Microwave oven with infrared detection element

Abstract

A heating chamber has a width in a direction of a two-head arrow X, a depth in a direction of a two-head arrow Y and a height in a direction of a two-head arrow Z. An infrared sensor includes 25 infrared detection elements each having a field of view. Since the 25 infrared detection elements are arranged, five by five in directions Y and Z, on the heating chamber's bottom plate there are projected a total of 25 fields of view, five by five in directions Y and X. Thus the bottom plate has any area thereof covered by one of the 25 fields of view.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to microwave ovens and particularly to microwave ovens having an infrared detection element and operative in response to an output from the infrared detection element to provide a heat-cooking operation.

2. Description of the Background Art

Japanese Patent Publication No. 4-68756 discloses a conventional microwave oven employing an infrared detection element to detect a temperature profile on the turntable to detect the position and temperature of a food to be heated that is placed on the turntable.

In such a conventional microwave oven, however, the infrared detection element can only detect the amount of infrared radiation in a limited area (or a field of view), i.e., on the turntable. As such, if such a microwave oven does not have a turntable and a food is placed in the oven's heating chamber at a location at which a turntable would otherwise be provided, the infrared detection element's output cannot fully be used to detect the temperature of the food in the heating chamber.

Furthermore, in a conventional microwave oven, with an infrared sensor arranged in a manner, the heating chamber often can have a large number of areas that cannot be covered by the field of view of the infrared detection element. If in such a case a food is placed at a location that the field of view cannot cover, the infrared sensor's output can also not fully used to detect the condition of the object to be heated.

Furthermore, if juice and the like scattering from a food in the heating chamber adheres to the component of the infrared detection element receiving infrared radiation, it can prevent the infrared detection element from accurately detecting the temperature of the object to be heated. In such a case, the infrared sensor's output can also not fully be used to detect the condition of the object to be heated.

SUMMARY OF THE INVENTION

The present invention has been made to overcome such disadvantages as above and it contemplates a microwave oven employing an infrared sensor having an infrared detection element mounted thereto to ensure that the temperature of an object to be heated is detected to make full use of an output of the infrared sensor to detect the condition of the object to be heated.

The present invention in one aspect provides a microwave oven having a heating chamber accommodating an object to be heated, includes a plurality of infrared detection elements having their respective fields of view in the heating chamber to detect an amount of infrared radiation in the fields of view, the plurality of infrared detection elements being arranged to have the fields of view covering an area in the heating chamber in a first direction from one end to the other end.

In the present invention in one aspect wherever in the heating chamber in the first direction there may exist the object to be heated the infrared detection elements are not required to be moved and their outputs can be used to detect the temperature of the object to be heated.

Thus the infrared detection elements' outputs can be made full use of to detect the condition of the object to be heated.

The present invention in another aspect provides a microwave oven having a heating chamber accommodating an object to be heated includes: an infrared detection element having a field of view in the heating chamber and attached to the heating chamber in a first direction on one side to detect an amount of infrared radiation in the field of view; and a drive unit driving the infrared detection element to move in a second direction traversing the first direction.

Thus if the infrared detection element is moved its field of view can have an area free of a significant variation in size in the heating chamber.

This can enhance the precision of the temperature of the object to be heated that is derived from an output of the infrared detection element.

The present invention in another aspect provides a microwave oven having a heating chamber accommodating an object to be heated, includes: an infrared detection element having a field of view in the heating chamber and attached to the heating chamber in a first direction on one side to detect an amount of infrared radiation in the field of view; and a drive unit driving the infrared detection element to pivot around an axis corresponding to a line orthogonal to a plane formed by the field of view and extending in one direction closest to one side.

With the drive unit driving the infrared detection element to pivot by a predetermined angle, the heating chamber in the first direction on one side and the other side can have less area that is not covered by the field of view of the infrared detection element. More specifically, the heating chamber can be entirely covered by the field of view of the infrared detection element that pivots by a further reduced angle.

Thus temperature can be detected throughout the heating chamber over a wide area.

The present invention in still another aspect provides a microwave oven having a heating chamber accommodating an object to be heated includes: an infrared detection element having a field of view in the heating chamber to detect an amount of infrared radiation in the field of view; a decision unit determining from an output received from the infrared detection element whether the field of view covers the object to be heated; and a drive unit driving the infrared detection element to move the field of view in the heating chamber, wherein if with the drive unit moving the field of view at a first rate the decision unit determines that in the heating chamber at an area there exists the object to be heated then the drive unit is controlled to move the field of view in the area at a second rate to determine that in the area at a specific subarea there exists the object to be heated, the second rate being lower than the first rate.

Thus in the heating chamber the object to be heated can soon be located.

Thus if the object in the heating chamber is heated for a short period of time its temperature can be detected accurately. That is, if the object in the heating chamber is heated for a short period of time the output of the infrared detection element can be made full use of.

The present invention in another aspect provides a microwave oven having a heating chamber having a wall provided with a window, and accommodating an object to be heated, includes: an infrared detection element provided external to the heating chamber and having a field of view in the heating chamber via the window to detect an amount of infrared radiation in the field of view; a cylinder surrounding the window and extending from the window outwardly of the heating chamber; and a drive unit driving the infrared detection element to move. The cylinder has a specific portion increased in height than a remaining portion of the cylinder. The infrared detection element has a detection window introducing infrared radiation into the infrared detection element. The drive unit drives the infrared detection element to move to allow the detection window to face the specific portion if the infrared detection element is not operated to detect infrared radiation.

Thus the cylinder can be formed by barring a sidewall of the heating chamber and at the specific portion of the cylinder increased in height than the remaining portion of the cylinder the infrared detection element can wait when it is not operated for detection.

As such when it is not operated for detection the infrared detection element can be free from contamination otherwise resulting in an impaired precision in detection. Thus the infrared detection element can provide an output that can more effectively be used to detect the temperature of the object to be heated. Furthermore, readily, without using any additional member and at low cost, and at a location closer to the position of the infrared detection element when it is operated for detection, there can be provided a location for the infrared detection element to wait at when it is not operated for detection.

The present invention in still another aspect provides a microwave oven having a heating unit, a fan provided to cool the heating unit, and a heating chamber having a wall provided with a window, and accommodating an object to be heated, includes: an infrared detection element provided external to the heating chamber and having a field of view in the heating chamber via the window to detect an amount of infrared radiation in the field of view; and a drive unit driving the infrared detection element to move windward of the window as the fan operates.

Thus without using any additional member and at low cost the infrared detection element when it is not operated for detection can be free of contamination otherwise resulting in an impaired precision in detection.

Thus the infrared detection element can provide an output that can more effectively be used to detect the temperature of the object to be heated.

The present invention in a different aspect provides a microwave oven having a chamber with a wall provided with a window, and accommodating an object to be heated, includes a plurality of infrared detection elements provided external to the heating chamber and having a field of view in the heating chamber via the window to detect an amount of infrared radiation in the field of view, the plurality of infrared detection elements having their respective fields of views with their respective centerlines traversing each other in a vicinity of the window.

Thus the heating chamber can have a window minimized in diameter.

This ensures that the infrared detection element can be free of an impaired precision in detection otherwise attributed for example to juice of the object to be heated in the heating chamber that scatters outside the heating chamber. Thus the infrared detection element can provide an output that can more effectively be used to detect the temperature of the object to be heated.

The present invention in a still different aspect provides a microwave oven having a heating unit, a heating chamber with a wall provided with a window, and accommodating an object to be heated, and a plurality of infrared detection elements provided external to the heating chamber and having a field of view in the heating chamber via the window to detect an amount of infrared radiation in the field of view, of the plurality of infrared detection elements a predetermined infrared detection element having a field of view having a portion external to the heating chamber, includes: a decision unit determining whether the object to be heated is covered by the field of view of the predetermined infrared detection element; and a unit stopping a heating operation of the heating unit if the decision unit determines that the object to be heated is covered by the field of view of the predetermined infrared detection element.

Thus in the microwave oven the infrared detection elements includes an infrared detection element having a field of view partially external to the heating chamber and thus incapable of accurately detecting the temperature of the object to be heated and if in the field of view of the infrared detection element there exists the object to be heated the microwave oven stops the current heating operation.

As such, wherever in the heating chamber the object to be heated may be placed, the infrared detection elements' outputs can be effectively used to control a heating operation, as appropriate.

The present invention in one aspect provides a method of controlling a microwave oven employing an infrared detection element having a field of view corresponding to a respective one of a plurality of areas internal to a heating chamber, to detect a temperature of an object attained in the field of view, including the steps of: calculating for each the area a variation in the temperature introduced within a predetermined temporal period; and referring only to the temperature in the area corresponding to the variation having a largest value and the temperature in the area corresponding to the variation having a value of at least a predetermined percentage relative to the variation having the largest value, to control a heating operation.

Thus of the fields of view of the plurality of infrared detection elements a field of view with a largest variation in temperature within a predetermined temporal period and a field of view with a variation having at least a predetermined percentage relative to the largest variation are extracted as specific fields of view and therein temperature is detected and used to control a heating operation.

Thus the outputs of the plurality of infrared detection elements can be used effectively.

The present in another aspect provides a method of controlling a microwave oven having a heating chamber with an infrared detection element attached thereto in a first direction on one side to detect a temperature of an object in the heating chamber, includes the step of controlling the infrared detection element to detect the temperature of the object in the heating chamber while moving the infrared detection element in a second direction traversing the first direction.

Thus if the infrared detection element is moved its field of view can have an area free of a significant variation in size in the heating chamber.

This can enhance the precision of the temperature of the object to be heated that is derived from an output of the infrared detection element.

The present invention in still another aspect provides a method of controlling a microwave oven having a heating chamber with an infrared detection element attached thereto in one direction on one side and having a field of view to detect a temperature of an object in the heating chamber, includes the step of controlling the infrared detection element to pivot around an axis corresponding to a line orthogonal to a plane formed by the field of view and extending in the first direction closest to one side, to detect the temperature of the object in the heating chamber.

With the drive unit driving the infrared detection element to pivot by a predetermined angle, the heating chamber in the first direction on one side and the other side can have less area that is not covered by the field of view of the infrared detection element. More specifically, the heating chamber can be entirely covered by the field of view of the infrared detection element that pivots by a further reduced angle.

Thus temperature can be detected throughout the heating chamber over a wide area.

The present invention in another aspect provides a method of controlling a microwave oven having a heating chamber with an infrared detection element having a field of view moving to allow the infrared detection element to detect a temperature of an object in the heating chamber, includes the steps of: referring to an output of the infrared detection element with the field of view moving at a first rate to determine that in the heating chamber at an area there exists the object to be heated; and referring to an output of the infrared detection element with the field of view moving in the area at a second rate to determine that in the area at a specific subarea there exists the object to be heated, the second rate being lower than the first rate.

Thus in the heating chamber the object to be heated can soon be located.

Thus if the object in the heating chamber is heated for a short period of time its temperature can be detected accurately. That is, if the object in the heating chamber is heated for a short period of time the output of the infrared detection element can be made full use of.

The present invention in still another aspect provides a method of controlling a microwave oven having a heating unit provided to heat an object to be heated, a fan provided to cool the heating unit, and an infrared detection element having a field of view in the heating chamber via a window provided in a wall of the heating chamber, the infrared detection element having the field of view moving to allow the infrared detection element to detect a temperature of an object in the heating chamber, includes the steps of: determining whether the infrared detection element is being operated to detect temperature; and if the infrared detection element is not being operated to detect temperature, moving the infrared detection element windward of the window as the fan operates.

Thus without using any additional member and at low cost the infrared detection element when it is not operated for detection can be free of contamination otherwise resulting in an impaired precision in detection.

Thus the infrared detection element can provide an output that can more effectively be used to detect the temperature of the object to be heated.

The present invention in a different aspect provides a method of controlling a microwave oven having a heating unit provided to heat an object to be heated and a plurality of infrared detection elements having their respective fields of view in a heating chamber, of the plurality of infrared detection elements a predetermined infrared detection element having a field of view partially external to the heating chamber, includes the steps of: determining whether the object to be heated is covered by the field of view of the predetermined infrared detection element; and stopping a heating operation if the object to be heated is covered by the field of view of the predetermined infrared detection element.

Thus in the microwave oven the infrared detection elements includes an infrared detection element having a field of view partially external to the heating chamber and thus incapable of accurately detecting the temperature of the object to be heated and if in the field of view of the infrared detection element there exists the object to be heated the microwave oven stops the current heating operation.

As such, wherever in the heating chamber the object to be heated may be placed, the infrared detection elements' outputs can be effectively used to control a heating operation, as appropriate.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of a microwave oven as one embodiment of the present invention;

FIG. 2 is a perspective view of the FIG. 1 microwave oven with its door open;

FIG. 3 is a perspective view of the FIG. 1 microwave oven with its exterior removed;

FIG. 4 is a cross section of the FIG. 1 microwave oven, taken along line IV—IV;

FIG. 5 is a cross section of the FIG. 1 microwave oven, taken along line V—V;

FIG. 6 schematically shows a field of view of an infrared detection element of the FIG. 1 microwave oven that is included in an infrared sensor thereof;

FIG. 7 is a block diagram of the control of the FIG. 1 microwave oven;

FIG. 8 is a flow chart of a heat-cooking process executed by a control circuit of the FIG. 1 microwave oven;

FIG. 9A shows a first variation of the FIG. 1 microwave oven and

FIG. 9B is a block diagram showing the control of the first variation of the FIG. 1 microwave oven;

FIG. 10 schematically shows the first variation of the FIG. 1 microwave oven with an infrared detection element having a field of view moving on the bottom plate;

FIG. 11 is a flow chart of a heat-cooking process executed by the control circuit in the first variation of the FIG. 1 microwave oven;

FIG. 12 shows the FIGS. 9A and 9B microwave oven with the infrared detection element having its field of view moving in a different direction;

FIG. 13 shows in the FIG. 10 microwave oven the infrared detection element's field of view moving in a different direction;

FIG. 14 shows a second variation of the FIG. 1 microwave oven;

FIG. 15 schematically shows the second variation of the FIG. 1 microwave oven, illustrating a positional relationship between the field of view of the infrared detection element and the bottom plate;

FIG. 16 is a flow chart of a heat-cooking process executed by a control circuit in the second variation of the FIG. 1 microwave oven;

FIG. 17 is a flow chart of a heat-cooking process executed by the control circuit in the second variation of the FIG. 1 microwave oven;

FIG. 18 shows a third variation of the FIG. 1 microwave oven;

FIG. 19 schematically shows the third variation of the FIG. 1 microwave oven, illustrating a positional relationship between the field of view of the infrared detection element and the bottom plate;

FIG. 20 is a flow chart of a heat-cooking process executed by a control circuit in the third variation of the FIG. 1 microwave oven;

FIG. 21 is a flow chart of a heat-cooking process executed by the control circuit in the third variation of the FIG. 1 microwave oven;

FIG. 22 is a vertical cross section of the microwave oven in a fourth variation of the present invention;

FIG. 23 is a side view in a vicinity of the FIG. 22 rotative antenna and subantenna;

FIG. 24 is an enlarged view below the FIG. 22 heating chamber;

FIG. 25 is an enlarged view below the FIG. 22 heating chamber;

FIG. 26 is an enlarged view below the FIG. 4 heating chamber;

FIG. 27 is a plan view of a subantenna of the FIG. 22 microwave oven;

FIG. 28 is a plan view of a rotative antenna of the FIG. 22 microwave oven;

FIG. 29A is a plan view of the FIG. 22 subantenna and rotative antenna overlapping each other, and

FIG. 29B is a partial cross section of the subantenna of FIG. 22 microwave oven;

FIG. 30 is a plan view of a subantenna of a fifth variation of the present invention;

FIG. 31 is a vertical, partial cross section of a microwave oven of the fifth variation of the present invention;

FIG. 32 is a cross section in a vicinity of an optical sensor of the FIG. 31 microwave oven;

FIG. 33 is a vertical cross section in a vicinity of a motor of the FIG. 31 microwave oven;

FIG. 34 is a bottom side view in a vicinity of a motor of a microwave oven of a sixth embodiment of the present invention;

FIG. 35 is a bottom side view in a vicinity of a motor of a microwave oven of a seventh variation of the present invention;

FIG. 36 is a plan view of a typical rotative antenna;

FIG. 37 schematically shows a bottom of a heating chamber;

FIG. 38 is a partial, perspective, right-side view of a microwave oven of a ninth variation of the present invention; with the exterior removed therefrom;

FIG. 39 is a right side view of the FIG. 38 detection path member;

FIG. 40 is a bottom side view of the FIG. 38 detection path member;

FIG. 41 is a perspective, right-side view of the FIG. 38 detection path member, as seen from behind;

FIG. 42 illustrates a positional relationship between the FIG. 38 detection path member and an infrared sensor;

FIG. 43 schematically shows a field of view of an infrared sensor provided in a heating chamber of the ninth variation of the present invention;

FIG. 44 is an enlarged view in a vicinity of the FIG. 43 infrared sensor;

FIG. 45 shows an infrared sensor pivoting as compared in the ninth variation of the present invention;

FIG. 46 is an enlarged view in a vicinity of the FIG. 45 infrared sensor;

FIG. 47 is a flow chart representing a controlling manner of a microwave oven in a tenth variation of the present invention;

FIG. 48 is a flow chart representing a controlling manner of a microwave oven in the tenth variation of the present invention;

FIG. 49 is a view for illustrating how a field of view moves in the microwave oven of an eleventh variation of the present invention;

FIG. 50 is an enlarged view in a vicinity of an infrared sensor of a microwave oven of a twelfth variation of the present invention;

FIG. 51 is a vertical cross section of the microwave oven of the twelfth variation of the present invention;

FIG. 52 shows an exemplary, specific configuration of an infrared sensor of the microwave oven of the twelfth variation of the present invention;

FIG. 53 shows another exemplary, specific configuration of the infrared sensor of the microwave oven of the twelfth variation of the present invention;

FIG. 54 is an enlarged view in a vicinity of an infrared sensor of a microwave oven of a thirteenth variation of the present invention;

FIG. 55 is a flow chart representing a controlling manner in the microwave oven of the thirteenth variation of the present invention;

FIG. 56 is a flow chart representing a controlling manner in the microwave oven of the thirteenth variation of the present invention;

FIG. 57 represents a direction in which moves an infrared sensor recommended in the present invention;

FIG. 58 represents a direction in which moves an infrared sensor recommended in the present invention;

FIG. 59 represents a direction in which moves an infrared sensor recommended in the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter the embodiments of the present invention will be described with reference to the drawings.

1. Structure of Microwave Oven

With reference to FIG. 1 , a microwave oven 1 is formed mainly of a body 2 and a door 3 . Body 2 has its outer surface covered by an exterior 4 . Body 2 has a front side provided with an operation panel 6 allowing a user to input various information to microwave oven 1 . Body 2 is supported on a plurality of legs 8 .

Door 3 can be opened and closed with its lower end serving as an axis. Door 3 has an upper portion provided with a handle 3 A.

Furthermore, with reference to FIG. 2 , body 2 is internally provided with a body frame 5 . Body frame 5 surrounds a heating chamber 10 . Heat chamber 10 has an upper right side portion provided with a hole 10 A. Hole 10 A connects with a detection path member 40 external to heating chamber 10 . Heating chamber 10 has a bottom provided with a bottom plate 9 .

Although not shown in FIG. 3 , on the right side of body frame 5 a magnetron 12 (see FIG. 4 ) and other various components are mounted adjacent to heating chamber 10 .

With reference to FIGS. 3-5 , detection path member 40 connected to hole 10 A has an opening connected to hole 10 A and it is provided in the form of a box. The form of the box corresponding to detection path member 40 has a bottom side with an infrared sensor 7 attached thereto and a detection window 11 formed therein. Through detection window 11 infrared sensor 7 senses infrared radiation in heating chamber 10 .

Inside exterior 4 magnetron 12 is provided adjacent to a lower right portion of heating chamber 10 . Furthermore, below heating chamber 10 a waveguide 19 is provided to connect magnetron 12 and a lower portion of body frame 5 together. Magnetron 12 supplies microwave to heating chamber 10 via waveguide 19 .

Furthermore, a rotative antenna 15 is provided between the bottom of body frame 5 and bottom plate 9 . Under waveguide 19 is provided an antenna motor 16 . Rotative antenna 15 and antenna motor 16 are connected by a spindle 15 A. When antenna motor 16 is driven, rotative antenna 15 rotates.

In heating chamber 10 on bottom plate 9 a food is placed. Magnetron 12 generates a microwave which is in turn transmitted via waveguide 19 , agitated by rotative antenna 15 and thus supplied to heating chamber 10 to heat the food on bottom plate 9 .

Furthermore, behind heating chamber 10 is provided a heater unit 130 housing a heater and a fan provided to efficiently transfer to heating chamber 10 the heat generated by the heater. Although not shown in the figure, a heater is also provided above heating chamber 10 to burn the surface of the food.

2. Field of View of Infrared Sensor

Infrared sensor 7 includes a plurality of infrared detection elements (infrared detection elements 7 A described hereinafter). Each infrared detection element has a field of view. Infrared sensor 7 can thus have a field of view considered the fields of view of the infrared detection elements that are combined together. FIGS. 4 and 5 schematically illustrate a field of view of infrared sensor 7 as a total field of view 700 .

Infrared sensor 7 has a field of view covering the entirety on bottom plate 9 . Thus, wherever in microwave oven 1 on bottom plate 9 a food may be placed, infrared sensor 7 is not required to move its field of view to cover the food.

As has been described above, infrared sensor 7 includes a plurality of infrared detection elements.

FIG. 6 schematically shows bottom plate 9 and infrared sensor 7 . Note that in FIG. 6 a two-head arrow X corresponds to the width of microwave oven 1 , a two-head arrow Y corresponds to the depth of microwave oven 1 , and a two-head arrow Z corresponds to the height of microwave oven 1 . Arrows X, Y and Z are orthogonal to each other.

Infrared sensor 7 includes a total of 25 infrared detection elements 7 A, five in direction Y and five in direction Z. Infrared detection elements 7 A each have a field of view 70 A.

25 infrared detection elements 7 A have their respective fields of view 7 A projected on bottom plate 9 , on which a total of 25 fields of view 70 A are projected, five in direction Y and five in direction X. Note that corresponding to five infrared detection elements 7 A arranged in direction Y, on bottom plate 9 five fields of view 70 A are arranged in direction Y. Furthermore, corresponding to five infrared detection elements 7 A arranged in direction Z, on bottom plate 9 there are five fields of view 70 A arranged in direction X.

Note that on bottom plate 9 in direction X a field of view 70 A projected that is closer to the right side has a smaller area, since as seen in direction X bottom plate 9 closer to the right side is closer to infrared detection element 7 A.

A single infrared detection element 7 A cannot have the field of view 70 A covering the entirety of bottom plate 9 . However, as shown in FIG. 6 , infrared sensor 7 having 25 infrared detection elements 7 A with the 25 fields of view 70 A combined together allows substantially the entirety of bottom plate 9 to be covered by the field of view 70 A. Note that the 25 fields of view 70 A combined together correspond to the total field of view 700 shown in FIG. 4 or 5 .

3. Control Block Diagram

With reference to FIG. 7 , microwave oven 1 includes a control circuit 30 generally controlling the operation of microwave oven 1 . Control circuit 30 includes a microcomputer.

Control circuit 30 receives various information via operation panel 6 and infrared sensor 7 . Control circuit 30 uses the received information and the like to control a motor for a cooling fan, an internal lamp 32 , a microwave oscillation circuit 33 and a heater 13 . Motor 31 drives a fan provided to cool magnetron 12 . Internal lamp 32 illuminates heating chamber 10 . Microwave oscillation circuit 33 allows magnetron 12 to oscillate a microwave. Heater 13 is a heater provided in heater unit 130 and a heater provided over heating chamber 10 .

Note that control circuit 30 receives an output of each infrared detection element 7 A, individually.

4. Automatic Cooking Process

Microwave oven 1 provides a heat-cooking process with infrared sensor 7 operating to sense the temperature of a food in heating chamber 10 to automatically terminate the heating operation. This process will now be described mainly by describing a process executed by control circuit 30 .

With reference to FIG. 8 , when operation panel 6 is operated to start a heat-cooking operation, control circuit 3 initially at step SA 1 controls magnetron 12 to start a heating operation and then moves to step SA 2 .

At step SA 2 , the FIG. 6 25 infrared detection elements 7 a provide their respective detection results which are in turn used to detect the temperature of the object in each field of view 70 A, and the control circuit then goes to step SA 3 . Note that the FIG. 6 25 infrared detection elements 7 A are labeled P( 1 )-P( 25 ), respectively, depending on their respective positions. Thus, at step SA 2 , P( 1 )-P( 25 ) provide their respective detection results, which are in turn stored as TO( 1 )-TO( 25 ).

At step SA 3 , control circuit 30 determines whether a predetermined period of time of T in seconds has elapsed since a heating operation started at step SA 1 . If so then the control circuit goes to step SA 4 .

At step SA 4 , control circuit 30 detects temperature based on the detection results from infrared detection elements 7 A labeled P( 1 )-P( 25 ) as above, and stores the values of temperature detected T( 1 )-T( 25 ), and the control circuit then goes to step SA 5 .

At step SA 5 , control circuit 30 calculates for each of P( 1 )-P( 25 ) the difference between value T(N) stored at step SA 4 immediately previously executed and TO(N) measured immediately after the heating operation is started, wherein N is 1 to 25, and the control circuit then goes to step SA 6 .

At step SA 6 , control circuit 30 extracts from 25 ΔT(N)s calculated at step SA 5 a maximal value (MAXΔT 1 ) and a second maximal value (MAXΔT 2 ) and the control circuit then goes to step SA 7 .

At step SA 7 , control circuit 30 extracts from the 23 ΔT(N)s remaining at step SA 6 a ΔT(N) satisfying the following expression (1), and the control circuit then goes to step SA 8 . In expression (1) MAXΔT 1 represents the maximal ΔT(N) extracted at step SA 6 and K represents a constant satisfying 0<K≦1. Microwave oven 1 provides heat-cooking processes according to a plurality of cooking menus. Constant K has a value varying to reflect a cooking menu to be provided.

Δ T ( N )≧MAXΔT1× K   (1)

Note that at step SA 7 , (K−2) ΔT(N)s satisfying expression (1) are extracted as MAXΔT 3 to MAXΔTk. More specifically, at steps SA 6 and SA 7 , from 25 ΔT(N)s the k largest ΔT(N)s, i.e., MAXΔT 1 to MAXΔTk are extracted.

At step SA 8 , control circuit 30 uses the following expression (2) to calculate AVEΔT and then goes to step SA 9 . $$ AVE ⁢   ⁢ Δ ⁢   ⁢ T = ∑ x = 1 k ⁢ ( MAX ⁢   ⁢ Δ ⁢   ⁢ Tx ) ⁢   k ( 2 )

As can be understood from expression (2), AVEΔT corresponds to an average of temperature differences of the k largest values, as measured since the heating operation was started.

At step SA 9 , control circuit 30 determines whether the following expression (3) is satisfied. In expression (3) TP represents a temperature set for an object to be heated and referred to to terminate a heating operation when infrared sensor 7 senses the set temperature as the object to be heated is considered as having been sufficiently heated. Set temperature TP has a value set for each individual cooking menu.

TO+AVEΔ≧TP   (3)

Then, if control circuit 30 at step SA 9 determines that expression (3) is not satisfied then the control circuit goes to step SA 10 .

At step SA 10 , control circuit 30 detects the current T (N) (a temperature based on an output of infrared detection element 7 ) at each of the k positions at which MAXΔT 1 to MAXΔTk are extracted at steps SA 6 and SA 7 . The control circuit then goes to step SA 11 .

At step SA 11 , control circuit 30 calculates MAXΔT 1 to MAXΔTk from the temperature detected at the step SA 10 immediately previously performed and TO detected at steps SA 2 and the control circuit then goes to step SA 8 . The SA 10 -SA 11 steps continue until at step SA 9 the control circuit determines that expression (3) is satisfied.

If at step SA 9 the control circuit determines that expression (3) is satisfied then at step SA 12 the control circuit controls magnetron 12 to terminate the heating operation and then returns.

In the above described heat-cooking process, as has been described as the SA 8 -SA 11 steps, whether an object to be heated has been completely heated is determined ultimately from the outputs of k of 25 infrared detection elements 7 A. As has been described in the SA 3 -SA 7 steps, the k outputs allow temperature elevation ΔT(N), as measured after a heating operation starts and before a predetermined period of time (t in seconds) has elapsed, to satisfy expression (1), which is that ΔT(N) has a value equal to or exceeding a maximal temperature elevation MAXΔT 1 multiplied by K.

In the present embodiment, control circuit 30 configures a temperature calculation unit using an output of each infrared detection element to calculate an “in field of view” temperature corresponding to a temperature of an object in a field of view of the infrared detection element, and a heating control unit referring to the “in field of view” temperature to control the heating unit.

Furthermore, at step SA 5 ΔT(N) is detected for each of 25 infrared detection elements 7 A, and it corresponds to a variation in “in field of view” temperature within a predetermined period of time.

Furthermore, at steps SA 6 and SA 7 MAXΔT 1 to MAXΔTk are extracted, and they correspond to specific variations in the predetermined period of time. Note that the specific variations within the predetermined period of time include a maximal variation within the predetermined period of time and a variation within the predetermined period of time which has a value having a predetermined percentage relative to the maximal variation within the predetermined period of time.

Furthermore at step SA 10 the fields of view 70 A of k infrared detection elements 7 A are subject to temperature detection, and they correspond to specific fields of view. Note that the specific field of view is one of the fields of views of the multiple infrared detection elements that corresponds to a specific variation within the predetermined period of time.

Then at the SA 8 -SA 11 steps control circuit 30 refers to the “in field of view” temperatures in the specific fields of view to control the heating unit.

In the present embodiment, as shown in FIG. 6 , infrared sensor 7 has 25 infrared detection elements 7 A arranged in a 5×5 matrix and having the fields of view 70 A each corresponding to a different area on bottom plate 9 to together cover substantially the entirety of bottom plate 9 . In other words, wherever on bottom plate 9 a food may placed, the food can be covered by at least one of the 25 fields of view 75 A.

Thus, in the present embodiment, wherever in the heating chamber an object to be heated may be placed, the plurality of infrared detection elements are not required to move their fields of view to cover at least a portion of the food placed in the heating chamber.

In the present embodiment an area having experienced a largest temperature variation since a heating operation started (i.e., an area in which MAXΔT 1 is detected) is considered as bearing a food thereon and thus has its temperature continuously detected until the heating operation ends(steps SA 8 -SA 11 ).

Furthermore, an area having experienced a second largest temperature variation since the heating operation started (i.e., an area in which MAXΔT 2 is detected) is also considered as bearing a food thereon and thus has its temperature continuously detected until the heating operation ends (steps SA 8 -SA 11 ).

Furthermore, if an area has a temperature variation relative to the largest temperature variation that is equal to or exceeds a predetermined percentage (K, see step SA 7 ), then the area also has its temperature continuously detected until the heating operation ends (steps SA 8 -SA 11 ).

Thus, if a plurality of objects to be heated are placed on bottom plate 9 , their temperatures can all be referred to to execute a heat-cooking process.

It should be noted, however, that while in the present embodiment the area with MAXΔT 2 detected has its temperature continuously detected until the heating operation ends, whether or not MAXΔT 2 is equal to or exceeds K times MAXΔT 1 , the present embodiment is not limited as above.

More specifically, while in the present embodiment at least two areas (those at which MAXΔT 1 and MAXΔT 2 are detected) have their respective temperatures continuously detected until the heating operation ends, only a single area may alternatively have its temperature continuously detected until the heating operation ends. In this example, step SA 6 is changed to extract only MAXΔT 1 and furthermore at step SA 7 are extracted (k−1) values, MAXΔT 2 to MAXΔTk.

If infrared sensor 7 includes a plurality of infrared detection elements 7 A, it is not a requirement that bottom plate 9 has substantially any area thereof covered by the field of view 70 A of infrared detection element 7 A, as shown in FIG. 6 .

Hereinafter, as a first variation of the present embodiment, infrared sensor 7 including a plurality of infrared detection elements 7 A arranged in a predetermined direction in a line will now be described by way of example.

5. First Variation

In FIG. 9A , infrared sensor 7 has infrared detection elements 7 A arranged in a line in the direction of the depth of heating chamber 10 , although not shown in the figure. In FIG. 9A , exterior 4 and door 3 are omitted and so is a portion of body frame 5 corresponding to a left-side wall of heating chamber 10 , to allow heating chamber 10 to have it interior readily visually observed. Furthermore, in FIG. 9A axes X, Y and Z are defined to correspond to the width, depth and height of heating chamber 10 , respectively. These three axes are orthogonal to each other.

In the present variation, microwave oven 1 includes infrared sensor 7 having six infrared detection elements 7 A arranged in direction Y and in addition to the FIGS. 1 and 7 microwave oven 1 a sensor motor 7 Z is provided to move a field of view of infrared detection element 7 A, (see FIG. 9 B).

With infrared sensor 7 having six infrared detection elements 7 A, on bottom plate 9 are simultaneously projected six fields of view 70 A arranged in direction Y, as represented by solid lines. Bottom plate 9 is covered by six fields of view 70 A in direction X at an area extending in direction Y from one end to the other end.

Furthermore microwave oven 1 is also provided with a member (sensor motor 7 Z) capable of moving infrared sensor 7 in the direction indicated by a two-head arrow 93 corresponding to a direction of rotation on the X-Z plane. Sensor motor 7 Z operates as controlled by control circuit 30 .

Since infrared sensor 7 moves in direction 93 , infrared detection element 7 A also positionally moves and the field of view 70 A projected on bottom plate 9 thus has a position moving in a direction indicated by a two-head arrow 91 (i.e., in direction X). More specifically, moving infrared sensor 7 in direction 93 allows the field of view 70 A to move from a position indicated by the solid line to a position indicated by the broken line.

Reference will now be made to FIGS. 10 and 11 to describe in the present variation how an output of each infrared detection element 7 A of infrared sensor 7 is used to provide a heat-cooking operation.

Note that the following description will be made generally for microwave oven 1 having infrared detection element 7 A arranged in the direction of the depth of heating chamber 10 and accordingly in FIG. 10 the number of infrared detection elements 7 A is not limited to any particular number and there exist N fields of view 70 A aligned in direction Y. Furthermore, in FIG. 10 , the field of view 70 A can take M positions as it moves in direction X. More specifically, if a coordinate system P (X, Y) is applied, then on bottom plate 9 the field of view 70 A has a position represented by P (1, 1) to P (M, N).

Furthermore in the present variation the plurality of infrared detection elements 7 A have their respective fields of views arranged to simultaneously cover bottom plate 9 in direction Y from one end to the other end. As such, the plurality of infrared detection elements 7 A have their fields of view in the coordinate system P (X, Y) with a coordinate X having a uniform value and a coordinate Y having N values ranging from one to N.

When operation panel 6 is used to provide a heat-cooking operation, control circuits 30 initially at S 1 controls magnetron 12 to start a heating operation.

Then at S 2 control circuit 30 moves infrared sensor 7 to allow infrared detection elements 7 A to have their fields of view 70 A having coordinate X equal to one. The position (X=1) corresponds to a rightmost area of bottom plate 9 . If infrared detection element 7 A have their fields of view 70 A having coordinate X equal to one, the fields of view 70 A, as shown in FIGS. 9 and 10 , correspond to the areas indicated by the solid lines and the plurality of infrared detection elements 7 A have their fields of view having coordinates P(1, 1) to P(1, N).

Then at S 3 control circuit 30 uses outputs of the infrared detection elements for the current positions of their fields of view 70 A to detect the temperature of an object in the fields of view 70 A, and stores detected temperatures TO(X, 1) to TO(X, N). TO(X, 1) to TO(X, N) each have value X substituted by the value of the current coordinate X of a respective one of the fields of view 70 A.

Then at S 4 control circuit 30 increments the value of coordinate X of each field of view 70 A by one to update it. This moves coordinate X of the field of view 70 A to the position of coordinate X resulting from the increment.

Then at S 5 control circuit 30 determines whether the value of coordinate X obtained at S 4 exceeds M. If not then the control circuit returns to S 3 and if so then the control circuit moves to S 6 . Thus the S 3 and S 4 steps continue until the field of view 70 A having coordinate X of one attains that of M. Thus bottom plate 9 has its entirety covered N×M fields of view 70 A.

At S 6 control circuit 30 determines whether a predetermined temporal period of T in seconds has elapsed since temperature was detected at S 3 for X=1, and if so then the control circuit moves to S 7 .

At S 7 control circuit 30 moves infrared sensor 7 to allow infrared detection element 7 A to each have a field of view 70 A with a coordinate X equal one.

At S 8 , the outputs from the infrared detection elements for the current positions of the fields of view 70 A are used to detect the temperature of an object in each field of view 70 A and detected temperatures T(X, 1) to T(X, N) are stored.

Then at S 9 control circuit 30 increments the value of coordinate X of each field of view 70 A by one to update it.

Then at S 10 control circuit 30 determines whether the value of coordinate X obtained at S 9 exceeds M. If not then the control circuit returns to S 8 and if so then the control circuit moves to S 11 . Thus the S 8 and S 9 steps continue until the fields of view 70 A having coordinate X of one attains coordinate X of N.

At S 11 control circuit 30 uses TO(1, 1) to TO(M, N) stored at S 3 and T(1, 1) to T(M, N) stored at S 8 to calculate ΔT(X, Y) for each coordinate and then move to S 12 . More specifically, at S 11 are calculated N×M ΔT(X, Y)s. Note that ΔT(X, Y) is calculated according to the following expression (4):

Δ T ( X, Y )= T ( X, Y )− TO ( X, Y )   (4)

wherein TO(X, Y) represents temperature at each coordinate (X, Y) detected immediately after the process is started, and T(X, Y) represents temperature at each coordinate (X, Y) detected when time T in seconds have elapsed since TO(X, Y) was detected. More specifically, ΔT(X, Y) represents a temperature elevation at each coordinate for time T in seconds.

At S 12 control circuit 30 extracts a maximal one of N×M ΔT(X, Y)s and stores it as MAXΔT(X, Y).

Then at S 13 control circuit 30 extracts any of N×M ΔT(X, Y)s calculated at S 11 that satisfy the following expression (5) and stores the same as TA(X, Y).

ΔT ( X, Y )≧ MAXΔT ( X, Y )× K   (5)

wherein K represents a constant satisfying 0<K≦1 and varies in value to reflect a cooking menu to be executed.

Hereinafter, the position of the field of view 70 A corresponding to ΔTA(X, Y) will be referred to as a “specific position.”

At S 14 , for specific positions extracted at S 13 corresponding to ΔTA(X, Y), control circuit 30 calls for temperature TO(X, Y) detected immediately after the heating operation is started that is stored at S 3 and control circuit 30 provides it as TAO(X, Y) and calculates an average thereof (AVETAO(X, Y)) and stores the average as TAO.

Then at S 15 control circuit 30 calculates an average AVEΔTA(X, Y) of ΔTA(X, Y)s extracted at S 13 and stores the average as ΔTA.

Then at S 16 control circuit 30 determines whether TAO calculated at S 14 plus ΔTA calculated at S 15 attains TP. If not then the control circuit moves to S 17 and if so then the control circuit goes to S 19 . TP represents a temperature set for an object to be heated, adopted to terminate a heating operation when the temperature is attained as the object to be heated is considered as having been sufficiently heated.

At S 19 control circuit 30 controls magnetron 12 to terminate the heating operation and the control circuit thus ends the heat-cooking process and returns.

In contrast at S 17 control circuit 30 detects temperature at a specific position (referred to as a coordinate PA(X, Y)) extracted at S 13 as TA(X, Y).

Then at S 18 control circuit 30 calculates for each specific position a difference ΔTA(X, Y) between temperature detected at the immediately previously executed S 17 and that detect at S 3 and then returns to S 15 .

In the present variation, temperature detection within the field of view 70 A is provided on bottom plate 9 at N×M areas labeled P (1, 1) to P (M, N). Note that the temperature detection at each of N×M areas is provided immediately after a heating operation is started (S 2 -S 5 ) and when a predetermined period of time has elapsed since the heating operation was started (S 7 -S 10 ).

Then, for each of N×M areas, temperature variation is calculated for a predetermined period of time (T in seconds) elapsing after the heating operation is started and it is provided as ΔT(1, 1) to ΔT(M, N) (S 11 ).

Then from ΔT(1, 1) to ΔT(M, N) is extracted ΔTA(X, Y) having a value having at least a predetermined percentage of K relative to maximum value MAXΔT(X, Y) (S 12 , S 13 ). Note that MAXΔT(X, Y) is a maximal value of ΔT(1, 1) to Δ(M, N) and ΔTA(X, Y) includes MAXΔT(X, Y). Furthermore, of N×M areas on bottom plate 9 , an area corresponding to extracted ΔTA(X, Y) is referred to as a “specific position” for the sake of convenience.

In the present variation in the process following the above described process a specific one(s) of N×M areas is/are subject to temperature detection.

More specifically, TAO is calculated as an average of temperatures TAO(X, Y)s for specific positions that are measured when a heating operation is started (S 14 ). Furthermore, ΔTA is calculated as an average of temperature elevations ΔTA(X, Y)s at the specific positions. Whether TAO plus ΔTA exceeds set temperature TP is referred to to determine whether the heating operation should be terminated (S 16 ).

Note that the specific positions are solely subjected to temperature detection until TAO plus ΔTA exceeds set temperature TP (S 17 , S 18 , S 15 ).

More specifically, in the present variation, an area having experienced a largest temperature variation since a heating operation was started is considered as bearing a food thereon and its temperature is continuously detected until the heating operation ends. Furthermore, if an area has a temperature variation having at least a predetermined percentage (K, see S 13 ) relative to the largest temperature variation the area also have its temperature continuously detected until the heating operation ends.

In the present variation, the area with the largest temperature variation and that with the temperature variation of at least a predetermined percentage relative to the largest temperature variation, are generally referred to as a “specific area.”

Thus, if a plurality of objects to be heated are placed on bottom plate 9 their temperatures can all be referred to to execute a heat-cooking process.

As has been described above, in the present variation the plurality of infrared detection elements 7 A has their fields of view 70 A combined together to cover bottom plate 9 in direction X (the direction of the width of heating chamber 10 ) in an area in direction Y (the direction of the depth of heating chamber 10 ) from one end to the other end. Furthermore, in the present variation, as has been described with reference to FIGS. 9 and 10 , the field of view 70 A moves in direction X.

Note that in microwave oven 1 , as shown in FIGS. 12 and 13 , infrared detection elements 7 A may be provided to allow fields of view 70 A to together cover bottom plate 9 in X direction from one end to the other end and also move in direction Y. More specifically, with reference to FIGS. 12 and 13 , in heating chamber 10 the plurality of fields of view 70 A moves in the direction of a two-head arrows 99 , i.e., direction Y. Thus, if a field of view has a position represented in an X-Y coordinate system by P(X, Y), fields of view located at P(1, N) to P(M, N) moves to change their coordinates Ys.

Furthermore, the plurality of infrared detection elements 7 A may not be provided to allow the fields of view 70 A to cover bottom plate 9 in direction Y or X from one end to the other end. Hereinafter a description will be made of a microwave oven of a second variation, including a plurality of infrared detection elements 7 A having their fields of view 70 A smaller in size than bottom plate 9 in both directions X and Y when the fields of view are combined together.

6. Second Variation

In FIG. 14 , infrared sensor 7 includes five infrared detection elements 7 A arranged in a line in the direction of the depth of heating chamber 10 , although not shown in the figure. As well as FIG. 9 , FIG. 14 omits various components of microwave oven 1 to allow heating chamber 10 to have its interior readily, visually observed. Furthermore, in FIG. 14 , heating chamber 10 has its width, depth and height defined to correspond to three axes X, Y and Z orthogonal to each other. Note that FIG. 14 shows in heating chamber 10 axes X and Y in the form of broken lines X and Y, traversing each other at the center of turntable 90 . An arrow 92 indicates a direction in which turntable 90 rotates.

In the present variation, microwave oven 1 includes heating chamber 10 having a bottom side provided with a round turntable 90 . As such, microwave oven 1 is preferably configured to have magnetron 12 supplying heating chamber 10 with microwave at a side surface of heating chamber 10 . Accordingly, waveguide 19 and rotative antenna 15 are preferably attached to the side surface of heating chamber 10 .

In the present variation five infrared detection elements 7 A are arranged to have their fields of view 70 A aligned in direction Y. Five fields of view 70 A projected on turntable 90 that are combined together are successively projected from the center of turntable 90 to a periphery thereof. As such, when turntable 90 turns, turntable 90 has its entire area covered by five fields of view 70 A.

Reference will now be made to FIGS. 15 to 17 to describe in the present variation how an output of each infrared detection element 7 A of infrared sensor 7 is used to provide a heat-cooking process.

Note that in the following description, with reference to FIG. 15 , the number of infrared detection elements 7 A is not limited to any particular number to generally describe microwave oven 1 including infrared detection elements 7 A arranged in the direction of the depth of heating chamber 10 , and there thus exist N fields of view 70 A arranged in direction Y. Thus on turntable 90 the field of view 70 A can have a position, if represented by P(N), of P(1) to P(N). Note that P(1) corresponds to the center of turntable 90 and as the number in the parenthesis increases the position represented by P(N) approaches a periphery of turntable 90 , and P(N) corresponds to an outermost peripheral position of turntable 90 .

When operation panel 6 is operated to provide a heat-cooking process, control circuit 30 initially at S 20 controls magnetron 12 to start a heating operation and the control circuit then goes to S 21 .

At S 21 control circuit 30 detects a temperature based on an output of each infrared detection element 70 A having its fields of view 70 A at a respective one of positions P(1) to P(N). Control circuit 30 associates the temperatures detected at S 21 with position P(1) to P(N), respectively, and stores them as T(1) to T (N). Furthermore, control circuit 30 also stores as TW a detected temperature T(N) corresponding to position P(N), at which the temperature is detected.

Then at S 22 control circuit 30 determines whether TW minus K (° C.) is greater than TP. If so then the control circuit goes to S 23 and if not then control circuit 30 goes to S 40 .

At S 40 control circuit 30 determines whether TW plus K (° C.) is smaller than TP. If so then the control circuit goes to S 41 and if not then the control circuit goes to S 30 .

TP is a temperature set for an object to be heated, adapted to terminate a heating operation when the temperature is attained as the object to be heated is considered as having being sufficiently heated. K represents a constant of approximately five. That is, K° C. is approximately 5° C. If microwave oven 1 provides a heat-cooking process to reflect multiple cooking menus, K is set for each of the menus.

In the heat-cooking process of the present variation the process steps following S 23 can be divided into three main blocks S 23 -S 29 , S 30 -S 38 , and S 41 -S 46 . Which block control circuit 30 is to execute depends on the magnitude of TW at the S 22 and S 40 decisions. Table 1 shows a relationship between TW and the blocks executed by control circuit 30 .

	TABLE 1
			TP − K >
	TP + K < TW	TP − K ≦ TW ≦ TP + K	TW (TP >
	(TP < TW − K)	(TW − K ≦ TP ≦ TW + K)	TW + K)
Steps	S23-S29	S30-S38	S41-S46
to be
Executed

The S 23 -S 29 steps will initially be described.

At S 23 control circuit 30 sets a value of “1” on axis Y for a location at which is detected a temperature to be extracted at 24 to be subject to a decision. More specifically, at S 23 control circuit 30 provides a setting to allow T(1) to be subject to a decision at S 24 .

Then at S 24 control circuit 30 extracts a detected temperature T(Y) currently set to be subject to a decision and determines whether the temperature is lower than set temperature TP. If so then the control circuit goes to S 25 and if not then the control circuit goes to S 27 . Note that a detected temperature subject to a decision at S 24 is that obtained from those obtained at the immediately previously executed S 21 or S 29 step which is detected at a location set at the immediately previously executed S 23 or S 26 step.

At S 25 control circuit 30 determines whether a position on axis Y currently set to be extracted as a subject for decision is no more than N−1. If so then the control circuit goes to S 26 . If not, i.e., if it has attained N then the control circuit goes to S 28 .

At S 26 the control circuit increments the currently set location by one on axis Y to update it and the control circuit then returns to S 24 . More specifically, the control circuit continues to make the S 24 decision until a position having a value “1” on axis Y attains a value of “N” on the axis.

At S 28 control circuit 30 determines whether a predetermined period of time A in seconds has elapsed since T 1 -T N were detected at the immediate previous S 29 or S 21 , and if so then the control circuit goes to S 29 . At S 29 , temperature is detected at each of locations P(1) to P(N−1) and stored as new values T(1) to T(N−1) and the control circuit then goes to S 23 . Herein, temporal period A in seconds is a period for detecting T(1) to T(N−1). Note that if turntable 90 turns at a rate of B (bpm), time A in seconds and the rate of revolution preferably have a relationship represented by the following equation (6);

A=B/I   (6)

wherein I is an integer.

If expression (6) is established, T(1) to T(N−1) is detected I times whenever turntable 90 rotates once. More specifically, temperature is detected on turntable 90 at a position of a radius forming an angle of 360 / I to each other.

If at S 24 the control circuit determines that TY has attained TP then control circuit 30 at S 27 determines whether TY is smaller than TW. If the control circuit determines that TY is no less than TW then the control circuit returns to S 25 . If the control circuit determines that TY is smaller than TW then the control circuit at S 39 controls magnetron 12 to terminate the current heating operation and the control circuit returns.

In the above-described S 23 -S 29 process, whenever time A in seconds elapses temperature is detected at locations P(1) to P(N−1) and stored as T(1) to T(N−1). If any of T(1) to T(N−1) has attained set temperature TP then the control circuit goes through S 27 and terminates the current heating operation. Note that in this example T(N) is temperature detected at S 21 .

The S 30 -S 38 process will now be described.

At S 30 control circuit 30 sets a value of “1” on axis Y for a location of at which is detected a temperature subject to a decision to be made at S 31 to be subsequently executed.

Then at S 31 control circuit 30 extracts detected temperature (TY) currently set to be subject to a decision and control circuit 30 determines whether the temperature is lower than set temperature TP minus K, i.e., TW−K. If so then the control circuit goes to S 32 and if not then the control circuit goes to S 34 . Note that detected temperature TY subject to a decision at S 31 is that obtained from those obtained at the immediately previously executed S 21 or S 38 step. TW is T(N) detected at S 21 which is detected at a location set at the immediately previously executed S 30 or S 33 step.

At S 32 control circuit 30 determines whether a location on axis Y that is currently set to be extracted as a subject for a decision is no more than N−1. If so then the control circuit 30 goes to S 33 . If not then the control circuit goes to S 37 .

At S 33 control circuit 30 increments the currently set location by one on axis Y to update it and the control circuit then goes back to S 31 . More specifically, the control circuit continues to make the S 31 decision until a location having a value “1” on axis Y attains a value of “N” on the axis.

At S 37 the control circuit determines whether a predetermined period of time A in seconds has elapsed since T(1) to T(N) were detected at the immediate previous S 38 or S 21 and if so then the control circuit goes to S 38 . At S 38 temperature is detected at each of location P(1) to P(N−1) and stored new T(1) to T(N−1) and the control circuit goes back to S 33 . Herein, time A in seconds is similar to that as has been described in the S 28 step, i.e., a period for detecting T(1) to T(N−1).

At S 31 if control circuit 30 determines that TY has attained TW−K then control circuit 30 goes to S 24 and determines whether TY is lower than TW. If TY is no less than TW then the control circuit goes back to S 32 and if TY is lower than TW then the control circuit goes to S 35 .

At S 35 control circuit 30 determines whether TP is lower than TW and if so then control circuit 30 at S 39 controls magnetron 12 to terminate the current heating operation and the control circuit returns.

If at S 35 it determines that TP is no less than TW then control circuit 30 at S 36 controls magnetron 12 to provide a further heating operation from that time point for an additional temporal period corresponding to value K in the process of interest and the control circuit at S 39 terminates the heating operation and returns. Note that, as has been described above, K is a value previously determined to correspond to a cooking menu. Thus at S 36 a heating operation is additionally executed for a period of time corresponding to a cooking menu.

The S 41 -S 46 process steps will now be described.

At S 41 control circuit 30 sets a value of “1” on axis Y for a location at which is detected a temperature to be extracted to be subject to the subsequent S 42 decision.

Then at S 42 control circuit 30 extracts detected temperature (TY) currently set to be subject to a decision and the control circuit determines whether the temperature is lower than set temperature TP. If so then the control circuit goes to S 43 and if not then the control circuit at S 39 terminates the heating operation and returns.

Note that a detected temperature subject to the S 42 decision is that obtained from those obtained at the immediately previously executed S 21 or S 46 step which is obtained at a location set at the immediately previously executed S 41 or S 44 step.

At S 43 control circuit 30 determines whether a location on axis Y that is currently set to be extracted as a subject for a decision is no more than N−1. If so then the control circuit goes to S 44 . If not then the control circuit goes to S 45 .

At S 44 control circuit 30 increments the currently set position by one on axis Y to update it and then goes back to S 42 . More specifically, the control circuit continues to make the S 42 decision until a position having a value “1” on axis Y attains a value of “N” on the axis.

At S 45 the control circuit determines whether a predetermined period of time A in seconds has elapsed since T(1) to T(N) were immediately previously detected at S 46 or S 21 . If so then the control circuit goes to S 46 . At S 46 , temperature is detected for each of locations P(1) to P(N−1) and stored as new T(1) to T(N−1) and then goes back to S 41 . Herein, as has been described in the S 28 step, time A in seconds is a period for detecting T(1) to T(N−1).

Thus in the present variation a heat-cooking process provides different blocks of steps to reflect value TW, as provided on Table 1. Note that in any of the blocks, temperature is detected whenever time A in seconds elapses. Time A in seconds, a period for temperature detection, and revolution rate B (bpm) are preferably have a relationship as represented by expression (6) provided above.

Note that in the present variation the S 29 and S 28 temperature detection are performed for locations P(1) to P(N−1) and it is omitted for location P(N), since on turntable 90 it is less likely that a food is placed at location P(N). Thus, temperature detection is omitted for location P(N) to maximally reduce the time required for a cooking process.

In the present variation microwave oven 1 includes infrared detection elements 7 A having the fields of view 70 A that cannot cover the entire bottom side of heating chamber 10 at a time even if all of the fields of view are combined together. However, the heating chamber 10 bottom side has turntable 90 , which turns to allow substantially any area on turntable 90 to be covered by one of the fields of view 70 A of the multiple infrared detection elements 7 A.

As a further variation of microwave oven 1 , a description will now be made of a microwave oven including heating chamber 10 having a bottom side provided with a turntable and having its area substantially entirely covered by the fields of view 70 A of multiple infrared detection elements 7 A at a time such that the chamber's bottom side has any portion thereof covered by one of the fields of view 70 A of multiple infrared detection elements 7 A.

7. Third Variation

In FIG. 18 , infrared sensor 7 includes infrared detection elements 7 A arranged in a M×N matrix in the directions of the depth and height of heating chamber 10 , although not shown in the figure. In FIG. 18 , as well as FIG. 9 , microwave oven 1 is shown with various components omitted to allow heating chamber 10 to have its interior readily visually observed. In FIG. 18 , heating chamber 10 has its width, depth and height defined to correspond to three axes X, Y and Z orthogonal to each other.

In the present variation, microwave oven 1 has heating chamber 10 having a bottom side provided with a round turntable 90 . Accordingly, microwave oven 1 preferably has magnetron 12 supplying heating chamber 10 with microwave at a side wall of heating chamber 10 and also has waveguide 19 and rotative antenna 5 attached to the side wall of heating chamber 10 .

In the present variation there exist M infrared detection elements 7 A in direction Y and N infrared detection elements 7 A in direction Z. Accordingly, on the heating chamber 10 bottom side are projected M fields of view 70 A (six of them in FIG. 18 by way of example) in direction Y and N fields of view 70 A in direction X. Some of M×N fields of view 70 A are projected on turntable 90 and the other thereof are projected outside turntable 90 . Note that turntable 90 has any portion thereof covered by one of M×N fields of view 70 A.

Reference will now be made to FIGS. 19-21 to describe how in the present variation an output of each of M×N infrared detection elements 7 A of infrared sensor 7 is used to provide a heat-cooking operation.

Note in the following description that if the field of view 70 A has a position represented in the form of “P(X, Y)” then it can have a position represented by P(1, 1) to P(N, M). Note that P(1, 1) represents a deepest, rightmost position in heating chamber 10 (an upper right corner in FIG. 19 ), and P(N, M) corresponds to a front, leftmost corner in heating chamber 10 (a lower left corner in FIG. 19 ). Furthermore, in heating chamber 10 the field of view 70 A closer to the left side as seen in direction X has a larger coordinate X and that closer to the front side (the lower side in FIG. 19 ) as seen in direction Y has a larger coordinate Y.

When operation panel 6 is operated to provide a heat-cooking operation, control circuit 30 initially at S 49 controls magnetron 12 to start a heating operation.

Then at S 50 control circuit 30 detects temperature based on outputs of infrared detection elements 70 A having their respective fields of view 70 A at positions P(1, 1) to P(N, M), respectively. Note that control circuit 30 associates M×N temperatures detected at S 50 with positions P(1, 1) to P(N, M), respectively, and stores them as T(1, 1) to T(N, M). Furthermore, control circuit 30 also stores as TW a detected temperature T(1, 1) corresponding to position P(1, 1).

Then at S 51 control circuit 30 determines whether TW minus K (° C.) is greater than TP and if so then the control circuit goes to S 53 and if not then the control circuit goes to S 52 .

At S 52 control circuit 30 determines whether TW plus K (° C.) is smaller than TP and if so then the control circuit goes to S 68 and if not then the control circuit goes to S 60 .

TP is a temperature set for an object to be heated, adapted to terminate a heating operation when the temperature is attained as the object to be heated is considered as having been sufficiently heated. K is a constant of approximately five. That is, K° C. is approximately 5° C. If microwave oven 1 provides a heat-cooking operation to accommodate various cooking menus K is set for each cooking menu.

In the present variation the heat-cooking process follows the process steps following S 53 that are divided generally into three blocks S 53 -S 59 , S 60 -S 66 , and S 68 -S 73 . Which block of steps control circuits 30 is to execute depends on the magnitude of TW at the S 51 and S 52 decisions. Table 2 represents a relationship between TW and the blocks executed by control circuit 30 .

	TABLE 2
			TP − K >
	TP + K < TW	TP − K ≦ TW ≦ TP + K	TW (TP >
	(TP < TW − K)	(TW − K ≦ TP ≦ TW + K)	TW + K)
Steps	S53-S59	S60-S66	S68-S73
to be
Executed

The S 53 -S 59 steps will initially be described.

At S 53 control circuit 30 extracts any of T(X, Y), or T(1, 1) to T(N, M), detected at the immediately previously executed S 50 or S 59 step that is lower than TW plus K (° C.) and the control circuit provides it as TE(X, Y) and then goes to S 54 .

At S 54 control circuit 30 extracts a maximal one of TE(X, Y)s extracted at S 53 and stores it as MAXTE.

Then at S 55 control circuit 30 extracts any of TE(X, Y)s that has a temperature no less than the product of MAXTE and a constant D and stores it has TED(X, Y). Note that D represents a constant previously determined for each cooking menu and satisfying 0>D>1.

Then at S 56 control circuit 30 calculates an average of TED(X, Y)s extracted at S 55 and stores it as AVETED(X, Y).

Then at S 57 control circuit 30 determines whether AVETED(X, Y) calculated at S 56 is lower than TP and if so then the control circuit goes to S 58 and if not then the control circuit at S 67 controls magnetron 12 to terminate the heating operation and returns.

At S 58 control circuit 30 determines whether time A in seconds has elapsed since T(X, Y) was detected at the immediately previously executed S 59 or S 50 step and if so then the control circuit goes to S 59 . At S 59 , temperature is detected for each of positions P(1, 1) to P(N, M) and stored as new T(1, 1) to T(N, M) and then the control circuit returns to S 53 . Herein, time A in seconds correspond to a period for detecting T(1, 1) to T(N, M). Note that if turntable 90 has a revolution rate of B (bpm), time A in seconds and the revolution rate preferably have a relationship represented by the following expression (7):

A=B/I   (7)

wherein I is an integer.

If expression (7) is established, T(1, 1) to T(N, M) is detected I times whenever turntable 9 turns once. More specifically, temperature is detected on turntable 90 at a location of a radius forming an angle of 360 / I to each other.

The S 60 -S 66 steps will now be described.

At S 60 control circuit 30 extracts any of T(X, Y), or T (1, 1) to T(N, M), detected at the immediately previously executed S 50 or S 64 step that is no less than TW minus K (° C.) and the control circuit provides it as TF(X, Y).

Then at S 61 control circuit 30 extracts any of TE(X, Y) extracted at S 60 that is lower than TW and the control circuit stores it as TFT(X, Y).

Then at S 62 control circuit 30 determines whether there is no TFT(X, Y) extracted at S 61 and if so then the control circuit goes to S 63 and if not then the control circuit goes to S 65 .

At S 63 control circuit 30 determines whether a predetermined temporal period A in seconds has elapsed since T(X, Y) was detected at the immediately previously executed S 64 or S 50 step and if so then the control circuit goes to S 64 . At S 64 temperature is detected for each of positions P(1, 1) to P(N, M) and stored as new T(1, 1) to T(N, M) and the control circuit then goes back to S 60 . Herein, time A in seconds correspond to a period for detecting T(1, 1) to T(N, M), as has been described in the S 58 step.

At S 65 control circuit 30 determines whether TP is lower than TW and if so then the control circuit at S 67 controls magnetron 12 to terminate the heating operation and then returns.

In contrast, if control circuit 30 at S 65 determines that TP is greater than TW then control circuit 30 at S 66 controls magnetron 12 to provide an additional heating operation from that time for an additional temporal period corresponding to value D in the process of interest and the control circuit then at S 39 terminates the heating operation and returns. Note that, as has been described above, D represents a value previously determined to correspond to a cooking menu. Thus at S 66 an additional heating operation is executed for a temporal period corresponding to a cooking menu.

The S 68 -S 73 steps will now be described.

At S 68 control circuit 30 extracts a maximal one of T(X, Y), or T(1, 1) to T(N, M), detected at the immediately previously executed S 50 or S 59 step and provides it as MAXT.

Then at S 69 control circuit 30 extracts any of T (X, Y)s detected at the immediately previously executed S 50 or S 69 that has a value exceeding the product of MAXT and constant D, and control circuit 30 stores it as TD(X, Y). Note that D represents a constant previously determined for each cooking menu, as has been described in S 55 .

Then at S 70 control circuit 30 calculates an average of TD(X, Y)s extracted at S 69 and stores it as AVETD(X, Y).

Then at S 71 control circuit 30 determines whether AVETD(X, Y) calculated at S 70 is higher than TP and if so the control circuit goes to S 72 and if not then the control circuit at S 67 controls magnetron 12 to terminate the heating operation and the control circuit returns.

At S 72 the control circuit determines whether a predetermined temporal period A in seconds has elapsed since T(X, Y) was detected at the immediately previously executed S 73 or S 50 step and if so then the control circuit goes to S 73 . At S 73 , temperature is detected for each of positions P(1, 1) to P(N, M) and stored as new T(1, 1) to T(N, M) and the control circuit then returns to S 68 . Time A in seconds is a period for detecting T(1, 1) to T(N, M).

In the present variation, a heat-cooking process provides different blocks of steps to reflect value TW, as has been provided in Table 2. Note that in any block, temperature is detected whenever time A in seconds elapses. The temperature detection period of A in seconds and revolution rate B (bpm) preferably have a relationship as represented by equation (7) provided above.

8. Fourth Variation

FIG. 22 is a partial cross section of a microwave oven corresponding to FIG. 4 .

With reference to FIG. 22 , the present variation provides a microwave oven having heating chamber 10 overlying a rotative antenna 20 rather than rotative antenna 15 .

Furthermore, a subantenna 21 is attached to rotative antenna 20 . Furthermore, with reference to FIG. 23 , rotative antenna 20 and subantenna 21 are each provided in the form of a plate. Subantenna 21 is attached to rotative antenna 20 by an insulator 61 , 62 . That is, rotative antenna 20 and subantenna 21 are insulated from each other. Note that rotative antenna 21 is attached to spindle 15 A. at the top end

Below rotative antenna 20 is attached a switch 89 switched on once whenever spindle 15 A revolves once. The revolution of spindle 15 A is transferred to switch 89 via a well known mechanism provided in a box 88 .

In FIGS. 24 and 25 , a thin arrow and a white arrow each represent a microwave radiation pattern and a thick, two-head arrow represents a pattern in which an electrical field is generated. In the microwave oven of the present variation, a microwave guided from magnetron 12 via waveguide 19 is transmitted through rotative antenna 20 and radiated therefrom at a perimeter (as indicated in FIGS. 24 and 25 by thin arrows) and also transmitted between a periphery of rotative antenna 20 and a bottom side of body frame 5 and between subantenna 21 and a bottom side of body frame 5 (as indicated in FIGS. 24 and 25 by thick, two-head arrows) and thus radiated in a vicinity of a periphery of subantenna 21 (as indicated in FIGS. 24 and 25 by white arrows).

To efficiently radiate a microwave from a periphery of rotative antenna 20 , the distance from the top end of spindle 15 A to the peripheral edge of rotative antenna 20 is preferably set to be one half of the wavelength of the microwave or that plus the wavelength of the microwave that is multiplied by an integer, since rotative antenna 20 thus dimensioned can peripherally have an electrical field having an intensity of a maximal value or a value closer thereto.

When a microwave spreads in rotative antenna 20 a transmission loss is introduced, whereas when it is transmitted between subantenna 21 and a bottom side of body frame 5 such a transmission loss is hardly introduced. As such, subantenna 21 can be formed to correspond to the geometry of hating chamber 10 receiving microwave radiation.

Subantenna 21 is provided with a plurality of holes, as will be described hereinafter, and FIG. 25 shows that an electronic wave propagates through a hole of subantenna 21 . An electronic wave transmitted from waveguide 19 is in turn transmitted via spindle 15 A to the center of rotative antenna 20 and therefrom toward an edge of rotative antenna 20 . Some of the electronic wave transmitted to the edge of rotative antenna 20 is supplied directly into heating chamber 10 and the other thereof is transmitted to subantenna 21 . Some of the electronic wave transmitted to subantenna 21 is supplied from an edge of subantenna 21 to heating chamber 10 and the other thereof is supplied from an edge of a hole 8 (holes 21 A to 21 F described hereinafter) to heating chamber 10 .

As can be understood from FIG. 29 , in the present variation rotative antenna 20 is generally covered by subantenna 21 . More specifically, subantenna 21 has a periphery outer than rotative antenna 20 , Thus, subantenna 21 exists closer to heating chamber 10 than rotative antenna 21 and, as seen in a plane parallel to that opposite to heating chamber 10 , has a large geometrical dimension and also exists over a large area. This can supply heating chamber 10 with a microwave over an area larger than when there is only rotative antenna 20 . Reference will now be made to FIG. 26 to describe further in detail an effect of providing such a subantenna 21 .

If under heating chamber 10 subantenna 21 is not provided and rotative antenna 15 is only provided then rotative antenna 15 has a periphery radiating a microwave toward heating chamber 10 only in a vicinity of the center.

In contrast, if rotative antenna 20 and subantenna 21 are both provided, as shown in FIGS. 24 and 25 , then not only does rotative antenna 20 have a periphery radiating a microwave toward heating chamber 10 in a vicinity of the bottom center but subantenna 21 also has a periphery radiating a microwave toward heating chamber 10 in a vicinity of the corner.

With reference to FIGS. 27-29A , subantenna 21 is provided with a plurality of holes including holes 21 A to 21 F. Thus subantenna 21 having received an electronic wave from rotative antenna 20 can radiate a microwave not only from an outer peripheral edge but from the holes.

Since subantenna 21 is fixed to rotative antenna 20 , it can revolve in the same period as rotative antenna 20 . As such, subantenna 21 can supply heating chamber 10 with a microwave in a pattern that varies as subantenna 21 rotates. More specifically, rotating subantenna 21 allows heating chamber 10 to be supplied with a microwave in a more complicated pattern, i.e., uniformly.

Rotative antenna 20 , as shown in FIG. 28 , has a center provided with a hole 20 X to be connected to spindle 15 A. Furthermore, rotative antenna 20 also has portions 20 A to 20 C extending from hole 20 X radially. In a vicinity of hole 20 X, rotative antenna 20 has an accurate periphery. Portion 20 A has an end spaced from hole 20 X by a distance A of approximately 60 mm and portions 20 B and 20 C each have an end spaced from hole 20 X by a distance D of approximately 80 mm. Distance A corresponds to approximately one half in length of the wavelength of a microwave.

An end of rotative antenna 20 radiates a microwave having an intensity depending on that of an electrical field generated at the edge. The intensity of the electrical field depends on the distance from a magnetron antenna of magnetron 12 to spindle 15 A, the distance from an end of spindle 15 A to a peripheral edge of rotative antenna 20 , the relationship between the length and geometry of waveguide 19 and the wavelength of a microwave radiated, and the like. For rotative antenna 20 of the present variation, the portion 20 a edge radiates a microwave more intense than the portions 20 B and 20 C edges. In other words, a waveguide is typically designed to intensify an electrical field generated in a vicinity of a power feed port of the waveguide, i.e., in a vicinity of spindle 15 A. As such, if the length from a vertex of spindle 15 A to an edge of rotative antenna 20 is dimensioned close to one fourth of the wavelength of a microwave that is multiplied by an even number, then the edge has a more intense electrical field. If the length is dimensioned closer to one fourth of the wavelength of a microwave that is multiplied by an odd number, then the edge has a weak electrical field.

In the present variation, subantenna 21 in a vicinity of portion 20 A has holes 21 A- 21 E in the form of a slit having its longitudinal direction perpendicular to a main direction in which a microwave propagates (as indicated by an arrow E in FIG. 20 A). Holes 21 A to 21 F allow an intense microwave to be radiated. Holes 21 B, 21 D, 21 E and 21 F allow a significantly intense microwave to be radiated. To allow holes 21 B, 21 D, 21 E and 21 F to efficiently radiate a microwave, these holes has a longitudinal dimension set to be approximately 55 mm to 60 mm.

In the present variation, rotative antenna 20 and subantenna 21 are stopped to position holes 21 A to 21 F in heating chamber 10 closer to door 3 . Thus, if the microwave oven is operated with these antennas stopped, placing a food in heating chamber 10 closer to the front side allows the food to receive an intensive microwave and thus be heated efficiently. Preferably, bottom plate 9 is for example transparent to allow subantenna 21 to be visible in heating chamber 10 and such is displayed in a vicinity of an area having holes 21 A to 21 F formed therein (an area F in FIG. 29 A), for example by using characters, such as “power zone”, to indicate that in that in the zone a food is intensively heated, or by corrugating a surface of the area, i.e., having a cross section as shown in FIG. 29 B.

Note that rotative antenna 20 is attached to spindle 15 A at the top end that is crimped polygonal rather than round as seen in cross section. Furthermore, as shown in FIG. 28 , hole 20 X has a cross section in the form of an octagon. Axis 15 A crimped to be polygonal as seen in cross section can prevent rotative antenna 20 from sliding relative to spindle 15 A when spindle 15 A is rotated to rotate rotative antenna 20 in a direction W. In other words, controlling an angle at which spindle 15 A rotates reliably controls an angle at which rotative antenna 20 rotates.

In the present variation as described above, rotative antenna 20 is provided with subantenna 21 insulated therefrom and rotative antenna 20 also configures a radiation antenna.

While in the present variation as described above rotative antenna 20 and subantenna 21 are combined together, an effect similar to that achieved by such a combination may be obtained simply by changing a dimension of rotative antenna 20 .

Simply changing rotative antenna 20 in dimension, however, imposes limitations on designing the heating chamber for example because: (1) a microwave is mostly radiated from rotative antenna 20 at an edge; (2) as rotative antenna 20 increases in dimension, microwave transmission loss also increases; and (3) to allow rotative antenna 20 to radiate a microwave efficiently, the antenna is required to have a dimension in relation to the wavelength of the microwave and the heating chamber thus cannot be sized as desired (for example, to allow the rotative antenna 20 edge to radiate a microwave with a maximal output, the length from spindle 15 A to the rotative antenna 20 edge is required to be closer to one fourth of the wavelength of the microwave that is multiplied by an even number.

In this regard, subantenna 21 only functions to a periphery of subantenna 21 a portion of a microwave radiated from rotative antenna 20 and its dimension does not contribute to transmission loss. Thus, subantenna 21 can be dimensioned as desired regardless of microwave radiation efficiency.

That is, rotative antenna 20 can be designed with a most efficient dimension and its edge can radiate a microwave and a portion of the radiated microwave can also be guided through subantenna 21 , dimensioned as desired, to a periphery thereof and thus radiated therefrom. As such, subantenna 21 is only required to have a dimension to consider the size of the heating chamber, which allows the heating chamber to be sized as desired.

Furthermore, since the heating chamber can receive a microwave radiated in a vicinity of an edge of rotative antenna 20 and a periphery of subantenna 21 , rotating rotative antenna 20 and subantenna 21 can supply the heating chamber with a microwave radiated more uniformly.

9. Fifth Variation

With reference to FIGS. 30-32 , in the present variation subantenna 22 is subantenna 21 of the fourth variation plus a reflector 22 X.

In the present variation a microwave oven includes an optical sensor 23 attached under body frame 5 .

Optical sensor 23 includes a light directing element and a light receiving element. The light directing element radiates light as indicated by an arrow V 1 at intervals of a predetermined temporal period. Rotative antenna 20 and subantenna 22 fixed to rotative antenna 20 are rotated by driving a motor 81 . When subantenna 22 that rotates has a position matching that allowing reflector 22 X to face optical sensor 23 , the sensor's light receiving element detects a reflection of light V 1 that is provided by reflector 22 X, as indicated by an arrow V 2 . From the detection of light V 2 by optical sensor 23 is derived that rotative antenna 20 and subantenna 22 have a predetermined position as they rotate. Furthermore, detecting a timing as counted from the time point when optical sensor 23 detects light V 2 , allows detecting the position of rotative antenna 20 and subantenna 22 as they rotate.

Thus, switch 89 as described in the fourth variation can be dispensed with and rotative antenna 20 and subantenna 22 can have their conditions directly detected as they rotate.

Furthermore in the present variation motor 81 provided to rotate spindle 15 A connected to rotative antenna 20 is attached at a (left) side of spindle 15 a , rather than under the spindle.

With reference to FIG. 33 , motor 81 has a spindle 81 A which is in turn connected to a cam 84 . The cam 84 rotation is transferred to a cam 82 and the cam 82 rotation is transferred to a spindle 83 and the spindle 83 rotation is transferred to spindle 15 A (see FIG. 31 ). In other words, when motor 81 is driven, spindle 81 A rotates and its rotation is transferred via cams 84 and 82 and spindle 83 to spindle 15 A.

In the present variation, motor 81 is arranged at a side of spindle 15 A. Thus motor 81 has a position that does not overlap a passage of food juice dropping from heating chamber 10 that is expected under heating chamber 10 , as indicated in FIG. 31 by arrows. Thus if food juice dropping in heating chamber 10 should move downward to under heating chamber 10 and long spindle 15 A, it cannot reach motor 81 .

10. Sixth Variation

With reference to FIG. 34 , the present variation provides a microwave oven corresponding to that of the fifth variation with cam 82 (see FIGS. 31 and 33 ) replaced by a came 85 having a periphery close to a switch 86 having a switch button 86 a pressed to switch a predetermined circuit on/off.

In the fifth variation, reflector 22 X is employed to detect the conditions of subantenna 22 and rotative antenna 20 as they rotate. In the present variation, in contrast, the condition of cam 85 as it rotates is detected to detect the conditions of subantenna 22 and rotative antenna 20 as they rotate.

The condition of cam 85 as it rotates is detected, as will now be described.

In FIG. 34 , G 1 denotes a direction in which cam 84 rotates, and G 2 denotes that in which cam 85 rotates. Cam 85 is basically round in geometry, although it has a protrusion 85 C. Protrusion 85 C is adjacent in the direction of rotation to a portion 85 A, which suddenly reduces in distance, as measured from the center (spindle 83 ), as it moves farther away from portion 85 C. Portion 85 C is also adjacent in the opposite direction of rotation to portion 85 B, which reduces in distance, as measured from the center (spindle 83 ), more gradually than portion 85 A. If cam 85 having such a peripheral geometry rotates in a direction G 2 , it can quickly press switch pattern 86 A with portion 85 A and gradually release it with portion 85 B.

Thus in the microwave oven of the present variation the condition of cam 85 as it rotates can be detected by switch 86 to detect those of rotative antenna 20 and subantenna 22 as they rotate. In doing so, switch button 86 A is quickly pressed and gradually released. Thus switch 86 can quickly respond to the condition of rotating cam 85 and switch button 86 A can also be free from rough operation.

Furthermore, in the present variation, rotating rotative antenna 20 and subantenna 22 are controlled to stop at a specific position after magnetron 12 has stopped its heating operation. More specifically, these antennas' rotation is stopped when two seconds have elapsed after switch button 86 A that is pressed is released following magnetron 12 having stopped its heating operation, when holes 21 A to 21 F of subantenna 22 are positioned closer to the front side of heating chamber 10 than the remainder of subantenna 22 . Note that holes 21 A to 21 F of subantenna 22 are, as well as those of subantenna 21 described for example with reference to FIG. 29 , are formed in the antenna at a location allowing a relatively intensive microwave radiation. More specifically in the microwave oven of the present variation when magnetron 12 stops its heating operation heating chamber 10 can have its internal front side heated intensively. Note that the heating chamber's internal front side is the door 3 side, a location readily accessible by a user to place a food. Thus in the microwave oven of the present variation when magnetron 12 starts a heating operation heating chamber 10 can have a portion readily accessible to place a food that is initially, intensively heated.

Furthermore in the present variation switch button 86 A does not remain pressed for a long period of time. This ensures that whenever switch button 86 A pressed is relieved of external force pressing the button the exact button is released. Thus switch 86 can have an extended longevity.

11. Seventh Variation

The present variation provides a microwave oven with cam 85 of the sixth variation replaced by a cam 850 . Cam 850 does not have such a protrusion as cam 85 of the sixth variation, although it has a reflector 851 . Furthermore in a vicinity of a circumference of cam 850 is provided an optical sensor 87 .

Optical sensor 87 includes a light directing element and a light receiving element. The light directing element radiates light, as indicated by an arrow H 1 , successively at predetermined temporal intervals. Cam 850 rotates in a direction G 2 . When the light receiving elements detects light indicated by an arrow H 2 , there is detected that rotating cam 850 has a position allowing reflector 851 to reflect light H 1 .

12. Eighth Variation

The fifth to seventh variations have described mechanisms provided to detect an angle of rotative antenna 20 and subantenna 21 or 22 as they rotate. In the present variation these mechanisms are used to control an angle of rotating rotative antenna 20 and subantenna 21 or 22 that is formed when they stop. Note that these antennas' stop position is controlled to heat a food in heating chamber 10 in a pattern suitable for the arrangement of the food. A pattern used to heat a food in heating chamber 10 will now be described.

As shown in FIG. 36 , for the sake of convenience, rotative antenna 20 with portion 20 A facing door 3 has a state of 0° and with hole 20 X serving as its center rotative antenna 20 rotates by α° in the direction indicated by the arrow in the figure (counterclockwise in FIG. 36 ) and then stops. In FIG. 36 , the letters “door side” opposite to rotative antenna 20 with a broken line therebetween indicates a positional relationship of door 3 relative to rotative antenna 20 .

As shown in FIG. 37 , heating chamber 10 has a bottom side divided into areas {circle around (1)} and {circle around (2)} for the sake of convenience. Areas {circle around (1)} and {circle around (2)} are located on the left and right sides, respectively, of heating chamber 10 , as seen from the front side, i.e., the door 3 side. Table 3 shows temperature elevation of a food placed in each of areas {circle around (1)} and {circle around (2)} and heated by magnetron 12 for a period of time with rotative antenna 20 stopped at predetermined angles of 0°, 90°, 180° and 270° or continuing to rotate.

TABLE 3
	Temperature	Temperature
Rotation Angle	Elevation of	Elevation of
α°	Load {circle around (1)} (° C.)	Load {circle around (2)} (° C.)
Continuous	18.6	19.3
Rotation
0°	20.4	19.1
90°	16.8	22.3
180°	17.5	18.9
270°	21.8	17.5

With reference to Table 3, if the foods are heated with rotative antenna 21 rotating, the foods placed in areas {circle around (1)} and {circle around (2)} have a difference in temperature elevation of less than 1° C. That is, it can be said that the areas experience substantially uniform temperature elevation. In contrast, if the foods are heated with rotative antenna 20 stopped, areas {circle around (1)} and {circle around (2)} can have a difference in temperature elevation.

More specifically, if the foods are heated with rotative antenna 20 stopped to position portion 20 A on the right side as seen at door 3 , i.e., rotated and stopped at 90°, the food in area 2 , on the right side as seen at door 3 , is heated more than 5° C. higher than that in area {circle around (1)}, on the left side as seen at door 3 .

Furthermore, if the foods are heated with portion 20 A positioned on the left side as seen at door, i.e., rotated and stopped at 270°, the food in area {circle around (1)}, on the left side as seen at door, is heated more than 4° C. higher than that in area {circle around (2)}, on the right side as seen at door 3 .

In contrast, if portion 20 A is positioned in heating chamber 10 on the front side or the rear side, i.e., at 0° or 180°, the foods in areas {circle around (1)} and {circle around (2)} do not have a significant difference in temperature elevation.

Thus, rotative antenna 10 having different stop positions results in heating chamber 10 internally having different portions intensively heated. Furthermore in the microwave oven of the present variation when a heating operation starts infrared sensor 7 is used to detect the pattern of the arrangement of a food placed in heating chamber 10 . More specifically, a decision is made on in which one of the FIG. 37 areas {circle around (1)} and {circle around (2)} a food exists, or if heating chamber 10 is divided into more areas a decision is made on which one of the areas a food exists. To do so, an area increased in temperature after a heating operation is started is determined as an area having the food arranged thereon.

Then the microwave oven refers to the food's arrangement pattern to select a heating pattern intensively heating the area having the food arranged thereon (that intensively heating area {circle around (1)} or {circle around (2)} on Table 3). At an angle corresponding to the selected heating pattern rotative antenna 20 (or 21 , 22 ) is stopped to heat the food. The Table 3 contents is stored for example in control circuit 30 .

Note that heating chamber 10 can be divided into further more areas and food temperature elevations in such areas for different angles of rotation α° can be stored as a Table 3. Thus Table 3 can contain further more heating patterns to provide a heat-cooking operation to better correspond to a food's actual arrangement pattern in heating chamber 10 .

Thus, a food's arrangement pattern in heating chamber 10 can be considered to stop the rotative antenna at a position to more efficiently heat the food.

13. Ninth Variation

FIG. 38 shows a variation of microwave oven 1 , corresponding to FIG. 3 .

In the present variation the microwave oven has a detection path member 40 having an upper portion with infrared sensor 7 attached thereto. Furthermore, detection path member 70 has a right portion with a motor 180 attached thereto to move a field of view of infrared sensor 7 .

Detection path member 40 has a top end provided with a hole 40 X surrounded by a cylinder 41 provided by barring a top end of detection path member 40 in the form of a sheer cylinder on the top end surface of detection path member 40 .

With reference to FIGS. 39-42 , cylinder 41 is formed to be partially increased in height to have a protrusion 41 A. In other words, cylinder 41 , with only protrusion 41 A increased in height, can readily be formed, barred.

As shown in FIG. 42 , infrared sensor 7 takes infrared radiation in through a detection hole 7 X to detect an amount of infrared radiation. In the present variation, as shown in FIG. 42 , when infrared sensor 7 is operated to detect an amount of infrared radiation in heating chamber 10 it has a position for example as indicated by the broken line and when it is not operated to detect infrared radiation it has a position allowing detection hole 7 X facing protrusion 41 A, as indicated by a solid line in FIG. 42 . The position of infrared sensor 7 when it is not operated for detection, as shown in FIG. 42 , corresponds to the position of infrared sensor 7 as shown in FIG. 38 . More specifically, protrusion 41 A of cylinder 41 is located windward of any other portions of cylinder 41 as fans 181 , 182 operates. As such, infrared sensor 7 , detecting through hole 41 X an amount of infrared evaluation in heating chamber 10 , is moved windward of hole 40 X when it is not operated for detection. Note that infrared sensor 7 and its field of view is moved by sensor motor 7 Z (see FIG. 9 B).

Thus, infrared sensor 7 when it is not operated for detection can have a detection component free of contaminants attributed for example to food juice scattering in heating chamber 10 .

Note that in the present variation when infrared sensor 7 is operated for detection or when the sensor in operation for detection is shifted to stop its operation for detection the sensor moves back and forth relative to heating chamber 10 . More specifically, it moves in direction Y in FIGS. 14 and 15 . More specifically, the present variation corresponds to a microwave oven including infrared sensor 7 having the field of view 70 A moving back and forth relative to heating chamber 10 , as has been described with reference to FIGS. 14 and 15 . It should be noted, however, that in the present variation infrared sensor 7 is only required to have a position windward of hole 40 X when it is not operated for detection, and it is not limited to an application with infrared sensor 7 moving back and forth relative to heating chamber 10 .

Furthermore, cylinder 41 can be provided with protrusion 41 A simply by barring a top end of detection path member 40 to increase cylinder 41 in height only partially, rather than entirely, to ensure a shelter for infrared sensor 7 when it is not operated for detection, and also to readily form cylinder 41 . Furthermore, the shelter can be positioned not so far from the position of infrared sensor 7 when it is operated for detection.

Furthermore in the present variation fans 181 , 182 are attached to cool magnetron 12 and other components. Infrared sensor 7 when it is not operate for detection is positioned windward of cylinder 41 as fans 181 , 182 operate. This ensures that infrared sensor 7 can have its detection component free of food juice scattering in heat chamber 10 .

In the present variation infrared sensor 7 has a field of view moving in a manner, as will now be described with reference to FIGS. 43-46 . In the present variation infrared sensor 7 is attached external to heating chamber 10 on an upper right side surface.

In the present variation infrared sensor 7 can have a field of view movable back and forth relative to heating chamber 10 , i.e., (in a direction indicated in FIG. 43 by a two-head arrow Y). In FIG. 43 , a collection of the sensor's fields of view that is provided rightmost in heating chamber 10 is shown in the form of a plane, i.e., a field of view 701 , and that of the sensor's fields of view which is provided leftmost in heating chamber 10 is shown in the form of a plane, i.e., a field of view 702 . In FIG. 43 , a prism 100 is drawn to assist in describing a manner in which the field of view of infrared sensor 7 moves.

The field of view 701 corresponds to a rightmost plane in heating chamber 10 in an area coverable by the field of view of infrared sensor 7 . As shown in FIG. 44 , infrared sensor 7 can pivot in a direction indicated by a two-head arrow K around an axis corresponding to a line located at a topmost portion of prism 100 (a line 101 in FIG. 44 ) to move its field of view back and forth relative to heating chamber 10 . In FIG. 43 , the field of view 701 is a plane parallel to a side plane of the prism. In other words, the field of view 701 is perpendicular to line 101 . This can minimize an area in heating chamber 10 on a side provided with infrared sensor 7 (the right side in FIG. 43 ) that is located on the front and rear sides and hence otherwise uncoverable by the sensor's field of view.

If infrared sensor 7 is attached to heating chamber 7 on a rearside and thus pivots rightward and leftward, infrared sensor 7 preferably pivots around an axis perpendicular to a plane corresponding to a collection of the sensor's fields of view that is provided most rearward.

More specifically, in the present variation if infrared sensor 7 pivots to move its field of view it pivots around an axis perpendicular to a plane within the entire region coverable by the sensor's field of view that is located in heating chamber 10 closest to the side of the heating chamber having the sensor attached thereto, as this can reduce in heating chamber 10 on a side having the sensor attached thereto an area uncoverable by the sensor's field of view. Thus, infrared sensor 7 can have a field of view covering heating chamber 10 over a wider area.

This effect can be described more specifically with reference to FIGS. 45 and 46 . In FIG. 45 , a prism 200 is shown to assist in describing how infrared sensor 7 moves.

In the FIGS. 45 and 46 comparison example, infrared sensor 7 has a field of view also moving back and forth (in a direction indicated by a two-head arrow Y) as infrared sensor 7 pivots. Of areas coverable by the pivoting sensor's field of view, the rightmost and leftmost planes are shown as fields of view 703 and 704 , respectively.

In this comparative example, infrared sensor 7 pivots around an axis corresponding to a rightmost line of prism 200 (a line 201 shown in FIG. 46 ). More specifically, as can be understood from FIG. 46 , in this comparative example the field of view 703 and line 201 form an acute angle. As such, the field of view 703 and heating chamber 10 form a line shorter in dimension than the depth of heating chamber 10 at that portion. More specifically, when FIG. 43 is compared with FIG. 45 , infrared sensor 7 can have a field of view covering in a much larger corner area closer to a side of heating chamber 10 having infrared sensor 7 attached thereto (i.e., the right side of the heating chamber 10 ) in FIG. 43 than in FIG. 45 .

It can thus be said that if infrared sensor pivots to move its field of view the sensor preferably pivots around an axis perpendicular to a plane within the entire region coverable by the sensor's field of view that is located in heating chamber 10 closest to a side of the heating chamber having the sensor attached thereto.

14. Tenth Variation

Reference will now be made to FIGS. 47 and 48 and 10 to describe a tenth variation of the present embodiment. The present variation mainly describes that in the microwave oven during a heat-cooking process infrared sensor 7 is employed to detect the temperature of a food in heating chamber 10 to automatically determine a timing at which the heating operation is terminated, as controlled in a manner as described hereinafter.

In the present variation, sensor motor 7 Z (shown in FIG. 9B ) can move the sensor 7 field of view in the direction of the width of heating chamber 10 (direction X in FIG. 10 ) and the direction of the depth of heating chamber 10 (direction Y in FIG. 10 ).

Initially at S 101 the control determines whether the microwave oven has received an input via a key. If so then the control goes to S 102 .

Then at S 102 the control determines whether at S 101 the microwave oven has received the input via a key instructing the microwave oven to provide a cooking and automatically detecting the end of the cooking (an automatic-cooking key). If so then the control goes to S 103 and if not then the control provides a process corresponding to the key of interest.

At S 103 the control determines whether the automatic-cooking key detected at S 102 selects a course using infrared sensor 7 to detect the temperature of a food in heating chamber 10 . If so then the control goes to S 104 and if not then the control provides a process corresponding to the course of interest.

At S 104 the control determines whether a key starting a heat-cooking operation (a start key) has been operated. If so then the control goes to S 105 .

At S 105 the control starts magnetron 12 to provide a heating operation and then goes to S 106 .

At S 106 the control resets contents recorded in memory about automatic-cooking and a flag and then goes to S 107 .

At S 107 the control sets a food sense temperature M 0 and then goes to S 108 . Food sense temperature M 0 is a target temperature for a heating operation. More specifically, when infrared sensor 7 senses the temperature the control terminates the current heating operation.

At S 108 the control turns on a lamp illuminating heating chamber 10 and starts rotation of rotative antenna 15 and then goes to S 109 .

At S 109 the control starts magnetron 12 and then goes to S 110 .

A S 110 the control controls infrared sensor 7 to start temperature detection and then goes to S 111 .

At S 111 the control controls infrared sensor 7 to move its field of view in heating chamber 10 back and forth to scan more than one location to detect a highest temperature and then goes to S 112 . The S 111 step will now be described more specifically with reference to FIG. 10 .

In the present variation infrared sensor 7 has a field of view moving in heating chamber 10 back and forth relative thereto (or in direction Y in FIG. 10 ) and rightward and leftward (or in direction X in FIG. 10 ). At S 111 if a field of view is represented in an X-Y coordinate system as p(X, Y), the field of view moves in a line with X=1 and Y varying from N to 1, then in a line with X=M 1 and Y varying from 1 to N, and then in a line with X=M 2 and Y varying from N to 1, wherein 1<M 1 <M 2 <M, i.e., it moves in the direction of the depth from a front side to a rear side, to a right side, from a rear side to a front side, further to a left side, from a front side to a rear side and the like to move throughout heating chamber 10 . While the field of view moves throughout heating chamber 10 , infrared sensor 7 senses temperature. A largest variation in temperature detected in heating chamber 10 in the direction of the depth thereof, is stored in memory. Temperature is detected in heating chamber 10 along a plurality of lines extending in direction Y and for each line there is calculated a difference between the largest and smallest value in temperature. The largest value of such differences correspond to the largest variation in temperature in the direction of the depth of the chamber.

At S 112 the control determines whether the largest variation MX stored at S 111 is at least a predetermined temperature LX. If so then the control goes to S 113 and if not then the control returns to S 111 and again extracts largest variation MX.

At S 113 the control determines whether ten seconds have elapsed since the latest temperature detection provided by infrared sensor 7 and if so then the control goes to S 114 .

At S 114 the control determines whether a flag F 0 is reset. If so then the control goes to S 115 and if it is set then the control goes to S 121 .

At S 115 the control moves the field of view of infrared sensor 7 in a line having the direction of the depth having detected MX subjected to the latest S 112 decision and the control circuit again controls infrared sensor 7 to sense temperature and then goes to S 116 . Note that at S 115 infrared sensor 7 has its field of view moving at a rate lower than at S 111 . More specifically, the rate at which the field of view moves at S 115 can be one fourth that at which the field of view moves at S 111 . More specifically in the present variation infrared sensor 7 has its field of view moving throughout heating chamber 10 at a relatively high speed to locate a food (S 111 -S 112 ) and once it generally determines a line on which the food exists it detects the temperature of the food precisely (S 115 ). Then temperature detection is provided on the line of interest to locate the food on the line of interest (S 116 to S 119 ).

At S 116 the control stores in memory a temperature elevation MY subjected to the S 115 temperature detection on a line at a point having attained a highest temperature value and then goes to S 117 .

At S 117 the control determines whether MY stored at S 116 is equal to or exceeds a predetermined temperature LY. If so then the control goes to S 118 and, having made a decision that a food exists at a location subjected to the latest S 116 MY detection, detects temperature with infrared sensor 7 having its field of view move in the direction of the depth including the location of interest and then goes to S 119 . The rate at which the field of view moves at S 118 is equal to that at which the field of view moves at S 115 .

At S 119 the control sets flag F 0 and returns to S 113 . Subsequently if flag F 0 remains set then the control goes to S 121 .

At S 121 the control controls infrared sensor 7 to move the field of view in a line in the direction of the depth, as predetermined, subjected to the S 118 temperature detection, to detect temperature, and the control stores a variation MZ in temperature at a location on the line of interest having a highest temperature value detected and then goes to S 122 . Note that the rate at which the field of view moves at S 121 is equal to that at which the field of view moves at S 115 .

At S 122 the control determines whether MZ stored at S 121 is equal to or exceeds a predetermined temperature LZ. If so then the control goes to S 123 and if not then the control goes to S 120 .

At S 120 the control determines whether five seconds have elapsed since the immediate previous temperature detection performed with a field of view moving in a line and if so then the control goes to S 114 .

In contrast at S 123 the control controls infrared sensor 7 to have a field of view fixed at a location having MZ stored at S 121 and continue to detect temperature and then the control goes to S 124 .

At S 124 in the field of view a food temperature M 1 is detected and then the control goes to S 125 .

At S 125 the control determines whether temperature M 1 detected at the immediately previously executed S 125 has attained M 0 set at S 127 . If not then the control goes back to S 124 and if so then the control moves to S 126 .

At S 126 the control provides a setting to terminate a heating operation and then goes to S 127 . At S 127 the control stops the heating operation provided by magnetron 12 , turns off the lamp illuminating heating chamber 10 and stops the rotation of rotative antenna 15 and the control then goes to S 128 . At S 128 the control controls a buzzer or the like to notify the user that the current heating operation ends. Then the microwave oven is placed in a waiting state.

15. Eleventh Variation

With reference to FIG. 49 , infrared sensor 7 includes eight infrared detection elements. At a time point these eight infrared detection elements have their respective fields of view 71 A- 78 A projected on a bottom plane of heating chamber 10 . Since the fields of view 71 A- 78 A together cover substantially the entire area of heating chamber 10 widthwise, heating chamber 10 has any area thereof widthwise covered by the field of view of an infrared detection element.

In the present variation, infrared sensor 7 is driven by sensor motor 7 Z (see FIG. 9B ) to pivot in a predetermined manner to move the fields of view 71 A- 78 A back and forth relative to heating chamber 10 to provide fields of view 71 B- 78 B and 71 C- 78 C, respectively. Thus, heating chamber 10 has any area thereof covered by the field of view of an infrared detection element.

Furthermore in the present variation each infrared detection element moves keeping a fixed distance as measured from the bottom plane of heating chamber 10 covered by the field of view of the infrared detection element. Thus in heating chamber 10 on the bottom plane an infrared detection element has a field of view covering a uniform area. More specifically, in heating chamber 10 on the bottom plane the fields of view 71 A- 71 C each cover an area of the same size and so do the fields of view 72 A- 72 C and 78 A- 78 C. Since each field of view thus moves, each infrared detection element can have a field of view covering a constant area of heating chamber 10 . Thus in the present variation each infrared detection element can detect temperature with constant precision, since the amount of infrared radiation that the infrared detection element can detect depends on the size of the area covered by the field of view of the infrared detection element.

16. Twelfth Variation

With reference to FIGS. 50 and 51 , infrared sensor 7 includes five infrared detection elements 701 - 705 . Also drawn in FIGS. 50 and 51 are centerlines 701 A- 705 A each representing the center of the field of view of a respective one of infrared detection elements 701 - 705 .

In the present variation infrared detection elements 701 - 705 have their respective fields of view passing through hole 40 X provided in detection path member 40 and thus reaching heating chamber 10 . Infrared detection elements 701 - 705 are arranged to allow their respective fields of view to have their respective centerlines 701 A- 705 A traversing each other in hole 40 X at a point Q. As such, hole 40 X can be minimized in diameter.

Hole 40 X reduced in diameter can further prevent food juice and the like scattering in heating chamber 10 from reaching infrared detection elements 701 - 705 .

Note that in the present variation infrared sensor 7 may have infrared detection elements 701 - 705 arranged in a line, as shown in FIG. 52 , or it may have a plurality of infrared detection elements 7 A on an internal wall surface of a sphere two-dimensionally, as shown in FIG. 53 . Note that in both FIGS. 52 and 53 , the plurality of infrared detection elements 7 A and 701 - 705 have their respective fields of view having their respective centers traversing each other in hole 40 X before extending into heating chamber 10 . Furthermore, if the FIG. 53 infrared sensor is used, heating chamber 10 is entirely covered by the fields of view of infrared detection elements 7 A at one time such that any area of the chamber is covered by the field of view of an infrared detection element 7 A.

17. Thirteenth Variation

With reference to FIG. 54 , in the present variation infrared sensor 7 includes infrared detection elements 701 - 705 described with reference to FIG. 50 plus an infrared detection element 706 . While infrared detection elements 701 - 705 have their respective fields of view all directed through hole 40 X to heating chamber 10 , infrared detection element 706 has a field of view half blocked by a detection path member 40 and thus failing to enter heating chamber 10 .

In the present variation if in heating chamber 10 infrared detection element 706 has a field if view 706 X detecting a food then the control determines that the food's temperature cannot be detected accurately and the control stops the current heating operation, as will now be described more specifically with reference to FIG. 55 .

With reference to FIG. 55 , in the present variation the control initially controls magnetron 12 to start a heating operation and then at S 201 drives sensor motor 7 Z (see FIG. 9B ) to allow any area of heating chamber 10 to be covered by the field of view of an infrared detection element. In other words, the infrared detection elements have their fields of view scanning throughout heating chamber 10 for temperature detection.

Then at S 201 the control determines whether a food has been located in heating chamber 10 . This decision is made based for example on whether there has been detected an area heated as time elapses. If such an area has been detected the control determines that the area includes the food and the control goes to S 203 .

At S 203 the control determines whether the food is located by an end of the field of view of infrared sensor 7 . Herein, the field of view of infrared sensor 7 corresponds to a collection of the fields of view of infrared detection elements 701 - 706 and the end of the field of view of infrared sensor 7 corresponds to the field of view 706 X, the field of view of infrared detection element 706 that is introduced into heating chamber 10 . That the field of view 706 covers a food means that the food is only partially covered by the field of view of infrared sensor 7 . More specifically, if infrared sensor 7 has a total field of view 700 in heating chamber 10 , as shown in FIG. 56 , a food R exists in heating chamber 10 , only partially covered by the total field of view 700 .

Thus infrared sensor 7 (or infrared detection elements 700 - 706 ) can hardly sense the temperature of food R accurately. As such, if at S 203 the control determines that the food is located by an end of the field of view of infrared sensor 7 then it goes to S 206 and at that time point controls magnetron 12 to stop the current heating operation to terminate the current process.

Note that if at S 203 the control determines that the food is located by an end of the field of view of infrared sensor 7 then at S 204 the control continues to detect the temperature of the food and if the food has attained a set, finish temperature corresponding to a temperature at which a heating operation should be terminated the control (S 205 ) stops the current heating operation and ends the current process.

The techniques disclosed in the embodiments and variations may be used individually or combined together.

Furthermore, as long as they are allowed, the techniques disclosed in the embodiments and variations are applicable to both infrared sensor 7 including a single infrared detection element and that including a plurality of infrared detection elements.

Furthermore, if infrared sensor 7 includes a plurality of infrared detection elements arranged in a rectangle and the exact infrared sensor 7 moves to move the fields of view of the infrared detection elements, infrared sensor 7 should move at least in a direction in which a shorter side of the rectangle extends. For example, if infrared sensor 7 includes infrared detection elements 7 A arranged in a line, as shown in FIG. 57 , or in multiple lines, as shown in FIGS. 58 and 59 , infrared sensor 7 should move in a direction indicated by a two-head arrow N. Moving infrared sensor 7 in direction N can provide a maximal variation of an area further covered by a field of view of infrared detection element 7 a , relative to the distance in which each infrared sensor 7 moves. In other words, temperature can be detected throughout heating chamber 10 more rapidly.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.

Claims

1. A microwave oven accommodating an object to be heated, comprisinga heating chamber further comprising a bottom surface, for receiving food thereon, and a side wall intersecting said bottom surface, a plurality of infrared detection elements mounted outside said side wall above a point on an intersection of said side wall and said bottom surface, the infrared detection elements comprising respective fields of view in said heating chamber to detect respective amounts of infrared radiation in said fields of view, said plurality of infrared detection elements being arranged to have said fields of view which align substantially in a first direction to cover an elongated area on said bottom surface, said first direction being substantially perpendicular to said side wall, further comprising a drive unit driving said plurality of infrared detection elements to move said elongated area along said bottom surface in a second direction traversing said first direction.

2. The microwave oven of claim 1,wherein said second direction is perpendicular to said first direction, whereby a predetermined rectangle is scanned by said drive unit and said infrared detection elements; and said drive unit drives said plurality of infrared detection elements to move along a shorter side of said predetermined rectangle.

3. A microwave oven according to claim 1, further comprising:a heating unit provided to heat said object to be heated; a temperature calculation unit calculating from an output received from each said infrared detection element a temperature of said object to be heated attained in each said field of view; and a control unit referring to said temperature to control said heating unit, wherein said control unit calculates a variation in said temperature introduced within a predetermined temporal period for each said field of view, sets said field of view, sets said variation having a largest value and said variation having a value having at least a predetermined percentage relative to said variation having said largest value as specific variations for said predetermined temporal period, sets as a specific field of view said field of view corresponding to said specific variation for said predetermined temporal period, and refers to said temperature in said specific field of view to control said heating unit.

4. The microwave oven of claim 3, said microwave oven including more than one said infrared detection element arranged in said first direction, further comprising means for controlling said more than one said infrared detection element to detect said temperature while moving said more than one said infrared detection element in said second direction traversing said first direction.