Heat cooking device allowing control of fan rotation number

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat cooking device and, more specifically, to a heat cooking device including a fan for feeding air from an inlet to an outlet through an air path.

2. Description of the Background Art

A conventional heat cooking device is provided with a fan for cooling a high voltage transformer or a magnetron as heating means. Among heat cooking devices, for a microwave oven installed at a high place, for example on a wall or on a kitchen cabinet, a fan has been provided not only for cooling but also for allowing use of the device simply as a ventilation fan.

In some of the conventional heat cooking devices, some allow selection of direction of exhaustion of the fan from a plurality of directions. For example, a device of the type installed on a kitchen cabinet, allows the user to select the direction of exhaustion into or out from the room.

In such type of heat cooking device, however, when the direction of exhaustion of the fan is set into the room, the noise at the time of exhaustion or ventilation has been rather large and unpleasant for the user.

SUMMARY OF THE INVENTION

The present invention was made in view of the foregoing, and its object is to provide a heat cooking device which can avoid such unpleasantness of the user.

The heat cooking device in accordance with the present invention includes heating means, an inlet, an outlet, and a fan feeding air from the inlet through an air path to the outlet, additionally including driving means for driving the fan, the fan is installed in any of a plurality of different manners of installation feeding air in different directions, the driving means controls the fan such that the fan rotates at a certain number of rotation within a prescribed range, and the prescribed range of the number of rotation is determined dependent on the manner of installation of the fan.

In the heat cooking device of the present invention, the range of the number of rotation of the fan is determined dependent on the manner of installation of the fan. Therefore, it becomes possible to lower the number of rotation of the fan only when the direction of exhaustion of the fan may cause noise unpleasant for the user, at the time of exhaustion.

Preferably, the different manners of installation include a first manner of installation in which the fan feeds air to the room, and a second manner of installation in which the fan feeds air to the outside, and the driving means determines the prescribed range for the first manner of installation to be smaller in the number of rotation, than the prescribed range for the second manner of installation.

Accordingly, when the fan exhausts air to the room, the number of rotation of the fan is made lower than when the air is exhausted to the outside, possibly lowering noise at the time of exhaustion.

Preferably, the manner of installation of the fan is changeable, and the device further includes input means capable of receiving as an input information of the manner of installation after the change. The driving means determines the prescribed range of the number of rotation based on the information of the manner of installation after the change input through the input means.

Accordingly, it is possible for the user to change the manner of installation of the fan, and the fan rotates at an appropriate number of rotation, in accordance with the manner of installation after the change.

Preferably, there are a plurality of outlets, the fan includes a cover capable of feeding air to any of the plurality of outlets and opening/closing a prescribed outlet among the plurality of outlets, and cover opening/closing means capable of controlling opening/closing of the cover, the cover opening/closing means keeps the cover in the closed state and opens/closes the cover in accordance with the operation of the fan only when the fan is installed in such a manner of installation in that the air is fed to the prescribed outlet.

Accordingly, when it is unnecessary to open the prescribed opening, the opening is closed by the cover. Therefore, entrance of dust or the like to the heat cooking device can surely be avoided.

Preferably, the device further includes an oil filter and a charcoal air filter provided at the inlet.

Namely, a plurality of filters are provided adjacent to each other. Therefore, maintenance including exchange of the plurality of filters is facilitated.

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

FIGS. 1A and 1B

represent a microwave oven in accordance with an embodiment of the present invention.

FIGS. 2A and 2B

represent details of the configuration of the microwave oven shown in

FIGS. 1A and 1B

.

FIG. 3

is a schematic diagram showing electric circuitry of the microwave oven shown in

FIGS. 1A and 1B

.

FIG. 4

is a cross section taken along the line IV—IV of

FIGS. 1A and 1B

.

FIGS. 5 and 6

are perspective views of the microwave oven shown in

FIGS. 1A and 1B

.

FIG. 7

is an illustration representing how a hood fan is attached to a the body of the microwave oven shown in

FIGS. 1A and 1B

.

FIG. 8

shows the hood fan installed facing forward, in the microwave oven of

FIGS. 1A and 1B

.

FIG. 9

shows the hood fan installed facing upward, in the microwave oven of

FIGS. 1A and 1B

.

FIG. 10

shows the hood fan installed facing backward, in the microwave oven of

FIGS. 1A and 1B

.

FIG. 11

shows the microwave oven of

FIGS. 1A and 1B

without the hood fan.

FIGS. 12

,

13

and

14

are illustrations showing the cover opening/closing mechanism of the microwave oven shown in

FIGS. 1A and 1B

.

FIG. 15

is an illustration showing the shape of the member for fixing a filter of the microwave oven shown in

FIGS. 1A and 1B

.

FIGS. 16A and 16B

show the manner of supporting an oil filter and a charcoal air filter by stepwise guides and top guides, of the microwave oven shown in

FIGS. 1A and 1B

.

FIGS. 17A and 17B

are illustrations showing the manner of attachment of a charcoal air filter in the microwave oven shown in

FIGS. 1A and 1B

.

FIGS. 18A

,

18

B and

18

C are illustrations showing the manner of attachment of the oil filter in the microwave oven shown in

FIGS. 1A and 1B

.

FIG. 19

is a flow chart of a process for setting the speed of rotation, executed by the control circuit, in the microwave oven of FIGS.

1

A and

1

B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described in detail with reference to the figures. In the following, a microwave oven installed at a high place, for example on a kitchen cabinet, will be described as an example of the heat cooking device. The present invention, however, it not limited thereto, and it may be applied to a movable microwave oven not installed at a fixed position. The present invention is applicable to any heat cooking device which has a fan and configured to take the air into the device and to exhaust the air out from the device.

FIGS. 1A and 1B

are illustrations of a microwave oven in accordance with an embodiment of the present invention.

FIG. 1A

shows the appearance of the microwave oven. Microwave oven

1

includes a front panel

5

and a door

3

at the front surface of a body

4

. An inlet and an outlet (an inlet

21

and outlets

2

,

22

as will be described later, not shown in

FIG. 1A

) are provided above the front panel

5

and door

3

, and a cover

7

is provided to cover the inlet and the outlet. A control panel

51

is provided on front panel

5

, allowing the user to input contents of operation of microwave oven

1

. Though not shown, a display unit capable of displaying time of cooking and the like is provided on control panel

51

. Microwave oven

1

is provided directly above a gas range

83

in a kitchen cabinet

82

.

FIGS. 2A and 2B

show details of the configuration of microwave oven

1

shown in

FIGS. 1A and 1B

.

FIG. 2A

is a perspective view of microwave oven

1

viewed from below. Referring to

FIG. 2A

, at the bottom portion of microwave oven

1

, there are kitchen lamps

42

and

43

. When the user cooks using the gas range

83

, he/she may turn on kitchen lamps

42

and

43

. Heat resistant glasses

42

a

and

43

a

are provided below kitchen lamps

42

and

43

, respectively.

A bottom hole

67

is formed in the bottom portion of microwave oven

1

. Microwave oven

1

is capable of taking smoke or the like inside microwave oven

1

and exhausting the smoke or the like in an appropriate direction, through the bottom hole

67

, by means of a fan provided in the microwave oven. As will be described later, a filter is fitted in the bottom hole

67

, and the smoke and the like are taken in to the microwave oven

1

through the filter.

FIG. 2B

shows internal structure of microwave oven

1

, representing microwave oven

1

with the front panel

5

, door

3

and cover

7

detached. Referring to

FIG. 2B

, there is a heating chamber

30

accommodating the object of heating such food behind the door. A heating chamber lamp

41

for illuminating the heating chamber

30

is provided above heating chamber

30

.

FIG. 3

is a schematic diagram showing an electric circuitry for microwave oven

1

. Referring to

FIG. 3

, a reference numeral

55

denotes an AC power supply, supplying power to the entire circuit shown in FIG.

3

. Reference numeral

33

denotes a magnetron, and

66

denotes a high voltage transformer supplying a high voltage to magnetron

33

.

A switch

57

is a door switch adapted to open the circuit shown in

FIG. 3

when door

3

is opened, and closes the circuit when door

3

is closed. Therefore, when door

3

of microwave oven

1

is opened, door switch

57

opens the circuit, preventing power supply from AC power supply

55

to high voltage transformer

66

, so as to prevent generation of electric wave from magnetron

33

.

In the figure, reference numerals

58

and

59

denote an output adjusting relay and a main relay, regulating conduction of magnetron

33

for heating and cooking. Main relay

59

is kept on while heating and cooking is being performed, while the output adjusting relay

58

is repeatedly turned on/off during heating and cooking, so as to adjust the output of magnetron

33

. Output adjusting relay

58

and main relay

59

are turned on/off under the control of control circuit

65

.

Control circuit

65

includes a microcomputer and a memory, not shown. Control circuit

65

controls turning on/off of main relay

59

and output adjusting relay

58

, in accordance with a cooking recipe input by the user through control panel

51

, by means of the microcomputer. Further, control circuit

65

stores cooking information, such as heating time, in the memory as needed. In the figure, reference numeral

64

denotes a constant voltage circuit supplying a power of a constant voltage to control circuit

65

.

Reference numeral

60

denotes a monitor switch which is adapted to close the circuit shown in

FIG. 3

when door

3

is opened and to open the circuit when door

3

is closed, contrary to door switch

57

. Monitor switch

60

ais provided for avoiding conduction of power to magnetron

33

by forming a short-circuit and blowing off fuse

56

, when the door switch

57

fails to open the circuit by some cause even when door

3

is opened. Accordingly, a dangerous situation where magnetron

33

generates a high frequency electric wave with the door

3

opened can surely be avoided.

In the figure, reference numeral

17

denotes a blower motor driving a fan (fan

34

, which will be described later) for cooling magnetron

33

mentioned above. Reference numeral

41

denotes a heating chamber lamp illuminating heating chamber

7

. Reference numerals

18

and

47

denote relay switches controlling conduction of power to blower motor

17

and heating chamber lamp

41

, respectively. Relay switches

18

and

47

are turned on/off under the control by control circuit

65

.

Kitchen lamps

42

and

43

are connected to constant voltage circuit

64

. In the figure, reference numeral

49

denotes a relay switch controlling conduction of power to kitchen lamps

42

and

43

. A cover motor

45

for opening/closing cover

7

, and a fan motor

44

for driving a hood fan (hood fan

8

, which will be described later) which is used when microwave oven

1

is made use of a ventilation fan, are also connected to constant voltage circuit

64

. Conduction of power to fan motor

44

and cover motor

45

is controlled by relay switches

46

and

48

, respectively. Relay switches

46

,

48

and

49

are turned on/off under the control of control circuit

65

. Fan motor

44

has a connector

50

A. Microwave oven

1

has a connector

50

B. When connectors

50

A and

50

B are connected, fan motor

44

is electrically connected to the body of microwave oven

1

.

The hood fan (hood fan

8

as will be described later) may be attached in different direction for feeding air. It is possible for the user to detach or remove the hood fan and attach the fan again on the body of microwave oven

1

, so as to change the direction of air from the hood fan. The plurality of directions of feeding air includes a direction of feeding air through an outlet (outlet

2

) which is opened/closed by cover

7

to the outside of microwave oven

1

. The user may input the direction of air feed of hood fan, through control panel

51

. Therefore, when the direction of air feed of hood fan is set to feed air out from microwave oven

1

through the outlet (outlet

2

) as will be described later, cover

7

is opened/closed in accordance with the operation of the hood fan.

Control panel

51

and a thermistor

63

are connected to control circuit

65

. Thermistor

63

is provided near the outlet (outlet

2

) of microwave oven

1

, as will be described later. When a temperature detected by thermistor

63

is excessively high and cover

7

is closed, control circuit

65

forces cover

7

open. A fan switch

61

is connected to control circuit

65

. The operation of fan switch

61

will be described later with reference to FIG.

8

and the like.

FIG. 4

is a cross section taken along the line IV—IV of

FIGS. 1A and 1B

.

FIG. 5

is a perspective view of microwave oven

1

shown in

FIGS. 1A and 1B

, with an outer casing of body

4

omitted, so as to show the details of the internal structure of microwave oven

1

.

Referring to

FIGS. 4 and 5

, microwave oven

1

includes, in its body

4

, an inner frame

11

and an air passage

12

. Inner frame

11

is so structured as to surround heating chamber

30

, a mechanical chamber

31

accommodating electronic components (magnetron

33

and the like) for heating control and the like, and an exhaustion chamber

32

to which air exhausted from heating chamber

30

is fed. At a bottom plate

6

as a wall surface of air passage

12

and the bottom surface of body

4

, a bottom hole

67

is provided. Two hood fans

8

are provided on inner frame

11

. An inlet

21

and outlets

2

,

22

covered by a cover

7

are formed at an upper portion of front panel

5

. In the figure, reference numeral

10

denotes a body guide guiding the air fed from hood fan

8

only to the outlet

2

. Though a filter is provided near the bottom hole

67

, it is not shown in FIG.

4

.

Hood fan

8

outlets air through an outlet opening

8

A. When hood fan

8

operates in microwave oven

1

, cover

7

is set from the close state shown in

FIGS. 1A and 1B

to the open state shown in FIG.

5

. As represented by white arrows in

FIGS. 4 and 5

, air is taken from bottom hole

67

to air passage

12

, and the air is exhausted through outlet

2

to the outside of microwave oven

1

, through hood fan

8

. As the cover

7

is provided in front of outlet

2

, the air can be exhausted diagonally upward from outlet

2

. Namely, cover

7

is capable of controlling the direction of air flow exhausted from outlet

2

(and outlet

22

). In this manner, the air is taken from the bottom hole

67

and exhausted through outlet

2

of microwave oven

1

, and therefore, microwave oven

1

can be used as a ventilation fan, when gas range

88

is used for cooking.

A partition panel

71

and a handle

72

are provided on cover

7

. Partition panel

71

is provided for preventing air exhausted from outlet

2

from directly taken into microwave oven

1

through inlet

21

, and handle

72

is provided for enabling manual switching of opening/closing of cover

7

. Opening/closing of cover

7

is basically switched by a cover motor

45

. Provision of handle

72

, however, enables manual opening/closing of cover

7

, especially when portions near the inlet

21

and outlets

2

,

22

are to be cleaned without operating hood fan

8

or fan

34

, or when a member for automatically opening/closing cover

7

fails.

Referring to

FIG. 5

, reference numeral

52

represents an air chamber to which the air taken through inlet

21

is fed, which chamber is connected to mechanical chamber

31

. Microwave oven

1

includes a fan (fan

34

, which will be described later) separate from hood fan

8

, by means of which the air can be fed in a manner different from the air flow shown in

FIGS. 4 and 5

. This different air flow in microwave oven

1

will be described in the following, with reference to FIG.

6

.

FIG. 6

is a perspective view of microwave oven

1

with an outer case portion of body

4

removed, similar to FIG.

5

. In

FIG. 6

, the air flow in a manner different from that described above is represented by white arrows. Further, in

FIG. 6

, the inner frame

11

is partially exploded, so as to show the inner structure of mechanical chamber

31

.

Microwave oven

1

includes, in mechanical chamber

31

, magnetron

33

for heating the object of heating in heating chamber

30

, and a fan

34

for cooling components such as magnetron

33

. When fan

34

operates in microwave oven

1

, cover

7

moves from the closed state shown in

FIG. 1

to the open state shown in

FIG. 5

(or FIG.

6

), the air is taken from inlet

21

through air chamber

52

and mechanical chamber

31

to heating chamber

30

, and the air is exhausted through exhaustion chamber

32

and outlet

22

to the outside of microwave oven

1

, as represented by the white arrows.

As described above, air flows in different manners in microwave oven

1

, by the operations of hood fan

8

and fan

34

. In microwave oven

1

, when hood fan

8

or fan

34

operates, cover

7

is opened by control circuit

65

, in microwave oven

1

as will be described later. When the operation of hood

3

fan

8

and fan

34

is stopped, cover

7

is set to the closed state. In microwave oven

1

, when heating and cooking by magnetron

33

is performed, fan

34

operates automatically. A hood fan

8

may be operated by a prescribed key operation through control panel

51

. In other words, in microwave oven

1

, hood fan

8

and fan

34

operate independent from each other.

Referring to

FIGS. 5 and 6

, outlet opening

8

A of hood fan

8

faces forward (in the direction of door

3

). As will be described later, the direction of outlet opening

8

A of hood fan

8

may be set facing forward, rearward or upward. In the following, the manner of setting of hood fan

8

with the direction of outlet opening

8

A facing forward, backward and upward will be referred to as front-setting, back-setting and up setting, respectively.

FIG. 7

is an illustration related to attachment of hood fan

8

on microwave oven

1

.

FIG. 7

is a perspective view of microwave oven

1

, viewed from the back-left side. In

FIG. 7

, hood fan

8

is in up-setting.

Referring to

FIG. 7

, hood fan

8

is attached in the direction of the arrow P, from behind the body of microwave oven

1

. At the time of attachment, a connector

50

A of hood fan

8

is connected to a connector

50

B on the body of microwave oven

1

. In microwave oven

1

, a presser plate

26

for fixing hood fan

8

is attached, above hood fan

8

. Presser plate

26

is fixed on the body of microwave oven

1

and hood fan

8

by screws. Presser plate

26

has an upper outlet

27

. Upper outlet is provided at a position corresponding to outlet opening

8

A of hood fan

8

. Therefore, even when the hood fan

8

is in up-setting, presser plate

26

does not interfere the air flow coming out from outlet opening

8

A.

The front-setting, up-setting and back-setting of hood fan

8

will be described in the following, with reference to

FIGS. 8

to

10

.

FIGS. 8

to

10

are schematic illustrations showing the manner of setting of hood fan

8

viewed from the right side of microwave oven

1

, showing hood fan

8

in front-setting, up-setting and back-setting, respectively.

First, referring to

FIG. 8

, in front-setting, the air blown out from outlet opening

8

A proceeds in the direction of the white arrow in the figure, and exhausted through outlet

2

to the outside of microwave oven

1

. Below hood fan

8

, there is a fan switch

61

arranged. Fan switch

61

has a switch button

62

(see

FIG. 11

) on an upper portion thereof. In the state shown in

FIG. 8

, hood fan

8

presses switch button

62

, so that the button is embedded in the body of fan switch

61

. Fan switch

61

changes the state of opening/closing of the circuitry shown in

FIG. 3

dependent on whether switch button

62

is pressed or not. Therefore, it is possible for control circuit

65

to detect whether hoof fan

8

is attached in such a position as shown in

FIG. 8

, by detecting the state of opening/closing of the circuitry which depends on fan switch

61

.

In

FIG. 8

, it can be seen that microwave oven

1

is provided with an oil filter

35

and a charcoal air filter

36

at its bottom portion. Oil filter

35

is to prevent oil resulting from cooking by gas range

83

from entering microwave oven

1

. Charcoal air filter

36

is provided for preventing soot resulting from cooking by gas range

83

from entering microwave oven

1

. These filters are supported by a member attached to bottom plate

6

. Details of the manner of support will be described later.

Further, it can seen from

FIG. 8

that microwave oven

1

includes a thermistor

63

near outlet

2

. Control circuit

65

forces cover

7

open when the temperature detected by thermistor

63

is excessively high, as described above. The place where thermistor

63

is provided is not limited to the vicinity of outlet

2

.

Referring to

FIGS. 9 and 10

, no matter whether hood fan

8

of microwave oven

1

is in the up-setting or back-setting state, switch button

62

of fan switch

61

is pressed by hood fan

8

.

Microwave oven

1

is configured to allow a user to input the manner of setting of hood fan

8

through control panel

51

. When the manner of setting is input to be back-setting or up-setting, cover

7

is basically not open when fan

34

is not in operation, even when hood fan

8

is in operation.

When the manner of setting of hood fan

8

of microwave oven

1

is input to be front-setting, the number of rotation of hood fan

8

(the number of rotation per unit time) is set to be lower than when the setting is input to be back-setting or up-setting, as will be described later.

Here, as a reference,

FIG. 11

shows a state where hood fan

8

is not attached to microwave oven

1

. When hood fan

8

is not attached, switch button

62

is not pressed by hood fan

8

and protruded from fan switch

61

, as can be seen from FIG.

11

.

The mechanism for opening/closing cover

7

will be described with reference to

FIGS. 12

to

14

. Referring to

FIG. 12

, cover

7

has a connecting portion

7

A and connected to the body of microwave oven

1

through connecting portion

7

A. A partition panel

71

of cover

7

has a slit

71

A at a back portion thereof.

At a position opposing to the back side of the main surface of partition plate

71

, a cover motor

45

is provided. Cover motor

45

has an arm

45

B. When cover motor

45

operates, arm

45

B rotates, with a center of rotation

45

A at one end serving as a fulcrum. A projection

45

C is provided at the other end of arm

45

B. Projection

45

C is fitted in slot

71

A. Therefore, when arm

45

B rotates, partition panel

71

acts as a cam, opening/closing cover

7

.

A leaf spring

85

is provided above partition panel

71

. Leaf spring

85

presses at its lower end, an upper end of the rearmost portion of partition panel

71

. Therefore, cover

7

as a whole functions as a “lever” (fulcrum: connecting portion

7

A, effort: contact with leaf spring

85

, load: contact with an outer frame of outlet

2

). Therefore, the forward most portion of cover

7

surely closes outlet

2

. Namely, when in the closed state (state of FIG.

12

), cover

7

is surely fixed in that state. Therefore, there is no space generated between cover

7

and the body of microwave oven

1

when cover

7

is closed. In the state shown in

FIG. 12

, cover

7

is closed. A mechanism for opening cover

7

from this state will be described in the following.

When cover motor

45

operates in the state of

FIG. 12

, arm

45

B rotates counterclockwise in the figure, with the center of rotation

45

A being the fulcrum. Thus, the contact between leaf spring

85

and partition panel

71

gradually shifts backward.

A rear end of partition panel

71

is arcuate. Radius of curvature of the rear end of partition panel

71

differs portion from portion. More specifically, the radii of curvature of the rear end may be RA, RB and RC from the upper portion, as shown in FIG.

12

. RA represents the radius of curvature of the upper end portion of the rear end, RB represents radius of curvature of a middle portion of the rear end, and RC represents the radius of curvature of the lower end portion of the rear end. The center of a circle formed by the arc RB is the connecting portion

7

A. Further, RA<RB. More specifically, the portion denoted by RA has steeper curve than the portion RB.

When cover motor

45

operates and arm

45

B rotates by a prescribed angle, the contact between leaf spring

85

and partition panel

71

moves to the rearmost end of the range represented by RA, as can be seen from FIG.

13

.

When cover motor

45

further operates from the state shown in

FIG. 13

, partition panel

71

comes to be in non-contact with leaf spring

85

as shown in FIG.

14

. The reason for this may be the fact that RA<RB.

More specifically, in the mechanism for opening/closing cover

7

described with reference to

FIGS. 12

to

14

, cover

7

opens/closes with a prescribed point (connecting point

7

A) serving as a fulcrum. Partition panel

71

has a first portion denoted by RA and a second portion denoted by RB at its rear end. The second portion is continues from the first portion and provided lower than the first portion. The first portion and the second portion have the first and second curvatures, respectively, with the second curvature being smaller than the first curvature. More specifically, the portion denoted by RA has steeper curve than the portion denoted by RB. The center of the circle, a part of which is the second portion, is the fulcrum. When the cover is closed, in the state of

FIG. 12

, leaf spring

85

engages from upward with the partition panel

71

of cover

7

. Here, radius of curvature RB is shorter than the shortest distance between leaf spring

85

and connecting portion

7

A (in this case, distance between the lower end of leaf spring

85

and connecting portion

7

A). The distance between the region denoted by RA of the outer periphery of partition panel

71

and connecting portion

7

A is equal to the shortest distance between leaf spring

85

and connecting portion

7

A.

Attachment of oil filter

35

and charcoal air filter

36

will be described in the following.

FIG. 15

is an illustration showing the member for fixing oil filter

35

and charcoal air filter

36

, which corresponds to the bottom portion of microwave oven

1

viewed from the inside.

In microwave oven

1

, there are two pairs of step guides

69

and a pair of top guides

68

provided opposing to each other at an end portion of bottom hole

67

. Top guide

68

and step guide

69

are formed integrally with bottom plate

6

. More specifically, those portions of bottom plate

6

which are to be cut out as bottom hole

67

are not cut out but left, with the left portions bent to provide top guides

68

and step guides

69

. Therefore, the top guides

68

and step guides

69

can be formed without the necessity of preparing material different from the material of bottom plate

6

.

FIGS. 16A and 16B

show manner of supporting oil filter

35

and charcoal air filter

36

by step guides

69

and top guides

68

. Referring to

FIGS. 15 and 16A

and

16

B, step guide

69

includes, in this order from the lower portion, a first surface continuous from bottom plate

6

and vertical to bottom plate

6

, a second surface continuous from the first surface and parallel to the bottom plate

6

, and a third surface continuous from the second surface and vertical to the bottom plate

6

. More specifically, step guide

69

has two surfaces vertical to bottom plate

6

. Upper and lower two surfaces vertical to bottom plate

6

of opposing step guides

69

grip and hold two filters from opposing sides.

Top guide

68

is for pressing from above the upper filter of the two filters (in the present embodiment, charcoal air filter

36

).

The manner of attachment of two filters using step guides

69

and top guides

68

will be described with reference to

FIGS. 17A

to

18

C.

When the two filters are to be attached, first, charcoal air filter

36

is attached. Therefore, attachment of charcoal air filter

36

will be described first. Referring to

FIG. 17A

, a rear end (right end in

FIG. 17A

) of charcoal air filter

36

is inserted to the inside of microwave oven

1

through bottom hole

67

. Thereafter, the front end (left end in

FIG. 17A

) of charcoal air filter

36

is moved in the direction of the arrow X, that is, upward, to be inserted to the inside of microwave oven

1

, through bottom hole

67

.

Thereafter, charcoal air filter

36

is fitted in between step guides

69

, and thus the charcoal air filter

36

is attached as shown in FIG.

17

B.

Attachment of oil filter

35

will be described next. Referring to

FIG. 18A

, the rear end (right end in

FIG. 18A

) of oil filter

35

is inserted to the inside of microwave oven

1

through bottom hole

67

. Thereafter, the front end of oil filter

35

is moved upward so that the oil filter

35

as a whole is inserted to the inside of microwave oven (see FIG.

18

B). At this time, oil filter

35

is fitted in step guides

69

. However, it is a little displaced backward (to the right in

FIG. 18A

) from the final position of attachment. Thus, oil filter

35

is moved from this state to the direction of the arrow Y, and the attachment of oil filter

35

is completed as shown in FIG.

18

C.

The manner of control by control circuit

65

of microwave oven

1

will be described in the following.

In microwave oven

1

, the number of rotation of hood fan

8

can be adjusted in two steps, by control panel

51

. Of these two different numbers of rotation, the larger number will be referred to as “High” and the smaller number will be referred to as “Low”. Corresponding keys are provided on control panel

51

. In the following, these keys will be referred to as High key and Low key.

In microwave oven

1

, the value of current to be supplied to fan motor

44

can be adjusted by control circuit

65

in three steps. The three current values will be referred to as “high current”, “middle current” and “low current”, from the higher one. When the current value supplied to fan motor

44

changes, the number of rotation of hood fan

8

, that is, the speed of rotation of hood fan

8

also changes accordingly. The speed of rotation of hood fan

8

when the current value supplied to fan motor

44

is “high current”, “middle current” or “low current” will be referred to as “high speed”, “middle speed” or “low speed”, respectively.

In microwave oven

1

, the High key and Low key mentioned above and the speed of rotation of hood fan

8

correspond as shown in Table 1, respectively.

TABLE 1

Hood Fan

Hood Fan Manner of Setting

Speed of

Back-

Up-

Rotation

Front-Setting

Setting

Setting

High speed

High key

High key

Middle speed

High key

Low key

Low key

Low speed

Low key

In Table 1, the manner of correspondence between respective keys and the rotation speeds differ dependent on the manner of setting of hood fan

8

. More specifically, when the fan is in front-setting, the High key corresponds to the middle speed and the Low key corresponds to the low speed. When the hood is in back-setting or up-setting, the High key corresponds to the high speed and the Low key corresponds to the middle speed. More specifically, in microwave oven

1

, hood fan

8

is rotated at any number of rotation within the prescribed range. The prescribed range refers to the number of rotation corresponding to the low to middle speed when the fan is in front-setting, and it refers to the number of rotation corresponding to the middle to high speed when the hood is in back-setting or up-setting. Namely, the prescribed range is set dependent on the manner of setting of the hood fan.

When power is applied from an AC power supply

55

to microwave oven

1

, control circuit

65

executes the process of setting rotation speed. In the process of setting rotation speed, control circuit

65

asks the user to input the manner of setting of hood fan

8

. In accordance with the manner of setting of hood fan

8

, control circuit

65

sets the correspondence between the High key and the Low key and the speed of rotation of hood fan

8

, as shown in Table 1. The process of setting rotation speed will be described in detail, with reference to FIG.

19

.

When power is applied from AC power supply

55

to microwave oven

1

, control circuit

65

displays, in step S

1

, a message asking the user to input the manner of setting of hood fan

8

, on a display unit of control panel

51

, and the flow proceeds to the step S

2

. The manner of display here may be associated with ten keys “1”, “2” and “3”, which are originally provided for inputting heating time and the like, adapted to select front-setting, back-setting and up-setting, respectively, asking the user to press either one of these three keys.

In step S

2

, control circuit

65

determines whether the manner of setting input by the user in step S

1

is the front-setting. If it is determined to be front-setting, the flow proceeds to S

4

, and otherwise, that is, when the setting is determined to be back-setting or up-setting, the flow proceeds to S

3

. In step S

2

, whether the setting is front-setting or not is determined. Therefore, the display in step S

1

may ask the user to answer whether the setting is front-setting or not.

In step S

3

, control circuit

65

sets High key to correspond to the high speed and Low key to correspond to the middle speed, sets the cover

7

to be kept closed even when hoof fan

8

is operated, and ends the process. In this case, cover

7

is opened/closed corresponding to the operation of fan

34

.

In step S

4

, control circuit

65

sets the High key and the Low key to correspond to the middle and low speeds, respectively, sets the cover

7

to be opened/closed in accordance with the operation of hood fan

8

, and ends the processing. In this case, cover

7

is opened/closed corresponding to the operations of hood fan

8

and fan

34

.

In microwave oven

1

, it is possible for the user to set the manner of operation of hood fan

8

to a desired manner, by pressing the High key or the Low key. By such a setting, when strong operation of hood fan

8

is desired, the High key may be pressed, and when moderate operation of hood fan

8

is desired, the user may press the Low key, in each manner of setting.

In the process of setting rotation speed described above, when the fan is in front-setting, the speed of rotation of hood fan

8

corresponding to each key is set slower than in other setting manner. More specifically, if the hood is in front-setting, the range of the number of rotation of hood fan

8

is shifted to smaller number side, than in other manner of setting. In microwave oven

1

, when hood fan

8

is in the front-setting, the direction of exhaustion from hood fan

8

is to the room, where the microwave oven

1

is installed. When the hood fan is in other setting, that is, when it is in the back-setting or the up-setting, the direction of exhaustion from hood fan

8

is outside the room where microwave oven

1

is installed.

Therefore, in the process of setting rotation speed, the number of rotation of hood fan

8

is made smaller when the direction of exhaustion from hood fan

8

is to the room where microwave oven

1

is installed, than when the direction is to the outside of the room. Generally, when the direction of exhaustion of hood fan

8

is into the room, noise generation is more likely as the hood fan

8

operates. This is because a louver is provided at outlet

2

to turn the direction of exhaustion upward, and the air fed from hood fan

8

is intercepted by the louver.

Microwave oven

1

is adapted such that when the noise is not tolerable for the user, the number of rotation of hood fan

8

is made lower to reduce noise, by executing the process of setting rotation speed.

In the conventional microwave oven installed at a high place, the charcoal air filter is provided in front of the fan which corresponds to hood fan

8

. More specifically, it has been positioned between hood fan

8

and outlet

2

in microwave oven

1

. In the microwave oven

1

of the present invention, the charcoal air filter

36

is supported and positioned near bottom hole

67

together with oil filter

35

. Therefore, operations at the time of maintenance such as attachment and detachment of these filters to microwave oven

1

can be facilitated, and the noise at the time of exhaustion by hood fan

8

in front-setting is reduced.

Here, reduction of noise of hood fan

8

in front-setting will be described in detail. Table 2 represents the amount of air (amount of ventilation) and the magnitude of exhaustion noise of respective manners of setting. In Table 2, the amount of air represents the amount of ventilation through the outlet when hood fan

8

is in operation, in CFM (Cubic Feet per Minutes [Ft

3

/min]) unit. In this case, the outlet refers to the portion opposing to outlet opening

8

A. Namely, in front-setting, it means outlet

2

, and in up-setting, it means the upper outlet

27

.

In Table 2 “vicinity of bottom hole” means that charcoal air filter

36

is provided near the bottom hole

67

together with oil filter

35

, as in the present embodiment. “In the vicinity of outlet” means that the charcoal air filter is placed between hood fan

8

and outlet

2

as in a conventional microwave oven.

TABLE 2

Front-Setting

Hood Fan

In the

In the

Speed of

vicinity of

vicinity of

Rotation

bottom hole

outlet

Back-Setting

Up-Setting

Amount of

230

170

300

300

Air (/CFM)

Exhaustion

65

62

59

56

Noise (dB)

Referring to Table 2, when the hood fan is in front-setting, the exhaustion noise is larger, though the amount of air is smaller as compared with other manner of setting. This is because of the existence of louver, as described above. When charcoal air filter

36

is provided in the vicinity of bottom hole

67

as in the present embodiment, the amount of air is increased by about 35%, that is, 65 CFM, than the conventional microwave oven, with comparable exhaustion noise.

In some cases, the user may wish to increase the power of exhaustion by hood fan

8

regardless of the large noise, with the direction of exhaustion of hood fan

8

being set toward that room. To meet such a demand by the user, microwave oven

1

is adjusted to attain the number of rotation of hood fan

8

corresponding to the High key and the Low key comparable to those in the case of back-setting or up-setting, by a prescribed operation through control panel

51

even when the hood fan is in front-setting, as shown in Table 3.

TABLE 3

Hood Fan

Hood Fan Manner of Setting

Speed of

Back-

Up-

Rotation

Front-Setting

Setting

Setting

High speed

High key

High key

High key

Middle speed

Low key

Low key

Low key

Low speed

In the present embodiment described above, means for driving the fan is provided by a fan motor

44

driving hood fan

8

and the control circuit

65

controlling the number of rotation of hood fan

8

by controlling the current value supplied to fan motor

44

. Further, hood fan may be attached in such manners as described with reference to

FIGS. 8

to

10

, and therefore it can be seen that the fan may be set in any of the plurality of manners of setting with different directions of air feed.

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.

Number	Name	Date
4115678	Tachikawa et al.	Sep 1978
4143646	Sampsel	Mar 1979
4886046	Welch	Dec 1989
6093922	Kim	Jul 2000
6097000	Frasnetti et al.	Aug 2000

Heat cooking device allowing control of fan rotation number

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (5)