Patent Grant
9119234
This application a 371 application of PCT/JP2011/001688 having an international filing date of Mar. 23, 2011, which claims priority to JP2010-066065 filed Mar. 23, 2010, the entire contents of which are incorporated herein by reference.
The present invention relates to microwave heating apparatuses for heating objects to be heated within heating chambers, through microwave, and more particularly, relates to drawer type heating apparatuses which make it possible to take out objects to be heated within heating chambers to the outside of the heating chambers, by pulling out an openable door.
As conventional drawer type heating apparatuses, there have been suggested various heating apparatuses relating to pull-out mechanisms, placement of heating means, and the like (refer to Patent Literature 1, for example).
Ordinary microwave heating apparatuses employ hinge couplings, as mechanisms for opening and closing openable doors and such openable doors are of turning types. In microwave heating apparatuses having such turning-type openable doors, there have been suggested structures which provide, in an openable door, a rectangular plate-shaped choke portion (a radio-wave transmission suppression portion) facing the inner wall surfaces of a heating chamber, in order to suppress leakages of microwaves supplied to the heating chamber for housing objects to be heated, through the openable door (refer to Patent Literature 2, for example).
Further, there have been suggested methods of determining states of thawing of objects to be heated within a heating chamber, by detecting reflected electric power returning from the heating chamber while varying the frequency of microwaves supplied to the heating chamber (refer to Patent Literature 3, for example).
In conventional drawer type heating apparatuses as disclosed in Patent Literature 1 as described, in order to suppress leakages of microwaves supplied to the inside of the heating chamber through the openable door, the mechanism for suppressing radio-wave transmission has been formed in a flange portion formed to protrude outwardly from the peripheral edge of the opening portion of the heating chamber and in the outer peripheral portion of the openable door which is faced to the flange portion. Accordingly, the openable door has been required to have a surface which faces the flange portion formed outwardly from the peripheral edge of the opening portion of the heating chamber and, therefore, the openable door has been structured to have a larger facing area, in comparison with the opening area of the heating chamber, in order to enclose microwaves within the heating space.
The conventional microwave heating apparatus disclosed in Patent Literature 2 is structured to be provided with the turning-type openable door using the hinge mechanism, wherein there is illustrated an example where a rectangular plate-shaped filter plate is orthogonally folded over its peripheral edge, and slits are formed in the folded area to form the choke portion, as a mechanism for suppressing radio-wave transmission. The choke portion is structured such that it is introduced within the heating chamber and is placed proximally to the wall surfaces of the heating chamber, when the turning-type openable door is closed. Accordingly, the openable door for forming the heating space within the heating chamber can be structured to have only a slightly larger area than the area of the opening portion of the heating chamber. Therefore, in the conventional microwave heating apparatus disclosed in Patent Literature 2, the openable door can be made to have a smaller size, in comparison with the opening portion of the heating chamber.
As described above, in the conventional microwave heating apparatus disclosed in Patent Literature 2, the turning-type openable door is provided with the choke portion with the slits having a length equal to the quarter-wavelength of radio waves, such that the choke portion is intruded in the heating chamber. Accordingly, it is necessarily necessary that the choke portion provided in the openable door is structured to have a thickness equal to or more than at least the quarter-wavelength of radio waves in the direction toward the heating chamber. In Patent Literature 2, the choke portion provided in the openable door is faced to the inner wall surfaces of the rectangular opening portion of the heating chamber, such that its four side portions are faced to the side portions of the heating chamber. Further, in the turning-type openable door adapted such that the choke portion having such a thickness is faced to the inner wall surfaces of the heating chamber, it is necessarily necessary that there is a larger gap between the choke portion and the heating chamber inner wall surface along the opening side along which the choke portion in the openable door comes to face the inner wall surface of the heating chamber opening portion, at last, in comparison with those along the other sides of the opening. Further, its four corner portions are faced to the corner portions of the heating chamber. At these corner portions, between the surfaces facing each other, there are gaps which are not the same as the gaps at the other portions. Namely, in the peripheral edge portions at which the heating chamber faces the choke portion of the openable door, the gaps between the corner portions facing each other are larger than the gaps between the straight portions facing each other.
Accordingly, the choke portion as the radio-wave transmission suppression mechanism has had the problem that it can not exert its radio-wave transmission suppression function at its corner portions. As described above, in such microwave heating apparatuses provided with turning-type openable doors, the inner wall surfaces of the opening portion of the heating chamber and the facing surfaces of the choke portion in the openable door are faced to each other, such that the interval between the inner wall surfaces and the facing surfaces is not constant over the entire outer peripheral portion, which has prevented reliable radio-wave transmission suppression effects from being expected.
The present invention is made in order to overcome the conventional problems described and aims at providing a drawer type heating apparatus which is provided with a radio-wave transmission suppression mechanism with excellent reliability between an openable door and inner wall surfaces of a heating chamber, thereby eliminating the necessity of structuring the openable door to be larger than the opening surface of the heating chamber and thus enabling compactification in the drawer type heating apparatus.
A drawer type heating apparatus in a first aspect of the present invention comprises a microwave radiation portion adapted to radiate microwaves within a heating space in which an object to be heated is placed; and
a heating chamber structural member adapted to enclose microwaves radiated within the heating space; wherein
the heating chamber structural member includes
a heating case having an opening portion formed from a curved surface, and
an openable door which is adapted to be moved in a pull-out manner with respect to the heating case for opening and closing the opening portion in the heating case and includes a radio-wave transmission suppression portion faced to an inner wall surface of the opening portion in the heating case,
the radio-wave transmission suppression portion is placed such that there is a predetermined gap between the radio-wave transmission suppression portion and an entire periphery of the inner wall surface of the opening portion in the heating case, in a state where the openable door is closed, and
the radio-wave transmission suppression portion includes a first radio-wave-propagation-direction suppression-area comprising a surface with a plurality of steps, and a second radio-wave-propagation-direction suppression-area comprising suppression protruding portions which are periodically formed and placed in such a way as to face the first radio-wave-propagation-direction suppression-area with a predetermined interval interposed.
In the drawer type heating apparatus having aforementioned structure in the first aspect of the present invention, the inner wall surface of the heating space at its opening portion is formed from a curved surface and thus has no corner portion. This can provide a substantially constant gap formed by the radio-wave transmission suppression portion and the inner wall surface of the opening portion, over the entire periphery. This enables the radio-wave transmission suppression portion provided in the drawer type openable door to certainly exert its function, over the entire periphery. This can provide a radio-wave transmission suppression mechanism with excellent reliability at the portion where the openable door faces the inner wall surface of the heating case. This can provide a drawer type heating apparatus including a compact openable door.
In a second aspect of the present invention, in the drawer type heating apparatus in the first aspect, the openable door includes a base plate having the first radio-wave-propagation-direction suppression-area having the plurality of steps formed through drawing processing, and a suppression plate having the second radio-wave-propagation-direction suppression-area in which the suppression protruding portions are periodically formed.
With the drawer type heating apparatus having the structure in the second aspect of the present invention, it is possible to create a space having an infinite impedance, between the first radio-wave-propagation-direction suppression-area in the base plate and the second radio-wave-propagation-direction suppression-area in the suppression plate, in order to enable the radio-wave transmission suppression portion to exert its function. By providing the first radio-wave-propagation-direction suppression-area in the base plate and the second radio-wave-propagation-direction suppression-area in the suppression plate and by making the gap between the areas have a space structure varied in a plurality of steps, the value of the characteristic impedance created by the first radio-wave-propagation-direction suppression-area in the root-side step in the suppression plate faced to the base plate having the plural-step structure is made larger than the value of the characteristic impedance created by the second radio-wave-propagation-direction suppression-area in the tip-end side step. As a result, due to an impedance transformation effect, it is possible to structure the radio-wave transmission suppression portion such that the space forming it has a length sufficiently shorter than the quarter-wavelength of transmitted waves. This enables the formation of the openable door to be compactified in the thick-wise direction. The openable door having such a structure can be formed such that its area which faces the inner wall surface of the opening portion of the heating case is compactified. Thus, the openable door can be made to have a structure which is light-weighted and compactified in its entirety.
In a third aspect of the present invention, in the drawer type heating apparatus in the second aspect, the openable door includes a supporting portion secured to a heating-space side of the openable door through the base plate and the suppression plate, and the supporting portion is adapted to hold a housing container on which the object to be heated is placed, and
the heating case includes a guide portion which is secured to an inner wall surface of the heating case and is adapted to engage with a portion of the supporting portion to define an area within which the supporting portion is movable.
The drawer type heating apparatus having the structure in the third aspect of the present invention has a structure with excellent reliability, since the supporting portion is secured to the openable door secured to have a high strength. Further, the drawer type heating apparatus is adapted to enable the openable door to be largely pulled out, since the guide portion defines displacements of the supporting portion in the upward and downward direction.
In a fourth aspect of the present invention, in the drawer type heating apparatus in the aforementioned third aspect, the drawer type heating apparatus further comprises a microwave generating portion for supplying microwaves to an inside of the heating space, and
a microwave radiation portion adapted to radiate microwaves from the microwave generating portion, within the heating space,
wherein the microwave radiation portion is provided at a position on a wall surface of the heating case which is faced to a center of an area which specifies a housing position in the housing container within the heating space.
With the drawer type heating apparatus having the structure in the fourth aspect of the present invention, microwaves are directly incident to the object to be heated, which can increase the amount of losses in the object to be heated and thus, can reduce the amount of energy of microwaves propagating over the entire heating space, thereby suppressing unnecessary heat generation and unnecessary occurrences of sparks, in the housing container housed in the heating space, the supporting portion or the guide portion.
In a fifth aspect of the present invention, in the drawer type heating apparatus in the fourth aspect, the microwave generating portion includes an electric-power detection portion adapted to detect at least reflected microwave electric power, out of supplied microwave electric power supplied to the heating space, and reflected microwave electric power reflected from the heating space, and
there is provided a control portion which is adapted to control an oscillating frequency of the microwave generating portion, based on a signal indicative of the reflected microwave electric power.
With the drawer type heating apparatus having the aforementioned structure in the fifth aspect of the present invention, at the beginning of start of heating, the frequency can be caused to sweep a specified range to determine an oscillating frequency which minimizes the reflected microwave electric power, this determined oscillating frequency can be selected as an operating frequency for heating, and the heating is continued, which enables electric power generated from the microwave generating portion to be supplied with highest efficiency. With the drawer type heating apparatus having the structure in the fifth aspect of the present invention, it is possible to utilize, as the microwave generating portion, one capable of generating smaller electric power, which can facilitate compactification of the entire heating apparatus.
In a sixth aspect of the present invention, in the drawer type heating apparatus in the fourth aspect, the drawer type heating apparatus further comprises a coaxial transmission line, as a transmission line for transmitting an output from the microwave generating portion to the microwave radiation portion.
With the drawer type heating apparatus having the structure in the sixth aspect of the present invention, it is possible to reduce the amount of microwave electric power reflected to the microwave generating portion, by utilizing the amount of transmission loss in the coaxial transmission line. This can suppress heat generation from the microwave generating portion, thereby ensuring reliable performance. With this structure, it is possible to eliminate an isolator as a component for taking countermeasures against reflected electric power, as those which have been generally employed.
In a seventh aspect of the present invention, in the drawer type heating apparatus in the fourth aspect, the microwave radiation portion comprises a patch antenna.
With the drawer type heating apparatus having the structure in the seventh aspect of the present invention, it is possible to place the antenna extremely close to the inner wall surface of the heating space, which enables providing a larger free space within the heating space.
In an eighth aspect of the present invention, in the drawer type heating apparatus in the fourth aspect, the microwave radiation portion comprises an antenna adapted to perform circularly-polarized wave radiation.
With the drawer type heating apparatus having the structure in the eighth aspect of the present invention, it is possible to supply two outputs from the microwave generating portion to a single antenna while providing a phase difference of 90 degrees therebetween, thereby realizing circularly-polarized wave radiation in the heating space. Therefore, the space occupied by the antenna within the heating space can be a substantially equal space to that of a patch antenna structure, and circularly-polarized waves can be directly incident to the object to be heated, which can facilitate heating of the object to be heated, and also, can further reduce the amount of energy of microwaves propagating within the heating space.
According to the present invention, it is possible to provide a drawer type heating apparatus having a compact structure which is capable of certainly preventing leakages of radio waves through an openable door and is capable of eliminating the necessity of forming the openable door to be larger than the opening surface of a heating chamber.
Hereinafter, with reference to the accompanying drawings, there will be described preferred embodiments of a drawer type heating apparatus according to the present invention. Note that, in the following embodiments, drawer type heating apparatuses will be described with respect to examples where drawer type microwave heating apparatuses are structured solely such that they include an openable door movable in the horizontal direction for opening and closing a heating space. However, the drawer type heating apparatus according to the present invention is not limited to the structures of the microwave heating apparatuses which will be described in the embodiments and can be also applied to structures of microwave heating apparatuses which are mounted in drawer portions in system kitchens in cooking rooms or integrally incorporated in other apparatuses such as refrigerators and vending machines. Further, the present invention is not limited to concrete structures according to the following embodiments and includes heating apparatuses structured based on equivalent technical concepts.
The drawer type heating apparatus 10 according to the first embodiment illustrated in
The drawer type heating apparatus 10 according to the first embodiment has the heating space formed by the heating case 11 and the openable door 12 and, further, is adapted to enclose, within the heating space, microwaves radiated within the heating chamber. Namely, in the structure according to the first embodiment, the heating case 11 and the openable door 12 form a heating chamber structural member. The heating case 11 forms the inner wall surfaces of the main body in the drawer type heating apparatus 10 and is made of a metal material. The openable door 12 is adapted to be movable in the horizontal direction with respect to the heating case 11 to make it possible to take out an object to be heated which is housed within the heating space, and has the function of opening and closing the heating space.
Further, the drawer type heating apparatus 10 according to the first embodiment is provided with a microwave generating portion 13 for generating microwaves, a microwave radiation portion 14 as an antenna for radiating microwaves within the heating space, a coaxial transmission line 15 for transmitting microwaves generated from the microwave generating portion 13 to the microwave radiation portion 14, a driving power supply 16 for the microwave generating portion 13, an electric-power detection portion 17 provided in an output side in the microwave generating portion 13, and a control portion 18 adapted to control operations of the microwave generating portion 13 and the driving power supply 16 for the microwave generating portion 13.
The openable door 12 is provided with a radio-wave transmission suppression portion 19. The radio-wave transmission suppression portion 19 is provided in the openable door 12, in its area which faces the inner wall surfaces of the opening portion of the heating case 11. The inner wall surfaces of the opening portion of the heating case 11, with which the radio-wave suppression portion 19 is internally in contact, are formed to have curved surfaces, at their four corner portions. On the other hand, the radio-wave transmission suppression portion 19 provided in the openable door 12 is also formed to have curved surfaces at its portions which face the four corner portions of the opening portion of the heating case 11, and thus the radio-wave transmission suppression portion 19 is structured to face the inner wall surfaces of the opening portion of the heating case 11 with a constant interval. As described above, the radio-wave transmission suppression portion 19 is formed in the openable door 12 in its heating-space side, such that there is a constant interval between the entire periphery of the radio-wave transmission suppression portion 19 and the inner wall surfaces of the opening portion of the heating case 11.
Further, a supporting portion 21 made of a metal material is secured to the openable door 12 in its heating-space side. The supporting portion 21 supports a housing container 20 on and in which an object to be heated is housed and placed, at the bottom surface thereof. The supporting portion 21 has a frame shape having two supporting members secured to the openable door 12 at left and right positions on the heating-space side. The supporting members in the left and right sides are coupled to each other through a coupling bar 22 near the rear surface of the heating space (in the left side of the heating space in
Further, referring to
The openable door 12 is structured to include a door portion 12a provided with a handle, and a door body portion 12b formed integrally with the door portion 12a. The door portion 12a and the door body portion 12b are made of a resin material. The radio-wave transmission suppression portion 19 and the supporting portion 21 are concurrently secured to the door body portion 12b, through the screw assembling (see
The supporting members in the opposite sides in the supporting portion 21 are coupled to each other, at their other ends (their rear-surface-side end portions), through the coupling portion 22 made of a resin material, with a predetermined interval. A roller 23 for smoothly moving the openable door 12 is rotatably mounted to the supporting members, in front of the position to which the coupling portion 22 is secured.
On the left and right wall surfaces of the heating case 11 forming the heating space within the main body, there are provided guide portions 24. The guide portions 24 are provided with rails, such that the roller 23 provided in the supporting portion 21 is fitted to the rails and is guided thereby. The rails in the guide portions 24 are provided with inclined surfaces 24a which are formed by inclining, downwardly, their end portions closer to the rear surface of the heating space (in the left side in
Further, a protruding portion 26 is formed in the coupling portion 22 provided in the supporting portion 21. When the openable door 12 is in the closed state, the protruding portion 26 is penetrated through an opening formed in the rear-surface wall of the heating space to press a switch 27. When the openable door 12 is closed, the protruding portion 26 pushes the switch 27, which causes the switch 27 to detect that the openable door 12 is being in the closed state and to input a signal indicative of the detection to the control portion 18.
On the other hand, there is provided a stopper 25 for stopping the movement of the roller 23, near the opening of the heating case 11, such that the openable door 12 is stopped at a predetermined position, when the openable door 12 has been pulled out in the horizontal direction from the heating chamber 11 and thus the heating space is in an opened state (see
As illustrated in
On the other hand, the suppression plate 31 is folded such that its outer peripheral portion faces the inner wall surfaces of the opening portion of the heating case 11. The suppression plate 31 has a plurality of cutout portions 35 which are periodically formed in its outer peripheral portion facing the inner wall surfaces of the opening portion of the heating case 11, and these cutout portions 35 form an area as a second radio-wave-propagation-direction suppression-area 34B. In the radio-wave-propagation-direction suppression-area 34B in the suppression plate 31, there are periodically arranged a plurality of suppression protruding portions 31 a having a substantially-T shape, which are formed from the cutout portions 35.
Further, the second radio-wave-propagation-direction suppression-area 34B at the outer peripheral portion of the suppression plate 31 is covered with a protection cover 32 made of a low dielectric-loss dielectric material, in order to prevent intrusions of foreign substances into the radio-wave transmission suppression portion 19.
As illustrated in
The screws securing the supporting members in the supporting portion 21 to the openable door 12 are screwed into the door body portion 12b in the openable door 12, by being penetrated through assembling holes 33 formed in the heating-space side of the suppression plate 31 and through assembling holes in the base plate 30. Since the supporting members in the supporting portion 21 are secured to the openable door 12 as described above, the base plate 30 and the suppression plate 31 are assembled and secured thereto, concurrently and integrally.
As illustrated in
The output of the microwave generating portion 13 is transmitted to the microwave radiation portion 14 through the coaxial transmission line 15 and is radiated within the heating space from the microwave radiation portion 14. As a result, an object to be heated 44 housed within the heating space is heated by microwaves.
In the drawer type heating apparatus according to the first embodiment, the microwave radiation portion 14 is constituted by a so-called patch antenna which utilizes an air layer. The microwave radiation portion 14 is provided on the upper surface wall of the heating case 11 and is placed at a position at the center of the heating space in the leftward and rightward directions and also in front of the center of the heating space in the forward and rearward directions. Further, regarding the position at which the microwave radiation portion 14 is placed with respect to the housing container 20 housed within the heating space, it is a position on the upper surface wall of the heating case 11 which faces the center position in an area specified as an area (a specified area) in which the object to be heated 44 should be placed. Further, the microwave radiation portion 14 is covered with an antenna cover 45 made of a low dielectric-loss material and is protected thereby (see
Next, there will be described heating operations in the drawer type heating apparatus having the structure described according to the first embodiment.
In an opened state where the openable door 12 has been pulled out from the heating case 11, the object to be heated 44 is placed within the specified area in the housing container 20. Then, the openable door 12 is closed. In this closed state, the coupling bar 22 presses the switch 27, thereby closing the contact point in the switch 27. Since the switch 27 is closed, the control portion 18 is supplied with electric power.
On receiving a heating start command and heating conditions for the object to be heated 44, which have been inputted to an operating portion (not illustrated), the control portion 18 operates the driving power supply 16, thereby starting an operation of the microwave generating portion 13.
The electric-power detection portion 17 placed in the output side of the microwave generating portion 13 is adapted to detect supplied microwave electric power supplied to the heating space, and reflected microwave electric power returning to the microwave generating portion 13 from the heating space. The control portion 18 causes the oscillating frequency to sweep a specified output-frequency range of the microwave generating portion 13 (for example, from 2400 MHz to 2500 MHz), at intervals of a predetermined frequency (for example, at intervals of 1 MHz), before actual heating for the object to be heated 44. Further, the control portion 18 extracts, from the electric power detection portion 17, a signal corresponding to the reflected microwave electric power at each oscillating frequency. Further, the control portion 18 extracts an oscillating frequency which minimizes the reflected microwave electric power. The microwave generating portion 13 sets the heating frequency at the extracted oscillating frequency and starts actual heating of the object to be heated 44, with a microwave output corresponding to the heating conditions having been inputted through the operating portion. In the actual heating, the control portion 18 controls the microwave output in such a way as to satisfy predetermined heating conditions and, also, stops the operation of the microwave generating portion 13 for completing the heating operation, when desired conditions (a temperature, a heating time, and the like) have been satisfied.
In the drawer type heating apparatus according to the first embodiment, the heating case 11 forming the heating space has curved-surface shapes at the four corner portions of its opening portion, and the radio-wave transmission suppression portion 19 in the openable door 12 which is faced to these corner portions of the opening portion is also formed to have the same curved surfaces. Therefore, the inner wall surfaces of the opening portion of the heating case 11 are adapted to be faced, over the entire periphery, to the radio-wave transmission suppression portion 19, at the constant distance. As described above, in the drawer type heating apparatus according to the first embodiment, the radio-wave transmission suppression portion 19 faces the inner wall surfaces of the opening portion of the heating case 11 at the constant distance, over its entire periphery, which allows the radio-wave transmission suppression portion 19 to certainly exert its functions, thereby preventing leakages of radio waves from the heating space.
Next, there will be described the functions and the structure of the radio-wave transmission suppression portion 19 which is provided between the openable door 12 and the heating case 11 forming the heating space within the drawer type heating apparatus according to the first embodiment.
In order to enable the radio-wave transmission suppression portion 19 to exert its function of suppressing radio-wave transmission, it is necessary to create an infinite impedance in the opening 36 between the first radio-wave-propagation-direction suppression-area 34A and the tip end of the second radio-wave-propagation-direction suppression-area 34B, by utilizing the space between the second radio-wave-propagation-direction suppression-area 34B at the outer peripheral portion of the suppression plate 31, and the first radio-wave-propagation-direction suppression-area 34A which is the drawing-processed portion in the base plate 30.
As illustrated in
Further, in the second radio-wave-propagation-direction suppression-area 34B in the suppression plate 31, the plurality of suppression protruding portions 31a with the substantially-T shape are periodically arranged with a constant pitch (P1). Each of these suppression protruding portions 31a is formed to have a smaller-width portion 31b with a width of W1, and a larger-width portion 31c with a width of W2 (W2>W1). Further, the smaller-width portion 31b has a length of L1, while the larger-width portion 31c has a length of L2. Here, these widths of the suppression protruding portions 31a are the lengths in the direction along the peripheral edge as the outer periphery of the suppression plate 31. Further, these lengths of the suppression protruding portions 31a are the lengths in the direction orthogonal to the direction along the peripheral edge of the suppression plate 31 (see
The suppression plate 31 having the suppression protruding portions 31a having the structure described is placed, such that the surfaces of the smaller-width portions 31b are faced to the surface 30a of the first step (the step closer to the center) in the two-stage-drawing-processed portion (the first radio-wave-propagation-direction suppression-area 34A) in the base plate 30, thereby forming the first suppression space. In this case, the gap dimension of the first suppression space is H1 (see
In the structure according to the first embodiment, the suppression plate 31 is folded such that its outer peripheral portion faces the inner wall surfaces of the opening portion of the heating case 11, thereby forming the second radio-wave-propagation-direction suppression-area 34B. In the drawer type heating apparatus according to the first embodiment, the second radio-wave-propagation-direction suppression-area 34B in the suppression plate 31, and the first radio-wave-propagation-direction suppression-area 34A which is the two-stages drawing-processed portion in the base plate 30 form the radio-wave transmission suppression portion 19.
As illustrated in
In the drawer type heating apparatus according to the first embodiment, the suppression plate 31 and the base plate 30 having the structures described are secured to the door body portion 12d in the openable door 12, by assembling the supporting portion 21 through screws. Therefore, the supporting portion 21 has a mechanically strong structure and thus has a structure capable of certainly holding the housing container 20.
Further, in the radio-wave transmission suppression portion 19 having the plurality of suppression spaces formed between the first radio-wave-propagation-direction suppression-area 34A in the base plate 30 and the second radio-wave-propagation-direction suppression-area 34B in the suppression plate 31, the suppression protruding portions 31a in the first radio-wave-propagation-direction suppression-area 34A in the suppression plate 31 can be made to have an I-shape. Namely, this corresponds to a case where, in the suppression protruding portions 31a having the T shape illustrated in
As described above, in the drawer type heating apparatus according to the first embodiment, the radio-wave-propagation-direction suppression-area 34B in the suppression plate 31 is formed from the periodic arrangement of the plurality of suppression protruding portions 31a which are separated from each other through the cutout portions 35, and also, each of the suppression protruding portions 31a is constituted by the smaller-width portion 31b (the width W1) and the larger-width portion 31c (the width W2> the width W0. As a result, the characteristic impedance determined based on the width W1 of the smaller-width portions 31b, and based on the dimension 1 between the smaller-width portions 31b which are the root portions of the suppression protruding portions 31a and the surface 30a of the first step portion in the base plate 30 (see
The structure of the drawer type heating apparatus according to the first embodiment has been described with respect to the case where the number of drawing stages for the base plate 30 for forming the radio-wave transmission suppression portion 19 is two. However, in the present invention, the base plate 30 in the radio-wave transmission suppression portion 19 is not limited to one having two stages, and it is also possible to employ multistage drawing processing with three or more stages for attaining suppression of radio-wave transmission.
As illustrated in
The suppression plate 131 having the suppression protruding portions 131a having the structure described is placed such that the surfaces of the smaller-width portions 131b are faced to the surface 130a of the first step in the three-stage-drawing-processed portion (the first radio-wave-propagation-direction suppression-area 34A) in the base plate 130, thereby forming the first suppression space. In this case, the gap dimension of the first suppression space is H11 (see
As described above, the radio-wave transmission suppression portion 119 is constituted by the first radio-wave-propagation-direction suppression-area 34A in the base plate 130 and the second radio-wave-propagation-direction suppression-area 34B in the suppression plate 131, which can provide a structure having a higher characteristic-impedance ratio. As described above, it is possible to create an infinite impedance in the opening 136 between the first radio-wave-propagation-direction suppression-area 34A and the tip end of the second radio-wave-propagation-direction suppression-area 34B. Therefore, the radio-wave transmission suppression portion 119 can be structured such that the space forming it has a length (see L10+L11+L12+L13 in
In the drawer type heating apparatus according to the first embodiment, the microwave radiation portion 14 is constituted by a patch antenna which utilizes an air layer. Due to the use of the patch antenna, it is possible to reduce, as much as possible, the space occupied by the microwave radiation portion 14, within the heating space formed by the heating case 11.
Further, in the drawer type heating apparatus according to the first embodiment, the coaxial transmission line 15 is used for microwave transmission between the microwave generating portion 13 and the microwave radiation portion 14. Due to the use of the coaxial transmission line 15, by utilizing the amount of transmission loss therein, it is possible to suppress the amount of microwave electric power returning to the microwave generating portion 13 to be equal to or less than a specified value, even when the supplied microwave electric power supplied to the heating space is reflected by 100%. For example, in the case where the coaxial transmission line 15 used therein has a transmission loss of 1.5 dB, with respect to the output electric power from the microwave generating portion 13, the reflected microwave electric power returning from the heating space and received by the microwave generating portion 13 is about 50% of the output electric power. As described above, by utilizing the transmission loss effect of the coaxial transmission line 15, it is possible to eliminate a protective component such as an isolator for protecting the microwave generating portion 13 from the reflected electric power, which enables compactification of the structure of the microwave generating portion 13.
Further, in the drawer type heating apparatus according to the first embodiment, the guide portions 24 are provided on the opposite side surfaces of the heating case 11 in order to determine the area in which the supporting portion 21 secured to the openable door 12 can move and, further, the guide portions 24 restrict the displacement of the supporting portion 21 in the upward and downward directions. This restricts the movement of the openable door 12 to which the supporting portion 21 is secured to fall within a predetermined movement range. Further, the openable door 12 can be largely pulled out, in the state where the supporting portion 21 is held on the rails in the guide portions 24.
Further, in the drawer type heating apparatus according to the first embodiment, the microwave radiation portion 14 for radiating microwaves within the heating space is placed at a position faced to the center of the area specifying the position at which the object to be heated 44 should be housed, in the housing container 20 within the heating space. Thus, the object to be heated 44 is placed in the specified area in the housing container 20, and microwaves are directly incident to the object to be heated 44 from above, which can increase the amount of microwave electric power absorbed by the object to be heated 44. This results in reduction of the amount of energy of microwaves propagating over the entire heating space, which can suppress unnecessary heat generation and unnecessary occurrences of sparks, in the housing container 20 housed in the heating space, the supporting portion 21 or the rails in the guide portions 24.
Next, there will be described a drawer type microwave heating apparatus as a drawer type heating apparatus according to a second embodiment of the present invention.
Further, the drawer type heating apparatus according to the second embodiment is different from the structure according to the first embodiment, in terms of the structures of a microwave radiation portion 51 and a microwave generating portion 52. But the other structures, particularly the structures of an openable door and a heating space, are substantially the same as those of the structure according to the first embodiment. Therefore, in the description about the second embodiment, components having the same structures as those of components in the drawer type heating apparatus according to the first embodiment will be designated by the same reference characters and will not be described herein.
In the drawer type heating apparatus according to the second embodiment, the microwave radiation portion 51 placed in the heating space is constituted by a microwave radiation portion 51 formed from an antenna adapted to perform circularly-polarized wave radiation, wherein respective lines connecting the center point to two feeding points are orthogonal to each other, and microwaves supplied to the respective feeding points have a phase difference of 90 degrees.
In the drawer type heating apparatus according to the second embodiment, the microwave generating portion 52 is structured to include a microwave oscillator 53, amplifiers 54 and 55 in two stages for amplifying the output of the microwave oscillator 53, an isolator 56 provided in the output of the amplifier 55 in the last stage, an electric-power detection portion 57 provided in the output of the isolator 56, and an electric-power divider 58 for dividing the output of the electric-power detection portion 57 into two parts and for creating a phase difference of 90 degrees. Further, in the microwave generating portion 52, there are provided transmission paths 59a and 59b which connect the respective outputs of the electric-power divider 58 to the respective feeding points in the microwave radiation portion 51 for extremely-shorter distances.
Further, in the drawer type heating apparatus according to the second embodiment, there is provided a control portion 60. Signals indicative of supplied microwave electric power supplied to the heating space and reflected microwave electric power reflected toward the isolator 56 from the heating space, which have been detected by the electric-power detector 57, are inputted to the control portion 60. The reflected microwave electric powers from the heating space are transmitted through the respective transmission paths 59a and 59b and are synthesized in electric power by the electric power divider 58.
The control portion 60 controls the generated frequency and the output electric power from the microwave generating portion 52. The method of control in the drawer type heating apparatus according to the second embodiment is the same as the control method described with respect to the drawer type heating apparatus according to the first embodiment, and therefore will not be described here.
In the drawer type heating apparatus according to the second embodiment, the microwave radiation portion 51 for radiating circularly-polarized waves is adapted to utilize an air layer similarly to in the first embodiment, and is formed from a circular plate. There are provided the two feeding portions at points spaced apart from the center of the circular plate by predetermined distances, and the straight lines connecting the respective feeding points to the center of the circular plate are orthogonal to each other.
As described above, in the drawer type heating apparatus according to the second embodiment, the microwave radiation portion 51 has an antenna structure for radiating circularly-polarized waves, so that the space occupied by the antenna within the heating space can be a substantially equal space to that of the patch antenna structure in the drawer type heating apparatus according to the first embodiment, which enables increase in the space for housing an object to be heated 44 within the heating space.
Further, in the drawer type heating apparatus according to the second embodiment, the microwave radiation portion 51 for radiating microwaves within the heating space is placed at a position faced to the center of the area specifying the position at which the object to be heated 44 should be housed, in the housing container 20 within the heating space. Thus, the object to be heated 44 is placed in the specified area in the housing container 20, and microwaves are directly incident to the object to be heated 44 from above, which can increase the amount of microwave electric power absorbed by the object to be heated 44. This results in reduction of the amount of energy of microwaves propagating over the entire heating space, which can suppress unnecessary heat generation and unnecessary occurrences of sparks, in the housing container 20 housed in the heating space, the supporting portion 21 or the rails in the guide portions 24.
Further, in order to ensure that microwaves supplied to the feeding points in the microwave radiation portion 51 have a phase difference of 90 degrees, it is preferable to employ extremely-short wiring between the electric-power divider 58 and the respective transmission paths 59a and 59b. For example, it is desirable to structure the microwave generating portion 52 such that it is mounted on the wall surface of the heating case 11 on which the microwave radiation portion 51 is placed. Accordingly, the drawer type heating apparatus according to the second embodiment does not employ a coaxial transmission line, as in the structure according to the first embodiment, and therefore, the microwave generating portion 52 is provided with the isolator 56 for inducing heat losses in the reflected microwave electric power having been reflected from the heating space and returning to the electric-power divider and for absorbing such heat losses.
Further, the structures of the drawer type heating apparatuses according to the first and second embodiments have been described with respect to examples where there is provided, on the rear-surface wall of the heating space, a switch for detecting states where objects to be heated have been housed in the heating space and the openable door 12 has been closed, but the present invention is not limited to this structure. For example, a switch for detecting states where the openable door 12 has been closed can be provided on the front-surface side wall surface in the heating space.
Further, the structures of the drawer type heating apparatuses according to the first and second embodiments have been described with respect to structures where the microwave radiation portion as an antenna is placed on the upper surface wall of the heating space, but the present invention is not limited to this structure. The microwave radiation portion can be provided on any of the wall surfaces. Also, a plurality of microwave radiation portions can be placed thereon.
As described above, the drawer type heating apparatus according to the present invention is structured such that the radio-wave transmission suppression portion provided in the drawer type openable door is placed in such a way as to face the inner wall surfaces of the opening portion of the heating space in which the object to be heated is housed, with a constant interval interposed therebetween. This allows the radio-wave transmission suppression portion to certainly exert its function, over its entire periphery. Accordingly, with the present invention, it is possible to structure the openable door such that its area which faces the opening area of the heating space is compactified, and also its length in the depthwise direction (the thickness) is smaller. The drawer type heating apparatus having the structure described according to the present invention is capable of realizing a heating space with a larger opening area with respect to the shape of the openable door, and the drawer type heating apparatus can be mounted in drawer portions in system kitchens in cooking rooms or mounted to other apparatuses such as refrigerators or vending machines through integral assembling.
With the drawer type heating apparatus according to the present invention, it is possible to realize a microwave heating apparatus with excellent safety and a reduced size and with a drawer type structure. Therefore, the drawer type heating apparatus can be mounted in drawer portions in system kitchens in cooking rooms or mounted to other apparatuses such as refrigerators or vending machines through integral assembling. Thus, the drawer type heating apparatus according to the present invention forms a heating apparatus with excellent general versatility.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-066065 | Mar 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/001688 | 3/23/2011 | WO | 00 | 9/19/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/118204 | 9/29/2011 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20130008894 A1 | Jan 2013 | US |
