JP2006196336A5 - - Google Patents

Description

Microwave heating device

  The present invention relates to a microwave heating apparatus that dielectrically heats an object to be heated.

  Conventionally, in a microwave oven, which is a typical example of a microwave heating apparatus, a microwave radiated from a magnetron is transmitted to a heating chamber through a waveguide to form a standing wave in the heating chamber. The heated object generates heat according to the component and the dielectric loss of the heated object. The absorbed power P [W / m3] per unit volume of the object to be heated is the electric field strength E [V / m] applied, the frequency f [Hz], and the relative dielectric constant (dielectric constant of the object to be heated). Εr and dielectric loss tangent tan δ are expressed by the following equation (where εr · tan δ corresponds to dielectric loss).

P = (5/9) εr · tan δ · f · E2 × 10 −10 [W / m 3]
In addition, in the microwave oven, the size of the heating chamber that accommodates the object to be heated is generally about 30 to 40 cm in width and depth, and about 20 cm in height. On the other hand, the wavelength of the microwave used is about 12 cm, and it resonates in the heating chamber and becomes a standing wave. Therefore, a strong electric field distribution is inevitably generated, and further, the shape of the object to be heated and the influence of its physical characteristics are affected. Local heating may occur by acting synergistically. As a method of suppressing this local heating, a so-called turntable that changes the relative position to the electric field distribution by rotating the object to be heated, a so-called stirrer system that changes the electric field distribution by stirring the microwave, and a rotating antenna There is a method using a method. In these cases, although there is some effect in averaging the heating of the parts equidistant from the center of rotation, it is still difficult to make it completely uniform.

  In particular, in the thawing of frozen foods, the area where the ice melts and becomes water rapidly increases the dielectric loss, and the heating energy is concentrated, so that the temperature rise rate is faster than the surroundings. In other words, while the heating of the ice portion is slow, the temperature difference tends to increase more and more in the state where the heating of the ice melted portion is accelerated. Therefore, the local heating phenomenon appears prominently, and when it is severe, the boiled portion and the unthawed portion may coexist. In order to prevent this, in the current microwave oven thawing, the output of the microwave is intentionally lowered (for example, even if the rated high-frequency output is 1000 W, 300 W or less when thawing), or a time during which no microwave is emitted is provided during heating (intermittent operation) ) Etc., the workmanship is improved by waiting for the temperature to be averaged due to heat conduction inside the food. In other words, local heating is avoided by intentionally extending the heating time.

On the other hand, there is one that pays attention to the fact that the microwave distribution changes by supplying a dielectric to the space where the microwave is transmitted. One of them is a microwave heating apparatus in which one thin tube made of a dielectric is placed in a waveguide connected to the upper surface of the heating chamber, and a coolant (dielectric) is intermittently sent into the tube (for example, And Patent Document 1). The other is a microwave heating apparatus in which water (dielectric material) and air are circulated in one large container covering almost the entire bottom surface of the heating chamber (see, for example, Patent Document 2).
Japanese Patent Publication No. 40-17195 Japanese Patent No. 3317227

  However, since the conventional microwave heating device controls the presence or absence of a dielectric in a certain region, there are at most two types of distribution: a microwave distribution when there is no dielectric and a microwave distribution when there is a dielectric. There are few options for distribution, and local heating may not be avoided depending on the type, shape, and position of the object to be heated.

  Moreover, in the thing of patent document 1, since the presence or absence of a refrigerant | coolant (dielectric material) is controlled only in a waveguide, it acts on the microwave in a waveguide especially, As a result, it transmits to a heating chamber from a waveguide. Although the microwave transmission efficiency can be changed, this is only changing the intensity of the entire microwave, and the effect of changing the positional relationship between the strong and weak microwaves in the heating chamber is not It is thought that there are few. This is because the distribution of microwaves in the heating chamber does not change unless the state in the heating chamber changes or the incident position of the microwaves in the heating chamber changes. That is, in Patent Document 1, although there is a change in the presence or absence of a refrigerant (dielectric material) in the waveguide, there is always no dielectric in the heating chamber, and the microwave incident position (waveguide and heating). This is because the connecting part of the chamber is also always constant.

  Moreover, in the thing of patent document 2, it is thought that the presence or absence of water is controlled in a heating chamber, and it fully acts on the microwave distribution in a heating chamber. However, a large amount of water that covers the entire bottom surface of the heating chamber is assumed, and the microwave does not reach the object to be heated unless it passes through the water. Therefore, when water is present, the water itself absorbs the microwave, and there is a concern that the ratio of the object to be heated that absorbs the microwave decreases. This is specifically described as a reduction in high-frequency output. What was 650 W when there is no water is 512 W when water is 70 g, and 446 W when water is 100 g. That is, the heating efficiency of the object to be heated is reduced by increasing the amount of water.

  The present invention solves the above-mentioned conventional problems, suppresses local heating peculiar to microwave heating without lowering the heating efficiency of the object to be heated, and achieves uniform heating of the object to be heated. An object of the present invention is to provide a microwave heating apparatus capable of improving the workmanship of the product.

  In order to solve the above-described conventional problems, the microwave heating apparatus of the present invention has a plurality of passages arranged in a microwave space in which microwaves radiated from microwave radiating means can propagate, and the plurality of passages are connected to the plurality of passages. Incoming and outgoing of the dielectric is controlled by the control means, and the microwave distribution is changed by changing the dielectric constant distribution state of the microwave space depending on the presence or absence of the dielectric in the plurality of passages.

  As a result, the microwave distribution in the heating chamber included in the microwave space can be changed, and the electric field distribution of the microwave around the object to be heated stored in the heating chamber is changed. Local heating as in the case of heating can be suppressed, the object to be heated can be heated uniformly, and the workmanship after heating can be improved.

  The microwave heating apparatus of the present invention can improve the quality after heating by uniformizing the heating of the object to be heated.

  1st invention can accommodate a to-be-heated object provided in at least one part of the microwave radiation means, the microwave space which the microwave radiated | emitted from the said microwave radiation means can propagate, and the said microwave space A heating chamber, a plurality of passages arranged in the microwave space, and a control means for controlling the entry and exit of the dielectric into and from the plurality of passages, and the presence or absence of the dielectric in the plurality of passages. The microwave heating apparatus changes the microwave distribution by changing the dielectric constant distribution state of the microwave space. As a result, the microwave distribution in the heating chamber included in the microwave space can be changed, and the electric field distribution of the microwave around the object to be heated stored in the heating chamber is changed. Local heating as in the case of heating can be suppressed, the object to be heated can be heated uniformly, and the workmanship after heating can be improved. In other words, if there is only one passage, there are only two microwave distributions, whether there is a dielectric or not, but if there are two passages, there are four ways (if there is no dielectric in any passage) , If there is a dielectric in only one of the passages, or if there is a dielectric in any of the passages), similarly, if there are three passages, the number of the eight microwave distributions and the number of passages If the number is four, the number of microwave distributions that can be selected every time the number of passages is increased, such as 16 microwave distributions, can be dramatically increased. Therefore, it is possible to switch to an arbitrary microwave distribution by controlling the presence or absence of a dielectric. As a result, the object to be heated can be heated more evenly, and in particular, it is possible to improve the workmanship when thawing a frozen product and general warming (reheating).

  According to a second aspect of the invention, in particular, in the first aspect of the invention, the microwave radiating means is configured to radiate microwaves from a radiating antenna that rotates about an axis, and the passages are arranged in at least two symmetrical positions when viewed from the axis. By doing so, the microwave distribution when the dielectric is present only in the first path and the microwave distribution when the dielectric is present only in the other path symmetrical to the first path It can be a distribution. For example, if there are two passages, the microwave distribution in the case where there is a dielectric only in the first passage causes local concentration at the portion (first portion) where the microwave distribution is mutated in either direction with respect to the axis. The distribution of microwaves in the presence of a dielectric only in the second path would cause local concentration at the part (second part) mutated in the opposite direction to the axis. A distribution can be produced.

In particular, in the second aspect of the invention, the heating chamber has a door on the front, the shaft is positioned substantially at the lower center of the heating chamber, and when viewed from the front, at least the first passage on the left of the shaft and the right of the shaft. By arranging the second passage, it is possible to obtain a symmetric microwave distribution around the axis when there is a dielectric only in the first passage and when there is a dielectric only in the second passage. it can. For example, it is possible to cause a distribution such as symmetry. In the case of a general microwave oven as a microwave heating device, there are many cases where the shape of a food that is a typical object to be heated is flat, or a plurality of foods are heated at the same time. In many cases, it is desirable that the left and right sides be uniform. In such a case, a uniform heating distribution can be expected.

In particular, in the second aspect of the invention, the heating chamber has a door on the front surface, the shaft is positioned substantially in the center of the lower portion of the heating chamber, and when viewed from the front, at least the first passage in front of the shaft and the rear of the shaft. By arranging the second passage, it is possible to obtain a symmetric microwave distribution around the axis when there is a dielectric only in the first passage and when there is a dielectric only in the second passage. it can. For example, it is possible to cause a distribution such as anteroposterior symmetry. In the case of a general microwave oven as a microwave heating device, there are many cases where the shape of a food that is a typical object to be heated is flat, or a plurality of foods are heated at the same time. In many cases, it is desired to be uniform before and after. In such a case, a uniform heating distribution can be expected.

In a third aspect of the invention, in particular, in the first aspect of the invention, the microwave radiating means radiates microwaves from a radiating antenna that rotates about an axis, and passages are provided at least at two locations that are different from each other when viewed from the axis. By arranging, the microwave distribution when there is a dielectric only in the first passage, and the microwave distribution when there is a dielectric only in another passage having a different distance from the axis from the first passage. The microwave distribution can be asymmetric with respect to the axis. For example, if there are two passages and the microwave distribution in the case where there is a dielectric only in the first passage is a distribution that causes local concentration at a specific part on the axis, the second passage Is located at an equal distance from the shaft and at the same distance from the axis, both when there is a dielectric only in the second path and when there is a dielectric only in the first path Can easily cause local concentration. However, by arranging the second passage so that the distance from the axis is different from that of the first passage, the microwave distribution when there is a dielectric only in the second passage is an asymmetric distribution with respect to the axis, that is, There is a high possibility that a distribution that does not concentrate on a specific part on the axis or a distribution that concentrates on a different part on the axis can be obtained.

In particular, in the third aspect of the invention, the heating chamber has a door on the front surface, the shaft is positioned substantially at the lower center of the heating chamber, and the first passage and the first passage at least above the shaft as viewed from the front. By arranging the second passage further above the first passage, the first passage is close to the radiating antenna and the second passage is far from the radiating antenna. In general, it is known that the electric field attenuates as the distance from the radiating antenna increases, and the first path close to the radiating antenna is exposed to a stronger electric field, so that the microwaves when there is a dielectric It is assumed that the effect, i.e. the change in the microwave distribution, will be greater. Therefore, when there is a dielectric only in the second path compared to the microwave distribution without a dielectric, the microwave distribution is slightly changed, and there is a dielectric only in the first path. Can greatly change the distribution of microwaves.

In particular, in the third aspect of the invention, the heating chamber has a door on the front surface, the shaft is positioned at the approximate center of the lower portion of the heating chamber, and at least a first passage close to the center of the shaft and an outer side of the first passage. By arranging the second passage far from the center of the shaft, the same effect as in the sixth invention can be obtained.

According to a fourth aspect of the invention, in particular, in the first aspect of the invention, there is provided temperature detecting means for detecting the temperature of the object to be heated. By controlling, a microwave that suppresses uneven distribution by controlling the entry and exit of the dielectric into the passage if the unevenness increases while observing the temperature unevenness of the object to be heated from the detection signal of the temperature detecting means. The distribution can be changed. In addition, if the temperature unevenness is detected while sequentially switching the combination of the presence or absence of the dielectric in each passage, the combination that can minimize the temperature unevenness can be found. Can be reduced. In addition, if you know in advance what kind of heating distribution will depend on the combination of the presence or absence of dielectric in each passage, the dielectric should be adjusted so that there is a high possibility of canceling the temperature unevenness while detecting the temperature unevenness. It can be controlled frequently and can be heated while maintaining a state in which the temperature unevenness of the object to be heated is not generated so much from the beginning to the end.

According to a fifth aspect of the present invention, in the first aspect of the present invention, in the first aspect of the present invention, the control unit further includes a setting unit that can be set by the user. Thus, the microwave distribution can be changed according to the set contents so as to suppress the distribution unevenness. In particular, when the setting means is the menu setting of the operation key, the shape and material of the heated object may be specified to some extent if the key itself is like “milk”, “thawing” or “convenience store lunch”. Many. For example, `` milk '' has convection in the shape of a mug or cup, so it is better to heat the lower part, and `` thaw '' should be a flat shape, so the front and rear distribution should be better than the top and bottom distribution, In the case of a “convenience store lunch box”, it can be preliminarily estimated that the area of rice and side dishes should be balanced because the area is wide and the area is divided. Alternatively, since the total time is determined when the heating time is set, it is possible to determine in advance how many minutes should be distributed if the distribution is changed twice in the middle. Therefore, controlling the entry / exit of the dielectric material to / from the predetermined passage according to the setting contents has a certain effect for uniform heating.

In particular, in the first invention, the control means controls the entry and exit of the dielectric to and from the passage during the microwave heating, thereby heating the object to be heated with a constant microwave distribution until halfway, and going to the predetermined passage. After controlling the entry and exit of the dielectric, the object to be heated can be heated with a different microwave distribution. In particular, the power for controlling the entry / exit of the dielectric is much lower than the power required for microwave heating (eg, 1200 W) (10 W order). Is easy. In this case, since it is not necessary to interrupt the microwave heating when controlling the entry and exit of the dielectric, the microwave heating can be continued efficiently.

In particular, in the first invention, since the dielectric is made of water, the relative permittivity of water is as high as about 80, which is 80 times that of air 1. In general, the wavelength of the microwave propagating inside the dielectric is inversely proportional to the square root of the relative permittivity, so the wavelength is compressed to about 1/9 (≈ 1 / √80) inside the water. On the other hand, if the microwave wavelength is considered to be constant, only the region where water is present appears to be enlarged 9 times. Therefore, depending on the presence or absence of water and the location of water, the microwave space has the same action as if the shape of the microwave space is deformed, and the microwave distribution can be greatly changed. Water is easy to obtain, safe and easy to handle. With regard to controlling the flow of water into and out of passages, it is easy to use general-purpose parts such as pumps and valves, and pipes for transporting water in various fields have been put into practical use. Can be adopted.

In particular, in the first invention, since the passage is constituted by a resin tube, the passage can be easily made of a low-loss dielectric material. Further, since the shape has a degree of freedom, the shape and position of the dielectric disposed inside can be arbitrarily determined by optimal design.

In particular, in the first invention, the same effect as in the twelfth invention can be obtained by configuring the passage with glass.

In particular, in the first invention, since the dielectric discharged from the passage is circulated through the circulation means, the dielectric can be reused and there is no waste. It is possible to avoid the trouble of post-processing.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
1 to 13 show a microwave heating apparatus according to Embodiment 1 of the present invention.

  As shown in FIGS. 1 and 2, the microwave heating apparatus 1 according to the present embodiment includes a microwave radiating unit 11, a microwave space 9 in which microwaves radiated from the microwave radiating unit 11 can propagate, A front-opening box-shaped heating chamber 3 that is provided in at least a part of the microwave space 9 and can store the object to be heated 2, a plurality of passages 13 to 16 disposed in the microwave space 9, and a plurality of passages Control means 33 for controlling the entry / exit of dielectric 17 (water in the present embodiment) 17 to 13-16. And the dielectric constant distribution state of the microwave space 9 is changed depending on the presence or absence of the dielectric 17 in the plurality of passages 13 to 16 so as to change the microwave distribution.

  In addition, the microwave heating apparatus 1 is used by partitioning the microwave space 9 and mounting the table 10 on which the object to be heated 2 is mounted, the setting means 32 that can be operated by the user, and the front of the heating chamber 3 so as to be opened and closed. A person has a door 34 through which the heated object 2 enters and leaves the heating chamber 3. Since the mounting table 10 is made of a low-loss dielectric material such as ceramic or glass, the microwave can easily pass through and can be sent to the heating chamber 3 formed above the microwave.

  The microwave radiating means 11 is connected to the shaft 7, the magnetron 4, the waveguide 5 for guiding the radiated microwave, the radiation antenna 8 having the shaft 7 coaxially coupled to the opening 6 of the waveguide 5, and the shaft 7. And a motor 12 that rotates the radiation antenna 8 to change the distribution of the microwave space 9 to some extent.

  The passages 13 to 16 are passages through which the dielectric 17 can move, are made of glass, and extend inside and outside the heating chamber 3. A dielectric 17 is stored in the tank 18 and is moved by pumps 19 to 22 constituting a circulation means. As for this passage, as shown in FIG. 3 in the present embodiment, a rubber water supply hose 23 connected to the pumps 19 to 22 and a variable distribution container 24 made of glass of a low-loss dielectric material. And a drainage hose 25 made of rubber. The water supply port 26 and the drainage port 27 of the distribution variable container 24 are projected to the outside of the heating chamber 3 from the openings 29 and 30 provided in the wall surface 28 forming the heating chamber 3, respectively. The drain hose 25 is connected. With this configuration, the main body 31 of the distribution variable container 24 is exposed to the microwave in the heating chamber 3, and the microwave distribution changes depending on the presence or absence of the dielectric 17 in the main body 31. The dielectric 17 in the main body 31 is naturally discharged to the tank 18 through the drainage port 27 and the drainage hose 25 according to gravity, but is equivalent to the amount of drainage through the water supply hose 23 and the water supply port 26 by the pumps 19 to 22. If the above dielectric material 17 is continuously supplied, the dielectric material 17 can be filled in the main body 31. The volume of the main body 31 can be designed arbitrarily, but if it becomes too large, there is a risk that the dielectric 17 will absorb the microwave and the speed at which the heated object 2 is heated will be slow (decrease in efficiency). 50 cc or less, preferably about 10 cc.

  The setting means 32 is operated by the user in order to set the start / end of heating, the setting of the heating time, the setting of the heating end temperature, the selection of the menu, and the like. The control means 33 performs predetermined control according to the setting contents of the setting means 32, and controls the emission of microwaves from the magnetron 4, the driving of the motor 12, the operation of the pumps 19 to 22, and the like.

  FIG. 4 shows a block diagram of the control system. This control system is mainly configured by the control means 33 including a microprocessor, for example.

  The microwave heating apparatus having the above-described configuration heats the article to be heated 2 by supplying microwaves to the heating chamber 3 that accommodates the article to be heated 2. The microwave radiated from the magnetron 4 propagates through the waveguide 5 and is radiated from the radiation antenna 8 to the microwave space 9. The microwave space 9 is vertically divided by the mounting table 10. However, since the mounting table 10 is made of a low-loss dielectric material such as ceramic or glass, the microwave can easily pass through and is formed on the mounting table 10. A microwave can be sent to the heating chamber 3. Here, the radiation antenna 8 has directivity, and the distribution of the microwave space 9 can be changed to some extent by changing the direction of microwave radiation depending on the direction. For this reason, the radiation antenna 8 is rotated by the motor 12 connected to the shaft 7.

  Next, the time change of the water amount in the passages 13 to 16, in particular, the distribution variable container 24 will be described with reference to FIG. When the pump operation is started (on) at time t_on, water supply starts from the water supply hose 23 shown in FIG. 3 into the distribution variable container 24 through the water supply port 26, but the drainage port 27 is located below the distribution variable container 24. A part of the dielectric 17 is drained through the drain port 27 and the drain hose 25. Here, the amount of water in the variable distribution container 24 can be kept constant as the amount of water increases while the amount of water supply is greater than the amount of drainage due to the ability of the pump. When the pump operation is stopped (off) at t_off, the water supply is lost and only drainage continues, so the amount of water in the distribution variable container 24 decreases and eventually becomes zero. As the amount of water in the distribution variable container 24 increases, the water pressure increases and the amount of drainage increases. When the amount of water in the distribution variable container 24 decreases, the water pressure decreases and the amount of drainage tends to decrease. It is thought that a curve like this is drawn. Since the amount of water supply can be adjusted by controlling the operation of the pump, the amount of water in the distribution variable container 24 between t_on and t_off can also be controlled as close as possible.

  Next, specific control of the insertion and removal of the dielectric 17 will be described. FIG. 6 shows a control sequence for changing the amount of water in the passages 13 to 16, particularly in the distribution variable container 24. The characteristics of the amount of water in the left rear passage 13, the left front passage 14, the right rear passage 15, and the right front passage 16 are shown in order from the top.

  From time 0 to t1, there is no water in any passage, and the state is as shown in FIG. At time t1 to t2, the dielectric 17 is present in the left rear passage 13 and the left front passage 14, and is in the state shown in FIG. At time t2 to t3, the dielectric 17 is present in the right rear passage 15 and the right front passage 16, and is in the state shown in FIG. From time t3 to t4, there is a dielectric 17 in the left rear passage 13 and the right rear passage 15, which is the state shown in FIG. From time t4 to t5, there is a dielectric 17 in the left front passage 14 and the right front passage 16, which is the state shown in FIG. 2 and FIGS. 7 to 10 show portions 35 to 39 in which the article to be heated 2 is particularly easily heated. In particular, FIG. 2 to FIG. A portion 35 that is easily heated is also shown. The portions 36 to 39 that are easily heated in FIGS. 7 to 10 are shifted in position from the portion 35 that is easily heated in FIG. 2.

  First, since the positions of the passage 13 and the passage 15 and the passage 14 and the passage 16 are substantially left and right as viewed from the axis 7 (the center of rotation) of the radiating antenna 8, only the left passages 13 and 14 are dielectric. In a state where there is a dielectric 17 (FIG. 7) and a state where the dielectric 17 is present only in the right passages 15 and 16 (FIG. 8), the position of the portion that is easily heated is reversed. That is, the easily heated portion 36 in FIG. 7 is shifted to the left side and the easily heated portion 37 in FIG. 8 is shifted to the right side with respect to the easily heated portion 35 in FIG. Therefore, if the state of FIG. 7 and the state of FIG. 8 are switched evenly, the portions to be heated are different, which leads to uniform heating distribution.

  Further, the positions of the passage 13 and the passage 14 and the passage 15 and the passage 16 are substantially the positions of the front and rear as viewed from the axis 7 (center of rotation) of the radiating antenna 8, so that only the rear passages 13 and 15 are dielectric. In the state in which the body 17 is present (FIG. 9) and the state in which the dielectric 17 is present only in the front passages 14 and 16 (FIG. 10), the position of the portion that is easily heated is reversed. That is, the easily heated portion 38 in FIG. 9 is shifted to the front side and the easily heated portion 39 in FIG. 10 is shifted to the rear side with respect to the easily heated portion 35 in FIG. Therefore, if the state shown in FIG. 9 and the state shown in FIG. 10 are switched evenly, the heated portions are shifted from each other, which leads to uniform heating distribution of the article 2 to be heated.

  FIG. 11 shows a conceptual diagram of uniform heating distribution. FIG. 11A shows a case of a general microwave heating apparatus. By continuing the heating in the state of FIG. 2, particularly the central portion of the portion 35 that is easily heated is locally heated. FIG. 11B shows the control of the entry and exit of the dielectric 17 from time 0 to t5 as shown in FIG. 6 according to the present embodiment. The heating parts 40 are widened by overlapping the parts 35 to 39 that are easily heated, And there is no local overheating.

  FIG. 12 shows another control sequence for changing the water amount. This is because there is always a dielectric 17 in one of the passages, and the presence / absence of the dielectric 17 is maintained for a long time in order to reduce the number of times the dielectric 17 is put in and out as much as possible. is there. As a result, the number of times the pump is started is reduced, and the durability is improved.

  FIG. 13 shows still another control sequence for changing the amount of water. In this case, the dielectric 17 is provided only in a single passage. Of course, three of the four paths may be filled with the dielectric material 17 or all four may be filled.

  As described above, the microwave heating apparatus 1 according to the present embodiment includes the microwave radiating unit 11, the microwave space 9 in which the microwave radiated from the microwave radiating unit 11 can propagate, and the microwave space 9. A heating chamber 3 which is provided in a part and can accommodate the object to be heated 2, a plurality of glass passages 13 to 16 disposed in the microwave space 9, and the dielectric 17 to the plurality of passages 13 to 16 And a control means 33 for controlling the entrance and exit, and the microwave distribution is changed by changing the dielectric constant distribution state of the microwave space 9 depending on the presence or absence of the dielectric 17 in the plurality of passages 13 to 16.

  Thereby, the dielectric constant distribution state of the microwave space 9 is changed and the microwave distribution in the microwave space 9 is changed depending on the presence or absence of the dielectric 17 in the plurality of passages 13 to 16 arranged in the microwave space 9. As a result, the microwave distribution in the heating chamber 3 included in the microwave space 9 can be changed. Therefore, the electric field distribution of the microwave around the object to be heated 2 accommodated in the heating chamber 3 changes, and local heating like when heating with a single distribution is suppressed, and the object to be heated 2 is heated. Uniform heating can improve the workmanship after heating.

  If there is only one passage, there are only two microwave distributions of the presence or absence of the dielectric 17, but if the number of passages is two, there are four ways (if there is no dielectric in any passage, If there is a dielectric in only one of the passages, or if there is a dielectric in any of the passages), similarly, if the number of passages is three, eight microwave distributions and the number of passages are four. If this is the case, the number of microwave distributions that can be selected each time the number of passages is increased, such as 16 microwave distributions, can be dramatically increased, and the microwave distribution can be switched to an arbitrary microwave distribution by controlling the presence or absence of the dielectric 17. It becomes possible. As a result, the article to be heated 2 can be heated more uniformly. In the present embodiment, since there are four passages, 16 microwave distributions can be switched.

  In the microwave heating apparatus 1, in particular, the microwave radiating means 11 is configured to radiate microwaves from the radiating antenna 8 that rotates about the axis 7, and the passages 13 to 16 are symmetrically viewed from the axis 7. The configuration is arranged. Thereby, the microwave distribution in the case where the dielectric 17 is present in a certain passage and the microwave distribution in the case where the dielectric 17 is present in another symmetric passage can be a symmetric microwave distribution. For example, the microwave distribution when the dielectric 17 is present only in the first passage is a distribution that causes local concentration in a portion (first portion) that is mutated in any direction with respect to the axis. In this case, the microwave distribution in the case where the dielectric 17 is present only in the second passage causes a distribution that causes local concentration at a portion mutated in the opposite direction to the axis (second portion). be able to.

  In particular, a door 34 is provided in front of the heating chamber 3, and the shaft 7 is positioned substantially in the center of the lower portion of the heating chamber 3, and when viewed from the front, the passages 13 and 14 are at least on the left of the shaft 7 and on the right of the shaft 7. The passages 15 and 16 are arranged. Further, the passages 14 and 16 are disposed at least in front of the shaft 7 and the passages 13 and 15 are disposed behind the shaft 7 when viewed from the front. As a result, the dielectric 17 is present only in the left passages 13 and 14, the dielectric 17 is present only in the right passages 15 and 16, and the dielectric 17 is present only in the front passages 14 and 16, and the rear. When the dielectric 17 exists only in the passages 13 and 15, a symmetric microwave distribution can be obtained with the axis 7 as the center. In the case of a general microwave oven as the microwave heating apparatus 1, there are many cases in which the shape of the food that is a typical object to be heated 2 is flat or a plurality of items are heated at the same time. In many cases, it is desired to be uniform left and right and front and rear rather than the direction. In such a case, a uniform heating distribution can be expected.

  Moreover, the microwave heating apparatus 1 is configured such that the control means 33 controls the entry and exit of the dielectric 17 into and from the passages 13 to 16 during the microwave heating. As a result, the object to be heated 2 is heated with a constant microwave distribution until halfway, and the object to be heated 2 is heated with a different microwave distribution after controlling the entry and exit of the dielectric 17 into and from a predetermined passage. it can. In particular, the power for controlling the entry / exit of the dielectric 17 can be much lower (100 W or less) than the power required for microwave heating (for example, 1200 W). Easy to fit. In this case, it is not necessary to interrupt the microwave heating when controlling the entry / exit of the dielectric 17, so that the microwave heating can be continued efficiently.

  In the microwave heating apparatus 1, the dielectric 17 is made of water. As a result, water has a high relative dielectric constant of about 80, which is 80 times that of air 1. In general, the wavelength of the microwave propagating inside the dielectric 17 is inversely proportional to the square root of the relative dielectric constant, so that the wavelength is compressed to about 1/9 (≈1 / √80) inside the water. On the other hand, if the microwave wavelength is considered to be constant, only the region where water is present appears to be enlarged 9 times. Therefore, depending on the presence or absence of water and the location of water, the microwave space has the same effect as the shape of the microwave space is deformed, and the microwave distribution can be greatly changed. Also, water is easy to obtain, safe and easy to handle. With regard to controlling the flow of water to and from the passages 13 to 16, it is easy to use general-purpose parts such as pumps 19 to 22 (and valves), and pipes for carrying water in various fields are practical. It is possible to adopt as a passage of the present invention.

  Moreover, the microwave heating apparatus 1 has comprised the passages 13-16 with glass. Thus, the passage can be easily made of a low-loss dielectric material. Further, since the shape has a degree of freedom, the shape and position of the dielectric 17 disposed inside can be arbitrarily determined by optimal design.

  Furthermore, the microwave heating apparatus 1 is configured to circulate the dielectric 17 discharged from the passages 13 to 16 via pumps (circulation means) 19 to 22. As a result, the dielectric 17 can be reused and there is no waste, and it is possible to prevent the user from setting the dielectric 17 and post-processing.

(Embodiment 2)
14 to 19 show a microwave heating apparatus according to Embodiment 2 of the present invention. The same elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 14, the microwave heating device 41 in the present embodiment is provided with passages 42 and 43 through which the dielectric (water) 17 can move over the inside and outside of the heating chamber 3. The dielectric 17 is stored in the tank 44 and is moved by a pump 45 and valves 46 and 47 as circulation means. Here, since the passages 42 and 43 are connected in series, the one pump 45 and the two valves 46 and 47 are used to switch the dielectric 17 into and out of the passages 42 and 43. As for the passage 42, in particular, as shown in FIG. 15, a variable distribution container 51 formed by a water supply tube 48 connected to a pump, a glass window 49 of a low-loss dielectric material, and a wall surface 50 forming the heating chamber 3. And a drainage tube 52. The water supply port 53 and the water discharge port 54 of the distribution variable container 51 are each connected to the water supply hose 48 and the water discharge hose 52 outside the heating chamber 3 by projecting the wall surface 50 to the outside by heating. With this configuration, it is the distribution variable container 51 that is exposed to microwaves in the heating chamber 3, and the microwave distribution changes depending on the presence or absence of the dielectric 17 in the distribution variable container 51. The dielectric 17 in the variable distribution container 51 is guided to the passage 43 through the drain port 54 and the drain hose 52, but is discharged or maintained depending on the open / closed state of the valve 46 disposed between the passage 43. It can be switched. The packing 55 is made of a material such as silicon and fills the gap between the glass window 49 and the wall surface 50 to prevent water leakage.

  The setting means 56 is operated by the user to perform settings such as heating start / end, heating time setting, heating end temperature setting, menu selection, and the like. The control means 57 performs predetermined control according to the setting contents of the setting means 56, and controls the emission of microwaves from the magnetron 4, the driving of the motor 12, the operation of the pump 45, valves 46 and 47, and the like. As shown in the block diagram of the control system in FIG. 16, this control system is mainly configured by a control means 57 including a microprocessor, for example. In particular, the setting means 56 has a menu selection means 58, and among the selectable menus, there are menus such as “milk” and “root vegetables”.

  Next, specific control of the insertion and removal of the dielectric 17 will be described. FIG. 17 shows a case where the object to be heated 2 is a flat food 59 that is neither “milk” nor “root vegetables”, and neither of the passages 42 and 43 has the dielectric 17. In this case, distribution performance equivalent to that of a general microwave heating apparatus can be obtained.

  Here, the heating distribution in the vertical direction in a general microwave heating apparatus will be described. In general, when trying to heat various foods as uniformly as possible, we want to eliminate the heating distribution in the vertical direction. Therefore, assuming the height of the food to be actually used, the height on the mounting table 10 is about 30 to 50 mm. It is conceivable to design so that microwaves are concentrated. In this case, the central part tends to be heated evenly, whether it is a drink such as milk or a root vegetable such as potato. In the case of root vegetables, there is no convection because it is solid, and the heat conduction from the center to the surroundings is uniform, so if the center part is heated quickly, a satisfactory result can be obtained. However, in the case of drinks, there is convection, and if the hot part is at a low position, it flows upward and mixes, but if the cold part is at a low position, it is not mixed with the upper part and is kept at a low temperature. Therefore, when the center portion is heated quickly, it tends to be uniform from the center to the top and only the bottom portion remains cold. For this reason, in order to improve the distribution of drinks, it is conceivable that the microwaves are concentrated at a height of 10 to 20 mm on the mounting table 10 with a lower height. In this way, the bottom part of the drink is heated to some extent, and the rest can be made uniform by convection. However, in this case, even in the root vegetables, heating of the bottom portion is accelerated, and since there is no convection, it may happen that the bottom is boiled first and the upper side remains cold. Therefore, it will be designed with a balance between the drink and the root vegetables (for example, concentrate on 20-30 mm), both are not perfect, but the result is decent, that is, the drink has a slightly cold bottom and the root vegetable has a slightly bottom It's easy to get hot.

  Therefore, in the present embodiment, when there is no dielectric 17 in both the passages 42 and 43, the distribution in the vertical direction is not considered so much, and the flat food distribution is improved. 17 is easily heated at the bottom of the drink, and filling the passage 17 with the dielectric 17 makes it easy to heat the center of the root vegetables (although the course of the passages 42 and 43 may be reversed). The passages 42 and 43 are provided at positions where the two can be switched.

  FIG. 18 shows the case where the object to be heated 2 is milk 60, and the user selects the “milk” key from the menu selection means 58 of the setting means 56, so that the control means 57 is controlled by the pump 45, valve 46, 47 is controlled, and only the upper passage 42 is filled with the dielectric 17. In the design stage, it is known that when the dielectric 17 is only in the upper passage 42, the microwaves are concentrated and heated at the bottom of the drink, and as a result, it is naturally stirred by convection and a uniform workmanship is obtained. It is done.

  FIG. 19 shows a case where the object to be heated 2 is a potato 61, and the user selects the “root vegetable” key from the menu selection means 58 of the setting means 56, so that the control means 57 controls the pump 45, valve 46, 47 is controlled, and only the lower passage 43 is filled with water 17. In the design stage, when the water 17 is present only in the lower passage 43, it is known that the microwaves are concentrated and heated in the center of the root vegetables, and as a result, a natural and uniform result can be obtained by heat conduction. Therefore, both drinks and root vegetables can provide a uniform workmanship.

  As described above, the microwave heating device 41 according to the present embodiment is configured such that the passages 42 and 43 are arranged in at least two places having different distances as viewed from the shaft 7. As a result, the microwave distribution when the dielectric 17 is present only in the passage 42 and the microwave distribution when the dielectric 17 is present only in the other passage 43 that is different from the passage 42 in the distance from the shaft 7 are 7 can be asymmetrical microwave distribution. If the microwave distribution with the dielectric 17 only in the passage 42 is such a distribution that causes local concentration at a specific part (the bottom of the drink) on the shaft 7, the passage 43 and the shaft If the dielectric 17 is present only in the passage 43, the specific portion on the shaft 7 (the bottom of the drink) is the same as when the dielectric 17 is present only in the passage 42. ) Can easily cause local concentration. However, by arranging the passage 43 so that the distance from the axis 7 is different from the passage 42, the microwave distribution when the dielectric 17 exists only in the passage 43 is asymmetric with respect to the axis 7, that is, the axis It is also possible to make a distribution that concentrates at different heights (center of root vegetables) in the upper part.

  Further, the microwave heating device 41 is configured such that the passage 43 is disposed at least above the shaft 7 and the passage 42 is disposed further above the passage 43 as viewed from the front. As a result, the passage 43 is close to the radiating antenna 8, and the passage 42 is arranged far from the radiating antenna 43. Generally, it is known that the electric field attenuates as the distance from the radiating antenna 8 increases, and the path 43 close to the radiating antenna 8 is exposed to a stronger electric field. It is assumed that the influence of the above, that is, the change in the microwave distribution becomes larger. Therefore, in comparison with the microwave distribution without the dielectric 17, when the dielectric is only in the passage 42, the microwave distribution is slightly changed, and when the dielectric 17 is only in the passage 43. It is also possible to greatly change the microwave distribution.

  Further, the microwave heating device 41 has setting means 56 that can be set by the user, and the control means 57 allows the dielectric 17 to enter and exit the predetermined passages 42 and 43 according to the setting contents of the setting means 56. It is configured to control. Thereby, according to the setting content, it can be changed to a microwave distribution that suppresses uneven distribution. In particular, since the setting means 56 has the menu selection means 58 and can select “milk” or “root vegetables”, the shape and material of the heated object 2 can be specified to some extent. For “milk”, there is convection in the form of a mug or cup, so it is better to heat the lower part, and for “root vegetables”, it is only necessary to heat the center of the potato.

  In addition, if it is `` thaw '', it should be a flat shape, so the distribution of front and back and left and right should be better than the top and bottom distribution, and in the case of `` convenience store lunch '', the area of rice and side dishes is divided in a wide area You can guess in advance that you should be balanced.

  Further, when the heating time is set by the setting means 56, the total time is determined. Therefore, if the distribution is changed twice in the middle, it is possible to determine in advance how many minutes should be distributed. Therefore, controlling the entry / exit of the dielectric 17 to / from a predetermined passage according to the set content has a certain effect for uniform heating.

(Embodiment 3)
20 to 34 show a microwave heating apparatus according to Embodiment 3 of the present invention. The same elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIGS. 20 and 21, the microwave heating device 62 in the present embodiment is arranged above the radiating antenna 8 in a loop shape with passages 63 and 64 through which the dielectric (water) 17 can move. It is provided over the inside and outside of the microwave space 9. A dielectric 17 is stored in the tank 65 and is moved by pumps 66 and 67 as circulation means. The passages 63 and 64 are made of a low-loss dielectric material, such as a silicon tube, and are flexible to some extent and easy to dispose.

  In addition, on the wall surface of the heating chamber 3, an infrared sensor (temperature detection means) 68 capable of simultaneously measuring the temperature at a plurality of locations (for example, 8 locations) is slidably disposed. By the scanning operation that swings the infrared sensor 68, the temperature of a plurality of measurement points in the heating chamber 3 can be measured, and the position of the object to be heated 2 can be determined by monitoring the temperature of the measurement points over time. You can also know.

  The setting means 69 is operated by the user in order to set the start / end of heating, the setting of the heating time, the setting of the heating end temperature, the menu selection, and the like. The control means 70 performs predetermined control in accordance with the setting contents of the setting means 69 and the temperature detection signal from the infrared sensor 68. The control means 70 emits microwaves from the magnetron 4, drives the motor 12, and pumps 66 and 67. It controls the operation, the scanning operation of the infrared sensor 68, and the like. FIG. 22 shows a block diagram of the control system.

  Here, control methods such as temperature measurement, position determination, and quantity determination of the object to be heated 2 in the frozen state using the infrared sensor 68 will be described.

  As shown in FIG. 23 (a), the infrared sensor 68 is heated while scanning in the direction of the arrow in the figure by swinging the infrared sensor 68 while simultaneously detecting the temperature of a plurality of points (n points) at the same time. Temperature measurement is performed at a plurality of measurement points (m points in the scanning direction) in the chamber 3. Accordingly, the temperature of all n × m measurement points shown in FIG. 23B is detected by one scan of the infrared sensor 68. The temperature of the object to be heated M is determined based on the rate of increase with respect to the elapsed time of the temperature at each measurement point that is continuously detected, and the position of the object to be heated M is obtained. Treat as M temperature.

  FIG. 24 shows the temperature distribution at the L-line position in FIG. 23B when scanning by the infrared sensor 68 is continuously performed a plurality of times. In FIG. 24, the peak position (valley position) of the temperature distribution at which the temperature changes particularly within one scan width corresponds to the position of the object to be heated M on the L line in FIG. Therefore, the position of the object to be heated M in the heating chamber 3 is obtained from the peak existence position of this temperature distribution. Here, the initial temperature of the object to be heated M can be determined by obtaining the temperature corresponding to the position of the object to be heated M by going back to the initial stage of heating or starting the temperature measurement. Further, the amount of the object to be heated M can be estimated by obtaining the temperature increase rate ΔT of the object to be heated M from the gradient of the line connecting the peaks of the temperature distribution curve in FIG. 24 (dotted line in FIG. 24). . As shown in FIG. 25, when two objects to be heated M1 and M2 having different weights at the same initial temperature are heated under the same conditions, the temperature increase rate ΔT differs depending on the weight, and the object to be heated with a small amount is used. This is because the temperature increase rate becomes ΔTL when M1 is heated, and the temperature increase rate becomes ΔTM smaller than ΔTL when the heated object M2 having a large amount is heated. By determining the initial temperature of the object to be heated M and estimating the amount of the object to be heated M from the temperature increase rate ΔT, it is possible to set the thawing process end time of the frozen product.

  On the other hand, control of the water 17 to the passages 63 and 64 by the pumps 66 and 67 in order to make the heating distribution uniform will be described.

  FIG. 26 is a control sequence for changing the amount of water in the passages 63 and 64. The horizontal axis represents time, and in order from the top, shows the timing of quantity determination, the amount of water in the inner passage 63, and the amount of water in the outer passage 64. First, it is assumed that the quantity determination is completed at time t0 according to the sequence of the infrared sensor 68. The control means 70 determines the total time to be heated from the amount at this time as t4, and controls the amount of water in the passages 63 and 64 by ¼ time distribution in the order as shown in FIG. Take control.

  At time 0 to t1, there is no water in any passage, and a portion 71 that is easily heated in a ring shape is generated in the frozen object M as shown in FIG. At time t1 to t2, the dielectric 17 is present in the inner passage 63, and a portion 72 that is easily heated is formed outside the portion 71 as shown in FIG. At time t2 to t3, the dielectric 17 is present in the outer passage 64, and portions 73 that are easily heated are formed on the inner side and the outer periphery of the portion 71 as shown in FIG. Since the positions 71 to 73 that are easily heated are different in position, it is obvious that they can be heated more uniformly if they are combined with each other. Thereafter, at time t3 to t4, the dielectric 17 is again in the inner passage 63, and the state shown in FIG. 28 is restored.

  The reason for the return will be described with reference to FIG. FIG. 30 shows the time change of the maximum temperature and the minimum temperature in the temperature distribution of the object M detected by the infrared sensor 68, and the difference between the two can be considered as so-called uneven heating. If the heating distribution so far (that is, the state of FIG. 27) is continued, the difference between the maximum temperature K1 and the minimum temperature K2 increases with time. However, when heating is performed up to time t3 in the control sequence of FIG. 26 as in the present embodiment, the temperature changes at the maximum temperature K3 and the minimum temperature K4. At time 0 to t1, since there is no dielectric 17 in any of the passages, this embodiment also has the same heating distribution as before, and K1 and K3, K2 and K4 match, and the temperature unevenness at time t1 Becomes ΔT1. However, at time t1 to t2, there is a dielectric 17 in the inner passage 63, and the portion that is easily heated as shown in FIG. 28 shifts, so the slope of the rise of the maximum temperature K3 is dull and the slope of the rise of the minimum temperature K4 is large Therefore, the temperature unevenness at time t2 is reduced to ΔT2. At time t2 to t3, the dielectric 17 is present in the outer passage 64, and the portion that is easily heated as shown in FIG. 29 shifts. However, the inclination of K3 becomes slightly larger than that between time t1 and t2, and the inclination of K4. The temperature non-uniformity expands to ΔT3, for example. At time t3, the remaining time is only t3 to t4 (1/4 of the total time), so that the heating is reheated with the heating distribution that reduces the most uneven heating. Therefore, regarding the control of water from t3 to t4, it is necessary to determine which condition is the best at the time point t3, and the method is preferably to compare the level of uneven heating generated under each condition. That is, ΔT1 (> 0), ΔT2−ΔT1 (<0), and ΔT3−ΔT2 (> 0) are compared, and as a condition for making the unevenness ΔT3 (> 0) at time t3 as close to 0 as possible, ΔT2−ΔT1 (< 0) is most appropriate. That is, it is a heating distribution at time t1 to t2, and the condition is that the water 17 is filled only in the inner passage 63. Such processing as calculation and determination can be executed in the control means 70.

  As described above, the heating unevenness at the end of heating t4 becomes ΔT4, which can be made considerably smaller than the heating unevenness ΔT0 by the conventional heating method.

  Now, with reference to FIGS. 31 to 34, the principle of the distribution in the microwave space 9, in particular, the standing wave distribution of the microwave will be described.

  For the sake of simplicity, assuming that there is a radio wave opening 74 for supplying microwaves in the center of the bottom of the heating chamber 3 instead of the radiating antenna 8, a strong magnetic field 75 ( Due to the broken line arrows), the strong magnetic fields 76 and 77 in the same direction (respectively broken line arrows) are likely to occur. Then, when the microwave enters the heating chamber 3, the microwave resonates in the heating chamber 3. In the resonance state, unlike the transmission state in the waveguide, the phases of the magnetic field and the electric field are shifted by 90 °. Therefore, the strong electric fields 78 and 79 (solid arrows) that are out of phase with the strong magnetic fields 76 and 77 It arises so that the part 74 may be inserted | pinched.

  The resonance state is determined by the shape of the heating chamber 3 and the position of the radio wave opening 74 when there is no object to be heated. In this embodiment, the strong electric fields 78 and 79 that are out of phase with the strong magnetic fields 76 and 77 are heated. Standing perpendicular to the bottom surface of the chamber 3, a strong electric field 80 stands in the same direction as the strong electric field 78 (backward in FIG. 31), and a strong electric field 81 in the same direction as the strong electric field 79 (frontward in FIG. 31). Let's stand. Of course, the direction is reversed at a speed of 2.45 GHz. Here, hatched portions in FIG. 31 indicate regions where the electric field is stronger than a certain level among the electric fields generated on the bottom surface of the heating chamber 3, and three in the depth direction (x direction) of the heating chamber 3 in the width direction. There are four strong electric fields in the y direction. This is an antinode of an electric field caused by the electromagnetic wave being distributed as a standing wave in the heating chamber 3 due to the resonance state, and the number of antinodes is called a mode. Usually, when the shape of the heating chamber is represented in three dimensions and the dimensions in each direction are x, y, and z, if there are only r, s, and t antinodes in each direction, the mode is (r s t ). In the illustrated case, r = 3 and s = 4.

  FIG. 32 shows an example in which the strong electric field mode shown in FIG. 31 is further simplified and three-dimensionally displayed with r = 2, s = 2 and t = 3. The hatched portion in the figure indicates a region where the electric field is stronger than a certain level among the electric fields generated on the wall surface of the heating chamber 3, and the opposing wall surfaces indicate a symmetric electric field distribution. When the number of strong electric fields 82 indicated by the hatched portion (antinode of electric field) is counted, two in the x direction (r = 2), two in the y direction (s = 2), and three in the z direction (t = 3) Standing, it can be seen that the mode (223).

  Here, when the object to be heated is not present in the heating chamber 3 and the heating chamber 3 is a rectangular parallelepiped, the mode that can stand is analytically obtained according to the dimensions of the heating chamber 3 and the position of the radio wave opening 74. be able to. Now, the dimensions of the heating chamber 3 are x, y, and z, and the number of modes standing in each direction is a combination of r, s, and t that satisfies Equation (1) (x, y, and z are in mm units, r, s and t are integers, and λ is the wavelength of the microwave and is approximately 122 mm).

1 / λ2 = (r / (2x)) 2+ (s / (2y)) 2+ (t / (2z)) 2 (1)
On the other hand, when the object to be heated exists in the heating chamber 3, a deviation from the equation (1) occurs due to the influence of wavelength compression due to the dielectric constant of the object to be heated. However, even if the object to be heated is in the heating chamber 3, a mode that satisfies the equation (1) is about to stand near the radio wave opening 74, and the mode may be disturbed at a position away from the radio wave opening 74. It has been experimentally found that there are many. Therefore, if the dimension of the heating chamber 3 is determined so that the desired mode can be obtained based on the equation (1) with the wavelength λ≈122 mm, almost any mode can be generated. Further, in the case of having rotatable radiation (or stirring stirrer blades), it is considered that the position of the radio wave opening 74 shown in FIG. 31 is continuously changed by rotation. Can be changed.

  Furthermore, the mode can be changed by changing the wavelength λ of the microwave. Specifically, the microwave wavelength is changed by supplying the dielectric 17 into the heating chamber 3. Here, assuming that the wavelength after change is λa and the dielectric constant in the heating chamber 11 is ε, the wavelength λa after change is expressed by equation (2).

λa = λ / √ε (2)
The dielectric constant ε is 1 for air and around 80 for water. That is, as described above, by supplying the dielectric 17 to the passages 63 and 64 in the heating chamber 3, the dielectric constant of the passages 63 and 64 in the heating chamber 3 changes. From the relationship, the wavelength of the microwave shifts to the short wavelength side. Then, the mode of the strong electric field determined by the equation (1) changes. Since the degree of this change is proportional to the relative dielectric constant of the dielectric 17, it is considered that if the relative dielectric constant is large, an effect can be obtained even with a small amount. If the relative dielectric constant is small, the effect cannot be achieved unless a large amount is added. . Ideally, a material having a large relative dielectric constant and a small dielectric loss is desirable. If the dielectric 17 is water, the relative permittivity and dielectric loss are large, so if too much is added, the water itself will absorb the microwave, and the heating efficiency of the object to be heated may decrease. Cost.

  FIG. 33 shows variations of the strong electric field generated on the wall surface of the heating chamber. If the displayed strong electric field 83 is the position of the strong electric field on the bottom surface of the heating chamber 3, (a) is a mode of r = 2 and s = 2. By supplying the dielectric 17 to the passage in the heating chamber 3 from the state (a), for example, transition to the state shown in (b), (c), (d) is also conceivable. (B) is a mode of r = 5 and s = 1, (c) is a mode of r = 3 and s = 3, (d) is a mode of r = 4 and s = 4, and the state of the strong electric field changes. To do.

  FIG. 34 is an explanatory diagram in the case where the dielectric 17 is controlled during the microwave heating, and the mode is switched from the first state to the second state for uniformization. As illustrated, for example, when the first state is a mode of r = 2 and s = 2 by the strong electric field 84 (a mode in which any two of r, s, and t are 2), the second state In this state, it is desirable to generate the strong electric field 85 and the strong electric field 86 so as to include the positions to be complemented so that the strong electric field is generated at the position where the strong electric field is not generated in the first state.

  Thus, in order to generate a strong electric field at a position to be complemented in the second state, the amount and position of the dielectric 17 supplied into the heating chamber 3 are adjusted, or the radiation antenna 8 and the stirrer that are normally rotated are adjusted. Fine adjustment can be performed by stopping the blade in a predetermined direction. By controlling the position of this strong electric field, the object to be heated can be microwaved more uniformly and more uniformly, and the workmanship after heating can be further improved.

  As described above, the microwave heating device 62 of the present embodiment has the infrared sensor (temperature detection means) 68 that detects the temperature of the object to be heated, and the control means 70 is the infrared sensor (temperature detection means) 68. Based on the detection signal, the entry and exit of the dielectric 17 into and from the passages 63 and 64 are controlled. Accordingly, while seeing the temperature unevenness of the object M to be heated from the detection signal of the infrared sensor (temperature detecting means) 68, the unevenness of the object 17 enters and exits the passages 63 and 64 if the unevenness increases. It can be changed to a microwave distribution that suppresses unevenness. Further, if the temperature unevenness is detected while sequentially switching the combination of the presence or absence of the dielectric 17 in each passage, the combination that can minimize the temperature unevenness can be found. Unevenness can be reduced. In addition, if it is known in advance what kind of heating distribution is obtained depending on the combination of the presence or absence of the dielectric 17 in each of the passages 63 and 64, it becomes a condition with a high possibility of canceling the temperature unevenness while detecting the temperature unevenness. Thus, the dielectric 17 can be frequently controlled, and can be heated while maintaining a state in which the temperature unevenness of the object to be heated is not generated so much from the beginning to the end.

  The control means 70 is configured to control the entry and exit of the dielectric 17 into and from the passages 63 and 64 during microwave heating. Accordingly, the object to be heated can be heated with a constant microwave distribution until halfway, and the object to be heated M can be heated with a different microwave distribution by controlling the entry and exit of the dielectric 17 into and from a predetermined path. In particular, the power for controlling the entry / exit of the dielectric 17 can be much lower (100 W or less) than the power required for microwave heating (for example, 1200 W). Easy to fit. In this case, it is not necessary to interrupt the microwave heating when controlling the entry and exit of the dielectric 17, so that the microwave heating can be continued efficiently.

  Further, the passages 63 and 64 are made of a resin tube. Thus, the passages 63 and 64 can be easily made of a low-loss dielectric material. Further, since there is a degree of freedom in shape, the shape and position of the dielectric disposed inside can be arbitrarily determined by optimal design.

  In the present embodiment, water is used as the dielectric material 17, but a material having a high relative dielectric constant may be used, and a dielectric loss is preferably small. In addition, since water has a risk of being frozen under zero and being unable to control the entry / exit, it is easy to consider using antifreeze.

  Each of the first to third embodiments described above can be implemented in various combinations, and is not limited to the configuration of the embodiment itself.

  As described above, the microwave heating apparatus according to the present invention can achieve uniform heating of an object to be heated and improve workmanship after heating, so that various dielectrics such as food can be heated, thawed, and pottery heated. It can be applied to uses such as drying, sintering or biochemical reaction.

Front sectional view of the microwave heating apparatus according to the first embodiment of the present invention. Plan view of the microwave heating device (A) The front view which looked at the channel | path part of the dielectric material in the same microwave heating apparatus from the A direction of FIG. 1 (b) BB sectional drawing of (a) Block diagram of the control system for controlling the microwave heating device The characteristic figure which shows the water quantity change in the distribution variable container in the passage section of the same microwave heating device Explanatory drawing which shows the control sequence of the water quantity change in the distribution variable container in the channel | path part of the same microwave heating device Explanatory drawing of a state where there is a dielectric in the left rear passage and the left front passage of the microwave heating apparatus Explanatory drawing of a state where there is a dielectric in the right rear passage and the right front passage of the same microwave heating device Explanatory drawing of a state where there is a dielectric in the left rear passage and the right rear passage of the microwave heating apparatus Explanatory drawing of a state where there is a dielectric in the left front passage and right front passage of the microwave heating apparatus (A) Image diagram of uniform heating distribution when heated by a general microwave heating device (b) Image diagram of uniform heating distribution by control sequence of FIG. Explanatory drawing which shows the other control sequence of the same microwave heating device Explanatory drawing showing still another control sequence of the same microwave heating apparatus Front sectional view of the microwave heating apparatus according to Embodiment 2 of the present invention Sectional view of the dielectric passage in the microwave heating apparatus Block diagram of the control system for controlling the microwave heating device Explanatory drawing of the state where flat food is heated by the microwave heating device Explanatory drawing of the state where milk is heated by the microwave heating device Explanatory drawing of the state where potato is heated by the microwave heating device Front sectional view of a microwave heating apparatus according to Embodiment 3 of the present invention Plan view of the dielectric passage in the microwave heating apparatus Block diagram of the control system for controlling the microwave heating device (A) The figure which shows the mode of the temperature measurement of the to-be-heated object by the infrared sensor in the microwave heating apparatus (b) Explanatory drawing which shows the data obtained by measurement Characteristic diagram showing temperature distribution when temperature measurement by infrared sensor in the microwave heating device is continuously performed several times Characteristic diagram showing the state of temperature change when two heated objects with different weights are heated under the same conditions by the same microwave heating device Explanatory drawing which shows the control sequence of the microwave heating device Explanatory drawing of the state where there is no water in the passage of the microwave heating device Explanatory drawing of a state where there is a dielectric in the passage inside the microwave heating device Explanatory drawing of a state where there is a dielectric in the outside passage of the microwave heating device Characteristic diagram showing the time change of the maximum temperature and minimum temperature of the heated object detected by the infrared sensor of the microwave heating device The top view which looked at the bottom of the heating chamber of the microwave heating device from the top Explanatory drawing which simplifies the mode of the strong electric field of the microwave heating apparatus and illustrated three-dimensionally Explanatory drawing showing variations of the strong electric field generated on the wall surface of the heating chamber of the microwave heating apparatus Explanatory drawing which showed the example of the position of the strong electric field in the 1st state and 2nd state of the microwave heating device

Explanation of symbols

1, 41, 62 Microwave heating device
2, M Object to be heated
3 Heating chamber
7 axes
8 Radiating antenna
9 Microwave space
11 Microwave radiation means
13, 14, 15, 16, 42, 43, 63, 64 passage
17 Dielectric
19, 20, 21, 22, 45, 66, 67 Pump (circulation means)
32, 56, 69 Setting means
33, 57, 70 Control means
34 Door
59 Flat food (object to be heated)
60 Milk (to be heated)
61 potato (to be heated)
68 Infrared sensor (temperature detection means)

Claims (5)

A microwave radiating means, a microwave space in which the microwave radiated from the microwave radiating means can propagate, a heating chamber provided in at least a part of the microwave space and capable of storing an object to be heated; and the microwave A plurality of passages arranged in the wave space, and a control means for controlling the entry and exit of the dielectric into and from the plurality of passages, and the dielectric constant of the microwave space depending on the presence or absence of the dielectric in the plurality of passages A microwave heating device that changes the distribution state and changes the microwave distribution. The microwave heating device according to claim 1, wherein the microwave radiating means is configured to radiate microwaves from a radiating antenna that rotates about an axis, and the passages are arranged in at least two symmetrical positions when viewed from the axis. The microwave heating apparatus according to claim 1, wherein the microwave radiating means is configured to radiate microwaves from a radiating antenna that rotates about an axis, and the passages are arranged in at least two places having different distances as viewed from the axis. The microwave heating apparatus according to claim 1, further comprising a temperature detection unit that detects a temperature of the object to be heated, wherein the control unit controls the entry and exit of the dielectric into and from the passage based on the detection signal of the temperature detection unit. The microwave heating apparatus according to claim 1, further comprising setting means that can be set by a user, wherein the control means controls the entry and exit of the dielectric into and from the predetermined passage according to the setting contents of the setting means.