KR960009621B1 - Microwave oven - Google Patents

Abstract

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Description

Heating cooker

1 is a plan sectional view showing the internal structure of a microwave oven according to a first embodiment of the present invention.

FIG. 2 is a plan sectional view showing a configuration related to the exhaust duct plate. FIG.

3 is a front view of the second view in the R ₁ direction.

4 is an electric circuit diagram related to heating control.

FIG. 5 is a waveform diagram showing signals derived from respective circuit parts of FIG.

6 is a front view near the thermistor of the microwave oven according to the second embodiment of the present invention.

7 is a cross-sectional view taken along the line A-A of FIG.

8 is a plan sectional view of a microwave oven according to a third embodiment of the present invention.

9 is a cross-sectional view taken along the line B-B in FIG.

10 is a plan view of the detection means.

11 is a bottom view of the detection means.

12 is an electric circuit diagram related to heating control.

13 is a characteristic diagram of an output V ₀ in FIG. 12.

* Explanation of symbols for main parts of the drawings

1: heating chamber 4: food

5: magnetron (heating means) 12: exhaust duct plate

15 Distribution Channel 25 Metal Plate (Thermal Conductor)

30: BEAD type thermistor 41: AC amplifier circuit

43: comparison circuit 44: microcomputer (control means)

50: tape 60: heating chamber

74: detection means 75: thin plate substrate

76: copper foil 83: chip-type thermistor

The present invention relates to a heating cooker for cooking by heating food contained in a heating chamber such as a microwave oven. In heating cookers, such as a microwave oven, the technique of conventionally controlling heating based on the output of the humidity sensor which detects the humidity in a heating chamber is applied.

In other words, when food is put into a heating chamber and heated, the humidity first decreases because the temperature rises, and when further heated, the humidity rapidly rises due to water vapor generated in the food. For this reason, the point at which the change in humidity changes to an increase tendency or the point at which the humidity starts to rise sharply is understood as one peculiar point regarding the finished cooking state of the food.

Therefore, this unusual point is detected by monitoring the change in humidity, and the most suitable cooking is possible by performing heating control.

However, since the humidity sensor is susceptible to contamination of gas or oil, so-called refresh heating is required to eliminate this contamination. For this reason, since it is necessary to provide the heater for refresh heating with respect to a humidity sensor, there exists a problem of complicated structure, a high cost, and the increase of power consumption.

On the other hand, prior art that achieves heating control without using a humidity sensor is shown in Japanese Patent Laid-Open No. 2-306024. In this prior art, heating control is performed using a superconducting element. That is, the steam generated by heating the food imparts a thermal change to the superconducting element.

By detecting the pyroelectricity generated in the superconducting element due to this heat change, the steam generation state can be detected. Thereby, since a fixed completed cooking state of a food is detected, heating automatic control is enabled based on the output of a superconducting element. However, since the superconducting element has piezoelectricity at the same time, when vibration occurs or an external shock is applied, the output due to the piezoelectric effect is generated. For this reason, the generation | occurrence | production state of steam was not necessarily able to be detected satisfactorily, and satisfactory heating control was not obtained.

In addition, when contacted with a high temperature for a long time by the heat in the heating chamber, there is also a problem that the superconducting element causes branching deterioration and deterioration in sensing performance. Accordingly, an object of the present invention is to solve the above technical problem, and to provide a heating cooker which enables a good heating control by detecting a completed cooking state of a food with a simple configuration. In order to achieve the above object, the present invention provides a heat cooker in which a food housed in a heating chamber is heated by a heating means as a first constitution, which is in contact with the heat conductor in contact with the air in the heating chamber. And a thermistor disposed so as to extract and amplify an AC component which is an output of the thermistor, and control means for controlling the heating means based on the output of the AC amplifying means.

Moreover, in a 2nd structure, in a 1st structure, the said heat conductor is comprised by a thin metal plate, and the said thermistor is set as the bead type thermistor. Moreover, in a 3rd structure, in a 1st structure, the thermistor is arrange | positioned at the surface which does not contact the air in the said heating chamber of the said heat conductor.

In a fourth configuration, in the first configuration, a comparison means for fertilizing the output of the AC amplifying means and the thermistor output before entering the AC amplifying means and outputting the comparison result to the control means is provided. do. Moreover, as a 5th structure, in a 2nd structure, the said bead-type thermistor is stuck to the said metal plate as a tape in close_contact | adherence state.

Moreover, as a 6th structure, in a 5th structure, let this tape be a heat resistant polyimide tape. In a seventh configuration, in the first configuration, the thermal conductor is formed of a thin printed board, the thermistor is a chip thermistor, and the chip thermistor is soldered to the printed board.

Further, as an eighth configuration, in the seventh configuration, copper foil is applied to one surface of the printed board entirely, and the chip thermistor is soldered to the other surface, and one surface of the printed board is exposed to air in the heating chamber. Contact In a ninth aspect, in the seventh aspect, the printed board is a glass epoxy board.

In the first configuration, when the food is heated by the heating means, steam is generated from the food. This steam gives latent heat to this heat conductor when it distribute | circulates the distribution path which arrange | positioned the heat conductor. For this reason, the temperature of a heat conductor rises instantaneously.

Therefore, the temperature of the heat conductor vibrates repeatedly for an instantaneous rise and fall in proportion to the amount of steam generated. For this reason, since the alternating current component is a component which originates in the steam generation | generation of the output signal of the thermistor arrange | positioned in contact with a thermal conductor, when this alternating current component is extracted, the steam generation state can be detected. The control means controls the heating means based on the signal obtained by amplifying the above-described AC component by the AC amplifying means. Since the state of steam generation eventually corresponds to the completed cooking state of the food, good heating control corresponding to the completed cooking state of the food can be realized by the control by the control means. In this case, since the humidity sensor is not used, another configuration such as a heater for cleaning the humidity sensor is not required.

In addition, since the thermistor has the same piezoelectricity as that of a superconducting element, noise for vibration and shock does not occur.

In addition, the thermistor does not cause deterioration even if the high temperature state continues for a long time. In the second configuration, since the heat conductor is made of a thin metal plate and the thermistor is a bead type thermistor, the change in temperature due to latent heat is quickly transmitted to the thermistor, thereby improving the detection sensitivity of steam.

In the third configuration, the thermistor does not come into contact with the air in the heating chamber, and thus does not cause insulation failure under the influence of steam or the like.

In the fourth configuration, if there is heat remaining in the heating chamber, the output amplitude of the AC amplifying means becomes small, and in this state, the steam detection sensitivity deteriorates, but the output of the thermistor to be compared with the output of the AC amplifying circuit is also small. As a result, the influence of residual heat is automatically eliminated, and the deterioration of the steam detection sensitivity is controlled.

In the fifth and sixth configurations, the heat conduction performance between the bead-type thermistor and the metal plate can be stably maintained at a desired value, and the steam detection performance is stabilized.

In the seventh structure, the soldering area of the chip-type thermistor to the printed board is limited to a portion other than the resist film, and the heat conduction performance between the chip-type thermistor and the printed board can be stably maintained in a desired manner. Performance is stable.

In the eighth configuration, the printed circuit board is able to absorb the latent heat of steam well by the copper foil which is entirely coated on the side facing the atmosphere of the heating chamber, so that the temperature of detecting the steam is improved.

In addition, the chip-type thermistor is soldered to the other side of the printed board, making it difficult to contact the air in the heating chamber, and does not cause poor insulation due to the influence of steam or the like.

In the ninth configuration, the printed board absorbs the latent heat of vapor better.

Example

1 to 5 show a microwave oven which is a heat cooker of the first embodiment of the present invention. In FIG. 1, the turntable 2 is arrange | positioned in the heating chamber 1, and the food 4 enters and exits by opening the door 3 provided in the front surface. In connection with the heating chamber 1, the magnetron 5 which generates the heating microwave is arrange | positioned, and the microwave in this magnetron 5 is guide | induced in the heating chamber 1, and heats the food 4. The food 4 is also heated by radiant heat in a halogen heater (not shown) or the like. In relation to the magnetron 5, a blower fan 8 which blows out the air sucked from the air supply port 7 formed on the rear surface to the magnetron 5 is provided. The air after cooling the magnetron 5 is introduced into the heating chamber 1 through the intake duct 6.

Air in the heating chamber 1 is exhausted out of the heating chamber 1 from the rear exhaust port 9 on the left side and the rear exhaust port 10 on the right side. In connection with the exhaust port 10 on the right side, an exhaust duct plate 12 is provided which forms a flow path 15 for guiding air from the exhaust port 10 to the exhaust port 11 on the rear surface.

A second turn and shows the close-up configuration according to the exhaust duct plate 12, will present a second third degree turn in the arrow R ₁ direction. A hole 21 is formed in the rear surface 12α of the exhaust duct plate 12, and the peripheral edge portion of the hole 21 is spaced in the circumferential direction so that the cross section is approximately L-shaped accommodating portion 22 and the position thereof. Crystal projections 23 and 24 are formed.

In addition, a thin metal plate 25 of a disc shape, which is a thermal conductor, is protected by the housing portion 22 and fixed by the vis 26 in a state of being positioned by the positioning protrusions 23 and 24. The metal plate 25 is made of, for example, 42 aluminum alloy or stainless steel having good thermal conductivity, and has a thickness of about 0.1 mm.

In the metal plate 25, the bead-type thermistor 30 is formed in the depression formed in the center on the surface of the blower fan 8 side, in other words, on the opposite side of the flow path 15 of the air in the heating chamber 1. 27) is fixed in an adhesive state.

The lead wire 31 adhered to the bead-type thermistor 30 is guided to the outer space of the duct plate 12 through the holes 32 and 33. 34 is a plug for electrical connection with a control board other than the drawing.

In addition, the bead-type thermistor 30 has a small thermal time constant, for example, one second or less. Since the metal plate 25 is made of a material having good thermal conductivity, and is extremely thin, the metal plate 25 quickly transmits the thermal change to the thermistor 30.

4 shows an electric circuit configuration for heating control based on the output of the thermistor 30. The thermistor 30 is connected to the control board via the plug 34 from the lead wire 31. The control board is provided with a resistor R ₁ connected in series to the thermistor 30 and a resistor R ₂ connected in parallel with the thermistor 30.

Then, the parallel circuit of the thermistor 30 and the resistor R _2, the signal V _s appearing at the junction 40 of the resistors R ₁ is given to the AC amplifying circuit 41. The AC amplifier circuit 41 is configured to input a signal in which the DC component is removed from the capacitor C ₁ to the inverted amplifier circuit using the operational amplifier 42.

Therefore, the output signal V ₀ becomes a signal obtained by amplifying the AC component of the signal V _s . This output signal V ₀ is compared with the signal V _s described above in the comparison circuit 43. The output signal V _c of the comparison circuit 43 is provided to the microcomputer 44 which performs operation control of the magnetron 5 and the like.

That is, the microcomputer 44 performs heating control for the most suitable cooking based on the output signal V _c of the comparison circuit 43. FIG. 5 shows an example of signal waveforms of respective circuits of FIG. In Fig. 5 (a), the signals V _s1 and V ₀ are simultaneously shown, and in Fig. 5 (b), the signal V _c derived by the comparison circuit 43 is shown. The microwave output from the magnetron 5 is started from time t ₁ , and heating of the food 4 is started.

In the initial period of the heating start, the air passing through the flow path 15 formed by the exhaust duct plate 12 is dried. Since the heat capacity of the dry air is small, the signal V ₀ contains only a noise component which vibrates slightly.

The signal V _s is reduced according to the reduction in the resistance of thermistor 30 according to the temperature increase of the magnetron 5 and the heating chamber (1). If heating continues further, steam will be generated in the food 4. When this vapor is led to the flow path 15 and contacts the metal plate 25, the latent heat is applied to the metal plate 25.

Because of this latent heat, the metal plate 25 instantly rises in temperature, and the temperature vibrates like a harmonic signal. This temperature change is well transmitted to the thermistor 30. As a result, since the temperature of the thermistor 30 rises instantaneously, the signal V _s decreases momentarily, and the signal V ₀ obtained by inverting the AC component of the signal V _s rises momentarily. The rising width of the signal V ₀ increases with an increase in the amount of vapor in the air flowing through the distribution path 15, and eventually exceeds the signal V _s . As a result, at time t ₂ , the output signal V _c of the comparison circuit 43 is temporarily inverted to the low level (-5 V).

In response to the low level signal from the comparison circuit 43, the microcomputer 44 stops the generation of microwaves in the magnetron 5 to stop the heating. In this way, the heating can be stopped in a state where the amount of water vapor in the heating chamber 1 has reached a certain level.

In other words, the heating can be stopped automatically when the food 4 is brought into a predetermined completed cooking state by heating. In addition, since heating control is performed based on the output of the thermistor 30, detection of steam generation is not difficult due to vibration or the like as in the case of the prior art described above.

In addition, even if the heating chamber 1 is kept at a high temperature for a long time, the thermistor does not cause deterioration such as a superconducting element, so durability can be maintained satisfactorily.

In this way, it is possible to satisfactorily detect a certain completed cooking state of the food to achieve the most suitable heating control. Next, at the time point t ₃ after a short time interval from the time t _2, it simulates the case heating is performed again. In this case, the temperature in the vicinity of the metal plate 25 and the thermistor 30 becomes high because of the residual heat in the heating chamber 1. For this reason, since the difference between the temperature of the steam which passes through the circulation path 15 and the temperature of the thermistor 30 becomes small, the amplitude of the output signal V ₀ of the AC amplifier circuit 41 becomes small.

In other words, the steam detection sensitivity is lowered. However, because of the signal V _s when the temperature of the thermistor 30 is higher lowered signals V in a relatively small step to the amplitude of _zero, and a signal V ₀ over the signal V _s, the comparator circuit 43 at time t ₄ The output is inverted to the low level, and the heating is stopped.

In this way, the decrease in the sensitivity to vapor depletion due to the temperature rise is automatically compensated for by the decrease in the signal V _s . Therefore, even when the temperature in the heating chamber 1 is high, the detection of steam generation is not delayed, and automatically at the time when the food 4 is in a constant completed cooking state without depending on the temperature in the heating chamber 1. Heating can be stopped.

Further, the cooking condition of the food complete 4 can be changed by a combination of respective resistance values of the resistors R _1, R _2.

Therefore, when the resistance values of the resistors R ₁ and R ₂ are experimentally determined to obtain a completed cooking state most suitable for the conditions such as the volume of the heating chamber 1 or the microwave output, good heating control can be performed.

In addition, in the first embodiment, the AC amplifier circuit 41 is constituted by an inverted amplifier circuit to compensate for the decrease in the steam detection sensitivity when the temperature of the heating chamber 1 rises. Output signal V ₀ is compared with the signal V _s corresponding to the DC component of the thermistor 30 output.

However, when the decrease in the steam detection sensitivity is not a problem, the output signal V ₀ may be level-divided at a constant voltage level, and the AC amplifying means does not have to be constituted by an inverting amplifier circuit.

In addition, in the above-mentioned first embodiment, although the circulation path 15 through which the air in the heating chamber 1 flows is formed by the exhaust duct plate 12 or the like, such a distribution path does not need to be particularly provided. For example, the metal plate 25 may be disposed to face the inside of the heating chamber 1.

Moreover, thermistors with a small thermal time constant other than the bead type thermistor may be used. In addition, various setting changes can be made without changing the gist of the present invention. Next, the main part of the microwave oven in 2nd Example of this invention is demonstrated.

In addition, the same code | symbol is written in the same part as 1st Example, and the description is abbreviate | omitted. 6 and 7 show a configuration near the thermistor 30.

In the metal plate 25, the bead-type thermistor 30 is disposed in a position where the recessed center of the surface is opposite to the flow path 15 of the air in the heating chamber 1. In this case, the thermistor 30 is positioned. The heat-resistant polyimide tape 50 having a thickness of 10 µm is fixed to the metal plate 25 in close contact with the depressions. Both ends of the tape 50 are folded back to the inner surface (the flow path 15 side) of the metal plate 25 so that they do not fall off.

In addition, the lead wire 31 of the thermistor 30 is fastened and fixed together by the binder 52 to the protrusion 51 formed integrally with the metal plate 25.

In such a configuration, since the thermistor 30 is in close contact with the metal plate 25, the thermal conductivity between the thermistor 30 and the metal plate 25 can be stably maintained at a desired value, and the steam detection performance is stabilized. Since the heat radiation amount by the tape 50 can also easily manage the thickness of the tape 50, it can maintain it at a predetermined value, and the steam detection performance is stabilized also in this advantage.

In addition, the microwave oven according to the third embodiment of the present invention will be described with reference to FIGS. 8 and 9 show the structure of the microwave oven. A heating chamber 60 is provided inside the microwave oven. In this heating chamber 60, the heating of the food 63 on the turntable 62 is performed by the microwaves supplied from the magnetron 61, and the halogen heater. Heating is also performed by radiant heat in (not shown) or the like.

A cooling fan 64 is provided at the rear of the magnetron 61, and the outside air is driven into the rear air intake holes 65, 65 by driving of the cooling fan 64. It is sucked in from and the cooling wind is provided to the magnetron 61. The cooling air after magnetron cooling is carried out in the intake holes 66, 66 near the front wall of the heating chamber. The exhaust holes 67 and 67 on the left side wall of the heating chamber together with the atmosphere containing the vapor generated from the food upon heating. A small amount of exhaust holes 69, 69... Of the heating chamber upper wall 68. From the heating chamber.

The exhaust holes 69 and 69. The exhaust duct 72 formed of the heating chamber upper wall 68, the microwave oven outer wall 70, and the packing 71 is provided.

In the exhaust duct 72, the exhaust holes 69, 69,. Exhaust ducts 73 are provided to restrict the circumference. The exhaust duct 72 receives a part of the cooling wind in the cooling fan 64 through the exhaust holes 69, 69. And then to the cooling fan 64 in accordance with the action of the suction force of the cooling fan 64.

And a small amount of the wind accompanied by the atmosphere containing steam in the food attracted by the cooling wind flow in the exhaust duct 72 is the exhaust holes 69, 69. And the cooling air in the exhaust duct 72 passes through the small exhaust duct 73.

A portion of the upper wall of the small exhaust duct 73 is formed by the detection means 74. This detecting means 74 is in contact with the atmosphere in the heating chamber passing through the small exhaust duct 73 on one side, that is, the bottom surface, and detects information of this atmosphere, namely steam. The other surface, that is, the upper surface, is in contact with the cooling wind passing through the exhaust duct 72.

The details of the detecting means 74 are as shown in FIGS. 10 and 11. A thin plate-shaped printed circuit board 75 having a thickness of 0.5-0.8 mm made of a glass epoxy plate is provided. The lower surface of the printed board 75 is coated with copper foil 76 over the entire surface as shown in FIG. Copper foils 77 and 78 are coated in two broad areas, such as 10 degrees.

The entire surface of the copper foil 76 on the lower surface side is protected by a thin resist film, and the small regions 79 and 78 on which the copper foils 77 and 78 on the upper surface side are also exposed near the center of the printed circuit board 75. 80) is covered and covered with a resist film.

Moreover, the lead wires 81 and 82 are couple | bonded with the edge part of these copper foils 77 and 78. As shown in FIG.

A chip thermistor 83 is soldered to the small areas 79 and 80 of the two copper foils 77 and 78 near the center of the upper surface of the printed board 75 over this small area.

FIG. 12 shows a circuit including the detection means 74. A resistor 84 is connected in series with the thermistor 83 of the detection means 74, and a connection point between the thermistor 83 and the resistor 84 is shown. variation of the voltage V _s this DC component is removed, and the capacitor 85, be amplified by the AC amplifier 86 is obtained, the output V _0. This output V ₀ is input to the microcomputer 87 incorporating the A / D converter.

In this case, in the detection means 74, the atmosphere in the heating chamber passing through the initial heating stage and the small exhaust duct 73 is in a dry state, and the latent heat (heat capacity) is small, and the variation of the voltage V _s is small. .

And, referring to the characteristics of the output V ₀ of the output of the detection means 74 shown in the Figure 13, the output V ₀ in a range that is about a little under the influence of vibration noise. When heating proceeds and steam is generated in the food and the steam is included in the atmosphere in the heating chamber passing through the small exhaust duct 73, the printed circuit board 75 of the detecting means 74 is temporarily heated by the latent heat of the steam. rise is transmitted to the temperature change on the thermistor 83 is instantaneous, the thermistor 83 is to increase the temperature voltage V _s is lowered temporarily to the output V ₀ temporarily rises. The increase in output V ₀ increases with the increase in the amount of steam.

The microcomputer 87 controls the heating by driving the magnetron 61 or the halogen heater based on this output V ₀ according to the output of the detection means 74, and heating the output when the output V ₀ exceeds a preset setting level VE. To exit.

In this configuration, the thermistor 83 is soldered to the printed circuit board 75, and the soldering area thereof is limited to the small regions 79 and 80, which are part of the non-resist film, and is constant. The heat conduction performance between the thermistor 83 and the printed circuit board 75 can be stably maintained at a desired hammer, and the detection means 74 is stable in detection performance and easily mass-produced.

In addition, the printed circuit board 75 absorbs the latent heat of the steam well by the copper foil 76 coated on the front surface of the lower surface of the side in contact with the atmosphere of the heating chamber, and the steam detection sensitivity of the detection means 74 is improved. do.

In addition, the thermistor 83 is soldered to the upper surface of the printed circuit board 75, so that the thermistor 83 is difficult to come into contact with the heating chamber atmosphere, so that poor insulation or the like does not occur. As described above, according to the present invention, in a heating cooker in which food stored in a heating chamber is heated by a heating means, a heat conductor in contact with the air in the heating chamber, a thermistor disposed in contact with the thermal conductor, and AC amplifying means for extracting and amplifying the output AC component, and control means for controlling the heating means based on the output of the AC amplifying means, so that good heating control corresponding to the completed cooking state of the food can be realized. .

In addition, since the humidity sensor is not used, other configurations such as heat for cleaning the humidity sensor can be omitted, thereby simplifying the configuration. In addition, since the thermistor does not have the same piezoelectricity as that of a superconducting element, noise for vibration and shock does not occur.

In addition, the thermistor does not cause deterioration even if the high temperature state is continued for a long time. In addition, since the heat conductor is composed of a thin metal plate and the thermistor is a bead type thermistor, the temperature change due to latent heat is quickly transmitted to the thermistor, thereby improving the detection sensitivity of steam.

In addition, since the thermistor is arranged on the surface of the thermal conductor that is not in contact with the air in the heating chamber, the thermistor does not come into contact with the air in the heating chamber. .

In addition, since a comparison means for comparing the output of the AC amplifying means with the output of the thermistor before entering the AC amplifying means and outputting the comparison result to the control means is provided, even if there is residual heat in the heating chamber, Deterioration of the steam detection sensitivity can be controlled.

In addition, since the bead-type thermistor is adhered to the metal plate in a state of being in close contact with a tape such as heat-resistant phylimide, it is possible to stably maintain the thermal conduction performance between the bead-type thermistor and the metal plate to stabilize steam detection performance. You can do it.

In addition, since the thermal conductor is composed of a thin printed circuit board, the thermistor is a chip thermistor, and the chip thermistor is soldered to the printed board, the thermal conduction performance between the chip thermistor and the printed board is stably maintained. Similarly, the steam detection performance can be stabilized.

In addition, the copper substrate is coated on one side of the printed board entirely, and the chip thermistor is soldered on the other side, and one side of the printed board is in contact with the air in the heating chamber. It is possible to improve the detection sensitivity of the steam by absorbing the latent heat of the steam well by the copper foil coated on the surface facing the atmosphere. In addition, the chip-type thermistor is soldered to the other side of the printed board, which makes it difficult to contact the air in the heating chamber and does not cause poor insulation due to the influence of steam or the like.

In addition, since the printed board is formed of a glass epoxy board which absorbs the latent heat of steam well, the detection sensitivity of the steam can be further improved.

Claims (9)

In the heat cooking apparatus which heats the food 4 accommodated in the heating chamber 1 by the heating means 5, The heat conductor 25 which contact | connects the air in the heating chamber 1, and this heat conductor 25 Control means for controlling the heating means (5) based on the thermistor (30) disposed in contact with the control element, an AC amplification means for extracting and amplifying the AC component output from the thermistor (30), and the output of the AC amplification means. Heat cooker comprising (44). The heating cooker according to claim 1, wherein the heat conductor (25) is made of a thin metal plate, and the thermistor (30) is a bead type thermistor. The heating cooker according to claim 1, wherein the thermistor (30) is arranged on a surface of the heat conductor (25) which is not in contact with air in the heating chamber (1). 2. A comparison means (43) according to claim 1, wherein an output of said AC amplification means and said thermistor (30) before entering said AC amplification means are provided, and a comparison means (43) for outputting the comparison result to said control means (44) is provided. Heat cooker characterized in that. The heating cooker according to claim 2, wherein the bead-type thermistor (30) is attached to the metal plate (25) in close contact with a tape (50). The heat cooker according to claim 5, wherein the tape (50) is a heat resistant polyimide tape. 2. The thermally conductive material (25) according to claim 1, comprising a thin printed circuit board (75), the thermistor (30) being a chip thermistor (83), and the chip thermistor (83) being the printed circuit board (75). Heat cooker characterized in that soldered to. 8. The printed circuit board (75) according to claim 7, wherein the printed circuit board (75) covers the entire surface of the copper foil (76), and at the same time solders the chip thermistor (83) to the other surface. Heating cooker, characterized in that in contact with the air of the heating chamber (1). The heating cooker according to claim 7, wherein the printed board (75) is a glass epoxy board.