JPH09171891A - Microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely measure the temperature of a matter to be heated by changing the inclination of an equipment body so that the matter to be heated is situated within the field-of-view range of a concave mirror, holding a radiant heat sensor at a fixed temperature, and correcting it to a secular change. SOLUTION: A magnetron 19 set within a heating chamber 17 heats a matter to be heated on a turn table 15. A radiant heat sensor 11 is set in the opening 21 on the upper wall surface of the heating chamber 17, and a concave mirror 13 for reflecting and converging the infrared ray emitted from the matter to be heated and thermistors TH1, 2 are provided within a housing 12. The inclination of the housing 12 is changed by a cam mechanism 14 with a support shaft 22 as axis in heating, fixed in a direction where the output of the radiant heat sensor 11 is maximum, so that the matter to be heated is situated within the field-of-view range of the concave mirror 13. When the ambient temperature is stabilized, the temperature difference between the thermistors TH1, 2 is eliminated to stabilize the output of the radiant heat sensor 11. The temperature of the radiant heat sensor 11 is held constant by the heating element 16 of the housing 12 and corrected to a secular change by the heating body 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven which detects infrared rays radiated from an object to be heated, measures the temperature of the object to be heated, and controls heating to the object to be heated based on the temperature information. It is a thing.

[0002]

2. Description of the Related Art Conventionally, a microwave oven with a heating control function measures the temperature of an object to be heated by detecting infrared rays radiated from the object to be heated, and heats the object to be heated based on the temperature information. To control. This prevents insufficient or excessive heating of the object to be heated, and finishes heating the object to be heated when finished.

There are various types of infrared detectors,
It is mainly classified into a quantum sensor and a thermal effect sensor. The quantum sensor utilizes the photoelectric effect of semiconductors and has high measurement accuracy and good response, but has the drawbacks that the wavelength range of light to be detected is narrow and it cannot be used at room temperature. Therefore, it is difficult to use the quantum sensor as an infrared detector in a microwave oven.

On the other hand, the thermal effect type sensor absorbs infrared rays, converts them into heat, and detects the heat.
Although the response is inferior to that of the quantum sensor, it has a simple structure, excellent mechanical strength, a wide wavelength range of light to be measured, and can be used at room temperature. The thermo-effect type sensor is a thermo-electric stack type using a thermo-electric stack (thermopile) in which a number of small thermocouples are connected in series, a pyro-electric type using the pyro-electric effect,
There is a thermistor bolometer type that utilizes the change in conductivity of the thermistor.

The thermoelectric stack type is widely put into practical use as a radiation thermometer, but the thermoelectric stack element is expensive. In the pyroelectric type, the pyroelectric element is relatively inexpensive, but a chopper mechanism that intermittently irradiates infrared rays is required, and the measurement system becomes expensive. The thermistor bolometer type is composed of two thermistors and a condenser for reflecting and condensing infrared rays radiated from an object to be heated, and is relatively inexpensive.

As shown in FIG. 7, the thermistor bolometer comprises a thermistor TH1 and TH2 having negative characteristics and uniform characteristics, and resistors R1 and R2, which are assembled in a bridge circuit 25. The high-precision differential amplifier circuit 7 is provided at the midpoint between the thermistor TH1 and the thermistor TH2 and the midpoint between the resistors R1 and R2.
Is connected.

The thermistor TH1 is adapted to irradiate the infrared rays collected by the condensing part, and the thermistor TH2 for compensation.
Is provided so that its infrared rays are not irradiated in the vicinity thereof. The constant voltage V is applied, and the midpoint voltage VT of the thermistor TH1 and thermistor TH2 at this time, the resistance R1 and the resistance R2.
When the midpoint voltage VR is set, the output voltage V2 of the high-precision differential amplifier circuit 7 becomes an amplified voltage of the difference between VT and VR.

As the amount of infrared radiation applied to the thermistor TH1 increases, the difference between VT and VR increases due to radiant heat, resulting in a voltage V2.
Also increases. The irradiation amount of infrared rays has a relationship of increasing as the temperature of the object to be heated rises, and the voltage V2 can be treated as information on the temperature of the object to be heated. In the microwave oven, when the output voltage V2 reaches a preset voltage,
The heating of the object to be heated is completed.

However, the output voltage V2 is greatly influenced by the ambient temperature, and if it is not taken into consideration, the temperature of the object to be heated cannot be measured accurately. In particular, even a slight difference in the characteristics of the two thermistors causes a problem of temperature drift in which the voltage V2 shifts due to a change in ambient temperature and correct results cannot be obtained. In a microwave oven, the thermistor bolometer is difficult to handle because the ambient temperature and the temperature of the object to be heated fluctuate greatly due to the heating of the object to be heated.

[0010]

Although the method of detecting radiant heat with a radiant heat sensor of thermistor bolometer type is relatively inexpensive, it is difficult to use in a microwave oven. In order to eliminate the temperature drift, two thermistors with extremely uniform characteristics may be used, but for this reason, the production yield is unavoidably deteriorated.

Further, the output of the radiant heat sensor is a minute voltage in the unit of μV, and the S / N ratio is poor because this is amplified by the high precision operation amplifier at a high magnification. Further, the amount of infrared rays radiated from the object to be heated is related to the size and shape of the object to be heated.
There is a problem that the output of the radiant heat sensor changes depending on the size and shape of the object to be heated, and an accurate measured value cannot be obtained. Further, the output of the radiant heat sensor may change due to the secular change of the characteristics of the thermistor and the secular change of the condensing power of the condensing part, and similarly, an accurate measured value may not be obtained.

The present invention solves such a problem and is relatively inexpensive and is not affected by changes in ambient temperature, changes in the characteristics of the thermistor, changes in the focusing power of the condensing section, and the object to be heated. An object of the present invention is to provide a microwave oven which measures a temperature with high accuracy and appropriately heats an object to be heated.

[0013]

In order to achieve the above object, in the first configuration of the present invention, the object to be heated is detected by a radiant heat sensor for detecting infrared rays radiated from the object to be heated placed in the heating chamber. In a microwave oven which measures temperature and controls heating to the object to be heated based on the temperature information, the radiant heat sensor is a bolometer type using a temperature sensitive element, and an ambient temperature for measuring an ambient temperature of the radiant heat sensor. Measuring means is provided, and the output of the radiant heat sensor is corrected based on the output of the ambient temperature measuring means.

With this structure, the infrared radiation emitted from the object to be heated is detected by the radiation heat sensor. The voltage output from the radiant heat sensor increases as the amount of infrared rays increases. The amount of infrared rays increases as the temperature of the object to be heated increases. Thereby, the voltage output from the radiant heat sensor can be treated as the temperature of the object to be heated.

However, since the radiant heat sensor using the temperature sensitive element also reacts to the ambient temperature, its output contains the ambient temperature component. Therefore, the ambient temperature measuring means measures the ambient temperature of the radiant heat sensor and removes the ambient temperature component from the output of the radiant heat sensor based on the ambient temperature information. As a result, the temperature of the object to be heated can be obtained with high accuracy. The heating of the object to be heated is controlled based on this temperature information.

According to the present invention, in addition to the above structure,
A control means for controlling the position of the radiant heat sensor so as to change the direction of the entrance of the radiant heat sensor is provided, and the control means is provided at a position where the output of the radiant heat sensor is maximized when the object to be heated is heated. A radiant heat sensor is provided.

According to this structure, when the object to be heated does not exist in the direction of the entrance of the radiant heat sensor, the output of the radiant heat sensor is small, so that the object to be heated enters in the direction of the entrance. The position of the radiant heat sensor is automatically controlled. Then, by selecting the direction in which the output of the radiant heat sensor is maximized, the output of the radiant heat sensor is related only to the temperature of the object to be heated, regardless of the size or shape of the object to be heated.

In addition, in the first structure of the present invention, the radiant heat sensor further includes a housing having the temperature sensing element built-in and a condensing section for guiding incident infrared rays to the temperature sensing element. Therefore, the housing is further provided with a heating element, and the heating element keeps the temperature of the radiant heat sensor constant by heating the heating element.

With such a structure, the housing is kept at a constant temperature by the heating element. Therefore, as can be seen from FIG. 3 described later, the temperature drift of the temperature sensitive element in the radiant heat sensor configured by using two temperature sensitive elements can be suppressed.

Further, the present invention has the above-mentioned constitution, and further,
A heating element having a predetermined heating temperature is provided at a predetermined position near the object to be heated, and the heating temperature of the heating element is measured by the radiant heat sensor to correct the output of the radiant heat sensor.

According to this structure, the radiant heat sensor output can be corrected with respect to the secular change that gradually changes under the same temperature condition, and the measurement accuracy can be maintained.

Further, according to the present invention, in each of the above-mentioned configurations, the radiant heat sensor is further mounted near an intake port provided in the heating chamber for air circulation.

According to this structure, when the object to be heated is food, steam generated by being heated,
The amount of oil, dirt, and the like is small near the intake port because air flows in from the outside of the heating chamber. By mounting the radiant heat sensor in the vicinity of the intake port, the radiant heat sensor is less likely to receive steam, oil, dirt, etc., and deterioration of measurement accuracy of the radiant heat sensor is prevented.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, a magnetron 19 is attached to the heating chamber 17. Magnetron 19
Is a device for generating a microwave, and the object to be heated is heated by the irradiation of the microwave. The object to be heated is placed on the turntable 15.

The turntable 15 continues to rotate during the heating operation, and the object to be heated is heated while being rotated. When the object to be heated is food, steam, oil, dirt, etc. are generated. In order to prevent this steam and the like from staying in the heating chamber 17, the intake port 20
The air outside the heating chamber 17 is introduced in the direction of the arrow 29. This uses the cooling blast of the magnetron 19.
An opening 21 is provided in the vicinity of the intake port 20 on the upper wall surface of the heating chamber 17, and the radiant heat sensor 11 is attached.

In the vicinity of the intake port 20, the air outside the heating chamber 17 flows in the direction of the arrow 29, so that the amount of steam, oil, dirt, etc. generated from the object to be heated is reduced. This prevents the measurement accuracy of the radiant heat sensor 11 from deteriorating due to steam, oil, dirt, and the like. The radiant heat sensor is the housing 12
The concave mirror 13 that reflects and collects the infrared rays emitted from the object to be heated inside the chamber, and the thermistor T that emits the infrared rays.
H1 and a compensating thermistor TH2 that does not emit infrared rays are provided.

The two thermistors TH1 and TH2 are thermistors having negative characteristics and almost the same characteristics. The concave mirror 13 narrows the viewing angle so that the amount of infrared rays collected is not affected by the size or shape of the object to be heated, and adjusts the radial axis of the turntable 15 in the direction of viewing. For example, if the viewing angle is 14 degrees, the area diameter is 50 mm when the distance is 200 mm. As a result, the infrared rays only in the portion entering the viewing angle area as shown by the arrow 30 are reflected and condensed, and the sensitivity becomes stable.

However, the object to be heated has various sizes and shapes, and depending on the object to be heated, it may not be well within the field of view of the concave mirror 13. Therefore, the tilt of the housing 12 is changed by the cam mechanism 14 around the support shaft 22 during heating.
At this time, the field of view of the concave mirror 13 moves on the radial axis of the turntable 15 and is fixed in a direction in which the output of the radiant heat sensor 11 is maximized. As a result, the object to be heated enters the visual field area.

The output of the radiant heat sensor 11 is determined by the temperature of the object to be heated, and the temperature measurement becomes accurate. Also, the housing 12
A heating element 16 is attached to the radiant heat sensor 11, and the radiant heat sensor 11 is kept at a constant temperature.

The stabilization of the ambient temperature prevents a temperature difference from occurring between the thermistor TH1 and the thermistor TH2 and stabilizes the output of the radiant heat sensor. Even if the ambient temperature of the thermistors TH1 and TH2 is constant, the concave mirror 1
If the temperature of 3 changes, the amount of infrared rays radiated from the concave mirror 13 changes, and the output of the radiant heat sensor 11 changes. The thermistors TH1 and TH2 and the concave mirror 13 are kept at a constant temperature by the heating element 16, and such noise generation is suppressed.

Even when the object to be heated is being heated, the temperature of the radiant heat sensor 11 becomes constant, so that the temperature drift of the output of the radiant heat sensor 11 is prevented. Further, the heating element 18 having a constant heating temperature is provided in the range corner portion beside the turntable 15. When the microwave oven is not used, the heating element 18 generates heat, for example, 2 hours after the use. By measuring the temperature with the radiant heat sensor 11, the aging of the characteristics of the thermistors TH1 and TH2 and the output change of the radiant heat sensor 11 due to the aging of the condensing power of the concave mirror 13 are corrected.

Next, a method of measuring the internal circuit of the radiant heat sensor 11 and the temperature of the object to be heated will be described. As shown in FIG. 2, in the radiant heat sensor 11, a thermistor TH1 that receives infrared rays radiated from an object to be heated and a thermistor TH2 for compensation are connected in series, and a resistor R1 and a resistor R2 are connected in series. The bridge circuit 25 is assembled by connecting them in parallel.

The resistor R3, the PNP transistor section 5, and the NPN transistor section 6 are connected to the bridge circuit 25, and the power supply voltage V is applied to the entire circuit. The difference between the midpoint VT of the thermistor TH1 and the thermistor TH2 and the midpoint voltage VR of the resistors R1 and R2 is amplified by the high precision differential amplifier circuit 7 and output from the radiant heat sensor 11 as the voltage V2. The voltage V2 is input to the microcomputer 4, converted into a digital signal by the A / D converter 26, and stored in the RAM 2.

The midpoint voltage V1 of the bridge circuit 25 and the resistor R3 is output from the radiant heat sensor 11. The voltage V1 is input to the microcomputer 4, converted into a digital signal by the A / D converter 27 and stored in the RAM 1. The characteristic data of the radiant heat sensor 11 is checked in advance and incorporated in the hardware output means 8. The output characteristic data is stored in the E ² ROM 9. The arithmetic processing unit 3 has a voltage V
1, the voltage V2 and the characteristic data are input to calculate the temperature of the object to be heated.

When a heating instruction is given to the microcomputer 4 from the operation section 23, the arithmetic processing section 3 operates the turntable 15 and the magnetron 19 to start heating the object to be heated. A high level signal and a low level signal are periodically and alternately output from the I / O output 10. The cam mechanism 14 is controlled by the arithmetic processing unit 3 during heating, and the visual field area of the radiant heat sensor 11 moves to a position where the output of the radiant heat sensor 11 is maximized.

The arithmetic processing unit 3 calculates the temperature of the object to be heated, and when the temperature reaches a predetermined set temperature, the operations of the turntable 15 and the magnetron 19 are stopped, and the heating of the object to be heated is completed. Further, after the heating of the object to be heated is completed, the heating element 18 having a predetermined heat generation temperature generates heat 2 hours later, and the temperature is similarly measured by the radiant heat sensor 11, so that the secular change in the characteristics of the radiant heat sensor 11 can be examined. E ² R
It is stored in OM9.

A high level signal and a low level signal are periodically and alternately output from the I / O output 10. I / O
The PNP transistor unit 5 and the NPN transistor unit 6 connected to the output are turned on and off by the signal. In the case of a high level signal, the radiant heat sensor 11
Becomes a mode for detecting radiant heat, and the voltage V2 representing the temperature of the object to be heated is stored in the RAM2.

This will be referred to as <sensor mode>. On the other hand, in the case of the low level signal, the radiant heat sensor 11 is in a mode for measuring the ambient temperature, the voltage V1 is output from the radiant heat sensor 11, and is stored in the RAM 1.
This will be referred to as <ambient temperature mode>. In this way, the <sensor mode> and the <ambient temperature mode> are alternately repeated.

For example, if the High level and the Low level are switched at intervals of 0.5 seconds, the arithmetic processing unit is based on the voltage V2 of the <sensor mode> and the voltage V1 of the <ambient temperature mode> every 1 second. 3 calculates the temperature of the object to be heated. This will be referred to as <calculation mode>. Less than,
Each mode will be described.

<Sensor mode> Hi from I / O output 10
This is the mode when the gh level signal is output. Hig
The h-level signal turns on the NPN transistor unit 6 and turns on the PNP transistor unit 5. As a result, the constant voltage V is applied to the bridge circuit 25. The thermistor TH1 is irradiated with infrared rays radiated from an object to be heated,
The electric resistance is slightly reduced by the irradiation heat.

Therefore, the midpoint voltage VT of the thermistors TH1 and TH2 slightly rises. Its voltage V
By amplifying the difference between the midpoint voltage VR of T, the resistance R1 and the resistance R2 by the high precision differential amplifier 7, the output voltage V2 thereof also rises. This voltage V2 rises as the amount of infrared rays radiated from the object to be heated increases, and the amount of infrared rays radiated from the object to be heated increases as the temperature of the object to be heated increases. Thereby, the voltage V2 can be processed as an amount representing the temperature of the object to be heated.

<Ambient temperature mode> L from I / O output 10
This is the mode when the ow level signal is output. Low
The level signal turns off the NPN transistor unit 6 and turns off the PNP transistor unit 5. As a result, the power supply voltage V is applied to the resistor R3 and the bridge circuit 25.

The resistance values of the thermistors TH1 and TH2 are RTH1 and RTH2, respectively. When the ambient temperature of the radiant heat sensor 11 rises, both resistance values RTH1 and RTH2 decrease. The resistance values RTH1 and RTH2 at this time are determined by the ambient temperature and follow the following basic formula of the thermistor.

[0044]

[Equation 1]

Here, B is a constant specific to the thermistor, R
_S is the resistance value at the temperature T _S ° C, and R is the resistance value at the temperature T ° C.

When the ambient temperature rises, the resistance values RTH1 and RTH2 of the thermistor decrease, and the resistance value of the entire bridge circuit 25 decreases. As a result, the resistor R3 and the midpoint voltage V1 of the bridge circuit drop. Thus, voltage V1 represents ambient temperature. The ambient temperature T is obtained by solving this in reverse.

[0047]

[Equation 2]

That is, when the resistance value R of the thermistor is given, the ambient temperature T is obtained. In the present embodiment, by utilizing the fact that the thermistor TH1 and the thermistor TH2 have almost the same characteristics, their respective resistance values RTH1 and RTH are used.
The ambient temperature T is calculated by taking the average of 2. This allows
The ambient temperature T can be obtained more accurately. Therefore, equation (2)
Substitute the following value into.

R _S = R _STH1 + R _STH2 (3) R = RTH1 + RTH2 (4) B = (B _TH1 + B _TH2 ) / 2 (5)

Here, R _STH1 is the resistance value of the thermistor TH1 at the temperature T _S ℃, R _STH2 is the resistance value of the thermistor TH2 at the temperature T _S ℃, B _TH1 is the B constant of the thermistor TH1,
B _TH2 is the B constant of the thermistor TH2, R TH1 is the resistance value of the thermistor TH1 during measurement, and R TH2 is the resistance value of the thermistor TH2 during measurement. In the circuit shown in FIG. 2, RT
H1 + RTH2 is expressed by the following equation using the power supply voltage V and the voltage V1.

[0051]

(Equation 3)

As described above, the arithmetic processing unit 3 can immediately calculate the ambient temperature by inputting V1 stored in the RAM1.

<Calculation Mode> Every time one second elapses, the calculation processing unit 3 inputs the voltage V1 representing the ambient temperature, the voltage V2 representing the temperature of the object to be heated, and the characteristic data stored in the E ² ROM 9. Calculate the temperature of the object to be heated.

The voltage V2 when there is no object to be heated is B _TH1 = B
_In the case of _TH2 , the output is constant with respect to the ambient temperature as in VA shown in FIG. However, when the B constant values are slightly deviated from each other, the voltage V2 drifts like VB and VC and is output. When B _TH1 > B _TH2 , the voltage V2 is output as VB, and when B _TH1 <B _TH2 , the voltage V2 is output as VC.

FIG. 4 shows the temperature characteristic of the object to be heated at the voltage V2. If the ambient temperature is constant and B _TH1 ≠ B _TH2 ,
Even if it is output like VA ′, if there is a slight change in ambient temperature, the voltage V2 drifts like VB ′ and VC ′ and is output. In order to eliminate such a problem, the arithmetic processing unit 3 makes the following corrections. The voltage V2 basically shows a characteristic proportional to a value obtained by subtracting the ambient temperature from the temperature of the object to be heated, as shown in FIG. Thereby, the ambient temperature correction formula (7) is established.

(Temperature to be heated) = a × V2 + b + (ambient temperature) (7) Here, a and b are constants. The ambient temperature is calculated based on the voltage V1 by the method described above. Further, temperature drifts such as VB ′ and VC ′ shown in FIG. 3 are corrected by taking the gradient into consideration. That is, the voltage V2 is corrected according to the following equation, and then substituted into the ambient temperature correction equation (7).

V2 → V2- (Δ ambient temperature) × (temperature drift gradient) × (amplification factor) (8) Here, Δ ambient temperature is amplified by the change amount of the ambient temperature at a certain fixed time interval. The rate is the amplification rate of the high precision differential amplifier circuit 7. The temperature drift gradient is investigated in advance and incorporated in the hardware output means 8. This correction is a correction of subtracting an increase in temperature drift at a certain fixed time interval from the voltage V2 output from the radiant heat sensor 11. Usually, the temperature drift gradient is a minute value and is an effective correction.

In this way, the voltage V1, the voltage V2, and Δ
Given the ambient temperature, the temperature drift gradient, and the constants a and b, the arithmetic processing unit 3 corrects the ambient temperature and corrects the B
Correct the manufacturing variation by a constant number. As shown in FIG. 6, the voltage V2 and the temperature of the object to be heated are uniquely determined by the correction,
Highly accurate temperature measurement is possible. Further, as shown in FIG. 1, the radiant heat sensor 11 is provided with a heating element 16, and the temperature of the radiant heat sensor 11 is kept at a certain constant temperature, whereby the temperature drift is suppressed.

Further, the secular change of the characteristics of the thermistors TH1 and TH2 and the secular change of the condensing power of the concave mirror 13 are corrected by using the heating element 18 having a constant heat generation temperature. The corrected characteristic data is stored in the E ² ROM 9. For example, even in the measurement of the predetermined heat generation temperature, it is conceivable that oil adheres to the surface of the concave mirror 13 to reduce the light collecting power and the output of the radiant heat sensor 11 becomes small.

In this case, since the sensitivity is lowered, the constant a may be changed to a small value. By accurately measuring the temperature of the object to be heated during heating to the object to be heated in this way, the object to be heated is automatically heated when it reaches a predetermined set temperature. By finishing the heating, shortage or excess of heating is prevented, and the object to be heated is finished in an appropriate temperature state.

[0061]

【The invention's effect】

<Effect of claim 1> The temperature of the object to be heated can be measured with high accuracy at a relatively low cost. The heating of the object to be heated is controlled based on the measured temperature of the object to be heated, and the object to be heated is heated to an appropriate temperature state. Further, it can be widely applied as a non-contact temperature measuring device other than the microwave oven.

<Effect of Claim 2> The output of the radiant heat sensor is maximized and the S / N ratio is improved. Further, the object to be heated can be accurately measured regardless of the shape and size of the object to be heated.

<Effect of Claim 3> The temperature drift of the temperature sensitive element in the radiation heat sensor constructed by using two temperature sensitive elements is suppressed, and the measurement accuracy is improved.

<Effect of Claim 4> The output of the radiant heat sensor can be corrected for the secular change which changes gradually even under the same temperature condition, and the measurement accuracy is maintained.

<Effect of Claim 5> The radiant heat sensor hardly receives steam, oil, filth, etc. generated from the object to be heated, and prevents deterioration of measurement accuracy due to steam, oil, filth, etc.

[Brief description of the drawings]

FIG. 1 is a sectional view of a microwave oven according to an embodiment of the present invention.

FIG. 2 is a basic circuit diagram thereof.

FIG. 3 is a characteristic diagram showing the temperature drift.

FIG. 4 is a temperature characteristic diagram of the object to be heated.

FIG. 5 is a characteristic diagram of (temperature of an object to be heated-ambient temperature) -output voltage.

FIG. 6 is a diagram showing the relationship between the measured object temperature after drift correction and the output voltage.

FIG. 7 is a circuit diagram of a conventional thermistor bolometer in a microwave oven.

[Explanation of symbols]

1 RAM 2 RAM 3 arithmetic processing unit 4 microcomputer 7 high precision differential amplifier 9 E ² ROM 10 I / O output 11 radiant heat sensor 12 housing 13 concave mirror 14 cam mechanism 16 heating element 17 heating chamber 18 heating element 19 magnetron TH1 thermistor TH2 Thermistor

Claims (5)

[Claims] 1. The temperature of the object to be heated is measured by a radiant heat sensor which detects infrared rays radiated from the object to be heated placed in the heating chamber, and heating of the object to be heated is controlled based on the temperature information. In the microwave oven, the radiant heat sensor is a bolometer type using a temperature sensitive element, an ambient temperature measuring means for measuring the ambient temperature of the radiant heat sensor is provided, and the output of the radiant heat sensor is based on the output of the ambient temperature measuring means. A microwave oven that is characterized by being corrected. 2. A control means for controlling the position of the radiant heat sensor so as to change the direction of the entrance of the radiant heat sensor is provided, and the control means maximizes the output of the radiant heat sensor when the object to be heated is heated. The microwave oven according to claim 1, wherein the radiant heat sensor is brought to a position where 3. The radiant heat sensor includes a housing having a portion containing the temperature sensing element and a light collecting portion for guiding incident infrared rays to the temperature sensing element, and the heating element is further provided in the housing. The microwave oven according to claim 1, wherein the temperature of the radiant heat sensor is kept constant by heating it. 4. An output of the radiant heat sensor is corrected by providing a heat generating element having a predetermined heat generating temperature at a predetermined position near an object to be heated and measuring the heat generating temperature of the heat generating element with the radiant heat sensor. The microwave oven according to claim 1 or claim 2 or claim 3, characterized in that. 5. The radiant heat sensor is attached in the vicinity of an intake port provided for air circulation in the heating chamber, according to claim 1, 2, 3 or 4. microwave.