JP2989418B2 - Humidity detector of cooking device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the humidity of a cooking device, and more particularly, to automatically controlling the heating output based on the amount of water vapor or the like discharged from food in a heating room of the cooking device. The present invention relates to a humidity detector for a cooking device.

[0002]

2. Description of the Related Art Conventionally, for example, there has been a microwave oven that automatically performs cooking by controlling heating output based on the amount of water vapor or the like emitted from food. In other words, near the completion of heating, a large amount of water vapor and the like will emanate from the food.Therefore, a temperature sensor that detects the water vapor and the like discharged from the heating chamber is provided, and the magnetron is operated based on the electric signal from the temperature sensor. This is a configuration for controlling the output. For example, JP-A-60-32288 discloses that
As a proposal of the present applicant, a heating cooker that includes two temperature-sensitive resistors as a humidity sensor and exposes one to the atmosphere, and one has a sealed structure and performs absolute humidity detection from each resistance ratio to perform heating control is known. Has become.

[0003] The present applicant has also filed Japanese Patent Application No. 3-351716.
According to the document, a heating cooker that performs heating control by performing self-heating of one thermistor as a humidity sensor to perform humidity detection is further proposed. On the other hand, JP-A-4-254113
JP-A-4-254115, JP-A-4-27082
No. 2, JP-A-4-283321 discloses a heating cooker which recognizes the generation of water vapor by the so-called "fluctuation" of the exhaust temperature of a heating chamber and judges the heating state. Japanese Utility Model Laid-Open No. 4-120504 discloses a heating cooking apparatus having a control means for performing both boiling detection and normal temperature detection with one temperature sensor.

Further, Japanese Patent Application Laid-Open Nos. 63-145954 and 2-179559 have proposed a temperature sensor and a humidity sensor using a temperature-sensitive resistor aiming for high-speed response to temperature and humidity. In addition, the present applicant has proposed a detection circuit of the high-speed response type humidity sensor in Japanese Patent Application No. 4-120408. For example, FIGS. 16 (a) and (b)
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view and a cross-sectional view of a high-speed response moisture-sensitive element disclosed in JP-A-63-145954.

That is, as shown in FIGS. 16 (a) and 16 (b), after forming a bridge-shaped thin-film insulating layer 32 on a Si substrate 31, the substrate 31, which is Si, is anisotropically etched by crystal axis. A hollow structure is formed between the substrate 31 and the insulating layer bridge portion (hereinafter, referred to as a micro bridge) 33 by etching under the layer bridge portion to provide an element structure excellent in thermal insulation, that is, a low heat capacity. A sensitive film 34, which is a thin film sensor material, is formed. An electrode 35 for detecting electrical resistance is directly connected to the sensitive film 34 as shown in FIG.

The microbridge 33 of this device is manufactured by forming a thin film insulating layer 32, which becomes a microbridge 33 and serves as a mask at the time of etching, on a Si substrate by a thermal oxidation method, a vacuum deposition method, a sputtering method, or the like. CV
It can be formed by laminating by a method D or the like, and performing fine processing into a bridge shape by a photolithography technique and a chemical etching method or a dry etching method. The shape of the element is not limited to the microbridge, but may be a cantilever shape or a diaphragm shape.

On the other hand, when a large amount of water vapor or the like is discharged from the heating chamber, a large change (so-called fluctuation) occurs in the density of the water vapor or the like around the temperature sensor, and the AC component level of the electric signal from the temperature sensor becomes low. Japanese Patent Application Laid-Open No. 4-350421 discloses a means for controlling the magnetron to stop at a timing when the signal level of the AC component of the electric signal from the temperature sensor exceeds a predetermined level or after a lapse of a predetermined time from the timing. Is disclosed.

[0008]

However, all of the above-mentioned technologies have their advantages and disadvantages, and at present, they cannot always be said to be completely satisfactory. For example,
In the conventional control using a humidity sensor in the form of using two temperature-sensitive resistors, an absolute humidity amount that increases with the progress of heating is detected with respect to the absolute humidity amount at the start of cooking, and the increase is set in advance. The heating was controlled by the amount of time. However, in the conventional humidity sensor disclosed in Japanese Patent Application Laid-Open No. Sho 60-32288, since the heat capacity of the temperature-sensitive resistor is large, the response to a change in humidity is slow, and when the temperature reaches the set value, the sensor is already in an overheated state. Therefore, heating control in an optimal state was not always performed.

As a countermeasure against this, the present applicant has, as described above,
JP-A-63-145954, JP-A-2-1794
No. 59 and Japanese Patent Application No. 4-120408 propose a high-speed response type humidity sensor. However, in the conventional control based on the increase in the absolute humidity, the heating in the optimum state may not always be performed. Further, the humidity sensor is configured by self-heating two temperature-sensitive resistors, and it is necessary to match the temperature characteristics (resistance value, temperature coefficient, heat dissipation coefficient, etc.) of each temperature-sensitive resistor with high accuracy. Therefore, it is disadvantageous in terms of manufacturing cost / yield.

As a countermeasure against this, means for detecting the exhaust air temperature with a thermistor and controlling the heating by fluctuations of the exhaust temperature at the time of boiling is disclosed in Japanese Patent Laid-Open Nos. 4-254113 and 4-25.
No. 4115, JP-A-4-270822 and JP-A-4-2
No. 83321 proposes that all of these methods detect boiling and do not control heating in an optimum state. In order to further reduce the influence of the ambient temperature and detect boiling more accurately, the present applicant has a means by which the thermistor is self-heated to separately recognize the rise in ambient temperature and the generation of steam. 3-351 Ganping
No. 716, it is only possible to recognize the state immediately before boiling because of the large heat capacity of the thermistor used, and it is also difficult to control the optimum heating state.

On the other hand, the means disclosed in Japanese Utility Model Laid-Open No. 4-120504 is a technique for detecting boiling and temperature using one thermistor. This technique changes the control means depending on the difference in the heating mode. No signal is obtained during one heating mode. Further, Japanese Unexamined Patent Publication No.
The means disclosed in JP-A-350421 outputs an AC component of an electric signal from a temperature sensor due to fluctuation of water vapor as an AC signal, and turns on / off heating by a magnetron.
In this technology, a rapid response type temperature sensor is not used, but a technology that detects steam fluctuation as an AC component at an early stage before the DC component of the sensor output rises. Therefore, it cannot be said that the response to the humidity change is fast. Therefore, an object of the present invention is to obtain the optimum condition of the heating control which has conventionally been overheating, and to make it possible to detect the fluctuation component with one thermosensitive element in a self-heating state. An object of the present invention is to provide a humidity detecting device for a heating cooker having excellent functions such as detection of both temperatures.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is to provide a heating chamber for heating an object to be heated, a heating means, and a temperature-sensitive resistor. It is composed of one body and has a response to humidity change of 9
0% response is set to 10 seconds or less, a humidity sensor for detecting steam (humidity) generated with the progress of heating, and the humidity sensor is self-heated when humidity is detected, and is set to a non-self-heated state when ambient temperature is detected. The two states are alternately switched while the object to be heated is being heated, and a switching signal is provided to the state control unit, and two resistance values in the respective states of self-heating and non-self-heating are used. Obtain the resistance ratio of the state, obtain the change value of the absolute humidity by the change of the resistance ratio,
And a control unit for controlling heating based on the change value of the absolute humidity.

The state control section includes a load resistor connected between the humidity sensor and a constant current power supply. The control section controls the load resistance so as to be in the respective states when detecting humidity and when detecting temperature. The resistance value of the unit may be changed.

The state control unit includes a load resistor connected to the humidity sensor supplied with a current from a constant current power supply, and the control unit is in each of a state when detecting humidity and a state when detecting temperature. Thus, the resistance value of the load resistance section may be varied.

The humidity sensor preferably has a resistance stabilization time of 5 seconds or less at the start of energization and at the time of non-energization during self-heating.

The humidity sensor is a temperature-sensitive resistor having a negative characteristic, and the state control unit is a variable current power supply for supplying a current to the humidity sensor. At least one of them has a characteristic that gradually changes with time, the control unit, when the current value from the variable current power supply gradually changes with time,
The resistance value of each state may be calculated by detecting a current value when the voltage between both ends of the humidity sensor reaches a preset self-heating and non-self-heating voltage.

In this case, the predetermined voltage of one state to be measured first is equal to or larger than the predetermined voltage of the other state to be measured later, or the resistance value of each state is determined. Setting the current value to a predetermined range is effective.

[0018]

In the present invention, a high-speed response type humidity sensor is used. However, in the case of the high-speed response type, before the DC component of the humidity sensor output rises, that is, when the temperature of the object to be heated exceeds approximately 70 ° C. Since the fluctuation of steam can be detected as an AC component at an earlier stage, the heating control is performed by using the AC component. In addition, since the temperature-sensitive resistor can be set in a short time and alternately switched between self-heating and non-self-heating, it is possible to obtain resistance values as humidity information and temperature information with one temperature-sensitive resistor. In addition, it is possible to calculate the absolute humidity amount from the resistance ratio of these two states by arithmetic processing, thereby performing the heating control.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. First, the high-speed response type temperature sensitive resistor having a response to a humidity change of 90% or less for 10 seconds or less in the present invention refers to a known humidity sensor as shown in FIG. In the present invention, it is assumed that such a resistor is used. In the embodiment shown in FIG. 16, a thin-film type element is illustrated, but as described above, an equivalent product capable of high-speed response such that the response to a humidity change is 10 seconds or less at 90% response. If it is, it is applicable and is not limited to a thin film type element.

FIGS. 1 and 2 are a front view and a schematic explanatory sectional view of a microwave oven as an embodiment of a heating cooker to which the humidity detecting device of the present invention is applied. First, FIG.
As shown in the front view of FIG. 1, a door 2 for taking in and out an object to be heated (food) is attached to the front of the range body 1, and the door 2 is pressed by an open button 3 a provided on the operation panel 3. Can be opened with. A display unit 3b for displaying a heating time, a heating temperature and an output of a heating source is provided on the operation panel 3, and a plurality of heating buttons 3c and 3d for heating according to the type of food are provided. Is provided. When the user presses the heating buttons 3c and 3d, the range body 1 starts heating.

In FIG. 2, the microwave generated from the magnetron 5 passes through the waveguide 6 and is absorbed by the object to be heated (food) 4 placed on the saucer 8 in the heating chamber 7 and the object to be heated ( Heating the food 4 is similar to the function of a normal microwave oven. In the heating chamber 7 of the microwave oven 1, an exhaust port 9 for discharging steam from the heated object (food) 4 or exhaust air containing heat of the steam is formed. The temperature sensing element 10 is disposed in the passage. Reference numeral 3 denotes a cooling fan for cooling the magnetron 5.

Next, an embodiment of the control circuit of the humidity detecting device according to the present invention will be described with reference to the circuit diagram of FIG. In FIG. 3, Rs is a temperature-sensitive resistor that is exposed to an atmosphere containing moisture and detects a change in humidity, and Rr is a temperature-sensitive resistor that is sealed with respect to the atmosphere to detect a temperature change in the atmosphere. . Further, A ₁ and A ₂ is an operational amplifier, forms a circuit that produces an output Vout1 comprises a resistivity R ₁ to R _5, specific to the output terminal of the further operational amplifier A ₂ in the circuit of FIG. 3 An integrating circuit (within a dotted line) composed of a resistor R ₆ , a capacitor C ₁ , and a comparator A ₃ is connected to generate an output Vout 2, and these outputs Vout 2 and Vout 1 are control units of the cooking device. 20 and control of cooking is performed.

Next, control means by the circuit of FIG. 3 will be described with reference to the drawings. Voltage Vc ₁ resistance output Vout1 R _6, at a voltage which is integrated by a time constant set by the capacitor C _1, the time constant is set longer than the frequency of the AC component of the output Vout1. This Vout1 and Vc ₁
Output compare two voltages by the comparator A ₃ Vout2 becomes a voltage indicating only the AC component of the output Vout1 of. Control unit 20
In, cooking is controlled by the number of pulses of the AC component or the amplitude width. In this case, the heating control is not limited to the control using only the output Vout2, and the conventional control may be performed using the output Vout1 depending on the food. For reference, showing the circuit output when the object to be heated serving heated food (heating milk) by Vout1, Vc _1, Vout2 in Fig. 3, the aging characteristics of the curve of FIG. As another method, an AC component may be obtained from the waveform by arithmetic processing of the control unit 20 using only the output Vout1, and cooking may be controlled by the number of pulses or the amplitude width of the AC component.

Next, another embodiment of the control circuit of the humidity detecting apparatus according to the present invention will be described with reference to the circuit diagram of FIG. The circuit example in FIG. 5 is an example in which only one temperature-sensitive resistor is provided, and the humidity sensor is configured only with the temperature-sensitive resistor Rs exposed to the atmosphere. The temperature sensitive resistor is a platinum resistor having a positive temperature coefficient. In the circuit of FIG.
VS is an output at the time of heating the object to be heated.
The resistor R _8, is connected to the inverting input terminal of the operational amplifier A ₄ via the capacitor C _2, the non-inverting input terminal is grounded via a resistor R _10. The output terminal and the inverting input terminal of the operational amplifier A ₄ is connected via a resistor R _9. This circuit is a general-purpose differentiating circuit. Therefore, the effect is that the output Vout3 is obtained by converting the AC component of VS into a pulse component, and the AC component of the sensor output is determined by the pulse number, peak value, frequency, and the like of this pulse. Can be recognized. For reference, FIG. 6 shows a curve of the change over time of the output VS and Vout3 during heating of food (heating of milk) by this circuit.

Next, still another embodiment of the control circuit of the humidity detecting apparatus according to the present invention will be described with reference to a control block diagram of FIG. FIG. 7 includes a state control unit 21 that switches the state of the humidity sensor between a self-heating state and a non-self-heating state according to a signal from the control unit 20. The state control unit 21 causes the humidity sensor to perform self-heating and non-self-heating. The two states are switched. The voltage between both ends of the humidity sensor is input to a differentiating circuit unit 22 and a resistance value calculating circuit 23. During self-heating, fluctuation humidity is detected by an output of the differentiating circuit 22,
At the time of non-self-heating, it functions as ambient temperature detection via the resistance calculation circuit unit 23. In addition, the two states are alternately switched during heating, and in either the self-heating state or the non-self-heating state, the resistance value in each state is calculated via the resistance calculation circuit section 23, and the resistance ratio is obtained by the control section 20. The change value of the absolute humidity can also be obtained by the fluctuation of. Since the absolute humidity information in the heating cooker needs information with a resolution of at least 10 seconds or less, the resistance stabilization time at the start of energization needs to be 5 seconds or less.

Next, in the embodiment shown in the control block diagram of FIG. 7, as a more specific circuit, a case where the temperature-sensitive resistor Rs is a platinum resistor is shown in FIG. Platinum resistor Rs is connected to a constant voltage source E0 via the resistor R _11, the load resistor R ₁₁ is connected in parallel with the resistor R ₁₂ which is variably connected state by signals S ₁ from the control unit 20 I have. Where R
It has become the setting of _11> R _12. R _{12 in the} non-self heating state
Is not connected, and therefore, the current flowing through Rs is small and is in a non-self-heating state. On the other hand, in the self-heating state, R
₁₂ is a current value flowing through the combined resistance value is reduced Rs of R _11, R ₁₂ are connected in parallel to R ₁₁ becomes becomes self-heating state greatly. The control unit 20 includes a voltage Vout4 across the sensor.
Is input, and the resistance value in each state is calculated from the known resistance values R ₁₁ and R ₁₂ , the resistance ratio is obtained from each resistance value, and the change in the absolute humidity is obtained from the change in the resistance ratio. .

Next, still another embodiment of the control circuit of the humidity detecting device according to the present invention will be described with reference to the circuit diagram of FIG. The circuit in FIG. 9 is a circuit for driving the humidity sensor Rs with a constant current. Humidity sensor is connected between the output terminal of the operational amplifier A ₅ and the inverting input terminal. Inverting input terminal is grounded further resistor R _13. Resistor R ₁₃ is connected in parallel with the resistor R ₁₄ which varies the connection state by a signal S ₂ from the control unit. Here, R ₁₃ > R ₁₄ is set. Reference voltage E0 to the non-inverting input terminal of the operational amplifier A ₅
Is entered. R ₁₄ is not connected to a non-self-heating state, therefore the current flowing through the Rs is in a state of small non-self heating. Whereas a self-heating state R ₁₄ is connected in parallel to R _13, the combined resistance value of R _13, R ₁₄ becomes smaller, the current value flowing to Rs will be self-heated state greatly. Current value I E0 / R ₁₃ flowing through Rs, or E
The value is determined by 0 / (R ₁₃ // R ₁₄ ). Output Vou
t5 is a value of (E0 + I × Rs). Since E0 and I are known, the sensor resistance value Rs is calculated and calculated, and the resistance ratio is obtained from each resistance value. Desired.

On the other hand, when the temperature-sensitive resistor is an element having a negative temperature characteristic, for example, a thermistor, the control is performed as follows. First, the current-voltage characteristics of the thermistor are shown in FIG.
0 is shown. In this case, unlike the temperature-sensitive characteristic having a positive temperature characteristic, the current-voltage characteristic has a mountain-shaped characteristic. That is, in the range of the zone (I) where the current is small, the voltage across the thermistor gradually increases as the current increases. However, as the current increases and the thermistor starts self-heating, the temperature of the thermistor increases and the resistance value decreases. Therefore, when the current is further increased (Zone II), the decrease in the resistance value due to the increase in the current is promoted, and as a result, the voltage is reduced. Therefore, the non-self-heating state is used in zone I, and the self-heating state is used in zone II. Here, the temperature T
0, T1 (T0 <T1) Absolute humidity AH0, AH1 (AH
If 0 <AH1), the current-voltage characteristics of the thermistor are as shown in FIG.

Then, as shown by the curve in FIG. 12, the voltage VS across the sensor when the current is gradually changed becomes a predetermined voltage VSN (non-self-heating) or VSH (self-heating). By detecting the current values IN and IH at that time, the resistance value in each state can be calculated and calculated. FIG. 13 shows a control block diagram of an example of a circuit for performing such control. The voltage Vout6 between both ends of the sensor is compared with VSH and VSN predetermined by the control unit 20.
Since the variable power supply current of the current source 24 is gradually changed to the sensor by a signal S ₃ from the control unit 20, V
out6 is VSH, the current value by the level of S ₃ when the match the VSN is recognized, therefore the sensor resistance Rs is sought resistance ratio than the resistance value of each calculated calculated, a change in absolute humidity than the change of the resistance ratio The quantity is required.

Next, a case where the current is changed from small to large based on the curve of FIG. 14 will be considered. In this case, the current measured first is a current value when VS and VSN in the non-self-heating state match (IN). Then, it is compared with the VSH in the self-heating state. Here, the setting of VSH is VS
If H (= VSH ₀ )> VSN, the current has two points when the current increases, that is, IH ₀₁ and IH _02, and the true self-heating state IH ₀₂ is not read.
Therefore, if VSH (= VHS ₁ ) <VSN, there is only _one voltage IH _{1 as} the current increases, so that the current in the self-heating state can be correctly detected. The same is true when the current is changed from large to small. If the set voltage in the first measurement state is larger than the set voltage in the next measurement state, no erroneous recognition occurs. Further, as shown in FIG. 10, since the energizing current value is naturally different in the non-self-heating state and the self-heating state, the current value range in the non-self-heating state (Zone I) and the self-heating state (Zone II) is determined in advance. Is set, the set voltage (VSN,
VSH) can be set arbitrarily.

Next, an example of a control circuit for gradually changing the current is shown in the circuit diagram of FIG. That is, the control unit 20
The signal S ₄ from the resistor _{R 16, R 17, R 18} , capacitors C _3, is input to the integration circuit constituted by an operational amplifier A _6. The output E0 of the integrating circuit is a reference power supply E of a constant current circuit composed of an operational amplifier A ₇ , a resistor R ₁₅ , and a humidity sensor Rs connected between the output terminal and the inverting input terminal of A _7.
Input as 0 (t). Signal S ₄ from control unit 20
Generates a pulse whose duty is controlled. The output of the integrating circuit E (t), and outputs a triangular waveform corresponding to the duty time of S _4. Since the circuit constant of the integration circuit is known, the value of E (t) according to the on-time (t) is known in advance. The current I flowing through the constant current circuit Rs is determined depending on a I = E0 (t) / R 15 in relation to the known R _15, I
Is a function I (t) of the signal S ₄ on-time (t). Vo
Since ut7 is determined by (E0 (t) + Rs × I (t)), the sensor resistance value Rs is calculated and calculated, the resistance ratio is obtained from each resistance value, and the change in the absolute humidity is obtained from the change in the resistance ratio. Is required. In order to increase the accuracy, E0 (t)
May be directly recognized by the control unit 20 to perform the arithmetic processing.

[0032]

As is clear from the above embodiments, the self-heating and non-self-heating states are alternately switched while the object to be heated is being heated, and the resistance value of the temperature-sensitive resistor in the humidity detection is changed. And the resistance value of the temperature-sensitive resistor in the detection of the ambient temperature, the resistance ratio of the two states is obtained one after another, and the change value of the absolute humidity can be obtained from the fluctuation of the resistance ratio.
The change of the absolute humidity can be known with one temperature sensitive resistor.
Further, according to the present invention, the responsiveness to humidity change is 90%.
By using a high-speed response type thermosensitive resistor with a% response of 10 seconds or less, first, it is possible to detect a fluctuating component of steam generated at a low temperature of food, so that this fluctuating component is detected as an AC component. However, by performing heating control with this component, it becomes possible to perform optimal heating control of food heating control which has conventionally been overheated. In addition, since the fluctuation component can be detected by one thermosensitive element in a self-heating state, absolute humidity detection by two conventional thermosensitive elements becomes unnecessary, and the cost of the humidity sensor can be greatly reduced. Further, humidity detection and temperature detection can be performed by one element.

Since the high-speed response type humidity sensor has a low heat capacity and has a very short stabilization time, it is possible to switch between self-heating and non-self-heating for one element in a short time. Humidity can be detected, and the cost of the humidity sensor can be significantly reduced. Further, there is an effect that the self-heating state and the non-self-heating state in the case of a temperature-sensitive resistor having a negative temperature characteristic can be measured without erroneous confirmation. As described above, the present invention exerts many excellent effects, and is extremely useful in practical use.

[Brief description of the drawings]

FIG. 1 is a front view of a microwave oven which is an embodiment of a heating cooker to which a humidity detecting device of the present invention is applied.

2 is a schematic explanatory sectional view of the microwave oven of FIG. 1;

FIG. 3 is a circuit diagram showing one embodiment of a control circuit of the humidity detecting device according to the present invention.

FIG. 4 is a curve showing output characteristics over time when food is heated by the circuit of FIG. 3;

FIG. 5 is a circuit diagram showing another embodiment of the control circuit of the humidity detecting device according to the present invention.

FIG. 6 is a curve showing a temporal characteristic of an output when food is heated by the circuit of FIG. 5;

FIG. 7 is a control block diagram showing still another embodiment of the control circuit of the humidity detecting device according to the present invention.

8 is a circuit diagram showing a specific circuit example of the control block diagram of FIG. 7;

FIG. 9 is a circuit diagram showing still another embodiment of the control circuit of the humidity detecting device according to the present invention.

FIG. 10 is a curve showing current-voltage characteristics of a thermistor.

FIG. 11 is a curve showing current-voltage characteristics of a thermistor.

FIG. 12 is a curve showing current-voltage characteristics of a thermistor.

13 is a control block diagram of an embodiment of the present invention for performing the control of FIG.

FIG. 14 is a curve showing current-voltage characteristics of a thermistor.

FIG. 15 is a circuit diagram showing still another embodiment of the control circuit of the humidity detecting device according to the present invention.

FIG. 16 shows a configuration of a known high-speed response moisture-sensitive element (a).
It is a perspective view and (b) sectional drawing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Microwave oven main body 2 Door 3 Operation panel 3a Release button 3b Display part 3c, 3d Heating button 4 Heated object 5 Magnetron 6 Waveguide 7 Heating chamber 8 Receiving tray 9 Exhaust port 10 Temperature sensing element 20 Control part 21 State control part 22 differentiating circuit 23 resistance value calculating circuit 24 a variable current source 31 substrate 32 thin film insulating layer 33 microbridge 34 sensitive film 35 electrodes _{A 1, A 2, A 4} , A 5, A 6, A 7 operational amplifier A ₃ comparator Rr temperature sensing resistor Rs thermal sensitive resistor (humidity sensor) R ₁ to R ₁₈ resistivity C _1, C _2, C ₃ capacitor

Claims (7)

(57) [Claims] 1. A heating chamber for heating an object to be heated, a heating means, and one temperature-sensitive resistor. The response to a humidity change is set to 10 seconds or less at a 90% response, and steam generated as heating proceeds. A humidity sensor that detects (humidity); and the humidity sensor self-heats to 100 ° C. or more when humidity is detected, and is set to a non-self-heating state when the ambient temperature is detected. In addition, a state control unit that switches alternately, while providing a switching signal to the state control unit, the resistance ratio of the two states is obtained from the resistance value in each state of self-heating and non-self-heating, A control unit that obtains a change value of the absolute humidity by the fluctuation and controls heating based on the change value of the absolute humidity. 2. The state control section includes a load resistor connected between the humidity sensor and a constant current power supply, and the control section controls the state so as to be in each of a state at the time of humidity detection and a state at the time of temperature detection. 2. The humidity detecting device for a cooking device according to claim 1, wherein the resistance value of the load resistance section is variable. 3. The state control unit includes a load resistor connected to the humidity sensor supplied with a current from a constant current power supply, and the control unit enters a state when detecting humidity and a state when detecting temperature. The humidity detecting device for a heating cooker according to claim 1, wherein the resistance value of the load resistance section is varied. 4. The humidity detecting device according to claim 1, wherein the humidity sensor has a resistance stabilization time of 5 seconds or less at the start of energization and at the time of non-energization during self-heating. 5. The humidity sensor is a temperature-sensitive resistor having a negative characteristic, and the state control unit is a variable current power supply that supplies a current to the humidity sensor. The control unit has a characteristic that gradually changes with time in at least one of the cases, and the control unit is configured such that when the current value from the variable current power supply gradually changes with time, the voltage across the humidity sensor is set in advance. The humidity detecting device for a cooking device according to claim 1, wherein the resistance value of each state is calculated by detecting a current value when the voltage reaches the self-heating and non-self-heating voltages. 6. The cooking method according to claim 5, wherein the preset voltage of one state measured first is equal to or greater than the predetermined voltage of the other state measured later. Vessel humidity detector. 7. The humidity detecting device for a cooking device according to claim 5, wherein a current value for obtaining a resistance value in each state is set in a predetermined range.