JPH04270823A - Heating and cooking device - Google Patents

Abstract

PURPOSE:To perform a proper heating of a food in a device for performing an automatic cooking in response to an operation of a gas sensor irrespective of a temperature and a humidity around a main body of the cooking device. CONSTITUTION:A heating and cooking device is provided with the first temperature sensor 11 for sensing a temperature around a main body of it when the cooking is started and with the second temperature sensor 14 for sensing a temperature around a gas sensor which is varied as the cooking is proceeded. It is further provided with a correcting means for correcting a gas sensing signal from a gas sensor 13 on the basis of temperature sensing signals from the first and second temperature sensors 11 and 14 and an amount of saturated water vapor corresponding to these detected temperatures.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooking device equipped with a gas sensor for detecting gas such as water vapor generated from food, and configured to control heating based on a gas detection signal output from the gas sensor.

0003

[Background Art] When automatic cooking is performed in a microwave oven, which is a heating cooker of this type, as shown in FIG. When the temperature decreases from V0 by a predetermined value Vc, a predetermined additional heat stroke is started, and the cooking ends after that stroke.

0004

[Problem to be Solved by the Invention] By the way, if the temperature and humidity of the place where the microwave oven is installed changes, the rate of change in the resistance of the gas sensor changes, so when cooking the same amount of the same type of food, However, the cooking end point may vary, that is, the cooking time may vary. To explain with reference to FIG. 4, the solid line A shows the change in the gas detection signal from the gas sensor when the room temperature is T1 (°C) and the relative humidity is H1 (%), and when the room temperature is T2 (°C) and the relative humidity is A solid line B shows the change in the gas detection signal from the gas sensor when H2 (%). However, T1<T2, H
1<H2. In addition, in FIG. 4, V1 and V2 are
The initial values output from the gas sensor in each of the above cases are shown.

[0005] In this case, the cooking is controlled to end when the peak value V0 drops by a predetermined value Vc, but appropriate heating is performed when the room temperature is T1 and the relative humidity is H1. When the predetermined value Vc is set, the heating time may become too long when the room temperature is T2 and the relative humidity is H2. That is, in an actual microwave oven, the predetermined value Vc is set so that appropriate heating is performed when the temperature and humidity are normal.
When the temperature and humidity are low in winter, the cooking time becomes short, whereas when the temperature and humidity are high in the summer, the cooking time becomes long. In the worst case scenario, the cooked food could not be eaten.

A specific example is shown in FIG. FIG. 5 is a graph showing the rate of change in resistance of the gas sensor. In FIG. 5, curve C1 is the case when one cup of miso soup is cooked at an initial temperature of 5°C and an initial relative humidity of 40%, and curve C2 is the case when one cup of miso soup is cooked at an initial temperature of 35°C and an initial relative humidity of 70%. This is the case. Curve D1 is the case when 4 cups of miso soup are cooked at an initial temperature of 5°C and initial relative humidity of 40%, and curve D2 is when 4 cups of miso soup is cooked at an initial temperature of 35°C and an initial relative humidity of 70%. be. In this case, it can be seen that the rate of change in the resistance of the gas sensor differs greatly depending on the state before the start of cooking, whether it is for one cup of miso soup or for four cups.

In particular, since the curve C2 and the curve D1 almost overlap, the cooking time for one cup of miso soup may be almost the same as the cooking time for four cups, depending on the state before cooking starts. I understand that.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cooking device that performs automatic cooking based on a gas sensor and can appropriately heat food regardless of the temperature and humidity around the cooking device itself. be.

[Configuration of the invention]

0010

[Means for solving the problems] The heating cooker of the present invention includes:
In a cooking device that is equipped with a gas sensor that detects gas such as water vapor generated from food and that controls heating based on a gas detection signal from the gas sensor, a first temperature that detects the temperature around the cooking device main body at the time of starting cooking. a second temperature sensor that detects the temperature around the gas sensor that changes as cooking progresses; and a temperature detection signal from the first and second temperature sensors and the detected temperature. The present invention is characterized in that it includes a correction means for correcting the gas detection signal from the gas sensor based on the saturated water vapor amount corresponding to the temperature.

[0011]

[Operation] According to the above means, the temperature around the cooker main body at the start of cooking and the temperature around the gas sensor that changes as cooking progresses are detected, and the detected temperature and these detected temperatures are handled accordingly. The gas detection signal from the gas sensor is corrected based on the saturated water vapor amount. As a result, if the cooking is controlled to end when the corrected output level of the gas detection signal drops by a predetermined value from the peak value, the cooking time to heat the food can be controlled regardless of the temperature and humidity around the cooker itself. is approximately constant and appropriate depending on the type and amount of food, and the food can be heated appropriately.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a microwave oven will be described below with reference to FIGS. 1 to 3. First, in FIG. 1 showing the general configuration as well as the electrical configuration, a rotary plate 3 on which food 2 is placed is disposed at the inner bottom of a cooking chamber 1 of a microwave oven. This rotating plate 3 is
It is designed to be rotationally driven by a motor (not shown). Further, the magnetron 4 disposed outside the cooking chamber 1 is configured to heat the food 2 by oscillating microwaves and supplying them into the cooking chamber 1 .

The magnetron 4 is driven by a high voltage transformer 5 and a voltage doubler rectifier circuit (not shown). A DC relay 7 is provided between the high voltage transformer 5 and the commercial AC power supply 6, and the relay 7 controls the high voltage transformer 5.
is de-energized. The DC relay 7 is controlled on and off by a control circuit 8. That is, the magnetron 4 is driven and controlled by the control circuit 8.

The control circuit 8 includes a microcomputer, and in addition to the function of controlling the heating operation in general, it also has the function of a correction means. The control circuit 8 is configured to receive switch signals output from an input circuit 9 including various operation switches, and to drive and control a display 10 that displays the progress of cooking, time, etc.

The main body of the cooking appliance (not shown) is provided with a room temperature sensor 11, which is a first temperature sensor and is made of a thermistor or the like. This room temperature sensor 11 is configured to detect the room temperature, which is the temperature around the cooking device main body at the start of cooking, and provide the control circuit 8 with a temperature detection signal. Further, an exhaust duct 12 is provided at the upper left end of the heating cooking chamber 1 for discharging the air inside the heating cooking chamber 1 to the outside, and a gas sensor 13 is disposed within the exhaust duct 12. This gas sensor 13 detects gas such as water vapor generated from the food 2 and provides a gas detection signal to the control circuit 8. It is located near the gas sensor 13 in the upper left end of the heating cooking chamber 1,
A temperature sensor 14, which is a second temperature sensor and is made of a thermistor or the like, is provided. This temperature sensor 14 is designed to detect the temperature around the gas sensor 13, which changes as cooking progresses.

Next, the operation of the above structure will be explained with reference to FIGS. 2 and 3. First, regarding the correction contents of the correction means for correcting the gas detection signal output from the gas sensor 13,
Let's be specific. The gas sensor 13 has the following (1) and (
2) It is known to have the temperature characteristics and relative humidity characteristics shown in the formula (Toshiba Review 1984, VOL. 3).
9, NO. 8).

α=log(RT1/RT0)/(T1-T0)
(1) β
=log(RH1/RH0)/(H1-H0)
(2) Here, α,
β is a constant specific to the gas sensor, α represents the temperature coefficient of the in-air resistance value, and β represents the relative humidity coefficient of the in-air resistance value.

Furthermore, T1 and T0 are the temperature, H1 and H0 are the relative humidity, RT1 is the resistance value when the temperature is T1, RT0 is the resistance value when the temperature is T0, and RH1 is the resistance when the relative humidity is H1. The value RH2 is the resistance value when the relative humidity is H1.

From the above equations (1) and (2), the resistance value R of the gas sensor 13 when it is installed in an environment where the temperature is T1 (°C) and the relative humidity is H1 (%) is , R=R0*EXP{α*(T1-T0)+β*(H
1-H0)} (3). Here, R0
is the gas sensor 13 when the gas sensor 13 is installed in an environment where the temperature is T0 (°C) and the relative humidity is H0 (%).
is the resistance value of

Furthermore, during cooking in the microwave oven, the temperature and relative humidity around the gas sensor 13 change as the cooking progresses and become a function of the elapsed time t. Therefore, the resistance value of the gas sensor 13 during cooking also becomes a function of the elapsed time t, and is expressed as follows from equation (3).

R(t)=R0*EXP{α*(T1(t)−T0
)
+β*(H1(t)-H0)}
(4) Here, R0 is the initial resistance at the start of cooking (Ω
) T0 is the initial temperature at the start of cooking (℃) H0 is the initial relative humidity at the start of cooking (%) T1 (t) is the temperature increase function from the start of cooking H1 (t) is the change function of relative humidity from the start of cooking It is. In addition, T1(t)-T0 is
This is the range of increase in temperature, hereinafter expressed as ΔT. Also, H1(t
)-H0 is the increase in relative humidity, and when expressed in terms of the amount of water vapor, it becomes as shown in the following equation.

H1(t)-H0=P1(t)/PS1(t)+P
0/PS1(t)

-P0/PS0 (5) Here, P
1(t) is the amount of water vapor generated due to the temperature of the food PS1(t) is the amount of saturated water vapor corresponding to the temperature around the gas sensor which increases as cooking progresses P0 is the amount of water vapor P corresponding to the initial relative humidity at the start of cooking
S0 is the saturated steam amount corresponding to the initial temperature at the start of cooking. That is, the first term in equation (5) is the relative humidity that increases due to water vapor generated from the food as cooking progresses. The second term in equation (5) is a term in which the initial relative humidity at the start of cooking decreases as the cooking progresses (due to temperature rise). The third term in equation (5) represents the initial relative humidity at the start of cooking.

Now, equation (4) can be transformed as follows.

R(t)=R0*EXP[α*ΔT+β*{P1(
t)/PS1(t)
+P0/PS1(t)-P0/PS0}]
(6) Furthermore, if this equation is separated into a term related to the initial temperature and relative humidity at the start of cooking and a term other than that, R(t)=R0*EXP[α*ΔT+β*{P
0/PS1(t) -P0/P
S0}+β*{P1(t)/PS1(t)}] (7
) Here, during the period when water vapor is not generated from the food, there is almost no change in the resistance of the gas sensor 13 (as is clear from the experimental results), so P1(t)=0. That is, β*
{P1(t)/PS1(t)}=0.

Therefore, α*ΔT+β*{P0/PS1(
t)-P0/PS0}=0.

[0026] This is due to the influence of temperature rise (α*ΔT)
and the effect of the decrease in initial relative humidity due to temperature rise (β＊{
This means that P0/PS1(t)-P0/PS0}) cancel each other out.

Therefore, equation (7) becomes as follows.

R(t)=R0*EXP[β*{P1(t)/PS
1(t)}] (8) Now, the relational expression of the resistance of the gas sensor 13 when cooking is started from a different initial state is expressed as follows from equation (8).

First, the initial temperature is T1 and the initial relative humidity is H.
1. When you start cooking when the initial resistance is R1,
R1(t)=R1*EXP[β*{P1(t)/PS
1(t)}] (9) Also, when cooking is started with the initial temperature being T2, the initial relative humidity being H2, and the initial resistance being R2, R2(t)=R2*EXP[β*{P
2(t)/PS2(t)}] (10).

By correcting equations (9) and (10), automatic cooking based on the gas sensor 13 can be made with less variation. In this case, the initial resistance R1
and correction of the initial resistance R2 and the resistance change coefficient of the gas sensor 13 (EXP[β*{P2(t)/PS2(t)}]
(as shown in ).

By the way, the water vapor generated from the food being heated will rapidly evaporate when the water vapor pressure around the food is lower than the saturated water pressure, so P1(t)=P
2(t) holds true.

Therefore, if the initial resistance correction coefficient is K1, R1=K1*R2 Therefore, K1=R1/R2

(11) becomes.

Further, if the correction coefficient of the resistance change coefficient of the gas sensor 13 is K2, then P1(t)/PS1(t)=K2*{P2(t)/
PS2(t)} Therefore, K2=PS2(t)/PS
1(t)
(12).

By appropriately selecting K1 and K2 described above, automatic cooking based on the gas sensor 13 can be performed with less variation. Here, regarding equation (11),
This is replaced by the conventional selection of the optimal load resistance at the start of cooking.

On the other hand, the correction of equation (12) is executed as shown below. Here, the resistance of the standard gas sensor is assumed to be R1(t). When the user places food in the cooking chamber 1, selects automatic cooking based on the gas sensor 13, and presses the start key to start cooking, the control circuit 8 executes the following processing steps. Ru.

In step 1, the room temperature T0 at the start of cooking and the resistance R0 of the gas sensor 13 are detected. Subsequently, in step 2, the difference between the room temperature T0 and the reference temperature T1 is calculated as ΔT=T0−
Find T1. Then, in step 3, the temperature T2(t) around the gas sensor 13 and the resistance R2(t) of the gas sensor 13 during cooking are detected. Next, in step 4, a change in resistance ΔR of the gas sensor 13 is calculated. In this case, it is calculated using the following formula.

ΔR02=R0-R2(t) Thereafter, in step 5, the correction coefficient K2 is calculated using the following equation.

K2={saturated water vapor amount of (T2(t)+ΔT)}

÷{saturated water vapor amount at T2(t)} Then, in step 6, the amount of change ΔR in the resistance of the gas sensor 13 after correction is calculated. In this case, it is calculated using the following formula.

ΔR=K2*ΔR02 Next, in step 7, it is determined whether the calculated ΔR has reached the preset value, and if ΔR has reached the set value, the next cooking operation For example, proceed to heating stop (
Step 8).

FIG. 3 shows an example of correction performed by performing the above-described processing. FIG. 3 is a graph showing the rate of change in resistance of the gas sensor 13. In FIG. In FIG. 3, curve E1 is the case when one cup of miso soup is cooked at an initial temperature of 5°C and an initial relative humidity of 40%, and curve E2 is the case when one cup of miso soup is cooked at an initial temperature of 35°C and an initial relative humidity of 70%. This is the case. Curve F1 is the case when 4 cups of miso soup are cooked at an initial temperature of 5°C and an initial relative humidity of 40%, and curve F2 is
This is a case where four cups of miso soup are cooked at an initial temperature of 35° C. and an initial relative humidity of 70%. Note that Table 1 below shows specific values of the correction coefficients in the case of the above example.

[0041]

[Table 1]

As is clear from the example shown in FIG. 3, the rate of change in the resistance of the gas sensor 13 is almost the same whether there is one cup of miso soup or four cups, regardless of the state before the start of cooking. It can be seen that it changes to In particular, when compared with the conventional example shown in FIG. 5, it can be seen that the effect is remarkable. Therefore, when automatically cooking based on the gas sensor 13, that is, when controlling the cooking to end when the output level of the gas detection signal from the gas sensor decreases by a predetermined value from the peak value, a microwave oven is not installed. Even if the temperature and humidity of the place where the food is cooked change, variations in the cooking end point, that is, variations in the cooking time, can be prevented as much as possible. In other words, according to this embodiment, food can be appropriately heated regardless of the temperature and humidity around the cooking device main body.

In the above embodiment, the present invention is applied to a microwave oven, but the present invention is not limited to this, and may be applied to, for example, an electric oven provided with an electric heater in the cooking chamber.

[0044]

Effects of the Invention As is clear from the above description, the present invention provides a first method for detecting the temperature around the cooking device main body at the start of cooking.
It is equipped with a second temperature sensor that detects the temperature around the gas sensor that changes as cooking progresses, and the temperature detection signals from the first and second temperature sensors and these detected temperature sensors are provided. Since the configuration is equipped with a correction means that corrects the gas detection signal from the gas sensor based on the amount of saturated water vapor corresponding to the temperature, it is possible to automatically cook based on the gas sensor regardless of the temperature and humidity around the cooker itself. It has the excellent effect of being able to properly heat food.

[Brief explanation of the drawing]

[Fig. 1] Block diagram showing one embodiment of the present invention

[Figure 2] Graph showing the relationship between temperature and saturated water vapor pressure

[Figure 3] Graph showing the rate of change in gas sensor resistance

[Figure 4] Graph showing changes in the gas detection signal output from a gas sensor with a conventional configuration

[Figure 5] Graph showing the rate of change in resistance of the gas sensor

[Explanation of symbols]

1 is a heating cooking chamber, 2 is a food product, and 8 is a control circuit (correction means)
, 11 is a room temperature sensor (first temperature sensor), 13 is a gas sensor, and 14 is a temperature sensor (second temperature sensor).

Claims (1)

[Claims] Claim 1: In a heating cooker that is equipped with a gas sensor that detects gas such as water vapor generated from food and that controls heating based on a gas detection signal from the gas sensor, the temperature around the main body of the cooker at the start of cooking is detected. a first temperature sensor that detects the temperature around the gas sensor that changes as cooking progresses; a temperature detection signal from the first and second temperature sensors; A heating cooker comprising: a correction means for correcting a gas detection signal from the gas sensor based on a saturated water vapor amount corresponding to a temperature.