JPH0157255B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cooking device, and more particularly to a cooking device that automatically cooks food using a plurality of sensors.

Configuration of conventional example and its problems In a conventional microwave oven with an automatic cooking function, for example, a humidity sensor was used as a means for detecting the heating state of food. This humidity sensor consisted of a humidity-sensitive resistor whose resistance value changed in response to changes in the amount of water vapor generated as the food was heated.

Generally, many of these humidity sensors have a characteristic that electrical resistance changes due to attachment and detachment of water vapor particles on the sensor surface, and therefore, if the sensor surface becomes contaminated, the sensitivity of the sensor decreases. Particularly in cooking appliances such as microwave ovens, it is difficult to avoid components such as oil and soybean oil from evaporating and adhering to the sensor, so it is necessary to remove these contaminants. Incineration is an effective method for removing pollutants. Therefore, when using a humidity sensor as a heating state detection means in a heating cooker, it is necessary to perform this incineration cleaning. FIG. 4 shows a perspective view of the humidity sensor. An incineration cleaning heater 13 is installed around the humidity-sensitive resistance element 5 as a sensor.
is arranged. To clean a humidity sensor by incineration, it is necessary to raise the temperature to several hundred degrees (approximately 450 degrees Celsius) or higher. The atmosphere of the sensor element at this time has a relative humidity of 0%. Therefore, it is impossible to accurately detect humidity immediately after incineration cleaning, that is, until the humidity sensitive resistive element 5 returns to room temperature.
Moreover, it is most effective to perform this incineration cleaning at the beginning of cooking. This is to remove contaminants that have adhered to the food before the start of cooking, so that it is in the least contaminated state at the time of detection.

However, there are drawbacks as shown below.
That is, by performing incineration cleaning at the start of cooking, the temperature of the humidity sensor increases, making it impossible to detect water vapor generated from the food. In other words, accurate humidity detection cannot be performed until the temperature of the humidity sensor returns to room temperature. It takes approximately one minute for this incineration cleaning and for the humidity sensor to return to room temperature. Therefore, in the case of small foods that are heated to almost a predetermined temperature within one minute, the generation of water vapor cannot be detected. In other words, it is not possible to cook small foods. Furthermore, in order to enable detection of this small food, it is necessary to stop the heating means for heating the food from the time cooking starts until the humidity sensor returns to room temperature.

As described above, the humidity sensor cannot detect the doneness of small foods (those that are heated within about 1 minute and generate steam). Alternatively, in order to detect even small foods, it is necessary to stop heating until the humidity sensor returns to room temperature after incineration and cleaning, which increases the cooking time accordingly.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
To provide a heating cooker capable of detecting the completion of food even if the food is small, without stopping heating from the start of cooking.

Structure of the Invention In order to achieve the above object, the cooking device of the present invention includes a sensor that detects gas or water vapor generated as food is heated, and a thermistor or infrared sensor that directly or indirectly detects the temperature of the food. When the humidity sensor that detects gas or water vapor cannot be detected during incineration cleaning, even small foods can be heated from the start of cooking by detecting the heating state of the food with a thermistor or infrared sensor. This has the effect of allowing heating and cooking without stopping the output.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of the main body of the cooking device according to the present invention. 1 is a display section that displays heating output, heating time, heating style, etc., and 2 is a setting section provided with keys for selecting and inputting heating output, heating style, cooking menu, etc. 3 is a timer setting section for inputting the heating time. 4 is a door that can be opened and closed to take food in and out of the heating chamber. 24 is a start key for inputting the start of cooking. Therefore, after opening the door 4 and putting food into the heating chamber, and closing the door 4, the setting section 2 sets the cooking menu and heating output, and the timer setting section 3 sets the heating time, etc., and then the start key 24 is pressed. This is how cooking begins. These heating cookers generally allow setting of two cooking modes: a manual setting cooking mode and an automatic cooking mode.
In the manual setting cooking mode, as described above, the heating output and heating style are inputted using the setting section 2, the heating time is set using the timer setting section 3, and then cooking is started using the start key 24. Then, cooking is performed for the heating time set based on the input heating output and heating style. On the other hand, in the automatic cooking mode, cooking is started by simply inputting the cooking menu through the setting unit 2 and the start key 24 is pressed, and when the cooking is done, the cooking is automatically completed using a heating detection means such as a sensor, a time control means, etc. It is something to do.

Now, the present invention relates to this automatic cooking mode. FIG. 2 is a block diagram showing the configuration of this heating cooker. 11 is a microcomputer,
It plays a central role in controlling the microwave oven, inputting commands from the setting section 2, timer setting section 3, and start key 24, and making judgments about the commands.As a result, it controls the heating output and heating time. , takes in sensor information, determines the heating state, etc. 15 is a magnetron for generating high frequency energy as heating output;
cools this magnetron 15 and heats the heating chamber 25.
This is a fan motor for ventilation. A heating output control section 14 controls the output of the magnetron 15 based on instructions from the microcomputer 11. Reference numeral 19 denotes a thermistor which indirectly detects the temperature rise due to heating of the food by detecting the temperature of the exhaust gas. 20 is a temperature detection circuit for converting the resistance change of the thermistor 19 into information that can be input to the microcomputer 11. A humidity sensor 18 detects the amount of water vapor generated as food is heated.

A humidity detection circuit 12 converts information from the humidity sensor whose resistance value changes depending on the amount of water vapor into information that can be input to the microcomputer 11.
has been established. Reference numeral 13 denotes an incineration cleaning control section for incinerating and cleaning contaminants adhering to the humidity sensor. Therefore, these two sensors, namely thermistor 19 and humidity sensor 18
is installed at the exhaust port of the heating chamber 25, so that the thermistor 19 detects temperature changes due to food heating, and the humidity sensor 18 detects changes in the amount of water vapor generated as the food is heated.

FIG. 3 shows a configuration diagram in which an infrared sensor 22 for detecting infrared rays generated as the temperature of food is used instead of the thermistor 19 installed at the exhaust port. 23 is an infrared detection circuit for converting information from the infrared sensor 22 into information that can be input to the microcomputer 11.

FIG. 4 shows a structural diagram of the humidity sensor 18. Reference numeral 5 denotes a moisture-sensitive resistance element, which has a characteristic of causing a change in electrical resistance due to the attachment and detachment of water vapor particles on its surface. Reference numeral 8 denotes electrodes coated on both sides of this moisture-sensitive resistance element. Reference numeral 6 denotes an incineration cleaning heater for incinerating and cleaning contaminants adhering to the humidity-sensitive resistance element 5. Reference numeral 9 denotes a heater terminal for fixing the incineration cleaning heater 6 to the sensor base 7 and connectable to a lead wire or the like. Reference numeral 10 denotes a humidity-sensitive resistance element terminal that fixes the humidity-sensitive resistance element 5 to the sensor base 7 and can be connected to a lead wire or the like.

FIG. 5 shows the characteristics of this humidity sensor. FIG. 5a shows the temperature characteristics when the relative humidity is approximately 0%, and FIG. 5b shows the humidity characteristics (relative humidity characteristics) at temperatures below 100°C. In cooking appliances such as microwave ovens, the ambient temperature of the humidity sensor is around several tens of degrees, even considering the heat generated by the magnetron and the temperature rise of the food, and is always below 100 degrees Celsius.

Therefore, the characteristics of the humidity sensor in this case are as shown in Fig. 5b.
The characteristics are shown as . On the other hand, in order to incinerate contaminants in the humidity sensor, it is necessary to heat it to a temperature of several hundred degrees (approximately 450 degrees Celsius) or higher, and in this case, the relative humidity becomes almost 0%, resulting in the characteristics shown in Figure 5a. That is, the change in the amount of water vapor generated from the food is detected by the characteristic change shown in FIG. 5b, while the control of the incineration temperature for cleaning by incineration is detected by the characteristic change shown in FIG. 5a. FIG. 5c shows an embodiment of the humidity detection circuit, in which a resistor is connected in series with the humidity-sensitive resistive element 5.
R _S is connected and the resistance change of the humidity sensitive resistive element 5 can be detected by the detection voltage Vd.

FIG. 6 shows a timing chart regarding control outputs and sensor information of each part of the cooking device.

In the figure, the horizontal axis t indicates the elapsed time, and t ₀ indicates the start time of cooking. Ph indicates energization of the incineration cleaning heater and is energized at the start of cooking. P _M indicates the high frequency output of the magnetron 15 and is heated from the start of cooking. _h1 is a signal of resistance change of the humidity sensor and corresponds to the voltage Vd shown in FIG. 5c. _h2 shows the part necessary for detecting the relative humidity of _h1 , and masks the information from the humidity sensor from the start of cooking to _t5 . Th indicates the temperature of the thermistor 19, and increases as the temperature of the food increases. Now, Ph, P _M , h ₁ , which I just mentioned here,
The changes in h ₂ and Th will be described based on the passage of time from t ₀ at the start of cooking.

At the start of cooking t ₀ , power supply Ph to the incineration cleaning heater 6 is started, and power supply P _M to the magnetron 15 for generating high frequency output is also started.
They will start almost at the same time. Electric power Ph is supplied to the incineration cleaning heater 6 to heat the humidity sensitive resistance element 5. As the temperature of the humidity-sensitive resistance element 5 rises, the relative humidity value approaches 0%, and the resistance value increases as shown in FIG. 5b.

This time is indicated by t ₁ in FIG. As heating continues, the temperature of the humidity-sensitive resistance element rises to over 100°C.
As shown in FIG. 5a, the resistance changes with temperature, and the resistance value becomes smaller. Then, h ₁ increases and Ph stops at a value corresponding to 450°C. In other words, the temperature of the humidity-sensitive resistance element is 450°C, which is sufficient to incinerate pollutants. Thereafter, since the temperature of the incineration cleaning heater 6 is high, the temperature rises a little even after Ph is stopped. After that, since the incineration cleaning heater 6 has a heat capacity, etc., it is not cooled down immediately, but the temperature gradually decreases. and,
The time of cooling to 100°C is indicated by _t3 . Then, as the temperature of the humidity-sensitive resistance element 5 is further cooled and returned to room temperature, the relative humidity is restored to normal. This is denoted by t ₄ . After t ₄ , the correct relative humidity of the exhaust can be measured. The microcomputer is then able to measure this normal relative humidity _.
It is only necessary to detect from the time point onward, so detection is usually started from time _t5 , which is slightly larger than _t4 . As the food is heated and the temperature rises, the relative humidity gradually decreases. This is because the rise in temperature in the heating chamber has a greater effect than the water vapor generated as the food is heated, so the relative humidity decreases. Then, from the time t ₆ , water vapor suddenly comes out from the food, so h ₁ also rises suddenly. Then, when the temperature rises by Δh from the minimum level (the level at t ₆ ), t ₇ is determined to be the predetermined heating state of the food. or
Th gradually increases as the temperature of the food increases,
This is why it is determined that the predetermined heating state is reached when there is a change in ΔTh from the temperature at _t8 , which is about 20 seconds after the start of cooking. In general, it is necessary to wear a mask until the ventilation and wind flow conditions become steady, but this is only for a short time, about 20 seconds, which is much shorter than the time that is impossible for humidity sensors. It is also a critical time for detection. The optimal detection widths Δh and ΔTh may be determined for the detection methods of the humidity sensor signal _h1 and thermistor signal Th, respectively, and priority may be given to the detection method using the signals. From the above, the period from incineration cleaning of the humidity sensor until it returns to room temperature, that is, from t ₀ to
Until t ₅ , relative humidity cannot be detected by the humidity sensor. Therefore, conventionally, for foods that reach a predetermined heating state between _t0 and _t5 , the output of the magnetron as a heating means has been stopped during this period. The magnetron started outputting from time _t5 . The period from t ₀ to _{t 5} is approximately 1 minute. Therefore, in the conventional method, time was lost from t ₀ to t ₅ and the cooking time was extended.

Therefore, in the present invention, by adding a thermistor or an infrared sensor, the thermistor detects the time when the humidity sensor cannot detect it, that is, from t ₀ to t ₅ , so that the magnetron is activated from the start of cooking. You can start outputting.

FIG. 7 shows the control of the microcomputer 11 from the start of cooking to the start of detection by the humidity sensor among the operations described above. First, start the output of the heating means (e.g. magnetron) from the start of cooking.
(A). At the same time, the humidity sensor is incinerated and cleaned (B). While the humidity sensor cannot detect the temperature due to this incineration cleaning, the heating state of the food is detected only by the thermistor (C). However, a short period of time from t ₀ to _{t 8} that does not affect the detection of the heating state of the food is masked. If a predetermined heating state is detected during that time (D), the process moves to subsequent control of heating output and heating time (H).

On the other hand, if the predetermined heating state is not reached, the thermistor continues detection until time _t5 when the humidity sensor returns to room temperature. Then, after _t5 has elapsed (E), the process moves to detection using both the thermistor and humidity sensor (F). If both sensors detect the specified heating state (G)
Then move on to controlling the heating output and heating time.
(H).

The above is the control content of the microcomputer 11 of this embodiment.

Next, FIG. 8 shows a specific example of the control circuit. The setting section 2, start switch 24, etc. are configured as a key matrix, which is scanned by sweep signals _S0 to _S4 and input to input ports _I0 to _I3 . 1 is a fluorescent display tube or the like as a display section. On the other hand, the heating output is controlled by output ports _R0 to _R2 ,
Turns on and off power to magnetrons, etc. via drivers, relays, etc. Further, A/D ₁ and A/D ₁ are input ports with an A/D conversion function for reading signals from a thermistor or humidity sensor as voltage signals. The incineration cleaning heater 6 is controlled by the _R4 port.

As described above, according to this embodiment, by incinerating and cleaning the humidity sensor, there is no longer a state where the humidity sensor cannot be detected, and even small foods can be detected. Moreover, the heating output does not have to be stopped when the humidity sensor cannot detect it, and cooking can be done in a shorter time than in the past. It has the above effects.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) Even when the humidity sensor is in an undetectable state due to incineration cleaning, detection with a thermistor makes it possible to detect even when the humidity sensor is in an undetectable state.

(2) Even if the humidity sensor becomes undetectable due to incineration cleaning, there is no need to stop the heating output, which reduces cooking time compared to conventional methods.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a heating device that is an embodiment of the present invention, Fig. 2 is a configuration diagram when the same thermistor is used, Fig. 3 is a configuration diagram when the same infrared sensor is used, and Fig. 4 FIG. 4a is a partial cross-sectional external perspective view of the same humidity sensor, FIG. 4b is a partial cross-sectional side view of the same sensor, and FIG.
Figures a to b are characteristic diagrams of the sensor, Figure 5c is a circuit diagram of the sensor, Figure 6 is a timing chart regarding the control output of each part and sensor information, and Figure 7 is a flow diagram showing the content of the control. 8 is a control circuit diagram using the same thermistor. 1...display section, 2...menu setting section, 3...
Timer setting section, 4... Door, 5... Moisture sensitive resistance element, 6... Incineration cleaning heater, 7...
Sensor base, 8... Electrode, 9... Heater terminal,
DESCRIPTION OF SYMBOLS 10... Humidity sensitive resistance element terminal, 11... Microcomputer, 12... Humidity detection circuit, 13... Incineration cleaning control section, 14... Heating output control section, 15... Magnetron, 16... Fan motor, 17 ...Food, 18...Humidity sensor, 19...
...Thermistor, 20...Temperature detection circuit, 21...
Buzzer, 22... Infrared sensor, 23... Infrared detection circuit, 24... Start key, 25... Heating chamber.

Claims (1)

[Claims] 1. A heating means for heating an object to be heated, a control section for controlling the heating means, and a first sensor means for detecting gas or water vapor generated as the object to be heated is heated. , a heater disposed close to the first sensor means to incinerate and clean contaminants adhering to the first sensor means, and a second sensor means to directly or indirectly detect the temperature of the object to be heated. A heating cooking device comprising: a heating device configured to control the heating device using the second sensor device when the first sensor device cannot detect the detection during incineration cleaning. 2. Claim 1 wherein the first sensor means is incinerated and cleaned at the start of cooking.
Heating cooker as described in section.