JPS6110570Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a cooking device such as an electric rice cooker, and more particularly to a control device that stops the operation of the heating means when the temperature detection means for detecting the temperature of a container storing food to be cooked fails. .

As a conventional cooking device, for example, there is an electric rice cooker shown in FIGS. 1 and 2.

In the figure, 1 is the outer pot of the electric rice cooker, 2 is the inner pot as a container for storing food such as rice, and 3 is disposed inside the outer pot 1 facing the outer bottom surface of the inner pot 2. 4 is a rice cooking heater as a heating means; 4 is a semiconductor sensor provided in close contact with the outer bottom surface of the inner pot 2 and has a built-in negative characteristic thermistor as a temperature detection means for detecting the temperature of the inner pot 2; 5 is a signal from the semiconductor sensor 4; 6 is a comparator that outputs a signal when it detects the rice cooking completion temperature by obtaining the signal from the semiconductor sensor 4, detects a predetermined temperature below the rice cooking completion temperature and outputs a signal, and the semiconductor sensor 4
It is determined whether the sensor 4 is disconnected by detecting a change in resistance due to temperature rise. 7 is a control device having an AND function that outputs no signal when both signals are received from the comparators 5 and 6 or when neither signal is received, and outputs a signal otherwise; 8 is connected in series to the rice cooking heater 3; This is a triax that operates ON-OFF when a signal from the control device 7 is input to the gate G. When the signal from the control device 7 is output, it becomes ON and energizes, while the control device 7
When no signal is output from the device, it becomes OFF and de-energized. 9 is rice cooking heater 3 and triax 8
A commercial power supply connected to a series circuit consisting of

In the electric rice cooker having such a configuration, two comparators 5 and 6 are used to detect the rice cooking completion temperature and the disconnection of the sensor 4 from the signal of the semiconductor sensor 4 that detects the temperature of the inner pot 2, so the number of parts is large. This was causing an increase in costs.

The present invention has been developed in view of the above points, and is a series of steps in which the set temperature of the comparator is changed to a desired temperature lower than the cooking completion temperature for a predetermined time according to the elapsed cooking time, and then switched to the cooking completion temperature after the elapse of the predetermined time. The above-mentioned conventional problems are solved by making the comparator determine the completion of cooking and the state of disconnection of the temperature detecting means.

An embodiment of the present invention will be described below with reference to FIGS. 1, 3 to 5. Incidentally, the same elements as those in the conventional example are given the same reference numerals and the explanation thereof will be omitted.

In the figure, 10 is a comparator that receives a signal from the semiconductor sensor 4 and outputs a signal when a predetermined temperature is detected, and 11 receives a constant frequency signal from the commercial power supply 9 and a signal from the comparator 10 to turn on the triac 8. It is a microcomputer having a CPU, ROM, and RAM as a control means for OFF control and operation/stop control of the rice cooking heater 3.

This microcomputer 11 counts the wave number of the signal from the commercial power supply 9 at the start of rice cooking, and measures the elapsed temperature after the start of rice cooking. Then, this computer 11 serves as a set temperature switching means for the comparator 10 and instructs the comparator 10 to change the set temperature to a desired temperature TE ₁ lower than the cooking completion temperature TE ₂ in order to detect the elapsed cooking temperature, for example, time T ₁ in FIG. 4. Set a predetermined time.

At this time, semiconductor sensor 4, which is normally input at all times,
If the comparator 10 detects a temperature equal to or higher than the desired temperature TE1 based on the signal from the comparator ₁₀ , the comparator 10
outputs a signal and gives a command to the microcomputer 11 to keep the triator 8 in the ON state, and rice cooking continues. And even after that,
After a predetermined time, that is, several seconds, the microcomputer 11 switches the set temperature to the rice cooking completion temperature, and then changes the set temperature at a certain period (for example, 1
The temperature is changed to the desired temperature for detection by the comparator 10 in minutes), and a series of switching operations are performed to monitor the semiconductor sensor 4 for disconnection. At this time, if the comparator 10 detects a temperature higher than all of the desired temperatures, it is confirmed that the semiconductor sensor 4 is operating normally, and the rice cooking operation continues until the inner pot 2 reaches the rice cooking completion temperature. Reach TE ₂ .
This is detected by the comparator 10 via the sensor 4, and the triax 8 is turned off via the microcomputer 11, completing the rice cooking operation. Incidentally, it is essential that all of the above-mentioned desired temperatures be lower than the temperature value at the relevant time of the temperature rise characteristic of the semiconductor sensor 4 during normal rice cooking operation and higher than the ambient temperature, regardless of the ambient temperature.

On the other hand, if the comparator 10 detects a temperature lower than any of the desired temperatures based on the signal from the semiconductor sensor 4, it detects that the semiconductor sensor 4 is disconnected, and turns on the triac 8 via the microcomputer 11.
The rice cooker heater 3 is turned off and the rice cooking operation is stopped. This prevents the inner pot 2 from overheating.

In the above example, time was measured by counting the wave number of a constant frequency signal of a commercial power supply, but crystal,
A similar effect can be obtained by counting the number of waves of a constant oscillation frequency signal from a ceramic or CR oscillator.

As explained above, according to the present invention, the set temperature of the comparator is changed to a desired temperature lower than the cooking completion temperature for a predetermined period of time according to the elapsed cooking time, and the set temperature is changed to the cooking completion temperature after the elapse of the predetermined time. Since the comparator determines the completion of cooking and the state of disconnection of the temperature detecting means, the heating means can be reliably stopped when the temperature detecting means is disconnected.

As a result, it is no longer necessary to provide a comparator for detecting disconnection of the temperature detecting means separately from the conventional comparator for detecting the completion of cooking, so it is possible to reduce the number of parts and provide an inexpensive cooker. Can be done.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of an electric rice cooker, Fig. 2 is a conventional control circuit diagram for the same rice cooker, Fig. 3 is a control circuit diagram of an electric rice cooker that is an embodiment of the present invention, and Fig. 4 is a diagram of a conventional control circuit for the same rice cooker. FIG. 5 is a temperature rise characteristic diagram of the semiconductor sensor of the above rice cooker, and FIG. 5 is a generation characteristic diagram of a command pulse to detect a disconnection of the semiconductor sensor of the above rice cooker. 2... Inner pot, 3... Rice cooking heater, 4... Semiconductor sensor, 8... Triack, 9... Commercial power supply, 10... Comparator, 11... Microcomputer.

Claims (1)

[Scope of utility model registration request] A cooking device comprising a container for storing a food to be cooked and a heating means for heating the food to be cooked through the container, a temperature detection means for detecting the temperature of the container and outputting a signal, and a temperature detection means for detecting the temperature of the container and outputting a signal. a comparator that receives a signal from the means and outputs a signal when it determines that the detected temperature is higher than the set temperature; and a comparator that changes the set temperature of the comparator to a predetermined temperature that is lower than the cooking completion temperature for a predetermined period of time according to the elapsed cooking time, and for the predetermined period of time. A set temperature switching means that performs a series of switching operations to switch to the cooking completion temperature after the cooking completion temperature, and a control means that receives a signal from the comparator and controls the activation and stopping of the heating means, are provided, and the set temperature switching means changes the set temperature. The cooking appliance is characterized in that the heating means is stopped when the comparator, which is set to the desired temperature, determines that the detected temperature at the cooking elapsed temperature is less than the set temperature.