JPH0237164B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a control circuit for an electric cooker used in a general household, and in particular has a microcomputer that stores the rice cooking process, and turns on and off the heater using a relay. This invention relates to an electric jiyar rice cooker that adjusts the heat by turning it off.

Conventional structure and its problems Conventionally, in this type of electric Jiyar rice cooker,
As shown in Fig. 1, a switch 2 that responds to a thermostat that detects the completion of rice cooking is connected to a control circuit 1 having a microcomputer, and this signal instructs the microcomputer to perform operation classification between rice cooking and keeping rice warm. was. However, according to this configuration, a separate input signal switch 2 is required, and since a relay 4 is connected in series to the main heater 3, the relay 4 is turned on and off in order to adjust the thermal power. This has the disadvantage that the number of operations of the relay 4 increases, and if a failure occurs in the relay, the reliability of the main body decreases.

For example, if the contacts of relay 4 are welded,
The main heater 3 is continuously energized, and the temperature fuse 5 is blown out. Further, it becomes impossible to input a signal indicating that the rice cooking operation is in progress to the microcomputer as a signal.

OBJECTS OF THE INVENTION The present invention solves these conventional problems and aims to provide an electric jar rice cooker having an electric circuit with improved reliability.

Structure of the Invention In order to achieve the above object, the electric jar rice cooker of the present invention includes a main body, a lid provided on the top surface of the main body so as to be openable and closable, a pot removably housed in the main body, and the main body. A lower heater installed at the inner bottom of the
A side heater provided on the inner surface of the main body, a lid heater provided inside the lid, a microcomputer that stores the rice cooking process, a relay that controls the lower heater, and a reverse heater that detects the end of rice cooking. and a heat-sensitive switch having contacts, and the relay, the lower heater, and the main contact of the heat-sensitive switch are connected in series during rice cooking, and the reverse contact of the heat-sensitive switch is connected to the microcomputer to control the rice cooking operation. The configuration is such that input is performed.

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

In FIG. 2, 11 is a lid heater provided inside a lid (not shown) that can be opened and closed on the top surface of the main body (not shown), 12 is a lower heater provided at the bottom of the main body, and 13 is a main body. When cooking rice, the lower heater 12 and the side heater 13 are energized to cook rice. Reference numeral 14 denotes a triax, which controls the temperature by energizing the series circuit of the lid heater 11, lower heater 12, and side heater 13 during heat retention.

15 is a heat sensitive switch, this heat sensitive switch 15
One contact 15a is a relatively large silver contact in order to interrupt the current. Further, since the other contact 15b is connected to the active element via the diode 16, the current is small, and the contact is small and gold-plated.

The heat-sensitive switch 15 is connected to one contact 15a when cooking rice, and is switched to the other contact 15b when keeping rice warm. 17 is a relay for energizing the lower heater 12;
has one contact 17a that is connected when keeping the rice warm, and the other contact 17b that is connected when cooking rice. Reference numerals 18 and 16 denote a resistor and a diode connected to the reverse contact of the heat-sensitive switch 15, that is, the other contact 15b, and these input the rice cooking operation to the microcomputer 19 which stores the rice cooking process.

20 is a temperature sensor, this temperature sensor 20
The system measures temperature gradients in order to control temperature during warming and determine cooking capacity during rice cooking. 21 is a pot detachably housed in the main body;
Reference numeral 2 denotes a temperature detection section consisting of a center thermostat disposed so as to be in contact with the bottom of the pot 21, and this temperature detection section 22 turns on the heat sensitive switch 1 when rice cooking is completed.
5 from one contact 15a side to the other contact 15b side.

The relay 17 is opened and closed by a drive signal from the microcomputer 19 for power control, and during rice cooking, the relay 17
The other contact 17b, the lower heater 12, and one contact 15a of the heat-sensitive switch 15 are connected in series, and with this configuration, if the contact of the relay 17 is welded, the rice will not be cooked. The temperature of the container 21 will rise, but in this case, when the temperature detection unit 22 consisting of a center thermostat operates, the heat sensitive switch 15 switches from one contact 15a to the other contact 15b in response. Since the power supply to the lower heater 12 can be cut off before the temperature fuse 23 is cut off, reliability can be improved.

FIG. 3 shows the circuit of FIG. 2 in more detail.

The heat-sensitive switch 15 has the other contact 15b connected to the resistor 1.
8 and the base of an active element transistor 24 via a diode 16. With this configuration, the current flowing through the other contact 15b of the heat-sensitive switch 15 becomes a half wave, so by providing a time constant with the capacitor 25, the output of the transistor 24 becomes a direct current.

Based on the output of the transistor 24, the temperature of the temperature control circuit A composed of a voltage comparator 26, a thermistor 27, a transistor 28, etc. can be changed by turning the transistor 28 ON and OFF. can.

When one contact 15a of the heat-sensitive switch 15 is connected, the rice cooking operation is performed, and
When the other contact 15b is connected, a heat-retaining operation is performed. When the one contact 15a is connected to start the rice cooking operation, the temperature control circuit A and timer circuit B in FIG. 3 operate to maintain the rice at a constant temperature for a certain period of time.

On the other hand, when rice cooking is finished, the heat-sensitive switch 15 is switched to the other contact 15b, and this other contact 15b is connected to the base of the transistor 24 via the diode 16 and the resistor 18, so the transistor 24 is not connected to the other contact 15b. A wave current flows, but since a time constant is secured by the capacitor 25, the output of the transistor 24 is converted into a DC signal. As a result, the control temperature of temperature control circuit A is changed to the control temperature for keeping warm, and the operation of timer circuit B is prohibited.

Further, the output of the transistor 24 turns on the transistor 29, and the relay drive transistor 30
is held off, so the relay 17 switches to one contact 17a side. As a result, the configuration of the heater becomes a circuit configuration for a heat-retaining operation in which the side heater 13, the lower heater 12, and the lid heater 11 are connected in series.

Effects of the Invention As is clear from the description of the above embodiments, according to the present invention, during rice cooking, a lower heater, a relay that controls the lower heater, and a heat-sensitive switch that detects the end of rice cooking are connected in series. Because of this structure, even if the relay contacts become welded,
Before the temperature fuse is cut off, the heat-sensitive switch always operates to cut off the power to the lower heater.
It is possible to provide an electric rice cooker that can ensure high reliability even when the relay adjusts the heat power during rice cooking and increases the number of times the relay is turned on and off. In addition, since the reverse contact of the heat-sensitive switch is connected to the microcomputer to input the rice cooking operation signal, even in the event of an abnormality, the rice cooking operation completion signal can be output to the microcomputer, further increasing safety.

[Brief explanation of drawings]

Fig. 1 is an electric circuit diagram of a conventional electric jiyar rice cooker, Fig. 2 is an electric circuit diagram of an electric jiyar rice cooker showing an embodiment of the present invention, and Fig. 3 is a specific electric circuit diagram of the electric jiyar rice cooker. It is a circuit diagram. 11...Lid heater, 12...Lower heater, 13
...Side heater, 15...Heat-sensitive switch, 17...
...Relay, 19...Microcomputer, 21
……pot.

Claims (1)

[Claims] 1. A main body, a lid provided on the top surface of the main body so as to be openable and closable, a pot removably housed in the main body, a lower heater provided on the inner bottom of the main body, and a lid heater provided on the inner surface of the main body. , a microcomputer that stores the rice cooking process, a relay that controls the lower heater, and a heat-sensitive switch with a reverse contact that detects the end of rice cooking. The contacts are connected in series, and the reverse contact of the thermal switch is connected to the microcomputer,
An electric jar rice cooker configured to input a rice cooking operation signal.