JPS643491B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for an electric rice cooker, and in particular, an object of the present invention is to make a mechanical lever type rice cooker switch section completely electronic.

Conventionally, an electric rice cooker that detects the completion of cooking using a temperature sensor that utilizes the Curie point of ferrite has a configuration as shown in FIG. 1.
In FIG. 1, 1 is an outer pot, 2 is an inner pot, 3 is a main heater, and 4 is a temperature sensor that uses the Curie point of ferrite, which loses its magnetic properties when the cooking time comes. Therefore, when the cooking temperature is reached, the magnet 5 separates from the temperature sensor 4 and falls, thereby opening the electrical contacts 8 and 9 via the transmission shaft 6 and lever type lever 7, and the main heater 3
The power supply to is stopped. Reference numeral 10 denotes a push button, and the push button 10 can open and close the electrical contacts 8 and 9 independently of the temperature sensor 4.

In the case of such a conventional structure, since the rice cooking switch part is mechanical, the structure is complicated and requires a large space at the bottom. Since it can be opened and closed, there are safety and operational issues.

The present invention solves these conventional drawbacks, and a control circuit for an electric rice cooker according to the present invention will be described below with reference to the drawings of FIGS. 2 to 4.

FIG. 2 shows the main parts of an electric rice cooker using the present invention, and in FIG. 2, 1 to 3 are the same parts as in FIG. 1. 11 is a first temperature sensor that detects the temperature inside the pot, 12 is a second temperature sensor that detects when the rice is cooked, and 13 is a sensor that detects when the first temperature sensor 11 has detected a specified temperature (for example, 40°C). 14 is a case that houses the control circuit section, which is a rice cooker switch whose control circuit section does not respond when the rice cooker switches.

FIG. 3 shows a control circuit of an electric rice cooker according to an embodiment of the present invention, in which 15 is a commercial power supply, 16 is a power switch, 17 is a rice cooking heater, 18 is a heat retention heater, and 19 is a relay for warming/rice cooking switching. The movable contact piece of the contact 19a of this relay 19 is connected to the commercial power supply 1 via the rice cooker heater 17 and the power switch 16.
5, one fixed contact is connected to the commercial power source 15 via the heat insulating heater 18, and the other fixed contact is directly connected to the commercial power source 15 as it is. 20 is a rectifier diode, 21 is a smoothing capacitor, 22 is a Zener diode, 23
is a current limiting resistor of this Zener diode 22. 24, 25 are D flip-flops, 26
is a switch indicating the operation of the first temperature sensor 11, and the operation of this switch 26 is stored by the D flip-flop 24. This switch 26
When ON, a positive pulse is input from the clock input terminal, the rising edge of the positive pulse is detected, and the output terminal is set to the LOW (hereinafter referred to as "L") level. Reference numeral 27 denotes a transistor whose emitter is connected to the clear terminals of the D flip-flops 24 and 25, and this transistor 27 is used for initial reset when the power is turned on. 28 is a base current limiting resistor connected to the base of this transistor 27, 29 is a capacitor, and resistor 3
This is to control the switching of the transistor 27 using a time constant of 0 and to determine the reset time. 31 is a diode for instantaneously discharging the charge of this capacitor 29 when the power switch 16 is turned off. 32 is the above D
The pull-up resistor 33 of the clear terminals of flip-flops 24 and 25 is an AND gate.
The AND gate 33 is connected to the D flip-flop 24.
The output of the rice cooker switch 13 is ANDed with the output of the rice cooker switch 13. That is, when the switch 26 corresponding to the first temperature sensor 11 is activated, the output of the D flip-flop 24 changes from the HIGH (hereinafter referred to as "H") level to "L", and the rice cooking becomes one input of the AND gate 33. Even if switch 13 is turned on, a positive rising pulse does not enter the input terminal of D flip-flop 25. Furthermore, the D flip-flop 25 feeds back the inverted output to the D input terminal, and the output is inverted every time a positive rising pulse is input to the clock input terminal.
Flip-flop 25 does not operate. Reference numeral 34 denotes a transistor whose base is connected to the output terminal of the D flip-flop 25 via a resistor 35. When this transistor 34 is turned on and off, the relay 19 is energized and turned off, and rice cooking and warming are switched. A diode 36 is connected in parallel to the relay 19, and is used to discharge the back electromotive force generated in the relay 19. A switch 37 indicates the operation of the second temperature sensor 12, and a diode 38 is connected in series with the switch 37. The output of the D flip-flop 25 is connected to the switch 37 and the diode 3.
8 to the clock input terminal, and when the second temperature sensor 12 is activated during rice cooking and the switch 37 is turned on,
The output of the D flip-flop 25 is reversed, the relay 19 is turned OFF, and the rice cooking mode is switched to the warming mode. That is, once the switch 37 is turned ON and the D flip-flop 25 is inverted, the output becomes "L", so even if the switch 37 is repeatedly turned ON or OFF again, there will be no positive signal at the clock input terminal. Since a rising pulse cannot be obtained, turn off the power switch 16 and then turn it back on.
The rice cooking switch 13 will not respond unless the operation is turned on and the initial reset is performed using the transistor 27.

Next, the operation of the control circuit of the present invention having the above configuration will be explained using the timing chart shown in FIG.

In the above configuration, first turn on the power switch 16.
When turned on, current flows from the resistor 32 through the emitter of the transistor 27, from the resistor 28 to the capacitor 29, the clear terminal of the D flip-flop 24 becomes "L" level, and the transistor 2
As the emitter current of 7 decreases, it becomes "H" level, and the initial reset is completed. As a result, the inverted output of the D flip-flop 24 becomes "H".
Therefore, the output of the D flip-flop 25 is “L”,
Since the inverted output is "H", the transistor 34 remains OFF. Therefore, since the relay 19 is not energized and does not operate, the contact 19a
remains on the heat retention heater 18 side.

Next, when the rice cooker switch 13 is temporarily turned on, both inputs of the AND gate 33 become "H", so a positive rising pulse is input to the clock input terminal of the D flip-flop 25, and the output changes from "L" to " This causes the transistor 34 to be driven and the relay 19 to be energized.
The relay 19 operates, the contact 19a switches, and the rice cooking heater 17 is energized. Here, when the rice cooking switch 13 is pressed again, the D flip-flop 25 is reversed and the output changes from "H" to "L", and the power to the relay 19 is cut off, resulting in a warm state. That is, until the switch 26 of the first temperature sensor 11 is activated, the rice cooking switch 13 can be used to freely switch between cooking and keeping the rice warm.

Next, when the first temperature sensor 11 detects the specified temperature and operates, a positive rising pulse is input to the clock input terminal of the D flip-flop 24, the output changes from "H" to "L", and the switch 26 Memorize the operation of. Therefore, even if the rice cooking switch 13 is pressed, the output of the AND gate 33 does not become "H", and the clock input to the D flip-flop 25 is prohibited, locking the rice cooking state.

Next, when the second temperature sensor 12 detects that the rice is cooked and the switch 37 is turned on, the output of the D flip-flop 25 is "H" and the rice is in the cooking state, so a positive rising pulse is sent to the clock input terminal when the switch 37 is turned on. 37 is ON, and the output changes from "H" to "L". Therefore, the relay 19 is turned off, and the contact 19a is also switched to enter the heat retention state.
Here, even if the rice cooking switch 13 is pressed or the switches 26 and 37 are turned ON or OFF, the heat retention state remains completely maintained.

As described above, according to the control circuit of the present invention, when the power switch 16 is turned on, the rice is kept warm, and when the rice cooking switch 13 is then temporarily turned on, the heating heater 18 is switched to the rice cooking heater 17, and the rice cooking switch 13 is turned on again. When turned on, the rice cooker returns to the keep-warm state, and when the rice cooking switch 13 is turned on again, the rice cooking state resumes.When the first temperature sensor 11 detects the specified temperature, the rice cooker switch 13 is pressed.
Even if it is turned on, it will not respond. Furthermore, when the second temperature sensor 12 detects that the rice is cooked, it switches from cooking to keeping the rice warm, but it does not respond even when the rice cooking switch 13 is turned on. Here, turn the power switch 16 once.
When turned off and turned on, the first warming state is entered, and when the rice cooking switch 13 is turned on, the heating heater 18 is switched to the rice cooking heater 17. That is, in the present invention, when the temperature inside the pot exceeds a certain specified temperature,
Once the rice cooking state is maintained and once the temperature sensor for detecting the rice is cooked is activated and the rice is kept warm, there is no response even if the rice cooking switch 13 is turned on again.

As described above, according to the present invention, the rice cooking switch section in an electric rice cooker can be fully electronic,
Moreover, when the temperature inside the pot rises to a specified temperature or higher during cooking, or when the rice is kept warm after cooking, it is possible to lock the state.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the main parts of a conventional electric rice cooker, FIG. 2 is a cross-sectional view showing the main parts of the electric rice cooker according to the present invention, and FIG. 3 is a cross-sectional view showing the main parts of the electric rice cooker according to an embodiment of the present invention. An electric circuit diagram showing the control circuit, and FIG. 4 is a timing chart for explaining the operation of the circuit. 11... First temperature sensor, 12... Second temperature sensor, 13... Rice cooking switch, 17... Rice cooking heater, 18... Heat retention heater, 19... Relay,
19a... Contact, 24, 25... D flip-flop, 26, 37... Switch, 33... AND
Gate.

Claims (1)

[Claims] 1. A first temperature sensor that detects the temperature inside the pot;
a second temperature sensor that detects when the rice is cooked; and a second temperature sensor that controls power supply to the rice cooking heater based on signals from the first and second temperature sensors and a rice cooking switch; 1. A control circuit for an electric rice cooker, comprising: a control circuit section that detects a specified temperature and maintains that state without responding to a signal from the rice cooker switch.