JPS5953050B2 - Microcomputer controlled thermal rice cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an MPU heat-retaining rice cooker in which a microcomputer (hereinafter referred to as MPU) controls the pot temperature during rice cooking and heat-keeping.

As shown in FIG. 1, the conventional MPU heat-retaining rice cooker includes a TRIAC element TR1 that controls the rice-cooking cast-in heater 4 and a TRIAC element TR that controls the heat-retaining heater 27.
2 is controlled by a signal from the MPU, and the MPU is also supplied with a signal from a rice cooking switch that turns the contact switch ON-OFF by the operation of a center thermostat composed of a ferrite and a magnet.

When the rice-cooking button is pressed, a signal from the contact switch is input to the MPU, and in response to this, the MPU makes the IAC element TR1 conductive and starts energizing the rice-cooking heater 4.

When the temperature inside the pot reaches point III in Figure 4 after a predetermined period of time has passed, the center thermo is activated and the contact switch is turned off.
FF, and in response to this, the MPU or the IC element TR
1 becomes non-conductive.

Pulse-like noise is generated by the opening/closing operation of the contact switch at this time, which enters the MPU and gives the triac TR1 a re-cooking start signal to start from point IV in Figure 4, for example, and the rice cooker starts. Causes malfunction.

In addition, since the temperature of the pot during rice cooking is only detected by a heat-responsive switch, it is not possible to obtain signals corresponding to various conditions related to the amount of rice and the quality of rice, making it difficult to perform precise control. is not possible.

Furthermore, since the rice-cooking heater and the warming heater are controlled by separate electronic switching elements, two large-capacity switching elements are required, which is disadvantageous in terms of cost and space.

An object of the present invention is to provide an MPU-controlled heat-retaining rice cooker that eliminates the problems that such conventional MPU-controlled heat-retaining rice cookers have.

Next, an embodiment of the present invention will be described based on FIGS. 2 and 3.

The main body 1 protects the outer pot 2, and the upper edge of the upper frame 3 protects the main body 1.
and the outer pot 2 are thermally insulated.

A pot 5 is placed on top of a cast-in heater 4 which is the main power source during rice cooking.

At the center of this pot 5, a chain-side sensor 6 composed of a temperature-measuring resistor such as a thermistor is arranged.

In conventional heat-retaining rice cookers, the center thermostat was located at this location and operated only on the ferrite cue point 1.

An inner lid 7 covers the upper edge of the pot 5 to prevent heat from escaping.

An outer cover 8 is placed over the top of the inner cover 7 to increase thermal efficiency during heat retention, and the outer cover 8 is provided with a handle 9, and a cover heating element 28 is held in the center. .

The outer lid and the inner lid are connected to a hook 11 by a hook lever 10 for locking or releasing them.

The handle is firmly supported by a hinge 12,
A hinge cover 13 is attached to this hinge 12.

The dew that falls when the inner lid 7 is opened is collected from the dew pan 14.
Uke is taken.

The surface of the display board 16 is neatly covered by the decorative board 15.

The additional cooking switch 17 is a changeover switch used for additional cooking, and the rice cooking switch 18 is a switch using a snap action, which is turned on by operating the rice cooking button 19, and controls the resistance change of the chain side sensor 6. The unit will detect it and turn it off with a future signal.

20 is a protection switch. The heat shield plate 21 blocks heat from the cast-in heater 4.

22 is a control unit which will be described later, and 23 is an electronic switching element such as a triac element or SCR.

24 is a back plate, 25 is a leg, 26 is a main body insulating material, and also a heat retention heater 27, a cast-in heater 4, a triac 23,
It is connected in series with the rice cooking switch 18, and a temperature fuse 29 is pressed against the protective frame 2 in case of an emergency failure.

Next, the functions of the control unit which form the main part of this invention will be explained together with its operation.

When the rice cooking button 19 is pushed downward, the rice cooking switch 18 and the heat retention switch 20 are turned on, a contact circuit is formed at a-a, d-e, and the cast-in heater 4 and the lid heating element 28 are energized. The heat-retaining heater 27 is not energized.

Then, when the casting heater 4 is energized, the temperature of the pot is detected by the pot sensor 6, and the MP temperature remains unchanged until the temperature reaches one point in FIG.
According to U's instructions, the rice continues to be cooked with low heat, controlling the temperature of the rice to not exceed 40 degrees Celsius, and allowing the rice to absorb enough water.

After this process continues for a certain period of time, the triac element 23 is controlled by a command from the MPU, and full power is supplied to the casting heater 4.

At this time, the time T for transition from temperature t1 to t2 in FIG.

is detected by the resistance change of the chain side sensor 6, and this time T.

Based on this, the MPU calculates rice cooking conditions, such as the amount of rice to be cooked, and supplies electric power corresponding to this to the casting heater 4 to continue cooking rice up to point II in FIG. 4 with this electric power.

Then, when the temperature of the pot continues to be 100°C for a certain period of time, the above-mentioned time T is reached.

Based on the results calculated by the MPU based on
Only 30% of the power is supplied to the cast heater.

When this state continues for a certain period of time and the rice absorbs water and the temperature of the pot 5 rises and reaches the temperature III in FIG. 4, the control unit 22 detects this by the resistance change of the chain side sensor 6. Then, a signal is sent to the triac element 23 to temporarily stop energizing the casting heater 4.

If this state continues for a certain period of time, the temperature of the pot will rise to II in Figure 4.
When it descends to point I, the control unit 22 detects this by the resistance change of the chain side sensor 6, and sends a signal to the triac element 23 again to energize the casting heater 4 to execute reheating.

This "additional cooking" is the process of stopping the heating just before the rice is completed and then reheating it after a period of time to remove moisture from the surface of the rice and promote alpha-ization of the rice. It gives the rice its aroma.

After this re-energization, when the bottom temperature of the pot 5 rises again and reaches point V in FIG. Sent.

This signal makes 5CR30 conductive, energizes the solenoid of the rice cooking switch 18, and the rice cooking switch 18
contacts are reversed.

Therefore, in the contact circuit of the rice cooking switch 18, only the terminals a-C are conductive, and the heat-retaining heater 27 is connected in series with the cast-in heater 4, and the rice-cooking switch 18 is switched to the heat-retaining state.

Point VI in FIG. 4 is the point at which unevenness is completed, which is detected by the chain-side sensor 6 and notified by the buzzer, and the heat retention state starts from point VII.

As mentioned above, in the MPU-controlled heat-retaining rice cooker of the present invention, the temperature at the bottom of the pot is continuously detected by a temperature-measuring resistance element such as a thermistor, so the pot is heated with electricity according to the amount of rice cooked and the rice cooking conditions. Heating is performed, the accuracy of rice cooking control is improved, and the accuracy of temperature control during keeping warm is also improved.

Further, since there is only one electronic switching element for controlling the casting heater and the heat-retaining heater, reliability is improved and cost and space are saved.

Furthermore, in the conventional rice cooker, III in FIG.
At this point, the rice cooking switch consisting of a contact switch was turned off by the thermostat, but in this invention, the temperature at the bottom of the pot is continuously detected.
It becomes possible to turn off the contact switch at the point,
Therefore, there is no influence of noise caused by the operation of the contact switch, preventing malfunctions and improving practicality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a control circuit of a conventional MPU-controlled heat-retaining rice cooker. FIG. 2 is a sectional view of the MPU-controlled heat-retaining rice cooker of the present invention, and FIG. 3 is a diagram showing a control unit of the MPU-controlled heat-retaining rice cooker of the present invention. FIG. 4 is a rice cooking curve in the MPU-controlled heat-retaining rice cooker of the present invention. 1: Main body, 2: Outer pot, 3: Upper frame, 4: Cast heater, 5
: Pot, 6: Chain side sensor, 7: Inner lid, 8: Outer lid, 9: Handle, 10: Hook lever, 11: Hook, 12: Hinge, 13: Hinge cover, 14: Dew catcher, 15: Decorative board , 16: Display board, 17: Additional cooking switch, 18: Rice cooking switch, 19: Rice cooking button, 20: Protection switch,
21: Heat shield plate, 22: Control unit, 23: Triac element, 24: Back plate, 25: Legs, 26: Main body heat shield material, 2
7: Heat retention heater, 29: Temperature fuse.

Claims (1)

[Claims] 1 A heat-retaining heating element is provided on the side of the protective frame, and a rice-cooking heating element is provided at the bottom of the protective frame, and the heat-retaining heating element and the rice-cooking heating element are connected in series via an electronic switching element such as a triac or SCR. A rice-cooking switch is connected to both ends of the heat-retaining heat generating element for forming and releasing a flow path, and a rice-cooking switch is connected to the heat-retaining heat generating element, the electronic switching element, and the rice-cooking heat generating element. A switch mechanism for controlling the rice cooking switch is connected in parallel to the series circuit consisting of the rice cooker, and various situations are determined by receiving signals from a chain-side sensor such as a thermistor that continuously detects the temperature at the bottom of the pot. A signal from a microcomputer,
A microcomputer-controlled heat-retaining rice cooker, characterized in that the electronic switching element and the switch mechanism are controlled.