JPS6249051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric rice cooker, and particularly to an electric rice cooker that can automatically perform uneven heating.

When cooking rice using this type of electric rice cooker,
A non-automatic return switch controls the predetermined cooking completion temperature.

In other words, this switch is attached to the outer bottom of the inner pot that stores the rice, and when the rice is cooked, it senses a predetermined temperature and automatically opens the contact, and at this point the rice cooking is complete. .

However, in such a conventional configuration, after rice cooking is completed and the switch is opened, power is not supplied to the inner pot, so the temperature of the cooked rice in the inner pot decreases.
The drawback was that the free water remaining in the cooked rice was blown away, and it was not possible to supply enough heat for the gelatinization of the starch in the rice to proceed.

Therefore, in view of the above-mentioned conventional situation, the present invention detects the cooking completion point of the rice in the container regardless of the amount of rice cooked, and then heats the rice with low heat to effectively prevent uneven heating. To provide an electric rice cooker that promptly eliminates the above-mentioned drawbacks.

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 13.

1 is the electric rice cooker body, 2 is the inner pot that stores the rice,
4 is a sensor with a built-in thermistor as a temperature detection device attached closely to the bottom wall of the inner pot 2; 5
6 is an operation panel attached to the electric rice cooker main body 1, and 6 is a rice cooker provided on the panel 5.
7 is an on/off switch for cooking rice porridge provided on the operation panel 5; 8 is an on/off switch for keeping warm operation provided on the panel 5; 9 inputs a signal from the sensor 4, which will be described later. A comparator whose operating point is adjusted by a microcomputer 12; 10 is a commercial power source for operating the electric heater 3; 11 is a triax connected in series with the commercial power source 10 and the heater 3; a signal is input to its gate G; When a signal is input, it turns on (conducting), and when no signal is input, it turns off (blocking).

12 stores the strength order of heat generation of the heater 3 according to the cooking selected by the rice cooking on/off switch 6 and the rice porridge cooking on/off switch 7, which function as cooking switching means, and outputs the heat from the sensor 4. as a control device that detects the rate of temperature rise based on the signal of the controller, determines the selected cooking amount, and controls the operating time of each step of the heat generation procedure according to this amount;
A microcomputer equipped with a CPU, ROM, and RAM counts the wave number of the commercial power supply 10 and measures time.

That is, for rice cooking, this microcomputer 12 issues operating commands for high heat power P _H , medium heat power P _M , low heat power P _L , and steaming power P _B in order, while for rice porridge cooking, it issues high heat power P _H and low heat power in order. The operating time of the _heater 3 at each stage in the order of strength obtained through the sensor 4 is controlled by sending a signal to the gate G of the triac 11.

In addition, the power control here adopts the energization rate control method, for example, when the energization rate is 100%, it is a high flame power,
Set medium heat power when the power is between 30 and 99%, and low heat power when the power is 29% or less.

In this configuration, in the case of rice cooking, rice, water, etc. are first put into the inner pot 2, and when the rice cooking on/off switch 6 is turned on, the microcomputer 12
receives the rice cooking command and sends a signal to gate G of triax 11. As a result, the triax 11 is turned on, the heater 3 starts operating, and the inner pot 2
is heated with high flame electric power P _H as shown in Fig. 4. Then, when the temperature of the inner pot 2 rises and the detection signal of the sensor 4 reaches the operating point temperature Ta of the comparator 9, the comparator 9 sends a signal to the microcomputer 12, and the microcomputer 12
Comparator 9 starts counting the wave number of
Set the operating point of to temperature Tb.

When the temperature of the inner pot 2 further increases and the temperature detected by the sensor 4 reaches the operating point temperature Tb of the comparator 9 again as shown by the solid line in FIG.
The heating time required for the temperature to reach the operating point temperature Ta, Tb
Determine t ₁ from the number of counts of the wave number, and calculate this time
From this point on, depending on the length of _t1 , that is, the amount of rice cooked,
The cooked rice in the box has a temperature of A shown in the dashed line in Figure 5.
The heating time t ₂ until the boiling point starts (approximately 98.5° C.) is selected from the memorized diagram in FIG. 6, and the heater 3 is continued to be controlled at high flame power P _H . Then, the microcomputer 12 uses the timer function to set the time.
When it is determined that t ₂ has elapsed, the high heat power P _H control is stopped, and the heater 3 is tried 11 to the medium heat power P _M having the power corresponding to the heating time t ₁ , that is, the amount of rice to be cooked, as shown in FIG. Begin controlling the current flow through the boiler and maintain boiling to the extent that it does not boil over.

On the other hand, the rice cooking completion temperature should be changed depending on the amount of rice being cooked.For example, when cooking a large amount of rice, if the rice cooking completion temperature is not very high, proper charring will not be possible and there will be too much free water in the rice. α of starch
The microcomputer 12 stores the characteristics shown in FIG. The heating time _t1 , that is, the appropriate rice-cooking completion temperature according to the amount of rice to be cooked, is selected as follows, and the operating point of the comparator 9 is changed to the selected rice-cooking completion temperature. The medium-heat power P _M operation continues, and the temperature detected by the sensor 4 exceeds the rice cooking completion temperature (for example, temperature Td), and the comparator 9
When the microcomputer 12 outputs a signal, the microcomputer 12 receives this signal and starts controlling the energization of the heater 3 to the low-heat power P _L for the steaming and heating process via the triax 11. The power value of this low heat power P _L and the heating time t ₃ using this power should be determined according to the heating time t ₁ , and the low heat power P _L and heating time are determined based on the heating time t ₁ , that is, the amount of rice cooked. By changing _t3 , the rice will not burn, and the excess free water in the rice will not be blown away, resulting in dry rice.
In addition, from FIGS. 9 and 10 obtained through experiments to find the optimal value that does not cause uneven cooking, the microcomputer 12 determines the optimal power value and heating time of the low-heat power P _L corresponding to the time _t1. Select t ₃ .
Then, the microcomputer 12 calculates the heating time t ₃
After counting is completed and the operation of the low heat power _PL is completed, time _t4 is counted, and after this time count, the heater 3 is controlled to be energized to the steaming power P _B at time _t5 via the triax 11. When the heating time t ₅ is counted and the steaming power P _B operation is completed,
When the microcomputer 12 further counts the time _t6 , the entire rice cooking process is completed, and the completion is notified by a buzzer or the like. On the other hand, if the contact between the sensor 4 and the inner pot 2 is poor, the low heat power P
During _{the L} operation period, the temperature detected by the sensor 4 decreases without exceeding the rice-cooking completion temperature (for example, temperature Td), making accurate temperature measurement impossible. The temperature detected by sensor 4 is the reference temperature.
When it becomes less than Tc, low heat power P _L operates medium heat power P
A control program is stored in advance in the microcomputer 12 to return to _{the M} operation, and to return to the low heat power P _L again if the electric power exceeds Tc due to this operation. Therefore, its operation is as follows. That is,
When the microcomputer 12 detects the rice-cooking completion temperature, it enters into low-heat power P _L operation control for the heating time _t3 , but during that time _t3 it scans whether the temperature detected by the sensor 4 is above or below a certain reference temperature Tc. , the microcomputer 12 determines this based on the signal from the comparator 9, and controls the heater 3 to the low heat power P _L in the above case, or to the medium heat power P _M in the case below. Note that this reference temperature Tc can be selected from three types: the same temperature as the rice-cooking completion temperature, a higher temperature, and a lower temperature, but preferably, the microcomputer 12 can select an appropriate reference temperature Tc depending on the amount of rice to be cooked. It is better to select the desired amount of rice, and this will significantly improve the stability of rice cooking regardless of the amount of rice cooked. Also,
Of course, if the reference temperature Tc also serves as the rice-cooking completion temperature, there is an advantage that the cost of the control circuit can be reduced.

Furthermore, in the case of boiling water or continuous rice cooking, for example, when the rice cooking operation starts, the temperature of the inner pot 2 is higher than the operating point temperature Ta of the comparator 9, and the detected temperature of the sensor 4 is also higher than the temperature Ta. 9, but the heating time _t1 is measured in a short time, and this is inconvenient if the configuration is such that the parameters of various rice cooking patterns are automatically determined at this time _t1 . Therefore, the present invention further provides the following functions. That is, when the rice cooking on/off switch 6 is turned on to start rice cooking, and at the time of this start, the temperature detected by the sensor 4 is already higher than the operating point temperature Ta of the comparator 9 and lower than the next operating point temperature Tb. Almost at the same time as the rice cooking on/off switch 6 is turned on, the microcomputer 12 receives a signal from the comparator 9, and as a result, the microcomputer 12
is determined to be a rice cooking pattern that does not depend on the heating time _t1 for determining the amount of cooked rice, and a program suitable for this pattern is selected. That is, microcomputer 1
When the heater 2 detects the operating point temperature Tb, the heater 3 is operated with high heat power P _H for a preset heating time t ₂ , and thereafter is operated with medium heat power P _M until the rice cooking completion temperature Td is reached.

When the water in the cooked rice disappears and the rice reaches the cooking completion temperature Td, the microcomputer 12 receives the signal from the comparator 9, stops supplying the signal to the gate G of the trimmer 11, and stops energizing the heater 3. Further, after the microcomputer 12 counts the time _t7 , the rice cooking is completed and is notified by a buzzer or the like. Note that this rice cooking pattern does not need to be newly set, but may be configured to select an appropriate pattern from among the normal rice cooking patterns, and by taking such a countermeasure, hot water cooking and continuous rice cooking can be improved. It becomes possible.

Also, if the thermistor in sensor 4 is intermittent, the cooking time will be longer than the maximum rice cooking time under various conditions such as when the outside temperature is low, the water temperature is low, and the power supply is low. Since the sensor 4 cannot detect the initial operating point temperature Ta even after the elapse of time, the microcomputer 1
2 stops the signal supply to the gate G of the triac 11 and stops the operation of the heater 3.

On the other hand, in the case of cooking rice porridge, rice is input into the inner pot 2 in the same way as when cooking rice, and when the rice porridge cooking on/off switch 7 is turned on, the microcomputer 12
receives the porridge command and sends a signal to gate G of triax 11. As a result, the triax 11 is turned on, the heater 3 starts operating, and the inner pot 2 is heated with high flame electric power P _H as shown in FIG.

Then, when the temperature of the inner pot 2 rises and the temperature detected by the sensor 4 reaches the operating point temperature Ta of the comparator 9, the comparator 9 sends a signal to the microcomputer 12, and the microcomputer 12 starts counting the wave number of the commercial power supply 10. At the same time, the operating point of the comparator 9 is set to the temperature Tb. The temperature of the inner pot 2 further rises, and the temperature detected by the sensor 4 again reaches the operating point temperature of the comparator 9, as shown by the solid line in FIG.
When Tb is reached, the microcomputer 12 uses the signal from the comparator 9 to determine the heating time _t1 required for the sensor 4 to reach the operating point temperature Ta, Tb from the number of wave numbers counted, and determines the length of this time _t1 , that is, the control Depending on the amount of porridge, the heating time t ₂ from this point until the cooked rice in the inner pot 2 starts to boil as shown by the dashed line in FIG. 13 at point B is determined, and the heater 3 is controlled to high heat power P _H continue.

Then, when the microcomputer 12 determines the passage of time t ₂ using the timer function, the high flame power P _H
The control is stopped and switched to low-fire power P _L control with an energization rate corresponding to the heating time _t1 . This low-heat power P _L starts cooking at a constant simmering level with relatively low heat, and continues for an optimum heating time t ₈ corresponding to the heating time t ₁ , and when the microcomputer 12 finishes counting this time. , the rice porridge cooking is completed.

As explained above, according to the present invention, the cooking completion point of the rice in the inner pot is detected regardless of the amount of rice cooked, and after the rice cooking is completed, the rice is heated over low heat to perform uneven heating. Depending on the amount of rice cooked, it is possible to maintain the temperature of the cooked rice in the inner pot without lowering it, evaporate the free water remaining in the cooked rice in the inner pot, and supply enough heat to advance the gelatinization of starch in the rice. You can get the best rice cooking performance.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of an electric rice cooker according to the present invention, FIG. 2 is a front view of the operation panel of the same rice cooker, FIG. 3 is a control circuit diagram of the same rice cooker, and FIGS. Figure 5 is a rice cooking characteristic diagram, Figures 6 to 10 are characteristic diagrams of data stored in the microcomputer, Figure 11 is a rice cooking characteristic diagram when the sensor is difficult to install, and Figures 12 and 13 are each a rice cooking characteristic diagram. Each figure shows the characteristics of rice porridge. 1... Main body, 2... Inner pot, 3... Electric heater, 4... Sensor, 6... On/off switch for rice cooking, 9... Comparator, 11... Triax, 12... Microcomputer.

Claims (1)

[Scope of Claims] 1. An electric rice cooker that includes a container that stores rice and an electric heater that heats the rice through the container, including temperature detection means that detects the temperature of the container;
Obtaining a signal from the means to detect the temperature rise rate of the container, and switch the electric heater to low heat power for the uneven heating process from the rice cooking completion point determined based on the detected temperature rise rate. An electric rice cooker characterized by being provided with a control circuit for controlling the rice cooker. 2. The electric rice cooker according to claim 1, wherein the control circuit is configured to control the power value and heating time according to the temperature rise rate in low-heat power control of the electric heater.