JPH0444529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a rice cooker that automatically performs appropriate heating control according to rice cooking capacity.

BACKGROUND ART A conventional rice cooker, that is, a rice cooker that automatically performs appropriate heating control according to the rice cooking capacity, has a configuration as shown in FIG.

That is, the temperature of the inner pot 1 containing rice and water is detected by a temperature sensor 2 that is brought into contact with the outer peripheral side of the inner pot 1.
The temperature rise rate of the temperature sensor 2 is measured by the temperature rise rate measuring means 3. Different rice cooking capacities mean different heat capacities, so the temperature rise rate changes depending on the rice cooking capacity, and the temperature rise rate measuring means 3 outputs different outputs depending on the rice cooking capacity. Therefore, the rice cooking capacity is determined by the rice cooking capacity determining means 4 based on this output, and the rice cooking power is determined by the rice cooking power determining means 5 according to the rice cooking capacity. The power determined by the rice cooking power determining means 5 is used to control the power supply to the heating element 7 by the heating element energization control means 6, thereby performing appropriate heating control according to the rice cooking capacity.

Figure 6 shows the temporal changes in the temperature of the inner pot and the temperature of the temperature detector at this time, from time t ₁ when the temperature of temperature detector 2 reaches T ₁ °C to time T ₂ °C. The rice cooking capacity is determined based on the time difference (t ₂ - _{t 1 )} .

Problems to be Solved by the Invention In such conventional rice cookers, it has not been possible to accurately determine the rice cooking capacity. In other words, in a conventional rice cooker, as shown in the temperature rise curve in Figure 6, the temperature detected by the temperature sensor rises with a slight time constant behind the temperature of the inner pot, and the temperature increases inside the inner pot. When nucleate boiling begins, the rate of temperature rise in the temperature detector decreases, so it is not possible to make a large temperature difference between T ₁ and T ₂ , but the temperature in the temperature detector always increases at a constant temperature. (T ₂ − T ₁ )
The smaller the temperature difference, the larger the error in determining the amount of rice cooked.

Also, the reason why the heating is controlled by determining the amount of cooked rice is to keep the boiling time inside the inner pot constant regardless of the rice cooking capacity, but in this case, the degree of T ₂ must be lower than the boiling point. Therefore, there was a problem in that it was difficult to reliably find the boiling point.

An object of the present invention is to provide a rice cooker that solves these problems.

Means for Solving the Problems The present invention for solving the above problems includes, in addition to a first temperature detector that detects the temperature of the inner pot, a device that detects the steam pressure of the inner lid located at the upper part of the inner pot. A second temperature detector is provided to detect the temperature of the upper lid by rapidly increasing the temperature of the upper lid by passing steam when the temperature rises, and the temperature of the first temperature detector is set to a predetermined temperature. The rice cooking capacity is detected based on the elapsed time from when the second temperature sensor reaches a predetermined temperature.

Effect According to the above configuration, since the rice cooking capacity end temperature can be brought to the boiling point, the detection temperature range can be increased, and as a result, the error in determining the rice cooking capacity can be reduced, and the boiling point can also be brought to the boiling point. It can be detected reliably.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the accompanying drawings. FIG. 1 shows a block diagram of a rice cooker according to an embodiment of the present invention. Reference numeral 11 denotes an inner pot containing rice and water, and the inner pot 11 is heated at a constant amount by a heating element 12. When heated, the inner pot 11
The temperature inside the pot gradually rises, but the temperature inside the inner pot 11
Until the water inside boils, almost no steam comes up through the inner lid 13, which has only a small hole.
The temperature of No. 4 hardly rises. However, inner pot 1
When the water inside the inner lid 1 boils, a large amount of steam hits the upper lid 14 through a small hole in the inner lid 13, and the temperature of the upper lid 14 rises rapidly.

The rice cooking capacity is determined based on the temperature change at this time, and the temperature of the inner pot 11 is detected by the first temperature detector 15 provided so as to be in contact with the bottom of the inner pot 11. A first comparator 16 compares whether or not the first temperature detector 15 has reached a predetermined temperature or higher, and when the temperature has reached a predetermined temperature or higher, time measurement for determining the rice cooking capacity is started. Next, the second comparator 18 compares whether the temperature of the second temperature detector 17 provided on the upper lid 14 has exceeded a predetermined temperature, and when the temperature has exceeded the predetermined temperature, the time measurement ends. Then, the first comparator 16 starts outputting,
By measuring the elapsed time until the second comparator 18 starts outputting, the rice cooking capacity determining means 19 can detect the rice cooking capacity. This is because the elapsed time becomes longer as the heat capacity increases, so the rice cooking capacity can be determined based on this elapsed time. Based on the output of the rice cooking capacity determining means 19, the rice cooking power determining means 20
determines the rice cooking power according to the rice cooking capacity. According to the rice cooking power determined by the rice cooking power determining means 20, the heating element energization control means 21 is driven to control the heating amount of the heating element 13.

The temperature change over time at this time is shown in Figure 2.
As the temperature of the inner pot 11 rises, the temperatures of the first and second temperature detectors 15 and 17 rise as shown in FIG. The time (t) from the time ( _t3 ) when the temperature of the first temperature detector 15 reaches the predetermined temperature (T ₃ °C) until the second temperature detector 17 reaches the predetermined temperature ( _T4 °C) ₄ ), and the rice cooking capacity can be determined based on the elapsed time of ( _t4 - _t3 ). As the rice cooking capacity increases, (t ₄ −t ₃ ) becomes longer, and t ₄ becomes the time when the water inside the inner pot 11 boils.

FIG. 3 shows a specific circuit diagram of the present invention, which is composed of a microcomputer 30 and its peripheral circuits. Note that parts that are the same as those shown in FIG. 1 are given the same numbers, and their explanations will be omitted. The microcomputer shown here is
It is a so-called one-chip microcomputer consisting of a CPU, ROM, RAM, input/output ports, etc. The first comparator 16 compares whether the thermistor 15 that detects the temperature of the inner pot (the rice cooker body is not shown) has reached a predetermined temperature or not, and the thermistor 17 that detects the temperature of the upper lid has reached a predetermined temperature. The second comparator 18 compares whether or not the temperature has exceeded the temperature, and inputs the result to the microcomputer 30. Based on the time elapsed between these two temperatures, the cooking capacity is determined, and the amount of electricity applied to the heating element is determined. By driving the relay 21,
This constitutes a rice cooker that appropriately controls the amount of heat generated by the heater 12 according to the rice cooking capacity.

This operation will be explained based on the flowchart shown in FIG. In step 1, the relay 21 is driven by the microcomputer 30 to start the heating operation. Next, in step 2, a comparison is made to see if the temperature of the thermistor 15 has reached a predetermined temperature or higher, and this state is maintained until the predetermined temperature is reached.
When the temperature reaches a predetermined temperature or higher, time measurement for detecting the rice cooking capacity is started in step 3. In step 4, a comparison is made to see if the thermistor 17 has reached a predetermined temperature or higher. Then, when the temperature reaches a predetermined temperature or higher, in step 5, the time measurement started in step 3 is terminated. Step 6
Now, determine the rice cooking capacity based on this measured time,
In step 7, the heating amount is determined according to the rice cooking capacity, and by controlling the relay 21, the subsequent rice cooking operation is performed with an appropriate heating amount according to the rice cooking capacity.

Effects of the Invention As is clear from the above description, according to the present invention,
The temperature inside the inner pot gradually rises, but until the water in the inner pot boils, almost no steam rises through the inner lid, which has only a small hole, so the temperature rises at the top of the inner lid. The temperature of the upper lid, where it is located, hardly rises, but when the temperature inside the inner pot boils, a large amount of steam hits the upper lid through a small hole in the inner lid, so the temperature of the upper lid rises rapidly. A second temperature detector is attached, which improves the accuracy of rice cooking capacity determination, and has the extremely useful effect that the end point of rice cooking volume determination is the boiling point at which the rice cooking power should be appropriately controlled. It is.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a rice cooker showing an embodiment of the present invention, Fig. 2 is a temperature-time characteristic diagram of the rice cooker, Fig. 3 is a specific circuit diagram of the rice cooker, and Fig. 4 is the same. A flowchart showing the operation of the rice cooker, FIG. 5 is a block diagram of a conventional rice cooker, and FIG. 6 is a temperature-time characteristic diagram of the conventional rice cooker. 11... Inner pot, 12... Heating element, 13... Inner lid, 14... Upper lid, 15... First temperature detector,
16...First comparator, 17...Second temperature detector, 18...Second comparator, 19...Rice cooking capacity determining means, 20...Rice cooking power determining means, 21...Heating element energization Quantity control means, 30...microcomputer.

Claims (1)

[Claims] 1. An inner pot for storing rice and water, an upper lid provided on the top of the main body housing the inner pot and for taking out the inner pot from the main body, and a top lid provided between the upper lid and the inner pot, and an inner lid provided with a small hole for rapidly passing steam when the steam pressure from the inner pot increases; a heating element that heats the inner pot; and a heating element provided in contact with the bottom of the inner pot; and a first temperature detector for detecting the temperature of the inner pot; a first comparator for detecting when the first temperature detector has reached a predetermined temperature or higher; a second temperature detector for detecting boiling of water inside the pot; a second comparator for detecting when the second temperature detector has reached a predetermined temperature or higher; a rice cooking capacity determining means for determining the rice cooking capacity by measuring the elapsed time between the output of the comparator and the output of the second comparator; A rice cooker comprising: a rice cooking power determining means for determining the rice cooking power of the rice cooking power; and a heating element energization amount control means for controlling the amount of electricity supplied to the heating element based on a control signal from the rice cooking power determining means.