JPS6323769B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a rice cooker.

Traditionally, rice cookers have been developed that can automatically cook rice by adding the desired amount of rice and water according to the amount of rice to the rice cooker and pressing the rice cooker switch, which heats the rice using electricity or gas. ing. Recently, microcomputers (hereinafter referred to as ``microcomputers'') are used to control rice cookers.
), a rice cooker has been proposed that allows for more precise control of the rice cooker and improves safety.

1 to 3 are diagrams showing the configuration of a microcomputer-controlled rice cooker (hereinafter referred to as "microcomputer rice cooker") according to the present invention developed and proposed by the present inventors. FIG. 2 is a block diagram showing the system configuration of the rice cooker, FIG. 2 is a cross-sectional view of the main part of the microcomputer rice cooker, and FIG. 3 is a diagram showing the configuration of a temperature sensor circuit for detecting the cooking temperature.

In Figures 1 to 3, 1 is the inner pot 2 of the rice cooker.
It is a lateral temperature sensor that detects the temperature on the side of 1.
It measures the internal temperature of the inner pot of a rice cooker. 2
is a center temperature sensor for detecting rice cooking temperature, which is installed at the center of the inner bottom of the rice cooker, and measures the temperature near the bottom of the pan to detect the end of rice cooking. Details of this temperature sensor will be explained later with reference to FIG. A safety temperature sensor 3 is attached to a microcomputer board 22 disposed on the outer bottom of the rice cooker with a gap in between, and is used to protect electronic components constituting the microcomputer from malfunction or damage due to abnormal temperatures. 4 is a power outage memory circuit provided in the microcomputer board 22 for storing the rice cooking state immediately before the power outage (in the middle of cooking or in the process of keeping warm) when a power outage occurs during rice cooking. 5 is an inner pot detection sensor provided on the side of the rice cooker, and when the inner pot 21 is set, the lever 5a moves from the broken line position to the solid line position as shown in the figure, indicating whether the inner pot is set or not. This is to detect whether or not this is the case. Permanent magnet 5b as sensor
A combination of a reed switch 5c and a reed switch 5c sensitive to the magnet is suitable. 6 is a rice cooking switch, 7 is a deep cooking switch, 8 is an abnormal temperature detection circuit attached to a microcomputer board, 9 is a microcomputer, 10 is a rice cooking display section that indicates that a series of rice cooking processes are in operation, 11 is a heat retention display section that indicates that the heat retention operation is in progress. Reference numeral 12 is a buzzer that notifies the end of rice cooking, etc., and 13 is a heating circuit that constitutes a rice cooking section and a heat retention section. 14 is a power supply circuit, and 15 is a heater drive signal.

FIG. 3 is an example of a temperature sensor suitable for a center temperature sensor or the like. In the figure, Rs is an element such as a thermistor whose resistance value changes with temperature as shown in Fig. 4, and is used as a temperature sensing element. This is used, for example, by being incorporated into the center temperature sensor 2, as shown in cross-section in FIG. Thermistor Rs
is connected in series with the resistor _R1 to the reference voltage Vcc, and the voltage Vb at this connection point is applied to the "-" terminal of the comparator C. with temperature
Since the resistance value of Rs changes as shown in FIG. 4, this voltage Vb changes with temperature as shown by the curve Vb in FIG. 10. The "+" terminal of comparator C has
A constant voltage Va obtained by dividing the power supply voltage Vcc by resistors R ₂ and R ₃ is applied.

In Figure 3, when the temperature rises and the voltage Vb rises and exceeds a certain voltage Va, the comparator C
detects this and outputs a temperature detection signal to the microcomputer 9.

Now, put the required amount of rice and water in the inner pot 21, set it in the rice cooker, turn on the power switch, and turn on the rice cooking switch.The rice cooking display 10 will light up and the program built into the microcomputer 9 will start. Therefore, rice cooking is started. During the rice cooking operation, each sensor monitors the rice cooking temperature, microcomputer board temperature, etc., and when the rice cooking is finished, the center temperature sensor 2 detects this and switches from the rice cooking heater to the warming heater. When a fault such as a breakdown occurs and the temperature rises abnormally, the safety temperature sensor 3, abnormal temperature detection circuit 8, etc. are activated immediately to turn off the power, thereby preventing an accident from occurring.

These rice cookers allow detailed control over rice cooking, heat retention, safety, etc., and can always safely cook delicious rice without failure, but the rice cooker only operates at a predetermined temperature when the rice cooker finishes cooking. Since the temperature is detected by the center temperature sensor 2, it is not possible to adjust the cooking temperature and it is not possible to make rice according to the user's preference. For example, some people like browned, fragrant rice, while others throw away browned rice, and others may need more fragrant rice for that day's dishes, or they may need rice that is not browned. However, I was unable to respond to such a desire.

An object of the present invention is to provide a rice cooker that eliminates such drawbacks and allows the user of the rice cooker to prepare rice according to his/her preference.

The present invention has been made to achieve the above object, and its feature is that the operating temperature (rice cooking end temperature) of a center temperature sensor for detecting the end of rice cooking can be adjusted.

The present invention will be described below with reference to embodiments shown in FIGS. 6 to 9. Note that in FIGS. 6 to 9, the same components as those in the embodiment described in FIG. 3 are given the same symbols, and since they have similar effects, their explanation will be omitted.

In the present invention, the reference voltage Va to the "+" terminal of the comparator C in FIG. 3 is fixed to a constant voltage,
In order to make the bias voltage of the input voltage Vb to the "-" terminal variable, a variable resistor Rx (a manual voltage regulator for adjusting the cooking temperature) is inserted on the "-" terminal side of the comparator C. As shown in Fig. 5, the thermistor Rs, which is a temperature sensing element, is incorporated into the center temperature sensor so that the temperature of the inner pot near the heater can be detected when the rice cooker is in use. Specific examples in which the variable resistor Rx is inserted are shown in FIGS. 6 to 9.

6 to 9, the input voltage Vb to the comparator C is the voltage obtained by dividing the power supply voltage Vcc by the resistance of the thermistor Rs, the resistor _R1 , and the variable resistor Rx, and the respective divided voltages are Vs , V ₁ , and Vx, the voltages V ₁ and Vx become bias voltages of the voltage Vb. Here, the variable resistor Rx is adjusted so that the rice cooking end temperature a is reached when the voltage Vb becomes equal to or higher than the reference voltage Va. Cook rice in this state.
As the rice cooking approaches the end stage, the temperature of the inner pot increases, and the temperature of the thermistor Rs in the center temperature sensor 2 increases accordingly. This voltage Vb
However, as shown in FIG. 10, when the rice cooking temperature reaches a, the voltage Vb becomes equal to the reference voltage Va, and the comparator C outputs a temperature a detection signal to the microcomputer 9. Immediately upon receiving this, the microcomputer 9 turns off the rice cooking heater.

When cooking browned rice, for example,
In the case of the embodiment shown in the figure, the variable resistor Rx is adjusted to reduce the bias voltage of the input voltage Vb to the comparator C by △Vx (curve Vb ₁ ) as shown in Fig. 10, and the cooking temperature is changed from a to a. You can move it to ₁ . In the case of the embodiments shown in FIGS. 7 to 9, the desired rice is cooked in the same manner.

In this way, according to the rice cooker of the present invention, it is possible to very easily cook rice to your liking just by adjusting the variable resistor.

Note that although the above explanation has been made using a rice cooker that uses a microcomputer as an example, it goes without saying that the present invention can also be used for a normal rice cooker, and the present invention is not limited to a rice cooker that uses a microcomputer.

Furthermore, it goes without saying that the circuit configuration of the present invention is not limited to that of the embodiment described above, and may be modified without changing the gist of the present invention.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the system configuration of a rice cooker using a microcomputer, Figure 2 is a sectional view of the main parts of the rice cooker using a microcomputer, and Figure 3 is an example of the temperature detection circuit shown in Figure 1. 4 shows the temperature characteristics of the thermistor, FIG. 5 shows the mounting position of the center temperature sensor, and FIGS. 6 to 9 show the configuration of the temperature detection circuit according to the embodiment of the present invention. FIG. 10 is a diagram for explaining the operation of the temperature detection circuit of this embodiment. Rs...Thermistor, _R1 , _R2 , _R3 , _R4 ...Resistor,
Rx...variable resistance, C...comparator.

Claims (1)

[Claims] 1. A temperature-sensing element that detects the temperature of the inner pot by contacting the inner pot, a means for converting resistance changes of the temperature-sensing element into voltage changes, and a manual voltage regulator for adjusting cooking to taste connected to the converting means. and a reference voltage source, and a comparator that compares the reference voltage set by the reference power source with a voltage based on the temperature change from the temperature sensing element and the output of the manual voltage regulator for adjusting the cooking temperature. A rice cooker featuring: