JPS59141910A - Rice cooker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to disconnection detection of a temperature sensing element that constitutes temperature detection of the inner pot in a rice cooker having a rice cooking heating control device that detects the temperature of the inner pot and controls the rice cooking heater. It is something.

In conventional thermosensor disconnection detection, a voltage dividing resistor circuit including the thermosensor is used in common to detect the temperature of the inner pot, and the disconnection detection level is set to an extremely large resistance value corresponding to a disconnection of the thermosensor. I set it to . However, according to the conventional method, there is too much difference in the set resistance value of the temperature sensing element for detecting the temperature of the inner pot and detecting disconnection. Since the temperature detection level is adjusted to the temperature detection level of the pot, there is a drawback that there is a risk of erroneously detecting a disconnection.

Particularly in cold regions, where the ambient temperature is low, if a negative thermistor is used as a temperature sensing element, its resistance value will increase, making this method unreasonable.

The present invention has been made in view of the above points, and detects the disconnection of the temperature sensing element that constitutes the temperature detection sound of the inner pot. Even if a voltage divider resistor circuit is used for both inner pot temperature detection and wire breakage detection,
The set resistance value of the temperature sensing element for detecting disconnection can be made small, and detection can be performed at a stable level of the voltage dividing resistor circuit, thereby solving the above-mentioned drawbacks of the conventional technology.

An embodiment of the present invention will be described below.

FIG. 1 is an overall configuration diagram of an embodiment of a rice cooker according to the present invention.

As is clear from FIG. 1, a temperature detection I#5, which also includes a rice cooking heater 3 for heating the inner pot 2 and a temperature sensing element 4 for detecting the temperature of the inner pot 2, is installed between the outer pot 1 and the inner pot 2. After a certain period of time has elapsed after the start of rice cooking by the rice cooking time measuring means 6, the disconnection determining means 7 compares and determines the detection level detected by the temperature detection I#5 with the disconnection level, and the result is used by the rice cooking heating control means. 8 to control the rice cooking heater 3.

FIG. 2 is a sectional view of the rice cooking bodies used in the embodiment of FIG. 1.

In the figure, 1 is an outer pot, and an inner pot 2 containing rice and water is placed inside the outer pot. 3 is a rice cooking heater placed between the inner pot 2 and the outer pot 1, and the temperature detection N is closely attached to the bottom of the inner pot 2.
It is controlled by the temperature sensing element 4 which constitutes 5. The temperature sensing element 4 is composed of a negative thermistor.

Figure 3 is a circuit diagram showing electrical connections, 16 is A/D conversion @
11, a microcomputer with a built-in memory 12, a CPU 13, an input circuit 14, and an output circuit 15; 24, a resistor 9;
and temperature sensing element 4 form a voltage dividing resistor circuit.

The rice cooking heating control means 8 includes the microcomputer 16,
It is composed of a resistor 19, a transistor 20, a resistor 21, a bidirectional thyristor 22, and a rice cooking heater 3.

17 is an A/
This is the input terminal of the D conversion@11, and the A/D converter is used to convert the analog voltage potential from the voltage dividing resistor circuit 24 into a digital value.
input to converter 11; Similarly, reference numeral 18 indicates an output terminal of the output circuit 15.

10 is a rice cooking switch for starting rice cooking, and 23 is a commercial frequency power supply.

Next, the operation of the above embodiment will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a diagram showing the relationship between the temperature at the bottom of the inner pot 2 and time after starting rice cooking. Time T9 is set in advance in the memory 12 of the microcomputer 16, and
After a period of time has elapsed, the temperature of the temperature sensing element 4 closely disposed at the bottom of the inner pot 2 is detected to determine whether the wire is disconnected.

If the temperature sensing element 4 is disconnected, it is naturally impossible to detect that the temperature has increased to r at time t)TpWk, so it can be determined that the temperature sensor 4 is disconnected.

FIG. 5 is a flowchart showing a disconnection detection program stored in the memory 12 of the microcomputer 16.

First, when the rice cooking switch 10 is pressed 1, the rice cooking beater 3 is turned on by steps 25 and 26 to start cooking rice.

Output terminal 1 of microcomputer 16
8 becomes High, the transistor 20 turns on through the C resistor 19, the gate current of the bidirectional thyristor 22 flows through the resistor 21, and the bidirectional thyristor 22 is turned on.
and turn on the rice cooking heater 3.

When the time Tb has elapsed since the start of rice cooking in step 27, the process proceeds to step 28, and a disconnection of the temperature sensing element 4 of the temperature detection @s5 is detected.

The detection level VD measured at the input terminal 17 of the A/D converter l#11 is expressed by the following equation.

In R+Rr, R2 is the resistance value of the resistor 9 and the thirst sensing element 4, and Vss is the power supply voltage of the control circuit.

In addition, the disconnection level is the resistance of the temperature sensing element 4 when the temperature of the temperature sensing element 4 reaches the temperature rise value t when the temperature sensing element 4 is normal after one hour has passed from the start of rice cooking. Value RTI-I
is a value calculated using the formula (fa), and is stored in advance in the memory 12 of the microcomputer 16.

Therefore, ■ is a value expressed by the following equation.

R0Rn1 Therefore, in the case of vj)Ve, it is determined that the wire is broken and step 2
Proceed to 9.30 and turn off rice cooking heater 3 in step 29.
Turn to F and stop cooking.

In this process, the output terminal 18 of the microcomputer 16 is turned OFF, turning off the transistor 20, cutting off the gate current of the bidirectional thyristor 22, turning the bidirectional thyristor 22 OFF, and setting the rice cooking heater 3 to QFF.

Further, in step 30, for safety, all functions of the device are disabled, for example, if the rice cooking indicator lamp is on, it is turned off, etc., to notify the user of any abnormality.

■ If <), it is determined that the temperature sensing element 4 is normal and the process proceeds to step 31, and when determining whether the temperature of the temperature sensing element 4 has reached the completion level ■ when rice cooking is completed. Similarly, the determination is made by comparing with the detection level vs' measured at the input terminal 17 of the A/D converter 110.

In the case of Vs'>vs, the determination in step 31 is made again, and in the case of W(V3), it is determined that the rice cooking is completed and the rice cooking heater 3 is turned off.

As described above, according to the present invention, the temperature rise value of the temperature sensing element is detected after a certain period of time has passed after the start of cooking to detect the disconnection of the temperature sensing element that constitutes the temperature detection of the inner pot. Since the determination is made, it is possible to reduce the set resistance value of the thermosensing element when detecting a disconnection, and by detecting at a stable level of the voltage dividing resistor circuit, it is possible to reliably detect a disconnection of the thermosensor, and at the same time, it is possible to It is also possible to reliably detect the temperature upon completion.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of an embodiment of the rice cooking example according to the present invention, Fig. 2 is a sectional view of the rice cooking cylinder main body, Fig. 3 is a circuit diagram showing its electrical connection, and Fig. 4 is a diagram after the rice cooking starts. A diagram showing the relationship between the temperature of the temperature sensing element and time, FIG. 5 is an o-chart showing the operation of this embodiment. In the figure, 2 is an inner pot, 3 is a rice cooking heater, 4 is a temperature sensing element, 5 is a temperature detection sensor, 6 is a rice cooking time measuring means, 7 is a disconnection determining means, and 8 is a rice cooking heating control means. Agent Shu Shin - (1 other person) Fang 1 Figure 2 JP-A-59-141910 (4) Figure 4 Figure 5 Start No.! 25 1 □-7°N26 No 27 28 Vb>V. No-Or-F-29 o31 YES

Claims (1)

[Claims] In the rice cooker, the rice cooker includes a rice cooking heater that heats an inner pot, a moisture detector that detects the temperature of the inner pot, and a rice cooking heating control means that controls the rice cooking heater based on a detection signal from the temperature detection plate. A rice cooker characterized in that disconnection of a temperature sensing element constituting the rice cooker is detected by detecting a temperature rise value of the temperature sensing element after a certain period of time has elapsed after the start of rice cooking.