JPS62176411A - Control of 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] (b) Industrial application field The present invention relates to a method of controlling a rice cooker that is most suitable for a rice cooker.

(B) Conventional technology Conventionally, in cooking appliances that control temperature, the thermistor as a temperature sensor plays an important role.If this thermistor malfunctions, not only will the intended cooking not be possible, but the power will not always be supplied. This could lead to dangerous conditions such as a significant rise in temperature. As a method to solve such problems, as disclosed in Japanese Patent Publication No. 59-53049, a temperature detection circuit having a comparator for detecting the resistance value of the thermistor is provided with at least one standard corresponding to the normal detected temperature. There is a method in which a second standard corresponding to a temperature exceeding the normal detection temperature range is provided, and when the resistance value of the thermistor exceeds the second standard, a display different from the normal display is displayed. Therefore, in general cooking devices such as rice cookers, this second standard is used to distinguish between when the thermistor is open and the pot temperature when cooking in a cold place, and also to distinguish between when the thermistor is shorted and the temperature at which cooking ends. (approximately 140°C) To clearly distinguish between approximately -20°C and approximately 175°C
It is recommended to set it to . However, as is well known, the relationship between the temperature detected by the thermistor and the resistance value of the thermistor is not a linear relationship, so the above-mentioned Japanese Patent Publication No. 59-53049 describes the relationship between the potential and temperature at the connection point of the misc and the resistor. is a zo-like curve, and if the normal detection temperature range corresponds to a proportional range, it will be -20℃ and 175℃.
At least one of the 1 inch ranges corresponds to a range where there is no proportional relationship, making it impossible to accurately determine whether the thermistor is open or short-circuited, which may lead to the above-mentioned situation and malfunction. There was a risk.

(c) Problems to be Solved by the Invention The present invention takes the above-mentioned drawbacks into account and provides a method for controlling a cooking appliance that can accurately detect abnormalities.

(D) Means for Solving the Problems The present invention sets the voltage value based on the resistance value of the thermistor at two relative levels, and for example, at one level, the detected temperature of the thermistor = 175 The voltage value at one level corresponds to the range rIJIζ that has a proportional relationship around °C, and at the other level, the thermistor detection temperature knee around 20 °C corresponds to the range that has a proportional relationship. When controlling the heating means, if the temperature is outside the detected temperature range (for example, below 17°C), change to the other level and determine whether the temperature is above -20°C.
If the temperature is 20° C. or lower, the heating by the heating means is stopped and/or a different display than normal is displayed.

(e) Effect: According to the cooking appliance control method of the present invention, abnormalities in the thermistor can be accurately detected, there is no risk of dangerous situations such as a significant rise in the temperature of the cooking appliance, and there is no abnormality in the thermistor. This prevents malfunctions that would be determined to be abnormal.

(F) Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 8. Figure 1 is a sectional view of a rice cooker, in which (1) is an outer frame, (2) is a bottomed cylindrical container, and (3) is a hot plate type main body installed at the inner bottom of the container. The heater (4) is connected to the container (2).
) and placed on the heater (3), (5) is an auxiliary heater wrapped around the upper outer circumference of the container (2), and (6) is the pot (4). a negative characteristic thermistor (7) that detects the temperature of the pot (4) by contacting the outer bottom surface of the pot (4);
) is an operation panel provided on the outer surface of the outer frame 1), (
8) is a control board built into the operation panel.

As shown in Fig. 2, the operation panel (7) has an L button for rice cooking display.
ED<9), a heat retention display LED (10), a rice cooking switch (11), and a heat retention switch (12). Note that these switches are of automatic return type.

Figure 3 is an electrical circuit diagram of the rice cooker shown in Figure 1.
〉 is an AC power supply, (1) is a DC power supply circuit, (15) is a temperature detection circuit, and the thermistor (6), the resistor (16),
<17), capacitor (18) and first transistor (
19) and turn on the first transistor (19).
so that a parallel circuit of resistors (16) and (17) is formed, and the first transistor (19) is turned on and off.
The output voltage is made to differ depending on the
When the transistor (19) is ONI, the temperature detection circuit (15) is said to be in the L range, which is 0FFI.

When the temperature detection circuit (15) is in the H range), there is a considerable distance between the thermistor (6) and the control board (8), and this thermistor (
The lead wire 6) tends to pick up H sound, but this noise is absorbed by the capacitor (18).
(20) converts the output signal of the temperature detection circuit (15) into A/
8-bit A/D converter for D conversion, (21), (2
2) is the inverter for the driver of the rice cooking and heat keeping display LEDs (9) and (10), and (23) is the heater circuit, which includes the main heater (3), auxiliary heater (5), and relay contact (24). , a relay coil (25) of the relay contact,
It is composed of a second transistor (26) and a 5CR (27) that drive the relay coil, and when cooking rice, the relay contact (
24) is ON, SCR (27) is OFF and only the main heater (3) is energized, and during heat retention, the relay contact (24) is OFF, 5CR (27> is ONL, and the main heater (3) is energized.
The series circuit of the auxiliary heater (5) and the auxiliary heater (5) are energized. (28) is a control circuit, and the rice cooking/warming switch (1
1), (12) and the output data of the A/D converter (20), and based on that, the inverter (21)
), (22), first and second transistors (19), (2
6), and SCR (27).

FIG. 4 is a detailed circuit diagram of the control circuit (28).
29) is the initial circuit that outputs a pulse when the AC W source is turned on, (30) and <31> are R8-F-F that operates at the rising edge of the input signal, and (32) to (37) are the A/D conversion circuits mentioned above. Compare the output data of the device (20) with the comparison value built in each, and if it is greater than or equal to this comparison value, the output goes “H”.
A digital comparator that outputs a "L II level signal" if the level signal is less than 1. (38) is a one-shot circuit that outputs a pulse at the rising edge and falling edge of the input signal. (39) to (50) are AND The circuits, <51) to (55) are OR circuits, (56) and (
57) is a NOR circuit.

FIG. 5 is a characteristic diagram showing the relationship between the temperature detected by the thermistor (6) and the output data of the A/D converter when the temperature detection circuit <15) is set to the H range and L range. ) is in the H range, and (b) is on.

It's microwave time. Note that this characteristic diagram is based on the capacitor <1
8) and the A/D converter (20) with the leak current set to 0. In reality, the leakage of the capacitor (18) and the A/D converter (20) is ideal.
Due to the flow of leakage from the D converter (20), the characteristic diagram becomes slightly to the right. Moreover, FIG. 6 shows the respective comparators (3
2) to (37) “role 4, “comparison value” and temperature detected by the thermistor (6) corresponding to the r comparison value” are shown. In addition, in the control method of the present invention, as can be understood from FIGS. 5 and 6, in the H range, the thermistor (6
) temperature to judge short circuit: around 175"C corresponds to a range with a proportional relationship, and when in the L range, the temperature of the thermistor (6) to judge the oven, around 22 to 1, is a proportional relationship. In addition, the lower limit temperature for the H range: 17°C and the upper limit temperature for the L range: 120°C are set near the range where the proportional relationship changes from the range to the range where there is no proportional relationship.

Next, the operation of the above configuration will be explained based on FIGS. 1 to 6. First, put an appropriate amount of rice and water in a pot (4), store the pot (4) in a container (2), and turn on AC TItR (13). When the initial circuit (29) stops outputting pulses, the RS - F-F (30) and (31) are reset, and various circuits operate to carry out the warming process, but here, the rice cooking switch (11) is turned on immediately after the AC power supply (13) is turned on. ONl,.

The explanation will begin assuming that the rice cooking process is carried out using the following methods.

Turn on the rice cooking switch (11), R8-F-F (3
0) and (31) are fully set, and as a result, the AND circuit (
39) to <41), 49), and (50) become operational, and the first transistor (19) turns ON1.
, the temperature detection circuit (15) is set to the H range. Normally, the temperature of the pot (4) is initially low, and the comparator (33) outputs an "L" level signal, and the AND circuit (40) outputs a "L" level signal.
R3-F-F (30) will hold the set state, AND circuits (45) and (47) will output an H" level signal (assuming that the thermistor (6) is normal), and the second
Turn on the transistor (26) to energize only the main heater (3), and turn on the ED (9) for cooking rice. At this time, if the output data of the A/D converter (20) is less than 10H (the temperature detected by the thermistor (6) is less than 17°C), the comparator (34), 1: Since the “L” level signal can be output from the AND circuit (41), the RS-F・F (31) is reset. As a result, the temperature detection circuit (15) can be set to the L range, and ) to (44) become operational.However, since the temperature of m(4) is low, the comparator (35>).

(36> outputs a "Lo" level signal, and the output states of the ant 2 circuit (42) and (43>) do not change.The problem here is that the output state of the comparator (37>)
However, if the output data of the A/D converter (20) is
If the temperature detected by the thermistor (6) is less than 122°C, it is determined that the thermistor (6) is an oven, and the comparator (37) outputs an "H" level signal, and the AND circuit Since the “Ho” level signal is output from (44), the output of the NOR circuit (56) is “L”.
゛' [- Changed to the bell signal, AND circuit (45) to (
48) all output "I, I+ level signals. Therefore, the main and auxiliary heaters (3), (5) and the rice cooking and warming LEDs (9), (10) are not energized. In addition, the AND circuit (49) outputs the "L11 level signal" due to the "H" level signal of the AND circuit (44), and the output state of R3-F-F (31) does not change. The output data of the D converter (20) is OFH
If the above is the case (this applies when cooking rice in a cold region, or when cold water is poured into the pot (4)), use the AND circuit (4).
Since the output of 4) remains an “L” level signal, the OR circuit (
54〉 will give the pulse of the one-way circuit (38) to the A〉/AD circuit (49), and this AND circuit (4
The output of 9) changes from "H" to "L"-'H" level signal, and R3-FF (31) is set again. Here, the output of A/D converter (20) Output data is IOH
If it is less than that, the same operation as described above is repeated to determine whether the thermistor (6) is open.

Note that this operation is repeated until the pan (4) is heated by the main heater (3) and the temperature rises, and the temperature detected by the thermistor (6) reaches 17°C or higher. As a result, the temperature of the pot (4) rises and the thermistor (6) registers 17℃.
When this is detected, the temperature detection circuit (15) becomes stable in the H range, and the AND circuits (39) to (41) become stable in an operable state.Then, the temperature of the pot (4) further increases, When the thermistor (6) detects 135°C and the output data of the A/D converter (20) becomes BEH, the comparator (33) outputs an “H” level signal, and the AND circuit <40) outputs an “HII” level signal. Since the level signal is output, RS-F F(30) and (31) should be reset.
The AND circuits (45) and (47) will output the "L11 level signal. Therefore, the second transistor (
26) turns 0FFt, which turns off the relay contact 24), which turns off the cooking LED (9). In addition, the heat retention L E D<10> is turned on, the temperature detection circuit (15) is set to the L range, and the AND circuit (4
2) to (44) are ready for operation.However, immediately after the rice cooking is finished, the temperature of the pot (4) is still high and the comparator (36) outputs an "H" level signal, and the AND circuit (
43) is outputting a "HII level signal," the AND circuit (46) will output an "L" level signal, and 5CR (27) will be turned off and the main and auxiliary heaters (
3> Do not energize (5). In this state, the temperature gradually decreases, and the thermistor (6) detects less than 71°C and turns on the A/D.
When the output data of the converter (20) becomes less than C7H, the output of the comparator (36) changes to a "L" level signal, so the AND circuit (46) outputs a "HII level signal" and turns on 5CR (27). do. Therefore, energization to the series circuit of the main and auxiliary heaters (3) and (5) is started. The heating of these heaters (3) and (5) causes the temperature of the pot (4) to rise, and the thermistor (6) detects 71°C or higher and outputs the A/D converter (20). When the data becomes C7H or higher, the comparator (36) outputs an "H" level signal again, so the AND circuit (46)
outputs a “L” level signal and sets SCR (27) to 0F.
Cut off the power to the FL main and auxiliary heaters (3) and 5). Therefore, from now on, the main and auxiliary heaters (3),
(5) is repeated alternately to keep the temperature of the pot (4) at approximately 71°C.

In addition, during the above-mentioned heat retention process, if the temperature detected by the thermistor (6) rises for some reason and the output data of the A/D converter (20) exceeds FOH, the combination
5) outputs a “H” level signal, the AND circuit (
42) outputs the “HII level signal and R8-F F(
31) cents. As a result, the temperature detection circuit (15
), and the AND circuits (39) to <4
1) becomes operational. Therefore, since the comparator (34) outputs the H'' level (R9), the AND circuit (41) does not affect R8-F-F (31).
Also, since an L" level signal is given to one side of the AND circuit (5o), the change in the output signal of the humparator (33),
In other words, the change in the output signal of the AND circuit (4o) is RS −
F ・F (30), (31)+: No influence.

The problem here is the output state of the comparator (32), but if the A/D converter < 20) (7) output data is EoH or higher ('? - the detected temperature of Mister (5) is 17
5°C or higher), it is determined that the thermistor (6) is in a negative state, and the AND circuit (39) outputs “HII”.
Since the level signal is output, the output of the NOR circuit (56) changes to the "L11 level signal," and the AND circuit (45)
All of (48) output "L" level signals. Therefore, the main and auxiliary heaters (3) and (5) and the cooking ff12j
The heat-retaining LEDs (9) and (10) will not be energized. In addition, the NOR circuit (57) goes "L" and outputs a signal due to the "H" level signal of the AND circuit (39), and the output state of R3・-F-F (31) does not change. . Furthermore, when the output data of the A/D converter (20) is less than EOH, the output of the AND circuit (39) remains an "L" level signal, so the OR circuit (55) becomes a one-shot circuit (38). This pulse is given to the NOR circuit (57), and the output of this NOR circuit (57) is “H”.
"→"L"→"H" level signal changes, R5-F-F
(31) will be reset again. Here, A
If the output data of the /D converter (20) is equal to or higher than FOH, the same operation as described above is repeated to determine whether the thermistor (6) is short-circuited.

If the thermistor (6) opens during this warming process, the output data of the A/D converter (20) will become ○FH, so the output of the comparator (37) will become "L1".
1 level signal, and the output of the AND circuit (44) is “
The signal becomes “H” level, and the output of the NOR circuit (56) becomes “H” level.
” level signal. Therefore, the main and auxiliary heaters (3), (5) and the rice cooking and warming L E D (9
), (10) will not be energized.

FIG. 7 shows another embodiment in which the control circuit (28) in FIG. 3 is configured with a microcomputer, and (5B) is a CPU
, (59) is a ROM in which a program for instructing the operation of the CPU is written, (60) is a RAM for storing data,
(61) is the respective switch (11), (12> and A
An input port (62) is used to input the output signal of the /D converter <20>, and the input port (62) is connected to the respective transistors (19), (
26), SCR (27) and each inverter (21)
), (22). Note that the CPU (58) has a ROM (58).
By reading and executing the program sequentially from 9), input and output ports (61), (62)
Through this, connection with the outside is made and data is exchanged with the RAM (60).

FIG. 8 is a flowchart of the program written in the ROM (59). The operation based on this flowchart is almost the same as that of the circuit shown in Fig. 4, so a detailed explanation of the operation will be omitted here, but the only difference from the circuit shown in Fig. 4 is the temperature detection circuit. This operation is added because it takes about 1 second for the output signal of the temperature detection circuit (15) to reach a steady state due to charging and discharging of the capacitor (18) when changing the range of (15). ing.

In the present invention, the rice cooking process is performed when the temperature detection circuit is set to the H range, and the warming process is performed when the temperature detection circuit is set to the L range.
) to change the rice-cooking end temperature or heat-retaining temperature, so that only the rice-cooking end temperature or the heat-retaining temperature can be changed.

That is, for example, when the rice cooking process and the warming process are performed only in the H range, changing the rice cooking end temperature always changes the warming temperature, so this is to prevent this.

In addition, in the present invention, when the temperature detection circuit is set to HL-'/', the lower limit temperature of the normal detection temperature range is set to 17°C (
The upper limit of the normal detection temperature range when set to the L range is set to 120°C (thermistor detection temperature), but it is not limited to this value, and the thermistor in each range Detected temperature and A/
In the characteristic diagram of the D data, it is sufficient to set it near the boundary where a portion that is in a proportional relationship changes to a portion that is not.

Furthermore, in the present invention, when the thermistor is short-circuited or open, the LED for cooking rice and keeping warm is turned off (
(When the power is turned on, if the thermistor is normal, one of the LEDs will always be on.) It is also possible to install a display device to notify of an abnormality and notify the thermistor of a short circuit or an oven. Of course.

(G) Effects of the Invention The present invention can accurately detect an abnormality in a thermistor, eliminates the risk of causing a dangerous situation such as a significant rise in the temperature of the cooker, and detects an abnormality even when the thermistor is not abnormal. It is possible to provide a method for controlling a cooking appliance that can prevent malfunctions such as those caused by the determination.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a rice cooker according to the control method of the present invention, FIG. 2 is a front view of the operation panel in FIG. 1, and FIG. The figure shows the third
5 is a detailed circuit diagram of the control circuit in FIG. 3. FIG. 5 is a characteristic diagram of the temperature detected by the thermistor in FIG. Fig. 7 is a circuit diagram in which the control circuit in Fig. 3 is composed of a microphone 1 + a computer, and Fig. 8 (a) and Fig. 8 (b) are the ROM in Fig. 7.
This is a flowchart of a program written in . <3) Main heater, (4) Pot, (5) Auxiliary heater, (6) Thermistor, (9) Rice cooking LED, (10) Heat retention LED for (15)・
・・Temperature detection circuit, (20) ・・A/D converter, (2
8)...Control circuit.

Claims (1)

[Claims] (1) The resistance value change of the thermistor that detects the temperature of the heated object is extracted as a voltage change, the temperature of the heated object is detected based on this voltage value, and the heating amount of the heating means that heats the heated object is controlled. In the cooking device control method, when the detected temperature exceeds the normal detected temperature range, the relative level of the voltage value is changed to determine whether the temperature is within the abnormal temperature range, and the temperature is determined to be within the abnormal temperature range. A method for controlling a cooking appliance, characterized in that at certain times, heating by a heating means is stopped and/or a display different from a normal display is displayed.