JP3006597B1 - Electric rice cooker temperature detector - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To improve accuracy of rice cooker temperature detection of a microcomputer-controlled electric rice cooker. A microcomputer control unit reads a detected value of a rice cooker temperature from a rice cooker temperature detector and controls a heating amount of the heating unit at the time of cooking or maintaining the temperature. When the rice cooker temperature detection value detected by the means is in an abnormal temperature state that is equal to or higher than a predetermined value, the abnormal temperature determination circuit determines that the apparatus is in an abnormal temperature state, and stops the heating operation of the heating means at the time of cooking or maintaining the temperature. In the electric rice cooker, the temperature range of the rice cooker temperature detection value detected by the rice cooker temperature detection unit without using the microcomputer control unit is determined, and the detection resistance value of the rice cooker temperature detection unit is determined. Is provided with a detection resistance value switching means for switching the values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rice cooker temperature detecting device for an electric rice cooker.

[0002]

2. Description of the Related Art In general, a sensor holder portion below a rice cooker (inner pot) of an electric rice cooker is provided with a rice cooker temperature detecting means such as a thermistor together with a temperature fuse. The temperature of the cooker is detected, and the microcomputer control unit controls the amount of heating of the cooker heating means such as a heater and a work coil based on the detected temperature. , The heating operation of the rice cooker heating means is stopped. However, in such a configuration, there is an inconvenience that the thermal fuse must be replaced once it has been blown (first conventional example).

Therefore, recently, as described above, the temperature of the rice cooker is detected by the rice cooker temperature detector such as a thermistor, and the heating amount of the heater such as a heater or a work coil is controlled by the microcomputer control unit based on the detected temperature. On the other hand, an abnormal temperature determination circuit including a comparator is provided separately from the microcomputer control unit, and the temperature detection value of the rice cooker temperature detection unit is compared with a predetermined reference temperature value. When the temperature exceeds a predetermined reference temperature value, it is determined that the temperature is abnormal and the supply of power to the rice cooker heating means is stopped to suppress the rise in the rice cooker temperature,
A device designed to protect the device has been proposed (second conventional example).

[0004]

By the way, in recent electric rice cookers, it is necessary to control the amount of heating in a high temperature region considerably as compared with ordinary electric rice cookers, for example, an electric rice cooker having a brown rice cooking menu. The above-mentioned rice cooker temperature detecting device is also required to have high detection accuracy in a wide temperature range including temperature detection in this region and an abnormal temperature region.

However, in general, the temperature detecting means such as the thermistor has a temperature detecting characteristic as shown in FIG. 4A, for example. The resolution (number of bits) of the temperature detected by the microcomputer control unit tends to decrease, and the reading accuracy tends to decrease.

Therefore, in order to solve such a problem and improve the accuracy of reading the temperature of the rice cooker especially in a high temperature region, for example, a rice cooker temperature detection which does not have an abnormal temperature determination circuit as in the above-mentioned first conventional example. for devices, for example, as shown in FIG. 10, the rice device temperature detection circuit consisting of voltage dividing resistors R _1, which is a thermistor T and detection resistor is a high resistance to the ground side voltage dividing resistors R ₁ (R ₁ = 51k ) while arranging, and setting corresponding to a high temperature region by a structure of arranging the thermistor T to the power supply, for example, a low resistance when cold zone R ₂
(R ₂ = 4.7 kΩ) and low resistance R ₃ (R ₃
= By reading inserted in parallel a plurality of resistors R _2, R ₃ with respect to the voltage dividing resistors R ₁ of 9.1kΩ), configured to increase the reading accuracy of the rice device temperature is employed in the high temperature region .

However, as in the second conventional example, the temperature detection voltage of the thermistor T is compared with reference voltages set by comparison reference voltage setting resistors R ₃ and R ₄ for judging abnormal temperatures. In the case where the rice cooker is provided with an abnormal temperature determination circuit that activates the heating stop circuit Rs when it is determined that the detected rice cooker temperature is in an abnormal temperature state, for example, FIG.
As shown in ( ₁ ), from the viewpoint of preventing malfunction due to microcomputer runaway, the detection resistance value of the rice cooker temperature detection circuit (resistances R ₁ , R ₂ , thermistor T) is switched by port control of the microcomputer control unit 100. Absent. Therefore, switching of the rice cooker temperature detection region as in the first conventional example of FIG. 10 cannot be performed, and a problem arises in that the accuracy of reading the rice cooker temperature in a high temperature region is reduced.

In FIG. 11, the voltage dividing resistor is divided into two parts, R ₁ and R ₂ , and a diode D ₀ is inserted between them and the output terminal of the comparator C _1. R
This is to provide a hysteresis characteristic during the s operation and prevent hunting of the reset operation. The resistor R ₅ is an operation voltage supply resistor to the heating stop circuit Rs.

The invention of this application has been made to solve such a problem, and a temperature region is determined or a power supply voltage signal is detected, and the determined temperature region or the detected power supply voltage signal is detected. In order to improve the accuracy of reading the rice cooker temperature by the microcomputer control unit by switching the rice cooker temperature detection characteristic by switching the detection resistance value of the rice cooker temperature detection means without going through the microcomputer control unit according to It is an object of the present invention to provide an improved electric rice cooker.

[0010]

Means for Solving the Problems Claims 1 to 6 of this application
SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems, and is provided with the following means for solving the problems.

(1) The invention of claim 1 That is, first, the rice cooker temperature detecting device of the electric rice cooker according to the invention of claim 1 of the present application uses the microcomputer control unit to convert the detected rice cooker temperature value from the rice cooker temperature detecting means. In addition to controlling the heating amount of the heating means at the time of cooking or keeping the temperature while cooking, and having an abnormal temperature determination circuit, the detected temperature of the rice cooker temperature detected by the above-described rice cooker temperature detector is an abnormal temperature state that is equal to or higher than a predetermined value. Sometimes, the abnormal temperature determination circuit determines that an abnormal temperature is present, and stops the heating operation of the heating means at the time of the rice cooking or keeping the temperature in the electric rice cooker. A detection resistance value switching unit configured to determine a temperature range of the rice cooker temperature detection value detected by the rice cooker temperature detection unit and to switch a detection resistance value of the rice cooker temperature detection unit. There.

Therefore, the detection resistance value of the rice cooker temperature detecting means can be switched without the intervention of the microcomputer control unit in accordance with the temperature range of the detected rice cooker temperature value detected by the rice cooker temperature detecting means. Regardless of the presence or absence of the circuit, the accuracy of reading the temperature of the rice cooker by the microcomputer control unit can be improved.

(2) The invention of claim 2 is a rice cooker temperature detecting device for an electric rice cooker according to the present invention, wherein the detection resistance switching means is detected by the cooker temperature detecting means. The detected rice cooker temperature is compared with a predetermined reference temperature that separates the low temperature region and the high temperature region, and the detected rice cooker temperature detected by the rice cooker temperature detector separates the low temperature region and the high temperature region. It is characterized in that the detection resistance value of the rice cooker temperature detection means is switched when the temperature is in a high temperature region higher than a predetermined reference temperature.

Therefore, when the detected value of the rice cooker temperature detected by the rice cooker temperature detector is in the high temperature region above the above-mentioned predetermined reference temperature, the rice cooker temperature detector does not need to go through the microcomputer control unit as described above. Is switched, and the reading accuracy of the rice cooker temperature of the microcomputer control unit is improved.

(3) A third aspect of the present invention is a rice cooker temperature detecting device for an electric rice cooker, which reads a detected rice cooker temperature value from a rice cooker temperature detecting means into a microcomputer control unit and heats the rice cooker or keeps the rice cooker warm. Means for controlling the amount of heating of the means and an abnormal temperature determination circuit, and when the detected temperature of the rice cooker temperature detected by the rice cooker temperature detection means is in an abnormal temperature state equal to or higher than a predetermined value, the abnormal temperature determination circuit In the electric rice cooker configured to determine the state and stop the heating operation of the heating means at the time of the rice cooking or the heat retention, a power supply voltage signal is detected, and the microcomputer is configured based on the detected power supply voltage signal. A detection resistance switching means for switching the detection resistance of the rice cooker temperature detection means without using a control unit is provided.

Accordingly, the power supply voltage signal is detected, and the detection resistance value of the rice cooker temperature detecting means is switched based on the detected power supply voltage signal, so that the microcomputer control unit can read the rice cooker temperature with higher accuracy.

(4) A fourth aspect of the present invention is a rice cooker temperature detecting device for an electric rice cooker according to the third aspect of the present invention, wherein the detecting resistance value switching means sets a zero cross timing of a power supply voltage signal. It is characterized in that the detection resistance value of the rice cooker temperature detection means is switched at the zero cross timing of the power supply voltage signal.

Therefore, the detection resistance value of the rice cooker temperature detecting means is switched in accordance with the detected zero-cross timing of the power supply voltage signal, thereby improving the accuracy of reading the rice cooker temperature by the microcomputer control unit.

(5) The invention of claim 5 is a rice cooker temperature detecting device for an electric rice cooker according to the invention of claim 1, 2, 3 or 4 wherein the detection resistance switching means is hardware. It is characterized by being constituted by a circuit.

Therefore, the circuit can be easily formed independently of the microcomputer control unit.

(6) The invention of claim 6 is a rice cooker temperature detecting device for an electric rice cooker according to the invention of claim 3, 4 or 5, wherein the heating means comprises an electromagnetic induction heating means, The abnormal temperature determination circuit is characterized in that it operates at the zero cross timing of the power supply voltage signal.

Therefore, even in the case of an electric rice cooker provided with electromagnetic induction heating means that generates electromagnetic induction noise when driven,
Since the abnormal temperature determination circuit is operated at the zero-cross timing of the power supply voltage signal having low electromagnetic induction noise of the electromagnetic induction heating means, malfunction of the abnormal temperature determination circuit due to the influence of the electromagnetic induction noise is prevented.

[0023]

(Embodiment 1) The configuration and operation of a rice cooker temperature detecting device for an electric rice cooker according to Embodiment 1 of the present invention will be described below with reference to FIGS. .

First, FIG. 1 shows a structure of a rice cooker main body of the electric rice cooker when an electric heater is employed as a heating means, for example.

This electric rice cooker is, for example, a so-called rice cooker-type one that serves both rice cooking and heat retention. A container body comprising a bottomed cylindrical outer case 1 configured so that a rice cooker (inner pot) 3 can be set therein, and a lid unit 2 for covering the upper part of the outer case 1 is provided. It is configured.

The outer case 1 is composed of a bottomed cylindrical cover member 4 made of, for example, a synthetic resin, and a shoulder member 5 made of the same synthetic resin and integrated with the upper end of the cover member 4. In addition, a bottomed cylindrical inner case 6 for removably setting the rice cooker 3 is provided therein.

The inner case 6, for example made of a bottomed cylindrical metal plate, the upper side outer peripheral edge portion 6a against the lower surface of the peripheral portion 5a inner having a shoulder heater H ₃ of the shoulder member 5 coupled, heat retaining heater (sub-heater) H ₂ is provided on the outer circumferential surface vertically substantially central portion of the side wall 6b. Also,
At the center of the bottom wall 6c of the inner case 6, there is provided a center sensor 7 which is in contact with the center of the lower surface of the bottom 3a of the rice cooker 3.
Is provided.

The center sensor 7 is located at the bottom 3 of the rice cooker 3.
It functions as a rice cooker temperature detecting means for detecting the temperature of a and a rice cooker set detecting means for detecting the presence or absence of the rice cooker 3, and detects the thermistor T as the rice cooker temperature detecting means and the presence or absence of the rice cooker 3. A well-known sensor structure in which a reed switch (not shown) serving as a rice cooker set detecting means is housed is employed.

Further, the upper side of the bottom wall 6c of the inner casing 6, provided with a cooking heater (main heater) H ₁ as rice vessel heating means so as to surround the thermistor T portion of the center sensor 7 A heater plate 9 made of casting is provided. The heater plate 9 is tightly adhered from the lower surface of the bottom portion 3a of the rice cooker 3 set in the inner case 6 to the side surface without any gap, and the heat transfer property of the bottom 3a of the rice cooker 3 and the side surface thereof is good. It is designed to heat evenly.

On the other hand, the lid unit 2 has an outer cover member 10 made of a synthetic resin constituting the outer peripheral surface thereof, an inner frame portion 11 inside the outer cover member 10, and a lower surface side of the inner frame portion 11. A hollow structure having high heat insulation as shown in the figure is formed by the detachable inner cover member 13. The lid unit 2 is attached to the rear end of the shoulder member 5 via a hinge mechanism 14 so as to be rotatable in the up-down direction. A lock mechanism 15 that detachably engages with a predetermined position on the unit side and maintains the closed state of the lid unit 2 is provided.

Reference numeral 16 denotes a steam release passage provided in the center of the lid unit 2, and reference numeral 17 denotes a steam release pipe detachably provided at a lower portion of the steam release passage 16 and having a function of returning to the end. is there.

Furthermore, the side in the space between the inner casing 6 and outer casing 1, the cooking heater H _1, insulation heater H _2, a microcomputer for performing energization control of the shoulder the heater H ₃ each Control board 2 provided with a microcomputer control unit (see reference numeral 100 in FIG. 2 to be described later)
4 are accommodated.

At the upper end of the front part of the shoulder member 5, a rounded operation panel 21 constituting a rice cooker operation section is provided. The operation panel 21 includes, for example, a menu switch for specifying a rice cooking menu (for example, white rice, fast-cooking, scorching, roasting, rice porridge, brown rice, etc.), a rice cooking switch, a warming switch, a clock switch, not shown.
A timer switch (timer rice reservation switch), a clock and a time setting switch of the timer, a time and minute setting switch of the clock and the timer, a cancel switch, a liquid crystal display 29, and the like are provided.

On the other hand, on the rear side of the operation panel 21, an operation board 32 provided with the liquid crystal display 29 and the various switch parts is provided.

Next, based on the electric circuit diagram shown in FIG. 2, in the electric rice cooker according to the present embodiment, a rice cooker temperature detecting circuit at normal temperature, an abnormal temperature judging circuit at abnormal temperature, and an abnormal temperature judging circuit at abnormal temperature judging. The configuration of the heating stop circuit section (reset circuit section) will be described.

As described above, in the conventional rice cooker temperature detecting circuit (the circuit shown in FIG. 11) having the abnormal temperature judging circuit and the heating stop circuit (reset circuit), the port at the microcomputer control unit 100 Since the detection resistance value cannot be switched, there is a problem that the reading accuracy (resolution) of the rice cooker temperature is low particularly in a high temperature region.

[0037] Therefore, in rice device temperature detection circuit in FIG. 2, in order to solve such problems, a conventional rice device temperature detection circuit second comparator C ₂ is a temperature region determination means with respect of Figure 11 Add a, by entering the rice device temperature detection signal V ₀ which thermistor T of the center sensor 7 parts to the second comparison input terminal of the comparator C _2, the second switching reference voltage setting of the comparator C ₂ For example, a switching reference voltage Vs set corresponding to a switching reference temperature of 100 ° C. (see FIG. 4) for separating the low temperature region and the high temperature region of the rice cooker temperature detection region of the electric rice cooker by the resistors R ₈ and R ₉ . Compare the comparison result (high temperature region of 100 ° C. or more, 100
The transistor Q _{0 is controlled} to ON (high-temperature region of 100 ° C. or higher) and OFF (low-temperature region lower than 100 ° C.) via the resistors R ₇ and R ₆ corresponding to the low-temperature region lower than 100 ° C.
The microcomputer control unit 1 determines which of these states
Input to the Po terminal on the 00 side and the thermistor T
Insert in parallel to rice device temperature detection resistor (dividing resistor) R _1, R ₂ of rice device temperature detecting circuit switched resistor R ₁₀ at the time is the rice device temperature is above 100 ° C. hot detected by, rice device and so as to increase the reading accuracy by enlarging the voltage variation width of the temperature detection signal V _0.

If the detection resistance value switching means is configured in this manner, for example, in comparison with the conventional (FIG. 11) rice cooker temperature detection characteristic shown in FIG. 4 (b), the characteristic shown in FIG. 4 (c) can be appropriately switched in the high temperature region of 100 ° C. or higher, and the microcomputer control unit 10 can be switched to the high temperature region.
The reading accuracy (resolution) of the rice cooker temperature with respect to 0 can be sufficiently increased, and the variation in the detected temperature can be reduced.

Therefore, for example, as shown in the rice cooking characteristics of FIG. 3, water absorption (40 ° C.), total number judgment (40 to 50 ° C.), cooking (40 to 100 ° C.), end of boiling detection (130 ° C.),
Spotted (100 ° C), scorched (170 ° C), warm (70 ° C)
℃) in each process, it is possible to accurately detect the rice cooker temperature and perform appropriate heating amount control,
The reliability of the performance of detecting an abnormal temperature (220 ° C. or higher) on the microcomputer control unit 100 side before the _first comparator C ₁ as the abnormal temperature determination circuit operates is also improved.

In the above case, as described above, the rice cooker temperature detecting resistor (voltage dividing resistor) R ₁ , on the thermistor T side,
When the switching resistor R ₁₀ in parallel with R ₂ is inserted, of course rice device temperature detection voltage V ₀ which thermistor T becomes higher. as a result,
When put the value of the second comparator C ₂ switching reference voltage Vs as is, the relationship of the input voltage Vs <V
Since ₀ becomes a relationship, the second output of the comparator C ₂ becomes H again, which may cause hunting.

[0041] Therefore, in this embodiment, in the divided voltage of the second comparator C ₂ as shown in the output-side circuit the second resistor in response to changes in the output of the comparator C ₂ R _21, R ₂₂ ON, the provided another transistor Q ₀₁ to OFF operation, the second output of the comparator C ₂ is L
Since when the transistor Q ₀₁ is turned ON and, as will be inserting a resistor R ₂₃ in parallel with the second comparator C ₂ switching reference voltage setting resistor R _8, at the same time the second comparator C _{The second} switching reference voltage Vs is also increased to provide a hysteresis characteristic to prevent the hunting as described above.

Further, in the above case, for example, the first comparator C ₁ of abnormal temperature determination value (comparison reference voltage), if so set higher than the abnormal temperature determining value of the microcomputer control unit 100 side In addition, the conventional abnormal temperature determination circuit can be used as it is, and the configuration is simplified.

(Embodiment 2) Next, FIG. 5 and FIG.
7 shows a configuration of a rice cooker temperature detection circuit, an abnormal temperature determination circuit, and a heating stop circuit for abnormal temperature determination of an electric rice cooker according to Embodiment 2 of the present invention.

As described above, the microcomputer control unit 10
In order to improve the accuracy of reading the rice cooker temperature for 0,
A low-temperature region and a high-temperature region are divided according to the detection characteristics of the thermistor T, and the detection resistance value of the rice cooker temperature detection circuit is switched corresponding to the entire high-temperature region including the abnormal temperature region (220 ° C. or higher). Is preferred.

However, as means for responding to such a demand, the temperature region determining means is necessarily provided as described above to determine the low and high temperature regions, and the detection is performed according to the determined temperature region. The present invention is not limited to the means for switching the resistance value. For example, the same object can be achieved by switching the detection resistance value of the rice cooker temperature detection circuit in accordance with the cycle timing of the power supply voltage signal.

Therefore, in this embodiment, the power supply voltage signal is detected, the zero cross timing (zero cross cycle) of the power supply voltage signal is set to the high temperature area, and the other timings are set to the low temperature area. The detection resistance value is switched.

First, in the rice cooker temperature detecting circuit shown in FIG. 5, a thermistor T serving as a temperature detecting sensor for the center sensor 7 provided opposite to the center of the bottom of the rice cooker 3 as in the first embodiment. Value and voltage dividing resistor R according to temperature
The voltage value V ₀ across the thermistor T determined by ₁ and R ₂ is input to the temperature data input terminal (A / D) of the microcomputer control unit 100 as the temperature detection value of the rice cooker 3, so that the voltage value V ₀ according to the rice cooking process Rice cooker H ₁ , warming heater H ₂ ,
Shoulder heater suitable heating amount control of H ₃ is performed, so that the proper cooking, heat insulation is performed. Then, the above-mentioned voltage dividing resistors R _1, R _2, is inserted select resistor R ₁₂ is in parallel at the zero cross timing of the source voltage signal is a high temperature region as described below, the microcomputer control unit 100
Input level of the temperature detection value V ₀ which is the A / D terminal of so is switched.

[0048] That is, in this circuit the resistor R _6, a power supply voltage detection circuit consisting of R ₇ and the first transistor Q ₁ is provided, the first transistor Q ₁ is resistor R _6, R
₇ Turns on and off according to the change in the potential of the AC power supply voltage 100 (V) applied to both ends, turns off at the zero cross timing, turns on at a timing other than zero cross,
A pulse signal as shown in FIG. 6A is input to the Zc terminal of the microcomputer control unit 100, which becomes L at zero cross timing indicating a high temperature region and becomes H at other timings indicating a low temperature region.

Then, the second and third transistors Q ₂ and Q ₃ are connected via the resistors R ₈ , R ₉ , R ₁₀ and R ₁₁ according to the ON / OFF operation as shown in FIG. 6B. OFF, ON
Control.

The second transistor Q ₂ is connected to the reference voltage setting resistors R ₃ and R ₄ of the comparator C ₀ forming the abnormal temperature judging circuit by a comparative reference voltage for judging the abnormal temperature (for example, corresponding to 220 ° C. in FIG. 4). and is intended for applying to have) been set, the first transistor Q ₁ resistor R ₃ is oN at both ends of the resistor R ₄ when is oN (when the high-temperature region) and R ₄ A comparison reference voltage Vc for abnormal temperature determination set by the partial pressure ratio is generated.

Similarly, the third transistor Q ₃ is turned on when the first transistor Q ₁ is ON (in a high temperature range).
Becomes N inserting the switching resistor R ₁₂ for increasing the reading accuracy in parallel to the voltage dividing resistors R ₁ and R ₂ of the thermistors T.

Therefore, when the detection resistance value switching means is configured in this way, the switching resistance R is added to the voltage dividing resistances R ₁ and R ₂ of the thermistor T only in the high temperature region at the zero cross timing of the signal of the power supply voltage AC100 (V). ₁₂ is inserted,
The reading accuracy (resolution) of the A / D terminal on the microcomputer control unit 100 side is increased. The comparator C ₀ is abnormal temperature determining circuit only in the same state is to operate.

(Modification) The same operation as described above can be realized by, for example, employing a timer circuit and outputting the same signal as the zero-cross timing of the power supply voltage signal.

(Embodiment 3) FIGS. 7 to 9 show a rice cooker temperature detecting circuit and an abnormal temperature judging circuit of an electric rice cooker according to a third embodiment of the present invention, and heating stop at the time of abnormal temperature judging. 1 shows a configuration of a circuit.

The electric rice cooker according to this embodiment is, for example, of an electromagnetic induction heating type, and serves both for cooking rice and for keeping heat. For example, as shown in FIG. The container main body 41 has a double-walled structure having a space 40 configured to be set, and a lid 42 that covers the upper opening of the container main body 41 so as to be openable and closable.

The container body 41 includes a bottomed cylindrical outer case 43 made of synthetic resin, which forms a bottom wall and an outer wall, an inner case 44, which forms an inner peripheral surface, and both cases 43, 4
And a shoulder member 45 made of a synthetic resin for connecting the upper end of the rice cooker 4 to which the rice cooker 3 is set so as to be able to be taken out.

The inner case 44 has a top end engaged with the shoulder member 45 and is provided with a heater 46 at the center in the vertical direction of the outer peripheral surface.
And a synthetic resin dish-shaped case 44b engaged with the lower end of the cylindrical case 44a.
A center sensor 7 is provided in the center of the bottom surface of the rice cooker 3 to contact the bottom surface 3a of the rice cooker 3.

The center sensor 7 functions as an inner pot temperature detecting means for detecting the temperature of the rice cooker 3, and detects whether or not the thermistor T serving as a temperature detecting section and the rice cooker 3 are set. A rice cooker detection sensor S is provided.

An annular work coil (heating coil) 47 is arranged on the lower surface of the dish-shaped case 44b so as to surround the center sensor 7 and to correspond to the lower curved portion from the bottom surface 3a of the rice cooker 3. ing. The work coil 47 functions as means for generating an induction magnetic field to the inner pot in the high-frequency electromagnetic induction heating means. Reference numeral 48 denotes a ferrite core that shuts off the magnetic field generated by the work coil 47 so as not to affect the underlying devices. Reference numeral 49 denotes a coil table, and the coil table 49 holds the work coil 47.

The lid unit 42 includes a synthetic resin upper plate 42a forming the upper surface, a synthetic resin lower plate 42b forming the outer peripheral annular portion on the lower surface, and a heat radiation cover for covering the opening in the lower plate 42b. A hollow structure is formed by the plate 42c. The lid unit 42 is connected to the shoulder member 4.
5 is rotatably attached to one side via a hinge mechanism 50, and a lid unit 42
And a lock mechanism 51 that engages with a predetermined position of the cover unit 42 to maintain the closed state of the lid unit 42. Reference numeral 52 denotes a steam outlet, and 53 denotes a lid heater.

An operation board 55 is provided on the front side peripheral portion of the space 40 while being supported by the mounting member 54.

[0062] In the electromagnetic induction heating type electric cooker as described above, in the case of adopting the rice device temperature detection circuit such as the first and second embodiments, the comparison reference voltage of the comparator C ₀ of the abnormal temperature determining circuit , The electromagnetic induction noise of the work coil 47 may cause a malfunction.

In this embodiment, for example, FIG.
Unlike the first and second embodiments, such a circuit is used to generate the comparison reference voltage within a short time only at the zero-cross timing of the power supply voltage signal as shown in the time chart of FIG. In addition, malfunctions due to electromagnetic induction noise are prevented.

That is, in FIG. 8, the symbol C ₀ is a comparator for judging an abnormal temperature similar to that of the second embodiment, R ₁₅ and R ₁₆ are comparison reference voltage setting resistors for judging the abnormal temperature, and T is The thermistors, R ₁ and R ₂ are the voltage dividing resistors, and Rs is a heating stop circuit (reset circuit) when abnormal temperature is determined.

On the other hand, reference numeral Q ₄ denotes a transistor inserted between the reference voltage setting resistors R ₁₅ and R ₁₆ and the power supply +5 (V) line, and the base of the transistor Q ₄ has a diode D _1. , D ₂ and resistors R ₁₃ and R ₁₄ are provided.

This power supply voltage signal detection circuit is connected to the AC power supply 1
00 (V) through resistors D ₁₃ and R ₂ via diodes D ₁ and D _2.
Detected as a divided voltage of _14, by only ON operation briefly transistor Q ₄ at the zero-cross timing, caused a comparison reference voltage for abnormal temperature determination at both ends of the resistor R _16, actuates the comparator C ₀ It has become.

Therefore, according to this configuration, the abnormal temperature is determined based on the zero-cross timing (FIG. 9B) of the power supply voltage signal (FIG. 9A) with the work coil 47 OFF and low electromagnetic induction noise. And the reliability of the abnormal temperature determination is improved.

Note that D ₃ and D ₄ are backflow prevention diodes.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a rice cooker main body of an electric rice cooker according to Embodiment 1 of the present invention.

FIG. 2 is an electric circuit diagram showing a configuration of a rice cooker temperature detection circuit of the electric rice cooker.

FIG. 3 is a time chart showing rice cooking temperature characteristics of the electric rice cooker.

FIG. 4 is a graph showing a switching characteristic of a rice cooker temperature detection accuracy of the electric rice cooker.

FIG. 5 is an electric circuit diagram showing a configuration of a rice cooker temperature detecting circuit of the electric rice cooker according to Embodiment 2 of the present invention.

FIG. 6 is a time chart showing the operation of the circuit.

FIG. 7 is a cross-sectional view showing a configuration of a rice cooker main body of an electric rice cooker according to Embodiment 2 of the present invention.

FIG. 8 is an electric circuit diagram showing a configuration of a rice cooker temperature detection circuit of the electric rice cooker.

FIG. 9 is a time chart showing the operation of the rice cooker temperature detection circuit.

FIG. 10 is an electric circuit diagram showing a configuration of a rice cooker temperature detecting circuit of the electric rice cooker according to the first conventional example.

FIG. 11 is an electric circuit diagram showing a configuration of a rice cooker temperature detection circuit of an electric rice cooker according to a second conventional example.

[Explanation of symbols]

100 microcomputer control unit, C ₁ Other 1 comparators, C ₂ is the second comparator, C ₀ is a comparator,
Rs is a heating stop circuit (reset circuit), D ₀ , D ₁ ,
D ₂ , D ₃ and D ₄ are diodes, Q ₁ is a first transistor, Q ₂ is a second transistor, Q ₃ is a third transistor, Q ₀ and Q ₄ are transistors, and T is a thermistor.

Claims (6)

(57) [Claims] 1. A microcomputer control unit which reads a detected value of a rice cooker temperature from a rice cooker temperature detector and controls a heating amount of the heating unit at the time of cooking or maintaining the temperature. When the rice cooker temperature detection value detected by the detection means is in an abnormal temperature state equal to or more than a predetermined value, the abnormal temperature determination circuit determines that the rice is in an abnormal temperature state, and performs the heating operation of the heating means at the time of cooking or maintaining the temperature. In the electric rice cooker configured to be stopped, the temperature range of the rice cooker temperature detection value detected by the rice cooker temperature detection unit without using the microcomputer control unit is determined, and the detection resistance of the rice cooker temperature detection unit is determined. A rice cooker temperature detecting device for an electric rice cooker, comprising a detection resistance switching means for switching a value. 2. The detection resistance value switching unit compares the detected rice cooker temperature value detected by the rice cooker temperature detection unit with a predetermined reference temperature that separates a low-temperature region from a high-temperature region to determine a temperature region. When the detected rice cooker temperature detected by the rice cooker temperature detector is in a high-temperature region higher than a predetermined reference temperature that separates the low-temperature region and the high-temperature region, the detection resistance value of the rice cooker temperature detector is switched. The rice cooker temperature detecting device for an electric rice cooker according to claim 1, wherein: 3. A microcomputer control unit that reads the detected value of the rice cooker temperature from the rice cooker temperature detector and controls the heating amount of the heating unit when cooking or maintaining the temperature. When the rice cooker temperature detection value detected by the detection means is in an abnormal temperature state equal to or more than a predetermined value, the abnormal temperature determination circuit determines that the rice is in an abnormal temperature state, and performs the heating operation of the heating means at the time of cooking or maintaining the temperature. In the electric rice cooker configured to be stopped, a detection resistor for detecting a power supply voltage signal and switching a detection resistance value of the rice cooker temperature detection means based on the detected power supply voltage signal without passing through the microcomputer control unit. A rice cooker temperature detecting device for an electric rice cooker, comprising a value switching means. 4. The detection resistance value switching means detects a zero cross timing of a power supply voltage signal, and switches the detection resistance value of the rice cooker temperature detection means at the zero cross timing of the power supply voltage signal. The rice cooker temperature detecting device for an electric rice cooker according to claim 3. 5. The apparatus according to claim 1, wherein the detection resistance switching means is constituted by a hardware circuit.
5. The rice cooker temperature detecting device for an electric rice cooker according to 2, 3 or 4. 6. The heating means comprises an electromagnetic induction heating means,
6. The rice cooker temperature detecting device for an electric rice cooker according to claim 3, wherein the abnormal temperature determining circuit operates at a zero cross timing of the power supply voltage signal.