JP2932449B2 - Electric rice cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In general, a sensor holder at a lower portion of an inner pot of an electric rice cooker is cut off when the temperature of the inner pot becomes an abnormal temperature equal to or higher than a predetermined value to supply power to heating means such as a heater. Although there is a thermal fuse that stops the operation,
There is an inconvenience that the thermal fuse must be replaced once it is blown.

Therefore, recently, for example, two sets of temperature sensors such as thermistors are provided separately from the temperature fuses in the sensor holder, and the heating amount of the heating means such as a heater is determined based on the output of one of the temperature sensors indicating the temperature of the inner pot. While comparing the output of the other temperature sensor with a predetermined reference value,
By providing heating stop control means for stopping the supply of power to the heating means by the heating control means when the output of the temperature sensor is equal to or more than a predetermined reference value, the temperature detection value of the inner pot of the temperature sensor When the temperature becomes equal to or higher than the abnormal temperature detection value, a method is proposed in which the heating operation of the heating control means is stopped to suppress an increase in the temperature of the inner pot, thereby protecting the apparatus.

According to this configuration, the operation of the microcomputer of the control unit can be ensured even when the program runs out of control, and the sensor holder does not need to have a conventional thermal fuse. It is simpler and more compact.

[0005]

However, in the case where the temperature sensor for controlling the heating amount of the heating means and the temperature sensor for detecting the abnormal temperature are separately provided as described above, there are the following disadvantages.

(1) Since two sets of temperature sensors are required, the number of parts is large and the cost is high.

[0007] (2) It is not easy to provide two sets of temperature sensors in a sensor holder having a large space restriction, and the diameter of the sensor holder is inevitably increased. (3) The diameter of the sensor holder is increased. If it is large, the degree of adhesion of the contact surface with the bottom portion of the inner pot via the sensor cap deteriorates due to unevenness in unevenness accuracy. In addition, heat capacity is large,
Poor response during heat transfer. As a result, the temperature detection performance decreases.

(4) The structure of the sensor holder becomes complicated, and the number of steps for processing and assembly increases, resulting in high cost.

[0009]

SUMMARY OF THE INVENTION The inventions according to claims 1 and 2 of the present application have been made for the purpose of solving the above-mentioned problems, respectively, and have the following means for solving the problems. It is configured.

(1) The invention of claim 1 That is, first, the electric rice cooker of the invention of claim 1 of the present application comprises an inner pot in which rice is accommodated, heating means for heating the inner pot,
Heating control means for controlling a heating amount of the heating means based on a temperature detection value of a temperature sensor for detecting a temperature of the inner pot; and a temperature of the inner pot which is a predetermined temperature based on a temperature detection value of the temperature sensor. In the electric rice cooker having the heating control means for stopping the heating operation of the heating control means, the temperature detection value of the temperature sensor, the heating control means or one of the heating stop control means A temperature detection input switching means for switching and inputting is provided, and when the detected temperature value of the temperature sensor is not equal to or higher than a predetermined temperature, the heating control means is activated, while when the detected temperature value of the temperature sensor is equal to or higher than a predetermined temperature. The heating stop control means is configured to operate.

That is, in the electric rice cooker of the present invention, the output of one temperature sensor is switched and input by the temperature detection input switching means, so that the temperature control means for controlling the heating amount by the heating control means and It is also used as a temperature detection unit for heating stop control by the heating stop control unit, and when the temperature detection value of the temperature sensor is not equal to or higher than a predetermined temperature, the heating control unit is operated when it is normal.
When the temperature detected by the temperature sensor becomes abnormally higher than a predetermined temperature, the heating stop control means is operated.

Therefore, in the case of this configuration, one of the heating control means or the heating stop control means is appropriately operated by one temperature sensor in accordance with the detected temperature value, and the detected temperature value is set to the predetermined temperature. The normal heating amount control and the abnormal heating stop control when the detected temperature value is equal to or higher than the predetermined temperature can be easily realized, and the configuration can be simplified.

(2) Invention of Claim 2 Next, the electric rice cooker according to the invention of claim 2 of the present invention provides an inner pot in which rice is stored, heating means for heating the inner pot, and a temperature of the inner pot. Heating control means for controlling a heating amount of the heating means based on a temperature detection value of the temperature sensor to be detected; and heating when the temperature of the inner pot becomes a predetermined temperature or more based on a temperature detection value of the temperature sensor. In an electric rice cooker comprising a heating stop control means for stopping the heating operation of the control means,
Power supply voltage monitoring means for monitoring a power supply voltage, and a temperature detection value input switch for switching and inputting the temperature detection value of the temperature sensor to either the heating control means or the heating stop control means by the power supply voltage monitoring means. Means for inputting the detected temperature value of the temperature sensor to one of the heating control means or the heating stop control means in accordance with a power supply voltage monitoring signal from the power supply voltage monitoring means. Is configured to operate.

That is, in the electric rice cooker according to the present invention, one temperature sensor is provided with a temperature detecting means for controlling a heating amount by the heating control means and a heating stop control means in accordance with the cycle of the power supply voltage monitoring signal. This is commonly used as a temperature detecting means for controlling the heating to stop. Then, in accordance with the detected temperature value, one of the heating control means and the heating stop control means is appropriately operated, for example, the heating amount control and the temperature detection value when the detected temperature value is not higher than the predetermined temperature are normal. Can easily realize the heating stop control at the time of abnormality when the temperature becomes equal to or higher than the predetermined temperature, and the configuration can be simplified.

[0015]

(Embodiment 1) Hereinafter, the configuration and operation of an electric rice cooker according to Embodiment 1 of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the structure of the main body of the electric rice cooker.

The electric rice cooker according to the present embodiment is formed, for example, of a heater type, and serves both for cooking rice and for keeping heat. The electric rice cooker includes a bottomed cylindrical outer case 1 configured so that an inner pot (rice cooker) 3 can be set therein, and a lid unit 2 that covers an upper portion of the outer case 1. It has a rice cooker.

The outer case 1 comprises a bottomed cylindrical cover member 4 made of a synthetic resin, and a synthetic resin shoulder member 5 coupled to the upper end of the cover member 4. Is provided with a bottomed cylindrical inner case (protection frame) 6 for setting the inner pot 3 so that it can be taken out.

The inner case 6 is formed of a bottomed cylindrical thin metal plate, and the upper end thereof is engaged with the shoulder member 5. And, in the center of the bottom wall 6b of the inner case 6,
As will be described later, a center sensor 7 is provided in contact with the center of the bottom surface of the inner pot 3 as described later.

The center sensor 7 has a thermistor THm as a temperature detecting sensor for detecting the temperature of the inner pot 3, that is, the temperature of the rice, and an inner pot set sensor for detecting whether or not the inner pot 3 is set. A sensor unit 7a containing an inner pot detection sensor 8 and the like is built in so as to be able to move up and down.

On the upper surface side of the bottom wall 6b of the inner case,
A rice-cooking heater MH as a rice-cooking heating means is provided on the lower side so as to surround the sensor portion 7a of the center sensor 7,
In addition, heater plates 9 each having a heat retaining heater SH are provided on the side. The heater plate 9 is in close contact with the bottom surface of the inner pot 3 set in the inner case 6, and heats the bottom 3a of the inner pot 3 and its outer periphery with good heat conductivity.

On the other hand, the lid unit 2 has an outer cover 10 made of a synthetic resin constituting the outer peripheral surface thereof and an inner cover (poly cover) made of a synthetic resin constituting the outer peripheral annular frame portion on the inner peripheral surface of the outer cover 10. A hollow structure without an inner cover as shown in the figure is formed by a heat radiating plate 11 which detachably covers an inner opening of the inner cover 11 in the radial direction through a polycover packing 12 having a V-shaped cross section. Have been. 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 vertical direction. A lock mechanism 15 that engages with the position and maintains the closed state of the lid unit 2 is provided.

Reference numeral 16 denotes a steam release passage, 20 denotes a steam discharge pipe fitted into the steam release passage 16, F
H is a lid heater as a heat sink heating means. The lid heater FH is mounted on the upper surface side of the heat radiating plate 13 with good heat conductivity by being covered with a heat radiating cover and fixed closely.

Further, between the inner case 6 and the outer case 1 on the front side of the rice cooker main body, the amount of power supply to the rice cooker MH, the lid heater FH, the heat retaining heater SH and the like, and the power supply voltage monitoring control are performed. A control board 29 having a control unit including a microcomputer (hereinafter, referred to as a microcomputer control unit) is accommodated. Further, the shoulder member 5
Is provided with a wide operation panel 30 which is obliquely lowered and wide as shown in the figure. In this operation panel 30 part, various switches (menu, heat retention, start, separate cooking, timer, etc.) necessary for cooking rice,
Cooking rice menu selected by each of those switches,
There is provided a display unit for displaying a switch operation level and the like so as to be visually recognized by a user.

Next, based on the electric circuit diagram shown in FIG.
The configuration of the electric control circuit unit in the electric rice cooker according to the present embodiment will be described. Parts corresponding to the respective parts shown in FIG. 1 are denoted by the same reference numerals.

In the figure, AC100V is an AC 1 for general household use.
It is a commercial power supply of 00V. The user connects the power plug on the rice cooker body side to a household power outlet and uses it.

A series circuit of the triac TRc and the heater SH connected to the 100 V power supply circuit forms a heating circuit for the heater SH. Heating heater S
H heats the inner pot 3 from the side of the inner pot 3 of the rice cooker body,
In each step of the rice cooking or heat retaining step, heat is generated according to the output value of the triac control signal from the microcomputer control unit 100. That is, the microcomputer control unit 1
00 of P ₁ terminal is output triac control signal, the control signal voltage of the P ₁ terminal becomes "L", the "L" signal output is applied to the base of the triac driving transistor Q ₁ through a resistor R ₄ , The transistor Q ₁
Turns ON. The current (gate current) flows to the gate of the triac TRc through the resistor R ₃ connected to the gate of the triac TRc, triac TRc
Turns on, and the heat retaining heater SH generates heat to a desired set temperature.

At the same time, the power supply circuit includes a relay R
₁ which is an open / close contact (normally open contact) and rice cooker MH
And a heating circuit of the rice cooker MH, which is connected in series, is connected in parallel. Cooking heater MH of the cooking heater heating circuit is also controlled by the output value of the control signal from the microcomputer control unit 100 (output from P ₂ terminal). That is, if the control signal voltage from the P ₂ terminal to "H", the signal output of the H potential via a resistor R ₅ resistor R
Is supplied to the _19, the transistor Q ₂ is turned ON by a potential generated at both ends of the resistor R _19. Then, the relay coil RL of the relay R connected to the collector of the transistor Q ₂ is excited, the switching contacts R of the relay R
To make the S _1. As a result, electricity is supplied to the rice cooking heater MH, and the heating operation is started.

The diode D ₁ connected in parallel to the relay coil RL is for protecting the transistor Q ₂ by absorbing the back electromotive voltage generated from the relay coil RL.

The resistor R ₆ is for applying a power supply voltage to the reset circuit 41 via the AC power supply line. The reset circuit 41 resets the program of the microcomputer control unit 100 when the power supply voltage supplied to the microcomputer control unit 100 falls below the rated operating voltage of the microcomputer control unit 100, and stops all operations of the microcomputer part. Things.

The capacitor C ₁ is for smoothing the input power supply voltage to the microcomputer control unit 100, and includes a Zener diode D _{4 in} parallel with the capacitor C _1.
Is provided for the purpose of setting the input power supply voltage to the microcomputer control unit 100 to the constant rated operating voltage.
The rectifier diode D ₂ is for rectifying the AC 100 V AC power supply to DC, and the resistor R ₁ reduces the voltage obtained by rectifying AC 100 V to DC to a predetermined set voltage value, thereby reducing the microcomputer control unit 100. It is intended to correspond to the operating voltage of

[0032] The resistor R ₂ is, above its one end AC10
Together are connected to a power supply circuit of 0V, it is connected to the base of the transistor Q ₃ and the other end, by a transistor Q ₃ converts the sinusoidal voltage of the AC100V supply a square wave voltage, via a resistor R ₇ The input is made to the power supply voltage monitoring input terminal K of the microcomputer control unit 100. Diode D ₃ which connects between the base and emitter of the transistor Q ₃ are a bypass diode of the transistor Q ₃ protection. The resistor R ₂ , the transistor Q ₃ , the resistor, and the diode D ₃ constitute a power supply voltage monitoring means in combination with the power supply voltage determination function of the microcomputer control unit 100.

Further, the illustrated LCD is a liquid crystal display for performing menu display and time display on the operation panel 30 of the rice cooker main body, and the illustrated LED is a state of the rice cooking process such as rice cooking and a heat retention timer on the operation panel 30. It is a light emitting diode for displaying.

The switches shown in FIG.
Various operation switches for using the rice cooker provided in the unit 0, such as a rice cooker switch, a cancel / heat switch, a timer set switch, a time set switch, and the like. On the other hand, XC is an oscillation circuit for generating a system clock signal for operating the microcomputer,
For example, it is composed of a ceramic vibrator, a capacitor and the like.

With the above circuit, the thermistor THm, which is a temperature detecting sensor of the center sensor 7 provided opposite the center of the bottom of the inner pot 3 and the voltage dividing resistor R ₈ ,
When the voltage values determined by R ₉ and R ₁₀ are input to the temperature data input terminal (A / D) of the microcomputer control unit 100 as the temperature detection value of the inner pot 3, the rice cooking heater MH corresponding to the rice cooking process, The heating amount control of the heat retention heater SH is performed, and appropriate rice cooking is performed.

Next, the configuration of the abnormal temperature protection circuit unit 50 (see the chain line in FIG. 2) combined with the above-described control circuit will be described.

Reference symbol THm denotes a thermistor provided in the above-mentioned center sensor section.
Based connected transistor Q ₄ are connected to the power supply voltage monitoring input terminal K of the microcomputer control unit 100 via the resistor R ₁₁ to.

[0038] When the input voltage of the power supply voltage monitoring input terminal K is "H", the collector and emitter is turned ON transistor Q _4, the temperature data input terminal (A / D input terminal) of the thermistor THm is the microcomputer Connected to
The heating temperature control at the time of the normal temperature which is not higher than the predetermined temperature based on the input temperature data as the detected temperature of the inner pot is performed. That is, at this timing, the rice cooking control program of the microcomputer control unit 100 controls the heating amounts of the rice cooking heater MH and the heat retaining heater SH while watching the temperature data.

[0039] Then the input voltage of the power supply voltage monitoring input terminal K becomes "L", the transistor Q ₄ of the collector and the emitter is turned OFF, the thermistor THm are disconnected from the control circuit of the microcomputer control unit 100,
Detection protection control is performed when an abnormal temperature is equal to or higher than a predetermined temperature.

[0040] That is, the the thermistor THm, also connected the emitter of the transistor Q ₄ and the opposite polarity of the transistor Q ₅ is at the same time, the transistor Q ₅
The base is connected to the power supply voltage monitoring input terminal K of the microcomputer control unit 100 via the resistor R _12. Therefore, the transistor Q _5, the input potential of the power supply voltage monitoring input terminal K is the OFF, whereas turned ON when the "L" when the "H". That is, depending on the signal potential of the power supply voltage monitoring input terminal K by the transistors Q ₄ and Q ₅ , the thermistor THm is connected to a temperature data input terminal on the premise of microcomputer control on the microcomputer control unit 100 side and an abnormal temperature not related to microcomputer control. The detection and protection circuit 50 are alternately switched.

Next, the configuration and operation of the abnormal temperature detection protection circuit 50 by the switching will be described with reference to the thermistor THm, for example.
There will be described in a state connected to the input side of the transistor Q shown by ON in the ₅ first comparator CP _1.

That is, in this state, the thermistor T
Hm and the resistor R ₁₄ on the collector side of the transistor Q ₅
The first divided comparator CP shown in FIG.
₁ inverting input terminal (-)
_13, divided by the divided voltage with R ₁₄ is connected to a set reference voltage non-inverting input terminal of the first comparator CP ₁ as (threshold voltage) (+). In the abnormal temperature determination circuit formed as described above, the resistance value of the thermistor THm is large when the temperature detected by the thermistor THm is not higher than a predetermined temperature lower than the temperature at the time of abnormality that is higher than the predetermined temperature. The first comparator CP ₁
The voltage at the inverting input terminal (−) is lower than the voltage at the non-inverting input terminal (+). Therefore, the output of the first comparator CP ₁ is in a state of "H".

On the other hand, when the transistor Q ₅ is turned OFF, the inverting input terminal from the voltage of the voltage of the non-inverting input terminal (+) (- -) voltage is almost 0V next, again inverting input terminal () because even lower, remains never change, the output of the first comparator CP ₁ "H".

[0044] In the present embodiment, as illustrated, the H output through a resistor R _20, and is further connected to a second non-inverting input terminal of the comparator CP ₂ (+).

[0045] Incidentally, the capacitor C ₂ connected to the non-inverting input terminal of the illustrated second comparator CP ₂ (+) is a capacitor for charging, whereas the resistor R ₁₇ is the resistance for discharge, charge and A discharge circuit is formed.

In the above state, the non-inverting input terminal (+) of the second comparator CP ₂ is “H”, and the reference voltage (the second comparator) determined by the voltage dividing resistors R ₁₆ and R _18. inverting input terminal of the craters CP ₂ (-) second output of the comparator CP ₂ higher than voltage) is "H", the circuit even though connected to the input terminal d of the reset circuit 41 is no Normally microcomputer control unit 1
A heating amount control operation of 00 is performed.

Next, when the temperature detected by the thermistor THm becomes abnormal temperature state, the resistance value of the thermistor THm is reduced, a first non-inverting comparator CP ₁ that is determined by the resistance of the thermistor THm and the resistor R ₁₄ inverting input terminal of the comparator CP ₁ the voltage at the input terminal (+) is determined by the voltage dividing resistor R ₁₄ and R ₁₅ (-) is higher than the reference voltage of the side, the first output of the comparator CP ₁ is " L "
become.

[0048] Note that when turned OFF by the signal of the power supply voltage monitoring input terminal K of the transistor Q ₅ is a microcomputer control unit 100, the voltage of the first non-inverting input terminal of the comparator CP ₁ (+) is so substantially to 0V , an inverting input terminal (-) reference voltage side lower than the first output of the comparator CP ₁ becomes "H".

That is, when the thermistor THm detects an abnormal temperature, the output of the _first comparator CP1 becomes
“H” → “L” → “H” is repeated by the voltage signal of the power supply voltage monitoring input terminal K.

Then, the second comparator C
Voltage at the non-inverting input terminal (+) of the P ₂ is charged to the capacitor C ₂ through a resistor R _20, it is discharged by the subsequent resistor R _17.

For this reason, the voltage of the non-inverting input terminal (+) of the second comparator CP ₂ becomes lower than the voltage of the inverting input terminal (−) determined by the resistors R ₁₆ and R ₁₈ ,
The output of the comparator CP ₂ of becomes "L".

Therefore, when the output terminal c of the _second comparator CP2 is connected to the input terminal d of the reset circuit 41 as shown in the figure, the input voltage of the reset circuit 41 becomes "L", Since the control system of the unit 100 is reset and the heating amount control itself is stopped, the power supply to the rice cooker MH and the heat retaining heater SH is also cut off, and the safety of the rice cooker main body is secured.

The electric rice cooker according to the present embodiment is configured as described above, and outputs the temperature detection output of the thermistor THm, which is the same temperature sensor, by the microcomputer control unit 100 as the heating control means or the heating stop control means. A detection output switching means comprising transistors Q ₄ and Q ₅ for switching to and inputting to one of the certain abnormal temperature protection circuit sections 50 is provided, and the detection output switching means monitors the operating power supply voltage to the microcomputer control unit 100. is configured to operate switches the detection output by the power supply voltage monitoring input signals from the transistor Q ₂ side power supply voltage monitoring input means for the thermistor THm is a temperature sensor of the one, the amount of heating by the microcomputer control unit 100 Temperature detection means for control and temperature for heating stop control by the abnormal temperature protection circuit unit 50 It is designed to be shared with the detection means.

Therefore, in the case of this configuration, the provided thermistor can be shared by the temperature detecting means for controlling the heating amount and the temperature detecting means for controlling the heating stop.
For example, the sensor unit 7a of the center sensor 7 can be freely installed at an appropriate position where the inner pot temperature detection accuracy is highest, such as the center, and the diameter of the sensor unit 7a can be reduced as much as possible. become.

As a result, it is possible to reduce costs by reducing the number of parts, simplifying the structure, and reducing the number of processing and assembling steps.

Further, by improving the close contact accuracy of the contact surface between the inner pot and the sensor section 7a and reducing the heat capacity of the sensor section 7a, the temperature detection performance and responsiveness of the inner pot are improved.

As a result, according to the electric rice cooker, it is possible to realize a simple and low-cost center sensor structure and to provide an abnormal temperature detecting device having higher responsiveness as compared with the conventional one, thereby improving safety and safety. Reliability is also improved.

In addition, according to the above configuration, since the protection circuit is provided separately from the control unit centering on the microcomputer control unit 100, even if the microcomputer control unit 100 goes out of control, for example, the influence is prevented. You don't have to.

In the above configuration, the temperature detection signal (temperature detection value) from the thermistor THm, which is a temperature detection sensor, is transmitted to the microcomputer control unit 100 and the abnormal temperature protection circuit 50 according to the level of the power supply voltage monitoring input signal. Since the switching is performed, it is not necessary to exert any influence on the abnormal temperature detection and the protection operation even when the input signals on each side are subjected to necessary signal processing according to the purpose of use.

Second Embodiment Next, FIG. 3 shows a configuration of a control circuit of an electric rice cooker according to a second embodiment of the present invention.

[0061] In the structure of this embodiment, between the relay R-side transistor Q ₂ and the microcomputer control unit 100 side P ₂ terminals in the configuration of FIG 2, further inserting the switching transistor Q _6, on its base side by connecting the second output terminal C of the comparator CP ₂ via the resistor R _21, it is obtained to perform the energization cut direct cooking heater MH together with resetting of the microcomputer control unit 100.

Next, the abnormal temperature protection circuit 50 having the above configuration.
The configuration and the operation, now for example the thermistor THm is described in the state connected to the input side of the comparator CP ₁ ON by a first illustration of the transistor Q _5.

That is, in this state, the thermistor T
Hm and the resistor R ₁₄ on the collector side of the transistor Q ₅
The first divided comparator CP shown in FIG.
₁ inverting input terminal (-)
_13, divided by the divided voltage with R ₁₄ is connected to a set reference voltage non-inverting input terminal of the first comparator CP ₁ as (threshold voltage) (+). In the abnormal temperature determination circuit formed as described above, when the detected temperature of the thermistor THm is a normal temperature which is not lower than a predetermined temperature which is lower than an abnormal temperature which is higher than a predetermined temperature, the resistance of the thermistor THm values are greater, therefore the first of the inverted input terminal of the comparator CP ₁ (-) voltage is lower than the voltage at the non-inverting input terminal (+). Therefore, the output of the first comparator CP ₁ is in a state of "H".

[0064] On the other hand, when the transistor Q ₅ is turned OFF, the inverting input terminal from the voltage of the voltage of the non-inverting input terminal (+) (- -) voltage is almost 0V next, again inverting input terminal () because even lower, remains never change, the output of the first comparator CP ₁ "H".

[0065] In the present embodiment, as illustrated, the H output through a resistor R _20, and is further connected to a second non-inverting input terminal of the comparator CP ₂ (+).

[0066] Incidentally, the capacitor C ₂ connected to the non-inverting input terminal of the illustrated second comparator CP ₂ (+) is a capacitor for charging, whereas the resistor R ₁₇ is the resistance for discharge, charge and A discharge circuit is formed.

In the above state, the non-inverting input terminal (+) of the second comparator CP ₂ is “H”, and the reference voltage (the second comparator) determined by the voltage dividing resistors R ₁₆ and R _18. inverting input terminal of the craters CP ₂ (-) second output of the comparator CP ₂ higher than voltage) is "H", even if it is connected to an input terminal d of the reset circuit 41 as described above The heating amount control operation of the microcomputer control unit 100 is normally performed on the circuit without any problem.

[0068] Further, the transistor Q ₆ is also connected to the base input terminal e via the resistor R ₂₁ of the transistor Q ₆ is O
Since it is still N, the driving transistor Q of the relay R
₂ operates in response to a control signal from the P ₂ terminal of the microcomputer control unit 100, operates exactly correctly heating control functional.

Next, when the temperature detected by the thermistor THm is the abnormal temperature state, the resistance value of the thermistor THm is reduced, the first non comparator CP ₁ that is determined by the resistance of the thermistor THm and the resistor R ₁₄ inverting input terminal (+) the inverting input terminal of the comparator CP ₁ the voltage is determined by the voltage dividing resistor R ₁₄ and R ₁₅ of (-) becomes higher than the reference voltage of the side, the first output of the comparator CP ₁ is "L"
become.

[0070] Note that when turned OFF by the signal of the power supply voltage monitoring input terminal K of the transistor Q ₅ is a microcomputer control unit 100, the voltage of the first non-inverting input terminal of the comparator CP ₁ (+) is so substantially to 0V , an inverting input terminal (-) reference voltage side lower than the first output of the comparator CP ₁ becomes "H".

That is, when the thermistor THm detects an abnormal temperature, the output of the _first comparator CP1 becomes
“H” → “L” → “H” is repeated by the voltage signal of the power supply voltage monitoring input terminal K.

Then, the second comparator C
Voltage at the non-inverting input terminal (+) of the P ₂ is charged to the capacitor C ₂ through a resistor R _20, it is discharged by the subsequent resistor R _17.

For this reason, the voltage of the non-inverting input terminal (+) of the second comparator CP ₂ becomes lower than the voltage of the inverting input terminal (−) determined by the resistors R ₁₆ and R ₁₈ ,
The output of the comparator CP ₂ of becomes "L".

For this reason, when the output terminal c of the _second comparator CP ₂ is connected to the input terminal d of the reset circuit 41 as shown in the figure, the input voltage of the reset circuit 41 becomes “L” as described above. Then, the control system of the microcomputer control unit 100 is reset, and the heating amount control itself is stopped, so that the power supply to the rice cooker MH and the heat retaining heater SH is also cut off, and the safety of the rice cooker main body is secured.

[0075] Also, whereas when connecting the output terminal c of the comparator CP ₂ to the base input terminal e of the transistor Q _6, since the base input of the transistor Q ₆ is "L", the transistor Q ₆ is turned OFF , the base potential of the transistor Q ₂ is turned to the "L" transistor Q ₂
Remains OFF, and the open / close contact RS of the relay R does not operate and remains OFF, so that the rice cooking heater MH is not energized. Therefore, the safety of the rice cooker body is also ensured.

In this way, in addition to the reset of the microcomputer control unit 100, the power supply of the rice cooking heater MH can be directly cut off, and the response is high, so that the reliability of the abnormal temperature protection is further improved.

(Embodiment 3) FIG. 4 shows the configuration of a control circuit section of an IH type (induction heater type) electric rice cooker according to Embodiment 3 of the present invention.

In the figure, reference numeral 200 denotes a control unit of the electric rice cooker, which includes various switch units, a display unit, a power supply unit, a warming heater, a microcomputer control unit, and the like, and a work coil 35. , 34 are work coil drive IGBTs (work coil drive power transistors),
33 IGBT drive circuit for IGBT driving, 31 the pulse width modulation circuit, 32 is synchronous trigger circuit, C ₁₁ is the resonant capacitor, C _12, C ₁₃ is a smoothing capacitor, 36 choke coil, 37 is a diode bridge circuit ,
These constitute a known rice cooker control circuit of an electric rice cooker.

A heating control circuit using the same thermistor THm and an abnormal temperature protection circuit 50, which are completely the same as those of the above embodiments, are incorporated in the circuit, and the circuit responds to the signal of the power supply voltage monitoring input terminal K. above the second comparator CP ₂ output levels (H or L) by I
By controlling the operation state (ON, OFF) of the GBT drive circuit 33, an abnormal temperature protection operation exactly the same as in the first and second embodiments is realized.

As described above, the present invention can be applied to an IH type electric rice cooker.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure 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 control circuit unit of the electric rice cooker.

FIG. 3 is an electric circuit diagram showing a configuration of a control circuit unit of the electric rice cooker according to Embodiment 2 of the present invention.

FIG. 4 is an electric circuit diagram showing a configuration of a control circuit unit of the IH type electric rice cooker according to Embodiment 3 of the present invention.

[Explanation of symbols]

33 is an IGBT drive circuit, 34 is an IGBT, 35 is a work coil, 41 is a reset circuit, 100 is a microcomputer control unit, SH is a warming heater, MH is a rice cooking heater,
THm thermistor, Q ₁ ~Q ₆ transistors, C
P ₁ and CP ₂ are comparators.

Claims (2)

(57) [Claims] 1. An inner pot in which rice is stored, heating means for heating the inner pot, and heating for controlling a heating amount of the heating means based on a temperature detection value of a temperature sensor for detecting a temperature of the inner pot. An electric rice cooker comprising control means and heating stop control means for stopping the heating operation of the heating control means when the temperature of the inner pan becomes equal to or higher than a predetermined temperature based on a temperature detection value of the temperature sensor. Temperature detection input switching means for inputting the temperature detection value of the temperature sensor by switching to one of the heating control means and the heating stop control means, and the temperature detection value of the temperature sensor is not higher than a predetermined temperature An electric rice cooker wherein the heating control means is sometimes activated, and the heating stop control means is activated when a temperature detection value of the temperature sensor becomes equal to or higher than a predetermined temperature. 2. An inner pot for accommodating rice, heating means for heating the inner pot, and heating for controlling a heating amount of the heating means based on a temperature detection value of a temperature sensor for detecting a temperature of the inner pot. An electric rice cooker comprising control means and heating stop control means for stopping the heating operation of the heating control means when the temperature of the inner pan becomes equal to or higher than a predetermined temperature based on a temperature detection value of the temperature sensor. A power supply voltage monitoring means for monitoring a power supply voltage, and a power supply voltage monitoring signal from the power supply voltage monitoring means for switching a temperature detection value of the temperature sensor to one of the heating control means or the heating stop control means. An electric rice cooker comprising a temperature detection input switching means for inputting.