JPH04277491A - Temperature control device of induction heating cooking apparatus - Google Patents

Abstract

PURPOSE:To stabilize the temp. control of induction heating by equipping a hysteresis on the turn-on/off control of induction heating operation for changing temperature of the object to be heated using a comparator. in which the reference voltage can be switched by a computer. CONSTITUTION:No.1 resistance is connected in series to a thermistor 2 of a temp. sensing element, and a partial voltage obtained by dividing the DC power supply voltage is compared with No.1 reference voltage which is set in a voltage comparator 3 according to the voltage at the jointing point of the power supply with a circuitry consisting of a series connection of No.2 resistance and No.3 resistance, and the result from comparison is entered into a microcomputer as Input-1. The control is so made that heating is stopped when Input-1 exceeds the No.1 reference voltage and is started when becomes lower than No.2 reference voltage set by grounding N0.4 resistance in connection with the joining point of No.2 and No.3 resistances with Output-1 of the computer. Thereby a stable temp. control of induction heating type can be achieved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for a heating cooker used in general households.

0002

2. Description of the Related Art FIG. 2 shows a method of measuring temperature in a general cooking appliance having a temperature control function using a conventional microcomputer.

First, in FIG. 2-(a), Rth is
This thermistor is a temperature detection means, and this thermistor is
As the temperature increases, its resistance value decreases.

[0004] COMP is a comparator that compares the voltages at point a and point b, and outputs high when point a has a higher voltage than point b, otherwise outputs low, and outputs the result. is input to the input 1 terminal of the microcomputer.

In other words, by making the ratio of the resistance value Rth of the thermistor at the temperature to be controlled, the resistance value of the resistor Rx of a predetermined composite resistance circuit, and the ratio of the resistance values of resistors R22 and R23 equal, the thermistor When the temperature measured by is lower than the temperature to be controlled, the resistance value Rth of the thermistor increases, so the voltage at point b becomes lower than the voltage at point a, the output of comparator COMP becomes Low, and the thermistor measures When the temperature becomes higher than the temperature to be controlled, the voltage at point b becomes higher than the voltage at point a, and the output of comparator COMP becomes High. The output of this comparator is input to the input terminal of the microcomputer, and when the input is High, heating is performed, and when the input is Low, heating is stopped, thereby controlling the temperature to be determined.

FIG. 2-(b) shows the temperature change of the heated object at this time. Temperature θ to be controlled when heating starts at time 0
Heating is continued until the temperature reaches θ, and the heater is turned off when the temperature θ is reached. Even after the heater is turned off, with a heater using a general electric heating wire, the temperature continues to rise for a while due to residual heat, and then falls. Further, even when heating is started when the temperature has fallen below the temperature θ, the temperature starts to rise after the temperature has fallen for a while until the heater is sufficiently heated. That is, in temperature control using a heating wire, the temperature of the object to be heated is maintained at approximately the temperature θ by repeating this operation based on the difference between ON/OFF of the heater and the temperature change of the object to be heated.

[0007] By switching the resistance value of the composite resistance circuit Rx using the output terminal of the microcomputer, it is possible to control the temperature in multiple stages.

[0008]

[Problems to be Solved by the Invention] However, when controlling the temperature of an induction heating cooker with the above-mentioned conventional configuration, in the induction heating method, it is difficult to turn ON/OFF the induction heating due to the characteristic that the heated object itself generates heat. Since the temperature of the heated object changes almost without deviation, heating can be turned ON/OFF.
The disadvantage was that F had to be carried out very frequently, making it virtually impossible to control the temperature.

[0009] The present invention solves the above-mentioned problems, and is capable of stably operating temperature even with the characteristic of induction heating cookers that the ON/OFF of induction heating and the temperature change of the heated object operate with almost no deviation. The purpose is to provide a control device.

0010

[Means for Solving the Problems] In order to solve the above problems, the temperature control device for an induction heating cooker of the present invention includes an induction heating device comprising a high frequency power source, a heating coil, etc., and a DC voltage that outputs a predetermined DC voltage. a microcomputer having a power supply, a plurality of input terminals and a plurality of output terminals operated by the DC power supply, a thermistor as a temperature detection element for measuring the temperature of a load such as a pot heated by the induction heating device; A DC power supply is applied to both ends of a circuit in which a resistor of the first resistor and a thermistor of the temperature sensing element are connected in series, and a voltage obtained by dividing the voltage of the DC power supply by the resistance values of the first resistor and the thermistor is divided into a second resistor and a thermistor of the temperature sensing element. The DC power supply is applied to a circuit in which a resistor and a third resistor are connected in series, and the voltage at the connection point is compared with a predetermined first reference voltage of a voltage comparator provided, and the output of the voltage comparator at that time is input into the microcomputer,
The voltage output obtained by dividing the voltage of the DC power supply by the resistance value of this first resistor and the thermistor is output from this predetermined first resistor during the heating operation.
If the voltage becomes higher than the reference voltage, the heating is stopped, and while the heating is stopped, a fourth resistor connected to the connection point of the second resistor and the third resistor is grounded by an output terminal of the microcomputer. If the voltage becomes lower than a predetermined second voltage set by the above, the control means is provided to start heating using the output of the induction heating cooker.

[0011]

[Function] According to the above configuration, the temperature control device for an induction heating cooker according to the present invention can turn on/off the heating of the induction heating cooker.
Even though the temperature changes of the FF and the object to be heated are almost the same, stable temperature control can be performed because there is a difference between the temperature at which the heating is turned on and the temperature at which the heating is turned off.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of an embodiment of the present invention will be described below with reference to FIG.

FIG. 1-(a) shows a control circuit of a temperature control device for an induction heating cooker according to an embodiment of the present invention, in which 1 is an input terminal of a microcomputer, 2 is a thermistor which is a temperature detection element, and 3 is a voltage A comparator is a comparator, 4 is a reference voltage changing circuit that provides two levels of reference voltage to the comparator 3, 5 is a composite resistance circuit that can switch a plurality of resistance values, and 6 determines the resistance value of the composite resistance circuit 5. This is the output of a microcomputer for.

FIG. 2-(b) shows the temperature control operation of the induction heating cooker of the present invention. When heating starts at time 0, the temperature of the heated object increases and the resistance value Rth of the thermistor 2 decreases, resulting in a temperature θ+ that is Δθ higher than the desired control temperature θ.
When Δθ is reached, the voltage determined by the ratio of the resistance value Rth of the thermistor 2 and the combined resistance Rx becomes the voltage determined by the voltage of the comparator 4 when the resistance R4 of the reference voltage changing circuit 4 is disconnected from the grounded state by the output 1 of the microcomputer. 1
becomes higher than the reference voltage of comparator 4, and the output of comparator 4 becomes L.
The signal is reversed from OW to High and the microcomputer outputs a signal to stop induction heating. Then, as the temperature of the heated object decreases almost simultaneously with the stop, the resistance value Rth of the thermistor 2 increases, and when the temperature θ - Δθ, which is Δθ lower than the desired control temperature θ, the resistance value Rth of the thermistor 2 and the combined resistance increase. The voltage determined by the ratio of Rx becomes lower than the second reference voltage of the comparator 4 when the resistor R4 of the reference voltage changing circuit 4 is grounded by the output 1 of the microcomputer, and the output of the comparator 4 changes from High to Low. The microcomputer outputs a signal to start heating. By repeating this operation, the temperature of the heated object can be adjusted to the desired control temperature θ
Stably controlled within the range of ±Δθ.

By switching the resistance value Rx of the composite resistance circuit 7 using the output terminal 8 of the microcomputer, the temperature can be controlled in multiple stages.

[0016]

As described above, the present invention applies a DC power source to both ends of a circuit in which a first resistor and a thermistor as a temperature sensing element are connected in series, and generates a direct current using the resistance values of the first resistor and the thermistor. The voltage obtained by dividing the voltage of the power supply is applied to a circuit in which a second resistor and a third resistor are connected in series, and the DC power supply is applied to a circuit in which a second resistor and a third resistor are connected in series.
The output of the voltage comparator at that time is input to the microcomputer, and the voltage output obtained by dividing the voltage of the DC power supply by the resistance value of this first resistor and the thermistor is calculated at this predetermined voltage during heating operation. If the voltage becomes higher than the first reference voltage, the heating is stopped, and while the heating is stopped, the fourth resistor connected to the connection point of the second resistor and the third resistor is grounded by the output terminal of the microcomputer. If the voltage becomes lower than the predetermined second voltage, the control means is provided to start heating using the output of the induction heating cooker.
Stable temperature control is also possible in induction heating type cooking appliances in which the temperature of the object to be heated changes in accordance with ON/OFF of heating.

[Brief explanation of the drawing]

FIG. 1 (a) A configuration diagram of a control device of an induction cooking device according to an embodiment of the present invention (b) An operation timing chart of an induction cooking device according to an embodiment of the present invention.

FIG. 2 (a) Configuration diagram of a control device of a conventional induction heating cooker; (b) Operation timing chart of a conventional induction heating cooker;

[Explanation of symbols]

1. First input of microcomputer 2. Thermistor of temperature detection element 3. Comparator 4. Reference voltage changing circuit 5. Composite resistance circuit.

Claims (1)

[Claims] Claim 1: An induction heating device comprising a high frequency power source, a heating coil, etc., a DC power source that outputs a predetermined DC voltage, and a microcomputer that is operated by the DC power source and has a plurality of input terminals and a plurality of output terminals. , a DC power source is applied to both ends of a circuit in which a thermistor as a temperature sensing element that measures the temperature of a load such as a pot heated by the induction heating device, a first resistor and the thermistor as the temperature sensing element are connected in series. , the voltage obtained by dividing the voltage of the DC power supply by the resistance value of the first resistor and the thermistor is applied to the circuit in which the second resistor and the third resistor are connected in series, and the voltage at the connection point is The voltage is compared with a predetermined first reference voltage of a voltage comparator provided, and the output of the voltage comparator at that time is input to a microcomputer, and the voltage of the DC power source is determined by the resistance value of this first resistor and thermistor. If the divided voltage output becomes higher than the predetermined first reference voltage during the heating operation, the heating is stopped, and while the heating is stopped, the second resistor and the third
control to start heating by the output of the induction heating device when the voltage becomes lower than a predetermined second voltage established by grounding the fourth resistor connected to the connection point of the resistor through the output terminal of the microcomputer; Temperature control device for induction heating cooker with means.