JPH0449759B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a temperature control device applied to an electric heater such as an electric cooker or an induction cooker.

[Prior art and its problems]

A conventional temperature control device of this type, which is an object of improvement of the present invention, will be explained with reference to FIG. 1 is a cooking pot (an object to be heated); 2 is a top plate on which the cooking pot is placed; 3 is an induction heating coil (electric heating means); and 4 is a temperature sensing element attached to the back surface of the top plate 2. Temperature sensing element 4 is made of a thermistor having negative temperature resistance characteristics, and together with resistors 5 and 6 and variable resistor 7 constitutes a bridge circuit. A voltage comparator 8 compares the resistance voltage of the thermistor 4 and the resistance voltage of the variable resistor 7. A controller 9 controls the current of the induction heating coil 3, and is operated by the output of the voltage comparator 8. That is, when the voltage comparator 8 detects that the temperature of the heated object detected by the thermistor 4 is lower than the temperature set by the variable resistor 7, the controller 9 causes the induction heating coil 3 to A current flows through it, and when the temperature detected by the thermistor is higher than the set temperature, the current is cut off.

By the way, in the above conventional temperature control device,
As shown in FIG. 2, the temperature detected by the thermistor 4 (dotted line a) reaches the control temperature _T0 set by the variable resistor 7 at time _t1 , and the controller 9 detects the current c of the induction heating coil 3. Even if the power is cut off, the temperature of the cooking pot 1 (solid line b) continues to rise. This is cooking pot 1
It is based on the heat capacity of Therefore, the temperature a detected by the thermistor 4 also follows this.
When time passes and the temperature detected by the thermistor 4 falls to the control temperature T ₀ at time t ₂ , current c flows through the induction heating coil 3 again, but the temperature is dependent on the heat capacity of the cooking pot, just as it was when the temperature rose. The temperature continues to drop for a while, and then starts to rise and reaches the control temperature T ₀ at time t ₃ .

As described above, in the conventional temperature control device shown in FIG. 1, the temperature control response is delayed due to the heat capacity of the object to be heated, and ripples occur in the temperature transition, making it difficult to maintain a uniform temperature. Therefore, it is unsuitable for heating objects (cooking) that require uniform temperature.

[Purpose of the invention]

The present invention is a temperature control device that does not have the above-mentioned drawbacks, that is, a temperature control device in which the temperature change of the heated object is small and the temperature of the heated object can be maintained almost constant through fine temperature control. The purpose of this invention is to provide a control device.

[Structure of the invention]

The temperature control device for an electric heater of the present invention includes a heating control means for controlling the heating amount of the electric heating means for heating an object to be heated, a control temperature setting means for setting a control temperature, and a temperature control device for detecting the temperature of the object to be heated. temperature detection means for inputting the temperature signal detected by the temperature detection means at regular time intervals; and storage means for storing the temperature signal input by the temperature signal input means. , a calculation means for calculating and amplifying the difference between the temperature data stored by the storage means and the temperature data input from the temperature signal input means, and adding the difference between the temperature data and the temperature data inputted from the temperature signal input means; It is characterized by comprising a comparison means for comparing the output of the setting means, and the operation of the heating control means is controlled by the output of the comparison means.

The configuration of the present invention will be explained with reference to the block diagram of FIG. 11 is an object to be heated (cooking pot), 12 is a top plate on which it is placed, and 13 is an electric heating means (induction heating coil). Reference numeral 14 denotes a temperature detecting means for detecting the temperature of the object to be heated using a thermistor having a negative temperature resistance characteristic attached to the back surface of the top plate 12. 15 is a temperature signal input means for inputting the temperature signal detected by the thermistor 14 at regular time intervals; 16 is a storage means for storing the temperature signal input by the temperature signal input means 15. Reference numeral 17 denotes a calculation means for calculating and amplifying the difference C between the temperature data A stored in the storage means 16 and the temperature data B input from the temperature signal input means 15, and adding this to B. Reference numeral 18 denotes a control temperature setting means comprising a variable resistor or the like for manually setting the control temperature by the user. 19 is a comparison means (voltage comparator) for comparing the output of the calculation means 17 with the output of the control temperature setting means 18;
control the behavior of The heating control means 20 controls the heating of the electric heating means 13.

Next, its operation will be explained with reference to FIG. When the electric heating means 13 is energized, the temperature T of the object to be heated (deep fryer) gradually rises as time t passes. The control temperature is set to T ₀ by the control temperature setting means 18.
For example, suppose the temperature is set to 180℃. The calculation constant (amplification degree) of the calculation means 17 is assumed to be n. The temperature signal input means 15 inputs the temperature detected by the thermistor 14 at fixed time intervals Δt, and stores the temperature in the storage means 1.
6 remembers this. The calculation means 17 is the storage means 1
For example, at time t ₄ , the temperature data T _{3 at time t 3 and} the temperature data T ₄ inputted from the input means 15 at time t ₄ are calculated as the difference T ₄ −T ₃ . is amplified n times and added to T ₄ to output temperature data T _s . The voltage comparator 19 compares the output (operating temperature T _s ) of the calculation means 17 with the control temperature T ₀ (180° C.) set by the control temperature setting means 18 . The heating control means 20 inputs the output of the voltage comparator 19, causes current to flow through the electric heating means 13 when T _s is lower than T ₀ , and cuts it off when T _s is higher than T ₀ . Figure 4 shows T _s at t ₄
becomes higher than T ₀ , indicating that the current c has been cut off.

When the current of the electric heating means 13 is cut off, the temperature of the object to be heated 11 continues to rise for a while, but then begins to fall. Temperature control during lowering is performed in the same way, and when T _s becomes lower than T ₀ , the current is turned on again. In other words, the device of the present invention controls electrical heating using temperature data (operating temperature T _s ) obtained by multiplying the rise or fall of temperature at time Δt by an arithmetic constant n and adding this to the detected temperature. The heating control means 20 controls heating or heating stop before the temperature of the object to be heated reaches the control temperature. Note that the calculation constant n is appropriately determined depending on the type and characteristics of the object to be heated 11.

[Explanation of Examples]

FIG. 5 shows an embodiment of the present invention in which the calculation means 17 of FIG. 3 is constituted by a first calculation means 17a and a second calculation means 17b. The first calculation means 17a compares the temperature data A stored in the storage means 16 and the temperature data B inputted from the temperature signal input means 15, and determines whether the difference C is positive or negative. The second arithmetic means 17b amplifies the difference C between A and B and adds this to B, but the arithmetic constant n that determines the degree of amplification is determined by the sign determined by the first arithmetic means 17a. different values will be adopted.

An object to be heated with a large heat capacity such as a deep fryer has a small thermal time constant when the temperature rises, so in order to prevent overshoot, the output of the second calculation means 17b (operating temperature T _s ) and the control temperature T ₀ (180 ℃). Furthermore, since the thermal time constant is relatively large when the temperature drops, there is no need to make a large difference between T _s and T ₀ . Therefore, the arithmetic constant n is a large number, for example 3, when the temperature is rising, that is, when the above C is positive, and a small number, for example 2, is adopted when the temperature is falling, that is, when the above C is negative. In this way, it becomes possible to perform fine temperature control.

〔Effect of the invention〕

Conventional devices controlled the heating by the electric heating means when the temperature of the object to be heated reached or dropped to the control temperature, so the temperature of the object to be heated was controlled by the fourth control temperature.
As shown by the dotted line b in the figure, ripples of a magnitude determined by the heat capacity of the object to be heated occur in the temperature transition. The device is configured to calculate an appropriate operating temperature using a calculation constant that is set based on the heat capacity of the object to be heated, and to control the heating of the object based on this temperature. The temperature of the object can be controlled to a substantially uniform temperature with small ripples, as shown by the solid line a in FIG. 4, and the object of the invention can be achieved.

[Brief explanation of the drawing]

Figure 1: Diagram showing the configuration of a conventional temperature control device,
Fig. 2: An explanatory diagram of the operation of the device shown in Fig. 1, Fig. 3: A block diagram showing the configuration of the temperature control device of the present invention, Fig. 4: An explanatory diagram of the operation of the temperature control device of the present invention, Fig. 5
Figure: A block diagram showing the configuration of an embodiment of the temperature control device of the present invention. 11...Object to be heated, 12...Top plate, 13
... electric heating means, 14 ... temperature detection means, 15 ... temperature signal input means, 16 ... storage means, 17 ... calculation means, 18 ... control temperature setting means, 19 ... comparison means,
20...Heating control means.

Claims (1)

[Scope of Claims] 1. Heating control means for controlling the heating amount of the electric heating means for heating the object to be heated, control temperature setting means for setting the control temperature, and temperature detection means for detecting the temperature of the object to be heated. , temperature signal input means for inputting the temperature signal detected by the temperature detection means at regular time intervals; storage means for storing the temperature signal input by the temperature signal input means; a calculation means for amplifying and adding the difference between the stored temperature data and the temperature data input from the temperature signal input means; and an output of the calculation means and an output of the control temperature setting means. 1. A temperature control device for an electric heater, comprising a comparison means for comparison, and controlling the operation of the heating control means based on the output of the comparison means. 2. The calculation means compares the temperature data A stored by the storage means with the temperature data B input from the temperature signal input means, and determines whether the difference C is positive or negative; a second calculation means that calculates the difference C between A and B, amplifies this using an arithmetic constant adopted according to the sign determined by the first calculation means, and adds this to the B; A temperature control device for an electric heater according to claim 1, characterized in that it is configured by: