JPH0410647B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for controlling the temperature of a heated object in a cooking device that heats the bottom surface of a container of a heated object, such as an electric stove or an induction heating cooker.

Configuration of conventional example and its problems A conventional temperature control method of this type will be described using an induction heating cooker as an example. As shown in FIG. 1, temperature detection means detects the bottom temperature T _p of the container P of the object to be heated O.
TD, temperature setting means S for setting the target heated object temperature T _OS , and power variable means C for changing the input power P _i of the heating coil H;
Generally, the temperature T O of the object to be heated O is controlled by changing the input power P _i so that the output (T _p ) of the TD and the output g (T _{OS )} of the temperature setting means S are equal. It was hot.

However, with this method, as described below,
For example, when a load is applied to the object to be heated O, such as when cooking tempura, there is a problem in that the set temperature _TOS and the temperature of the object to be heated T _O are significantly different. This problem will be explained below using FIGS. 1 to 3. In FIG. 1, P _O is the power supplied to the object to be heated O through the bottom surface of the container P for the object to be heated, and P _a is the electric power released from the object to be heated O to the surroundings. To simplify the explanation, assuming that the variable range of the set temperature T _OS is sufficiently small, it can be expressed as P _a = α (T _p − T _a ), P _p = β (T _p − T _O ) …(1) . Here, α and β are constants, and T _a is the ambient temperature. In the steady state, P _p =P _a ...(2), so from the above equations (1) and (2), T _O =β/α+βT _p +α/α+βT _a ...(3) is obtained. Therefore, if the ambient temperature T _a is constant, the first
In the figure, by keeping the bottom surface temperature T _p of the heated object container constant, the heated object temperature T _O can be kept constant. However, as shown in Figure 2,
When the load M is applied to the object to be heated O, thermal energy is transferred to the load M according to the difference between the temperature of the load M and the temperature of the object to be heated T _O , so that the above equation (3) no longer holds true. That is, if the power supplied to the load M is P _n , then P _p =P _a +P _n (4), so from the equations (1) and (4), T _O = β/α + βT _p + α/ α+βT _a −P _n /α+β …(5). As can be easily seen by comparing equations (4) and (5) above, by applying a load M equivalent to the electric power P _n , the temperature of the object to be heated T _O becomes constant, while the bottom surface temperature T _p of the object to be heated container is kept constant. Even if it is maintained, it will decrease by P _n /(α+β). If a considerable amount of time has passed after the load M is turned on, the temperature of the load M will become equal to the temperature of the heated object T _O and the transfer of thermal energy will stop.
P _n = 0, and the temperature of the heated object T _O recovers to the temperature when there is no load, that is, the initial set temperature T _OS . However, if the heat capacity of the load M is large, or when the load is When loading and unloading is repeated continuously, the heat capacity of the load can be considered to be approximately infinite during cooking, and the temperature of the heated object increases.
T _O constantly decreases to a greater extent than the set value T _OS .
This problem is illustrated in FIG. In FIG. 3, the horizontal axis represents the load amount P _n and the vertical axis represents the temperature of the heated object T _O.

Purpose of the Invention The present invention solves these conventional problems, allows the temperature of the heated object to be maintained at a set value regardless of the amount of load, and improves the accuracy and stability of the heated object temperature. The present invention provides a temperature control method for a heating cooker.

Structure of the Invention The method for controlling the temperature of an object to be heated in a heating cooker according to the present invention includes a temperature detecting means for detecting the temperature of the bottom surface of a container for the object to be heated, a power detecting means for detecting input power of the heating cooker, and an object to be heated. a temperature setting means for setting the temperature of the temperature detecting means; a power variable means for changing the input power; and an arithmetic means receiving the output of the power detecting means and the output of the temperature detecting means as inputs, and the arithmetic means is the temperature detecting means. A calculation is performed to correct the output using the output of the power detection means, the output of the calculation means is compared with the output of the temperature setting means, and the input power is controlled by the power variable means according to the difference, thereby controlling the temperature of the heated object. The temperature of the heated object is maintained at the set value, and the temperature of the heated object can be maintained at the set value regardless of the load amount by power feedback by the power detection means.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the accompanying drawings. In Figure 4, O is the object to be heated,
P is a heated object container, M is a load, H is a heating coil,
TD is a temperature detection means for detecting the bottom temperature T _P of the object to be heated container P, and S is the temperature of the object to be heated.
C is a temperature setting means for setting T _OS ; C is a power variable means for changing the input power P _i of the heating coil H;
PD is power detection means for detecting the input power P _i ;
F is an arithmetic means that outputs a function G [T ( _P ), h (P _i )] whose variables are the output (T _P ) of the temperature detection means TD and the output h (P _i ) of the power detection means PD. , the input power P _i is controlled so that the output g (T _OS ) of the temperature setting means S and the output G [T ( _P ), h (P _i )] of the calculation means F are equal. If the power transmission efficiency from the heating coil H to the heated object container P is η, the power P _p supplied to the heated object has the following relationship: P _p =η P _i −P _a ′ (6). Here, P _a ′ is the electric power released from the heated object container to the surroundings, and can be expressed as P _a ′=ξ(T _p −T _a ) (7). Here ξ is a constant. From the second equation (1), (6), and (7), we obtain T _p =(1+ξ/β)T _p -η/βp _i -ξ/βT _a (8). Therefore, in order to control T _O = T _OS (const.), T _OS = aT _p −bP _i −C where a=1+ξ/β, b=η/β, C=ξ/βT _a …(9 ) can be controlled to satisfy. As can be easily seen, for example, (T _p )=aT _p , g(T _OS )=T _OS , h(P _i )=bP _i G[(T _p ), h(P _i )]=(T _p ) -h(P _i )-C, the system shown in FIG. 4 can operate to satisfy the above equation (9). Therefore, as shown in Figure 5, regardless of the load amount, the temperature of the heated object T _O
can be kept at the set value T _OS . This operation is
This is nothing but control by correcting the heated object container bottom temperature T _P with the input power P _i according to the load amount P _n to determine the heated object temperature T _O.

FIG. 6 shows a specific circuit example of the embodiment shown in FIG. In Figure 6, 1 is a thermistor, and resistor 2
Together, they constitute the temperature detection means TD. Reference numeral 7 denotes a variable resistor, which constitutes the temperature setting means S. 8 is current transformer, 9 is current transformer 8
load resistance, 10 is a rectifier diode, 11,1
2 is a resistor, 13 is a capacitor, and 8 to 13 above constitute the power detection means PD,
Generates a voltage proportional to input power P _i . resistance 1
5, 16, 17, 18, and an operational amplifier 19 constitute the temperature detection means F, and the operational amplifier 19 constitutes the temperature detection means TD.
and the output of the power detection means PD. 3 is an operational amplifier, 4 and 5 are gain setting resistors, and constitute a differential amplifier circuit 6 which amplifies and outputs the differential voltage between the output of the temperature setting means S and the output of the arithmetic means F. Input power P _i to heating coil H
The power variable means C for changing the input power changes the input power as an increasing function of the output of the differential amplifier circuit 6. As can be easily seen, if the gain of the differential amplifier circuit 6 is sufficiently large, the system shown in FIG. 6 operates so that the output of the temperature setting means S and the output of the calculation means F become equal. Therefore, the characteristics of thermistor 1 and resistances 2, 9, 11, 12, 15, 1
By adjusting the values of 6, 17, and 18, the formula
The bottom surface temperature T _p of the object to be heated container can be controlled so as to satisfy (9), and the temperature T _O of the object to be heated can be maintained at the set value T _OS regardless of the load amount.

Effects of the Invention As is clear from the above embodiments, the method for controlling the temperature of a heated object in a cooking device of the present invention includes a function in which the output of the power detection means and the output of the temperature detection means are variables;
By comparing the output of the temperature setting means and controlling the input power using the power variable means, the temperature of the heated object can be maintained at the set value regardless of the load amount, improving the accuracy and stability of the temperature of the heated object. It is something that can be measured. There is also a method that achieves the same purpose by calculating the set value and input power and comparing it with the bottom temperature of the container to be heated.
The method of the present invention is characterized in that it is very convenient for displaying the temperature of a heated object because a function using the output of the power detection means and the output of the temperature detection means as variables directly represents the temperature of the object to be heated.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional temperature control method, Fig. 2 is an energy flow chart explaining the characteristics of the conventional example shown in Fig. 1, and Fig. 3 is a characteristic diagram showing the characteristics of the conventional example shown in Fig. 1. 4 is a block diagram showing one embodiment of the method of the present invention, FIG. 5 is a characteristic diagram showing the characteristics of the embodiment of FIG. 4, and FIG. 6 is a specific circuit diagram of the embodiment of FIG. 4. TD...Temperature detection means, PD...Power detection means, S
...Temperature setting means, C...Power variable means.

Claims (1)

[Scope of Claims] 1. Temperature detection means for detecting the temperature of the bottom surface of the object container of the heating cooker, power detection means for detecting the input power of the heating cooker, and a temperature for setting the temperature of the object to be heated. It has a setting means, a power variable means for changing the input power, and a calculation means for inputting the output of the power detection means and the output of the temperature detection means, and the calculation means changes the output of the temperature detection means to the output of the power detection means. The temperature of the object to be heated is maintained at the set value by performing a computation for correction, comparing the output of the calculation means and the output of the temperature setting means, and controlling the input power by the power variable means according to the difference. A method for controlling the temperature of a heated object in a heating cooker. 2. The method for controlling the temperature of a heated object in a heating cooker according to claim 1, wherein the output of the calculation means is a linear function using the output of the power detection means and the output of the temperature detection means as variables.