JPH0468755B2 - - 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 an object, such as an electric stove or an induction cooking device.

Configuration of conventional example and its problems For convenience of explanation, an induction heating cooker will be described below as an example.

Conventionally, this type of temperature control method, as shown in FIG. 1, includes a temperature detection means TD that detects the bottom surface temperature Tp of a container P of the object to be heated O, and a temperature setting that sets the target temperature Tos of the object to be heated. Means S, heating coil H
has a power variable means C that changes the input power Pi, and changes the input power Pi so that the output f (Tp) of the temperature detection means TD and the output g (Tos) of the temperature setting means S become equal. Therefore, it was common to control the temperature Tos of the object O to be heated.

However, as described below, this method has a problem in that when a load is applied to the object O, such as when cooking tempura, the set temperature Tos and the temperature To of the object to be heated are significantly different. This problem will be explained below with reference to FIGS. 1, 2, and 3. In Figure 1, Po is the electric power supplied to the object to be heated O through the bottom of the container P for the object to be heated, and Pa
is the power emitted from the heated object O to the surroundings.
For simplicity, assuming that the variable range of the set temperature Tos is sufficiently small, it can be expressed as Pa = α (To - Ta), Po = β (Tp - To) ... (1). Here, α and β are constants, and Ta is the ambient temperature. In the steady state, Po=Pa (2), so from equations (1) and (2), To=β/α+βTp+α/α+βTa (3) is obtained. Therefore, if the ambient temperature Ta is constant, the first
By keeping the temperature Tp of the bottom surface of the heated object container constant in the system shown in the figure, the temperature To of the heated object can be kept constant. However, as shown in FIG. 2, when the load M is applied to the object to be heated O, the load M
Since thermal energy is transferred to the load M according to the difference between the temperature of and the temperature of the heated object To, the above equation (3) no longer holds true. That is, if the power supplied to the load M is Pm, then Po=Pa+Pm... (4) Therefore, from the equations (1) and (4), To=β/α+βTp+α/α+βTa−Pm/α+β… …(Five
) becomes. As can be easily seen by comparing equations (4) and (5) above, by applying a load M equivalent to the electric power Pm, the temperature of the heated object To is maintained constant at the bottom surface temperature Tp of the heated object container. also decreases by Pm/(α+β). After a considerable amount of time has passed after turning on the load M, the temperature of the load M will reach the temperature of the heated object To
is equal to and there is no transfer of thermal energy, so
Pm = O, and the temperature of the heated object To recovers to the temperature when there is no load, that is, the initial set temperature Tos, but if the heat capacity of the load M is large, or when the load is turned on or raised, such as when cooking tempura, etc. When 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.
To constantly decreases considerably below the set value Tos.
This problem is illustrated in FIG. In FIG. 3, the horizontal axis represents the load amount Pm, and the vertical axis represents the temperature of the heated object To.

Purpose of the Invention The present invention solves these conventional problems, enables the temperature of the heated object to be kept constant with high accuracy regardless of the amount of load, and improves the accuracy and stability of the temperature of the heated object. The present invention provides a method for controlling the temperature of a modern heating cooker.

Structure of the Invention The temperature control method of the present invention includes a temperature detection means for detecting the temperature of the bottom surface of a container for a heated object, a power detection means for detecting input power of a cooking device, and a temperature setting for setting the temperature of the heated object. means, a power variable means for changing the input power, and an arithmetic means for outputting a function using the output of the power detecting means and the output of the temperature setting means as variables, wherein the output of the arithmetic means and the output of the temperature detecting means are By controlling the input power by the power variable means so as to match,
A device that maintains the temperature of the heated object with high accuracy and constant, and can maintain the temperature of the heated object with high accuracy and constant regardless of the amount of load by feedback of the magnitude of input power by this input power detection means. It is.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In FIG. 4, O is the object to be heated, P is the container for the object to be heated, M is the load, H is the heating coil, TD is a temperature detection means for detecting the bottom surface temperature Tp of the container P for the object to be heated, and S is the purpose. temperature setting means for setting the heated object temperature Tos; C is a power variable means for changing the input power Pi of the heating coil H;
PD is a power detection means for detecting the input power Pi;
F is an arithmetic means that outputs a function F [g(Tos), h(Pi)] whose variables are the output g(Tos) of the temperature setting means S and the output h(Pi) of the power detection means PD,
The input power Pi is controlled so that the output f (Tp) of the temperature detection means TD and the output F [g (Tos), h (Pi)] 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, then there is the following relationship: Po=ηPi−Pa′ (6). Here, Pa′ is the electric power released from the heated object container to the surroundings, and can be expressed as Pa′=ξ(Tp−Ta) ……(7). Here ξ is a constant. The above formula (1),
From (2), (6), and (7), we obtain To=(1+ξ/β)Tp−η/βPi−ξ/βTa ……(8). Therefore, in order to control To=Tos (const), Tp=aPi+bTos+c However, a=η/β+ξ, b=β/β+ξ, c=ξ/β+
Tp should be controlled so that ξ Ta...(9) is satisfied. As can be easily seen, for example, f (Tp) = Tp, g (Tos) = bTos, h (Pi) = aPi F[g (Tos), h (Pi)] = g (Tos) + h (Pi) + c. Then, since the system shown in FIG. 4 controls Tp so as to satisfy the above equation (9), the temperature of the object to be heated can be maintained at To, regardless of the load amount, as shown in FIG. 5. Qualitatively, this behavior can be explained by the amount of load
This is nothing but raising the bottom surface temperature Tp of the object to be heated according to Pm to maintain the temperature To of the object to be heated at the set value Tos.

FIG. 6 shows a specific circuit example of the embodiment shown in FIG. In FIG. 6, reference numeral 1 denotes a thermistor which together with a resistor 2 constitutes the temperature detecting means TD. 7 constitutes the temperature setting means S by a variable resistor. 8 is a current transformer, 9 is a load resistance of the current transformer 8, 10 is a rectifying diode, 11 and 12 are resistors, 13 is a capacitor, and the power detection means
It constitutes a PD and generates a voltage proportional to the input power Pi. Resistance 14, 15, 16, 17, 1
8. The operational amplifier 19 constitutes the calculation means F, and outputs a linear combination of the output of the temperature setting means S 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 that amplifies and outputs the differential voltage between the output of the temperature detection means TD and the output of the calculation means F. The power variable means C for changing the input power Pin to the heating coil H 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.
It operates so that the output of TD and the output of the calculation means F are equal. Therefore, the characteristics of thermistor 1 and resistances 2, 9, 11, 12, 14, 15, 16, 1
By setting the values of 7 and 18 appropriately, the bottom surface temperature Tp of the heated object container can be controlled so as to satisfy equation (9), and the heated object temperature To can be controlled regardless of the load amount.
can be kept at the set value Tos.

Effects of the Invention As is clear from the above-mentioned embodiments, the temperature control method of the present invention specifically calculates and returns the magnitude of the input power of the cooking device to control the temperature of the bottom surface of the container of the object to be heated. The temperature of the object to be heated can be maintained constant with high accuracy regardless of the amount of load, and the accuracy and stability of the temperature of the object to be heated can be improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a temperature control method in a conventional induction heating cooker, Figure 2 is an explanatory diagram showing the flow of energy in the same induction heating cooker, and Figure 3 is an explanatory diagram showing the flow of energy in the induction heating cooker.
The figure is a temperature characteristic diagram of the same induction heating cooker, FIG. 4 is a block diagram showing a temperature control method in an induction heating cooker showing one embodiment of the present invention, and FIG. 5 is a temperature characteristic diagram of the same induction heating cooker. , FIG. 6 is an electric circuit diagram showing a specific example of the induction heating cooker. TD...Temperature detection means, PD...Input 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 to be heated container, power detection means for detecting the input power of the cooking device, temperature setting means for setting the temperature of the object to be heated; comprising a power variable means for changing the input power, and an arithmetic means for outputting a function using the output of the power detection means and the output of the temperature setting means as variables,
A method for controlling the temperature of a heated object in a cooking device in which the temperature of the heated object is maintained at a set value by controlling the input power by the power variable means so that the output of the calculation means and the output of the temperature detection means match. . 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 substantially linear function with the output of the power detection means and the output of the temperature setting means as variables.