JPS6161506B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating device that heats a material to be heated and an induction heating coil while moving them relative to each other.

FIG. 1 is a block diagram of a conventional induction heating device.
In the figure, 1 is a continuously moving heated material in the shape of a plate or rod, 2 is an induction heating coil (hereinafter referred to as a heating coil), 3 is a heating power source for supplying high-frequency power, and 4 is a heating source for supplying high-frequency power. a transformer, 5 a radiation thermometer for measuring the temperature of the heated material 1;
Reference numeral 6 denotes a speed detector for detecting the moving speed of the heated material 1, which includes a roller 7. 8 is a control panel, which includes a square root calculator 8a, a temperature controller 8b and an adder 8.
c is provided. Reference numeral 9 denotes an operation panel provided with a temperature setting device 9a and a ratio setting device 9b.

Generally, in such an induction heating device,
The heated mass of the heated material per unit time is proportional to its moving speed, and the thermal energy required for heating is constant for the heated mass if the temperature rise value is set to the same value. Therefore, the voltage applied to the heating coil must be such that the resulting thermal energy is a constant proportion of the heated mass of the material to be heated passing through it per unit time.

Normally, electrical energy is proportional to the square of the voltage applied to a circuit, so in this case, where the final goal is the amount of heat required, the voltage, which is a means, is calculated backwards.
There is a relationship that when the required amount of heat doubles, the applied voltage will be multiplied by √2.

This relationship is the basis of the heating adjustment principle of such an induction heating device, and can be summarized as follows.

(moving speed of heated material) ∝ (mass per unit time passing through the coil) ∝ (required energy to raise the temperature to a certain level) ∝ (2 of the voltage applied to the coil)
(multiplier value) Next, the operation will be explained. The signal from the speed detector 6 is processed by a square root calculator 8a and provided to an adder 8c. Further, the deviation value between the temperature signal of the heated material 1 measured by the radiation thermometer 5 and the temperature signal instructed by the temperature setting device 9a is determined by the temperature controller 8b.
Adder 8 due to negative feedback from
given to c. The signal added by the adder 8c is sent as a voltage command signal to the heating power source 3 via the ratio setting device 9b.

Therefore, in this state, the theoretically required voltage is generated from the feeding speed of the heated material 1 to heat it, the temperature of the heated material 1 is measured, and the excess or deficiency of the voltage relative to the target temperature is determined. adjustment to obtain the desired target temperature. Among these, the role of the ratio setting device 9b is that even if the material has the same shape, the material properties such as electrical resistance differ and even if the same voltage is applied, the temperature may not rise the same. It is used for different purposes.

By the way, in conventional devices, when the material to be heated 1 is preliminarily heated by other means or when heating is performed in multiple stages, the applied voltage decreases after the temperature of the material to be heated 1 exceeds a set value. Therefore, it will overheat, and when used in a high temperature range of 1200° or more and a wide speed change range, radiant heat dissipation is extremely large, so a voltage command proportional to the square root of the speed can only be controlled under one speed condition. There were disadvantages in that characteristics could not be matched and it was difficult to change the target temperature over a wide range.

This invention was made to eliminate the above-mentioned drawbacks, and an object of the present invention is to obtain an induction heating device that can be used in a wider temperature range and can perform more precise temperature control.

FIG. 2 is a block diagram showing an embodiment of the present invention. In FIG. 2, 1 to 9 are the same as the conventional one. 5b is a radiation thermometer that measures the temperature of the heated object 1 before heating; 8e is a multiplier; 8f is an adder; 8d
is a subtracter, and 9c is a fine difference corrector. Also, a square root calculator 8a' is similar to the conventional one but has different characteristics. That is, the square root calculator 8a' can select an exponent value in the range of 0.5 to 1 in the root calculation by adjusting the exponent setter 8g.

Next, the operation will be explained. A signal corresponding to the temperature difference before and after heating is obtained by a subtracter 8d, and multiplier 8e is added to this signal.
The system signal multiplied by the speed signal, calculated by the square root calculator 8a', and the ratio set by the ratio setter 9b, and the temperature signal from the regulator 8b are added by the adder 8c.
Then, the signal from the adder 8c and the signal from the fine difference setting device 9c are added together by an adder 8f to obtain a voltage command signal for the heating power source 3.

In such a configuration, the calculation basis for the required amount of heat incorporates information on how much the temperature will rise, so even if large changes are made to the speed or heating target temperature, the error will not widen as in the past. do not have.
When the rate of radiant heat dissipation of the heated material 1 is large and it is necessary to apply more power than the theoretical value, that is, to apply a higher voltage, set the appropriate index between 0.5 and 1 based on the experimentally measured characteristic values and graphs. You can find it and select it using the index setter 8g. Even so, if there is a difference between the target temperature and the actual measurement value, the regulator 8b of the adjustment system functions to try to follow the target temperature. Although it is undeniable that there is still an error of about ±20° C. between the target temperature and the target temperature after the temperature is sufficiently stabilized, this error can be canceled by the fine difference corrector 9c. The ratio setter 9b has the same role as the conventional one, but a square root calculator 8a' and an adder 8c are added so that it has no relation to the temperature control system.
This eliminates the loss of adjustment function.

In the above embodiment, the radiation thermometer 5b was provided at the inlet of the heating coil, but if the inlet temperature can be considered constant, the signal from the temperature setting device similar to the temperature setting device 9a can be used. It is also effective to integrate the speed signal with the multiplier 8e.

Incidentally, in the above description, the present invention has been described with respect to heating a solid object such as a metal as a moving object, but it can also be used in the case of heating a liquid or the like while moving a heating coil.

As described above, according to the present invention, the voltage applied to the heating coil is the product of the temperature increase value of the heated material and the moving speed.
Since the temperature is controlled to a value proportional to 0.5 to the first root, the temperature can be heated to the target temperature even if the temperature increase value is changed widely, and the temperature control accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional induction heating device, and FIG. 2 is a block diagram showing an embodiment of the present invention. In the figure, 1 is the material to be heated, 2 is the heating coil,
3 is a heating power supply, 4 is a transformer, 5a and 5b are radiation thermometers, 6 is a speed detector, 8 is a control panel, 8a is a square root calculator, 8b is a regulator, 8c and 8f are adders,
8d is a subtracter, 8e is a multiplier, 9 is an operation panel, 9a
is a temperature setter, 9b is a ratio setter, 9c is a fine difference corrector, and 8g is an index setter. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a device that heats the material to be heated and an induction heating coil while moving them relatively, the voltage applied to the induction heating coil is set to 0.5 to the first root of the product of the temperature increase value of the material to be heated and the moving speed. An induction heating device characterized by controlling to a proportional value.