JPS6360229A - Method for controlling annealing of iron core of electric equipment - Google Patents

Abstract

PURPOSE:To heat up all iron cores to a prescribed temp. range without using a dummy material and to stably and continuously anneal the iron cores by controlling the output of an inverter for heating to the optimum condition in an annealing furnace by the input of means for detecting an annealing rate and position and calculation of time. CONSTITUTION:The top position of the iron cores 1 is detected by an optical or electrical position detecting means 6 near an inlet of a heating coil 2 and the moving speed of the iron cores 1 is measured by a means for detecting the rotating speed of a motor for driving a conveyor 3 or other means. The position where the iron cores 1 pass in the coil 2 is calculated from the above-mentioned speed and time by a microcomputer 7. The output of the ratio determined in relation to the target output of the inverter 9 for heating at the time of the stationary operation when the inside of the furnace is full of the iron cores is gradually applied to the coil 2 when the top iron core 1 arrives at the point L1 to enter the coil 2. The stationary operation is started from the point of the time past the L2 at which the inside of the furnace is full of the iron cores. Conversely, the tail end of the iron core 1 is detected and the output is successively decreased reverse from the above when the inside of the furnace is successively emptied. The individual heating of the iron cores 1 to an adequate temp. is thereby permitted even if the inside of the furnace is not full.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an annealing control method in an induction heating apparatus mainly used for annealing cores of electrical equipment such as small electric motors and small transformers.

BACKGROUND OF THE INVENTION Iron cores for electrical equipment are often subjected to annealing after being punched to improve the efficiency of the equipment.

This annealing is usually called residual stress relief annealing or strain relief annealing, and is annealed at 750°C to 850°C for ~2 hours, and generally takes 10 to 12 hours including all steps such as cooling. It is true. Therefore, various annealing methods using induction heating devices as heating means have been proposed. That is, in JP-A No. 58-104125, the frequency and input power as heating conditions are described in JP-A-59-12371.
No. 9 deals with the relationship between temperature and time as heating conditions, and JP-A-59-143026 deals with annealing equipment. In these conventional induction heating devices,
It is advantageous to use a solenoid type coil with the highest heating efficiency, but when heating the iron core, it is necessary to determine the amount of heat and set the heating inverter output with the entire iron core inside the heating coil. It is being done.

Problems to be Solved by the Invention However, in this method, if a steady output is applied before the inside of the heating coil is full, an appropriate annealing temperature cannot be obtained due to the difference in load. In continuous production annealing equipment, especially when using the induction heating method, the cores are heated individually, so the key to quality stability is how to anneal each core at a uniform temperature. Looking at it, I have to say that I am extremely dissatisfied.

The present invention also solves the above-mentioned drawbacks of the conventional method at the start or end of continuous annealing, by bringing the temperature of the entire core to a predetermined temperature without filling the furnace with so-called dummy material, and preventing the occurrence of core quality problems. , which controls the annealing speed and inverter output.

Means for Solving the Problems In order to overcome the drawbacks of the prior art, the present invention measures the iron core position by means of optical or electrical position detection means near the entrance of the heating coil, and measures the core position within the heating coil by means of electrical speed detection means. By measuring the speed at which the core passes through the heating coil, the position of the core passing through the heating coil is calculated using a microcomputer or the like, and based on the result, the inverter output is immediately controlled by the inverter control means.

Operation In the apparatus of the present invention, for example, when the iron core starts to be continuously annealed, the leading position of the iron core is detected by the position detection means,
The iron core position in the heating coil is calculated from the result of the iron core moving speed obtained by the rotation speed detection means of the conveyor drive motor,
By determining the amount of heat input necessary to raise the temperature to the annealing temperature for the core position and controlling the inverter output,
The iron core is heated to a specified temperature when passing through the heating coil.

Example The present invention will be explained based on examples.

FIG. 1 shows an annealing apparatus of the present invention.

Iron cores 1 are arranged on a chain conveyor 3 and guided into a heating coil 2 to be annealed by induction heating.

First, the conveyor speed is obtained from the pulse signal generator 4 via the frequency counter 5. Normally, the output P of the heating coil inverter 9 when the furnace is full is P=VXK+Q+CXΔT, where P: heating coil inverter output [kwlV:
Annealing conveyor speed [kaku/min] K: Iron core shape/
Coefficient determined by material Q: Heat dissipation [kwl8T] Difference between target annealing temperature and current annealing temperature E°C: Inverter output for heating coil required to raise temperature difference by 1°C [kw]
We have confirmed through experiments that it can be determined by /'C].
K is 2.0-3.0, Q is 30-40. C is 1.0-3
．． It is about 0. If it is close to the target annealing temperature, C×ΔT is 3
As can be seen, the heating coil inverter output becomes a linear function of the conveyor speed when P=VXK+Q, and once the conveyor speed is determined, the target inverter output during steady operation is determined.

Assume that the cores 1 are sequentially introduced into the furnace from a completely empty state. Since the inside of the furnace is exposed to high temperatures, a position detecting means 6 for the iron core is provided at the Lo point at the heating coil inlet, and a microcomputer 7 detects the distance from Lo based on the conveyor speed and time.
Calculate with. When the furnace is empty, the heating inverter output is O, but according to the calculation result, the first core enters the heating coil, and when it reaches one point, the output gradually increases to a predetermined ratio to the target output during steady operation. I'm gaining strength. The relationship between the position of the leading edge of the iron core and the output of the heating coil inverter at this time is shown in FIG. 2(a). This curve was obtained through experiments, and it is thought that it changes depending on the shape of the heating coil, etc.

In this way, the inside of the furnace becomes full, and steady operation is started from the time point 2 is passed. On the other hand, if the core is not fed into the furnace when it is full (and the furnace is empty), the last end of the core is detected at points I and O, and the On the contrary, the output is reduced at a predetermined ratio to the target output for steady operation, as shown in Figure 2 (b).
Shown below.

In this way, each core can be heated to an appropriate temperature even if the furnace is not full. In addition, in Figure 1,
8 is a D/A converter.

Effects of the Invention As described above, in the present invention, the state inside the furnace is estimated by calculating the annealing speed, the input of the position detection means, and the time, and the inverter output for the heating coil is applied to the furthest state inside the annealing furnace. , all the iron cores are heated within the specified temperature range without the use of so-called dummy materials as the furnace goes from empty to full and then empty again, and no defects occur due to under- or over-cut temperatures. , stable annealing is possible continuously.

[Brief explanation of the drawing]

Fig. 1 is a system outline diagram of an annealing apparatus in an embodiment of the present invention, Fig. 2 (a) is a graph of the relationship between the distance from the LO at the beginning of the core and the heating inverter output, and Fig. 2 (b) is a graph of the relationship between the distance from the LO at the beginning of the core and the output from the heating inverter. It is a graph of the relationship between distance from LO and heating inverter output. DESCRIPTION OF SYMBOLS 1... Iron core, 2... Induction heating coil, 4... Pulse signal generator, 6... Position detection means, 7...・Microcomputer, 9
・・・・・・Inverter for heating coil. Name of Agent: Patent Attorney Toshio Nakao

Claims (2)

[Claims] (1) When continuously annealing the core of an electrical device using the induction heating method, the core position is measured using an optical or electrical position detection means near the entrance of the heating coil, and the inside of the heating coil is measured using an electrical speed detection means. Annealing control method for an electrical equipment iron core, in which the position of the iron core passing through a heating coil is calculated by measuring the speed at which the iron core passes, and the output of a heating inverter is controlled based on the result of calculating the amount of heat input to the passing position. . (2) Claim 1 in which the inverter output for any iron core position within the heating coil is controlled by a predetermined function.
Annealing control method for an electrical equipment iron core as described in .