JPH0130267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention can be carried out when the shape of the object to be heated makes it easy to surround the outer periphery with a coil, such as a shock absorber for an automobile. The present invention relates to a suitable electromagnetic induction heating device.

(Prior Art) Electromagnetic induction heating devices have conventionally been widely used as heat sources for cooking appliances and the like. In the case of such cookers, a metal heated object was placed in a magnetic field in which the direction of magnetic lines of force alternated, and the food to be heat-processed was placed on top of it, so naturally the heated metal object (Food) had a structure in which it received heat through a metal heating object (generally a metal plate).

By the way, most of the automobile parts manufactured from metal are painted for the purpose of preventing rust, but in this painting process, the quality of drying is an issue. This is because the paint is likely to peel off if it is poorly dried. Therefore, in the past, sufficient drying time was taken to prevent insufficient drying, but if the shape of the object to be coated is complex, it may still not be possible to dry the hidden areas sufficiently. Ta.

(Problems to be Solved by Heat Generation) The present invention has been developed to directly heat objects with complex shapes, such as the above-mentioned automobile parts, using an electromagnetic induction heating method. In addition to this, it is possible to securely control the energization of the magnetic force generating coil, monitor the operating status of the energization control circuit, and stop the energization and issue an alarm when an abnormality occurs.

(Means for Solving the Problems) In order to solve the above problems, that is, as a means to achieve the object, the present invention uses a GTO thyristor as a current control element for a magnetic force generating coil, and also uses a GTO thyristor in a power supply circuit. The detection side of a meter relay for current detection that detects the current flowing in the power supply circuit is connected, and the detection side of a meter relay for voltage detection is connected to a control circuit that controls the oscillation circuit that controls the GTO thyristor. Connecting the output side of the meter relay to the energization control element and alarm circuit,
Both meter relays detect current and voltage, and when the current and voltage values respectively exceed the set values of both meter relays, the control circuit immediately stops the energization, and at the same time a warning is displayed on the display. The configuration is such that it displays the following information.

(Function) With this configuration, when compared with drying using conventional infrared drying lamps, etc., the generally known difference between radiant heat conduction and electromagnetic induction heating of conventional infrared drying lamps will be improved. Due to the difference in heating efficiency and the provision of a monitoring and abnormality detection circuit using a meter relay, drying can be carried out quickly and reliably, and abnormal situations can be quickly detected.

(Embodiment) Next, an embodiment of the present invention will be explained with reference to the drawings. Reference numerals 1 and 2 are power supply terminals, and
It is powered by 100 volts. The power supply terminals 1 and 2 are connected to contacts 3 and 4 of an earth leakage breaker (or circuit protector), a current transformer 5, a resistor 6, output contacts 8 and 9 of a control circuit 7 to be described later, a capacitor 10, a diode 11, 1
2, 13, 14, chiyoke coil 15, capacitor 16, magnetic force generating coil 17, capacitor 18,
A GTO thyristor 19 and a diode 20 are connected as shown. As is well known, the GTO thyristor 19 has both the self-conduction function of a thyristor and the self-cutting ability of a transistor, and by being connected to this part,
The power supply to the magnetic force generating coil 17 is controlled.

A meter relay 21 for detecting current is connected in parallel to the resistor 6, and a meter relay 22 for detecting voltage, which will be described later, is connected to the control circuit 7.
It controls the output contacts 8 and 9 of the control circuit 7 and displays an alarm. Output side of resistor 6 and contact 4
A transformer 26 is connected to the output side of the transformer 26 via a fuse 23 and choke coils 24 and 25. 27 is a voltmeter. A low voltage power supply circuit 28 is connected to the output side of the transformer 26, and supplies power to the control circuit 7, an oscillation circuit (including a drive circuit) 29, and a monitor circuit 30.

The control circuit 7 controls the output voltage of the current transformer 5, the output voltage generated between the poles of the capacitor 18 to the magnetic force generating coil 17, and the magnetic force generating coil 1.
7 receives the output voltage of the temperature sensor 31 provided near the meter relay 2 as an input signal.
1 and 22, and outputs the heating time, heating temperature, output voltage, output current, and control status to the monitor circuit 30, and also displays whether the heating cycle step status is good or not. 32
This is what is output to. Note that a setting circuit 33 is connected to the monitor circuit 30 so that settings such as heating output and heating time can be made.

The control of the GTO thyristor 19 is performed by the oscillation circuit 29.
It is carried out by. This oscillation circuit 29 includes a drive circuit as described above. An astable multivibrator circuit is used as the oscillation circuit, and a circuit 33 sets the width of the output pulse wave.
GTO thyristor 19 by changing the operation of
The current supply time to the tank circuit formed by the magnetic force generating coil 17 and the capacitor 18 is controlled by changing the current supply time. The setting circuit 33 is operated not only to change the heating time, but also to change the heating time depending on the condition of the object to be heated.
It is also possible to gradually increase the output voltage from the start of heating to the middle, reach the maximum at the middle, and then gradually weaken it towards the end of heating. Therefore, optimum heating conditions can be achieved.

Next, the effect will be explained. When a voltage is applied to the power supply terminals 1 and 2, this voltage is rectified and smoothed by a rectifying and smoothing circuit including a capacitor 10, diodes 11, 12, 13, and 14, a chiyoke coil 15, and a capacitor 16. is applied to the tank circuit formed by 18. On the other hand, this tank circuit is supplied with its output power from the control circuit and resonates. By manufacturing the magnetic force generating coil 17 in a shape that surrounds the outer periphery of the object to be heated, the object to be heated (not shown) can be heated.
will be heated. While monitoring the monitor circuit 30 and paying attention to the warning on the display device 32,
The oscillation circuit 29 is activated by operating the setting circuit 33.
By controlling , the energization time to the GTO thyristor 19 changes, so the heating situation can be changed. When acting in this manner, the meter relays 21 and 22 monitor the current and voltage, and when the set value is exceeded, the control circuit 7 immediately stops the current supply, and at the same time a warning is displayed on the display device 32. Become. As described above, in the circuit of the present invention, the detection side of a meter relay for detecting current that detects the current flowing through this power supply circuit is connected to the power supply circuit, and the control circuit that controls the oscillation circuit that controls the GTO thyristor is connected to the power supply circuit. Since the detection side of a meter relay for voltage detection is connected to the circuit, both meter relays can detect changes in the current and voltage values that always occur when an abnormal situation occurs that can occur at any time. This will allow us to respond quickly. Moreover, unlike other means, meter relays have a simple structure, are easy to handle, and have very few failures, so they can be said to be the most suitable device for this purpose. on the other hand,
As is well known, a GTO thyristor has properties intermediate between a transistor and a thyristor.
This allows the circuit to be simplified. By employing this element, the present invention makes good use of the unique effects of this element, and has succeeded in obtaining a simple and economical electromagnetic induction heating circuit.

(Effects of the Invention) Since the present invention is configured and operates as described above, the shape of the object to be heated is such that the outer periphery thereof can be easily surrounded by a coil, such as a shock absorber of an automobile. In this case, the entire area can be heated evenly and efficiently.
Therefore, if this heating is for drying after painting, the inner part will also be thoroughly dried.

[Brief explanation of drawings]

The figure is a circuit diagram of an embodiment of the present invention. 7... Control circuit, 17... Magnetic force generating coil, 18...
Capacitor, 19...GTO thyristor, 21,2
2...meter relay, 29...oscillation circuit, 32...display device, 33...setting circuit.

Claims (1)

[Claims] 1 G. as an energization control element to the magnetic force generating coil.
In addition to using TO thyristors, in the power supply circuit,
A detection side of a meter relay for current detection that detects the current flowing in the power supply circuit is connected, and a detection side of a meter relay for voltage detection is connected to a control circuit that controls an oscillation circuit that controls the GTO thyristor. The output sides of these meter relays are connected to the energization control element and the alarm circuit, and both meter relays are made to detect current and voltage, respectively, and when the current and voltage values exceed the set values of both meter relays, respectively. An electromagnetic induction heating device characterized in that, in some cases, the control circuit immediately stops energization, and at the same time a warning is displayed on a display device.