JPH03295210A - Demagnetizing device - Google Patents

Abstract

PURPOSE:To easily and quickly control a direction switching, and also to conduct a demagnetizing operation quickly by a method wherein each contact point of a direction-switching circuit is continuously ON-OFF controlled by a time interval which is decreased gradually. CONSTITUTION:A capacitor 6 is provided between the output terminals of a rectifier 3, and diodes S1, D2, D3 and D4 are parallel-connected to contact points (1)to (4) of a diode switching circuit 7. Also, the diodes D1 to D4 are connected from the side of an electromagnetic coil 4 to a capacitor 6 in such a manner that a forward direction is obtained from the minus (-) terminal to a plus (+) terminal. Accordingly, a direction-changing relay CR1 is continuously switched at the times T12 to T15 which will be determined by the time intervals reduced gradually, the relay CR2 on the powder source side is turned OFF at the time T15 the chucking current at each direction switching time can be reduced gradually without generation of sparks from the contact points 1 to 4, and a demagnetizing operation can also be finishing in a short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a demagnetizing device that demagnetizes a ferromagnetic material that has been magnetized in advance.

(Prior art) For example, in an electromagnetic chuck device that fixes an iron workpiece to the table of a machine tool, a ferromagnetic material provided on the table surface is magnetized to hold the workpiece, and then the workpiece is released from the ferromagnetic material. Magnetism allows the workpiece to be removed from the table surface.

In such an electromagnetic chuck device, it is necessary to appropriately erase residual magnetism, that is, demagnetize it, so as not to leave any magnetism on the workpiece.

By the way, in general, once a magnetic field is applied to a ferromagnetic material, it becomes magnetized and retains magnetism in the object in the form of residual magnetism, but in order to demagnetize this residual magnetism, it is necessary to Simply apply a slightly smaller magnetic field in the opposite direction to the current magnetic field, then apply an even smaller magnetic field in the opposite direction several times, gradually converging the magnetic field to zero.

To control the magnetic field in this way, the current can be gradually reduced while reversing the direction of the current flowing through the electromagnetic coil. The magnitude of the current can be controlled by controlling the voltage, controlling the energizing time, or controlling the voltage and the energizing time by combining both.

However, in the method of controlling the voltage and the method of controlling the voltage and the energization time, the control method is complicated and the device becomes expensive, so a method of controlling the energization time is generally adopted.

FIG. 3 is an explanatory diagram showing an example of a drive circuit of a conventional demagnetizing device used in an electromagnetic chuck device.

In the figure, an AC power source 1 is provided with a rectifier 3 via a contact 2 of a control relay (electromagnetic relay) CR2, and the output of the rectifier 3 is used as a DC power source for a demagnetizing coil (electromagnetic coil) 4.

Between the rectifier 3 and the electromagnetic coil 4, there are four control relay CRI contacts ■, ■, ■.

■ combined in a bridge shape, contacts placed opposite ■,
A direction switching circuit 5 is provided which simultaneously opens or closes ■, ■, and ■, respectively, and input points A and B of the circuit 5.
is connected to the rectifier 3, and output points C and D are connected to the electromagnetic coil 4.

FIG. 4 is a timing chart showing the control method of the demagnetizing drive circuit. In FIG. 4, each chart shows, in order from the top, the operating state of the relay CRI of the direction switching circuit 5,
It shows the operating state of relay CR2 connected to AC power supply 1, the changing state of (chuck voltage) appearing at the connection point (C, D) of electromagnetic coil 4, and the changing state of the current (chuck current) flowing through electromagnetic coil 4. There is.

In FIG. 4, first, before the start of demagnetization work, relay CRI is turned off, and rectifier 3 is connected to electromagnetic coil 4 via contacts (1) and (2) of relay CRI.

Therefore, when demagnetizing work is started and at time T, -72, relay CR2 on the power supply side is turned on and contact 2 is closed, rectifier 3
A DC voltage appears at the output end of the electromagnetic coil 4, and the output voltage is applied as a chucking voltage to both ends of the electromagnetic coil 4. A chucking current I that gradually increases is passed through the electromagnetic coil 4, and the magnetization of the ferromagnetic material (not shown) is reversed. be done.

When relay CR2 is turned off at time T2 and power supply to rectifier 3 is cut off, chuck current I gradually becomes smaller.
It eventually becomes zero (0) after time tl.

Therefore, from time T2 when relay CR2 is turned off, time t
From time T3 after one elapsed time to time T6 thereafter, relay CRI is turned on, contacts ■ and ■ are opened, and contacts ■ and ■
is closed, and after time t2, relay CR2 on the power supply side is closed for time T.
When turned on up to 5, a current flows through the electromagnetic coil 4 in the opposite direction to the previous current. Here, if the energization time T, -74 is made shorter than the previous energization time T2-T, the chuck current becomes smaller than the previous one, and the magnetism of the ferromagnetic material (not shown) becomes smaller.

Time t1 is a waiting time until the chucking current is attenuated to zero to prevent sparking from the contacts of relay CRI. Further, time t2 is a waiting time for preventing relay interference.

From time T7 to T8, the electromagnetic coil 4
Next, a chuck current is sequentially passed in the opposite direction from Tlo to T11. Here, the subsequent energization time is made sequentially smaller than the previous energization time, and a gradually smaller magnetic field appears in the electromagnetic coil 4 alternately, and the ferromagnetic material (not shown) is eventually demagnetized.

(Problem to be Solved by the Invention) However, in the conventional demagnetizing device using the energization time control method as described above, after the contact of the direction switching circuit 5 is opened, the contact opening/closing operation for the next direction is not possible. Since the process must be delayed by 9 hours t1 until the chuck current becomes zero and by a waiting time t2 to prevent interference between relays, the direction switching operation takes time, which complicates the sequence and makes it difficult to perform sufficient escape. There was a problem in that it took a considerable amount of time to perform magnetization.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a demagnetizing device using the energization time control method, which can easily and quickly perform direction switching control and can quickly perform demagnetizing work.

[Structure of the Invention] (Means for Solving the Problems) The present invention to solve the above problems repeatedly generates magnetic fields in the forward and reverse directions in the electromagnetic coil by repeatedly supplying current in the forward and reverse directions to the electromagnetic coil. , in a demagnetizing device that demagnetizes a pre-magnetized ferromagnetic material, a DC voltage source that generates a DC voltage, a capacitor connected to the DC voltage source, and a capacitor disposed between the capacitor and the electromagnetic coil. a direction switching circuit that switches the connection direction of both members by the opening and closing operation of contacts arranged in a bridge shape;
and a diode that is built in parallel to each contact of the circuit and circulates a current caused by self-induction of the electromagnetic coil generated in conjunction with the opening operation of the contact to the capacitor, forming a demagnetizing drive circuit, The present invention is characterized in that it includes a control circuit that alternately generates a gradually decreasing magnetic field from the electromagnetic coil by continuously controlling the opening and closing of each contact of the switching circuit in a gradually decreasing time duct.

(Function) In the demagnetizing device of the present invention, since the opening/closing control of each contact of the direction switching circuit 5 is performed continuously using a gradually decreasing time duct, the waiting time (tl+t2) shown in the conventional example is unnecessary. This makes sequence processing easier and increases processing speed.

At this time, in each switching operation, a current generated by self-induction of the electromagnetic coil is made to flow back into the capacitor and also to flow from the opposite direction of the electromagnetic coil, so that a gradually decreasing current is caused to alternately flow through the electromagnetic coil. Since it will alternately generate a magnetic field that gradually decreases from
The direction switching operation becomes smooth and there is no waste in power consumption.

(Embodiment) FIG. 1 is an explanatory diagram showing the configuration of a demagnetizing drive circuit of a demagnetizing device according to an embodiment of the present invention. Components shown with the same reference numerals as in FIG. 3 are components that perform the same functions as those in FIG.

The demagnetizing drive circuit of this example is different from the one shown in FIG.
2. The only difference is that D3 and Da are connected in parallel.

The capacitor 6 has a capacity sufficient to absorb the surge current caused by self-induction of the electromagnetic coil 4.

Moreover, each diode D,, D2. D, , D are connected in the forward direction from the electromagnetic coil 4 side to the capacitor 6 and from the minus (-) terminal to the plus (+) terminal of the capacitor 6.

FIG. 2 is a timing chart showing a control method of the demagnetizing drive circuit. From top to bottom, the operating status of relay ~ CR1, the operating status of relay CR2, the changing status of chuck voltage,
It shows the changing state of the chuck current.

First, when relay CR2 is turned on at time T1 and DC voltage is output from rectifier 3, the chuck current gradually increases toward time T2. The operation is the same as the operation from time T1 to time T2 in the conventional example shown in FIG.

However, in this example, diodes D8 . D2, D9. D4
Since a capacitor 6 is provided at the output end of the rectifier 3, the surge current of the electromagnetic coil 4 can be absorbed by the capacitor 6, and the relay CRI can be operated while the relay CR2 is kept on.

Therefore, in this example, the time T, which is determined by the gradually decreasing time duct, 2. T, 3. T, 4. At time T2, the direction switching relay CRI is continuously switched at time T2. By turning off relay CR2 on the power supply side, it is possible to gradually reduce the chuck current at each direction switching time without causing sparks at each contact, and the demagnetization work can be completed in a short time. be able to.

As described above, in this example, the relay CRI of the direction switching circuit can be continuously switched while the relay CR2 on the power supply side is kept on, so the control circuit can be simplified.
Moreover, the demagnetization time can be considerably shortened.

Further, even if the relay CRI malfunctions due to noise or the like, each contact does not spark, so the device life is extended and the device reliability is improved.

The present invention is not limited to the above-mentioned embodiments, but can be implemented in any appropriate manner by making appropriate design changes.

[Effects of the Invention] As described above, since the present invention is a demagnetizing device as described in the claims, direction switching control can be performed continuously, and the demagnetizing time can be considerably shortened. . Also,
Since direction switching control only requires turning on and off one relay, the control circuit becomes extremely simple. Furthermore, since no sparks are generated from each contact, the life of the device is extended and reliability is improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a demagnetizing drive circuit according to an embodiment of the present invention, Fig. 2 is a timing chart showing its control method, Fig. 3 is an explanatory diagram of a conventional demagnetizing drive circuit, and Fig. 4 is an explanatory diagram of a demagnetizing drive circuit according to an embodiment of the present invention. 1 is an evening chart showing the control method. 1... AC power supply 3... Rectifier 4... Electromagnetic coil 6... Capacitor 7... Direction switching circuit CRI, CR2... Electromagnetic relay

Claims (1)

[Scope of Claims] In a demagnetizing device that demagnetizes a ferromagnetic material that has been magnetized in advance by repeatedly generating a magnetic field in the forward and reverse directions in the electromagnetic coil by repeatedly applying current in the forward and reverse directions to the electromagnetic coil. , a DC voltage source that generates a DC voltage, a capacitor connected to the DC voltage source, and a bridge-shaped contact arranged between the capacitor and the electromagnetic coil, which connects both members by opening and closing operations. a direction switching circuit that switches the direction;
and a diode that is built in parallel to each contact of the circuit and circulates a current caused by self-induction of the electromagnetic coil generated in conjunction with the opening operation of the contact to the capacitor, forming a demagnetizing drive circuit, A demagnetizing device characterized by comprising a control circuit that alternately generates a gradually decreasing magnetic field from the electromagnetic coil by continuously controlling the opening and closing of each contact of the switching circuit in a duct for a gradually decreasing time.