JPH10294215A - Electromagnet apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a count of switching transistors and enable omission of three insulated d.c. power sources. SOLUTION: An electromagnet 2 has an attraction coil 1 and a demagnetization coil 10 wound in opposite directions. A power supply circuit 3 connected to an a.c. power source 11 is provided with an attraction coil-switching transistor 34 connected in series to the attraction coil 1 and a demagnetization coil- switching transistor 37 connected in series to the demagnetization coil 10. A control circuit part 49 is connected at an input terminal of the transistor 37. The control circuit part 49 turns on the transistor 37 from a time point when the supply of an exciting current i1 to the attraction coil 1 is stopped, and turns off the transistor 37 at a time point when an exciting current i2 of the demagnetization coil 10 reaches a current value Ir whereby a remnant magnetization by the attraction coil 1 can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnet apparatus which can be used as a magnet chuck, an electromagnetic clutch or the like, and which has a function of removing residual magnetism.

[0002]

2. Description of the Related Art As is well known, a magnet chuck is
The work is attracted by energizing the attraction coil of the electromagnet to excite the electromagnet, and the work is released by stopping the energization to the attraction coil.
It is difficult to easily detach the work due to the residual magnetism simply by stopping the energization of the attracting coil. Therefore, various measures for removing the residual magnetism have been conventionally taken.

FIG. 6 shows a first conventional example of a magnet chuck, and FIG. 8 shows a second conventional example.

As shown in FIG. 6, the first conventional example includes an electromagnet 2A having an attraction coil 1A, and a power supply circuit 3A for supplying an exciting current to the attraction coil 1A.

The power supply circuit 3 A includes a commercially available power module 5 connected to a DC power supply 4.

The power module 5 has an H-bridge circuit 6, and output terminals 6a and 6b of the H-bridge circuit 6 are connected to the attraction coil 1A.

The input terminals of the four switching transistors 61, 62, 63, 64 constituting the H-bridge circuit 6 correspond to the pre-drive circuits D on a one-to-one basis.
1, D2, D3 and D4 are connected.

A switch SW for sending a command signal SIG is connected to the input terminals of the predrive circuits D1 and D4, and the changeover switch SW is connected to the input terminals of the other predrive circuits D2 and D3 via a timer circuit T. SW is connected.

The timer circuit T is configured to drive the pre-drive circuits D2 and D3 only for a predetermined time from the time when the changeover switch SW is turned on to the B side.

The pre-drive circuit D1 is connected to an insulated DC power supply S1 dedicated to the insulated pre-drive circuit D1 which converts the commercial power 7 into DC power and supplies the DC power to the pre-drive circuit D1. The pre-drive circuits D2, D4 and the timer circuit T are also common to the pre-drive circuits D2, D4 and the timer circuit T for converting the commercial power supply 7 into DC power and supplying the DC power to the pre-drive circuits D2, D4 and the timer circuit T. The insulated DC power supply S2 is connected. The pre-drive circuit D3 is also connected to an insulated DC power supply S3 dedicated to the insulated pre-drive circuit D3, which also converts the commercial power 7 into DC power and supplies the DC power to the pre-drive circuit D3.

In the first conventional example configured as described above, in order to attract the workpiece W by the electromagnet 2A, as shown in FIG.
Turn on the side. When the changeover switch SW is turned on to the A side, the pre-drive circuits D1 and D4 operate, the pair of switching transistors 61 and 64 are turned on, and the exciting current i flows through the attracting coil 1A as shown in FIG.
Can be excited to attract the work W.

Thereafter, in order to separate the work W from the electromagnet 2A, as shown in FIG. 7, the changeover switch SW is switched from the A side to the B side by the command signal SIG, the A side is turned off, and the B side is turned on. When the A side is turned off, the pre-drive circuits D1 and D4 stop operating, the switching transistors 61 and 64 are turned off, and the exciting current i flows through the feedback diodes 65 and 66 and gradually decreases as shown in FIG. Go on. On the other hand, when the changeover switch SW is turned on to the B side, the timer circuit T operates and the pre-drive circuit D
2, D3 is operated, and another pair of switching transistors 62 and 63 are turned on, and as shown in FIG. 7, an exciting current i in the opposite direction to the attracting coil 1A, that is, an exciting current i for removing the residual magnetism. Will flow. And
When a predetermined time set by the timer circuit T has elapsed, the pre-drive circuits D2 and D3 stop operating, the switching transistors 62 and 63 are turned off, and the exciting current i stops flowing. Here, the magnitude of the exciting current i at the time point when the predetermined time has elapsed is set to a value (-Ir) capable of removing the residual magnetism of the electromagnet 2A.
This current value (−Ir) is set to a value (≒ −I / 10) that is about 1/10 of the steady value I of the forward exciting current i of the attracting coil 1A from the BH curve shown in FIG. ing.

As shown in FIG. 8, the second conventional example has an electromagnet 2A having an attracting coil 1A, as in the first conventional example.
Power supply circuit 3 for supplying exciting current i to attracting coil 1A
B, the power supply circuit 3B includes a commercially available power module 5 connected to the DC power supply 4, a pre-drive circuit D1,
D2, D3, D4, a changeover switch SW, a DC power supply S1 dedicated to the insulated pre-drive circuit D1 for converting the commercial power supply 7 into DC power, a DC power supply S2 dedicated to the insulated pre-drive circuits D2, D4, And a DC power supply S3 dedicated to the insulated pre-drive circuit D3. However, the second conventional example does not include the timer circuit T as in the first conventional example, and has a current limiting resistor 8 and a diode 9 that are not provided in the first conventional example. A circuit is externally provided between the output terminal 6b of the H-bridge circuit 6 and the attraction coil 1A.

In the second conventional example configured as described above, to attract the work W by the electromagnet 2A, as shown in FIG. 9, the changeover switch SW is set to A by the command signal SIG.
Turn on the side. When the changeover switch SW is turned on to the A side, the pre-drive circuits D1 and D4 operate, the pair of switching transistors 61 and 64 are turned on, and the exciting current i flows through the attracting coil 1A as shown in FIG.
Can be excited to attract the work W.

Thereafter, in order to separate the work W from the electromagnet 2A, as shown in FIG. 9, the changeover switch SW is switched from the A side to the B side by the command signal SIG, the A side is turned off, and the B side is turned on. When the A side is turned off, the pre-drive circuits D1 and D4 stop operating, and the switching transistors 61 and 64 are turned off. As shown in FIG. 9, the exciting current i flows through the feedback diodes 65 and 66 and gradually decreases. Go on. On the other hand, when the changeover switch SW is turned on to the B side, another pair of switching transistors 62 and 63 are turned on, and as shown in FIG.
An exciting current i in the opposite direction, ie, an exciting current i for removing residual magnetism, flows through A. The exciting current i in the opposite direction is limited by the current limiting resistor 8 to a value (-Ir) from which residual magnetism can be removed. This current value (-Ir) is the same as that of the first conventional example described above.
A is about 1/10 of the steady state value I of the forward exciting current i of A.
It is set to a value of the order (≒ −I / 10).

[0016]

However, each of the first and second prior arts described above uses a commercially available power module having four switching transistors and also uses three insulated power modules. Since a DC power supply is used, there is a problem that a relatively large space is required and the cost is high.

The present invention solves the above-mentioned problems and reduces the number of switching transistors and eliminates three insulated DC power supplies, thereby reducing the space and cost. The purpose is to provide.

[0018]

An electromagnet apparatus according to the present invention comprises:
Claims 1. An electromagnet having an attraction coil and a degaussing coil wound in opposite directions, and a power supply circuit connected to an AC power supply or a DC power supply, wherein an excitation current is supplied to the attraction coil. And a power supply circuit for supplying an excitation current to the degaussing coil for removing residual magnetism by the attraction coil immediately after the supply of the excitation current to the attraction coil is stopped.

According to a second aspect of the present invention, in the electromagnet device according to the first aspect, the power supply circuit includes a switching transistor for the attraction coil connected in series to the attraction coil, and a switching transistor connected to the degaussing coil in series. And a switching transistor for the degaussing coil connected thereto.

According to a third aspect of the present invention, in the electromagnet apparatus according to the second aspect, a control circuit is connected to an input terminal of the switching transistor for the degaussing coil. The switching transistor for the degaussing coil is turned on at the time when the supply of the exciting current to the attracting coil is stopped, and then, when the exciting current of the degaussing coil reaches a current value at which the residual magnetism by the attracting coil can be removed, the degaussing coil is turned off. And a switching transistor for turning off the switching transistor.

According to a fourth aspect of the present invention, in the second aspect, the control circuit is connected to the input terminal of the switching transistor for the degaussing coil, and the current limiting resistor is connected to the output terminal. The control circuit unit is configured to turn on the switching transistor for the degaussing coil from the time when the supply of the exciting current to the attracting coil is stopped, while the current limiting resistor is configured to switch the switching transistor for the degaussing coil. When turned on, the excitation current of the degaussing coil is limited to a current value capable of removing residual magnetism by the attraction coil.

[0022]

According to the first aspect of the present invention, in addition to the attraction coil, a demagnetizing coil is provided for the purpose of removing residual magnetism by the attraction coil, and is connected to an AC power supply or a DC power supply. The power supply circuit supplies an exciting current to the attracting coil, and supplies an exciting current to the degaussing coil to remove residual magnetism by the attracting coil immediately after the supply of the exciting current to the attracting coil is stopped.

Therefore, by using one AC power supply or one DC power supply, three insulated DC power supplies according to the conventional example can be omitted, and instead of using four switching transistors according to the conventional example, For example, as described in claim 2, by using two switching transistors consisting of a switching transistor for the attracting coil connected in series to the attracting coil and a switching transistor for the degaussing coil connected in series to the degaussing coil, The number of switching transistors used can be reduced, so that a small space and low cost can be achieved.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a magnet chuck as an electromagnet device according to one embodiment, and FIG. 2 is a configuration diagram of a power supply circuit in the magnet chuck.

The magnet chuck according to the present embodiment includes an electromagnet 2 for attracting and releasing a workpiece W.
A degaussing coil 10 is provided in addition to the attracting coil 1, and the attracting coil 1 and the degaussing coil 10 are wound in opposite directions.

Here, the number of turns N ₂ of the degaussing coil 10 is extremely small, which is about 1/10 of the number of turns N ₁ of the attraction coil 1. Therefore, the provision of the degaussing coil 10 causes the electromagnet 2 to be enlarged. Almost no defects occur.

That is, as shown by the BH curve in FIG.
The magnetic field H to be generated by the degaussing coil 10 in order to remove the residual magnetism caused by the attraction coil 1 is about 1/10 of the magnetic field H generated by the attraction coil 1. Therefore, when the exciting current i ₂ flowing through the degaussing coil 10 is set to be equal to the exciting current i ₁ flowing through the attracting coil 1, the number of turns N ₂ of the degaussing coil 10 is about 1/10 of the number of turns N ₁ of the exciting coil 1. Value (≒
By setting the N _1/10), it is possible to remove the residual magnetism by the suction coil 1. Therefore, the number of turns (N ₁ + N ₂ ) of the electromagnet 2 as a whole due to the provision of the degaussing coil 10 is only slightly increased as compared with the number of turns N ₁ of the attraction coil 1 alone, and the electromagnet 2 is not enlarged.

Each of the attracting coil 1 and the degaussing coil 10 has
Exciting current i in coils 1 and 10₁ , I _Two Supply power times
Road 3 is connected.

The power supply circuit 3 is connected to an AC power supply (commercial power supply) or a DC power supply (AC power supply 11 in this embodiment). Further, a switch 12 that outputs a command signal SIG to the power supply circuit 3 is connected to the power supply circuit 3.

As shown in FIG. 2, the power supply circuit 3 includes a bridge circuit 31 for performing full-wave rectification on the AC power supply 11.

Between the positive output terminal 31a and the negative output terminal 31b of the bridge circuit 31, a series circuit of a reverse current preventing diode 32 and a smoothing capacitor 33 is connected.

The positive output terminal 3 of the bridge circuit 31
A series circuit of the attracting coil 1 and the attracting coil switching transistor 34 is connected between 1a and the negative output terminal 31b. A flywheel diode 35 is connected to the attraction coil 1 in series.

Further, a demagnetizing coil 1 is provided between the positive output terminal 31a and the negative output terminal 31b of the bridge circuit 31.
A series circuit of 0, a variable resistor 36, and a demagnetizing coil switching transistor 37 is connected. Degaussing coil 10
, A flywheel diode 38 is connected in series.

One contact 12 a of the switch 12 is connected to the positive terminal 33 a of the smoothing capacitor 33.

The other contact 12 b of the switch 12 is connected via a resistor 39 to the base of the attracting coil switching transistor 34. A resistor 40 is connected between the base and the emitter of the attraction coil switching transistor 34.

The positive terminal 33 of the smoothing capacitor 33
The base of the switching transistor 37 for the degaussing coil is connected to a through a series circuit of a variable resistor 41 and a capacitor 42. A parallel circuit of a variable resistor 43 and a discharge diode 44 is connected between the base and the emitter of the demagnetizing coil switching transistor 37.

An auxiliary switching transistor 46 is connected between a connection point 45 between the variable resistor 41 and the capacitor 42 and a negative output terminal 31b of the bridge circuit 31. The base of the auxiliary switching transistor 46 is connected to the other contact 12b of the switch 12 through a resistor 47.
, And a resistor 48 is connected between the base and the emitter.

Next, the operation of the magnet chuck configured as described above will be described with reference to FIGS. 3 and 4.

First, the AC power supply 11 is turned on with the switch 12 turned off, full-wave rectified by the bridge circuit 31 and the smoothing capacitor 3
Charge to 3.

[0041] After that, when the adsorbing workpiece W to the electromagnet 2, turning on the switch 12 at time t _0.

[0042] When the switch 12 is turned on, the voltage of the positive terminal 33a of the smoothing capacitor 33 is applied to the base side of the suction coil switching transistor 34, switching transistor 34 is turned on, the steady value I ₁ to the suction coil 1 exciting current i ₁ flows, the electromagnet 2 is excited, the electromagnet 2 will be able to adsorb the workpiece W (see FIGS. 3 and 4).

When the switch 12 is turned on, the voltage of the positive terminal 33a of the smoothing capacitor 33 is applied to the base of the auxiliary switching transistor 46, and the switching transistor 46 is turned on. Therefore, the switching transistor 37 for the degaussing coil is kept in the off state, and the exciting current i ₂ does not flow through the degaussing coil 10.

[0044] After adsorbing the workpiece W to the electromagnet 2, when leaving the workpiece W from the electromagnet 2, at time t ₁ for switching the switch 12 from ON to OFF.

When the switch 12 is turned off, the attracting coil switching transistor 34 that has been turned on is switched off, and the current due to the induced energy of the attracting coil 1 flows through the flywheel diode 35. Exciting current i flowing through coil 1
₁ gradually decreases and finally becomes zero (see FIGS. 3 and 4).

When the switch 12 is turned off, the auxiliary switching transistor 46 which has been turned on is switched off, and the variable resistor 41 and the capacitor 4 are turned off.
Switching transistor 37 for demagnetizing coil via 2
As a result, the demagnetizing coil switching transistor 37 switches from off to on, and the exciting current i ₂ flows through the degaussing coil 10.

Here, the ON time of the demagnetizing coil switching transistor 37 is determined by the capacitance of the capacitor 42 and the resistance values of the variable resistors 41 and 43.
That is, when the resistance values of the variable resistors 41 and 43 are set to fixed values, the on-time increases as the capacitance of the capacitor 42 increases, and the resistance value of the variable resistor 41 and the capacitance of the capacitor 42 increase. When the capacitance is set to a fixed value, the ON time becomes longer as the resistance value of the variable resistor 43 increases, and when the resistance value of the variable resistor 43 and the capacitance of the capacitor 42 are set to fixed values, The ON time becomes longer as the resistance value of the variable resistor 41 increases.

On the other hand, the exciting current i flowing through the degaussing coil 10
Steady value I ₂ of ₂ is determined by the resistance of the variable resistor 36. In other words, the stationary value I ₂ of the exciting current i ₂ is
It decreases as the resistance value of the variable resistor 36 increases.

The waveform of the exciting current i ₂ shown in FIG. 3 is based on the above-described circuit design conditions, with the ON time T _on of the demagnetizing coil switching transistor 37 set to a relatively short time, and the demagnetizing coil This corresponds to a waveform when the steady value I ₂ of the ten exciting currents i ₂ is set to a relatively large current value (≒ 10I ₁ ). In the waveform of the exciting current i ₂ shown in FIG. 3, the exciting current value Ir at the time point t ₂ at which the demagnetizing coil switching transistor 37 switches from on to off is a current value capable of removing the residual magnetism by the attracting coil 1. (≒ I ₁ ).

On the other hand, the exciting current i shown in FIG._Two Waveform
Is also based on the above circuit design conditions.
ON time T of the switching transistor 37 for il_onTo
Set to a relatively long time and the excitation current i_Two Steady-state value of
I_Two With a relatively small current value (≒ I₁ ) When set to
Corresponds to the waveform. Then, the exciting current i shown in FIG.
_Two In the waveform of
Time t at which the star 37 switches from on to off_Two To
Of the exciting current Ir in the steady state I of the exciting current i2_Two so
Yes, current value that can remove residual magnetism by adsorption coil 1
(≒ I₁ ) Is set to

As described above, the magnet chuck according to the present embodiment includes the electromagnet 2 having the attracting coil 1 and the degaussing coil 10 wound in opposite directions, and the AC power source 1.
1 or a power supply circuit 3 connected to a DC power supply, which supplies an exciting current i ₁ to the attracting coil 1 and immediately stops supplying the exciting current i _{1 to} the attracting coil 1 with respect to the degaussing coil 10. characterized in that it comprises a power supply circuit 3 for supplying an excitation current i ₂ for removing residual magnetism by 1.

The power supply circuit 3 includes a switching transistor 34 for the attraction coil connected in series to the attraction coil 1.
And a demagnetizing coil switching transistor 37 connected in series to the demagnetizing coil 10.

A variable resistor 41 and a capacitor 42 are connected to the input terminal of the demagnetizing coil switching transistor 37.
A variable resistor 43 and a control circuit unit 49 (FIG. 2) is connected, the control circuit unit 49 turns on the switching transistor 37 for degaussing coil from supply stop time of the excitation current i ₁ with respect to the suction coil 1, Thereafter, at a time point t ₂ (FIG. 3) when the exciting current i ₂ of the degaussing coil 10 reaches a current value Ir at which the residual magnetism by the attraction coil 1 can be removed, the switching transistor 37 for the degaussing coil is turned off. Features.

A current limiting resistor comprising a variable resistor 36 is connected to the output terminal of the demagnetizing coil switching transistor 37. The current limiting resistor 36 is demagnetized when the demagnetizing coil switching transistor 37 is turned on. characterized in that it is configured the exciting current i ₂ of the coil 10 to limit the residual magnetism by the suction coil 1 enables current value Ir removed (FIG. 4).

Therefore, according to the magnet chuck of this embodiment, by using one AC power supply 11 or DC power supply, the three insulated DC power supplies according to the conventional example can be omitted, and the conventional example can be omitted. Instead of using the four switching transistors, two switching transistors 34 and 37, which are composed of an attracting coil switching transistor 34 connected in series to the attracting coil 1 and a demagnetizing coil switching transistor 37 connected in series to the degaussing coil 10, are used. By using at least, the number of switching transistors to be used can be reduced, so that a small space and low cost can be achieved.

As described above, since the number of turns of the demagnetizing coil 10 is extremely small, about 1/10 of the number of turns of the attraction coil 1, the provision of the demagnetizing coil 10 causes an increase in the size of the electromagnet 2. Almost no defects occur.

Although the above-described embodiment is an example of a magnet chuck, the present invention is not limited to only a magnet chuck, and it is necessary to remove residual magnetism such as an electromagnetic clutch. It can be widely applied to certain electromagnet devices.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a magnet chuck as an electromagnet device according to one embodiment.

FIG. 2 is a configuration diagram of a power supply circuit in the magnet chuck.

FIG. 3 is a waveform chart showing a first operation example.

FIG. 4 is a waveform chart showing a second operation example.

FIG. 5 is a BH curve diagram.

FIG. 6 is a configuration diagram of a magnet chuck according to a first conventional example.

FIG. 7 is a waveform chart showing the operation of the magnet chuck.

FIG. 8 is a configuration diagram of a magnet chuck according to a second conventional example.

FIG. 9 is a waveform chart showing the operation of the magnet chuck.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 attracting coil 2 electromagnet 3 power supply circuit 34 attracting coil switching transistor 36 variable resistor (current limiting resistor) 37 demagnetizing coil switching transistor 41, 42, 43 control circuit unit 10 demagnetizing coil 11 AC power supply

Claims (4)

[Claims] 1. An electromagnet having an attracting coil and a degaussing coil wound in opposite directions, and a power supply circuit connected to an AC power supply or a DC power supply,
A power supply circuit for supplying an exciting current to the attracting coil and supplying an exciting current to the degaussing coil for removing residual magnetism by the attracting coil immediately after the supply of the exciting current to the attracting coil is stopped. An electromagnet device, characterized in that: 2. The attracting coil switching transistor connected in series to the attracting coil;
2. A switching transistor for a degaussing coil connected in series to the degaussing coil.
An electromagnet device according to claim 1. 3. A control circuit unit is connected to an input terminal of the switching transistor for the degaussing coil, and the control circuit unit turns on the switching transistor for the degaussing coil from the time when supply of the exciting current to the attraction coil is stopped. 3. The device according to claim 2, wherein the switching transistor for the degaussing coil is turned off when the exciting current of the degaussing coil reaches a current value at which the residual magnetism by the attraction coil can be removed. Electromagnet device. 4. A control circuit unit is connected to an input terminal of the switching transistor for the degaussing coil, and a current limiting resistor is connected to an output terminal thereof, wherein the control circuit unit stops supplying an exciting current to the attraction coil. The current limiting resistor is configured to turn on the demagnetizing coil switching transistor, and when the demagnetizing coil switching transistor is turned on, the exciting current of the demagnetizing coil can remove residual magnetism caused by the attracting coil. The electromagnet device according to claim 2, wherein the electromagnet device is configured to limit the current value.