JPS5943258B2 - electromagnetic chuck device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chuck device for fixing a magnetic body by magnetic attraction force, and more particularly to an electromagnetic chuck device including an electromagnet device and a power supply device.

One of the means for temporarily fixing a workpiece made of a magnetic material is an electromagnetic chuck device that uses magnetic force, and the chuck device includes an electromagnet device and a power supply device.

The electromagnet device generates a constant magnetic field by receiving direct current from the power supply device, and the magnetic body is attracted and fixed to the electromagnet device by this constant magnetic field. The electromagnet device of the electromagnetic chuck device is generally susceptible to residual magnetism, and magnetism remains in the electromagnet device and the magnetic body even after the supply of the direct current is stopped. In order to eliminate this residual magnetism and facilitate the detachment of the magnetic body, at the time of detachment, an attenuating alternating current is supplied from the power supply device to the electromagnet device as a so-called loop attenuation demagnetization method. Ru. The power supply device includes a rectifier bridge circuit having a power control rectifier, an ignition circuit that supplies a gate current to the power control rectifier, and a gate current that is sent from the output end of the bridge circuit to the electromagnet device when the magnetic body is detached. and a polarity switching circuit for switching current polarity.

Control signal voltages from the constant voltage standard circuit and the attenuated voltage standard circuit are supplied to the control input terminal of the ignition circuit when the magnetic body is attracted and fixed, respectively, and when the magnetic body is removed, and a pulse current with a period based on the signal voltage value is supplied. A voltage value applied to the gate of the power control rectifying element and corresponding to the pulse period appears at the output end of the bridge circuit.

As a result, when fixed by suction, a constant DC current is sent to the electromagnet device via the output end, and when detached, the attenuated DC current passes through the output end and further passes through the polarity switching circuit, so that the attenuated alternating current is converted into the attenuated alternating current. sent to an electromagnetic device. The operation when the power supply device is disconnected is completed by stopping the operation of the polarity switching circuit when the output terminal voltage value becomes below a certain voltage value. However, in the power supply device, feedback control is not performed in controlling the output voltage at the time of disconnection.

Therefore, in order to effectively eliminate residual magnetism, a CR discharge circuit that draws a discharge voltage curve along an exponential function is used as the attenuated standard voltage circuit in order to obtain a current that follows an exponential function as the attenuated DC current. However, due to the ignition characteristics of the ignition circuit, only a decaying current along a cosine function can be obtained from the output terminal. Therefore, in order to obtain a satisfactory demagnetization effect and facilitate the separation of the magnetic material,
A specific relationship is required between the degaussing time, that is, the supply time of the attenuated alternating current to the electromagnetic device, and the polarity switching period due to the operation of the switching circuit. The adjustment process is complex and requires a relatively long degaussing time. Further, since the attenuation current along the cosine function includes many ripples and spike currents, it has been impossible to reduce the stop voltage of the polarity switching circuit to a sufficiently low value.

Therefore, the final voltage value of the attenuated alternating current supplied to the electromagnet device becomes relatively large, and the demagnetizing effect changes greatly depending on the magnitude of the magnetic inductance of the magnetic material. In addition, the ripple and spike currents included in the attenuating current often cause the polarity switching circuit to malfunction. The purpose of the present invention is to
To provide an electromagnetic chuck device which can securely fix a magnetic body, erase residual magnetism in a short time when the magnetic body is removed, and operate reliably without causing malfunction.

The present invention provides first and second attenuated voltage standard circuits each consisting of a CR discharge circuit having the same time constant;
through a feedback control system including each of the third arithmetic circuits,
The present invention is characterized in that when the magnetic body is removed from the electromagnetic device, a DC attenuation voltage that attenuates exponentially is obtained at the output end of the rectifier prism circuit.

The present invention also provides a circuit for detecting overcurrent at the output end;
and a flip-flop circuit that issues a stop signal to stop the operation of the ignition circuit in response to an overcurrent signal from the detection circuit, and the overcurrent that causes residual magnetism in the magnetic body is transmitted from the output end to the electromagnet device. The ignition circuit is characterized in that the operation of the ignition circuit is immediately stopped when the ignition circuit is about to be supplied.

Furthermore, the present invention detects an increase in the pulse period of the gate current sent from the ignition circuit to the power control rectifier of the bridge circuit, and instructs the polarity switching circuit to stop operating the polarity switching circuit. The present invention is characterized in that it includes a pulse switch circuit for sending a signal, and the operation of the pulse switch circuit ensures that the operation of the polarity switching circuit is stopped after the attenuation current has sufficiently attenuated.

The features of the invention will become clearer from the following description of the illustrated embodiment.

An electromagnetic chuck device 10 according to the present invention includes an electromagnet device 12 and a power supply device 14, as shown in FIG. The electromagnet device 12 includes an iron core 16 and a coil 18 wound around the iron core, and the iron core 16 and the coil 18 are housed in a casing 22 having an attraction surface 20. The power supply device 14 includes diodes Dl,
D2 and thyristors SCRl, SCR2, a mixed bridge circuit 26 to which an AC voltage EA from an AC power source is applied to its input terminal 24, and a circuit for igniting the thyristors SCR1, SCR2 of the mixed bridge circuit. An ignition circuit 28 that supplies a trigger pulse current, and first, second and third arithmetic circuits D having a gain of 1
Al, DA2 and DA3. The ignition circuit includes a control voltage input terminal VC and the thyristors SCRl, SC.
A trigger pulse output terminal Gl is connected to each gate terminal 30 of R2 and supplies to each gate terminal 30 a pulse current whose firing angle increases as the voltage value applied to the control voltage input terminal VC increases. . A pulse current is synchronized with the AC power source from the connected synchronizing signal human power terminals Sl, S2 and has a firing angle corresponding to the voltage value of the control input terminal VC, and is supplied to each gate terminal 30 from the output terminals Gl, G2. Furthermore, an output signal corresponding to this pulse current is generated from the signal output terminal P. The mixing bridge circuit 26 converts the AC power supplied to the input terminal 24 into DC power at a voltage corresponding to the firing angle of the pulse current supplied to each gate terminal 30 of the thyristor, which is one of the power control rectifier elements. Convert to In the illustrated example, the bridge circuit is a full-wave rectifier mixed bridge circuit, and one of its output terminals 32 is grounded. The control signal voltage value Es applied to the control voltage input terminal VC of the ignition circuit 28
and the output voltage value EO of the output terminal 32 of the mixed bridge circuit 26, as shown in FIG. 2, when each voltage value Es and EO are plotted on the horizontal axis X and vertical axis Y, respectively, It is shown by a so-called downward-sloping curve, and control signal voltage values of zero to Es in the figure are in the uncontrollable range of the output voltage EO.

The output terminal 32 of the bridge circuit is connected to a magnetic contactor MCl, M for switching the polarity as in the conventional case.
It is connected to a current supply terminal 38 connected to the coil 18 of the electromagnetic device 12 via a pair of contacts 34 and 36, respectively, of C2.

Each electromagnetic contactor MCl, MC2 is actuated by an output terminal signal of an AND circuit 40, 42 each having three input terminals, one of the input terminals of each AND circuit 40, 42 is connected to each output terminal of the astable multivibrator 44. Connected to terminals θ, θ. The unstable multivibrator 44 is
As long as the input terminal Ri receives an off signal, a positive logic signal, that is, an on signal is alternately generated from each output terminal θ, θ. A polarity switching circuit consisting of these electromagnetic contactors MCl, MC2, AND circuits 40, 42, and multivibrator 44 is configured to operate the multivibrator 44 when an off signal is received at the input terminal of either of the AND circuits 40, 42. Regardless of the contactor 34 of the electromagnetic contactor
, 36 disconnect the output terminal 32 of the bridge circuit from the current supply terminal 36, thereby preventing the supply of current from the mixing bridge circuit to the coil 18. Further, when the other two input terminals of each AND circuit 40, 42 receive an on signal, the input terminal Ri of the multivibrator 44 receives an on signal, so that one of its output terminals θ, θ An ON signal is generated only from the magnetic contactor, thereby activating one of the magnetic contactors, and the rectification from the mixing bridge circuit is supplied to the coil 18 via the current supply terminal 38 without switching the polarity. On the other hand, when the input terminal Ri of the multivibrator 44 receives an OFF signal, ON signals are alternately emitted from its output terminals θ, θ, whereby the electromagnetic contactors MCl, MC2 are alternately activated, and the The rectification from the mixing bridge circuit is switched in polarity and this alternating current is supplied to the coil 18 via the current supply terminal 38. Output terminal 32 of the mixed bridge circuit 26
is a resistor R for obtaining a partial voltage at the output terminal.

, RTl, Rl, R2, and resistors Rl, R2 connected in series with each other.
The divided voltage at the output terminal obtained by is applied to the inverting input terminal of the first arithmetic circuit, that is, in the illustrated example, the differential amplifier DAl. The resistor R. , RTl are connected in series to each other via the b1 contact of relay A, which will be described later, and the partial voltage at the output terminal 32 obtained by closing the b1 contact is applied to the non-inverting input terminal of the differential amplifier DAl. ing. Further, the resistor RTl constitutes a first discharge circuit together with the capacitor CTl connected in parallel thereto, and when the b1 contact is closed, the capacitor CT
By opening the b1 contact, the charges accumulated in the resistor RTl are discharged through the resistor RTl, and a discharge voltage that attenuates along an exponential function is applied to the non-inverting input terminal of the differential amplifier DA. The resistor R. ,KTl几2RT1,R
What are the values of 1 and R2? one? R. r. , +ROR, +R9.

Therefore, due to the closure of the contacts B, the differential amplifier D
The voltage difference between both input terminals of A becomes zero, and its output terminal voltage ER also becomes zero. Furthermore, by opening the b1 contact,
Since the discharge voltage that attenuates along an exponential function and the partial voltage of the output terminal 32 are respectively applied to both input terminals, the output end voltage ER is the target discharge voltage and the partial voltage of the output terminal. The error voltage is the difference between the voltage and the voltage. FIG. 1A shows a graph showing an example of voltage changes at each terminal of the amplifier DAl, where the negative region on the X-axis indicates when the b1 contact is open, and the positive region on the X-axis indicates the b1 contact. Shows when closed.

By closing the b1 contact, a discharge voltage is applied to the non-inverting input terminal of the amplifier DAl, which attenuates along the above-described exponential function, as shown by the characteristic line α1 of the graph. Further, when a non-exponential decay voltage as shown by the characteristic line β1 of the graph is applied to the inverting input terminal, the amplifier D
A negative output voltage ER as shown by γ1 in the graph is outputted to the output terminal of Al as the error voltage. The non-inverting input terminal of the second arithmetic circuit, that is, the differential amplifier BA2 in the illustrated example, is connected to the variable resistor of the constant voltage standard circuit consisting of a DC constant voltage source VR and a variable resistor R3 connected in series. The partial voltage EB of the voltage source VR obtained by R3 is applied to the b1 of the relay A.
ΔE from the partial voltage EB applied by closing the B2 contact similar to the contact, and obtained by the variable resistor R4 connected in parallel to the B2 contact by opening the B2 contact.
B A small partial pressure (E3-ΔEB) is applied.

The inverting input terminal of the differential amplifier DA2 is connected to the b1, B2
It is connected to the constant voltage source VR through a voltage dividing circuit consisting of resistors R''4 and RT2 connected in series through the B3 contact of the relay A, which is similar to the contact point, and the B3
By closing the contact, the constant voltage source V is applied to the inverted human power terminal.
A partial pressure Es of R is applied. The resistor RT2 and the capacitor CT2 connected in parallel constitute a second discharge circuit having the same time constant as that of the first discharge circuit, and when the contact B3 is closed, the capacitor CT2 is connected to the resistor RT2. The charged electric charge is released by opening this B3 contact,
A damped discharge voltage is applied to the inverting input terminal which is discharged through the resistor RT2 and corresponds to the damped discharge voltage obtained by the first discharge circuit. Therefore, the above B2
, B3 contact is closed, the divided voltages EB and E8 of the constant voltage source VR are applied between the input terminals of the amplifier DA2, respectively, so that the output terminal voltage EB is divided from the divided voltage EB. The DC voltage is the difference between the voltage Es and the voltage Es. Also,
By opening the B2 and B3 contacts, the non-inverting input terminal receives a DC partial voltage e''B (EB-
ΔEB) is applied to the inverting input terminal, and since a discharge voltage that decays along an exponential function is applied to the inverting input terminal as described above, the output terminal voltage EB is equal to the DC partial voltage e.
The difference between ``B'' and the discharge voltage increases as the discharge voltage decreases exponentially. FIG. 1B shows a graph similar to FIG. 1A showing voltage changes at each terminal of the amplifier DA2. The positive region of the X-axis is the above-mentioned B2 and B
Shows when 3 contacts are closed. Due to the closed contact of the B2 and B3 contacts, a constant positive voltage △EB smaller than the voltage EB when the B2 contact is open is applied to the non-inverting input terminal of the amplifier DA2, as shown by the characteristic line α2. (EB1△EB)
is applied. Further, a voltage E8 smaller than the positive voltage (EB-△EB) of the non-inverting input terminal is applied to the inverting input terminal.
A voltage is applied as shown by a characteristic line β2 which coincides with the characteristic line β1 and which attenuates along an exponential function from . Therefore, as shown by the characteristic line γ2, the output terminal of the amplifier DA2 has a voltage (EB-ΔE
B) and the initial value Es of the voltage of its inverting input terminal (EB-△EB-ES), the voltage value (EB-△EB
) is outputted as a positive control voltage EB that gradually increases exponentially toward . The output terminals of the first and second differential amplifiers DAl and DA2 are respectively connected to the inverting input terminal and the non-inverting input terminal of the third arithmetic circuit, that is, in the illustrated example, the differential amplifier DA3. amplifier DA
The output terminal of No. 3 is the control input terminal V of the ignition circuit 28.
Connected to C.

Therefore, when the relay A is not activated, each b contact is closed, so the output terminal voltage Es of the third differential amplifier is equal to the output terminal voltage of the second differential amplifier DA2. EB is the DC voltage difference between the partial voltage EB and the partial voltage Es (EB - Es). Furthermore, since each b contact is placed in an open state by the start of operation of the relay A, the output terminal voltage Es of the third differential amplifier DA3 is a DC voltage of the difference between the divided voltage EB and the divided voltage Es. a voltage that increases as the attenuated discharge voltage value decreases from a voltage value (EB-ES-ΔEB) smaller than the value ΔEB;
This is the difference from the error voltage. FIG. 1C shows a graph similar to FIGS. 1A and 1B showing voltage changes at each terminal of the amplifier DA3, and the positive region on the X axis is the b1
, shows when the B2 and B3 contacts are closed.

By closing the b1, B2, and B3 contacts, the non-inverting input terminal of the amplifier DA3 has the characteristic line γ2 in FIG. 1B.
A positive voltage EB shown by is applied, and a negative voltage ER shown by a characteristic line γ1 in FIG. 1A is applied to its inverting input terminal. Therefore, a positive corrected control voltage Es as shown by a characteristic line γ3, which is the sum of the absolute value of the positive voltage EB and the absolute value of the negative voltage ER, is outputted to the output terminal. As long as the ignition circuit 28 receiving the control voltage receives the activation signal at the control signal input terminal C, the ignition circuit 28 operates at a constant cycle according to the difference between the partial pressure EB and the partial pressure Es when the relay A is not activated. is applied to each gate terminal 30 of the thyristor, thereby increasing the voltage E at the output terminal 32.

is maintained at a constant DC voltage value according to the cycle of the pulse current. Further, when the relay A starts operating, the ignition circuit 28 includes the error voltage and the partial pressure difference (EB-E
A pulse current whose firing angle gradually increases in accordance with a voltage value gradually increasing with an initial value smaller than ΔEB than s) is supplied to each gate terminal 30 of the thyristor, thereby increasing the voltage E at the output terminal 32. is gradually decreased from a value ΔB larger than the constant DC voltage value. An example of a change in the voltage value of the output terminal 32 before and after the start of operation of the relay A is shown in the graph of FIG. The Y-axis represents the voltage value E of the output terminal 32. Indicates (). The discharge voltage that decays along the exponential function of the CR discharge circuit, which is the most preferable decay voltage that is to be obtained when the magnetic body attracted by the electromagnet is released, that is, the target value, is shown in the first quadrant by a dotted line A, The voltage at the output terminal 32 of the power supply device 14 according to the invention is indicated by line B. When the relay A is not activated, the voltage value is constant as shown in the second quadrant, and as soon as the relay A starts to operate, the voltage value increases by the partial pressure ΔB, and begins to attenuate from this value as time passes. , this attenuation voltage is
It decays exponentially along the line A as shown in the first quadrant. On the other hand, according to the conventional power supply device, the output terminal voltage similar to the output terminal 32 which becomes a constant voltage value when a magnetic material is attracted, as shown by the dashed line C, is as follows.
When the magnetic body is removed, the voltage does not attenuate along the line A, which is the target value, but attenuates in a cosine function from the constant voltage value. The voltage increase ΔB before and after the activation of the relay A of the output terminal 32 according to the present invention is adjusted to a desired value by operating the variable resistor R4, and the output terminal voltage when magnetic material is attracted is It is adjusted to a desired value by operating the resistor R3. The control signal input terminal C for controlling the supply of the gate pulse current of the ignition circuit 28 is connected to the reset output terminal θ1 of the first RS flip-flop F1.

The set output terminal θ1 of the first flip-flop F1 is connected to one input terminal of an AND circuit 46 having two input terminals and to one input terminal of each of the AND circuits 40 and 42 of the polarity switching circuit, The set input terminal R of the flip-flop F1 and the set input terminal S1 are connected to an OR circuit 48 having three input terminals, respectively.
and each output terminal of an OR circuit 50 having two input terminals. The other input terminal of the AND circuit 46 is connected to the set input terminal of the second RS flip-flop F2, and the output terminal of the AND circuit 46 has the b1, B2, and B3 contacts described above, and the B4 contact and It is connected to a relay circuit 52 that includes the relay A having an a1 contact and operates the relay A with a time difference with respect to an input signal. The set input terminal R2 of the second flip-flop F2 is connected to the output terminal of the OR circuit 48, and the set input terminal S2 of the flip-flop F2 is connected to the DC power supply 54 via the first push button switch Pbl. There is. The power supply 54 connects the first push button switch Pbl to each input terminal of the OR circuit 50 and one of the input terminals of the OR circuit 48, respectively.
Second push button switch Pb2 and third push button switch P
b3, and is also connected to B4 of the relay A.
It is connected to the input terminal Ri of the multipipulator 44 via a contact. The push button switch Pbl, P
Each of b2 and Pb3 is a normally open switch that normally keeps its contacts open. The other two of the OR circuit 48
One of the two input terminals is connected to the overcurrent detection circuit, and the other is connected to the pulse switch circuit 52 via the relay Af)a1 contact. In the illustrated example, the overcurrent detection circuit is a resistor whose one end is connected to the current supply terminal 38 which becomes the ground side when supplying a constant DC current to the coil of the electromagnet 12, and whose other end is grounded. 51
If the voltage drop caused by the resistor exceeds a certain specified value, this voltage drop is applied to the input terminal of the OR circuit 48 as an overcurrent detection signal. The pulse switch circuit 52 includes a thyristor 58 that is forwardly connected to a DC power source 54 via a resistor 56, and a capacitor 60 that is electrically connected in parallel with the thyristor 58 between the anode and cathode of the thyristor. The gate of the thyristor 58 is connected to the signal output terminal P of the ignition circuit 28.

The collector of an NPN transistor TR is connected to the positive electrode terminal side of the power source 54, and the collector of the transistor T
The base of R is connected to the thyristor at its anode side, and the emitter is grounded via a resistor 62. The output terminal 64 connected to the emitter is connected to the input terminal of the OR circuit 48 via the relay Af:)a1 contact, and is also connected to the input terminals of the AND circuits 40 and 42 via the NOT circuit 66. Each is connected to one of the The resistor 56 keeps the forward current of the thyristor at a value equal to or lower than the holding current, and according to the pulse switch circuit, the pulse firing angle of the gate current from the output terminal P is equal to the capacitor 60 and the resistor 56. When the resistor 56 is less than about one tenth of the time constant τ of
Since the current supplied from the power supply 54 via the thyristor 58 flows through the thyristor 58, the capacitor 60 is not charged, and therefore the base voltage is held negative with respect to the emitter voltage, and the output terminal No on signal is emitted from 64. On the other hand, the output terminal P
As the pulse firing angle of the gate current increases, the capacitor 60 is charged by the current flowing from the power supply 54 through the resistor 56, and this charging voltage causes the base voltage to become positive with respect to the emitter voltage. is maintained. Therefore, a current flows from the collector to the emitter, and a voltage drop due to the resistor 62 is applied to the output terminal 64.
It is issued as an on signal. In the power supply device 14 according to the present invention, when the contact of the second push button Pb2 is closed, the activation signal is applied to the set input terminal S1 of the first flip-flop F1 via the OR circuit 50. As a result, an ON signal is generated from the set output terminal θ1 of the first flip-flop F1, and an OFF signal is generated from the set output terminal θ1.

On the other hand, since no input signal is applied to the set input terminal S2 of the second flip-flop F2 and the relay A of the relay circuit is kept in a non-operating state, the a1 contact is opened and each of the above-mentioned B contacts b1 to B4 are closed. Accordingly, the ignition circuit 28 receives the OFF signal at its control signal input terminal C, so that it is activated.
Furthermore, since each b contact is in the closed state, as described above, a pulsed gate current of a constant firing angle is applied to the output terminal Gl in accordance with the constant voltage value applied to the control voltage input terminal VC. , G2, the thyristor SCRl,S
Supplied to each gate of CR2. Further, the ignition circuit 28
Since a pulse with a constant firing angle corresponding to the pulse current from the output terminals Gl and G2 of is applied from the signal output terminal P to the gate terminal of the thyristor 58 of the pulse switch circuit 52, the pulse switch circuit 52
An OFF signal is issued from the output terminal 64 of. This OFF signal passes through the NOT circuit 66 as an ON signal and is output to the AND circuits 40 and 4 together with the ON signal from the set output terminal θ1 of the first flip-flop F1.
By closing the B4 contact, an ON signal from the power source 54 is applied to the input terminal Ri of the multivibrator 44, and either one of the output terminals θ, θ of the vibrator 44 is applied to the input terminal Ri of the multivibrator 44. Since the ON signal is emitted from the contactor, either one of the electromagnetic contactors MCl and MC2 is activated, and one of its contacts 34 and 36 is closed. Therefore, the DC voltage and current that has been controlled to a desired constant voltage value by the preload circuit 26, which receives the gate current from the ignition circuit 28, is transferred from the current supply terminal 38 to the current supply terminal 38 without having its polarity changed. The electromagnetic device 12 is supplied to the coil 18 of the electromagnetic device 12 and generates a constant magnetic field by this direct current.
attracts and fixes the magnetic material by its magnetic force. When the magnetic body that has been attracted and fixed is to be removed from the electromagnet device 12, the first push button switch Pbl is operated, thereby closing its contact. Closure of this contact causes an input signal to be applied to the set input terminal S2 of the second flip-flop F2 as well as to the set input terminal S1 of the first flip-flop F1. As a result, the AND circuit 46 operates on both flip-flops Fl and F.
An activation signal is sent to the relay circuit upon receiving the output signal from each set output terminal .theta.1, .theta.2, and the relay circuit activates the relay A after a certain period of time has elapsed. Due to the operation of the relay A, the a1 contact is closed and at the same time the b
1 to B4 are in the open state, and the ignition circuit 28 is applied with a voltage value gradually increasing from a value smaller than the constant value to its control voltage input terminal VC, as described above. A pulse-like gate current whose firing angle increases gradually is supplied to each gate of the thyristors SCR1 and SCR2. Further, due to the opening of the B4 contact, the multivibrator 44 receives an OFF signal at its input terminal Ri, and therefore outputs an ON signal alternately from its output terminals θ, θ, thereby causing the electromagnetic contactors MC, MC
2 are activated alternately. Therefore, the DC voltage and current that are controlled by the bridge circuit that receives the gate current from the ignition circuit 28 and that attenuate from a value larger than the constant voltage value as shown in FIG. Its polarity is switched by the operation of , and the current is supplied from the current supply terminal to the coil 18 as an alternating decay current. By supplying this alternating decay current, the electromagnetic device generates an alternating magnetic field that is attenuated from a magnetic field strength greater than the value of the magnetic field when the magnetic body is attracted, and this alternating magnetic field causes residual magnetism in the magnetic body and the electromagnet device. is erased to an almost negligible extent, and the magnetic body can be easily removed from the electromagnetic device. Stopping the supply of attenuated alternating current to the electromagnetic device, ie, completion of demagnetization, is accomplished by actuation of the pulse switch. That is, as described above, the gradual decrease in the voltage value of the output terminal 32 is based on the gradual increase in the pulse firing angle of the gate current from the ignition circuit 28 to the thyristors SCRl, SCR2. When the pulse firing angle of the gate current applied from the signal output terminal P to the pulse switch circuit according to the angle exceeds a certain value, the pulse switch circuit issues an ON signal from its output terminal 64 as described above. .
This ON signal is converted into an OFF signal by passing through the NOT circuit 66, and is applied to one of the input terminals of the AND circuits 40 and 42. Therefore, the electromagnetic contactor MCl
, MC2 are stopped, and both of these contacts are placed in an open state, so that the supply of current to the electromagnetic device is stopped, thereby completing the demagnetizing operation. Furthermore, when an overcurrent is to be supplied through the current supply terminal 38 when current is supplied to the electromagnet device, the voltage drop due to the resistor 51 exceeds a specified value, so the voltage exceeding this specified value is A deactivation signal is applied to the input terminal of the OR circuit 48, and an input signal is applied to the set input terminals R1, R2 of the first and second flip-flops Fl, F2, respectively. This signal causes each flip-flop to stop sending output signals from the set output terminals θ1 and θ2,
The stop of this output signal serves as an off signal to the AND circuit 4.
0 and 42, each contact is held open and the supply of overcurrent to the electromagnetic device is blocked, as described above. At the same time, a stop signal is sent from the reset output terminal θ1 of the first flip-flop F1 to the control signal input terminal C of the ignition circuit 28, so that the supply of gate current from the ignition circuit 28 is stopped and each difference is The dynamic amplifiers DAl, DA2, DA3 are protected from damage due to overcurrent. The operation of the power supply device as described above can be stopped by operating the third push button switch Pb3, and by closing this switch contact, a stop signal similar to the stop signal due to the overcurrent is sent through the OR circuit 48. Since the voltage is applied to each of the set input terminals of the flip-flops Fl and F2, the power supply device can be maintained in the ready state as described above by operating the third switch Pb3.

FIG. 4a shows an example of the relationship between the switching period T of the attenuation current at the time of detachment of the electromagnetic chuck device according to the present invention and the magnetic attraction force Fr remaining in the magnetic material after detachment, The X-axis is the switching period T, (Sec
．． ), and the Y axis represents the magnetic attraction force Fr(y/
Cd). Furthermore, FIG. 4b is a graph similar to FIG. 4a for the conventional device, and as is clear from the comparison of both graphs, according to the present invention, regardless of the increase or decrease in the switching period, the A superior demagnetizing effect can be obtained. FIG. 5 shows an initial voltage value of the attenuated alternating current supplied to the magnet device, that is, a demagnetization start voltage value EdO
(V) and the magnetic adsorption force Fr (t/Cr!i) of the magnetic body after demagnetization, the demagnetization start voltage value EdO (V) and the magnetic adsorption force Fr (y/Cd) are determined respectively. The graph is shown as an X-axis and a Y-axis, and the graph is an example of experimental results showing the effect of erasing the residual magnetism of the magnetic body after supplying 80V DC voltage and current to the electromagnetic device. .

As is clear from this graph, the larger the demagnetization start voltage value supplied to the electromagnet device with respect to the DC current voltage value supplied to the electromagnet device when a magnetic body is attracted, the more the DC voltage and current The greater the initial value of the attenuated alternating magnetic field with respect to the magnetic field strength, the greater the demagnetization effect. In the electromagnet device according to the present invention, when the magnetic body is detached, the voltage control in the power supply device is performed by the return circuit, so that it is demagnetized regardless of the uneven characteristics of the thyristors of the mixed bridge circuit. It is supplied with an alternating current that is exponentially damped and has very little spike current and ripple current, suitable for this purpose.

Furthermore, when the supply of the attenuated alternating current is stopped, the change in the pulse period from the ignition circuit is reliably detected by the pulse switch circuit. The alternating attenuated voltage is supplied until the voltage reaches the specified value, and the power supply device does not malfunction. Therefore, according to the present invention, irrespective of the magnitude of the magnetic inductance of the magnetic body, it is possible to effectively erase the residual magnetism of the magnetic body imparted by a constant magnetic field during attraction and fixation, and to reduce variations in the demagnetization effect. It can be reduced to about 1/10 compared to the conventional one, and no large residual magnetism remains in the magnetic material.

Further, according to the present invention, as described above, a uniform demagnetizing effect can be obtained regardless of an increase or decrease in the switching period, and the switching period can be easily set to the most suitable value.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an electromagnetic chuck device according to the present invention, and FIGS. 1A to 1C are graphs showing voltage changes at each terminal of the differential amplifiers DAl to DA3 shown in FIG. 1, respectively. FIG. 2 is a graph showing the characteristics of the ignition circuit of the electromagnetic chuck device according to the present invention, and FIG. 3 is a graph showing the output terminal voltage when the magnetic body of the mixed bridge circuit of the electromagnetic chuck device according to the present invention is detached. FIGS. 4A and 4B are graphs showing the relationship between the magnetic attraction force due to the residual magnetism of the magnetic material and the switching period in the electromagnetic chuck device according to the present invention and the conventional electromagnetic chuck device, respectively, and FIG. 1 is a graph showing the relationship between the demagnetization start voltage of the electromagnetic chuck device according to the present invention and the attraction force due to the residual magnetism of the magnetic material. 12: Electromagnet device, 14: Power supply device, SCRl, SCR
2: Power control element, 28 two-striking circuit, 26: Rectifier bridge circuit, VC: Control voltage input terminal, 32: Output terminal of rectifier bridge circuit, 34, 36, MC1, MC2, 40,
42, 44: polarity switching circuit, VR, R3: constant voltage standard circuit, CTl, RTl: first attenuated standard voltage circuit, CT2
, RT2: second attenuated standard voltage circuit, DAl, DA2,
DA3: first, second and third arithmetic circuits, 51: overcurrent detection circuit, 52: pulse switch circuit, Fl, F2:
flip-flop circuit.

Claims (1)

[Scope of Claims] 1. An electromagnet device, a direct current is supplied to the electromagnet device for attracting and fixing a magnetic body, and a residual magnetism of the electromagnet device is supplied for detaching the magnetic body from the electromagnet device. a power supply device that supplies an attenuated alternating current to the electromagnetic device for erasing, the power supply device having a rectifying bridge circuit having a power control rectifying element and a control voltage input terminal;
an ignition circuit that supplies a gate current to the power control rectifier to reduce the voltage at the output terminal of the bridge circuit as the voltage at the control voltage input terminal increases; and an output terminal of the bridge circuit that is activated when disconnected. and a polarity switching circuit for switching the polarity of the current supplied to the electromagnet device, the power supply further comprising a constant voltage standard circuit and a CR discharge circuit each having the same time constant. first and second attenuated voltage standard circuits, the difference between the divided voltage of the output end voltage of the bridge circuit and the CR charging voltage of the first attenuated voltage standard circuit, and the divided voltage of the output end voltage of the bridge circuit; CR of the first attenuated voltage standard circuit
a first arithmetic circuit that obtains the difference between the discharge voltage and the constant voltage of the constant voltage standard circuit and the CR of the second attenuated voltage standard circuit;
a second arithmetic circuit that obtains the difference between the charging voltage and the constant voltage of the constant voltage standard circuit and the CR discharge voltage of the second attenuated voltage standard circuit; and outputs of the first and second arithmetic circuits. a third arithmetic circuit for obtaining an end voltage difference;
An electromagnetic chuck device, wherein an output terminal voltage of an arithmetic circuit is applied to a control voltage input terminal of the ignition circuit. 2. Further, the power supply device includes a circuit for detecting an overcurrent sent from an output terminal of the bridge circuit to the electromagnet device, and supplying a gate current to the power control rectifier according to an overcurrent signal from the detection circuit. The electromagnetic chuck device according to claim 1, further comprising a flip-flop circuit that sends a stop signal to the ignition circuit to stop the ignition circuit. 3. Furthermore, the power supply device includes a circuit for detecting an overcurrent sent from an output terminal of the bridge circuit to the electromagnet device, and supplying a gate current to the power control rectifier by an overcurrent signal from the detection circuit. a flip-flop circuit that sends a stop signal to the ignition circuit to stop it; and a flip-flop circuit that detects an increase in the pulse period of the gate current supplied from the ignition circuit to the power control rectifier and stops the operation of the polarity switching circuit. The electromagnetic chuck device according to claim 1, further comprising a pulse switch circuit that sends a stop signal to the polarity switching circuit to cause the polarity switching circuit to stop.