JP2022162228A - Demagnetization method - Google Patents

Abstract

To process a workpiece while an electromagnetic chuck using an electromagnet is magnetized to adsorb the workpiece and cause demagnetizing current to flow through the coil of the electromagnet when the workpiece is detached, thereby performing demagnetization of the workpiece in a short time.SOLUTION: In a method of performing excitation by applying an alternating magnetic field using a coil of an electromagnetic chuck, a commercial power supply is stored in a capacitor, and a DC voltage which is 1.414 times as large as a commercial power supply voltage is alternately switched over time and applied to the coil as a pulse voltage, and a pulse voltage which is successively attenuated by setting the pulse width of a first wave of demagnetization and an attenuation rate of an alternating pulse is applied to supply an alternating current whose current peak value successively decreases linearly. When the pulse voltage width to be applied is 0.01 second or less, the minimum pulse width is switched to 1/10 or less, and a voltage pulse having a pulse width of 0.01 second to 0.0005 second is applied to the coil, thereby causing a minute alternating attenuated current to flow through the coil of the electromagnetic chuck.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method of demagnetizing a magnetized magnetic body, and more particularly to a method of demagnetizing a workpiece by applying a gradually decreasing AC pulse current when applying an alternating DC pulse voltage to the coil of an electromagnetic chuck. It relates to an apparatus for carrying out.

The electromagnetic chuck is activated by the initial operation of magnetizing the electromagnetic chuck by passing an electric current through the coil, and in this state it is possible to retain a piece of metal made of magnetic material by the action of magnetic attraction. After that, the current supply to the coil is maintained while the electromagnetic chuck is in use. Then, the electromagnetic chuck is deactivated by degaussing the coil by supplying a reverse current to the coil, and the metal piece that has been held until then is released.

A work material made of a magnetic material must be reliably magnetized when it is processed. However, if magnetism remains even when degaussing is performed after work and the work material is removed, the work material cannot be removed. In addition, since it is often necessary to demagnetize the removed work material, it is necessary to demagnetize the work material.

In order to demagnetize an object to be demagnetized, including the work piece as described above, the object to be demagnetized must be demagnetized while its position is fixed. The following methods are available for demagnetizing an object to be demagnetized while its position is fixed.

A method in which a damped oscillating current is formed by an LC resonance circuit of a capacitor and a coil, and the object to be demagnetized is fixed in position and demagnetized.

Full-wave rectification of the AC power supply, demagnetization pulse with a first demagnetization pulse width that is a multiple of the demagnetization period at a demagnetization period (0.01 second or 0.00833 second) that is half the AC power frequency (50 Hz or 60 Hz). A demagnetization method that applies a DC voltage pulse that is applied to the coil and attenuates while switching the polarity until the pulse width reaches 0.01 seconds or 0.00833 seconds (for example, see Patent Document 1, hereinafter referred to as "pulse voltage type" ).

A method of demagnetizing an object to be demagnetized while keeping its position fixed by creating a DC reversal damping current. Conventionally, it was used in laboratories and was used as a method of complete demagnetization in which the current was gradually attenuated to zero over several minutes to completely eliminate the magnetism. A commercially available demagnetizer will attenuate a DC reversal current of several hertz over a period of about one minute.

A degaussing method in which a DC voltage is alternately applied to a coil, and an alternating current whose current peak value decreases sequentially linearly from a predetermined value is applied to demagnetize, or a demagnetizing method in which a decaying alternating current is applied to the coil (for example, Patent Document 2 Reference, hereinafter referred to as "current type").

JP-A-10-229014 JP-A-04-114413

The above-mentioned pulse voltage type demagnetization requires a long demagnetization time of about 8 seconds. With automation of equipment, reduction of demagnetization time is required.

On the other hand, since the current type switches the polarity by comparing the set current value and the current current value, there is a limit to discrimination of minute signals, depending on the performance of the comparator. Also, there is a problem that the demagnetization time changes when the object to be demagnetized changes.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to complete demagnetization in a short period of time with little residual magnetism in the minute output pulse system.

In order to solve the above-mentioned problems, the present invention provides a method of performing excitation by applying an alternating magnetic field using a coil of an electromagnetic chuck, wherein a commercial power source is stored in a capacitor in the coil, and 1.1. A 414 times DC voltage is alternately applied as a pulse voltage with the passage of time, and a pulse voltage that is successively attenuated by setting the pulse width of the first wave of demagnetization and the attenuation rate of the alternating pulse is applied. An alternating current whose current peak value gradually decreases linearly is applied, and when the pulse voltage width to be applied becomes 0.01 seconds or less, the minimum pulse width as a reference is switched to 1/10 or less, and a 0.01 second pulse is generated. A degaussing method and a degaussing device characterized in that a minute alternating decay current is applied to a coil of an electromagnetic chuck by applying a voltage pulse with a pulse width of 0.0005 seconds to the coil.

The present invention has the following effects. In the invention according to claim 1, as a method of demagnetizing by alternately switching and applying a DC voltage to the excitation coil, the pulse width is attenuated from the first demagnetization pulse width according to the attenuation rate setting value, thereby demagnetizing sequentially and linearly. When the current is reduced and the demagnetization pulse width becomes 0.01 seconds or less, a minute demagnetization current that alternates with a finely reduced pulse width of 1/10 or less is passed through the coil to demagnetize the object, even if the object is voluminous. Alternatively, even if the object is strongly magnetized, the inside of the object can be demagnetized satisfactorily.

In the invention according to claim 2, the gradually decreasing demagnetizing pulse voltage output is output as a continuous pulse group without breaks, thereby suppressing the noise generated by the back electromotive force generated from the coil and improving the demagnetizing performance. there is

In the invention according to claim 3, the object can be reliably demagnetized by implementing the demagnetization method described above.

It is a figure explaining the structure of the degaussing apparatus which concerns on this invention. It is a control block diagram of the demagnetization device according to the present invention. 4 is a graph of demagnetization voltage waveforms for carrying out the demagnetization method according to the present invention; 4 is a graph of a demagnetizing current waveform for carrying out the demagnetizing method according to the present invention; 4 is a graph of detailed voltage waveforms for carrying out the demagnetization method according to the present invention; 4 is a graph of detailed voltage waveforms for carrying out the demagnetization method according to the present invention; 1 is a principle diagram showing the strength of voltage and current; FIG. FIG. 4 is a relational diagram of various generated pulse output voltages and currents for carrying out the demagnetization method according to the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In the demagnetization method according to the present invention, a demagnetization period D, which is a first demagnetization period, and a detailed demagnetization period Df, which is a second demagnetization period continuous with the demagnetization period D, are set in advance. Efficient demagnetization is realized by applying a detailed demagnetization pulse during the detailed demagnetization period Df. That is, when the width of the attenuated degaussing pulse in the degaussing period D becomes twice the basic pulse width, the detailed degaussing period Df is entered to add a detailed demagnetizing pulse train that becomes a reduced reference pulse with a reduced basic pulse width. Therefore, it is possible to obtain good demagnetization performance in a short demagnetization time.

In the present invention, the value of the basic pulse width is not limited, and it is preferable to appropriately set the value corresponding to conditions such as the target demagnetization time.

FIG. 1 shows an outline of an apparatus for carrying out the demagnetization method according to the present invention, which includes an electromagnetic chuck 1 capable of holding a workpiece (metal piece) 5 so that it does not move during machining, and a control device 10. It is. The electromagnetic chuck 1 is composed of a winding wire (hereinafter referred to as a coil) 3 with a small resistance and an iron core 2. When an electric current is supplied to the coil 3 from a conducting wire 9, an electric current is generated on the face plate 4 of the electromagnetic chuck 1 via a separator 6. As a result, magnetic fluxes of the north pole 7 and the south pole 8 are generated in the magnetic poles forming the face plate 4 (the polarity of the magnetic poles alternates depending on the direction of the current flowing through the coil). A conductor 9 connected to the coil 3 of the electromagnetic chuck 1 is connected to a controller 10 for magnetizing and demagnetizing the magnetic poles N and S of the face plate 4 .

FIG. 2 is a diagram showing the configuration of the control device 10. As shown in FIG. AC power supplied from a commercial power supply 100 is full-wave rectified via a rectifier (bridge diode) 11 and charged in a capacitor 13 via a current limiting resistor 12 and the like. The DC voltage charged in the capacitor 13 becomes the peak value of the commercial AC power supply (1.414 times the commercial AC voltage). When the gates of the power MOSFETs 14 and 17 are turned on by control signals from the power MOSFETs 14 to 17 and the PWM output control unit 30, which combine this DC voltage into an H bridge, a forward current flows through the coil 3 of the electromagnetic chuck 1. , sucks the workpiece 5 on the face plate 4 .

When the gates of the power MOSFET 15 and the power MOSFET 16 are turned on, a current flows in the coil 3 of the electromagnetic chuck 1 in the negative direction, demagnetizing the workpiece 5 on the face plate 4 . The controllers of these four power MOSFETs 14-17 and snubber circuits 18-21 are connected to the control electronics inside the controller 10, and the controller 10 has a manual operation controller 22 or an external manual (or automatic ) is connected to the control unit 23 . Using the manual operation control unit 22 or the external manual (or automatic) control unit 23, the operator can magnetize the magnetic poles to the N pole 8 and the S pole 7 to put the electromagnetic chuck into a magnetized state or to put it in a demagnetized state. You can choose to

Next, an embodiment of the demagnetization method according to the present invention will be specifically described. In this embodiment, a pulse voltage is applied to the coil 3 of the electromagnetic chuck 1 by a pulse group in which a plurality of pulses are continuous.

FIG. 3 shows an outline of transition of the demagnetizing voltage during the demagnetizing operation. In the figure, the horizontal axis represents the time t, and the vertical axis represents the applied voltage value, that is, the attenuating demagnetizing pulse voltage applied to the coil 3. FIG. More specifically, the degaussing of the electromagnetic chuck 1 is performed by applying a first degaussing pulse T1, a second degaussing pulse T2, . This is done by applying a number of successive demagnetizing pulse trains to the coil 3 .

The total number of degaussing pulse trains is 20 to 60-odd. Each demagnetizing pulse T1, T2, . On the other hand, the sign changes between one demagnetizing pulse and the next demagnetizing pulse. That is, the N pulse signs of the first demagnetizing pulse train T1 are all negative pulses, the signs of the N2 pulses of the second demagnetizing pulse train T2 are all positive pulses, and the third demagnetizing pulse train T3 is The signs of the N3 pulses are all negative pulses, the signs of the N4 pulses of the fourth demagnetizing pulse train T4 are all positive pulses, and so on.

Furthermore, the current pulse intensities I1, I2, . In between, it decreases, for example linearly, according to a certain mathematically defined law.

The positive demagnetizing pulse trains T2, T4, T6, . , and the negative demagnetizing pulses T1, T3, T5, .

FIG. 5 shows the waveform from the initial demagnetizing pulse voltage T1 to the final demagnetizing pulse voltage Tn+m during the demagnetizing period D, and FIG. Detailed pulse voltage waveforms up to degauss pulse Tn+20 are shown. Also, FIG. 4 shows the exciting current waveform of the exciting current I of the pulse voltages of the demagnetizing pulses T1 to Tn+m.

As shown in these figures, in this embodiment, the DC voltage stored in the capacitor 13 is 1.414 times that of the commercial power supply, so that a cycle independent of the power supply frequency can be realized at the PWM frequency. For example, the basic demagnetizing pulse is generated based on the basic period of 0.005 seconds of the basic demagnetizing pulse preset in the demagnetizing period D, and the basic detailed demagnetizing pulse in the detailed demagnetizing period Df has a basic period of 1/10 of the basic period of the basic demagnetizing pulse. Generated based on 0.0005 seconds.

If the demagnetizing pulse T1 of the demagnetizing period D is set as the first demagnetizing pulse m times the fundamental period of 0.005 seconds, the second demagnetizing pulse T2 will be the value obtained by multiplying the fundamental period of the first demagnetizing pulse T1 by the attenuation factor. . By being multiplied by the set attenuation rate, the demagnetization pulse gradually decreases in pulse width until the pulse width reaches 0.01 seconds (twice the basic period), after which it shifts to the detailed demagnetization period Df. . Incidentally, the value of the attenuation rate is not limited, and it is preferable to set it appropriately corresponding to the target demagnetization time.

In the shifted detailed demagnetization period Df, the first detailed demagnetization pulse is generated with 20 pulses for 0.01 second based on the demagnetization pulse basic period of 0.0005 seconds, and the first detailed demagnetization pulse is generated with 20 pulses for 0.01 second. Output from degauss pulse to final detail degauss pulse of 0.0005 seconds.

FIG. 5 further shows that when the electromagnetic chuck 1 is magnetized, the same control device 10 is used to apply a positive pulse train MAG to the gates of the power MOSFETs 14 and 17 from the PWM output control unit 30 to the coil 3 surrounding the iron core 2. It shows that it can be adsorbed by An OFF time during which the electromagnetic chuck 1 is not energized is interposed between the end of magnetization and the beginning of the demagnetization period D.

The voltage and current intensity at the time of pulse output during magnetization or demagnetization period D are based on the principle shown in FIG. ) is controlled by the PWM output controller 30 .

More specifically, FIG. 8(a) shows a single ON pulse of 0.005 seconds×10 (=0.05 seconds) applied to the gates of the power MOSFETs 15 and 16 corresponding to the pulse train at the beginning of the demagnetization process. shows the variation of the voltage and current intensity I of .

FIG. 8(b) shows the voltage and current intensity of a single pulse when ON for 0.005 seconds×2 (=0.01 seconds) at the gates of the power MOSFETs 15 and 16 corresponding to the pulse train at the beginning of the demagnetization process. shows the change in height I.

FIG. 8(c) shows the voltage and current intensity of a single pulse when ON for 0.0005 seconds×10 (=0.005 seconds) at the gates of the power MOSFETs 15 and 16 corresponding to the pulse train at the beginning of the demagnetization process. shows the change in height I.

FIG. 8(d) shows the voltage and current intensity of a single pulse when ON for 0.0005 seconds×1 (=0.0005 seconds) at the gates of the power MOSFETs 15 and 16 corresponding to the pulse train at the beginning of the demagnetization process. shows the change in height I.

As shown in FIG. 8, the demagnetizing pulse width in the demagnetizing period D can be set by increasing or decreasing the demagnetizing current value reaching the rated current of the coil 3 by controlling the ON time of the gates of the power MOSFETs 15 and 16 . The demagnetizing current gradually decreases corresponding to the preset attenuation rate while changing the polarity, and when it reaches 0.01 sec, it shifts to the detailed demagnetizing period mode where the basic pulse becomes 0.0005 sec, and 0.01 sec (0 The first detailed demagnetizing pulse of 0.0005 seconds×20) is generated, and the detailed demagnetizing pulse gradually decays by 0.0005 seconds, and is finally output until a pulse of 0.0005 seconds is applied.

The invention is not limited to the one embodiment of the demagnetization method described above, by way of example, with reference to the accompanying drawings. Rather, the invention includes uses of all versions and adaptations based on the same principles. In particular, the following can be done without departing from the scope of the invention.

・Change the basic period of the demagnetizing pulse in the demagnetizing period D to less than 0.0005 seconds.

- Change the basic period of the detailed demagnetization period Df to less than 1/10.

・Although the connection between the demagnetization period D and the detailed demagnetization period Df is set to 0.005 seconds, it should be changed to 0.03 to 0.05 seconds.

- In the present embodiment, the demagnetization period D and the detailed demagnetization period Df are used, but a change is made to add the detailed demagnetization period Dfx.

In the present embodiment, the detailed degaussing pulse width gradually decreases by 1 pulse width in the detailed degaussing period Df.

・This demagnetization method must be applicable to chucks that use electric permanent magnets.

The degaussing method of the present invention is not limited to electromagnetic chucks that serve to retain material on various machine tools during machining, but is also applicable to electro-permanent magnet chucks. be.

1 electromagnetic chuck 2 iron core 3 coil (winding)
4 Face plate 5 Work (target for demagnetization)
6 separator 7, 8 magnetic pole 9 conducting wire 10 control device 11 rectifier (bridge diode)
12 Current limiting resistor 13 Capacitor 14-17 Power MOSFET
18-21 Snubber circuit (surge absorber)
22 Manual operation control unit 23 External manual (or automatic) control unit 100 Commercial power supply

The present invention relates to a method of demagnetizing a magnetized magnetic material, and in particular, when applying an alternating DC pulse voltage to the coil of an electromagnetic chuck, the workpiece is demagnetized by flowing a demagnetizing current while changing the polarity of the gradually decreasing DC pulse voltage. It is about how to

The electromagnetic chuck is activated by the initial operation of magnetizing the electromagnetic chuck by passing an electric current through the coil, and in this state it is possible to retain a piece of metal made of magnetic material by the action of magnetic attraction. After that, the current supply to the coil is maintained while the electromagnetic chuck is in use. Then, the electromagnetic chuck is deactivated by degaussing the coil by supplying a reverse current to the coil, and the metal piece that has been held until then is released.

A work material made of a magnetic material must be reliably magnetized when it is processed. However, if magnetism remains even when degaussing is performed after work and the work material is removed, the work material cannot be removed. In addition, since it is often necessary to demagnetize the removed work material, it is necessary to demagnetize the work material.

In order to demagnetize an object to be demagnetized, including the work piece as described above, the object to be demagnetized must be demagnetized while its position is fixed. The following methods are available for demagnetizing an object to be demagnetized while its position is fixed.

A method in which a damped oscillating current is formed by an LC resonance circuit of a capacitor and a coil, and the object to be demagnetized is fixed in position and demagnetized.

Full-wave rectification of the AC power supply, demagnetization pulse with a first demagnetization pulse width that is a multiple of the demagnetization period at a demagnetization period (0.01 second or 0.00833 second) that is half the AC power frequency (50 Hz or 60 Hz). A demagnetization method that applies a DC voltage pulse that is applied to the coil and attenuates while switching the polarity until the pulse width reaches 0.01 seconds or 0.00833 seconds (for example, see Patent Document 1, hereinafter referred to as "pulse voltage type" ).

A method of demagnetizing an object to be demagnetized while keeping its position fixed by creating a DC reversal damping current. Conventionally, it was used in laboratories and was used as a method of complete demagnetization in which the current was gradually attenuated to zero over several minutes to completely eliminate the magnetism. A commercially available demagnetizer will attenuate a DC reversal current of several hertz over a period of about one minute.

A degaussing method in which a DC voltage is alternately applied to a coil, and an alternating current whose current peak value decreases sequentially linearly from a predetermined value is applied to demagnetize, or a demagnetizing method in which a decaying alternating current is applied to the coil (for example, Patent Document 2 Reference, hereinafter referred to as "current type").

JP-A-10-229014 JP-A-04-114413

The above-mentioned pulse voltage type demagnetization requires a long demagnetization time of about 8 seconds. With automation of equipment, reduction of demagnetization time is required.

On the other hand, since the current type switches the polarity by comparing the set current value and the current current value, there is a limit to discrimination of minute signals, depending on the performance of the comparator. Also, there is a problem that the demagnetization time changes when the object to be demagnetized changes.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to complete demagnetization in a short period of time with little residual magnetism in the minute output pulse system.

In order to solve the above-mentioned problems, the present invention provides a method of performing excitation by applying an alternating magnetic field using a coil of an electromagnetic chuck, wherein a commercial power source is stored in a capacitor in the coil, and 1.1. A 414 times DC voltage is alternately applied as a pulse voltage with the passage of time, and a pulse voltage that is successively attenuated by setting the pulse width of the first wave of demagnetization and the attenuation rate of the alternating pulse is applied. An alternating current whose current peak value gradually decreases linearly is applied, and when the pulse voltage width to be applied becomes 0.01 seconds or less, the minimum pulse width as a reference is switched to 1/10 or less, and a 0.01 second pulse is generated. A demagnetization method characterized by applying a voltage pulse with a pulse width of 0.0005 seconds to a coil to apply a minute alternating decay current to the coil of an electromagnetic chuck.

The present invention has the following effects. In the invention according to claim 1, as a method of demagnetizing by alternately switching and applying a DC voltage to the excitation coil, the pulse width is attenuated from the first demagnetization pulse width according to the attenuation rate setting value, thereby demagnetizing sequentially and linearly. When the current is reduced and the demagnetization pulse width becomes 0.01 seconds or less, a minute demagnetization current that alternates with a finely reduced pulse width of 1/10 or less is passed through the coil to demagnetize the object, even if the object is voluminous. Alternatively, even if the object is strongly magnetized, the inside of the object can be demagnetized satisfactorily.

In the invention according to claim 2, the gradually decreasing demagnetizing pulse voltage output is output as a continuous pulse group without breaks, thereby suppressing the noise generated by the back electromotive force generated from the coil and improving the demagnetizing performance. there is

It is a figure explaining the structure of the apparatus for enforcing the degaussing method based on this invention. 1 is a control block diagram of an apparatus for carrying out a demagnetization method according to the present invention; FIG. 4 is a graph of demagnetization voltage waveforms for carrying out the demagnetization method according to the present invention; 4 is a graph of a demagnetizing current waveform for carrying out the demagnetizing method according to the present invention; 4 is a graph of detailed voltage waveforms for carrying out the demagnetization method according to the present invention; 4 is a graph of detailed voltage waveforms for carrying out the demagnetization method according to the present invention; 1 is a principle diagram showing the strength of voltage and current; FIG. FIG. 4 is a relational diagram of various generated pulse output voltages and currents for carrying out the demagnetization method according to the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In the demagnetization method according to the present invention, a demagnetization period D, which is a first demagnetization period, and a detailed demagnetization period Df, which is a second demagnetization period continuous with the demagnetization period D, are set in advance. Efficient demagnetization is realized by applying a detailed demagnetization pulse during the detailed demagnetization period Df. That is, when the width of the attenuated degaussing pulse in the degaussing period D becomes twice the basic pulse width, the detailed degaussing period Df is entered to add a detailed demagnetizing pulse train that becomes a reduced reference pulse with a reduced basic pulse width. Therefore, it is possible to obtain good demagnetization performance in a short demagnetization time.

In the present invention, the value of the basic pulse width is not limited, and it is preferable to appropriately set the value corresponding to conditions such as the target demagnetization time.

FIG. 1 shows an outline of an apparatus for carrying out the demagnetization method according to the present invention, which includes an electromagnetic chuck 1 capable of holding a workpiece (metal piece) 5 so that it does not move during machining, and a control device 10. It is. The electromagnetic chuck 1 is composed of a winding wire (hereinafter referred to as a coil) 3 with a small resistance and an iron core 2. When an electric current is supplied to the coil 3 from a conducting wire 9, an electric current is generated on the face plate 4 of the electromagnetic chuck 1 via a separator 6. As a result, magnetic fluxes of the north pole 7 and the south pole 8 are generated in the magnetic poles forming the face plate 4 (the polarity of the magnetic poles alternates depending on the direction of the current flowing through the coil). A conductor 9 connected to the coil 3 of the electromagnetic chuck 1 is connected to a controller 10 for magnetizing and demagnetizing the magnetic poles N and S of the face plate 4 .

FIG. 2 is a diagram showing the configuration of the control device 10. As shown in FIG. AC power supplied from a commercial power supply 100 is full-wave rectified via a rectifier (bridge diode) 11 and charged in a capacitor 13 via a current limiting resistor 12 and the like. The DC voltage charged in the capacitor 13 becomes the peak value of the commercial AC power supply (1.414 times the commercial AC voltage). When the gates of the power MOSFETs 14 and 17 are turned on by control signals from the power MOSFETs 14 to 17 and the PWM output control unit 30, which combine this DC voltage into an H bridge, a forward current flows through the coil 3 of the electromagnetic chuck 1. , sucks the workpiece 5 on the face plate 4 .

When the gates of the power MOSFET 15 and the power MOSFET 16 are turned on, a current flows in the coil 3 of the electromagnetic chuck 1 in the negative direction, demagnetizing the workpiece 5 on the face plate 4 . The controllers of these four power MOSFETs 14-17 and snubber circuits 18-21 are connected to the control electronics inside the controller 10, and the controller 10 has a manual operation controller 22 or an external manual (or automatic ) is connected to the control unit 23 . Using the manual operation control unit 22 or the external manual (or automatic) control unit 23, the operator can magnetize the magnetic poles to the N pole 8 and the S pole 7 to put the electromagnetic chuck into a magnetized state or to put it in a demagnetized state. You can choose to

Next, an embodiment of the demagnetization method according to the present invention will be specifically described. In this embodiment, a pulse voltage is applied to the coil 3 of the electromagnetic chuck 1 by a pulse group in which a plurality of pulses are continuous.

FIG. 3 shows an outline of transition of the demagnetizing voltage during the demagnetizing operation. In the figure, the horizontal axis represents the time t, and the vertical axis represents the applied voltage value, that is, the attenuating demagnetizing pulse voltage applied to the coil 3. FIG. More specifically, the degaussing of the electromagnetic chuck 1 is performed by applying a first degaussing pulse T1, a second degaussing pulse T2, . This is done by applying a number of successive demagnetizing pulse trains to the coil 3 .

The total number of degaussing pulse trains is 20 to 60-odd. Each demagnetizing pulse T1, T2, . On the other hand, the sign changes between one demagnetizing pulse and the next demagnetizing pulse. That is, the N1 pulse signs of the first demagnetizing pulse train T1 are all negative pulses, the signs of the N2 pulses of the second demagnetizing pulse train T2 are all positive pulses, and the third demagnetizing pulse train T3 is The signs of the N3 pulses are all negative pulses, the signs of the N4 pulses of the fourth demagnetizing pulse train T4 are all positive pulses, and so on.

Furthermore, the current pulse intensities I1, I2, . In between, it decreases, for example linearly, according to a certain mathematically defined law.

The positive demagnetizing pulse trains T2, T4, T6, . , and the negative demagnetizing pulses T1, T3, T5, .

FIG. 5 shows the waveform from the initial demagnetizing pulse voltage T1 during the demagnetizing period D to the final demagnetizing pulse voltage Tn , and FIG. A pulse voltage waveform up to the final detailed demagnetizing pulse Tn+20 is shown. Also, FIG. 4 shows the exciting current waveform of the exciting current I of the pulse voltages of the demagnetizing pulses T1 to Tn+m.

As shown in these figures, in this embodiment, the DC voltage stored in the capacitor 13 is 1.414 times that of the commercial power supply, so that a cycle independent of the power supply frequency can be realized at the PWM frequency. For example, the basic demagnetizing pulse is generated based on the basic period of 0.005 seconds of the basic demagnetizing pulse preset in the demagnetizing period D, and the basic detailed demagnetizing pulse in the detailed demagnetizing period Df has a basic period of 1/10 of the basic period of the basic demagnetizing pulse. Generated based on 0.0005 seconds.

If the demagnetizing pulse T1 of the demagnetizing period D is set as the first demagnetizing pulse with m1 times the fundamental period of 0.005 seconds, the second demagnetizing pulse T2 will be the value obtained by multiplying the fundamental period of the first demagnetizing pulse T1 by the attenuation factor. . By being multiplied by the set attenuation rate, the demagnetization pulse gradually decreases in pulse width until the pulse width reaches 0.01 seconds (twice the basic period), after which it shifts to the detailed demagnetization period Df. . Incidentally, the value of the attenuation rate is not limited, and it is preferable to set it appropriately corresponding to the target demagnetization time.

In the shifted detailed demagnetization period Df, the first detailed demagnetization pulse generates a demagnetization pulse of 0.01 sec with 20 pulses based on the basic period of the demagnetization pulse of 0.0005 sec, and the first demagnetization pulse of 0.01 sec with 20 pulses. Output from the fine degauss pulse to the final fine degauss pulse of 0.0005 seconds.

FIG. 5 further shows that when the electromagnetic chuck 1 is magnetized, the same control device 10 is used to apply a positive pulse train MAG to the gates of the power MOSFETs 14 and 17 from the PWM output control unit 30 to the coil 3 surrounding the iron core 2. It shows that it can be adsorbed by An OFF time during which the electromagnetic chuck 1 is not energized is interposed between the end of the magnetization period and the beginning of the demagnetization period D.

The voltage and current intensity at the time of pulse output during magnetization or demagnetization period D are based on the principle shown in FIG. ) is controlled by the PWM output controller 30 .

More specifically, FIG. 8(a) shows a single ON pulse of 0.005 seconds×10 (=0.05 seconds) applied to the gates of the power MOSFETs 15 and 16 corresponding to the pulse train at the beginning of the demagnetization process. shows the variation of the voltage and current intensity I of .

FIG. 8(b) shows the voltage and current intensity of a single pulse when ON for 0.005 seconds×2 (=0.01 seconds) at the gates of the power MOSFETs 15 and 16 corresponding to the pulse train at the beginning of the demagnetization process. shows the change in height I.

FIG. 8(c) shows the voltage and current intensity of a single pulse when ON for 0.0005 seconds×10 (=0.005 seconds) at the gates of the power MOSFETs 15 and 16 corresponding to the pulse train at the beginning of the demagnetization process. shows the change in height I.

FIG. 8(d) shows the voltage and current intensity of a single pulse when ON for 0.0005 seconds×1 (=0.0005 seconds) at the gates of the power MOSFETs 15 and 16 corresponding to the pulse train at the beginning of the demagnetization process. shows the change in height I.

As shown in FIG. 8, the demagnetizing pulse width in the demagnetizing period D can be set by increasing or decreasing the demagnetizing current value reaching the rated current of the coil 3 by controlling the ON time of the gates of the power MOSFETs 15 and 16 . The demagnetizing current gradually decreases corresponding to the preset attenuation rate while changing the polarity, and when it reaches 0.01 sec, it shifts to the detailed demagnetizing period mode where the basic pulse becomes 0.0005 sec, and 0.01 sec (0 The first detailed demagnetizing pulse of 0.0005 seconds×20) is generated, and the detailed demagnetizing pulse gradually decays by 0.0005 seconds, and is finally output until a pulse of 0.0005 seconds is applied.

The invention is not limited to the one embodiment of the demagnetization method described above, by way of example, with reference to the accompanying drawings. Rather, the invention includes uses of all versions and adaptations based on the same principles. In particular, the following can be done without departing from the scope of the invention.

・Change the basic period of the demagnetizing pulse in the demagnetizing period D to less than 0.0005 seconds.

- Change the basic period of the detailed demagnetization period Df to less than 1/10.

・Although the connection between the demagnetization period D and the detailed demagnetization period Df is set to 0.005 seconds, it should be changed to 0.03 to 0.05 seconds.

- In the present embodiment, the demagnetization period D and the detailed demagnetization period Df are used, but a change is made to add the detailed demagnetization period Dfx.

In the present embodiment, the detailed degaussing pulse width is gradually reduced by 1 pulse width in the detailed degaussing period Df.

・This demagnetization method must be applicable to chucks that use electric permanent magnets.

The degaussing method of the present invention is not limited to electromagnetic chucks, which are useful for holding material on various machine tools during machining, but can also be used with electro-permanent magnet chucks. be.

1 electromagnetic chuck 2 iron core 3 coil (winding)
4 Face plate 5 Work (target for demagnetization)
6 separator 7, 8 magnetic pole 9 conducting wire 10 control device 11 rectifier (bridge diode)
12 Current limiting resistor 13 Capacitor 14-17 Power MOSFET
18-21 Snubber circuit (surge absorber)
22 Manual operation control unit 23 External manual (or automatic) control unit 100 Commercial power supply

Claims (3)

When a DC voltage obtained by rectifying a commercial power supply is stored in a capacitor and an alternating positive and negative DC pulse voltage is applied to the coil of an electromagnetic chuck, an alternating demagnetizing current flows and an alternating magnetic field is generated. ,
A period for demagnetizing the object to be demagnetized is set in advance as a first demagnetization period and a second demagnetization period that is continuous with the first demagnetization period, and the pulse width is determined from an integral multiple of a reference pulse whose pulse width is set in advance and the pulse width of the reference pulse. and an integral multiple of the reduced reference pulse with a smaller width, respectively;
In the first degaussing period, a plurality of continuous reference pulses, the pulse width of the first degaussing pulse T1 being set to an integer multiple of the reference pulse, so that a demagnetizing current corresponding to the rated current of the electromagnetic chuck to be demagnetized can flow. and the second degaussing pulse T2 to the (n-1)th degaussing pulse Tn-1 obtained by sequentially attenuating the degaussing pulse T1 according to a preset attenuation rate, and the width is the reference alternately applying an n-th demagnetizing pulse Tn set equal to the pulse to the coil of the electromagnetic chuck;
when a demagnetization pulse Tn is applied to the coil of the electromagnetic chuck, the first demagnetization period is shifted to the second demagnetization period;
In the second demagnetization period, the (n+1)-th demagnetizing pulse Tn+1 consisting of a predetermined number (m) of consecutive reduced reference pulses and the (n+m)-th demagnetizing pulse obtained by subtracting the reduced demagnetizing pulse from the demagnetizing pulse Tn+1. By alternately applying pulses Tn+m to the coil of the electromagnetic chuck,
A demagnetizing method, wherein, during the second demagnetizing period, a demagnetizing pulse having a width shorter than that of the demagnetizing pulse during the first demagnetizing period is alternately applied to a coil of an electromagnetic chuck to demagnetize the object to be demagnetized. A method of demagnetizing by applying an alternating magnetic field using a coil of an electromagnetic chuck to an object to be demagnetized,
In order to suppress the back electromotive force generated from the coil of the electromagnetic chuck due to the application of alternating current to the coil of the electromagnetic chuck,
A demagnetization method, wherein the applied pulse voltage is a pulse group consisting of a plurality of consecutive pulses, and the pulse voltage group obtained by alternating and attenuating the pulse group is applied to the chuck for excitation. A device for demagnetizing a magnetic body using an electromagnetic chuck that attracts the magnetic body,
a rectifier that rectifies AC power taken from a commercial power supply;
a capacitor connected to the rectifier;
a power MOSFET and a snubber circuit assembled in an H-bridge for applying the DC voltage charged in the capacitor to the coil of the electromagnetic chuck;
A PWM output control unit that controls the power MOSFET and the snubber circuit,
A degaussing device characterized by having

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