JP5033766B2 - Permanent electromagnetic chuck - Google Patents

Description

  The present invention relates to a permanent electromagnetic chuck. More specifically, the present invention includes a coil and a permanent magnet. The present invention relates to a permanent electromagnetic chuck provided with magnetizing means for passing a direct current and demagnetizing means for generating a damped alternating magnetic field in the coil so as to demagnetize the magnetic force guided to the work surface.

A permanent electromagnetic chuck provided with a coil and a permanent magnet is described, for example, in Patent Document 1 below. Such a permanent electromagnetic chuck is shown in FIG. 9A is a plan view of the permanent electromagnetic chuck, and FIG. 9B is a longitudinal sectional view thereof.
In the permanent electromagnetic chuck shown in FIG. 9, an iron core 104 around which a coil 106 is wound is erected on each of a plurality of permanent magnets 102, 102,. The upper end surface of the iron core 104 is a work surface on which the suction article 110 is placed.
The permanent magnet 102, the iron core 104, and the coil 106 are partitioned from adjacent ones by a partition plate 108. The upper end surface of the partition plate 108 is also a work surface on which the suction article 110 is placed.
Japanese Utility Model Publication No.7-112243

In the permanent electromagnetic chuck shown in FIG. 9, a direct current is applied to each of the coils 106, 106,... So that the magnetic force of the permanent magnets 102, 102,. By supplying a current, the adsorbed article 110 can be adsorbed.
In this way, even after the adsorption article 110 is adsorbed on the work surface, the adsorption state of the adsorption article 110 can be maintained even if the application of the direct current to the coils 106, 106,.
On the other hand, the demagnetization of the magnetic force guided to the work surface is performed by alternately switching the direction of direct current flow to the coils 106, 106... To generate a damped alternating magnetic field in each of the coils 106, 106. ing.

However, with the permanent electromagnetic chuck shown in FIG. 9, it is extremely difficult to adjust the suction force for the suction article placed on the work surface.
That is, the magnetization curve of the permanent electromagnetic chuck is shown in FIG. In the permanent electromagnetic chuck exhibiting such a magnetization curve, the attractive force can be adjusted within the demagnetization range shown in the upper left of the magnetization curve shown in FIG.
However, in this demagnetization range, the slope of the magnetization curve is not linear, and it is difficult to adjust it.
However, the permanent electromagnetic chuck has an advantage that the adsorption can be maintained even if the direct current applied to the coil is stopped after the adsorption article is adsorbed, and the adsorption can be maintained even during a power failure. Further, the coil can be energized in a short time, and there is an advantage that a decrease in accuracy due to heat generation due to the energization of the coil for a long time can be avoided.
Therefore, the problem of the present invention is to solve the problem of the conventional permanent electromagnetic chuck that the adsorption force of the adsorption article cannot be easily adjusted, and the permanent electromagnetic that can easily adjust the adsorption force of the adsorption article. It is to provide a chuck.

In order to solve the above problems, the inventors have applied a direct current to the coil to generate the maximum adsorption force on the work surface, and then reduce the magnetic force guided to the mounting plate with respect to the coil. It was found that the attracting force of the permanent electromagnetic chuck can be adjusted by energizing the DC current for a predetermined time in the direction opposite to the direction of energizing the coil of the direct current that generates the maximum attracting force.
However, adjusting the energizing time of the direct current that energizes the coil in the direction of reducing the magnetic force guided to the work surface by using a timer means that the demagnetizing range of the permanent electric chuck is as shown in the magnetization curve of FIG. Thus, it has been found that the slope of the magnetization curve is not linear, it is extremely difficult to obtain a desired adsorption force, and variations in the adjusted adsorption force are likely to occur.
For this reason, the present inventors examined whether the adsorption force of the permanent electromagnetic chuck can be easily adjusted, and whether the adjusted adsorption force can be reduced in variation. As a result, a pulse signal synchronized with the cycle of the alternating current is received, and a rectifier circuit driving circuit for driving a rectifying circuit for full-wave rectification of the alternating current is provided, and magnetized so as to generate the maximum attractive force on the work surface. For the permanent electromagnetic chuck, a predetermined number of pulse signals synchronized with the AC current cycle are transmitted to the rectifier circuit drive circuit to drive the rectifier circuit, and the direct current output without smoothing from the rectifier circuit The present inventors have found that a desired attracting force can be easily obtained by switching the current to the coil and demagnetizing the magnetic force guided to the work surface.

  In other words, the present invention includes a coil and a permanent magnet, and a coil that is energized with a direct current so as to generate an attracting force by guiding the magnetic force of the permanent magnet to a work surface on which the attracting article is placed. A permanent electromagnetic chuck provided with a magnetic means and a demagnetizing means for generating a damped alternating magnetic field in the coil so as to demagnetize the magnetic force guided to the work surface, and full-wave rectified alternating current A rectifier circuit that outputs a direct current without smoothing; a polarity switching circuit that switches a current-carrying direction of the direct-current current output from the rectifier circuit in synchronization with a cycle of the alternating current; A rectifier circuit drive circuit that receives a pulse signal synchronized with a cycle and drives the rectifier circuit; and a control unit that controls the polarity switching circuit and the rectifier circuit drive circuit, wherein the control unit includes the coil In A coil of direct current from the rectifier circuit is generated so that a reverse magnetic force is generated in the coil in a direction of reducing the magnetic force of the work surface where the maximum attraction force is generated by applying a direct current from the flow circuit. The polarity switching circuit switches the energization direction in synchronization with the AC current cycle, and sends a predetermined number of pulse signals synchronized with the AC current cycle to the rectifier circuit drive circuit, to the pulse signal The polarity switching circuit and the rectifier circuit drive so that a corresponding direct current is passed from the rectifier circuit to the coil via the polarity switching circuit, and the magnetic force of the work surface is demagnetized and adjusted to a desired attracting force. A permanent electromagnetic chuck characterized by controlling a circuit.

In the present invention, the control unit is provided with an output synchronization unit that transmits a predetermined signal to each of the polarity switching circuit and the rectifier circuit driving circuit in synchronization with the cycle of the alternating current, and the polarity is output from the output synchronization unit. A switching signal for switching the energization direction of the DC current output from the rectifier circuit to the coil is transmitted to the switching circuit, and a predetermined number of pulse signals for driving the rectifier circuit are transmitted to the rectifier circuit driving circuit. Thus, the polarity switching circuit and the rectifier circuit driving circuit can be easily controlled.
Further, the control unit is a demagnetization pattern showing the relationship between the attractive force and the magnetic force adjustment scale graduated at equal intervals, and the number of pulse signals transmitted to the rectifier circuit driving circuit corresponding to the magnetic force adjustment scale Is provided with a storage unit that stores a demagnetization pattern defined by the input unit and an input unit that inputs the scale of the magnetic force adjustment scale to the control unit, and corresponds to the scale of the magnetic force adjustment scale that is input from the input unit based on the maximum attraction force. According to the demagnetization pattern, a predetermined number of pulse signals are transmitted from the control unit to the rectifier circuit driving circuit in synchronism with the cycle of the alternating current so as to adjust to the attractive force. be able to.
A plurality of demagnetization patterns are stored in the storage unit, and a demagnetization pattern selection unit that selects one of the demagnetization patterns and inputs the demagnetization pattern is provided. The resulting demagnetization pattern can be selected.

In the permanent electromagnetic chuck according to the present invention, the direct current output without smoothing by full-wave rectifying the alternating current with the rectifier circuit is passed through the coil and led to the work surface of the suction article that has generated the maximum suction force. The direction of energization of the DC current output from the rectifier circuit to the coil is switched in synchronism with the surroundings of the AC current by the polarity switching circuit so that a reverse magnetic force that reduces the magnetic force is generated in the coil. In synchronization with the current cycle, a predetermined number of pulse signals are transmitted to the rectifier circuit drive circuit to drive the rectifier circuit. For this reason, the DC current output from the rectifier circuit in synchronization with the AC current cycle is supplied to the coil via the polarity switching circuit, thereby demagnetizing the magnetic force on the work surface and adjusting it to the desired attractive force. it can.
In this way, the demagnetization of the magnetic force on the work surface is performed by energizing the coil with a direct current output without being smoothed from a rectifier circuit driven in response to a pulse signal synchronized with the cycle of the alternating current. As a result, it is possible to accurately adjust the suction force on the work surface as compared with the case where the energization time of the direct current energizing the coil is regulated by a timer.

An example of the permanent electromagnetic chuck according to the present invention is shown in FIG. 1A is a partial cross-sectional front view of the permanent electromagnetic chuck, FIG. 1B is a cross-sectional view taken along the line OA of FIG. 1A, and FIG. 1C is FIG. It is sectional drawing in the OB line of a).
In the permanent electromagnetic chuck shown in FIG. 1, magnet portions 10, 10... Are radially arranged on a circular main body portion 16. As shown in FIGS. 1 (a) and 1 (b), the magnet portion 10 has an coil 14 wound around an alnico magnet 12 as a permanent magnet. A spacer 18 is placed on the alnico magnet 12, and a placing plate 20 is placed on the entire surface of the magnet portions 10, 10,.
In the mounting plate 20, a portion corresponding to the magnet unit 10 is surrounded by a separator 22.
In addition, the adjacent magnet parts 10 and 10 are divided by the partition part 24 formed in the main-body part 16, as shown in FIG.1 (c).

The coil 14 shown in FIG. 1 is energized via the polarity switching circuit 32, as shown in FIG. 2, with the direct current outputted without full-wave rectification and smoothing of the alternating current by the rectifier circuit 30. .
The rectifier circuit 30 is constituted by a thyristor and is driven by a rectifier circuit drive circuit 34.
In addition, the polarity switching circuit 32 increases the magnetic force of the alnico magnet 12 so that the direct current output without being smoothed from the rectifier circuit 30 generates an attracting force on the work surface of the mounting plate 20. The direction is switched between an energization direction for generating a positive magnetic force in the coil 14 and an energization direction for generating a reverse magnetic force that demagnetizes the magnetic force of the alnico magnet 12 so as to reduce the attractive force generated on the work surface of the mounting plate 20.
The polarity switching circuit 32 and the rectifier circuit driving circuit 34 are controlled by the control unit 36.
The control unit 36 includes a cycle count unit 38 that counts the cycle of the alternating current rectified by the rectifier circuit 30 detected by the cycle detection circuit 35, and a rectifier in synchronization with the cycle counted by the cycle count unit 38. An output synchronization unit 40 that transmits a predetermined signal to the circuit drive circuit 34 and the polarity switching circuit 32 is provided. Further, the control unit 36 is provided with a first storage unit 42 that stores demagnetization pattern data and a second storage unit 44 that stores demagnetization pattern data.
As input means for inputting to the control section 36, as will be described later, an input means 45 for designating a magnetic force adjustment scale of a demagnetization pattern stored in the first storage section 42 and inputting a magnetization command, and a first storage An input means 46 for inputting a demagnetization pattern selection command for selecting one of a plurality of demagnetization patterns stored in the unit 42 and an input means 48 for inputting a demagnetization command are provided.

FIG. 3 shows current waveforms at locations indicated by (A) to (E) in the block diagram shown in FIG. In the rectifier circuit 30 shown in the block diagram of FIG. 2, the alternating current shown in FIG. 3A is full-wave rectified and smoothed, and the direct current having the waveform shown in FIG. May be output). The rectifier circuit 30 is driven by a rectifier circuit drive circuit 34. The rectifier circuit driving circuit 34 is a pulse shown in FIG. 3C, which is transmitted from the output synchronization unit 40 in synchronization with the cycle of the alternating current detected by the cycle detection circuit 35 and counted by the cycle counting unit 38. When the signal is received, the rectifier circuit 30 is driven. For this reason, as shown in FIG. 3C, when the pulse signal is not transmitted from the output synchronization unit 40 to the rectifier circuit drive circuit 34, the direct current is output from the rectifier circuit 30 as shown in FIG. Not output.
As shown in FIG. 3E, the output synchronization unit 40 sends a switching signal for switching the direction of energization of the DC current output from the rectifier circuit 30 to the polarity switching circuit 32. It is transmitted in synchronization with the period. When this switching signal is a positive signal for energizing (positively energizing) a DC current in the direction in which the magnetic force of the alnico magnet 12 is increased, the waveform of the DC current via the polarity switching circuit 32 is as shown in FIG. As shown to (D), it is the same direction as the waveform of the direct current output from the rectifier circuit 30. On the other hand, as shown in FIG. 3E, the switching signal transmitted from the output synchronization unit 40 is a reverse signal that energizes (reversely energizes) the DC current in the direction in which the magnetic force of the alnico magnet 12 is demagnetized. If there is, the waveform of the direct current passing through the polarity switching circuit 32 is opposite to the waveform of the direct current output from the rectifier circuit 30 as shown in FIG.

In the permanent electromagnetic chuck shown in FIG. 1 and FIG. 2, after the coil 14 is positively energized with a direct current output from the rectifier circuit 30 and magnetized so that the maximum attractive force is applied to the work surface of the mounting plate 20. When the magnetic force is demagnetized, a direct current corresponding to the number of pulse signals transmitted from the output synchronizer 40 to the rectifier circuit drive circuit 34 is switched by the polarity switching circuit 32 and the coil 14 is reversely energized. is doing.
In this way, by attracting the coil 14 with a direct current corresponding to the pulse signal from the output synchronization unit 40, the suction force on the work surface of the mounting plate 20 can be easily adjusted. This is shown in FIG. In FIG. 4, the DC current output from the rectifier circuit 30 is positively energized to the coil 14 to give the work surface of the mounting plate 20 the maximum adsorption force, and then the polarity switching circuit 32 switches the energization direction to reverse energization. 6 is a graph showing the relationship between the number of pulse signals from the output synchronization unit 40 and the suction force on the work surface of the placement plate 20 when adjusting the suction force on the work surface of the placement plate 20. At this time, the voltage of the direct current was constant. The waveform of the direct current output from the rectifier circuit 30 corresponds to this pulse signal at 1: 1 as shown in FIG.

On the other hand, when adjusting the attraction force on the work surface of the mounting plate 20, a case where the current value (or voltage value) of the direct current from the rectifier circuit 30 that reversely energizes the coil 14 is changed and adjusted is shown in FIG. Shown in 5 (a). In FIG. 5A, the horizontal axis represents magnetomotive force [AT (ampere turn)] caused by reverse energization of the coil 14. Further, when the magnetomotive force is further increased after the attraction force has reached the minimum value, the polarity is reversed and re-magnetized in the permanent electromagnetic chuck, and the attraction force is increased again.
As is clear from FIG. 5A, the relationship between the magnetomotive force and the attractive force in the attractive force adjustment region is not a linear relationship, and the region where the change rate of the attractive force with respect to the change of the magnetomotive force is small and the large region Coexist. For this reason, it is difficult to adjust the attracting force by changing the current value (or voltage value) of the direct current that reversely energizes the coil 14.
In addition, when adjusting the energizing time of the direct current output from the rectifier circuit 30 without being smoothed by the timer to adjust the attracting force on the work surface of the mounting plate 20, FIG. As shown in FIG. 6, a part of the direct current (part of the direct current peak) may be cut at one or both of the time when the timer is turned on and the time when the timer is turned on. In this way, when a part of the peak of the direct current is cut, as shown in FIG. 4, the change rate of the adsorption force per pulse in the region where the number of pulses is small (in other words, the direct current 1 In the region where the change ratio per mountain) is large, the influence on the adsorption amount becomes large. For this reason, as shown in FIG. 5B, when the energization amount to the coil 14 is adjusted by a timer in which a part of the waveform of the direct current is cut, the adjusted attracting force is likely to vary.
In this respect, the direct current output from the rectifier circuit 30 without being smoothed corresponds to the pulse signal from the output synchronization unit 40 as shown in FIG. For this reason, it is possible to accurately control the amount of DC current that is reversely energized to the coil 14 by the number of pulse signals, and as shown in FIG. Variation can be reduced as much as possible.

In the permanent electromagnetic chuck shown in FIGS. 1 and 2, a plurality of demagnetization patterns are stored in the first storage unit 42 as shown in FIG. Each of the demagnetization patterns is a demagnetization pattern indicating the relationship between the attractive force and the magnetic force adjustment scale graduated at equal intervals, and is a pulse transmitted to the rectifier circuit drive circuit 34 corresponding to the magnetic force adjustment scale. The number of signals is fixed. The number of pulse signals can be determined from the relationship between the attractive force and the number of pulse signals shown in FIG.
Therefore, by selecting a predetermined pattern from the plurality of demagnetization patterns shown in FIG. 6 and designating the magnetic force adjustment scale, the attractive force on the work surface of the mounting plate 20 can be determined. This magnetic force adjustment scale cannot specify an intermediate area between the scale and the scale.
Such a pattern can be selected from the input means 46 shown in FIG. 2, and a magnetic force adjustment scale can be designated from the input means 45. The input means 45 can also send a magnetization command to the control unit 36.

In the control unit 36 that has received the magnetization command input from the input means 45, a positive signal as a switching signal is transmitted from the output synchronization unit 40 to the polarity switching circuit 32, and the period of the alternating current input to the rectifier circuit 30 is determined. In synchronism, the energizing direction of the DC current that is output from the rectifier circuit 30 without being smoothed is switched to the positive energizing, and the positive magnetic force in the direction of guiding the magnetic force to the work surface of the mounting plate 20 is applied to the coil 14. To occur.
Further, the control unit 36 drives the rectifier circuit 30 by transmitting a pulse signal to the rectifier circuit drive circuit 34 in synchronization with the cycle of the alternating current input to the rectifier circuit 30 from the output synchronization unit 40. A direct current output without being smoothed from 30 is positively energized to the coil 14 via the polarity switching circuit 32 to generate a positive magnetic force in the coil 14. Such a positive magnetic force increases the suction force of the work surface of the mounting plate 20 to the maximum suction force.
In this way, by making the adsorption force of the work surface of the mounting plate 20 the maximum adsorption force, even if there is residual magnetism on the mounting plate 20 or the like, the maximum adsorption force obtained is constant. is there.

Next, the control unit 36 selects a pattern input from the input unit 46 from the demagnetization patterns stored in the first storage unit 42 and corresponds to the magnetic force adjustment scale input from the input unit 45. Specify the number of pulse signals.
Further, in the control unit 36, a reverse signal as a switching signal is transmitted from the output synchronization unit 40 to the polarity switching circuit 32, and is smoothed from the rectification circuit 30 in synchronization with the cycle of the alternating current input to the rectification circuit 30. The energizing direction of the direct current that is output without switching is switched to reverse energization so that a reverse magnetic force that demagnetizes the magnetic force guided to the work surface of the mounting plate 20 is output from the coil 14.
Further, in response to the specified number of pulse signals, a pulse for driving the rectifier circuit 30 from the output synchronization unit 40 to the rectifier circuit 30 in synchronization with the cycle of the alternating current input to the rectifier circuit 30. The rectifier circuit 30 outputs a direct current corresponding to the pulse signal transmitted from the output synchronization unit 40. This DC current is reversely energized to the coil 14 via the polarity switching circuit 32 and generates a reverse magnetic force from the coil 14 that demagnetizes the magnetic force guided to the work surface of the mounting plate 20.
The pulse signal from the output synchronization unit 40 is transmitted until the number of pulse signals specified by the selected demagnetization pattern is reached. The number of pulse signals is counted by the period counting unit 38, and when a predetermined number of pulse signals are transmitted, the transmission of the pulse signal from the output synchronization unit 40 is stopped by the stop signal from the period counting unit 38. To do.
In this manner, the attractive force on the work surface of the mounting plate 20 can be set to the attractive force corresponding to the magnetic force adjustment scale of the selected demagnetization pattern.

As shown in FIG. 6, three types of demagnetization patterns are stored in the first storage unit 42 of the permanent electromagnetic chuck shown in FIGS. Pattern 1 is a pattern in which the magnetic force adjustment scale and the attractive force are linearly related. In Pattern 2, the adsorption force and the magnetic force adjustment scale are in a linear relationship with a gentle slope in the region where the adsorption force is high, and the adsorption force and the magnetic force adjustment scale change abruptly in the region where the adsorption force is low. It is the pattern of the relationship used as the curve form. On the other hand, the pattern 3 has a curved relationship in which the attractive force and the magnetic force adjustment scale change rapidly in the region where the attractive force is high, and the attractive force and the magnetic force adjustment scale are inclined in the region where the attractive force is low. A loose linear relationship pattern. Of these patterns, the pattern 2 is suitable for use in a region having a relatively high suction force, and the pattern 3 is suitable for use in a region having a relatively low suction force.
In FIG. 6, three types of demagnetization patterns are shown. However, one type of demagnetization pattern or a large number of three or more types of demagnetization patterns may be used.

In the permanent electromagnetic chuck shown in FIG. 1 and FIG. 2, the magnetic force guided to the work surface of the mounting plate 20 is used when the suction product placed on the work surface of the mounting plate 20 is taken out. Demagnetize with the residual magnetism.
In the demagnetization, the control unit 36 to which the demagnetization start command is input from the input unit 48 demagnetizes the magnetic force guided to the work surface of the mounting plate 20 by generating a damped alternating magnetic field in the coil 14. The polarity switching circuit 32 and the rectifier circuit driving circuit 34 are controlled. This control is performed according to the demagnetization pattern stored in the second storage unit 44.
FIG. 7 shows current waveforms at positions (B) to (E) in the block diagram shown in FIG. 2 when the demagnetization pattern is used. In FIG. 7, the waveform of the alternating current input to the rectifier circuit 30 is shown in FIG.
At the time of degaussing, as shown in FIG. 7C, a pulse signal is continuously transmitted from the output synchronization unit 40 to the rectifier circuit drive circuit 34 in synchronization with the cycle of the alternating current, and rectified. As shown in FIG. 7B, the circuit 30 continuously outputs a direct current without smoothing.
On the other hand, as shown in FIG. 7E, the polarity switching circuit 32 includes a positive signal as a switching signal for positively energizing the coil 14 with a direct current in the direction in which the magnetic force of the alnico magnet 12 is increased, and the alnico magnet 12. A reverse signal as a switching signal for reversely energizing the DC current to the coil 14 in the direction of demagnetizing the magnetic force is alternately transmitted from the output synchronization unit 40 in synchronization with the cycle of the AC current. The transmission time of the positive signal and the reverse signal is gradually shortened.
For this reason, as shown in FIG. 7D, the direct current supplied to the coil 14 is alternately switched between the direction in which the magnetic force of the alnico magnet 12 is demagnetized and the direction in which the magnetic force of the alnico magnet 12 is increased. As a result, a damped alternating magnetic field is generated in the coil 14.
As a result, as shown in FIG. 8, the magnetic force of the work surface of the mounting plate 20 is changed to (1) → (2) → (3) → (4) → (5) → (6) → (7) → ( 8) It can be demagnetized by gradually decreasing in the order of (9).

As described above, in the permanent electromagnetic chuck shown in FIGS. 1 and 2, a plurality of types of demagnetization patterns are stored in the first storage unit 42, but a type of demagnetization pattern is stored. May be. Alternatively, the first storage unit 42 may indicate the relationship between the adsorption force on the work surface of the mounting plate 20 illustrated in FIG. 4 and the number of pulse signals from the output synchronization unit 40 to the rectifier circuit drive circuit 34. Good.
Moreover, in the permanent electromagnetic chuck shown in FIG.1 and FIG.2, although the alnico magnet 12 is employ | adopted as a permanent magnet, a ferrite magnet may be sufficient.
Of course, the permanent electromagnetic chuck may have a rectangular shape as shown in FIG.

It is the fragmentary sectional front view and fragmentary sectional view of the permanent electromagnetic chuck which concern on this invention. It is a block diagram explaining the electric circuit of the permanent electromagnetic chuck shown in FIG. FIG. 3 is a waveform diagram showing current waveforms in the block diagram shown in FIG. 2. It is a graph which shows the relationship between the adsorption | suction force in a work surface, and the pulse signal transmitted to the rectifier circuit drive circuit 34 from the output synchronizer 40. It is a graph which shows the relationship between the attraction | suction force on a work surface, and a magnetomotive force. The demagnetization pattern memorize | stored in the 1st memory | storage part 42 shown in FIG. 1 is shown. FIG. 3 is a waveform diagram showing current waveforms in the block diagram shown in FIG. 2 when demagnetizing the magnetic force on the work surface of the permanent electromagnetic chuck shown in FIG. 1. It is explanatory drawing explaining the demagnetization of the magnetic force of the work surface of the permanent electromagnetic chuck shown in FIG. It is the fragmentary sectional top view and longitudinal cross-sectional view explaining the conventional permanent electromagnetic chuck. The magnetization curve of the conventional permanent electromagnetic chuck is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnet part 12 Alnico magnet 14 Coil 16 Main body part 18 Spacer 20 Mounting board 22 Separator 24 Partition part 30 Rectifier circuit 32 Polarity switching circuit 34 Rectifier circuit drive circuit 35 Period detection circuit 36 Control part 38 Period count part 40 Output synchronization part 42 First storage unit 44 Second storage unit 45, 46, 48 Input means

Claims (4)

A magnetizing means, comprising a coil and a permanent magnet, for passing a direct current through the coil so as to generate an attracting force by guiding the magnetic force of the permanent magnet to a work surface on which the attracted article is placed; A permanent electromagnetic chuck provided with demagnetizing means for generating a damped alternating magnetic field in the coil so as to demagnetize the magnetic force guided to the surface,
A rectifier circuit that outputs a DC current obtained by full-wave rectification of an AC current without smoothing, and a polarity switch that switches a direction of energization of the DC current output from the rectifier circuit to the coil in synchronization with the cycle of the AC current A circuit, a rectifier circuit driving circuit that receives the pulse signal synchronized with the cycle of the alternating current and drives the rectifier circuit, and a control unit that controls the polarity switching circuit and the rectifier circuit drive circuit,
In the control unit, a direct current is applied to the coil from a rectifier circuit so that a reverse magnetic force in a direction to reduce the magnetic force is generated in the coil with respect to the magnetic force of the work surface where the maximum adsorption force is generated. The direction of energization of the direct current from the rectifier circuit to the coil is switched in synchronization with the cycle of the alternating current by the polarity switching circuit
In addition, a predetermined number of pulse signals synchronized with the cycle of the alternating current are transmitted to the rectifier circuit driving circuit, and a direct current corresponding to the pulse signal is supplied from the rectifier circuit to the coil via the polarity switching circuit. A permanent electromagnetic chuck characterized in that the polarity switching circuit and the rectifier circuit driving circuit are controlled so that the magnetic force of the work surface is demagnetized and adjusted to a desired attracting force. The control unit is provided with an output synchronization unit that transmits a predetermined signal to each of the polarity switching circuit and the rectifier circuit driving circuit in synchronization with the cycle of the alternating current,
From the output synchronization unit, a switching signal for switching the direction of energization of the direct current output from the rectifier circuit to the coil is transmitted to the polarity switching circuit, and the rectifier circuit is driven to the rectifier circuit driving circuit. The permanent electromagnetic chuck according to claim 1, wherein a predetermined number of pulse signals are transmitted. The control unit is a demagnetization pattern showing the relationship between the attractive force and the magnetic force adjustment scale graduated at equal intervals, and the number of pulse signals transmitted to the rectifier circuit driving circuit corresponding to the magnetic force adjustment scale. A storage unit in which a predetermined demagnetization pattern is stored; and an input unit that inputs the scale of the magnetic force adjustment scale to the control unit;
In accordance with the demagnetization pattern, the control unit synchronizes with the rectifier circuit drive circuit in accordance with the period of the alternating current so that the maximum attractive force is adjusted to the attractive force corresponding to the scale of the magnetic force adjustment scale inputted from the input means. The permanent electromagnetic chuck according to claim 1, wherein a predetermined number of pulse signals are transmitted.   4. The permanent electromagnetic chuck according to claim 3, wherein a plurality of demagnetization patterns are stored in the storage unit, and a demagnetization pattern selection unit that selects one of the demagnetization patterns and inputs the selected one to the control unit.

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