JPH0569650B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to excitation of a magnetic chuck including an irreversible polarity permanent magnet, a plurality of reversible polarity permanent magnets, and a plurality of excitation coils for switching the polarity of the reversible polarity permanent magnets. Regarding equipment.

(Prior Art) Generally, an excitation device for a magnetic chuck including a plurality of reversible polarity permanent magnets, a plurality of irreversible polarity permanent magnets, and a plurality of excitation coils for switching the polarity of the irreversible polarity permanent magnets has a reversible polarity. An excitation current for switching the polarity of the permanent magnet is simultaneously supplied to each excitation coil.

However, in such an excitation device, a large amount of current flows at once, so the power supply capacity is large, and large-capacity circuit elements must be provided. is large, and furthermore, it is not possible to finely adjust the excitation current.

In addition, in the above-mentioned excitation device, the magnetic material attracted to the magnetic chuck is magnetized, and even if the magnetic chuck is switched to the inactive state, that is, the work surface that attracts the magnetic material is switched to the non-excited state, the magnetic material will not be attracted. You may not be able to remove the magnetic material from the magnetic chuck.

(Object of the invention) The present invention reduces the amount of excitation current that flows at a time, thereby reducing the power supply capacity, and by switching the work surface to a non-excited state, an alternating magnetic field acts on the magnetic material. The purpose is to allow the magnet to undergo a demagnetizing effect.

(Structure, Effects of the Invention) The present invention includes at least one irreversible polarity permanent magnet, a plurality of reversible polarity permanent magnets magnetically connected to the irreversible polarity permanent magnet by a common magnetic circuit member, and the irreversible polarity permanent magnet. An excitation device for a magnetic chuck including a plurality of excitation coils for switching the polarity of a permanent magnet for each magnet, the switching circuit for switching the polarity of an excitation current supplied to the excitation coil, and the irreversible polarity permanent magnet. The excitation coil is divided into a plurality of groups for switching the polarity of the polarity reversible permanent magnet that is magnetically connected in common to the excitation coil, and the excitation coil is sequentially selected with a pause time for each group to excite the excitation coil. The present invention is characterized in that it includes a selection circuit that supplies current to the excitation coil, and a control circuit that controls the switching circuit and the selection circuit.

According to the present invention, since the excitation current is sequentially supplied to the divided groups of excitation coils with a rest period, the amount of excitation current that flows at once is smaller than when the excitation current is supplied to all excitation coils at the same time. (The maximum value of the instantaneous excitation current becomes smaller), so the power supply capacity can be reduced accordingly, and even though the excitation current is not an alternating current, the excitation current that keeps the magnetic chuck in the non-operating state is excited. Each time it is supplied to the coil, a reverse magnetic field acts on the magnetic material, and the magnetic material is demagnetized.

(Example) Hereinafter, an example of the present invention shown in the drawings will be described.

The magnetic chuck 10 shown in FIGS. 1 to 3 includes a face plate 12, a housing 14 made of a magnetic material and open at one end, and a connecting body 1 disposed inside the housing.
6, a plurality of reversible polarity permanent magnets 18a, 18b arranged in the housing 14, and a plurality of excitation coils wound around the reversible polarity permanent magnets 18a, 18b to change the magnetization direction, that is, the polarity, of the reversible polarity permanent magnets. 20a, 20b, and an irreversible polarity permanent magnet 22 disposed within the housing 14.

The face plate 12 has a large number of elongated first and second magnetic pole pieces 26, 28, and a spacer 30 made of a plate-shaped non-magnetic material and arranged between the magnetic pole pieces. The first and second magnetic pole pieces 26 and 28 are arranged parallel to each other and alternately with a spacer 30 in between, and together with the spacer 30, the magnetic body 8
A working surface 32 is defined for adsorbing 6. The spacers 30 are arranged with their thickness directions aligned.

Each first pole piece 26, as shown in FIG.
It has a notch 34 at its longitudinal center, and each second pole piece 28 has notches 36 at both longitudinal ends, as shown in FIG. Each cutout portion 34, 36 is open toward the housing 14. Nonmagnetic members 38 and 40 are arranged in each of the notches 34 and 36, respectively.

The first and second magnetic pole pieces 26 , 28 , the spacer 30 and the non-magnetic members 38 , 40 are integrally coupled to form the face plate 12 , and the face plate 12 is formed so that each magnetic pole piece 26 , 28 has a width corresponding to the width of the housing 14 . They are arranged at the open end of the housing 14 so as to extend in the direction and to be spaced apart from one another in the longitudinal direction of the housing 14 .

The housing 14 has a bottom plate portion 42 arranged parallel to and spaced from the face plate 12, and a frame portion 44 located above the bottom plate portion. Two portions of the frame portion 44 extending in the width direction of the first and second magnetic pole pieces 26 and 28, that is, in the longitudinal direction of the face plate 12, are magnetically attached to both longitudinal ends of all the first magnetic pole pieces 26. connected to the non-magnetic member 40
It is magnetically insulated from all second pole pieces 28 by.

The connecting body 16 is disposed between the bottom plate portion 42 and the face plate 12 and is connected to the first and second magnetic pole pieces 26, 28.
It consists of two magnetic members 46 and 48 extending in the width direction. The magnetic member 46 is connected to the bottom plate portion 42 and the magnetic member 4
It is located between 8 and 8. The lower surface of the magnetic member 46 is magnetically connected to the bottom plate portion 42 by an irreversible polarity permanent magnet.

The magnetic member 48 has a width larger than that of the magnetic member 46 and is disposed between the magnetic member 46 and the face plate 12. Magnetic member 48
, all the first magnetic pole pieces 2 are connected by the non-magnetic member 38.
6, and is magnetically connected to the longitudinal center of all second pole pieces 28.

The polarity reversible permanent magnets 18a and 18b are attached to the bottom plate portion 4.
2 and the magnetic member 48 , and between the widthwise end of the magnetic member 46 and the frame portion 44 . One magnetic pole surface of the reversible permanent magnets 18a, 18b magnetically contacts the inner surface of the frame portion 44, and the other magnetic pole surface magnetically contacts the widthwise end surface of the magnetic member 46. For this reason, the polarity reversible permanent magnets 18a, 1
One magnetic pole face of 8b is magnetically connected to the first magnetic pole piece 26 via the frame portion 44, and the other magnetic pole face is magnetically connected to the second magnetic pole piece 28 via the connecting body 16.

The polarity reversible permanent magnets 18a and 18b are low coercive force magnets such as alnico magnets, and therefore their magnetization directions, that is, the positions of their N and S poles, are reversed by an external magnetic field. In addition, the polarity reversible permanent magnet 18
In the illustrated example, a, 18b are excitation coils 20a,
20b connects the first and second pole pieces 26, 28
magnetized in a direction parallel to the longitudinal direction of the The magnetization direction, that is, the magnetic polarity, of the reversible polarity permanent magnets 18a, 18b is determined by passing a pulse-like DC current through the excitation coils 20a, 20b for a short period of time, and causing the reversible polarity permanent magnets 18a, 18b to have an external magnetic field in the direction opposite to the direction of the magnetic lines of force. It can be reversed by applying a magnetic field.

As shown in FIG. 4, the excitation coils 20a and 20b are divided into a first group 20a and a second group 20b and are connected to an excitation device 50, respectively. A direct current is supplied to the coils 20a, 20b such that the magnetic pole faces of the reversible permanent magnets 18a, 18b on the magnetic member 46 side have the same polarity.
The excitation coils 20a, 20b may be divided into three or more groups, or one coil group may be composed of a single excitation coil.

The illustrated magnetic chuck 10 is a so-called one magnetic circuit magnetic chuck in which all the reversible permanent magnets 18a and 18b are magnetically connected to all the irreversible permanent magnets 22 via the magnetic member 46 and the housing 14. Therefore, each excitation coil is divided into a first group 20a and a second group 20b, but when the magnetic chuck is divided into multiple magnetic circuits, a plurality of polarity irreversible permanent magnets are installed in each magnetic circuit. The excitation coil that is arranged to reverse the magnetization direction of the reversible permanent magnet may be divided into a first group and a second group.

In other words, in the case of a magnetic chuck that has a plurality of pairs of irreversible polarity permanent magnets and irreversible polarity permanent magnets that are magnetically connected in common (having a plurality of magnetic circuits), each magnetic circuit has a plurality of polarity reversible permanent magnets. It is sufficient to arrange permanent magnets and excitation coils therefor, and to divide the excitation coils of each magnetic circuit into a first group and a second group.

The irreversible polarity permanent magnet 22 is a plate-shaped magnet having a high coercive force, such as a rare earth metal magnet or a ferrite magnet, and its polarity, that is, the positions of its N and S poles, cannot be reversed by an external magnetic field. The polarity irreversible permanent magnet 22 is arranged between the bottom plate part 42 and the magnetic member 46, and one magnetic pole surface contacts the upper surface of the bottom plate part 42, and the other magnetic pole surface contacts the magnetic member 4.
Contact the bottom surface of 6. In the following description, it is assumed that the polarity irreversible permanent magnet 22 has an N magnetic pole face on the housing 14 side and an S magnetic pole face on the magnetic member 46 side.

Note that a second polarity irreversible permanent magnet may be arranged between the first and second magnetic poles 26 and 28, respectively. In this case, the second polarity irreversible permanent magnet is a plate-shaped magnet having a high coercive force, such as a rare earth metal magnet or a ferrite magnet, and is magnetized in its thickness direction, with magnetic pole faces of the same polarity facing each other. In addition, it is arranged so as to apply a magnetic field of the same polarity as the irreversible permanent magnet 22 to the first and second magnetic pole pieces 26 and 28 .

The excitation device 50 shown in FIG. 4 for bringing the magnetic chuck 10 into an energized state and a de-energized state includes a rectifier circuit 54 that rectifies alternating current supplied from a commercial alternating current power supply 52 and generates a direct current exciting current at a predetermined level.
including. The rectifier circuit 54 includes a plurality of resistors 56,
A plurality of capacitors 58 and a plurality of diodes 60
and a plurality of thyristors 62. The generation and value of the excitation current from the rectifier circuit 54 are controlled by a trigger pulse supplied from the control circuit 64 to the gate of the thyristor 62.

The excitation current generated by the rectifier circuit 54 is applied to the excitation coils 20a, 2 in order to switch the magnetization direction, that is, the polarity, of the reversible permanent magnets 18a, 18b.
It is supplied to a switching circuit 66 for switching the direction of the excitation current supplied to 0b. The polarity switching circuit 66 is a relay 6 controlled by the control circuit 64.
8, its two normally closed contacts 68a, 68b, and its two normally open contacts 68c, 68d. The normally closed contact 68a is the input terminal 70 for the excitation current.
A and the output terminals 72a, 72c have normally closed contacts 68.
b is connected to the input terminal 70b and output terminal 72b for the excitation current, and the normally open contact 68c is connected to the input terminal 70.
a and output terminal 72b, and normally open contact 68d.
are connected to the input terminal 70b and the output terminals 72a and 72c, respectively.

Output terminals 72a, 72b, 72 of switching circuit 66
c is the excitation coil 20 to which the excitation current is to be supplied;
It is connected to a selection circuit 74 for selecting a and 20b. The selection circuit 74 includes a relay 76 controlled by the control circuit 64 and its normally closed contact 76a.
and a normally open contact 76b. Normally closed contact 76
a is connected to the terminals 72a and 78a, and the normally open contact 7
6b is connected to terminals 72c and 78c. Terminal 72b and terminal 78b are short-circuited.

Excitation coil 20a is connected to terminals 78a and 78b, whereas excitation coil 20b is connected to terminal 7
8b and 78c.

The control circuit 64 includes a switch 80 for turning the magnetic chuck 10 into an energized state and a de-energized state, and a setting circuit 8 for setting the voltage level of the exciting current.
2 are connected. The setting circuit 82 includes a variable resistor 84a for setting the value of the excitation current supplied to the excitation coil 20a, and a variable resistor 84 for setting the value of the excitation current supplied to the excitation coil 20b.
It consists of b.

When using the chuck 10, as shown in FIG.
When the contact a of the switch 80 is connected at time T ₁ to place the magnetic chuck 10 in an excited state, the control circuit 64 first switches between the switching circuit 66 and the selection circuit 74.
time without activating relays 68 and 76.
Thyristor 6 of rectifier circuit 54 from T ₂ to T ₃
A gate pulse is supplied to 2. As a result, the excitation current output from the rectifier circuit 54 is transferred from the contact 68a to the contact 76a, to the excitation coil 20a, and to the contact 68.
2 and 3, the polarity reversible permanent magnet 18a around which the excitation coil 20a is wound is
Contrary to the diagram, the magnetization is such that the pole on the housing 14 side is the north pole and the pole on the connection body 16 side is the south pole.

Next, the control circuit 64 operates the thyristor 6 between time T ₄ and time T ₅ with the relay 76 activated.
A gate pulse is supplied to 2. As a result, the excitation current output from the rectifier circuit 54 is transferred from the contact 68a to the contact 76b, to the excitation coil 20b, and to the contact 68.
Therefore, the reversible polarity permanent magnet 18b around which the excitation coil 20b is wound has a polarity such that the polarity reversible permanent magnet 18b has an N pole on the housing 14 side, like the polarity reversible permanent magnet 18a.
The pole on the side of the connecting body 16 is magnetized to become the S pole.

As a result, the first pole piece 26 is attached to the permanent magnet 18.
The second magnetic pole piece 28 acts as the N pole of the permanent magnets 18a, 18b, 22 because it is magnetically connected to the N pole of the permanent magnets 18a, 18b, 22.
Since it is magnetically connected to the south pole of permanent magnets 18a, 18b, 22, it acts as the south pole of all permanent magnets 18a, 18b, 22. As a result, the work surface 32 is placed in an excited state (operating state), and the magnetic body 86 is attracted to the work surface 32. The magnetic fields that act on the magnetic body 86 in this excited state are the magnetic field caused by the irreversible polarity permanent magnet 22 and the magnetic field caused by the reversible polarity permanent magnets 18a and 18b.

On the other hand, as shown in FIG. 6, when the contact b of the switch 80 is turned on at time _t1 to place the magnetic chuck 10 in a de-energized state, the control circuit 64
First, with the relay 68 of the switching circuit 66 activated, a gate pulse is supplied to the thyristor 62 of the rectifier circuit 54 from time t ₂ to time t ₃ .

At this time, the excitation current (first reversal current) output from the rectifier circuit 54 is applied to the reversible permanent magnet 18.
is a value smaller than the value that completely inverts a,
Further, from the contact 68c, the exciting coil 20a and the contact 7
6a and through contact 68d. As a result, the polarity reversible permanent magnet 18a around which the excitation coil 20a is wound, as shown in FIGS. 2 and 3,
A magnetic field acts such that the pole on the housing 14 side is an S pole and the pole on the connecting body 16 side is an N pole.

However, at this point, the magnetization direction of the reversible permanent magnet 18a is not completely reversed.
Therefore, after the first reversal current to the excitation coil 20a is cut off at time _t3 , the strength of the magnetic field of the irreversible polarity permanent magnet 22 and the magnetic field of the reversible polarity permanent magnet 18b acting on the working surface 32 is , is weakened by the magnetic field of the reversible permanent magnet 18a whose polarity has been completely reversed, so that the working surface is placed in a weakly excited state and the magnetic body 86 is weakly attracted to the working surface 32.

Next, control circuit 64 supplies a gate pulse to thyristor 62 from time t ₄ to time t ₅ with relays 68 and 76 activated. As a result, the excitation current (second reversal current) output from the rectifier circuit 54 is transferred from the contact 68c to the excitation coil 2.
0b, contacts 76b, and contacts 68d, the reversible polarity permanent magnet 18b around which the excitation coil 20b is wound is magnetized so that the pole on the housing 14 side is the S pole and the pole on the connecting body 16 side is the N pole. Ru.

The second reversal current at this time is large enough to completely reverse the magnetization direction of the reversible permanent magnet 18b, and is also large enough to completely reverse the magnetization direction of the reversible permanent magnet 18b.
It is also large enough to apply a magnetic field in the opposite direction to the previously attracted state. Therefore, the second
During time t ₄ to _{t 5} when the reversal current is generated, the magnetic body 86 is acted upon by a weak magnetic field in the opposite direction to that in the attracted state.

However, when the second reversal current is cut off at time _t5 , the work surface 32 is placed in a weaker excitation state in the same direction as the attracted state, and the magnetic body 86 is again affected by the weak magnetic field in the same direction as the attracted state. receive. This means that the magnitude of the magnetic field of the irreversible polarity permanent magnet 22 is
This is because it is larger than the sum of the magnetic field of the polarity reversible permanent magnet 18a whose polarity is completely reversed by the first reversal current and the magnetic field of the polarity reversible permanent magnet 18b whose polarity is completely reversed by the second reversal current. That is, this is because the polarity reversible permanent magnet 18a remains in an incompletely reversed state.

Next, control circuit 64 supplies a gate pulse to thyristor 62 from time t ₆ to time t ₇ with relay 68 activated. As a result, the excitation current (third
A reversal current of
0a, contacts 76a, and contacts 68d, the polarity reversible permanent magnet 18a around which the excitation coil 20a is wound is affected by a magnetic field in which the pole on the housing 14 side is the S pole and the pole on the connection body 16 side is the N pole. receive.

The magnitude of the third reversal current at this time is such that the incomplete magnetization of the reversible permanent magnet 18a is completed and a weak magnetic field in the opposite direction to the attracted state acts on the magnetic body 86. It is. As a result, from time t ₆ to when the reversal current shown in FIG. 3 is generated,
During t ₇ , the magnetic body 86 is again subjected to the action of a weak magnetic field in the opposite direction to that in the attracted state.

The third reversal current to the excitation coil 20a is applied at time t ₇
When the magnetic field is cut off at , the magnetic field of the irreversible polarity permanent magnet 22 and the magnetic field of the reversible polarity permanent magnets 18a and 18b whose magnetization direction has been completely reversed cancel each other out, and therefore act on the magnetic body 32 on the work surface 32. The magnetic field is removed and the magnetic body 86 is released from the magnetic chuck 10.

As described above, if the first to third reversal currents are supplied at intervals, it is possible to notice that the second reversal current has been supplied, that the supply of the second reversal current has been stopped, and that the third reversal current has been supplied. By supplying the reversal current, a weak alternating magnetic field acts on the magnetic body 86, and the magnetic body 86 is effectively demagnetized. Such demagnetization action first completely reverses the magnetization direction of the reversible polarity permanent magnet 18a, and then reverses the magnetization direction of the reversible polarity permanent magnet 18a.
This problem also occurs when other reversal methods are employed, such as completely reversing the magnetization direction of the reversible permanent magnet 18b after completely reversing the magnetization direction of the reversible permanent magnet 18b.

Note that the magnetic body 86 can be demagnetized even if the excitation current is supplied to the excitation coils 20a and 20b once each. That is, in this case, if the exciting current is supplied to the exciting coils 20a and 20b in this order,
The magnetic body 86 attracted to the magnetic chuck 10 is magnetized by the magnetic field generated by the excitation coil 20a when an excitation current for placing the magnetic chuck 10 in a non-excited state is supplied to the excitation coil 20a. However, when the excitation coil 20b is supplied with an excitation current for placing the magnetic chuck 10 in a non-excited state, it is affected by the magnetic field generated by the excitation coil 20b, so that it can be easily removed from the magnetic chuck 10. demagnetized to a certain extent. This demagnetization effect and the amount of demagnetization vary depending on the material, processing precision, shape, excitation current, etc. of the magnetic body.

According to the excitation device 50, the excitation coils are divided into two groups in order to change the polarity of the irreversible permanent magnet, and when the polarity is changed, the excitation current is sent to the excitation coils 18a,
18b, the amount of excitation current that flows at once is smaller than when the excitation current is supplied to all excitation coils at the same time (the maximum value of the instantaneous excitation current is smaller), and the power supply capacity can be reduced accordingly. Can be made smaller. As a result, a circuit element with a small capacity can be used, and the amount of heat generated, thermal strain, and magnetostriction of the polarity reversible permanent magnet are reduced. Furthermore, since it is only necessary to adjust a small amount of excitation current, the excitation current can be adjusted finely and accurately.

According to the excitation device 50, the excitation current has a rest time, so that even though the excitation current is not an alternating current, each time a reversal current is supplied to the excitation coil to put the magnetic chuck in an inoperative state. Then, a reverse magnetic field acts on the magnetic material, and the magnetic material is demagnetized. As a result, the magnetic material attracted to the work surface is automatically and effectively demagnetized, and the magnetic material can be easily removed from the work surface.

According to the excitation device 50, the variable resistors 84a, 84b for current setting are further connected to the excitation coils 18a, 84b.
Since each excitation coil 18b is provided, the excitation coil 18a, 18
The excitation current supplied to the terminals b can be set separately by the setting circuit 82.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of an embodiment of the magnetic chuck of the present invention, FIG. 2 is a cross-sectional view taken along the - line in FIG. 1, and FIG. 4 is a block diagram of an electric circuit showing an embodiment of the excitation device of the present invention;
FIG. 5 is a diagram showing the waveform of an electric signal when the magnetic chuck is placed in an energized state, and FIG. 6 is a diagram showing the waveform of an electric signal when the magnetic chuck is placed in a non-excited state. 10: Magnetic chuck, 18a, 18b: Reversible polarity permanent magnet, 20a, 20b: Excitation coil, 2
2: Irreversible polarity permanent magnet, 54: Rectifier circuit, 6
4: Control circuit, 66: Polarity switching circuit, 74: Excitation coil selection circuit.

Claims (1)

[Claims] 1 at least one polarity irreversible permanent magnet; a plurality of polarity reversible permanent magnets magnetically connected to the polarity irreversible permanent magnet by a common magnetic circuit member;
A magnetic chuck excitation device including a plurality of excitation coils for switching the polarity of the polarity reversible permanent magnet for each magnet, a switching circuit for switching the polarity of an excitation current supplied to the excitation coil, and a switching circuit for switching the polarity of an excitation current supplied to the excitation coil; The excitation coils for switching the polarity of the polarity reversible permanent magnets that are commonly magnetically connected to the irreversible permanent magnet are divided into a plurality of groups, and the excitation coils are sequentially selected for each group with a pause time. An excitation device for a magnetic chuck, comprising: a selection circuit that supplies the excitation current to the excitation coil; and a control circuit that controls the switching circuit and the selection circuit.