JP2002354779A - Linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear motor capable of preventing the influence of a leakage magnetic flux from the motor so as not to make a magnetic sensor malfunction. SOLUTION: The linear motor 1 is provided with a magnetic field yoke 3 comprising two rows of a plurality of permanent magnets 4 straight aligned and constituting magnetic field poles alternately having a different polarity, an armature 6 disposed opposite to the rows of the permanent magnets 4 through a magnetic air gap and having an armature winding 8 comprising a group of a plurality of coils, and magnetic sensors 15, 16 for detecting the position of the armature 6. The magnetic field poles constitute a stator. The armature 6 constitutes a movable element moving relative to the stator. In the linear motor 1, a magnetic shield plate 17 for magnetically shielding the linear motor through a nonmagnetic material 10 is provided on an outer face of the magnetic field yoke 3 and a leakage magnetic flux reducing coil 18 is provided on a back face 17a of the magnetic shield plate 17 and turned on so as to cancel a magnetic flux generated by the permanent magnets 4 and the armature winding 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor suitable for applications requiring ultra-precision positioning and high thrust, such as a table feed of a semiconductor manufacturing apparatus or a machine tool. It is related to the configuration to be performed.

[0002]

2. Description of the Related Art Conventionally, linear motors suitable for applications requiring ultra-precision positioning and high thrust, such as table feed of a semiconductor manufacturing apparatus or a machine tool, are shown in FIGS. FIG. 5 is a perspective view of a conventional linear motor. FIG. 6 is a front sectional view of a conventional linear motor viewed from a traveling direction in which a thrust is generated, and shows a state in which a fixed base, a linear guide, a table, a magnetic sensor, and a magnetic shield plate are incorporated. In the conventional example, a moving coil type linear motor will be described as an example. In the figure,
1 is a linear motor, 2 is a field yoke fixing plate, 3 is a field yoke, 4 is a permanent magnet, 5 is an armature fixing plate, 6 is an armature,
7 is a fixed winding frame, 8 is an armature winding, 9 is a resin mold,
10 is a non-magnetic material, 11 is a fixed base, 12 is a table, 13
Is a guide rail, 14 is a slider, 15 is a magnetic sensor (linear scale), 16 is a magnetic sensor (sensor head), and 17 is a magnetic shield plate. Linear motor 1
Are arranged in such a manner that a plurality of permanent magnets 4 constituting a field pole are alternately arranged linearly in the longitudinal direction of a field yoke 3 composed of two rows so that the polarities of an N pole and an S pole are alternately different. The field yoke fixing plate 2 is disposed between the field yokes 3 to form a stator. Further, in the longitudinal direction of the magnet row of the permanent magnets 4 arranged in parallel, a coreless armature winding 8 formed of a plurality of coil groups and formed into a flat plate so as to face each other via a magnetic gap. Are disposed, and the armature 6 constitutes a mover. Here, as shown in FIG. 5, the armature windings 8 are held on both sides of a flat plate-shaped winding fixing frame 7 made of a non-magnetic material such as stainless steel so as to improve strength and insulation. . Further, the armature winding 8 is fixed to the winding fixing frame 7 by a resin mold 9, and the winding fixing frame 7 to which the armature winding 8 is fixed is fixed to the armature fixing plate 5.

[0003] Such a linear motor 1 is provided so as to sandwich both sides of a movable armature 6 on which a pair of fixed permanent magnets 4 are movable.
(A magnetic flux penetrating type structure), and the energized armature winding 8 is driven by an electromagnetic action between the magnetic flux generated in each coil group and the permanent magnet 4.
It is designed to move linearly. Then, in the linear motor 1 having this structure, the outer circumference of the field yoke 3 (the side surface and the outside) is so set that the magnetic flux of the magnetic circuit does not affect the magnetic sensors 15 and 16 attached to the table 12 or other peripheral devices not shown. Both ends) are covered with a magnetic shield plate 17 made of a ferromagnetic material such as permalloy via a nonmagnetic material 10 such as an air layer or a resin mold. Here, the nonmagnetic material 10 is an air layer. Then, regarding the field yoke fixing plate 2 and the magnetic shield plate 17 provided on the linear motor 1, the field yoke fixing plate 2,
A female screw (not shown) for fastening is provided on the magnetic shield plate 17, a through hole (not shown) is provided on the fixing base 11, and the magnetic shield plate 17 is fixed by a bolt (not shown) having a male screw.
Further, a linear guide is constituted by the guide rail 14 provided on the fixed base 11 and the slider 13 attached to the table,
The linear motor 1 is supported.

[0004]

However, in the prior art, since the end of the permanent magnet 4 and the end of the field yoke 3 are open to face the armature mounting plate 5, the magnetic flux from the opening. Was leaking. Since the leaked magnetic flux differs at the same measurement point depending on the relative position of the mover and the stator and the generated thrust, a magnetic field fluctuation due to the leaked magnetic flux occurs.
After affecting a magnetic sensor or a device outside the linear motor, a malfunction occurs, and as a result, there is a problem in that a precise positioning operation is hindered. The present invention has been made to solve the above-described problem, and has as its object to provide a linear motor that can prevent the influence of magnetic flux leakage from a motor so that a magnetic sensor does not malfunction. And

[0005]

In order to solve the above-mentioned problem, the present invention of claim 1 is directed to a two-row arrangement in which a plurality of permanent magnets constituting a field pole are arranged in a straight line so as to have alternately different polarities. A field yoke, an armature having an armature winding composed of a plurality of coil groups and arranged opposite to a magnet row of the permanent magnets via a magnetic gap, and detecting a position of the armature. A magnetic sensor, and a linear motor in which one of the field pole and the armature is used as a stator and the other is used as a mover, and the field pole and the armature run relatively to each other. A magnetic shield plate for magnetically shielding the linear motor via a non-magnetic material is provided on the outer surface of the outer surface of the magnetic shield plate.On the back surface of the magnetic shield plate, a coil for reducing leakage magnetic flux is provided. Said permanent magnet and front It is intended to be energized so as to cancel out the magnetic fluxes due to the armature winding. According to a second aspect of the present invention, in the linear motor according to the first aspect, an end of the field yoke is L-shaped toward the surface of the armature winding so as to cover an end of the permanent magnet. It has a bent shape. According to a third aspect of the present invention, in the linear motor according to the first or second aspect, the leakage magnetic flux reducing coil is configured such that windings are concentratedly mounted on a core made of an insulator having a rectangular cross section. Things.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a front sectional view of a linear motor according to a first embodiment of the present invention viewed from a traveling direction, in which a linear guide, a table, a magnetic sensor, and a magnetic shield plate are incorporated. Is shown. FIG. 2 is a perspective view of a state in which the leakage magnetic flux reducing coil of the present invention is attached to the back surface of the magnetic shield plate as viewed from the bottom. The components of the present invention that are the same as those in the prior art are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described. The external appearance (perspective view) of the linear motor of the present invention is the same as that shown in FIG. The differences between the present invention and the prior art are as follows. That is, in FIG. 1, on the back surface 17a of the magnetic shield plate 17, a leakage magnetic flux reducing coil 18 is provided.
In addition, current is supplied so as to cancel the magnetic flux generated by the armature winding 8. The current value flowing through the leakage magnetic flux reducing coil is stored in a data table in advance, and the current value is stored in a controller (not shown). Is determined. Further, as shown in FIG. 2, the leakage magnetic flux reducing coil 18 is configured by concentrating windings around a core 19 made of an insulator having a rectangular cross section.

Next, verification was performed to confirm the effect of the leakage magnetic flux reduction coil 18 to reduce the leakage magnetic flux. FIG. 3 is a graph showing the relationship between the current frequency of the armature and the leakage flux by comparing the presence or absence of the leakage flux reduction coil. The exciting frequency of the leakage magnetic flux reducing coil 18 was the same as the armature current frequency. It became clear that the leakage magnetic flux from the motor part was reduced from 1/4 to 1/10 by the leakage magnetic flux reduction coil 18.

Therefore, the first embodiment of the present invention provides a field yoke 3 composed of two rows in which a plurality of permanent magnets 4 constituting a field pole are arranged in a straight line, and a magnet row of the permanent magnets 4 and a magnetic field. The armature windings 8 are disposed opposite each other with a gap therebetween.
Armature 6 having a magnetic field, the magnetic sensors 15 and 16 for detecting the position of the armature 6, and the linear motor 1 which relatively travels with the field poles as the stator and the armature 6 as the mover. A non-magnetic material 1 is provided on the outer surface of the field yoke 3 and on its outer periphery.
0, a magnetic shield plate 17 for magnetically shielding the linear motor 1 is provided through the rear surface 17 of the magnetic shield plate 17.
a is provided with a leakage magnetic flux reducing coil 18 and is configured to conduct electricity so as to cancel the magnetic flux generated by the permanent magnet 4 and the armature winding 8, so that the leakage magnetic flux generated in the motor portion and the leakage magnetic flux reducing coil 18 are generated. Magnetic fluxes cancel each other out, and the effect of leakage magnetic flux on the magnetic sensors 15 and 16 can be prevented. As a result, the magnetic sensors 15, 16
Can be provided. In addition, the leakage flux reducing coil 18
Has a structure in which a winding is concentratedly wound around a core 19 made of an insulator having a rectangular cross section, so that when the core 19 is mounted on the back surface 17a of the magnetic shield plate 17, both members have the same planar shape. Because of the contact surface, the magnetic flux leakage reduction coil 18 can be easily positioned and attached to the magnetic shield plate 17.

(Second Embodiment) The second embodiment is different from the first embodiment in that the end 3a of the field yoke 3 covers the end 4a of the permanent magnet 4 in the armature. The point is that it has a shape bent in an L shape toward the surface of the winding 8. When the shape of the end 3a of the field yoke 3 is improved as in the above-described means, the magnetic flux to be leaked from the end 4a of the permanent magnet 4 flows through the end 3a of the field yoke 3 bent into an L shape. The magnetic flux leaking from the end portion 4a of the permanent magnet 4 becomes substantially zero, and thereby the magnetic sensors 15 and 16 are
Is not affected by stray magnetic flux. As a result, it is possible to provide a linear motor that does not cause the magnetic sensors 15 and 16 to malfunction, and to significantly reduce magnetic flux leakage from the motor as compared with the related art.

In the embodiment of the present invention, the example in which the leakage magnetic flux reducing coil 18 is mounted on the back surface 17a of the magnetic shield plate 17 has been described. The magnetic flux leakage reduction coil 18 may be directly arranged on the back surface of the field yoke 3. Further, in the present embodiment, an example of the mounting direction and the position of the mover, the stator and the magnetic sensor of the linear motor has been described, but the mounting direction and the position shown in the embodiment are not limited. Is appropriately selected according to the conditions. In this embodiment, a moving coil type linear motor using an armature as a mover has been described as an example. However, the present invention may be applied to a moving magnet type linear motor using a field pole as a mover. Further, in this embodiment, the armature of the linear motor is described as a coreless type, but the present invention is also applicable to a cored type armature in which electromagnetic steel sheets are laminated. Further, in the present embodiment, an example is shown in which a plurality of permanent magnets having different polarities are alternately used for the magnets constituting the field poles. However, a magnet in which one magnet is multipolarly magnetized may be used.

[0011]

As described above, according to the first embodiment of the present invention, a field yoke composed of two rows in which a plurality of permanent magnets constituting a field pole are arranged in a straight line, An armature having an armature winding and an armature winding, and a magnetic sensor for detecting the position of the armature, a field pole serving as a stator, and an armature serving as a mover, which are arranged opposite to the magnet row with a magnetic gap therebetween. In a linear motor that is designed to run in a fixed manner, an outer surface of the field yoke is provided with a magnetic shield plate for magnetically shielding the linear motor via a non-magnetic material on an outer periphery thereof,
A magnetic flux leakage reduction coil is provided on the back side of the magnetic shield plate to energize so as to cancel out the magnetic flux generated by the permanent magnet and the armature winding, so that the magnetic flux generated by the magnetic flux leakage reduction coil and the leakage generated by the motor unit The magnetic fluxes cancel each other, and the effect of the leakage magnetic flux on the magnetic sensor can be prevented. This makes it possible to provide a linear motor that does not malfunction the magnetic sensor. Further, according to the second embodiment of the present invention, the end of the field yoke has a shape bent in an L shape toward the surface of the armature winding so as to cover the end of the permanent magnet. As a result, the magnetic flux leaking from the end of the permanent magnet flows through the end of the field yoke bent in an L-shape, so that the magnetic flux leaking from the opening becomes almost zero. Even if the sensor is brought close to the field yoke, it is not affected by the stray magnetic flux. This makes it possible to provide a linear motor that does not cause the magnetic sensor to malfunction, and to significantly reduce the leakage magnetic flux from the motor as compared with the conventional motor. When the core is mounted on the back of the magnetic shield plate, the core has the same flat contact surface. It can be easily positioned and attached to the magnetic shield plate.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a linear motor according to a first embodiment of the present invention viewed from a traveling direction, showing a state in which a linear guide, a table, a magnetic sensor, and a magnetic shield plate are incorporated. is there.

FIG. 2 is a perspective view showing a state in which the leakage magnetic flux reducing coil of the present invention is attached to the back (bottom) of a magnetic shield plate.

FIG. 3 is a graph showing a relationship between a current frequency of an armature and a leakage flux by comparing the presence or absence of a leakage flux reduction coil.

FIG. 4 is a front sectional view of the linear motor of the present invention viewed from the traveling direction, and shows a state where a linear guide, a table, a magnetic sensor, and a magnetic shield plate are assembled.

FIG. 5 is a perspective view of a linear motor showing a conventional technique.

FIG. 6 is a front sectional view of a conventional linear motor viewed from a traveling direction in which a thrust is generated, showing a state where a fixed base, a linear guide, a table, a magnetic sensor, and a magnetic shield plate are incorporated. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Linear motor 2 Field yoke fixing plate 3 Field yoke 3a end 4 Permanent magnet 4a end 5 Armature fixing plate 6 Armature 7 Winding fixing frame 8 Armature winding 9 Resin mold 10 Non-magnetic body 11 Fixing table DESCRIPTION OF SYMBOLS 12 Table 13 Slider 14 Guide rail 15 Magnetic sensor (linear scale) 16 Magnetic sensor (sensor head) 17 Magnetic shield plate 17a Magnetic shield plate back surface 18 Coil for reducing magnetic flux leakage 19 Core

Claims (3)

[Claims] 1. A field yoke comprising two rows in which a plurality of permanent magnets constituting a field pole are alternately arranged in a line so as to have alternately different polarities, and a magnetic gap between the row of permanent magnets and a magnetic gap. An armature having an armature winding composed of a plurality of coil groups disposed opposite to each other, a magnetic sensor for detecting a position of the armature, and one of the field poles and the armature as a stator A magnetic motor for moving the field pole and the armature relative to each other while using the other as a mover. A magnetic shield plate for performing the operation is provided.On the back surface of the magnetic shield plate, a leakage magnetic flux reducing coil is provided, and a current is supplied so as to cancel magnetic flux by the permanent magnet and the armature winding. Features and Linear motor that. 2. An end of the field yoke is directed toward a surface of the armature winding so as to cover an end of the permanent magnet.
The linear motor according to claim 1, wherein the linear motor has a shape bent in a letter shape. 3. The linear motor according to claim 1, wherein the leakage magnetic flux reducing coil has a structure in which a winding is concentratedly mounted on a core made of an insulator having a rectangular cross section. .