JP2002191164A - Linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear motor which can prevent the influence of a magnetic flux leaked from a permanent magnet so that a magnetic sensor does not malfunction. SOLUTION: In the linear motor 1 which has a field yoke 3 composed of two rows where a plurality of permanent magnets 4 constituting a field pole are arranged in a straight form so that polarities vary alternately, an armature 6 being counterposed through a magnetic space to the magnet row of the permanent magnets 4 and having a armature winding 8 composed of a plurality of coil groups, and magnetic sensors 15 and 16 for detecting the position of the armature 6, and is arranged so that field pole and the armature 6 may travel relatively, with either of the field pole and the armature 6 as a stator and the other as a needle, the field yoke 3 is provided with a magnetic shield plate 17 for performing magnetic shielding of itself 1 through a nonmagnetic substance 10 around itself, and the end 3a of the field yoke 3 is bent in a L shape toward the surface of the armature winding 8 so as to cover the end 4a of the permanent magnet 4.

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 table feed of a semiconductor manufacturing apparatus or a machine tool.

[0002]

2. Description of the Related Art Conventionally, linear motors suitable for applications requiring ultraprecision positioning and high thrust, such as table feed of a semiconductor manufacturing apparatus or a machine tool, are shown in FIGS. FIG. 4 is a perspective view of a conventional linear motor. FIG. 5 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 where a fixed base, a linear guide, a table, and a magnetic sensor 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 winding fixing frame, and 8 is an armature. Windings, 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), 17 is a magnetic shield plate. The linear motor 1 has N poles and S poles alternately.
A plurality of permanent magnets 4 constituting the field poles are arranged linearly in the longitudinal direction of the field yoke 3 composed of two rows so that the poles have different polarities. The stator is constituted by disposing the field yoke fixing plate 2. 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 with a magnetic gap therebetween. Are disposed, and the armature 6 constitutes a mover. Here, the armature winding 8 corresponds to FIG.
As shown in (1), it is held on both sides of a flat plate-shaped winding fixing frame 7 made of a non-magnetic member such as stainless steel so that strength and insulation can be improved. The armature winding 8 is fixed to the winding fixing frame 7 by a resin mold 9, and the armature winding 8
Is fixed to the armature fixing plate 5.

In such a linear motor, a pair of fixed permanent magnets 4 are provided so as to sandwich both sides of a movable armature 6, and the lines of magnetic force of the permanent magnets 4 pass through an armature winding 8 in a magnetic circuit. (A magnetic flux penetrating type structure), and the energized armature winding 8 linearly moves due to the electromagnetic action between the permanent magnet 4 and the magnetic flux generated in each coil group. I have. Then, in the linear motor having this structure, the magnetic flux of the magnetic circuit
Linear scale 15 and sensor head 16 attached to 2
Alternatively, the outer periphery (side surface and both end portions) of the field yoke 3 may be covered with a ferromagnetic material such as permalloy via a nonmagnetic material 10 such as an air layer or a resin mold so as not to affect other peripheral devices not shown. And a magnetic shield plate 17 made of Here, the nonmagnetic material 10 is an air layer. Then, with respect to the field yoke fixing plate 2 and the magnetic shield plate 17 provided on the linear motor, female screws (not shown) for fastening are provided on the field yoke fixing plate 2 and the magnetic shield plate 17, respectively, and a not-shown thread is provided on the fixing base 11. A hole is provided and fixed by a bolt (not shown) having a male screw.
The slider and the slider 13 attached to the table form a linear guide, which supports the linear motor.

[0004]

However, in the prior art, since the end of the permanent magnet 4 and the end of the field yoke 3 are open facing the armature mounting plate 5, the open permanent magnet The magnetic flux leaking from the end of the magnetic field increases, and the leaked magnetic flux affects the magnetic sensor and causes a malfunction. As a result, there is a problem that a precise positioning operation is hindered. The present invention has been made in order to solve the above-described problem, and provides a linear motor that can prevent the influence of magnetic flux leakage from a permanent magnet so that a magnetic sensor does not malfunction. Aim.

[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 is provided on the outer periphery thereof through a non-magnetic material, and the end of the field yoke covers the end of the permanent magnet. L shape toward the surface of armature winding Those having a shape bent in. According to a second aspect of the present invention, in the linear motor according to the first aspect, a length of a gap between an end of the field yoke bent in an L shape and an end of the permanent magnet is H, The distance between each permanent magnet provided in the field yoke of the row is L
When g, 0.5 ≦ H / Lg ≦ 1.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a linear motor showing an embodiment of the present invention. FIG. 2 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, and a magnetic sensor are incorporated. In addition,
Components of the present invention that are the same as those of the prior art are denoted by the same reference numerals, and description thereof is omitted. The differences between the present invention and the prior art are as follows. That is, the end 3 a of the field yoke 3 has a shape bent in an L shape toward the surface of the armature winding 8 so as to cover the end 4 a of the permanent magnet 4. Next, verification was performed to confirm the effect of reducing the magnetic flux leakage by improving the shape of the field yoke 3. FIG. 3 shows the relationship between the ratio of the distance between each permanent magnet and the ratio of the gap length between the field yoke and the permanent magnet to the amount of leakage magnetic flux, which was determined by magnetic field analysis. As a result of the magnetic field analysis, the distance between the permanent magnets 4 provided in the two rows of field yokes was set to Lg (in this example, Lg = 21 mm).
In this embodiment, when the length of the gap between the L-shaped bent end of the field yoke 3 and the end of the permanent magnet 4 is H, the relationship of 0.5 ≦ H / Lg ≦ 1 is satisfied. Has been found to be optimal, and more preferably, in the relationship of 0.7 ≦ H / Lg ≦ 0.9. When the shape of the end of the field yoke 3 is improved as in the above means, the magnetic flux to be leaked from the end of the permanent magnet 4 is bent into an L-shape.
, The magnetic flux leaking from the end of the permanent magnet 4 becomes substantially zero, so that even if the magnetic sensors 15 and 16 are brought close to the field yoke 3, the magnetic flux may be affected by the leaked magnetic flux. There is no.

Therefore, in the embodiment of the present invention, the end of the field yoke 3 is bent in an L shape toward the surface of the armature winding 8 so as to cover the end of the permanent magnet 4. When the length of the gap between the L-shaped end of the field yoke 3 and the end of the permanent magnet 4 is H, and the distance between the permanent magnets 4 is Lg, , 0.5 ≦ H / Lg ≦ 1
, The magnetic flux generated by the permanent magnet 4 always flows through the L-shaped bent end of the field yoke 3, and the magnetic flux leaking from the end of the permanent magnet 4 to the outer periphery of the linear motor is eliminated. Therefore, it is possible to prevent the magnetic sensors 15 and 16 from being affected by the magnetic flux leakage due to the permanent magnet 4, and as a result, it is possible to provide a linear motor that does not malfunction the magnetic sensors 15 and 16. Incidentally, in the embodiment of the present invention, the mover of the linear motor,
An example of the mounting direction and the position of the stator and the magnetic sensor has been described. However, the mounting direction and the position are not limited to the mounting direction and the position shown in the embodiment, and may be appropriately selected according to the use of the linear motor. Further, in this embodiment, the moving coil type linear motor having the armature as the mover has been described as an example. However, the present invention may be applied to a moving magnet type linear motor having the field pole as the mover. In this embodiment,
Although the armature of the linear motor has been described as a coreless type, the present invention can also be applied to a cored type armature in which electromagnetic steel sheets are laminated. Further, in this 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.

[0008]

As described above, according to the present invention, the end of the field yoke is bent in an L shape toward the surface with the armature winding so as to cover the end of the permanent magnet. The length of the gap between the L-shaped end of the field yoke and the end of the permanent magnet is H, and each permanent magnet 4
When the distance between them is Lg, the configuration has a relationship of 0.5 ≦ H / Lg ≦ 1, so that the magnetic flux generated by the permanent magnet always flows through the L-shaped bent end of the field yoke, Since there is no magnetic flux leaking from the end to the outer periphery of the linear motor, it is possible to prevent the influence of the magnetic flux leaked by the permanent magnet on the magnetic sensor, and as a result, to provide a linear motor that does not malfunction the magnetic sensor. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a perspective view of a linear motor according to an embodiment of the present invention.

FIG. 2 is a front sectional view of the linear motor of the present invention viewed from the traveling direction, showing a state where a linear guide, a table, and a magnetic sensor are incorporated.

FIG. 3 is a graph illustrating the relationship between the ratio of the distance between each permanent magnet and the gap length between the field yoke and the permanent magnet and the amount of leakage magnetic flux.

FIG. 4 is a perspective view of a conventional linear motor.

FIG. 5 is a front sectional view of a conventional linear motor viewed from a traveling direction, and shows a state where a linear guide, a table, and a magnetic sensor are incorporated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Linear motor 2 Field yoke fixing plate 3 Field yoke 3a End part 4 Permanent magnet 4a Dark part 5 Armature fixing plate 6 Armature 7 Winding fixing frame 8 Armature winding 9 Resin mold 10 Nonmagnetic body 11 Fixing table 12 Table 13 Slider 14 Guide rail 15 Magnetic sensor (linear scale) 16 Magnetic sensor (sensor head) 17 Magnetic shield plate

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takao Fujii 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu-shi, Fukuoka F-term (reference) 5H605 AA11 BB05 BB10 CC01 DD36 FF01 5H641 GG02 GG03 GG05 GG07 GG11 GG12 GG26 GG28 HH02 HH03 HH05 HH13 HH14 HH16 HH17

Claims (2)

[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 the magnetic row. 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 pole and the armature being a stator. In a linear motor in which the other is a movable element and the field pole and the armature run relatively to each other, the field yoke performs magnetic shielding of the linear motor through a non-magnetic material on an outer periphery thereof. The end of the field yoke has an L-shape bent toward the surface of the armature winding so as to cover the end of the permanent magnet. Linear feature Over data. 2. A permanent magnet provided in each of the two rows of field yokes, wherein a length of a gap between an L-shaped bent end of the field yoke and an end of the permanent magnet is H. Distance between L
2. The linear motor according to claim 1, wherein, when g, a relationship of 0.5 ≦ H / Lg ≦ 1 is satisfied.