JP2024049435A - Yoke assembly and linear motor - Google Patents

Abstract

[Problem] To provide a yoke assembly that can reduce the size and weight of a linear motor and obtain a uniform thrust and high output, and a linear motor having said yoke assembly. [Solution] A yoke assembly 41 used in a linear motor in which a stator 1 and a mover are relatively movable, has a pair of long plate-like yokes 212 arranged opposite each other with a gap therebetween, and a yoke fixing part 411 that supports the pair of yokes in a cantilever manner at one end in the short direction of the pair of yokes, and a protrusion 415 is formed on the surface of the yoke fixing part that supports the pair of yokes, and the protrusion is configured so that the pair of yokes expand the gap from one end side to the other end side. [Selected Figure] Figure 4

Description

The present invention relates to a yoke assembly that constitutes the stator or mover of a linear motor, and a linear motor having the yoke assembly.

Two-axis stage devices, so-called XY stages, are used as transport devices for various parts in semiconductor manufacturing equipment, liquid crystal manufacturing equipment, and inspection equipment for semiconductor elements and liquid crystal displays, etc. The XY stage is equipped with an X stage that moves in a specific direction (X direction) relative to a base, and a Y stage that moves in a direction perpendicular to the X direction (Y direction).
The X stage and the Y stage include a driving section driven by a linear motor, etc. The linear motor includes a magnetic field generating member with a U-shaped cross section having a permanent magnet supported by a yoke so that the north pole and the south pole face each other, and a coil member having a coil that crosses the magnetic field.
In a linear motor, when a current is passed through the coil, the magnetic field generated by the permanent magnet interacts with the magnetic field generated in the coil, allowing relative movement between the magnetic field generating member and the coil member.

Patent Document 1 discloses a linear motor composed of a stator in which adjacent permanent magnets and opposing permanent magnets are arranged on the inner side of a yoke with a U-shaped cross section so that their magnetic poles are different, and a mover made of a coil arranged opposite the row of permanent magnets.
Patent document 2 discloses a linear motor having a movable element with permanent magnets arranged facing each other within a frame body (yoke) that is square-shaped when viewed from above, and a stator made of a coil arranged within the frame body.

JP 2008-245475 A JP 2004-40939 A

In linear motors arranged in this manner, permanent magnets with strong magnetic force are used to obtain high output, and the attractive force between the magnets can cause the yoke in which the magnets are arranged to bend, which can result in a lack of sufficient gap between the magnets and the mover (stator).
One possible way to prevent the yoke from bending is to make the yoke thicker, making it less likely to bend. However, this would make it difficult to make the linear motor smaller and lighter.
Furthermore, due to the curvature of the yoke, the intervals between the magnets arranged on the inner surface (opposing surface) of the yoke vary depending on the location, which can cause the thrust to vary depending on the relative position of the mover (stator).

The present invention aims to provide a yoke assembly that reduces the size and weight of a linear motor and can provide a uniform thrust and high output, as well as a linear motor having the yoke assembly.

The yoke assembly of the present invention is a yoke assembly used in a linear motor in which a stator and a movable element are relatively movable, and is characterized in that it has a pair of elongated plate-like yokes arranged opposite each other with a gap therebetween, and a yoke fixing part that supports each of the pair of yokes in a cantilever manner at one end of the short side of the pair of yokes, and a protrusion is formed on the surface of the yoke fixing part that supports the pair of yokes, and the protrusion is configured to cause the pair of yokes to expand the gap from the one end side to the other end side.

The yoke assembly of the present invention is a yoke assembly used in a linear motor in which a stator and a movable element are relatively movable, and is characterized in that it has a pair of long, plate-like yokes arranged opposite each other with a gap therebetween, and yoke fixing parts that support the pair of yokes at both longitudinal ends of the pair of yokes, and a protrusion is formed on the surface of the yoke fixing part that supports the pair of yokes, and the protrusion is configured to widen the gap between the pair of yokes as the pair of yokes move away from the yoke fixing part.

The linear motor of the present invention is characterized in that a plurality of permanent magnets are arranged on each of the opposing surfaces of a pair of yokes of the yoke assembly that are arranged opposite each other across the gap, and a coil is arranged in the gap that faces the plurality of permanent magnets.

The present invention provides a yoke assembly that can reduce the size and weight of a linear motor while providing a uniform thrust and high output, and a linear motor having the yoke assembly.

1 is a plan view showing a basic configuration of a linear motor according to an embodiment of the present invention; 2 is a cross-sectional view taken along line AA of FIG. 1. FIG. 2 is a cross-sectional view of a yoke assembly for explaining an embodiment of the present invention. FIG. 2 is a cross-sectional view of a yoke assembly (after permanent magnets are disposed) for explaining an embodiment of the present invention. 4A is an axial cross-sectional view of a yoke fixing portion, and FIG. FIG. 11 is an axial cross-sectional view of a yoke assembly for explaining a comparative example. FIG. 7 is a view of the yoke assembly shown in FIG. 6 after permanent magnets have been disposed therein. FIG. 4 is an axial cross-sectional view of a yoke fixing portion according to a comparative example of the present invention. FIG. 11 is an axial cross-sectional view of a yoke fixing portion showing another embodiment according to the comparative example. FIG. 11 is an axial cross-sectional view of a yoke assembly showing another embodiment according to the comparative example. 5A and 5B are a plan view and a side view of a linear motor according to another embodiment of the present invention. FIG. 11 is a plan view of a mover according to another embodiment of the present invention. FIG. 11 is a side view of a stator according to another embodiment of the present invention. FIG. 4 is a plan view of a yoke assembly according to another embodiment of the present invention. FIG. 15 is a diagram showing a permanent magnet being disposed in the yoke assembly of FIG. 14 .

Hereinafter, the present invention will be described based on an embodiment thereof.
FIG. 1 is a plan view showing the basic structure of a linear motor according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG.
1 and 2, the basic structure of a linear motor according to an embodiment of the present invention will be described.
The linear motor 10 has a stator 1 and a mover 3. The stator 1 and the mover 3 are arranged so as to be movable relative to one another. Specifically, the linear motor 10 of the present invention includes the stator 1 having a plurality of divided units 2 including a magnetic field generating member 22, and the mover 3 having a coil member 4 having a multi-phase coil and a holder 5. The mover 3 drives within a magnetic gap g formed inside the stator 1.
The linear motor 10 has a plurality of split units 2 connected along the moving direction of the mover 3 (the up-down direction (X direction) in FIG. 1), and each split unit 2 has a similar structure. However, the lengths do not need to be the same. As shown in FIG. 2, the mover 3 is equipped with a coil member 4 having a multi-phase coil and a holder 5 that supports the coil member 4. The coil member 4 contains a multi-phase coil along the moving direction of the mover 3.

The split unit 2 forming the stator 1 includes a yoke assembly 21 and permanent magnets 22, 23 which are magnetic field generating members. The yoke assembly 21 has a yoke fixing part 211 and a pair of yokes 212. The yoke fixing part 211 is shaped like a rectangular column, and a pair of elongated plate-shaped yokes 212 are arranged on the sides of the yoke fixing part 211 so as to face each other with a gap between them. The yoke assembly 21 has a U-shaped cross section. That is, the yoke fixing part 211 joins one end side (the lower side in FIG. 2 ) of the pair of yokes 212 in the height direction, and supports each of the yokes 212 in a cantilever shape. The yoke fixing part 211 and the yoke 212 which constitute the yoke assembly 21 are made of a magnetic material such as a magnetic steel plate, but the yoke fixing part 211 may be made of a non-magnetic material.
A groove 213 is formed in the yoke fixing portion 211, extending in the moving direction of the mover 3. The groove 213 is provided in the center in the width direction of the yoke fixing portion 211. The depth and width of the groove 213 are set to a dimension that allows a part of the coil member 4 to fit therein. Note that the groove 213 is not an essential component.

On one side of the pair of yokes 212, multiple permanent magnets (22, 23) are arranged at a predetermined interval along the moving direction of the mover 3. The magnetization direction of the multiple permanent magnets (22, 23) is the thickness direction (direction perpendicular to the moving direction of the mover 3), and the magnets facing each other across a magnetic gap are arranged so that they have different polarities, and the magnets lined up in the moving direction of the mover 3 each have different magnetic poles. The multiple permanent magnets 22, 23 may be made of the same material and have the same dimensions. In Figures 1 and 2, the magnet whose north pole faces the magnetic gap is marked with the symbol 22, and the magnet whose south pole faces the magnetic gap is marked with the symbol 23.

According to the linear motor 10 of the present invention, the mover 3 is provided with a magnetic field detection element such as a Hall element to detect the magnetic pole position and change the direction of the current flowing through each coil of the coil member, thereby moving the mover 3 in the movable direction.

Known permanent magnets can be used for the permanent magnets 22 and 23. One example is a rare earth magnet. As a rare earth magnet, an R-T-B system sintered magnet containing R (R is at least one element selected from rare earth elements such as Nd), T (T is Fe or Fe and Co), and B (boron) as essential components is preferable.
In order to achieve a smaller, lighter, more efficient, and more energy-efficient linear motor (improved energy efficiency), it is preferable to use an RTB based sintered magnet.

First embodiment
FIG. 3 is a cross-sectional view of a yoke assembly according to embodiment 1 of the invention (cross-sectional view perpendicular to the moving direction of the mover 3), FIG. 4 is a cross-sectional view of the yoke assembly of FIG. 3 with a permanent magnet attached, FIG. 5(a) is a cross-sectional view of a yoke fixing part 411 according to embodiment 1 of the invention, and FIG. 5(b) is a side view of the yoke fixing part 411 in the longitudinal direction (the moving direction of the mover 3).
The yoke assembly 41 according to the first embodiment of the invention has one end (the lower side in FIG. 2 ) of a pair of yokes 212 in the short direction (height direction) joined to the longitudinal side (the moving direction of the movable element 3) of the yoke fixing portion 411, and supports each of the yokes 212 in a cantilever manner.
5, the yoke fixing part 411 has a protrusion 415 at the upper end of the longitudinal side surface (the direction in which the mover 3 moves). When viewed from a side surface in a direction perpendicular to the longitudinal direction (the short side surface), the protrusion 415 protrudes outward on both sides (left and right directions in the figure) from the upper end of the yoke fixing part 411 and has a rectangular cross section. The protrusion 415 is provided continuously on the longitudinal side surface (the direction in which the mover 3 moves) of the yoke fixing part 411.
As shown in Figure 3, when the yoke 212 is joined to the longitudinal side of the yoke fixing part 411 by a known method to form the yoke assembly 41, the pair of yokes 212 are configured so that the gap (the gap between the pair of yokes 212) expands from one end side (the lower side in the figure) to the other end side (the upper side in the figure) due to the protrusion portion 415 of the yoke fixing part 411.

FIG. 4 shows a cross-sectional view of the yoke 412 with the permanent magnets 22 and 23 attached thereto.
The attractive force of the permanent magnets 22 and 23 causes the pair of yokes 212 to bend inward (toward the magnetic gap), correcting the state in which they were open from the bottom to the top, and the gap between the permanent magnets 22 and 23 becomes almost uniform.
In this way, by adjusting the height of the protrusion 415 and the thickness (rigidity) of the yoke 212, the gap between the permanent magnets 22, 23 after bending (straightening) can be adjusted, and contact between the permanent magnets 22, 23 and the movable member 3 (coil member 4) caused by narrowing the gap can be avoided, making it possible to obtain a uniform thrust and high output.
In addition, the cross-section of the protrusion 415 is not limited to a rectangular shape, and it is sufficient that the yoke 212 is open from the bottom to the top when the yoke 212 is attached, and the cross-section may be an arc shape or a triangular shape.
Furthermore, the protrusions 415 do not need to be provided continuously on the side surface of the yoke fixing portion 411 in the longitudinal direction (the direction in which the mover 3 moves), and may be partially missing or may be scattered.
In these cases, it is sufficient that the gap between the permanent magnets 22, 23 is uniform in the longitudinal direction (the direction in which the mover 3 moves) (the distance of the gap does not change).

Comparative Example of Embodiment 1 FIG. 6 is a cross-sectional view of a yoke assembly according to a comparative example of embodiment 1 of the invention (a cross-sectional view in a direction perpendicular to the moving direction of the mover 3), FIG. 7 is a cross-sectional view of the yoke assembly of FIG. 6 with a permanent magnet attached, and FIG. 8 is a cross-sectional view of a yoke fixing portion 211 according to the comparative example.
The yoke fixing portion 211 according to the comparative example differs from the first embodiment in that there is no protrusion at the upper end of the side surface of the yoke fixing portion 211 in the longitudinal direction (the direction in which the mover 3 moves).
As in the first embodiment, when the pair of yokes 212 are joined to the longitudinal side surfaces of the yoke fixing portion 211 by a known method, the yokes 212 are substantially parallel from the bottom to the top.

FIG. 7 is a cross-sectional view showing a state in which the permanent magnets 22 and 23 are attached to the yoke 212.
The pair of yokes 212 are curved inward (toward the magnetic gap) due to the attractive force of the permanent magnets 22 and 23, narrowing the gap between the permanent magnets 22 and 23. In this state, there is a concern that the permanent magnets 22 and 23 may come into contact with the mover.
In such a case, the curvature of the yoke 212 can be reduced by making the yoke 212 thicker (increasing the rigidity), but this makes it difficult to reduce the size and weight of the linear motor. In contrast, according to the first embodiment, the curvature of the workpiece can be corrected with a simple configuration in which a protrusion is provided on the yoke fixing portion, making it possible to reduce the size and weight of the linear motor.

Note that, taking into account the curvature of the yoke 212, it is possible to adjust the gap when the permanent magnet is attached by providing the yoke fixing part 511 with a slope that spreads from the bottom to the top as shown in FIG. 9, or by curving the yoke 312 in advance and leaving it open from the bottom to the top as shown in FIG. 10. However, in the former case, there is a concern that the processing costs will increase in order to improve the processing accuracy of the inclined surface, such as by preparing a dedicated jig. In the latter case, it is difficult to process the yoke 312 (grinding and bending), and it is also difficult to achieve the processing accuracy.

Embodiment 2
Figures 11 to 13 are figures showing the basic configuration of a linear motor according to embodiment 2, with Figure 11(a) being a plan view (top view) showing linear motor 600, (b) being a longitudinal side view of linear motor 600, Figure 12 being a plan view of mover 610, Figure 13(a) being a longitudinal side view of stator 700, and Figure 13(b) being a transverse side view of stator 700, as viewed from the direction B in the figures.
As in the first embodiment, the linear motor according to the second embodiment has a stator and a mover. The stator and the mover are arranged to be movable relative to each other.
Specifically, linear motor 600 according to the second embodiment of the invention has a mover 610 having a permanent magnet 650, and a stator 700 having a coil member 720. Mover 610 is composed of a pair of yokes 620 and a pair of yoke fixing parts 630, and has a square shape in plan view (top view) as shown in Fig. 12 .
In addition, both longitudinal ends of a pair of long, plate-shaped yokes 620 are joined in a known manner so as to be connected by a pair of yoke fixing portions 630 having a rectangular cross-section, forming a frame body (yoke assembly 640) that is U-shaped when viewed in a plane.
The yoke 620 is formed of a magnetic material such as a magnetic steel plate, and the yoke fixing portion 630 may be made of a magnetic material such as a magnetic steel plate, or may be made of a non-magnetic material.
On the inside of the yoke assembly 640 (on the side facing the yoke 620), multiple permanent magnets 650 are arranged at predetermined intervals along the moving direction of the mover 610, the magnetization direction of the multiple permanent magnets 650 is the height direction (depth direction in FIG. 12), and magnets facing each other across a magnetic gap are arranged so that they have different poles. Also, the magnets lined up in the moving direction of the mover 610 are arranged in the order of N pole, N pole, S pole, S pole from the left in the upper row in FIG. 12, and in the order of S pole, S pole, N pole, N pole from the left in the lower row in FIG.
In addition, in FIG. 12, one N pole (S pole) is configured with two permanent magnets, but it may be configured with one permanent magnet, or may be configured with two or more permanent magnets.

As shown in FIGS. 11A and 11B, the linear motor 600 of the second embodiment is constructed by inserting a stator 700 into a magnetic gap formed in a yoke assembly 640 (a mover 610).
As shown in FIG. 13, the stator 700 has a coil member 720 in which a coil 710 is enclosed, and a holder 730 that supports the coil member 720 .
Linear motor 600 according to the second embodiment is a moving magnet type linear motor in which coil 710 is used as stator 700, and yoke assembly 640 having permanent magnets 650 is used as mover 610. Holder 730 is fixed to a mechanical member (not shown) and mover 610 is fixed to a bearing (not shown).
By passing a current through a coil that crosses the magnetic field formed by the opposing permanent magnets, the mover 610 moves in the direction indicated by the arrow in FIG.

11 to 13, a configuration for correcting the curvature of a yoke in linear motor 700 according to embodiment 2 having yoke assembly 640 (mover 610) that is square-shaped in plan view will be described below.
14 is a plan view (top view) of a yoke assembly 645 according to the second embodiment of the invention, and FIG. 15 is a plan view of the yoke assembly 645 of FIG. 14 with a permanent magnet 650 attached thereto.
In the second embodiment, the yoke fixing portion 635 has a protrusion 670 as in the first embodiment. However, the location where the protrusion 670 is formed is different from that in the first embodiment. In the second embodiment, the protrusion 670 is formed in the height direction of the yoke 625 (the depth direction in FIGS. 14 and 15 ) at the end of the side of the yoke fixing portion 635 that contacts the yoke 625, which is closer to the permanent magnet 650.
When the yoke 625 is attached to the side of the yoke fixing part 635, the protrusion 670 causes the gap between the pair of yokes to widen as the yoke 625 moves away from the yoke fixing part 635. That is, in FIG. 14, the upper yoke 625 is curved in an upwardly arched shape, and the lower yoke 625 is curved in a downwardly arched shape. As shown in FIG. 15, in a state in which the permanent magnets 650 are attached to the yoke assembly 645, the curvature of the pair of yokes 625 is corrected by the attraction force between the permanent magnets 650, and the gap between the permanent magnets 650 can be made almost uniform (parallel). In this way, by adjusting the height of the protrusion 670, the gap between the permanent magnets 650 after bending can be adjusted, and contact between the permanent magnets 650 and the stator (coil member) due to narrowing of the gap can be avoided, and a uniform thrust and high output can be obtained. Furthermore, as in the case of the first embodiment, the curvature of the workpiece can be corrected with a simple configuration of providing a protrusion on the yoke fixing portion, without increasing the thickness of the yoke (increasing its rigidity), thereby making it possible to reduce the size and weight of the linear motor.

The disclosed embodiments should be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

10, 600 Linear motor 1, 700 Stator 3, 610 Movable element 22, 23, 650 Permanent magnet 212, 312, 620, 625 Yoke 211, 311, 411, 511 Yoke fixing portion 21, 41, 640, 645 Yoke assembly

Claims (3)

A yoke assembly used in a linear motor in which a stator and a mover are relatively movable,
The yoke fixing portion includes a pair of elongated plate-like yokes arranged opposite each other with a gap therebetween, and a pair of yoke fixing portions that support the pair of yokes in a cantilever manner at one end of the pair of yokes in a short side direction,
A yoke assembly characterized in that a protrusion is formed on a surface of the yoke fixing part that supports the pair of yokes, and the protrusion is configured to cause the pair of yokes to expand the gap from the one end side to the other end side. A yoke assembly used in a linear motor in which a stator and a mover are relatively movable,
The magnetic bearing includes a pair of elongated plate-like yokes arranged opposite each other with a gap therebetween, and yoke fixing portions that support the pair of yokes at both longitudinal ends of the pair of yokes,
A yoke assembly characterized in that a protrusion is formed on a surface of the yoke fixing part that supports the pair of yokes, and the protrusion is configured to widen the gap between the pair of yokes as the pair of yokes move away from the yoke fixing part. 3. A linear motor comprising the yoke assembly according to claim 1 or 2, wherein a plurality of permanent magnets are disposed on each of the opposing surfaces of a pair of yokes that are arranged opposite each other with the gap therebetween, and a coil is disposed in the gap between the plurality of permanent magnets.