JP2008245475A - Moving coil linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moving coil linear motor which is small and light and can be easily assembled.
A movable coil type having a stator having a magnetic gap g in which a sinusoidal magnetic flux density distribution appears along a predetermined direction, and a mover 8 disposed in the magnetic gap and including a multiphase coil 82. In the linear motor 1, the stator 2 is fixed to a yoke 6 a made of a ferromagnetic material, and permanent magnet members 5 a in which permanent magnets 7 a and 70 a having different magnetization directions are alternately arranged along the moving direction of the mover 8. A plurality of divided units 3a having at least a pair of permanent magnet members 5a opposed via a magnetic gap g and having a nonmagnetic frame 4 made of a metal material having a specific gravity smaller than that of the yoke, and a nonmagnetic frame 4 supports the base member 41 having the groove 43 into which a part of the multiphase coil 82 extending along the moving direction of the mover 8 is inserted, and the permanent magnet member 5a. The side member 42 fixed to the both sides | surfaces of this is included.
[Selection] Figure 3

Description

  The present invention relates to a moving coil type linear motor used as a stage driving unit of a semiconductor manufacturing apparatus, for example.

  In a semiconductor manufacturing facility, as a means for transporting a substrate such as glass to a predetermined position, the X stage that moves in a predetermined direction with respect to the base and the X stage move in another direction (orthogonal direction) with respect to the stage. An XY stage apparatus having a Y stage is used. Since a two-axis stage device requires a precise positioning operation and high-speed driving over a long stroke, a multipolar linear DC motor (hereinafter simply referred to as a linear motor) is used as a driving means for each stage. In general, when a responsiveness and high positioning accuracy are required, a moving coil linear motor is used. In this moving coil type linear motor, a permanent magnet having the same magnetization direction is fixed to each of a pair of yokes so that N poles and S poles are alternately arranged along the stroke direction and opposite poles face each other. A stator having a magnetic circuit and a mover having a multi-phase coil arranged in a magnetic gap are provided.

  In particular, since the X-axis linear motor is mounted on the Y-axis stage and needs to be small and light, it is conceivable to first reduce the size of the magnetic circuit constituting the stator. However, in a magnetic circuit in which only permanent magnets having the same magnetization direction are combined, a large-sized permanent magnet having a complicated shape may be used in order to make the magnetic flux density distribution in the magnetic gap sinusoidal and to increase the magnetic flux density in the magnetic gap. Necessary. Therefore, a magnetic circuit structure in which a plurality of permanent magnets are arranged along the moving direction while rotating the polarity direction by 90 ° has been proposed (see Patent Document 1).

  Also, in a normal magnetic circuit, a yoke that is thicker than necessary is used to prevent saturation of the magnetic flux, so that the weight of the magnetic circuit increases and the yoke is exposed to the outside air. Is likely to occur. Therefore, a structure has been proposed in which a yoke constituting the stator is formed into a U shape by plastic working, and this yoke is housed in a frame made of a U-shaped nonmagnetic material (for example, aluminum) (Patent Document 2). reference).

JP-A-9-308218 (pages 2 and 3, FIG. 1) Japanese Unexamined Patent Publication No. 2000-299973 (pages 4-5, FIG. 1)

  However, as described in Patent Document 1, in the case of a linear motor having a so-called Halbach magnetic circuit, the yoke can be made thin, so that the stator can be reduced in weight somewhat, but that alone can reduce the weight. This is not sufficient, and it is not sufficient in terms of downsizing the magnetic circuit (particularly, reducing the width dimension in the direction perpendicular to the moving direction of the mover). Further, as described in Patent Document 2, the magnetic circuit is housed in the U-shaped aluminum frame to reduce the weight of the stator. However, the Halbach magnetic circuit is formed in the aluminum frame. For this reason, there is a problem that a great number of man-hours are required. This is because, in the Halbach magnetic circuit, the magnetic poles are arranged so that the magnetic poles of the same polarity are adjacent to each other, so that it is extremely difficult to fix all the permanent magnets to the yoke due to the magnetic repulsive force.

  Accordingly, an object of the present invention is to provide a moving coil type linear motor that is small and light in weight and that allows easy assembly of a stator.

In order to achieve the above object, a moving coil linear motor according to the present invention includes a stator having a magnetic gap in which a sinusoidal magnetic flux density distribution appears along a predetermined direction, and a multi-pole arranged in the magnetic gap. In a moving coil type linear motor having a mover including a phase coil,
The stator is fixed to a yoke made of a ferromagnetic material, and is opposed to at least a permanent magnet member in which permanent magnets having different magnetization directions are arranged along the moving direction of the mover via the magnetic gap. A plurality of divided units having a pair of the permanent magnet members and having a nonmagnetic frame made of a metal material having a specific gravity smaller than that of the yoke,
The non-magnetic frame includes a base member having a groove into which a part of the multiphase coil is inserted, and side members that support the permanent magnet member and are fixed to both side surfaces of the base member. To do.

  In the present invention, the yoke is preferably made of a steel material, and the nonmagnetic frame is preferably made of aluminum or an alloy thereof.

  In the present invention, the permanent magnet must include R (R is one or more elements of rare earth elements such as Nd), T (T is Fe or Fe and Co), and B. It is preferably made of an RTB-based sintered magnet as a component.

  According to the present invention, the stator constitutes a magnetic circuit with permanent magnet members formed by alternately arranging permanent magnets having different magnetization directions along the moving direction of the mover on the yoke made of a ferromagnetic material. The yoke can be made thin, and a plurality of magnetic circuit members are held by a nonmagnetic frame made of a metal material having a specific gravity smaller than that of the yoke, so that the linear motor can be reduced in size and weight.

  In addition, since the nonmagnetic frame is formed of a base member that supports the magnetic circuit and a side member that is fixed to the side surface thereof, the magnetic circuit can be easily assembled.

  Further, the base member of the nonmagnetic frame is provided with a concave groove into which a part of the movable coil is inserted, and the width dimension of the linear motor can be reduced, so that the size can be further reduced.

  Details of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a side view of an XY stage provided with a linear motor according to an embodiment of the present invention, FIG. 2 is an arrow view of FIG. 1 viewed from the direction A, and FIG. FIG. 4 is a diagram for explaining the assembly procedure of the permanent magnet member, and FIGS. 5 to 7 are diagrams for explaining the assembly procedure of the stator.

  The XY stage shown in FIG. 1 is a movable table 10 driven along the Y-axis direction, a stator 2 installed at both ends thereof, and a movable that moves along the X-axis direction (direction perpendicular to the paper surface). A moving table 11 driven by a linear motor 1 having a child 8 is provided. The moving table 11 is connected to the mover 8 via arms 12 fixed at both ends thereof.

  As shown in FIG. 2, the linear motor 1 includes a stator 2 in which a plurality of divided units 3 a, 3 b, 3 c are connected along the X-axis direction, and a magnetic gap g formed inside the stator 2 in the X-axis direction. Is provided with a movable element 8 that moves along the axis. As shown in FIG. 3, the mover 8 includes a multiphase coil 82 fixed to a holder 81. The multi-phase coil 82 has a plurality of flat coils (not shown) arranged in the X-axis direction, and each flat coil (for example, a three-phase coil) is thrust in the X-axis direction when the coil of each phase is energized. It is wired so as to occur. The linear motor 1 detects a magnetic pole position of a permanent magnet constituting a stator by a magnetic field detection element (for example, a Hall element) provided on the mover, and changes the direction of the current flowing in each coil, thereby moving the mover 8. Is driven to move in the X-axis direction.

  The structure of the stator 2, which is a characteristic part of the present invention, will be described with reference to FIGS. The stator 1 is formed by connecting a plurality of (for example, three) divided units 3a, 3b, and 3c along the X-axis direction (see FIG. 2). Each divided unit is assembled in the state shown in FIG. 3 and then installed on the moving stage 10 so as to have the posture shown in FIG. Since each divided unit has the same structure (however, the lengths need not be the same), the divided unit 3a will be described, and the description of the other divided units will be omitted.

  The division unit 3a includes a nonmagnetic frame 4 (length L1) made of a material having a specific gravity smaller than that of the steel material, and permanent magnet members 5a and 5b having a length L2 provided on the inside thereof. The permanent magnet member 5a (5b) is a main magnet 7a magnetized in the thickness direction on one surface of a yoke 6a (6b) formed in a flat plate shape made of a ferromagnetic material such as a steel material (for example, SS material). (7b) and spacer magnets 70a (70b) magnetized in the direction orthogonal to the magnetization direction (X-axis direction) are formed alternately. The main magnet 7a (7b) has N and S poles arranged alternately along the X-axis direction, and the spacer magnet 70a (70b) is arranged so that the same polarity magnetic poles face each other across the main magnet 7a (7b). Has been. Further, the main magnet 7a (7b) and the spacer magnet 70a (70b) that are opposed to each other with the magnetic gap g interposed therebetween are arranged so that magnetic poles of different polarities face each other.

  Since the permanent magnet member forms a so-called Halbach magnetic circuit, the magnetic gap g is high (for example, 0.8 to 0.8) even if the thickness of the yoke is less than half that of the permanent magnet. A magnetic flux density (0.9 T) can be obtained, and a high thrust can be obtained. Further, according to this magnetic circuit, a magnetic flux density distribution approximating a sine wave can be obtained in the magnetic gap g even if a simple rectangular permanent magnet is used. Note that the length of the permanent magnet on one end side may be shorter than that of other permanent magnets, whereby the magnetic flux density distribution (X-axis direction) in the magnetic gap g can be made closer to a sine wave.

  As shown in FIG. 3, the nonmagnetic frame 4 is made of a material having a specific gravity smaller than that of a steel material, and is a U-shaped member including a prismatic base member 41 and flat side members 42 fixed to both sides thereof. is there. The base member 41 is provided with a concave groove 43 extending in the X-axis direction (a direction perpendicular to the paper surface), and the width W3 of the concave groove is a part of the multiphase coil 82 (ineffective of the flat coil that does not contribute to thrust). The dimension is set such that the conductor portion) enters. The width W1 of the side member 42 is set to be the sum of the width Wm of the permanent magnet member 5b and the width W2 of the base member 31. The thickness t (stator thickness) of the split unit 2 is such that the dimension {t−2 (tm + t3 + t2)} of the magnetic gap g becomes as narrow as possible without increasing the thrust so that the permanent magnet does not contact the coil unit. It is set to such a dimension. According to this divided unit, since the base member 41 is provided with the concave groove 43 extending in the X-axis direction (direction perpendicular to the paper surface), the length La of the movable table 11 can be shortened, and the space occupied by the stage Can be narrowed.

  The above-mentioned division unit can reduce the assembly man-hour by assembling in the procedure shown in FIGS. First, as shown in FIG. 4 (a), a main magnet 7a is fixed to one surface of each yoke 6a with a predetermined length (magnet width) at a predetermined interval, and is a flat plate made of a non-magnetic material (for example, plastic). The opposing main magnets 7a are magnetically attracted and integrated by opposing the magnetic poles of different polarities across the spacer 10 having a thickness ts). Next, as shown in FIG. 4B, the permanent magnet member 5a having the thickness ta is assembled by inserting the spacer magnet 70a between the main magnets 7a.

  Further, as shown in FIG. 5, the base member 31 and two side plates 42 each having two rows of drill holes 421 and drill holes 422 are prepared (b), and formed on the side surface of the base member 41 from the drill holes 421. The nonmagnetic frame 4 is assembled by screwing bolts (not shown) into the female screws.

  Next, as shown in FIG. 6, a pair of permanent magnet members 5 a in which a spacer 10 is sandwiched between a permanent magnet 7 a and a permanent magnet 7 b (not shown) fixed to the yoke 6 a are attached from above the nonmagnetic frame 4. Lower it in the direction indicated by the white arrow. In this case, the permanent magnet member 5 a is placed on the upper surface of the base member 41 by making the thickness ta of the permanent magnet member 5 a smaller than the thickness t 1 of the base member 31. In this state, as shown in FIG. 7, a bolt (not shown) is screwed into the female screw 61 of the yoke 6a (a) from a drill hole 422 (shown by a one-dot chain line), and the permanent magnet member 5a is moved to the side member 42 side (white By pulling in the direction of the pulling arrow), the interval t5 between the permanent magnets is increased (t5> ts), and the state where the spacer 9 enters the concave groove 43 of the base member 41 appears. Therefore, a part of the stator 2 can be assembled by pulling out the spacer 9 in a direction perpendicular to the paper surface. The other permanent magnet member 5b is also incorporated into the nonmagnetic frame 4 in the same procedure as described above, whereby the divided unit 3a is obtained. The stator 2 is manufactured by assembling the other divided units 3b and 3c and connecting them in series in the same procedure.

  According to the stator described above, the permanent magnet member 5a (5b) is held by the nonmagnetic frame 4 that is lighter than the other members (yoke and permanent magnet). Therefore, the stator simply formed by the yoke and the permanent magnet. In addition to being able to be smaller and lighter than the above, the non-magnetic frame 4 is provided with the concave groove 43 that accommodates a part of the mover (part that does not contribute to thrust), so that the entire width of the motor can be suppressed, and the stage Space saving of the apparatus can be achieved.

  In addition, the non-magnetic frame is formed of a base member and side members fixed to both side surfaces of the base member, and the permanent magnet member is assembled with a spacer sandwiched between a pair of permanent magnets. In addition, the magnetic circuit can be easily mounted inside the frame.

  The dimension t4 of the concave groove 43 may be any dimension that is wider (not in contact with) the multiphase coil 82 as shown in FIG. 3, and the stator can be made lighter by increasing this dimension. . However, when this dimension is increased to, for example, about t5 in FIG. 3, it is predicted that the side member 42 will fall to the coil side. Therefore, it is necessary to set the dimension so that the side member 42 does not fall.

  In the above stator, the non-magnetic frame 4 is formed of an aluminum alloy (for example, A5052), and the size of each part is set in the following range, for example, so that the linear motor can be reduced in size and weight more reliably. be able to. The base member 41 has w2 = 50 to 60 mm, t1 = 90 to 100 mm, the groove width w3 = 20 to 30 mm, and the side member 42 has a thickness t2 = 10 to 20 mm and a width w1 = 150 to 160 mm. The permanent magnet member 5a (5b) has a thickness tm = 20 to 30 mm, a width Wm = 90 to 100 mm, and a length Lm = 20 to 30 mm and a thickness t3. = 10-15 mm yoke (SS material).

  By configuring the stator in this way, motor performance with a maximum thrust of 1100 N or more and a stroke of 2100 mm or more can be obtained. The stator has a thickness t = 120 to 130 mm, a width w1 = 150 to 160 mm, the total weight is 250 to 260 kg, and the weight combined with the mover (for example, length 1200 mm) is much less than 300 kg. The total width w of the motor can be suppressed to 210 to 220 mm, and the stage device can be greatly reduced in size and weight.

  In the present invention, the nonmagnetic frame may be formed of a material having a specific gravity smaller than that of the yoke material (for example, carbon steel, specific gravity is 7.85). However, from a practical standpoint (cost, rigidity, etc.), an aluminum alloy (specific gravity) It is preferable to form in 2.8). However, other non-magnetic metal materials (for example, Mg alloy: specific gravity is about 2/3 that of aluminum alloy) can be used, and plastic materials (for example, FRP, specific gravity 1.5 to 1.9) or ceramics can be used. It is also possible to form with a material (for example, zirconia: specific gravity 3.8).

  In the present invention, the permanent magnet can be formed of a known permanent magnet, for example, a rare earth magnet, and in particular, R (R is one or more elements selected from rare earth elements such as Nd. ), T (T is Fe or Fe and Co.) and R-T-B based sintered magnets containing B as essential components are suitable.

It is a side view of the XY stage provided with the linear motor concerning embodiment of this invention. It is the arrow line view which looked at FIG. 1 from A direction. FIG. 3 is a sectional view taken along line B-B in FIG. 2. (A) is a figure which shows the state in the middle of the assembly of a permanent magnet member, (b) is a figure which shows the state which assembled the permanent magnet member. It is a figure which shows the state at the time of the assembly start of a stator, (a) is a front view, (b) is a side view. It is a figure which shows the state in the middle of the assembly of a stator, (a) is a front view, (b) is a side view. It is a figure which shows the state at the time of completion | finish of an assembly of a stator, (a) is a front view, (b) is a side view.

Explanation of symbols

1: linear motor, 2: stator, 3a, 3b, 3c: divided unit,
4: non-magnetic frame, 41: base member, 42: side member, 421, 422: drill hole, 43: concave groove,
5a, 5b: permanent magnet member, 6a, 6b: yoke, 61: female screw 7a, 7b: main magnet, 70a, 70b: spacer magnet,
8: Movable element, 81: Coil holder, 82: Multi-phase coil,
9: Spacer,
10, 11: Moving table, 12: Arm

Claims (3)

In a movable coil linear motor having a stator having a magnetic gap in which a sinusoidal magnetic flux density distribution appears along a predetermined direction, and a mover including a multiphase coil disposed in the magnetic gap,
The stator is fixed to a yoke made of a ferromagnetic material, and is opposed to at least a permanent magnet member in which permanent magnets having different magnetization directions are arranged along the moving direction of the mover via the magnetic gap. A plurality of divided units having a pair of the permanent magnet members and having a nonmagnetic frame made of a metal material having a specific gravity smaller than that of the yoke,
The nonmagnetic frame includes a base member having a groove into which a part of the multiphase coil is inserted, and a side member that supports the permanent magnet member and is fixed to both side surfaces of the base member. Moving coil type linear motor. The moving coil linear motor according to claim 1, wherein the yoke is made of a steel material, and the non-magnetic frame is made of aluminum or an alloy thereof. The permanent magnet contains R (R is one or more elements selected from rare earth elements such as Nd), T (T is Fe or Fe and Co), and B as essential components. 2. The moving coil linear motor according to claim 1, wherein the moving coil linear motor is made of an RTB-based sintered magnet.

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