JP2011035993A - Linear motor actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear motor actuator which can restrain a force due to the thermal expansion of a table from acting on a motion guide even if a motor coil part generates heat, in its turn, can elongate its life. <P>SOLUTION: The table 4 of the linear motor actuator is divided into a coil hanger 4a from which a motor coil part 8 is hung, and a work mount 4c which includes a mounting face to which a work is attached. The material of the coil hanger 4a of the table 4 and the material of the work mount 4c are varied, and the linear expansion coefficient of the coil hanger 4a of the table 4 is made smaller than the linear expansion coefficient of the work mount 4c of the table 4. Even if the motor coil part 8 generates heat, and the heat of the motor coil part 8 is conducted to the table 4, the amount of thermal expansion in the width direction of the table 4 can be made small. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a linear motor actuator that linearly moves a table to which a workpiece is attached in one axial direction.

  This type of linear motor actuator includes a base to which a stator in which N poles and S poles are alternately formed in one axis direction is attached, a table on which a motor coil portion facing the stator is suspended, and a straight line of the table with respect to the base. A pair of motion guide devices that guide the motion (see, for example, Patent Document 1). The pair of motion guide devices are arranged so as to sandwich the motor coil portion.

  A track rail of a pair of motion guide devices is attached to the base. The pair of track rails are parallel to each other. A moving block is slidably assembled to the track rail via a rolling element capable of rolling motion. A table is attached to the upper surface of the moving block. By interposing the motion guide device, the linear motion of the table can be guided, and the resistance when the table linearly moves with respect to the base can be reduced.

  The motor coil unit has, for example, U, V, and W phase three-phase coils. When a three-phase alternating current having a phase difference of 120 degrees is passed through the three-phase coil, a thrust is generated in the motor coil portion by a magnetic field generated in the stator and a current flowing in the three-phase coil. A slight magnetic clearance is provided between the motor coil portion and the stator. The motor coil section moves linearly with respect to the stator while maintaining a constant clearance with the stator. The pair of motion guide devices also has a role of maintaining a constant clearance between the motor coil portion and the stator.

JP 2008-75666 A

  When a three-phase alternating current is passed through the motor coil section, the motor coil section generates heat due to Joule heat. The heat generated in the motor coil part is transmitted to the table. When heat is transmitted to the table, the table is thermally expanded in the width direction and the moving direction. In particular, when aluminum having a large coefficient of linear expansion is used as the table material, the amount of thermal expansion of the table increases. A pair of motion guide devices are attached to both ends in the width direction of the table. When the table is thermally expanded in the width direction, the pair of motion guide devices are also separated from each other.

  On the other hand, even if the motor coil section generates heat, the base does not expand as much as the table. This is because a gap is interposed between the motor coil portion and the base stator, so that the heat of the motor coil portion is hardly transmitted to the stator.

  As described above, when the motor coil portion generates heat, the table thermally expands in the width direction, whereas the base does not expand as much in the width direction as the table. For this reason, a force in the width direction of the table acts on the pair of motion guide devices. There is an allowable value for the force applied to the motion guide device. When the force applied to the motion guide device exceeds the allowable value, the life of the motion guide device is shortened.

  Accordingly, the present invention provides a linear motor actuator that can suppress the force caused by the thermal expansion of the table from acting on the motion guide device even if the motor coil section generates heat, and thus can extend the service life. Objective.

  In order to solve the above-described problem, an embodiment of the present invention includes a base having a stator in which N poles and S poles are alternately formed in a uniaxial direction, and a plurality of coils facing the stator via gaps. A motor coil part having a table on which the motor coil part is suspended, and the motor coil part is disposed so as to sandwich the motor coil part when viewed from the one-axis direction, and the table linearly moves in the one-axis direction with respect to the base. A pair of motion guide devices for guiding, wherein the table has a coil suspension part on which the motor coil part is suspended, and a work attachment part including an attachment surface to which a work is attached, The material of the coil suspension part and the material of the workpiece attachment part are different from each other, and the linear expansion coefficient of the coil suspension part of the table is the same as that of the table. A small linear motor actuator than the linear expansion coefficient of the click attachment portion.

  In another aspect of the present invention, a base having a stator in which N poles and S poles are alternately formed in a uniaxial direction, a motor coil section having a plurality of coils opposed to the stator via gaps, A table on which the motor coil unit is suspended, and a pair of motion guide devices that are arranged so as to sandwich the motor coil unit as viewed from the one axis direction and guide the table to linearly move in the one axis direction with respect to the base. And the table is provided on both sides in the width direction of the coil suspension portion as viewed from the one axis direction, and the pair of motion guide devices are provided A pair of motion guide device attachment portions to be attached, and the motor core is disposed between the coil suspension portion of the table and the pair of motion guide device attachment portions. Thermal expansion absorbing portion to allow the lower portion hanging said coil extending in the width direction by the heat generated in the pole tip is a linear motor actuator provided.

  According to one aspect of the present invention, since a material having a small linear expansion coefficient is used for the portion of the table where the motor coil portion is suspended (coil suspension portion), the motor coil portion generates heat and the motor Even if the heat of the coil portion is transmitted to the table, the amount of thermal expansion in the width direction of the table can be reduced. Since the force in the width direction of the table acting on the motion guide device can be reduced, the early life of the motion guide device can be prevented. Also, by making the material of the mounting surface of the table different from that of the coil suspension part, the finishing accuracy of the workpiece mounting surface can be increased and the workpiece mounting accuracy can be increased. .

  According to another aspect of the present invention, a thermal expansion absorbing portion that allows the coil hanging portion to extend in the width direction is provided between the coil hanging portion and the pair of motion guide device mounting portions of the table. Even if the motor coil part generates heat and the coil suspension part thermally expands in the width direction, it is possible to make it difficult to change the positions of the pair of motion guide device attachment parts. Since the force in the width direction acting on the motion guide device can be reduced, the early life of the motion guide device can be prevented.

1 is a perspective view of a linear motor actuator according to a first embodiment of the present invention (including a partial cross-sectional view of a table). Front view of the linear motor actuator Top view of stator Schematic table Sectional view along the moving direction of the motor coil The front view of the linear motor actuator of 2nd embodiment of this invention The front view of the linear motor actuator of 3rd embodiment of this invention

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view of a linear motor actuator according to an embodiment of the present invention, and FIG. 2 is a front view thereof. A linear motor stator 2 is mounted on the elongated base 1. A pair of linear guides 5 are attached to the upper surfaces of the side wall portions 1 b at both ends in the width direction of the base 1 as a motion guide device that guides the linear motion of the table 4. The table 4 is attached to the upper surface of the moving block 6 of the pair of linear guides 5. On the lower surface of the table 4, a motor coil portion 8 that is a mover of the linear motor is suspended between the left and right linear guides 5. A magnetic gap g is provided between the stator 2 and the motor coil unit 8. The motor coil unit 8 moves linearly with respect to the stator 2 while keeping the clearance g constant. The linear guide 5 has a role of keeping the clearance g between the motor coil portion 8 and the stator 2 constant.

  As shown in FIG. 2, the cross-sectional shape of the base 1 is composed of a recessed bottom wall portion 1a and a pair of side wall portions 1b provided at both ends in the width direction of the bottom wall portion 1a. The stator 2 is attached to the upper surface of the bottom wall 1a. The track rail 7 of the linear guide 5 is attached to the upper surface of the side wall 1b. The moving block 6 is slidably assembled to the track rail 7. A large number of balls are interposed between the track rail 7 and the moving block 6 so as to be capable of rolling motion (not shown). The moving block 6 is provided with a circuit-shaped ball circulation path for circulating these many balls. When the moving block 6 slides with respect to the track rail 7, many balls roll between the ball rolling groove of the track rail 7 and the loaded ball rolling groove of the moving block 6, and circulate in the ball circulation path. . By interposing a large number of balls between the track rail 7 and the moving block 6, the relative movement of the moving block 6 with respect to the track rail 7 becomes smooth.

  FIG. 3 shows a plan view of the stator 2 attached to the base 1. The stator 2 includes a thin plate-like magnet holding plate 11 and a plurality of plate-like permanent magnets 12 (12a, 12b) arranged in a line on the magnet holding plate 11. The permanent magnet 12 is a rare earth magnet such as a neodymium magnet having a high coercive force. The permanent magnet 12 is magnetized in the vertical direction, and one of the N pole and the S pole is formed on the front side of the permanent magnet 12, and the other of the N pole and the S pole is formed on the back side. The front side N-pole permanent magnets 12a and the front side S-pole permanent magnets 12b are alternately arranged in the longitudinal direction of the base 1 so that N poles and S poles are alternately formed in the longitudinal direction of the base 1. The permanent magnet 12 is fixed to the magnet holding plate 11 by fixing means such as adhesion, bolts, and press-fitting.

  The magnet holding plate 11 is made of a magnetic material such as general structural rolled steel or silicon steel. The permanent magnet 12 fixed to the magnet holding plate 11 is covered with a cover plate 13. The cover plate 13 is also fixed to the magnet holding plate 11 by fixing means such as adhesion, bolts, and press fitting.

  As shown in FIG. 2, the table 4 is attached to the upper surface of the moving block 6 of the linear guide 5. The table 4 includes a coil suspension portion 4a at the center in the width direction, a pair of linear guide attachment portions 4b as a pair of motion guide device attachment portions in the width direction of the coil suspension portion 4a, and a pair of linear guide attachment portions. A pair of work attachment portions 4c coupled to 4b. In this embodiment, the coil suspension part 4a and the pair of linear guide attachment parts 4b are made of the same material, and the pair of workpiece attachment parts 4c are made of a material different from that of the coil suspension part 4a and the pair of linear guide attachment parts 4b. Become. The material of the coil suspension part 4a and the pair of linear guide attachment parts 4b has a smaller linear expansion coefficient than the material of the pair of work attachment parts 4c.

Specifically, a general structural material such as aluminum or iron is used as the material of the pair of work attachment portions 4c, and CFRP (Carbon) is used as the material of the coil suspension portion 4a and the pair of linear guide attachment portions 4b. Fiber Reinforced Plastics), ceramic, invar material, or iron is used. The linear expansion coefficient of aluminum is 24.56 × 10 ⁻⁶ (/ ° C.), and the linear expansion coefficients of CFRP (Carbon Fiber Reinforced Plastics) and iron are 0.2 × 10 ⁻⁶ (/ ° C.) and 11-13, respectively. × 10 ^-6 (/ ° C). The coefficient of thermal expansion of the coil suspension part 4a is preferably 11 to 13 × 10 ⁻⁶ (/ ° C.) or less. When CFRP is used as a material having a small linear expansion coefficient, the specific gravity is small, so that the weight of the table 4 can be reduced.

  A motor coil portion 8 is suspended from the coil suspension portion of the table 4. The motor coil section 8 is coupled to the coil suspension section 4a of the table 4 by, for example, bolt coupling. A counterbore 21 (see FIG. 1) for fixing the motor coil portion 8 is processed in the coil suspension portion 4a of the table 4. The bolt head sits on this counterbore 21. A linear guide 5 is attached to the linear guide attachment portion 4 b of the table 4. A counterbore 22 (see FIG. 1) for fixing the linear guide 5 is processed in the linear guide mounting portion 4b. The head of the bolt for fixing the linear guide sits on this counterbore. In this embodiment, the coil suspension portion 4a and the linear guide attachment portion 4b of the table 4 are made of the same material, and are formed in a single rectangular plate shape.

  As shown in FIG. 4, the work attachment portion 4 c is formed in a C shape having a recess 23 corresponding to the thickness of the linear guide attachment portion 4 b of the table 4. The work attachment portions 4c are attached to both ends in the width direction of the pair of linear guide attachment portions 4b. The workpiece attachment portion 4c is fixed to the linear guide attachment portion 4b by fixing means 25 such as bolts, adhesives, and press-fitting. A fastening portion 24 (see FIG. 1) such as a screw hole for attaching the workpiece to the table 4 is processed on the upper surface of the workpiece attachment portion 4c. In order to attach the workpiece to the table 4 with high accuracy, the workpiece attachment surface 4d on the upper surface of the workpiece attachment portion 4c is subjected to surface grinding. The pair of workpiece attachment surfaces 4d are arranged in the same plane. By providing the pair of work attachment surfaces 4d only at both ends in the width direction of the table 4, the surface to be surface-ground can be reduced and the work attachment surfaces 4d can be easily arranged in one plane.

  After attaching the workpiece attachment portion 4c to the linear guide attachment portion 4b of the table 4, it is desirable that the upper surface of the workpiece attachment portion 4c be surface ground with reference to the lower surface of the linear guide attachment portion 4b. This is because the position of the upper surface of the work mounting portion 4c can be determined based on the upper surface of the moving block 6 of the linear guide 5.

  For the linear motor, it is important to keep a slight gap g between the stator 2 and the motor coil unit 8 constant. In order to keep the clearance g constant, it is necessary to increase the accuracy of each component. In order to keep the gap g constant, the lower surface of the coil suspension portion 4a of the table 4 may be ground with reference to the lower surface of the linear guide mounting portion 4b of the table 4.

  However, when CFRP is used for the material of the coil suspension part 4a and the linear guide attachment part 4b, it is better not to grind for the following reasons. CFRP is a composite material formed by impregnating a carbon fiber with a plastic material and then curing it. CFRP is manufactured by laminating a number of intermediate materials made by impregnating plastic with tape or woven fabric with carbon fibers aligned in one direction, placing them in an autoclave, which is a pressurized container, and pressurizing at high temperatures. -The method of hardening and manufacturing is mentioned. The small coefficient of linear expansion of CFRP when heated is derived from the laminated structure of CFRP. This is because when CFRP is ground, the balance in the thickness direction is shifted and distortion occurs in CFRP. In addition, when ground, the surface of the carbon fiber or resin becomes fuzzy due to the fiber.

  In addition, when CFRP is used as the material of the coil suspension portion 4a and the linear guide mounting portion 4b of the table 4, a spacer for adjusting the clearance between the coil suspension portion 4a of the table 4 and the motor coil portion 8 is provided. It may be interposed. By interposing the spacer, not only the clearance can be adjusted, but also a case where there is a step between the motor coil portion 8 and the moving block 6 of the linear guide 5 can be handled.

  Position detection means such as a linear scale for detecting the position of the table 4 with respect to the base 1 is attached to the table 4. The position signal detected by the position detection means is sent to a driver that drives the linear motor. The driver controls the current supplied to the motor coil unit 8 based on, for example, a position command from a host controller.

  FIG. 5 shows a cross-sectional view along the moving direction of the motor coil unit 8. The motor coil unit 8 includes a core 31 made of a magnetic material such as silicon steel, and coils 32a, 32b, and 32c wound around the salient poles 31a, 31b, and 31c of the core 31. The core 31 includes a base plate 31d attached to the lower surface of the table 4, and the comb-shaped salient poles 31a, 31b, 31c projecting downward from the base plate 31d. Each of the three salient poles 31a, 31b, 31c is wound with any of the U-phase, V-phase, and W-phase coils 32a, 32b, 32c. Three-phase alternating current having a phase difference of 120 degrees is passed through the three coils 32a, 32b, and 32c. After the coils 32a, 32b, and 32c are wound around the salient poles 31a, 31b, and 31c, these are resin-sealed.

  A pair of auxiliary cores 34 may be attached to the lower surface of the table 4 with the motor coil portion 8 interposed therebetween. The auxiliary core 34 is made of a magnetic material such as general structural rolled steel or silicon steel, and reduces the cogging force generated in the core 31.

  When a three-phase alternating current is passed from a driver (not shown) to the motor coil unit 8, a thrust that linearly moves in the motor coil unit 8 is generated by the magnetic field generated in the permanent magnet and the current flowing in the motor coil unit 8. The table 4 obtains thrust from the motor coil unit 8 and moves linearly. The linear movement of the table 4 relative to the base is guided by a pair of linear guides 5.

  When a three-phase alternating current is passed through the motor coil unit 8, the motor coil unit 8 generates heat, and the heat of the motor coil unit 8 is transmitted to the table 4. As shown in FIG. 2, by using a material having a low coefficient of linear expansion for the coil suspension portion 4a and the linear guide attachment portion 4b of the table 4, the table 4 expands in the width direction even when heat is transmitted to the table 4. Less amount to do. For this reason, the force in the width direction applied from the table 4 to each of the pair of left and right linear guides 5 can also be reduced. In particular, by using a material having a low linear expansion coefficient for the coil suspension part 4a and the pair of linear guide attachment parts 4b of the table 4, the amount of expansion between the pair of linear guide attachment parts 4b in the width direction is minimized. Can do. For this reason, the lifetime of a linear guide can be lengthened. Further, by using a general structural material such as aluminum or iron as the material of the work attachment portion 4c of the table 4 to which the work is attached, the work attachment accuracy can be increased.

  FIG. 6 shows a linear motor actuator according to a second embodiment of the present invention. In this embodiment, the material of the linear guide attachment part 41b and the workpiece attachment part 41c of the table 41 is the same. These are made of general structural materials such as aluminum and iron. The material of the coil suspension portion 41a of the table 4 is not a general structural material, but is any one of a low linear expansion coefficient, for example, CFRP (Carbon Fiber Reinforced Plastics), ceramic, invar material, and iron.

  In this embodiment, the linear guide attachment part 41b and the work attachment part 41c of the table 41 are integrated. These are arranged on both sides in the width direction of the coil suspension portion 41a. Both the lower surface of the linear guide mounting portion 41b and the upper surface of the workpiece mounting portion 41c are surface ground.

  Grooves 42 for receiving the coil suspension portions 41a are formed on the opposing surfaces of the pair of linear guide attachment portions 41b on the left and right. The coil suspending portion 41a is fixed to the pair of linear guide mounting portions 41b by fixing means such as press fitting and bonding.

  The other base 1, the stator 2, the pair of linear guides 5, and the motor coil unit 8 are the same as those of the linear motor of the first embodiment, and thus the same reference numerals are given and the description thereof is omitted.

  Also in this embodiment, heat is transmitted to the table 41 when the motor coil unit 8 generates heat. However, since a material having a low linear expansion coefficient is used for the coil suspension portion 41a of the table 41, even if heat is transmitted to the table 41, the amount of expansion of the table 41 in the width direction is reduced, and the left and right sides of the table 41 are left and right. The force in the width direction applied to each of the pair of linear guides 5 is also reduced. However, in this embodiment, it is necessary to make the distance α from the groove 42 of the linear guide mounting portion 41b of the table 41 to the linear guide fastening bolt of the linear guide mounting portion as short as possible. This is because if the distance α is long, the amount that the distance α is extended by the heat transmitted from the motor coil portion 8 increases, and a force acts on the linear guide 5 in the width direction.

  According to this embodiment, by integrating the linear guide mounting portion 41b and the workpiece mounting portion 41c of the table 41, the upper surface of the moving block 6 and the upper surface of the workpiece mounting portion 41c of the linear guide 5 can be accurately positioned. Can do. Furthermore, since a material having a low linear expansion coefficient is used only for the coil suspension portion 41a, the amount of expensive material used can be minimized, and the material cost can be reduced.

  FIG. 7 shows a linear motor actuator according to a third embodiment of the present invention. In this example, the table 51 is divided into three as a whole like the linear motor actuator of the second embodiment. The three divided materials are all the same, and general structural materials such as aluminum and iron are used.

  The linear guide attachment part 51b and the work attachment part 51c of the table 51 are integrally formed. A pair of linear guide attachment portions 51b and workpiece attachment portions 51c on the left and right are disposed on both sides of the coil suspension portion 51a. The lower surface of the linear guide mounting portion 51b and the upper surface of the workpiece mounting portion 51c of the table 51 are surface ground.

  Grooves 52 for receiving the coil suspension 51a are formed on the opposing surfaces of the pair of linear guide attachment portions 51b on the left and right. The width of the groove 52 is the same as the height of the plate-like coil suspension 51a. When the coil suspension 51a is sandwiched between the pair of linear guide attachment portions 51b, a slight gap s is generated between the bottom of the groove 52 and the coil suspension 51a. When heat is transmitted from the motor coil 8 to the coil suspension 51a, the coil suspension 51a expands in the width direction so as to fill the gap s. For this reason, even if the coil suspension part 51a is thermally expanded, force in the width direction does not act on the linear guide 5. In order to reliably support the coil suspension 51a with the pair of linear guide attachment portions 51b, the gap s may be filled with a material that is easily elastically deformed, such as rubber. The groove 52 of the pair of linear guide attachment portions 51b and the clearance s between the pair of linear guide attachment portions 51b and the coil suspension portion 51a allow thermal expansion absorption to allow the coil suspension portion 51b to extend in the width direction. Parts.

  Since the other stator 2, the base 1, the pair of linear guides 5, and the motor coil unit 8 are the same as those of the linear motor of the first embodiment, the same reference numerals are given and the description thereof is omitted.

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Stator, 4, 41, 51 ... Table, 4a, 41a, 51a ... Coil suspension part, 4b, 41b, 51b ... Linear guide attachment part (motion guide apparatus attachment part), 4c, 41c, 51c: Work mounting portion, 5 ... Linear guide (motion guide device), 6 ... Moving block, 7 ... Track rail, 8 ... Motor coil portion, 41 ... Table, 52 ... Groove (thermal expansion absorbing portion), s ... Gap ( Thermal expansion absorption part)

Claims (6)

A base having a stator in which N poles and S poles are alternately formed in a uniaxial direction;
A motor coil portion having a plurality of coils opposed to the stator via gaps;
A table on which the motor coil unit is suspended;
A pair of motion guide devices arranged so as to sandwich the motor coil portion when viewed from the one axis direction, and guiding the table to linearly move in the one axis direction with respect to the base;
The table has a coil suspension part on which the motor coil part is suspended, and a work attachment part including an attachment surface to which a work is attached,
The material of the coil suspension part of the table and the material of the work attachment part are different from each other,
A linear motor actuator in which a linear expansion coefficient of the coil suspension part of the table is smaller than a linear expansion coefficient of the work mounting part of the table. The table has a pair of motion guide device attachment portions to which the pair of motion guide devices are attached and is provided on both sides of the coil suspension portion in the width direction when viewed from the uniaxial direction.
The linear motor actuator according to claim 1, wherein the pair of motion guide device attachment portions of the table are formed integrally with the coil suspension portion. The table has a pair of motion guide device attachment portions to which the pair of motion guide devices are attached and is provided on both sides of the coil suspension portion in the width direction when viewed from the uniaxial direction.
The linear motor actuator according to claim 1, wherein the pair of motion guide device attachment portions of the table are formed integrally with the workpiece attachment portion of the table.   The spacer for adjusting the clearance gap between the said motor coil part and the said stator is interposed between the said coil suspension part and the said motor coil part of the said table. The linear motor actuator in any one of thru | or 3.   5. The linear motor actuator according to claim 1, wherein a material of the coil suspension portion of the table is any one of CFRP (Carbon Fiber Reinforced Plastics), ceramics, invar material, and iron. . A base having a stator in which N poles and S poles are alternately formed in a uniaxial direction;
A motor coil portion having a plurality of coils opposed to the stator via gaps;
A table on which the motor coil unit is suspended;
A pair of motion guide devices arranged so as to sandwich the motor coil portion when viewed from the one axis direction, and guiding the table to linearly move in the one axis direction with respect to the base;
A pair of movements in which the table is provided on both sides of the coil suspension part in which the motor coil part is suspended and the width direction of the coil suspension part as viewed from the one axis direction, and the pair of motion guide devices are attached. A guide device mounting portion;
Between the coil suspension part of the table and the pair of motion guide device attachment parts, a thermal expansion absorption part that allows the coil suspension part to extend in the width direction due to heat generated in the motor coil part A linear motor actuator provided with

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