JP2006054973A - Linear motor for machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a linear motor for machine tool which is high in positioning accuracy. <P>SOLUTION: This linear motor 10 for a machine tool comprises a stator 13 where a plurality of permanent magnets 12 in the same form being magnetized in the vertical direction to the face of a yoke 11 are arrayed, at equal intervals in the shifting direction of a moving member so that the direction of the magnetization may be different from adjacent permanent magnets 12, on both sides of the plate-shaped yoke 11, and a pair of moving members 16 where armature coils 14 with armature coils 15 wound are counterposed severally to the rows of each permanent magnet 12 provided on both sides of the plate-shaped yoke 11 so that the central axis of each armature coil 15 may be parallel with the direction of the magnetization of each permanent magnet 12. The plate-shaped yoke 11 is provided with grooves 20, and the above permanent magnets 12 are fixed in the grooves 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a linear motor for machine tools. In particular, the present invention relates to a linear motor for a machine tool that is used in a driving device in a machine tool such as a cutting device, a milling machine, a machining center, or a laser processing machine, and whose stator is a permanent magnet type.

  Laser processing machines have been widely used as devices for processing semiconductor workpieces and the like. FIG. 11 is a conceptual diagram showing an example of a conventional laser beam machine. According to the illustrated laser beam machine, a table 122 is provided on a frame 121, and a workpiece (not shown) to be machined is placed on the table 122. Further, an X-axis drive device 123 that is movable in the X-axis direction in a coordinate plane parallel to the workpiece surface to be processed is attached above the frame 121. Further, a Y-axis drive device 124 that can move in the Y-axis direction via attachment parts is attached to the drive device 123, and a Z-axis drive device 125 that can move in the Z-axis direction is attached to the Y-axis drive device 124. A torch 126 for emitting laser light is attached to the shaft driving device 125. In FIG. 11, the wiring of the driving device, the control device, and the member that transmits the laser light are omitted.

  In the laser processing machine having such a configuration, the X-axis drive device 123 and the Y-axis drive device 124 are controlled by a control device (not shown), and a desired laser beam from the torch 126 attached to the tip is applied to the workpiece. Cut into shapes. In order to focus the laser beam, the distance between the torch 126 and the workpiece is controlled by the driving device 125 in the Z-axis direction. In the conventional laser beam machine having such a configuration, a drive device constituted by a rotary servo motor and a ball screw has been used.

  However, the above-described laser processing machine using a rotary servo motor has a limit for high-speed processing, and the fast feed speed is about 20 m / min. Furthermore, when the workpiece is longer than 3 m, there is a problem that the machining accuracy is lowered due to the deflection of the ball screw. Therefore, studies have been made to replace the drive unit with a linear motor.

  The linear motor has a stator in which a plurality of permanent magnets magnetized in a direction perpendicular to the surface of the yoke are mounted on a plate-shaped yoke such as an iron plate at equal pitches so that the directions of magnetization are alternately different from each other; The armature core (magnetic core) made of a magnetic material disposed so as to face the permanent magnet array is composed of a mover in which an armature coil is wound. Since a machine tool requires a large thrust, such a linear motor is preferably used. In a linear motor, position control, speed control, and the like are performed by supplying a current suitable for the position to the armature coil. This position is determined on the assumption that the permanent magnets are magnet arrays of equal pitch. . Therefore, if there is a pitch error, it is difficult to perform high-speed and high-accuracy positioning, and the advantages of the linear motor may not be fully utilized. The pitch (also referred to as a magnet pitch) is the sum of the width of the permanent magnet and the distance between the permanent magnets in the moving direction of the mover.

Patent Document 1 describes a method of polishing a magnet and a spacer at once. According to the method of Patent Document 1, members having the same shape and the same dimensions can be obtained, and therefore accurate feeding can be obtained because there are few individual differences.
JP 2002-281729 A

When the method according to Patent Document 1 is used, the shape and dimensions are almost the same as long as they are within the member processing lot, but this is not the case if the lots are different. Therefore, it is not possible to stably obtain the stator magnet row pitch at equal intervals, resulting in individual differences between individual linear motors and machine tools equipped with these linear motors. Positioning is not possible. Further, when a small amount of foreign matter is mixed or positioning failure occurs when the magnet or spacer is assembled, problems such as the final positional deviation and the high-speed and high-precision positioning, which is the final target, occur due to their integration.
Accordingly, an object of the present invention is to solve these problems and provide a linear motor for machine tools with higher positioning accuracy.

  The present invention is a linear motor for machine tools, wherein a plurality of identically shaped permanent magnets magnetized in a direction perpendicular to the surface of the yoke on both surfaces of a plate-like yoke are different in magnetization direction from adjacent permanent magnets. As described above, the stator arranged at equal intervals in the moving direction of the mover and the armature core wound with the armature coil are arranged so that the central axis of the armature coil is parallel to the magnetization direction of the permanent magnet. And a pair of movers arranged opposite to each row of permanent magnets provided on both sides of the plate-shaped yoke, wherein the plate-shaped yoke has a plurality of grooves, and each permanent magnet Is fixed to the plurality of grooves provided in the plate-like yoke.

  The present invention provides a linear motor for machine tools having a high positioning accuracy, comprising a stator with the magnet row pitch being equally spaced by positioning the permanent magnet between or above the grooves. Can do. Further, according to the linear motor for machine tools according to the present invention, it is preferable that both ends of the magnet row are fixed by plate-like plates, so that the positional tolerance at both ends of the magnet row is preferably suppressed to 1 mm or less, and the magnet end portion This eliminates the variation in leakage flux and enables high-speed positioning feed.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In the drawings, the same members are denoted by the same reference numerals. Note that the present invention is not limited to the scale and number of members shown in the drawings.

  FIG. 1 is a cross-sectional view of a linear motor 10 according to an embodiment of the present invention, cut along a plane parallel to the moving direction of the mover and perpendicular to the permanent magnet fixing surface of the yoke. The linear motor 10 includes a stator 13 composed of a plate-like yoke 11 formed with a plurality of grooves 20 and a plurality of permanent magnets 12, a mover composed of an armature core 14 and an armature coil 15. 16.

  In the illustrated stator 13, a plurality of grooves 20 formed by the member 21 and the magnet fixing surface of the plate-like yoke 11 are formed in the plate-like yoke 11 at equal intervals along the longitudinal direction of the yoke. A permanent magnet 12 is fixed in each groove 20 to form a magnet row 17.

  FIG. 2 shows a conceptual diagram of the plate-like yoke 11, the permanent magnet 12, and the groove 20 constituting the stator 13. FIG. 2A is a cross-sectional view of the stator 13 taken along a plane that is parallel to the moving direction of the mover and is perpendicular to the fixed surface of the permanent magnet 12 of the yoke 11. FIG. 2B is a plan view of the stator 13 as seen from the direction of the arrow X in FIG. The plate-like yoke 11 of the stator 13 is a plate-like member whose longitudinal direction is the moving direction of the mover. As a material for the plate-like yoke 11, a particularly general magnetic material can be used. Examples include, but are not limited to, low carbon steel, silicon steel plate, SUS, and the like.

  The plate-like yoke 11 is provided with a plurality of grooves 20 formed by a plurality of members 21 and a magnet fixing surface of the plate-like yoke 11. In addition, since the member 21 protrudes from the magnet fixing surface of the plate-shaped yoke 11, it is also called a protrusion. The plurality of grooves 20 are for arranging and positioning a plurality of permanent magnets in parallel. The width of the groove 20 preferably has a tolerance within plus 0.1 mm with respect to the width of the permanent magnet 12. If the width of the groove 20 is larger than the width of the permanent magnet 12 plus 0.1 mm, a gap is formed between the end face of the permanent magnet 12 and the groove 20, the position of the permanent magnet 12 is not fixed, and skew variation is caused. This is because the high-speed positioning feed may not be realized. The length of the groove 20 is preferably the same as the length of the permanent magnet 12.

  The groove 20 does not need to be oriented in a direction perpendicular to the moving direction of the mover 16, and can be arranged in parallel with an appropriate skew angle (magnetic field vector angle) of up to 10 degrees in the design of the linear motor. it can. The adjacent grooves 20 are parallel to each other, and the distance between the adjacent grooves 20 can be determined so as to obtain a magnet pitch capable of obtaining desired characteristics when the permanent magnets 12 are disposed in the respective grooves 20. Specifically, the magnet pitch is appropriately determined according to the number of teeth of the armature core 14 of the mover, the number of poles of the permanent magnet 12, and the size and shape of the permanent magnet 12, and the position of the groove 20 is adjusted accordingly. decide. Such a groove 20 can be formed in advance by attaching a member 21 made of a magnetic material to the permanent magnet fixing surface of the plate-like yoke 11 before assembling the stator 13 of the linear motor 10.

  The plurality of permanent magnets 12 are plate-like members each having the same shape and dimensions. As a material of the permanent magnet 12, a permanent magnet such as an Nd-based or Sm-based rare earth-based material, a ferrite-based material, an alnico-based material, or the like can be used. The present invention is particularly effective when an Nd—Fe—B magnet having a high energy product is used. It is particularly preferable to use a magnet obtained by powder metallurgy or a rapid cooling method so as to have a desired composition.

  A permanent magnet 12 is embedded in each groove 20 provided in the plate-like yoke 11, and is usually fixed to the plate-like yoke 11 with an adhesive or the like. The illustrated permanent magnet 12 is in a state in which the surface thereof is inserted and fixed so as to protrude from the groove 20, but the member 21 and the surface of the permanent magnet 12 may be in the same plane. Good.

  The permanent magnets 12 are magnetized in the direction perpendicular to the surface of the plate yoke 11 to which the magnets are fixed, and the magnetization directions of the adjacent permanent magnets 12 are alternately different. The two permanent magnets 12 facing each other via the plate-like yoke 11 have opposite magnetization directions. In FIG. 1, the direction of magnetization of each permanent magnet 12 is indicated by an arrow. The permanent magnet 12 may be magnetized before being fixed to the plate-like yoke 11, or may be magnetized after being fixed to the plate-like yoke 11. Furthermore, it is preferable that the width of the projecting portion (member 21 in the embodiment of FIG. 1) forming the groove is 10 to 70% of the width of the permanent magnet. This is because the magnetic flux flows efficiently and the thrust is not reduced.

  1 and 2, the plate-like yoke 11 and the same magnetic member 21 as the plate-like yoke are used to form a groove 20 formed on the surface of the plate-like yoke 11, and the permanent magnet 12 is inserted therein. The stator 13 has been described. Such a form is preferably used in terms of workability and workability, but the present invention is not limited to such a form. In addition, the form shown below is mentioned, for example.

  FIG. 3A is a cross-sectional view of a stator 13a according to another embodiment cut along a plane parallel to the moving direction of the mover and perpendicular to the surface of the yoke 11 where the permanent magnet 12 is fixed. FIG. 3B is a plan view of the stator 13a as viewed from the direction of the arrow X in FIG. In such an embodiment, the groove 20 is formed by digging into the plate-like yoke 11. Therefore, in this embodiment, the part of the yoke located between each permanent magnet 12 becomes a protrusion. The groove 20 is not the same length as the permanent magnet 12, but is formed in such a length that a gap is formed at one end of the groove 20 even after the permanent magnet 12 is fitted. This is to improve the leakage of magnetic flux at the end of the permanent magnet 12, facilitate plate attachment described later, and make the magnet alignment more accurate. In this case, after the permanent magnet 12 is fixed to the groove 20, the opening can be sealed with a non-magnetic material (aluminum, SUS, resin, etc.) or a magnetic material spacer 22. Further, a plate similar to the plate 18 shown in FIG. 6 described later can be applied to seal the opening. Furthermore, even in a mode in which both ends are openings as in FIG. 2, the openings can be sealed from both sides with spacers, plates, or the like.

  FIG. 4A is a cross-sectional view of a stator 13b according to another embodiment, cut along a plane parallel to the moving direction of the mover and perpendicular to the permanent magnet 12 fixing surface of the yoke 11. FIG. FIG. 4B is a plan view of the stator 13b viewed from the direction of the arrow X in FIG. In such an embodiment, the groove 20 is formed by digging into the plate-like yoke 11. And the permanent magnet 12 can be processed according to the dimension of the groove | channel 20, and it can be inserted so that the convex part of the permanent magnet 12 may be inserted in a groove | channel. In this embodiment, there is no gap between the adjacent permanent magnets 12, and the pitch between the magnets is the same as the magnet width.

  FIG. 5A is a cross-sectional view of a stator 13c according to still another embodiment cut along a plane parallel to the moving direction of the mover and perpendicular to the permanent magnet 12 fixing surface of the yoke 11. FIG. FIG. 5B is a plan view of the stator 13c viewed from the direction of the arrow X in FIG. In such an embodiment, the groove 20 is provided so as to be dug into the plate-like yoke 11 and to form irregularities in the groove 20. Then, the permanent magnet 12 can be processed according to the size of the groove 20, and the concave portion of the permanent magnet 12 can be inserted into the convex portion in the groove 20.

  In the embodiment shown in FIG. 1, a plate (not shown) that extends from one end of the row of permanent magnets 12 to the other end and contacts at least one surface in the width direction of each permanent magnet 12 is provided on the surface of the yoke 11. Be prepared for. FIG. 6 shows a schematic view of members constituting the stator 13. In FIG. 6, the magnet pressing plate 18 is arranged on the surface of the yoke 11 so as to extend in the longitudinal direction of the yoke 11. And the magnet row | line | column 17 is fixed from both sides of the row | line | column 17 of a permanent magnet in contact with the surface of the width direction of each permanent magnet 12. FIG. The plate plate 18 can be fastened to the plate yoke 11 with screws or the like. Since the plate 18 positions all the magnet rows 17 of the stator 13, the shape is such that the positions of both ends of the magnet row 17 are constrained by the positions of the screw holes 19 of the yoke 11 and the plate 18 and the processing accuracy of the respective positioning portions. It is fixed with.

  Although it depends on the length of the stator 13, it is preferable that the deviation of the relative positions of the permanent magnet 12 at one end and the permanent magnet 12 at the other end in the magnet row 17 is within 1 mm. This relative position shift is schematically shown in FIG. If the relative position deviation is larger than 1 mm, the movement of the mover 16 may be disturbed by the influence of the leakage magnetic flux at the end of the magnet row 17. FIG. 8 is a drawing that emphasizes the displacement of the relative position in order to explain the displacement of the relative position between the permanent magnet at one end and the permanent magnet at the other end. Therefore, the scale of the magnitude of the deviation is not as illustrated, and the displacement of the relative positions of the permanent magnets is not limited to the illustrated form.

  The material of the plate 18 may be a non-magnetic material that is easy to work with strength that is worthy of positioning and holding the permanent magnet 12. For example, in order to reduce the width and thickness of the plate 18, a high-strength material such as aluminum or stainless steel can be used, but is not limited thereto. Further, a heat resistant resin such as an epoxy resin can be used for fixing the plate 18 to the plate-like yoke 11. In addition, the plate 18 can be fixed to the plate-like yoke 11 using a bolt or the like. In the illustrated embodiment, the magnet array 17 is sandwiched between two plates, but can be fixed by only one plate.

  The mover 16 is constituted by an armature core 14 having a plurality of teeth around which an armature coil 15 is wound. In the mover 16, a plurality of armature coils 15 are provided, and the central axes of the respective coils 15 are arranged in parallel along the mover moving direction. The armature core 14 can be made of a magnetic material similar to that of the plate-like yoke 11, and a copper wire or the like can be used as the armature coil 15.

  The mover 16 is configured so that the central axes of the plurality of armature coils 15 are perpendicular to the fixed surface of the magnet row 17 of the plate-shaped yoke 11, that is, parallel to the magnetization direction of the permanent magnet 12. It arrange | positions through the space | gap between this magnet row | line | column 17. FIG. One mover 16 is disposed on each side of the stator 13.

  When the linear motor 10 having such a configuration is used as a moving mechanism of a laser processing machine, accurate and high-speed positioning is possible, and it is effective for a three-dimensional moving mechanism.

  A linear motor 10 including the stator 13 having the form shown in FIG. 2 was produced. As the plate-like yoke 11, an iron yoke having a length of 550 mm, a width of 140 mm, and a height of 19 mm was used. The plate-like yoke 11 has a groove 20 having a plus tolerance of 0.04 to 0.07 mm with respect to a width of 18 mm and the same length as the permanent magnet 12, and an iron member 21 having a height of 1 mm. It was formed by fixing to the magnet fixing surface. The member 21 is a protruding member that protrudes from the plate-like yoke 11 and constitutes the groove 20, and its width is 39% with respect to the width of the permanent magnet. The grooves 20 were provided so that the magnet pitch was 25 mm. The skew setting of the groove 20 was 2 ± 0.3 degrees. As the permanent magnet 12, an Nd—Fe—B magnet having a magnet width of 18 ± 0.03 mm × length 100 mm × height × 5 mm was used. The plate 18 was made of aluminum having a width of 20 mm, a thickness of 5 mm, and a length of 548 mm.

  The permanent magnet 12 was disposed in the groove 20 formed on both surfaces of the plate-like yoke 11 so as to be exposed 4 mm from the surface of the member 21. And the both ends of the yoke 11 were fixed with the epoxy resin so that the permanent magnet 12 may be fixed to the upper and lower parts of the yoke 11 using the plate 18. FIG. 7 schematically shows the configuration of the stator 13 after the permanent magnets 12 are arranged and fixed in the grooves 20 provided in the yoke 11. Furthermore, a linear motor 10 was prepared by winding a magnetic core and a coil such as a copper wire around the core as the mover 16 and attaching it to the stator 13.

  As a reference example, a linear motor was manufactured in the same manner as in the example except that the groove width was larger by 0.3 mm at the maximum than the width of the permanent magnet. When the tolerance of the plurality of groove widths provided in the plate-shaped yoke exceeded 0.1 mm, the skew of the permanent magnet was not constant, and it was difficult to accurately position the mover. Further, as a comparative example, a linear motor was manufactured by using a conventional method and manufacturing a stator while inserting a spacer manufactured by machining without providing a groove in the yoke. In this case, the spacer was processed in the same manner as in Japanese Patent Application Laid-Open No. 2002-281729.

  FIG. 9 shows the results of measuring the cogging torque of the linear motor 10 manufactured according to this example and the results of measuring the cogging torque of the linear motor according to the reference example. Moreover, the result of measuring the cogging torque of the linear motor 10 manufactured according to the present embodiment and the cogging torque of the linear motor of the comparative example are shown in FIG.

  The cogging force of the linear motor is a force that periodically acts in the traveling direction or the opposite direction when the mover moves, and the cycle is the pitch of the magnet. The sum of the magnetic attractive forces generated between the magnet and each tooth of the armature core is the cogging force, and the magnetic attractive forces generated by the teeth inside the armature core cancel each other, but are generated at both ends of the armature. Since the magnetic attraction force does not cancel well, it appears as a cogging force of the magnet pitch period. The actual cogging torque measurement is performed by connecting the manufactured linear motor and the evaluation linear motor via a load cell, moving the evaluation linear motor without passing current through the manufactured linear motor, stopping at each measurement pitch, and The relationship between the position and the thrust (indicated value of the load cell) was measured and measured over the entire area where the stator was connected.

  As a result, in the linear motor 10 according to the present embodiment, it is possible to suppress the pulsation of the cogging waveform due to the error such as the magnet pitch that has occurred in the reference example of FIG. 9, and further, the cogging (maximum value)-(minimum value). The reference example 24N was able to be suppressed to 17N in the examples. In FIG. 10, the cogging (maximum value) − (minimum value) was 30 N in the linear motor of the comparative example, but in the example, it could be suppressed to 19 N, so the position and speed could be easily controlled. High-speed positioning as a linear motor has become possible.

  The present invention can be applied to a drive device of a machine tool such as a cutting device, a milling machine, a machining center, or a laser processing machine.

It is a figure explaining the linear motor which concerns on one Embodiment of this invention. The conceptual diagram of the stator by one Embodiment of this invention is shown. FIG. 2A is a cross-sectional view of the stator. FIG. 2B is a plan view of the stator as viewed from the direction of the arrow X in FIG. The conceptual diagram of the stator by another embodiment of this invention is shown. FIG. 3A is a cross-sectional view of the stator. FIG. 3B is a plan view of the stator as viewed from the direction of the arrow X in FIG. FIG. 5 shows a conceptual diagram of a stator according to still another embodiment of the present invention. FIG. 4A is a cross-sectional view of the stator. FIG. 4B is a plan view of the stator as viewed from the direction of the arrow X in FIG. FIG. 6 shows a conceptual diagram of a stator according to still another embodiment of the present invention. FIG. 5A is a cross-sectional view of the stator. FIG. 5B is a plan view of the stator as viewed from the direction of the arrow X in FIG. It is a figure explaining the components which comprise a stator row | line. It is a general-view figure of a stator magnetic circuit. It is a conceptual diagram explaining the shift | offset | difference of the position of a magnet. It is a figure showing the measurement result of cogging torque. It is a figure showing the measurement result of cogging torque. It is a conceptual diagram explaining a laser beam machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Linear motor 11 Plate-shaped yoke 12 Permanent magnet 13 Stator 14 Armature core 15 Armature coil 16 Movable element 17 Magnet row 18 Plate 19 Screw hole 20 Groove 21 Groove forming member 22 Spacer 121 Frame 122 Table 123 X axial direction Drive unit 124 Y-axis direction drive unit 125 Z-axis direction drive unit 126 Torch

Claims (6)

A plurality of identically shaped permanent magnets magnetized in a direction perpendicular to the surface of the yoke on both surfaces of the plate-like yoke are arranged at equal intervals in the moving direction of the mover so that the direction of magnetization differs from that of adjacent permanent magnets. An array of stators,
The armature core around which the armature coil is wound is arranged in each permanent magnet row provided on both surfaces of the plate-like yoke so that the central axis of the armature coil is parallel to the magnetization direction of the permanent magnet. A linear motor for a machine tool comprising a pair of movers arranged to face each other,
The linear motor for machine tools, wherein the plate-shaped yoke has a plurality of grooves, and each permanent magnet is fixed to the plurality of grooves. The linear motor for machine tools according to claim 1, wherein the width of the groove in the moving direction of the mover has a tolerance of plus or less 0.1 mm with respect to the width of each permanent magnet. The linear motor for machine tools according to claim 1 or 2, wherein a plate extending from one end of the row of permanent magnets to the other end and contacting at least one surface in the width direction of each permanent magnet is provided on the surface of the yoke. . 4. The machine tool linear according to claim 3, wherein the plate is arranged in parallel with a moving direction of the mover so that a relative position shift between one end and the other end of the row of the permanent magnets is within 1 mm. motor. The groove of the plate-like yoke is formed by a protrusion located between the permanent magnets, and the width of the protrusion is 10 to 70% of the width of the permanent magnet. A linear motor for machine tools as described in 1. A laser processing machine using the linear motor according to claim 1 as a three-dimensional moving mechanism.

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