JP2011193691A - Linear actuator unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear actuator unit that minimizes deflection of a magnet rod and can obtain a smooth motion and a high positional accuracy of a slide member. <P>SOLUTION: The linear actuator unit comprises: a guide shaft that has a hollow part and is formed with openings along the axis direction; the slide member that can reciprocate along the guide shaft; the magnet rod supported on both ends inside the hollow part of the guide shaft; a forcer that is disposed around the magnet rod to constitute a linear motor together with the magnet rod and is coupled with the slide member; a pair of end caps that are so fixed as to close the openings on both ends of the guide shaft and support the shaft ends of the magnet rod; support members provided in the end caps to support the magnet rod from a direction orthogonal to the axis direction; and a rod pressing member that is screwed to the end cap from the side opposite to the support member at a position away from the support member in the axis direction of the magnet rod and presses the magnet rod. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a linear actuator unit having a built-in driving means and capable of moving a guide shaft and a slide member relatively in accordance with an input signal, and in particular, a linear type using a rod-type linear motor as a propelling means for the slide member. The present invention relates to an actuator unit.

  A so-called rod-type linear motor is known as a kind of linear motor used as a propulsion means in an actuator. This rod type linear motor includes a rod-shaped magnet rod in which a plurality of magnetic poles are arranged along the longitudinal direction, and a through-hole through which the magnet rod is inserted, and a coil member is arranged on the inner peripheral surface of the through-hole. When a drive current is passed through the coil member, a propulsive force along the axial direction of the magnet rod is generated with respect to the forcer.

  As a linear actuator unit using this rod type linear motor, one disclosed in WO2007 / 026673A1 is known. The linear actuator unit is formed in a cylindrical shape having a hollow portion and an opening is formed along the longitudinal direction, and the guide shaft is assembled to the guide shaft via a large number of balls. A slide member that guides the shaft in the axial direction; a magnet rod supported at both ends in the hollow portion of the guide shaft; and a linear motor that is disposed in the hollow portion of the guide shaft and combined with the magnet rod, And a forcer coupled to the slide member through an opening.

  When a driving current is applied to the coil member of the forcer, the forcer is propelled in the axial direction in the hollow portion of the guide shaft along the magnet rod. As a result, the slide member coupled to the forcer through the opening of the guide shaft is propelled in the axial direction outside the guide shaft, and the slide member is moved to an arbitrary amount with respect to the guide shaft in response to energization of the drive current. It is possible to move with.

  The conventional linear actuator unit configured as described above has a linear motor as a thrust generation source, a guide shaft as a linear guide means, and a slide member as a result of storing a rod-type linear motor in the hollow portion of the guide shaft. It is fused in a compact manner, making it very easy to handle.

WO2007 / 026673A1

  However, in such a conventional linear actuator unit, since the guide shaft is made of a magnetic material such as steel, the magnet rod and the hollow portion are arranged as a result of arranging the magnet rod in the hollow portion of the guide shaft. The magnetic attraction force acts between the guide wall and the inner wall of the guide shaft, and the magnet rod is disposed in the hollow portion of the guide shaft while supporting both ends in the longitudinal direction. Is unevenly distributed around the magnet rod, there is a problem that the magnet rod is likely to be bent.

  In particular, an opening is formed in the guide shaft to connect the forcer to the slide member, and no magnetic attractive force acts between the magnet rod and the opening, so it is arranged in the hollow portion of the guide shaft. The magnet rod thus made tends to bend on the side opposite to the opening, and there is concern about contact of the magnet rod with the guide shaft when the entire length of the magnet rod is increased.

  When such bending occurs in the magnet rod, the movement of the forcer arranged so as to surround it is hindered. When the bending amount of the magnet rod is large, the forcer and the magnet rod come into contact with each other, and the slide In addition to the inability to move the member, there is a concern that the positioning accuracy of the slide member may be lowered even when contact between the forcer and the magnet rod is avoided.

  The present invention has been made in view of such problems, and the object of the present invention is to suppress the bending of the magnet rod as much as possible while miniaturizing using a rod type linear motor, An object of the present invention is to provide a linear actuator unit capable of obtaining smooth movement of a slide member and high positioning accuracy.

  In order to achieve the above object, a linear actuator unit according to the present invention includes a guide shaft made of a magnetic body having a hollow portion and formed in a cylindrical shape and having an opening portion formed along an axial direction. A slide member that can freely reciprocate along an axis, a magnet rod that is supported at both ends in the hollow portion of the guide shaft, and a magnet rod that is disposed around the magnet rod in the hollow portion of the guide shaft and coupled with the magnet rod While constituting a linear motor, the forcer coupled with the slide member through the opening of the guide shaft, and fixed to both ends of the guide shaft in the axial direction so as to close the openings at both ends of the guide shaft A pair of end caps that support both ends of the magnet rod in the axial direction, and provided on the end caps, the magnet rod is orthogonal to the axial direction. A rod pressing member that is screwed into the end cap and presses the magnet rod from the opposite side of the supporting member and at a position away from the supporting member with respect to the axial direction of the magnet rod. Member.

  According to the present invention configured as described above, the following effects are obtained. In the present invention, the magnet rod is supported at both ends in the hollow portion of the guide shaft, and its periphery is surrounded by the guide shaft except for the opening. For this reason, although a magnetic attractive force acts between the magnet rod and the guide shaft, no magnetic attractive force acts between the opening and the magnet rod. It tends to bend in the direction.

  However, since the rod pressing member is screwed to the end caps fixed to both ends of the guide shaft in the axial direction, the magnet rod is pressed from the direction orthogonal to the axial direction by fastening the rod pressing member. It becomes possible. Thereby, the bending of the magnet rod is reduced, and as a result, smooth movement of the slide member can be ensured and the positioning accuracy of the slide member with respect to the guide shaft can be increased.

It is a whole perspective view which shows the linear actuator unit of this invention. It is a side view of the linear actuator unit shown in FIG. FIG. 2 is a perspective view in which the microactuator shown in FIG. 1 is cut out perpendicular to the longitudinal direction at the center of the slide member. It is a perspective view which shows the forcer which comprises a linear motor. It is a side view which shows the state which mounted | wore the protector plate to the forcer shown in FIG. It is the perspective view which notched the end cap of the linear actuator unit shown in FIG. 1 in parallel with the longitudinal direction.

  Hereinafter, the linear actuator unit of the present invention will be described in detail with reference to the accompanying drawings.

  1 to 3 are views showing an example of a linear actuator unit to which the present invention is applied. FIG. 1 is an overall perspective view, FIG. 2 is a side view, and FIG. 3 is perpendicular to the longitudinal direction at the center of a slide member to be described later. It is a cutaway perspective view. The linear actuator unit includes a stainless steel guide shaft 1 having a hollow portion 10 and formed in a substantially cylindrical shape, and a slide member 2 fitted to the outside of the guide shaft 1 through a large number of balls. And the slide member 2 can be reciprocated in the axial direction of the guide shaft 1 using a thrust generated by the linear motor 3 accommodated in the hollow portion 10 of the guide shaft 1. Yes.

  The guide shaft 1 is formed of a magnetic material and has a hollow portion 10 and is formed in a cylindrical shape, and two ball rolling grooves 11 are formed on the outer peripheral surface thereof with a phase shift of 180 °. Yes. Further, the guide shaft 1 is provided with a single opening 12 along the axial direction at a position that is 90 ° out of phase with the ball rolling groove 11. The opening 12 is located below the guide shaft 1 in FIGS. Accordingly, the hollow portion 10 of the guide shaft 1 described above is opened to the outside of the guide shaft 1 through the opening 12. Further, a flat surface 13 is formed on the outer peripheral surface of the guide shaft 1 at a position that is 180 degrees out of phase with the opening 12, and this flat surface 13 is a mounting surface for a linear scale described later.

  On the other hand, the slide member 2 is formed in a substantially rectangular shape and has a through hole having an inner diameter slightly larger than that of the guide shaft 1. The guide shaft 1 is inserted into the through hole, and is assembled to the slide member 2 via a large number of balls rolling on the ball rolling groove 11. The slide member 2 includes a slide block 20 and a plurality of end plates 21 fixed to both end surfaces in the axial direction of the slide block 20 corresponding to the ball rolling grooves 11. The slide block 20 is formed with a mounting surface 20a for a fixed portion or a movable portion of a device using the linear actuator unit, and a tap hole 20b into which a bolt is screwed is formed on the mounting surface 20a.

  Moreover, two load rolling grooves 22 opposite to the ball rolling grooves 11 of the guide shaft 1 are formed 180 ° out of phase on the inner peripheral surface of the through hole of the slide block 20. Rolling is performed between the ball rolling groove 11 and the load rolling groove 22 while applying a load. Further, two ball return passages 23 are formed in the slide block 20 in parallel with each load rolling groove 22, and these ball return passages 23 exist outside each load rolling groove 22. On the other hand, each end plate 21 is formed with a direction changing path for moving the ball between the load rolling groove 22 of the slide block 20 and the ball return path 23 corresponding to the load rolling groove 22. When fixed to both end surfaces of the slide block 20 in the axial direction, the slide member 2 is provided with an infinite circulation path for the balls. That is, in the slide member 2 shown in FIG. 3, two endless circulation paths are formed so as to sandwich the guide shaft 1. In FIG. 3, the load rolling groove 22 and the ball return passage 23 formed in the slide block 20 are illustrated, but the balls that roll through these are not illustrated.

  Therefore, when the slide member 2 is moved along the guide shaft 1, the ball circulates in the endless circulation path while applying a load between the slide block 20 and the guide shaft 1, and the slide member 2 is moved along the guide shaft. 1 can be continuously moved. Further, since the ball rolls between the ball rolling groove 11 of the guide shaft 1 and the load rolling groove 22 of the slide member 2, the slide member 2 is prevented from rotating in the circumferential direction of the guide shaft 1. Thus, torque can be transmitted between the slide member 2 and the guide shaft 1. That is, the slide member 2 and the guide shaft 1 constitute a ball spline device, the guide shaft 1 corresponds to a spline shaft, and the slide member 2 corresponds to a spline nut.

  In the example shown in FIGS. 1 to 3, the slide member 2 is assembled outside the guide shaft 1. However, the ball rolling groove 11 is provided on the inner wall of the guide shaft 1, that is, the inner wall of the guide shaft 1 facing the hollow portion 10. A configuration in which the slide member 2 is assembled in the hollow portion 10 via a large number of balls may be employed.

  Therefore, this linear actuator unit is used so that the slide member 2 is fixed to other devices by utilizing the tap hole 20b, and the guide shaft 1 supported by the slide member 2 is advanced and retracted in the axial direction. Is done.

  On the other hand, a magnet rod 30 as a stator of the linear motor 3 is accommodated in the hollow portion 10 of the guide shaft 1. Such a magnet rod 30 is formed by alternately arranging N poles and S poles of permanent magnets along the axial direction, and may be manufactured by packing a large number of permanent magnets inside a steel pipe, or a molded round shape. The pole may be magnetized later to form a magnetic pole. The magnet rod 30 shown in FIG. 3 is manufactured in the former example.

  A pair of end caps 5 are fitted to both ends of the guide shaft 1 in the axial direction. Inside these end caps 5, rod insertion portions into which the end portions of the magnet rod 30 are inserted are formed. Accordingly, the magnet rod 30 is supported in the hollow portion 10 of the guide shaft 1 by fixing the pair of end caps 5 to the guide shaft 1.

  FIG. 4 shows details of the forcer 31 constituting the linear motor 3. The forcer 31 is arranged around the magnet rod 30, and a plurality of coil members 32 wound around the magnet rod 30 in a ring shape while maintaining a slight gap, and these coil members 32 are integrated. A resin holder 33 serving as an insulator to be held in the housing and a stainless steel plate member 34 bonded to the resin holder 33. The plate member 34 is formed of a magnetic material. In addition, the code | symbol 35 in FIG. 4 is a cable for supplying a drive current to each coil member 32, and is formed from the flexible printed circuit board (FPC).

  A three-phase alternating current is applied to each coil member 32, and the coil members 32 corresponding to the U-phase, V-phase, and W-phase of the three-phase alternating current are arranged in order on the resin holder 33. Has been. In the example shown in FIG. 4, 18 coil members 32 are arranged in the resin holder 33, and six sets of three coil members 32 corresponding to the U phase, the V phase, and the W phase are arranged. Become. The arrangement pitch of the coil members 32 is set shorter than the arrangement pitch of the permanent magnets in the magnet rod 30. Magnetic flux is formed in the magnet rod 30 from the magnetic pole of S pole to the magnetic pole of N pole, and the forcer 31 incorporates a magnetic pole sensor (not shown) for detecting the magnetic flux density. Therefore, the positional relationship of each magnetic pole (N pole and S pole) of the magnet rod 30 with respect to the coil member 32 is grasped from the detection signal output from the magnetic pole sensor. The driver unit that controls the energization of the drive current to the coil member 32 receives the detection signal of the magnetic pole sensor, and calculates the phase of the optimum drive current according to the positional relationship between the coil member 32 and each magnetic pole of the magnet rod 30. Then, it energizes each coil member 32. As a result, due to the interaction between the drive current flowing through each coil member 32 and the magnetic flux formed by the permanent magnet, an attractive force and a repulsive force are generated between the coil member 32 and each magnetic pole of the permanent magnet. It is propelled in the axial direction of the magnet rod 30.

  Two linear scales 14 and 15 are attached to the flat surface 13 provided on the opposite side of the guide shaft 1 from the opening 12 along the longitudinal direction of the guide shaft 1. The slide member 2 is mounted with a read head 16 facing the linear scales 14 and 15 so that when the slide member 2 moves relative to the guide shaft 1, a signal corresponding to the amount of movement is output. It is configured. The output signal of the read head 16 is transmitted to the driver unit by a cable 17. The cable 17 is formed from a flexible printed circuit board (FPC). Of the pair of linear scales 14 and 15, one linear scale 14 is for detecting the position of the slide member 2 on the guide shaft 1, and the other linear scale 15 is the home position of the slide member 2 on the guide shaft 1. This is for returning to origin.

  As shown in the sectional view of FIG. 3, the coil member 32 of the forcer 31 surrounds the magnet rod 30 in the hollow portion of the guide shaft 1, but the resin holder 33 that holds the coil member 32 is a guide shaft. A plate member 34 that protrudes to the outside of the guide shaft 1 through one opening 12 and is bonded to the resin holder 33 is coupled to the slide member 2 by a fixing screw. Therefore, the plate member 34 is formed with a tap hole 36 into which the fixing screw is screwed. Thereby, when the forcer 31 is propelled in the axial direction of the magnet rod 30, the slide member 2 is propelled in the axial direction of the guide shaft 1.

  The axial length of the forcer 31, that is, the length of the forcer 31 along the arrangement direction of the coil members 32 is formed longer than the axial length of the slide member 2. This is to increase the thrust of the linear motor 3. For this reason, the slide member 2 is fixed to the center portion in the longitudinal direction of the forcer 31, and both ends in the longitudinal direction of the forcer 31 are exposed to the outside of the guide shaft 1 from the opening 12 without being covered by the slide member 2. Yes.

  On the other hand, if the slide member 2 exceeds the limit stop position and overruns on the guide shaft 1 as a result of increasing the length of the forcer 31 and improving the thrust of the linear motor 3 in this way, It is assumed that the end of the forcer 31 hits the end cap 5 and the forcer 31 is damaged.

  Even when such a situation occurs, in order to prevent the forcer 31 from being damaged, the linear actuator unit is provided with a pair of protector plates 4 for protecting the forcer 31. FIG. 5 is a side view showing the forcer 31 with the protector plate 4 attached thereto. The protector plate 4 is a stainless steel plate having a distal end portion 40 bent in a substantially L shape, and is attached to the plate member 34 of the forcer 31 so as to sandwich the slide member 2 from the axial direction. In a state where the protector plate is attached, a gap is formed between the front end portion 40 of the protector plate 4 and the axial end surface of the forcer 31, while the rear end portion 41 of the protector plate is in contact with the slide member 2. Yes. Further, the attachment of the protector plate 4 to the plate member 34 of the forcer 31 is accompanied by some play, so that the external force acting on the protector plate 4 does not reach the plate member 34 and thus the forcer 31.

  FIG. 6 shows the end cap 5 fitted to both ends of the guide shaft 1 in the axial direction. Inside the end cap 5 are formed a rod insertion part 51 into which the end of the magnet rod 30 is inserted and a shaft insertion part 52 into which the end of the guide shaft 1 is inserted. A step portion 53 is formed between the rod insertion portion 51 and the shaft insertion portion 52, and the end portion of the guide shaft 1 is locked by the step portion 53. That is, the end of the magnet rod 30 is supported by the end cap 5 in a state of protruding from the guide shaft 1.

  When the end of the magnet rod 30 is attached to the rod insertion portion 51, a slight gap is formed between the circumferential surface of the magnet rod 30 and the rod insertion portion 51. That is, the attachment of the end portion of the magnet rod 30 to the rod insertion portion 51 involves some play. Further, the shaft insertion portion 52 is configured to close the hollow portion 10 of the guide shaft 1.

  On the other hand, the end cap 5 includes a rod support pin 54 as a support member for supporting the magnet rod 30 and a rod press pin 6 as a rod pressing member for pressing the end of the magnet rod 30. The magnet rod 30 is screwed from the direction orthogonal to the axial direction.

  A first tap hole 56 into which the rod support pin 54 is screwed is formed on a first surface 55 that forms the surface of the end cap 5. The first tap hole 56 penetrates from the first surface 55 toward the shaft insertion portion 52. On the other hand, the guide shaft 1 is formed with a through hole communicating with the first tap hole 56.

  Accordingly, when the rod support pin 54 is screwed into the first tap hole 56 with the end cap 5 fitted to both ends of the guide shaft 1 in the axial direction, the rod support pin 54 is connected to the end cap 5 and the guide. The shaft 1 passes through and comes into contact with the magnet rod 30. In this state, the rod support pin 54 restricts the movement of the magnet rod 30 toward the flat surface 13 side of the guide shaft 1. Further, since the rod support pin 54 penetrates the guide shaft 1, the rod support pin 54 also functions as a stopper for preventing the guide shaft 1 from coming off from the end cap 5.

  A second tap hole 58 into which the rod pressing pin 6 is screwed is formed on the second surface 57 located on the opposite side of the first surface 55 of the end cap 5. The second tap hole 58 is provided closer to the shaft end of the magnet rod 30 than the first tap hole 56, and penetrates toward the rod insertion portion 51. That is, in a state where the rod pressing pin 6 is screwed into the second tap hole 58, the rod pressing pin 6 is brought into contact with the magnet rod 30.

  In the linear actuator unit having the above configuration, the magnet rod 30 constituting the linear motor 3 is accommodated in the hollow portion 10 of the guide shaft 1 made of a magnetic material, and the magnet rod 30 is supported only at both ends. Since it is located in the hollow portion 10 in a state, a magnetic attractive force acts between the magnet rod 30 and the guide shaft 1. However, an opening 12 is formed in the guide shaft 1 along the longitudinal direction, and no magnetic attractive force acts between the opening 12 and the magnet rod 30. It does not exist evenly in the circumferential direction, but is unevenly distributed. For this reason, in the linear actuator unit having the structure shown in FIGS. 1 to 4, the magnet rod 30 tends to bend toward the side opposite to the opening 12 of the guide shaft 1.

  However, in this linear actuator unit, the rod support pin 54 and the rod pressing pin 6 are screwed to the end cap 5, and the rod support pin 54 faces the flat surface 13 side of the guide shaft 1. 30 movements are restricted. On the other hand, when the rod pressing pin 6 is fastened from the state in which the rod pressing pin 6 is in contact with the magnet rod 30, there is a little play for attaching the end of the magnet rod 30 to the rod insertion portion 51. Therefore, the magnet rod 30 can be pressed.

  At this time, since the rod pressing pin 6 is screwed into the end cap 5 from the opening 12 side of the guide shaft 1, the contact surface between the rod support pin 54 and the magnet rod 30 forms a fulcrum. The pressing force of the rod pressing pin 61 acts on the magnet rod 30 as a force that resists the bending of the magnet rod 30. The bending force of the magnet rod 30 is reduced by the pressing force of the rod pressing pin 6.

  Thereby, in the linear actuator of the present invention, it is possible to smooth the movement of the slide member 2 with respect to the guide shaft 1 and to increase the positioning accuracy of the slide member 2 with respect to the longitudinal direction of the guide shaft 1. Become.

  In the above embodiment, the rod support pin 54 is screwed into the end cap 5 as a support member, that is, the end cap and the support member are provided separately, but the magnet rod 30 and the guide are provided. As long as it forms a fulcrum with the shaft 1, a thin metal plate such as a shim may be used as the support member, and the support member may be fixed to the end cap. However, as in the above embodiment, using a pin member screwed to the end cap as the support member makes it easier to adjust the deflection of the magnet rod by an amount that can arbitrarily adjust the protruding amount of the support member as a fulcrum. It becomes possible to do.

  In the above embodiment, the rod pressing pin 6 as a rod pressing member is configured to be screwed closer to the shaft end of the magnet rod 30 than the fulcrum formed by the rod support pin 54. 6 may be screwed into the longitudinal center of the magnet rod 30 rather than the fulcrum. That is, a rod pressing pin 6 as a rod pressing member is screwed into the first tap hole 56 of the end cap 5, while a rod supporting pin 54 as a support member is screwed into the second tap hole 58. There is no problem.

  Furthermore, since the bending of the magnet rod 30 changes according to the length of the magnet rod 30, it is necessary to change the correction amount of the magnet rod by the rod pressing member accordingly. Therefore, the clearance between the peripheral surface of the magnet rod 30 and the rod insertion portion 51 of the end cap 5 may be adjusted according to the length of the magnet rod 30. For example, when the magnet rod 30 is elongated, the clearance between the circumferential surface of the magnet rod 30 and the rod insertion portion 51 is set large, and the correction amount of the magnet rod by the rod pressing member is set large. preferable.

  DESCRIPTION OF SYMBOLS 1 ... Guide shaft, 2 ... Slide member, 3 ... Linear motor, 5 ... End cap, 6 ... Rod press pin (rod press member), 12 ... Opening part, 30 ... Magnet rod, 31 ... Forcer, 54 ... Rod support pin (Support member)

Claims (2)

  A guide shaft made of a magnetic body having a hollow portion and formed in a cylindrical shape and having an opening formed in the axial direction, a slide member capable of freely reciprocating along the guide shaft, and the guide A magnet rod supported at both ends in the hollow portion of the shaft, and arranged around the magnet rod in the hollow portion of the guide shaft to form a linear motor together with the magnet rod, and through the opening of the guide shaft A forcer combined with the slide member, a pair of end caps fixed to both ends of the guide shaft in the axial direction so as to close openings at both ends of the guide shaft, and supporting both ends of the magnet rod in the axial direction; A support member provided on the end cap and supporting the magnet rod from a direction orthogonal to the axial direction; and from the opposite side of the support member and in front Linear actuator unit and having a rod pressing member for pressing the magnet rod with respect to the axial direction of the magnet rod screwed into the end cap at a location remote from said support member.   The guide shaft is a spline shaft having ball rolling grooves along the axial direction on the outer peripheral surface, while the slide member is a spline nut provided so as to surround the spline shaft via a plurality of balls. The linear actuator unit according to claim 1.

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