JP2009273224A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear actuator, wherein it is possible to stabilize the output of a moving member and enhance the state of coaxiality of the moving member, without causing increase in the number of parts. <P>SOLUTION: The linear actuator includes: a case 10 having a cylindrical wall 10a and a bottom wall 10b closing the cylindrical wall 10a and integrally having a guide shaft 10c protruded from the bottom wall 10b along the center axis line O; the moving member 20 provided with an axial member 31, having a cylindrical portion 31a into which the guide shaft 10c is inserted so that it can be relatively moved along the center axis line O and a bottom portion 31b for closing the cylindrical portion 31a; a coil spring 33, that is placed between the bottom portion 31b and the tip of the guide shaft 10c opposed to the bottom portion 31b and bonded to the tip and the bottom portion 31b and produces a bias force along the center axial line O; and coils 16, 18 that are provided on a stator 11 and vibrate the moving member 20 along the center axis line O by a magnetic field produced at energization. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a linear actuator.

Conventionally, as a linear actuator used as an active vibration-proof actuator or the like, for example, one described in Patent Document 1 is known. The linear actuator includes a mass member (M) having a predetermined mass with respect to a vibration suppression target, and an excitation mechanism that vibrates the mass member and is connected to the mass member via an elastic body (26). The excitation mechanism includes a convex member (28) that supports the mass member and is divided from the mass member, and a drive member that drives the convex member by increasing / decreasing electromagnetic force to vibrate the mass member. With.
JP 2006-258235 A

  By the way, in patent document 1, since the elastic body which concerns on the vibration of a mass member and a plunger (22) is arrange | positioned above an upper yoke (15), especially in the radial direction (lateral direction) at the time of the maximum stroke. The output is likely to be affected by external force, and the output may become unstable due to the eccentricity of the plunger or the like. Or the number of parts for ensuring the accuracy of coaxiality, such as a plunger, is increasing. Further, since the mass member connected to the elastic body is further arranged on the upper side, the entire apparatus is forced to be enlarged, and the mountability is impaired.

  The objective of this invention is providing the linear actuator which can stabilize the output of a needle | mover and can improve the coaxial property of a needle | mover, without increasing a number of parts.

  In order to solve the above-mentioned problems, the invention described in claim 1 has a cylindrical wall and a bottom wall that closes the cylindrical wall, and is protruded from the bottom wall along the central axis of the cylindrical wall. A case integrally including a guide shaft; a movable part including a shaft portion having a cylindrical portion in which the guide shaft is inserted so as to be relatively movable along the central axis; and a bottom portion closing the cylindrical portion; and the bottom portion A biasing member that is interposed between tips of the guide shafts facing the bottom portion and is fixed to the tip and bottom portions, respectively, and generates a biasing force along the central axis, and any of the case and the mover A gist is provided with a coil that is provided on either side and vibrates the movable element along the central axis by a magnetic field generated during energization.

  According to this configuration, the highly rigid guide shaft integrated with the case is inserted into the cylindrical portion of the shaft member so as to be relatively movable along the central axis. The shaft member (cylinder portion) is supported by being overlapped with the guide shaft in a direction along the central axis, and particularly in the radial direction (horizontal direction) even during the maximum stroke of the mover (shaft member). Direction) and the output of the mover can be further stabilized. Moreover, the number of parts for ensuring the accuracy of the coaxiality of the movable element (shaft member) with respect to the guide shaft can be reduced. Further, since the movable element (shaft member) can be basically accommodated in the cylindrical wall, the entire apparatus can be further downsized. Furthermore, since the accuracy of coaxiality of the movable element (shaft member) can be ensured by inserting the guide shaft into the cylindrical portion, the assembling property can be improved. Further, since the movable element can be supported (floating supported) on the guide shaft by only one urging member, the number of parts can be further reduced.

The gist of the invention according to claim 2 is that, in the linear actuator according to claim 1, a bush that is slidably contacted with the guide shaft is fixed to the cylindrical portion.
According to the same configuration, the shaft member is further improved in adhesion with the guide shaft via the bush fixed to the cylindrical portion, thereby further stabilizing the output of the movable element (shaft member), The coaxiality of the mover (shaft member) with respect to the guide shaft can be further improved.

  According to a third aspect of the present invention, in the linear actuator according to the second aspect, the bush is always in sliding contact with the guide shaft over the entire length in the direction along the central axis when the mover vibrates. The gist.

  According to this configuration, even when the mover vibrates, the bush is always in sliding contact with the guide shaft over the entire length in the direction along the central axis, so that the contact area with the guide shaft remains unchanged. Thus, the output of the mover can be further stabilized.

  According to a fourth aspect of the present invention, in the linear actuator according to the second or third aspect, the bush has a friction coefficient that is smaller in a sliding contact surface with the guide shaft than a fixed surface with the cylindrical portion. The gist is that it is formed of two different materials.

  According to this configuration, the bush can reduce the energy loss at the time of vibration of the mover by forming the sliding contact surface with the guide shaft from a material having a small friction coefficient. By fixing the fixed surface to the portion with a material having a large friction coefficient, the tube portion can be firmly fixed.

  According to the present invention, it is possible to provide a linear actuator that can stabilize the output of the mover and improve the coaxiality of the mover without increasing the number of parts.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a linear actuator according to this embodiment. As shown in the figure, a case 10 constituting a housing of the linear actuator has a substantially cylindrical cylindrical wall 10a and a bottom wall 10b that closes an opening on the upper side of the cylindrical wall 10a. A substantially cylindrical guide shaft 10c is provided integrally with the bottom wall 10b along the central axis O of 10a. And the front-end | tip of the guide shaft 10c is recessedly provided circularly along the said central axis O, and forms the seat surface 10d. The length in the direction along the central axis O of the guide shaft 10c is set shorter than the length in the direction along the central axis O of the cylindrical wall 10a. Moreover, the case 10 is expanded through the step part 10e in the vicinity of the bottom wall 10b.

  The stator 11 of the linear actuator includes three annular teeth 12, 13, and 14 arranged in order on the step portion 10 e along the central axis O. These teeth 12 to 14 are formed of a magnetic metal (iron, magnetic stainless steel, etc.). The stator 11 is fixed to the case 10 by being sandwiched between the stator 10 and an end cap (not shown) that closes the lower opening of the cylindrical wall 10a.

  The teeth 12 that are arranged adjacent to the stepped portion 10e and form end magnetic poles have boss-like projecting pieces 12a that project from the inner peripheral portion thereof toward the teeth 13 and extend from the outer peripheral portion toward the teeth 13 to extend toward the teeth 13. 13 is provided. Further, the tooth 13 that is disposed adjacent to the tooth 12 and forms the central magnetic pole has a pair of boss-like projecting pieces 13a and 13b that project from the inner peripheral portion thereof toward the teeth 12 and 14, respectively. Further, the tooth 14 arranged on the opening end side has a boss-like projecting piece 14a projecting from the inner peripheral portion thereof toward the tooth 13 side, and extends from the outer peripheral portion toward the tooth 13 side so as to come into contact with the tooth 13. It has a back yoke 14b.

  An annular bobbin 15 made of a resin material is mounted between the adjacent teeth 12 and 13 in a manner that fits into an annular recess formed between the teeth 12 and 13. A coil 16 is wound in a winding direction toward one side. Similarly, between the adjacent teeth 13 and 14, an annular bobbin 17 made of a resin material is mounted in a manner of fitting into an annular recess formed between the teeth 13 and 14, and the bobbin 17 The coil 18 is wound in the winding direction toward the other side reversed with respect to the coil 16. The two coils 16 and 18 arranged in parallel along the central axis O are connected in series, and form a magnetic field in a direction opposite to each other when energized.

  The mover 20 of the linear actuator includes a shaft member 31 made of a nonmagnetic material. The shaft member 31 includes a cylindrical portion 31a into which the guide shaft 10c is inserted so as to be relatively movable along the central axis O, and the shaft member 31a. It has the bottom part 31b which obstruct | occludes the illustration lower opening of the cylinder part 31a. A cylindrical bush 32 that is in sliding contact with the guide shaft 10c is fixed to the cylindrical portion 31a by press-fitting. The bush 32 is formed of two different materials so that the sliding contact surface with the guide shaft 10c has a smaller friction coefficient than the fixed surface with the cylindrical portion 31a. Specifically, the guide shaft 10c side is molded from a resin made of a low friction material, and the cylinder part 31a side is molded from a metal.

  The shaft member 31 is reduced in diameter near the bottom 31b to form a seating surface 31c. Between the bottom 31b and the tip of the guide shaft 10c facing the bottom 31b, a coil spring as an urging member in which one end and the other end are fixed to the seat surfaces 10d and 31c, respectively. 33 is interposed. The coil spring 33 generates a biasing force along the central axis O.

  A pair of annular yokes 21 and 22 made of magnetic metal disposed on the bottom wall 10b side and the opening side of the case 10 are joined to the outer peripheral surface of the shaft member 31, and these are arranged in the direction of the central axis O. An annular permanent magnet 23 sandwiched between both yokes 21 and 22 is joined. The yokes 21 and 22 have the same outer diameter that is smaller than the inner diameters of the teeth 12 to 14. The permanent magnet 23 is made of, for example, a ferrite magnet that is magnetized in the direction of the central axis O, and has an outer diameter slightly smaller than the outer diameter of the yokes 21 and 22. The length LM along the central axis O of the permanent magnet 23 is set to be equal to or shorter than the length LT along the central axis O of the teeth 13 forming the central magnetic pole. Further, the annular protrusions of the yokes 21 and 22 that slightly protrude radially outward with respect to the tip of the permanent magnet 23 form the magnetic poles of the mover 20.

  The movable element 20 floatingly supported on the guide shaft 10c via the coil spring 33 in a manner guided by the guide shaft 10c can reciprocate along the central axis O (guide shaft 10c). Yes. The coil spring 33 returns the movable element 20 to the reference position of the movable range by the urging force and secures a gap C with the stator 11.

  Here, when the mover 20 is at the reference position of the movable range, the yoke 21 is disposed so that the center position of the outer peripheral surface thereof is opposed to the center position between the projecting pieces 12a and 13a in the radial direction. The yoke 22 is arranged at the central position between the projecting pieces 13b and 14a so that the central position of the outer peripheral surface is opposed in the radial direction, and the permanent magnet 23 is positioned at the central position of the inner peripheral surface of the tooth 13. It arrange | positions so that the center position of an outer peripheral surface may oppose radial direction. With this arrangement relationship, when the coils 16 and 18 are not energized, the magnetic flux generated by the permanent magnet 23 is between the pair of yokes 21 and 22 and the teeth 13 that form the central magnetic pole of the stator 11. This constitutes a magnetic circuit in a closed loop. Therefore, in this state, a force that holds the mover 20 at the reference position of the movable range is applied.

  The coils 16 and 18 are energized by switching the energization direction between forward and reverse. At the time of energization, the mover 20 is caused by magnetic fields in opposite directions formed according to the energization direction. When the permanent magnet 23 is vibrated, it reciprocates along the central axis O with the central position (reference position) of the movable range as the origin (vibration center). In the present embodiment, the bush 32 is set so as to always slidably contact the guide shaft 10c over the entire length in the direction along the central axis O when the mover 20 vibrates.

As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) In the present embodiment, a highly rigid guide shaft 10 c integrated with the case 10 is inserted into the cylindrical portion 31 a of the shaft member 31 along the central axis O so as to be relatively movable. The shaft member 31 (cylindrical portion 31a) is supported by being overlapped with the guide shaft 10c in the direction along the central axis O, so that the radial direction is obtained even when the movable member 20 (the shaft member 31) is at the maximum stroke. It can be made less susceptible to external forces in the (lateral direction), and the output of the mover 20 can be further stabilized. Further, it is possible to reduce the cost by reducing the number of parts for ensuring the accuracy of the coaxiality of the mover 20 (shaft member 31) with respect to the guide shaft 10c. Furthermore, since the needle | mover 20 (shaft member 31) can be basically accommodated in the cylinder wall 10a, it can further reduce in size as the whole apparatus. Furthermore, since the accuracy of the coaxiality of the mover 20 (shaft member 31) can be ensured by inserting the guide shaft 10c into the cylindrical portion 31a, the assembling property can be improved and the cost can be reduced. Further, since the movable element 20 can be supported (floating supported) on the guide shaft 10c by only one coil spring 33, the number of parts can be further reduced and the cost can be reduced.

  (2) In the present embodiment, the bushing 32 slidably contacting the guide shaft 10c is fixed to the cylindrical portion 31a, so that the shaft member 31 has improved adhesion to the guide shaft 10c via the bush 32. Thus, the output of the mover 20 (shaft member 31) can be further stabilized, and the coaxiality of the mover 20 (shaft member 31) with respect to the guide shaft 10c can be further improved.

  (3) In this embodiment, the bush 32 is always in sliding contact with the guide shaft 10c over the entire length in the direction along the central axis O when the mover 20 vibrates, so that the contact area with the guide shaft 10c remains unchanged. Thus, the output of the mover 20 can be further stabilized.

  (4) In this embodiment, the bush 32 can reduce the energy loss at the time of vibration of the needle | mover 20 by shape | molding the sliding contact surface with the guide shaft 10c with a material with a small friction coefficient, Since the surface to be fixed to the cylindrical portion 31a is formed of a material having a large friction coefficient, the cylindrical portion 31a can be firmly fixed.

(5) In the present embodiment, the mover 20 can be easily removed by removing the cylindrical portion 31a from the guide shaft 10c, so that maintainability can be improved.
In addition, you may change the said embodiment as follows.

  In the embodiment, the bush 32 may be omitted if the coaxiality of the guide shaft 10c and the shaft member 31 (the case 10, the stator 11, and the mover 20) is suitably ensured.

  In the embodiment, the configuration of the magnetic circuit that vibrates the mover 20 is an example. For example, a linear actuator (voice coil motor) including a coil on the mover side may be used.

In the above embodiment, instead of the coil spring 33, for example, an elastic body made of a rubber material may be adopted.
In the embodiment, the reference position of the movable range of the mover 20 may be an appropriate intermediate position of the movable range.

In the embodiment, the permanent magnet 23 may be a neodymium magnet or the like.
Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
A case having a cylindrical wall and a bottom wall that closes the cylindrical wall, a stator that is accommodated in the case and includes three teeth that form two coils and a magnetic pole along the central axis, and the central axis A mover in which a permanent magnet is sandwiched between a pair of yokes in the direction of, and an urging member for returning the mover to a reference position in a movable range when the coil is not energized and securing a gap with the stator. In a linear actuator that vibrates the mover along the central axis by a magnetic field generated when energizing the coil,
A guide shaft integrally projecting from the bottom wall along the central axis of the cylindrical wall;
A cylindrical portion that is provided in the movable element and into which the guide shaft is inserted so as to be relatively movable along the central axis; and a bottom portion that closes the cylindrical portion; and the pair of yokes on the outer peripheral surface of the cylindrical portion; A shaft member to which the permanent magnet is joined,
The linear actuator, wherein the urging member is interposed between the bottom and the tip of the guide shaft facing the bottom, and is fixed to the tip and the bottom, respectively.

The longitudinal cross-sectional view which shows one Embodiment of this invention.

Explanation of symbols

  O ... center axis, 10 ... case, 10a ... cylinder wall, 10b ... bottom wall, 10c ... guide shaft, 11 ... stator, 16, 18 ... coil, 20 ... mover, 31 ... shaft member, 31a ... cylinder part, 31b ... bottom, 32 ... bush, 33 ... coil spring (biasing member).

Claims (4)

A case that has a cylindrical wall and a bottom wall that closes the cylindrical wall, and that integrally has a guide shaft that projects from the bottom wall along a central axis of the cylindrical wall;
A mover comprising a cylindrical member into which the guide shaft is inserted so as to be relatively movable along the central axis, and a shaft member having a bottom that closes the cylindrical portion;
A biasing member that is interposed between the bottom and the tip of the guide shaft facing the bottom and is fixed to the tip and the bottom, respectively, and generates a biasing force along the central axis;
A linear actuator provided with either one of the case and the mover, and a coil that vibrates the mover along the central axis by a magnetic field generated during energization. The linear actuator according to claim 1,
The linear actuator is characterized in that a bush that slides on the guide shaft is fixed to the cylindrical portion. The linear actuator according to claim 2, wherein
The linear actuator is characterized in that the bush is always in sliding contact with the guide shaft over the entire length in the direction along the central axis when the mover vibrates. The linear actuator according to claim 2 or 3,
The linear actuator according to claim 1, wherein the bush is formed of two different materials so that a sliding contact surface with the guide shaft has a smaller coefficient of friction than a fixed surface with the cylindrical portion.

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