JP4857600B2 - Linear actuator - Google Patents

Description

  The present invention relates to a linear actuator, and more particularly to a linear actuator capable of reducing the amount of magnetic flux generated by a coil magnetomotive force being reduced by the magnetic flux of a permanent magnet in a linear actuator including a permanent magnet in a mover.

  Linear actuators are used as compressor motors and the like because they can be driven with little loss by resonating together with a spring. And since the compressor using this linear actuator can exhibit excellent performance such as high efficiency, it is expected to be used for a refrigerator, a freezer, or an air conditioner.

  As the linear actuator, there are a movable coil type (for example, a voice coil motor) in which a mover including a coil moves, a movable magnet type in which a mover including a permanent magnet moves, and the like. Among these, since the movable coil type includes a coil in the movable element, there is a possibility that the power supply line to the coil may be disconnected due to the movement of the movable element, resulting in poor reliability. For this reason, development of a linear actuator that includes a permanent magnet in the mover is underway.

  As one method of the linear actuator including the permanent magnet of the movable element, as shown in FIG. 3, a concave portion is formed in the central outer peripheral portion in the axial direction of the movable element 40, and a cylindrical permanent magnet 41 is formed in the concave portion. Some have been fitted (see FIG. 5 of Patent Document 1). In the linear actuator shown in FIG. 3, an air gap 31 that is a magnetic gap in the reciprocating direction is provided on the mover 40 side of the yoke 30, and thrust is generated by the coil magnetomotive force of the coil 32 and the permanent magnet 41. is there. The mover 40 is used as a linear motor by providing a support mechanism 33 such as a leaf spring that is supported so as to be linearly movable.

  4 is an improved example based on the conventional linear actuator of Patent Document 1 shown in FIG. 3, omitting the portion constituting the gap 31 of the yoke 30 of the linear actuator shown in FIG. The shape of the permanent magnet 41 is simplified, and the length of the permanent magnet 41 in the axial direction is extended. In FIG. 4, a coil 32a is disposed in a recess 31a formed on the inner surface of a yoke 30a of the linear actuator 1a, and a cylindrical permanent magnet 41a is fitted in the recess of the mover 40a. FIG. 4B shows a sectional shape of the yoke 30a, and FIG. 4B shows an overview of the cylindrical permanent magnet 41a. The permanent magnet 41a has an N pole on the side facing the yoke 30a and an S pole on the inner peripheral side.

  FIG. 5 is a diagram for explaining the operation of the linear actuator shown in FIG. In the linear actuator 1a, when no current is passed through the coil 32a, the mover 40a is stopped, and the permanent magnet 41a, the yoke 30a, the mover 40a, and the permanent magnet 41a are stopped as shown in FIG. A magnetic flux loop that is connected in order is formed throughout the yoke 30a.

Then, an alternating current (sine wave current, rectangular wave current) is passed through the coil 32a.
For example, as shown in FIG. 5B, when a current flows through the coil 32a in a clockwise direction when viewed from the right side in FIG. 5B, the coil 32a circulates in the direction of the thick line A. Magnetomotive force is generated so that a magnetic flux loop is generated. As described above, the permanent magnet 41a attempts to align the position in the axial direction with respect to the end portion (protrusion portion) 30b of the yoke 30a, so that the mover 40a moves leftward in the axial direction (leftward on FIG. 5B). )

Next, for example, as shown in FIG. 5C, when a current flows through the coil 32a in a counterclockwise direction when viewed from the right side in FIG. A magnetomotive force is generated so that a magnetic flux loop that circulates in the direction of As described above, the permanent magnet 41a attempts to align the position in the axial direction with respect to the end portion (projecting portion) 30c of the yoke 30a, so that the mover 40a moves to the right in the axial direction (rightward on FIG. 5C). ) Then, by alternating the direction of the current flow to the coil 32a by the alternating current, the above operation is repeated, and the mover 40a reciprocates with a predetermined stroke in the axial direction with respect to the yoke 30a. Become.
JP 2004-056772 A

  By the way, the linear actuator shown in FIG. 4 has an advantage that the structure is simple, but a permanent magnet is used over a wide portion of the central portion of the mover, which is generated by permanent magnetic flux and coil magnetomotive force. There are many portions in which the direction of the magnetic flux is opposite, and there is a large proportion of cancellation of the magnetic flux generated by the permanent magnet and the coil, resulting in a problem that the generation efficiency of thrust is reduced.

  The present invention has been made to solve such a problem. The purpose of the present invention is to reduce the influence of the magnetic flux generated by the coil magnetomotive force being reduced by the permanent magnet magnetic flux of the mover. In comparison, an object of the present invention is to provide a linear actuator that can increase the generation efficiency of thrust.

The present invention has been made to solve the above problems, and includes a columnar stator having a through hole in the center, and a movable element inserted into the through hole and reciprocally movable along a central axis. In the linear actuator having the above, the stator includes a coil housing space portion formed within the predetermined range in the center in the axial direction of the inner peripheral surface of the through hole and having a recess having a predetermined depth in the radial direction along the inner peripheral surface. An end portion formed along the inner circumferential surface on both end surfaces of the through hole of the stator by providing the coil housing space portion, and fitted into the coil housing space portion, and is disposed on the outer circumferential surface of the mover. A cylindrical coil wound in parallel, and each of the movers has a small-diameter portion coaxial with the central axis at each end thereof, and each end of the inner peripheral surface of the stator. axially with respect to the respective small-diameter portion so as to correspond to the Is fitted, a pair of permanent magnets forming the same diameter cylindrical shape, in a stopped state, the center of each of the axial direction substantially coincides with the outer end face of the stator, and the orthogonal direction to the axial direction Are formed so that the outer peripheral surface of each permanent magnet and the outer peripheral surface of the mover between the permanent magnets are smoothly continuous with the same outer diameter. It is characterized by that.
If it does in this way, a recessed part will be provided in the internal peripheral surface of a stator, and a coil will be accommodated. Further, a pair of cylindrical permanent magnets is provided on the outer peripheral surface of the mover so as to correspond to each of the end portions formed on the inner peripheral surface of the stator by providing the recesses. And this pair of permanent magnets, with the mover stopped, are arranged such that the center of each axial direction substantially coincides with the outer end surface of the stator, and the magnetic poles are arranged in a direction perpendicular to the axial direction. To do.
Thereby, when the coil is energized, the amount of cancellation (cancellation) of the magnetic flux generated by the coil and the magnetic flux generated by the permanent magnet is reduced. For this reason, reduction of coil magnetomotive force can be prevented and the generation efficiency of thrust can be increased.

In addition, it is desirable that the length of the permanent magnet in the axial direction and the length of the end portion of the inner peripheral surface of the stator in the axial direction substantially coincide with each other.
According to this configuration, a pair of permanent magnets having the same length as that of the end (the same length in the axial direction) is provided on the mover so as to correspond to the end of the stator (the protruding portion on the inner peripheral surface). As a result, this reduces the amount of cancellation (cancellation) of the magnetic flux generated by the coil and the magnetic flux generated by the permanent magnet when the coil is energized. For this reason, reduction of the magnetic flux generated by the coil magnetomotive force can be prevented, and the generation efficiency of thrust can be increased.
In addition, it is desirable that the axial length between the pair of permanent magnets is larger than the axial length between the ends of the inner peripheral surface of the stator .

  In the linear actuator of the present invention, a permanent magnet having a short length (length in the axial direction) is provided on the mover so as to correspond to the end of the yoke (stator). The amount of cancellation (cancellation) of the magnetic flux generated by the coil and the magnetic flux generated by the permanent magnet is reduced. For this reason, reduction of coil magnetomotive force can be prevented and the generation efficiency of thrust can be increased.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating a configuration example of a linear actuator according to an embodiment of the present invention.
As shown in FIG. 1, the linear actuator 1 of this embodiment is provided with a yoke (stator) 10 and a reciprocating motion (movable) along the axis center inside the yoke 10 (through hole portion). The movable element 20, a pair of permanent magnets 21 and 22 fixed to the outside of the movable element 20 (the surface facing the yoke 10), and the coil 12 fixed to the recess 11 on the inner surface of the yoke 10. ing. Although not shown, the movable element 20 has a support mechanism such as a leaf spring or a bearing mechanism that holds the movable element 20 as shown in FIG.

  FIG. 1B shows the cross-sectional shape of the yoke 10. The yoke 10 has a cylindrical shape as a whole, and in a predetermined range in the center in the axial direction on the inner surface side of the yoke 10, a concave portion 11 that is a storage space for storing the coil 12 extends along the inner peripheral surface. Is formed. The yoke 10 is formed by sintering with a sintered material, for example, a magnetic material. The yoke 10 may be formed of a laminated electric iron plate. A coil 12 wound in a cylindrical shape is disposed in the recess (coil housing space) 11 of the yoke 10.

The mover 20 has a cylindrical shape as a whole, and its outer diameter is a predetermined amount smaller than the inner diameter of the yoke 10. The mover 20 is made of an iron member that is a magnetic material that is not entirely magnetized, and is made of, for example, a sintered material. The mover 20 is inserted on the inner diameter side of the yoke 10 so as to be coaxial, so that the mover 20 can be reciprocated in the axial direction of the yoke 10 with respect to the yoke 10. The mover 20 may be formed of a laminated electric iron plate.
Further, each of the both end portions in the axial direction of the movable member 20, the small diameter portion for fitting a pair of permanent magnets is formed so as to be on the same axis as the movable table 20, cylinder to the small-diameter portion a pair of permanent magnets 21 and 22 shape is fitted from axially outside diameter and the outer circumferential surface of the movable member 20 is the same between the outer circumferential surface and these permanent magnets 21 and 22 of these permanent magnets 21 and 22 Thus, the permanent magnet is fixed so that it continues smoothly .
As described above, the outer peripheral surfaces of the permanent magnets 21 and 22 and the outer peripheral surface of the mover 20 are formed so as to be smoothly continuous. Thus, the reciprocating motion of the mover 20 can be performed smoothly.

  The permanent magnets 21 and 22 are made of a cylindrical ferrite ring magnet having the same diameter, and are coaxial with each other. The permanent magnets 21 and 22 have the same axial width as the end portions (projections) 10c and 10d of the yoke 10, and the central portion of the permanent magnet 21 in the axial direction is the yoke when the mover 20 is stopped. 10 is arranged so as to be substantially coincident with the end face 10a of the permanent magnet 22, and the central portion of the permanent magnet 22 is arranged so as to be substantially coincident with the end face 10b of the yoke 10. That is, with the yoke 10 and the mover 20 aligned with each other in the axial direction, the permanent magnets 21 and 22 in the axial direction are approximately half the length in the axial direction from the end faces 10a and 10b of the yoke 10, respectively. Is also set to protrude outward.

  FIG. 2 is a diagram for explaining the operation of the linear actuator shown in FIG. In the linear actuator 1, when no current is passed through the coil 12, the mover 20 is stopped, and as shown in FIG. 2A, the permanent magnet 21, the yoke 10, the mover 20, and the permanent magnet 21. A magnetic flux is formed by a loop connecting in order, and a magnetic flux is formed by a loop connecting the permanent magnet 22, the yoke 10, the mover 20, and the permanent magnet 22 in this order.

Then, an alternating current (sine wave current, rectangular wave current) is passed through the coil 12.
For example, as shown in FIG. 2B, when a current flows through the coil 12 so as to flow in the clockwise direction when viewed from the right side in FIG. 2B, the coil 12 circulates in the direction of the thick line A. Magnetomotive force is generated so that a magnetic flux loop is generated. As described above, when the permanent magnet 21 attempts to align the position in the axial direction with respect to the end portion 10c of the yoke 10, the mover 20 moves in the left direction in the axial direction (right direction in FIG. 2B). .

  Next, as shown in FIG. 2C, when a current flows through the coil 12 in a counterclockwise direction when viewed from the right side in FIG. Magnetomotive force is generated so as to generate a magnetic flux loop that circulates around the surface. As described above, the permanent magnet 22 tries to align the position in the axial direction with respect to the end portion 10d of the yoke 10, so that the movable element 20 moves in the left direction in the axial direction (left direction in FIG. 2C). .

  Then, by alternating the direction of the current flow to the coil 12 by the alternating current, the above operation is repeated, and the mover 20 reciprocates with a predetermined stroke in the axial direction with respect to the yoke 10. Become.

In addition, it is used as a linear motor by providing the support mechanism which supports the needle | mover 20 in the yoke 10 so that linear movement is possible. In addition to the above-described ferrite ring magnet, a permanent magnet such as neodymium or samarium cobalt can be used, or a plastic magnet can be used. However, using a ferrite magnet can reduce costs. More preferable from the viewpoint.
Also, the permanent magnet shape need not be particular about the ring shape, and may be divided in the radial direction (a tile-like one is attached in the circumferential direction so that there is no gap).

  The linear actuator can be used as a linear servo actuator capable of controlling speed and position by providing a sensor for detecting position, speed, etc. and performing closed loop control.

  According to the linear actuator of this embodiment described above, the influence of the magnetic flux generated by the coil magnetomotive force being reduced by the magnetic flux of the permanent magnet of the mover is reduced, and thrust is generated compared to the conventional linear actuator. Efficiency can be increased.

  The embodiment of the present invention has been described above. However, the linear actuator of the present invention is not limited to the illustrated example described above, and various modifications can be made without departing from the scope of the present invention. Of course.

  In the present invention, there is an effect that the amount of cancellation (cancellation) between the magnetic flux generated by the coil magnetomotive force and the magnetic flux of the permanent magnet is reduced. Therefore, the present invention is useful for a linear actuator or the like.

It is a figure which shows the structural example of the linear actuator of this invention. It is operation | movement explanatory drawing of the linear actuator shown in FIG. It is a figure which shows the structural example of the linear actuator of a prior art. It is a figure which shows the application example of the linear actuator of a prior art. It is operation | movement explanatory drawing of the linear actuator shown in FIG.

Explanation of symbols

1, 1a Linear actuator 10, 30, 30a Yoke 10a, 10b End face 10c, 10d, 30b, 30c End (projection part)
11, 31a Concave portion 12, 32, 32a Coil 20, 40, 40a Movable member 21, 22, 41, 41a Permanent magnet

Claims (3)

In a linear actuator having a columnar stator having a through hole in the center, and a mover inserted in the through hole and reciprocally movable along a central axis,
The stator is
A coil housing space portion formed within the predetermined range in the center in the axial direction of the inner peripheral surface of the through hole and having a concave portion with a predetermined depth in the radial direction along the inner peripheral surface;
An end portion formed along the inner peripheral surface of both end surfaces of the through hole of the stator by providing the coil housing space portion;
A cylindrical coil fitted into the coil storage space and wound in parallel with the outer peripheral surface of the mover;
The mover is
A small diameter portion coaxial with the central axis is formed at both ends, respectively,
A pair of permanent magnets having the same diameter cylindrical shape that are fitted from the axial direction to the respective small diameter portions so as to correspond to the respective ends of the inner peripheral surface of the stator, in a stopped state The center of each axial direction is substantially coincident with the outer end surface of the stator, and includes a permanent magnet in a state where magnetic poles are arranged in a direction orthogonal to the axial direction ,
A linear actuator characterized in that the outer peripheral surface of each permanent magnet and the outer peripheral surface of the mover between the permanent magnets are smoothly continuous with the same outer diameter . 2. The linear actuator according to claim 1, wherein the length of the permanent magnet in the axial direction is substantially equal to the length of the end portion of the inner peripheral surface of the stator in the axial direction. The length in the axial direction between the pair of permanent magnets is formed to be larger than the length in the axial direction between the end portions of the inner peripheral surface of the stator. Linear actuator.

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