JP2009130943A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear actuator that is used well over a long term even if it is immersed in oil. <P>SOLUTION: A linear actuator includes a stator, a moving member having a shaft 6 supported reciprocally by the stator, a means for generating thrust in the moving member in the reciprocal direction, and a magnet 32 arranged opposite to the surface of the shaft 6. In such a constitution, the shaft 6 is reciprocated with thrust generated by the thrust generation means. Magnetic powder flowing through oil can be attracted by the magnetic force of the magnet. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a linear actuator that reciprocates a mover.

Conventionally, a linear actuator that reciprocates a mover by electromagnetic action is known (for example, see Patent Document 1). These linear actuators generally include a mover having a shaft portion and a stator that supports the mover so as to reciprocate. In such a linear actuator, a thrust is applied to the mover by a magnetic force to reciprocate the mover.
Here, in recent years, for example, using a linear actuator in a transmission or a gear box, it has been studied to perform a gear change that has been performed by hydraulic pressure until now by an electromagnetic action by the linear actuator.
In order to use the linear actuator in a transmission or the like, it is necessary to provide the linear actuator in oil.
Japanese Utility Model Publication No. 57-52787

  However, when the linear actuator is provided in the oil as described above, fine magnetic powder (abrasion powder) generated from a gear or the like flows into the oil, so that the magnetic powder enters the linear actuator. There is a problem. In addition, there is a problem that magnetic powder or the like enters the bearing used.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the linear actuator which can be used favorably for a long time also in oil.

In order to solve the above problems, the present invention provides the following means.
The present invention relates to a stator, a mover having a shaft part supported by the stator so as to be reciprocally movable, thrust generating means for generating a thrust in the reciprocating direction on the mover, and a surface of the shaft part And a magnet disposed opposite to the magnet.

In this invention, the shaft portion reciprocates by the thrust from the thrust generating means, and the magnetic powder flowing in the oil is attracted by the magnetic force of the magnet.
This prevents the magnetic powder from entering the inside.

  Further, the present invention is characterized in that the magnetic poles of the magnet are directed in the reciprocating direction, and yokes are provided on both sides of the magnet in the reciprocating direction.

  According to this invention, the magnetic flux from a magnet can be guided easily and reliably, and magnetic powder can be adsorbed effectively.

  Further, according to the present invention, the magnet and the yoke are formed in an annular shape, and the inner diameter dimension of the magnet and the yoke is larger than the outer diameter dimension of the shaft portion. The part is inserted, It is characterized by the above-mentioned.

  According to this invention, it is possible to reliably prevent the magnetic powder from entering between the magnet and the yoke and the shaft portion.

  Further, the present invention is characterized in that the outer diameter of the magnet and the yoke are the same, and the inner diameter of the magnet is larger than the inner diameter of the yoke.

  According to the present invention, a magnetic flux loop from the magnet can be easily formed between the magnet and the yoke and the shaft portion.

  According to the present invention, the magnetic powder in the oil can be attracted by the magnetic force of the magnet, so that it can be used well in the oil for a long time.

(Embodiment 1)
Hereinafter, a linear actuator according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a linear actuator as a first embodiment of the present invention.
The linear actuator 1 is provided with a rectangular parallelepiped and hollow case 2 as shown in FIGS.
A fixed core (stator) 10 made of a magnetic material is provided on the inner surface of the case 2. The fixed core 10 includes first annular bodies 11a and 11b formed in an annular shape. The first annular bodies 11a and 11b are formed in an L-shaped cross section, and their bottom surface portions are arranged to face each other. A permanent magnet 12 having the same shape is provided between the bottom portions of the first annular bodies 11a and 11b.

The magnetic pole of the permanent magnet 12 is directed in the reciprocating direction of a shaft 6 (shaft portion, mover) described later. For example, the first annular body 11b side is the south pole, and the second annular body 11a side is the north pole. The reciprocating direction is the direction of the axis L of the shaft 6.
In addition, second annular bodies 13a and 13b having an L-shaped cross section are provided at the ends of the first annular bodies 11a and 11b in the axis L direction. The bottom portions of the second annular bodies 13a and 13b are arranged to face each other. And the recessed parts 14a and 14b are each formed by the level | step-difference part 16a, 16b of 1st annular body 11a, 11b and the bottom face part of 2nd annular body 13a, 13b.
Coils (thrust generating means) 20a and 20b are provided in the recesses 14a and 14b, respectively.
Moreover, the vertical wall part orthogonal to the bottom face part of 2nd annular body 13a, 13b is provided with taper 18a, 18b which becomes thick as it goes to the front-end | tip of an axis L direction.

Further, through holes 3a and 3b are formed at the centers of both end faces 2a and 2b in the longitudinal direction of the case 2, respectively. Bearings 7a and 7b are provided in the through holes 3a and 3b, respectively. A shaft 6 extending in a columnar shape is inserted into the bearings 7a and 7b. The shaft 6 is made of a metal such as iron. Under such a configuration, the shaft 6 is supported by the bearings 7a and 7b so as to be capable of reciprocating in the direction of the axis L.
The shaft 6 is provided with a cylindrical movable core (movable element) 23. That is, when the shaft 6 is press-fitted into the cylindrical hole 23 a of the movable core 23, the movable core 23 is fixed to the central portion in the longitudinal direction of the shaft 6.

The movable core 23 is made of a magnetic member, and a projecting portion (thrust generating means) 27 projecting radially outward is provided at the center in the longitudinal direction (axis L direction). The protruding portion 27 is formed in a rectangular cross section, and the tip surface thereof faces the inner peripheral surface of the permanent magnet 12 and the fixed core 10. Further, flanges 24a and 24b extending in a direction orthogonal to the axis L direction are provided on both end faces of the movable core 23 in the longitudinal direction. The flanges 24 a and 24 b are provided over the entire circumference of both end surfaces of the movable core 23. The outer edge portions of the flanges 24 a and 24 b extend radially outward from the inner edge portion of the fixed core 10. That is, the outer edge portions of the flanges 24 a and 24 b overlap the fixed core 10 when viewed from the axis L direction. These flanges 24a and 24b function as suction force generating means for sucking the movable core 23 in the direction of the axis L.
Further, on the surface side of the edge portions of the flanges 24a and 24b, tapers 25a and 25b are formed so as to become thinner toward the outer side in the radial direction.
Since the tapers 25a, 25b, 18a, and 18b are formed, the gap does not change abruptly, and therefore a sudden change in magnetic flux can be prevented.

  Under such a configuration, when the coils 20a and 20b are energized, the movable core 23 and the shaft 6 are reciprocated by the magnetic flux from the coils 20a and 20b and the magnetic flux of the permanent magnet 12.

Further, in the present embodiment, an adsorbing portion 30 for adsorbing magnetic powder is provided in the center of both end faces 2a, 2b of the case 2.
As shown in FIG. 2, the attracting part 30 includes an annular magnet 32 formed in a cylindrical shape. The annular magnet 32 is a permanent magnet. The magnetic pole of the annular magnet 32 is oriented in the direction of the axis L, the case 2 side is the N pole, and the opposite side (the tip side of the shaft 6) is the S pole. Cylindrical yokes 33a and 33b formed coaxially are provided on both ends of the annular magnet 32 in the axis L direction. The annular yokes 33a and 33b are made of a magnetic member.
The shaft 6 is inserted through the annular magnet 32 and the annular yokes 33a and 33b.

The outer diameter r3 of each of the annular magnet 32 and the annular yokes 33a and 33b is the same. Further, the inner diameters r1 of the annular yokes 33a and 33b are the same. Further, the inner diameter r1 is larger than the outer diameter r4 of the shaft 6. Further, the inner diameter r2 of the annular magnet 32 is larger than the inner diameter r1.
Therefore, when the shaft 6 is inserted through the annular magnet 32 and the annular yokes 33a and 33b, the gaps G2, G1a, Gp between the outer peripheral surface of the shaft 6 and the inner peripheral surfaces of the annular magnet 32 and the annular yokes 33a and 33b. G1b is formed.
Since the inner diameter r2 is larger than the inner diameter r1, the distance d2 between the outer peripheral surface of the shaft 6 and the inner peripheral surface of the annular magnet 32 in the gap G2 is the outer periphery of the shaft 6 in the gaps G1a and G1b. It is larger than the distance dimension d1 between the surface and the inner peripheral surfaces of the annular yokes 33a and 33b.

  With such a configuration, as shown in FIG. 3, the magnetic flux of the annular magnet 32 exits from the N pole, passes through the annular yoke 33b, and exits from the inner peripheral surface thereof into the gap G1b. Then, the magnetic flux is bent to the opposite side of the case 2 in the gap G1b, proceeds along the axis L, passes through the gap G2, passes through the gap G1a of the annular yoke 33a, and the inner circumference of the annular yoke 33a. It enters the annular yoke 33a from the surface and returns to the south pole of the annular magnet 32. Thereby, the magnetic flux loop M is formed.

Next, the operation of the linear actuator 1 according to this embodiment configured as described above will be described.
When currents in opposite directions are passed through the coils 20a and 20b, magnetic fluxes from the coils 20a and 20b and the permanent magnet 12 reach the flange 24a through the first annular body 11a and the second annular body 13a. . Then, the magnetic flux passes through the movable core 23, returns from the protrusion 27 through the first annular body 11 b, and returns to the S pole of the permanent magnet 12. Thereby, a magnetic pole is formed between the front end surface of the protrusion part 27 and the inner peripheral surface of the fixed core 10, and the thrust of an axis L direction acts. Therefore, the shaft 6 moves in the direction of the axis L via the movable core 23. For example, in the state of FIG. 1, the flange 24 b is in contact with the fixed core 10, and from this state, the shaft 6 moves in the right direction (the direction of the first annular body 11 b with respect to the permanent magnet 12). At this time, since the outer edge of the flange 24a extends radially outward from the inner edge of the fixed core 10, a magnetic pole is formed between the fixed core 10 and the flange 24a. Then, the shaft 6 is sucked rightward through the flange 24a and the movable core 23.
Therefore, the attractive force by the magnetic pole of the flange 24a is added to the thrust by the magnetic pole of the protrusion 27, and the shaft 6 moves in the right direction.
Furthermore, the shaft 6 reciprocates by alternately changing the direction of the current flowing through the coils 20a and 20b.

Here, conventionally, when the linear actuator is provided in oil, there is a possibility that magnetic powder flowing in the oil may enter the linear actuator.
In the linear actuator 1 in the present embodiment, intrusion of magnetic powder is prevented as follows.
That is, as shown in FIG. 3, the magnetic powder F flowing in the oil A tends to enter the case 2 through the gaps G1a, G2, G1b. At this time, since the magnetic flux loop M by the magnetic flux of the annular magnet 32 is formed in the gaps G1a, G2, and G1b, the magnetic powder F that has entered the gap G1a is annularly formed by the magnetic force as shown in FIG. It is attracted to the inner peripheral surface of the yoke 33a. Even if the gap G1a can be passed, the gap G1b is attracted to the inner peripheral surface of the annular yoke 33b. Therefore, the gap G2 is filled with magnetic powder soaked in oil to form an oil seal. After the oil seal is formed, it is possible to prevent the magnetic powder and the like from entering the case.

As described above, according to the linear actuator 1 in the present embodiment, the magnetic powder F can be attracted to the inner peripheral surfaces of the annular yokes 33a and 33b by the magnetic force of the annular magnet 32. Intrusion can be prevented. Moreover, since penetration | invasion of the magnetic powder F is blocked | prevented, durability, such as bearing 7a, 7b, can be improved.
Therefore, it can be satisfactorily used in the oil A for a long time.
Conventionally, an oil seal can be provided on the rotary shaft, but it has been difficult to provide an oil seal on the reciprocating shaft. According to the linear actuator 1 in the present embodiment, since it is provided in the oil A, an oil seal in the gaps G1a, G1b, and G2 can be easily provided even with the shaft 6 that reciprocates.

Further, since the distance dimension d2 is larger than the distance dimension d1, a magnetic flux loop along the axis L can be reliably formed in the gaps G1a, G1b, and G2.
Further, since the flanges 24a and 24b are provided, it is possible to generate a suction force by using energy for generating a thrust, and accordingly, the shaft 6 can be appropriately reciprocated with a small amount of energy. Can do. Therefore, not only can the efficiency be improved with a simple configuration, but also the size can be easily reduced.
In other words, since a reduction in thrust at the stroke end of the shaft 6 can be compensated by the suction force, a large thrust can be generated throughout the entire stroke of the shaft 6. Further, the direction of thrust generation can be easily changed depending on the energization direction of the coils 20a and 20b. This is due to the fact that the central pole of the electromagnet is the N pole and the S pole, and that the opposing magnetic pole (projecting portion 27) has a convex shape.
Further, at the stroke end of the shaft 6, an attractive force is generated in the flanges 24 a and 24 b by the magnetic flux of the permanent magnet 12, so that the position at the stroke end of the shaft 6 can be maintained even when the energization of the coils 20 a and 20 b is stopped (with no current). Holding is possible. This force is further increased by energization.

Here, in automobiles and the like, the replacement of hydraulic actuators with electric actuators and the like has been studied, but naturally there is a demand for a small actuator that generates a large thrust. If it is the structure of a magnetic circuit like the linear actuator 1 which concerns on this embodiment, it will become possible to provide an actuator of a small large thrust. In a lock mechanism or the like, it is necessary to keep the state in which the shaft 6 is moved in one direction. According to the linear actuator 1, the position can be held even when no power is supplied. What is necessary is just to increase the electric current applied to the coils 20a and 20b, and the lock mechanism can be realized with low power consumption.
Further, opening and closing of the compressor and the valve often requires a large thrust at the stroke end of the shaft 6, and an actuator that can generate a large thrust at the stroke end of the shaft 6, such as the linear actuator 1. Application can greatly contribute to improving the efficiency and downsizing of these devices.

(Embodiment 2)
Next, a second embodiment of the present invention will be described.
FIG. 5 shows a second embodiment of the present invention.
In FIG. 5, the same components as those shown in FIGS. 1 to 4 are denoted by the same reference numerals, and the description thereof is omitted.
This embodiment and the first embodiment have the same basic configuration, and only the differences will be described here.

In the present embodiment, the suction portion 30 is provided on the inner peripheral surfaces of the both end faces 2a and 2b of the case 2 (in the through holes 3a and 3b). In addition, the bearings 7a and 7b in the first embodiment are not provided.
Under such a configuration, by providing the linear actuator 1 a in oil, an oil seal is provided in the gap between the shaft 6 and the suction portion 30. In addition, since the gap G2 between the shaft 6 and the annular magnet 32 is filled with magnetic powder immersed in oil, the degree of freedom on the annular magnet 32 side of the shaft 6 is restricted, and the reciprocating motion of the shaft 6 is supported. Therefore, it is not necessary to provide separate bearings (7a and 7b shown in FIG. 1).
From the above, not only the same effects as the first embodiment can be achieved, but also the configuration can be simplified.

The technical scope of the present invention is not limited to the first and second embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, although the annular magnet 32 is a permanent magnet, it may be an electromagnet. Thereby, the attractive force of the magnetic powder F can be controlled. Specifically, a metal sensor is provided in the vicinity of the entrance of the magnetic powder F, and when the output from the metal sensor is read and it is determined that the magnetic powder F is large, a control unit is provided to increase the magnetic force by the electromagnet. Is also possible.

The coils 20a and 20b may be provided on the movable core 23. However, it is preferable to provide the coils 20a and 20b on the fixed core 10 side because there is no fear of disconnection due to movement.
Although the shaft 6 is supported by the bearing member, the present invention is not limited to this, and the shaft 6 may be supported by an elastic body such as a coil spring or a leaf spring.
Moreover, it can change suitably as a structure which makes the shaft 6 reciprocate. For example, a movable iron core may be used, or a solenoid or the like may be provided.
Moreover, although the outer side is the fixed core 10 and the inner side is the movable core 23, the present invention is not limited to this, and the outer member may be a movable element and the inner member may be a stator.
The configuration of the thrust generating means of the linear actuator can be changed as appropriate. For example, any type that can reciprocate such as a voice coil type or a linear solenoid may be used.

It is a figure which shows 1st Embodiment of the linear actuator which concerns on this invention, Comprising: (a) is sectional drawing which shows a mode seen from the side surface, (b) is the front view seen from the axis line L direction. It is sectional drawing which expands and shows the adsorption | suction part of FIG. It is explanatory drawing which shows a mode that a magnetic powder tries to penetrate | invade into the adsorption | suction part of FIG. It is explanatory drawing which shows a mode that the magnetic powder was adsorb | sucked to the adsorption | suction part of FIG. It is sectional drawing which shows 2nd Embodiment of the linear actuator which concerns on this invention from a side surface.

Explanation of symbols

1,1a Linear actuator 6 Shaft (shaft, mover)
10 Fixed core (stator)
20a, 20b coil (thrust generating means)
23 Movable core (movable element)
27 Protrusion (thrust generating means)
32 annular magnet 33 annular yoke

Claims (4)

A stator,
A mover having a shaft portion reciprocally supported by the stator;
Thrust generating means for generating a thrust in the reciprocating direction on the mover;
A linear actuator comprising: a magnet arranged to face the surface of the shaft portion. The magnetic pole of the magnet is oriented in the reciprocating direction;
The linear actuator according to claim 1, wherein yokes are provided on both sides of the magnet in the reciprocating direction. The magnet and the yoke are formed in an annular shape,
The inner diameter dimension of the magnet and the yoke is larger than the outer diameter dimension of the shaft portion,
The linear actuator according to claim 2, wherein the shaft portion is inserted through the magnet and the yoke. The outer diameter of the magnet and the yoke are the same,
The linear actuator according to claim 3, wherein an inner diameter of the magnet is larger than an inner diameter of the yoke.

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