JPH07303363A - Linear actuator - Google Patents

Abstract

PURPOSE:To position a magnet moving type linear actuator with high accuracy by reducing the size of the actuator and improving the linearity of the thrust of the actuator without reducing the thrust of the actuator nor increasing the cost of the actuator. CONSTITUTION:The axial length L1 of a magnet constituting body 12 (the distance between both outermost ones of a plurality of cylindrical permanent magnets 12a,..., 12f constituting the body 12) forming the mover 1 of a magnet moving type linear actuator and the axial length L2 of a magnetic pole section 22 (the distance between both outermost ones of a plurality of magnetic poles 22a,..., 22g) forming a stator 2 are set in a relation, L1<L2. Therefore the influence of a detent force can be remarkably reduced when a detent force offsetting elastic body which can make the occurrence of a restoring force substantially zero and gives an elastic force to the mover in the axial direction is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a linear actuator used in a wide range of fields such as FA equipment and machine tools, and in particular, it is compact and has high thrust linearity.
The present invention relates to a linear actuator that enables stable and highly accurate positioning.

[0002]

2. Description of the Related Art Conventionally, as a linear actuator, an actuator utilizing current force, such as a VCM (voice coil type linear motor), has been widely used. An actuator that uses current force has the advantage of excellent responsiveness, but on the other hand, the thrust generated per volume is not very large, and the drawback is that the actuator must be upsized in order to obtain a large thrust, and the application range is limited. have.
Further, the ratio of permanent magnets to the members constituting the actuator is large, and there has been a limit to cost reduction.

With the expansion of applications of linear actuators, recently, a large movable thrust force has been obtained, a relatively small amount of magnets used, and a large movable thrust force per volume, ie, a movable magnetic linear actuator, that is, a magnetic force has been used. Actuators have been proposed. As a movable magnet type linear actuator, the configurations as shown in FIGS. 8 to 10 have been conventionally known (published by The Institute of Electrical Engineers of Japan, June 5, 1992, “The Institute of Electrical Engineers of Japan Material Linear Drive Study Group LD- 92-46: Study on Improving Thrust of Movable Magnet Actuator ").

More specifically, FIG. 8 is a vertical cross-sectional explanatory view showing the overall schematic structure, FIG. 9 is a partial detailed vertical cross-sectional explanatory view thereof, and FIG. 10 is a cross-sectional view taken along the line BB of FIG. is there. In the figure, reference numeral 1 denotes a mover, and a plurality of cylindrical permanent magnets 1 magnetized in a radial direction are provided on an outer peripheral portion of a cylindrical movable yoke 11.
12h are alternately magnetized (the directions of the arrows shown in the cylindrical permanent magnets 12a, 12h in FIG. 9 indicate the magnetized directions of the permanent magnets 12a, 12h). It is configured such that magnet constituents 12 that are arranged adjacent to each other in the axial direction so as to be opposite to each other are fixed. In addition, reference numeral 13 in the drawing denotes an output shaft projecting from both ends of the movable yoke 11.

Reference numeral 2 in the drawing denotes a stator, and a plurality of magnetic poles 22a, ... 22 which are opposed to each other in the inner peripheral portion of the cylindrical fixed yoke 21 by forming a predetermined gap with the magnet constituting body 12 of the mover 1.
and a drive coil 23 having a magnetic pole portion 22 of g.
Is arranged in a circumferential direction. Reference numeral 3 in the drawing denotes a support portion of the mover 1, which is composed of a flange portion 32 that supports the output shaft 13 of the mover 1 via a bearing 31 so as to be movable in the axial direction (left-right direction in the drawing). Are fixed to each end of the stator 2.

In the above structure, when a current is applied to the drive coil 23, a predetermined polarity is generated in the magnetic pole portion 22 of the stator 2 (the magnetic poles 22a, which are arranged adjacent to each other in the axial direction in advance).
... Each drive coil 2 so that the polarities of 22g are alternately different.
3 are connected), and the mover 1 moves in a predetermined direction by a magnetic action with each of the cylindrical permanent magnets 12a, ... 12h forming the magnet structure 12 of the mover 1.

[0007]

In the magnet movable type linear actuator described above, it is possible to realize a large thrust and a low price originally possessed by the linear actuator, but it is downsized and the thrust is high. The linearity cannot be realized, and the stable and highly accurate positioning currently required for the linear actuator cannot be achieved.

More specifically, as shown in FIG. 8 (see FIG. 8), the conventional movable magnet type linear actuator has the axial length L _{1 of} the magnet assembly 12 constituting the mover ₁ , that is, the magnet assembly 12 as shown in FIG. A plurality of cylindrical permanent magnets 12a,
The cylindrical permanent magnets 12 located at both ends of 12h.
a and the length between the outer end portions of 12h and the axial length L _{2 of} the magnetic pole portion 22 constituting the stator ₂ , that is, the magnetic poles 22a located at both ends of the plurality of magnetic poles 22a, ...
And the length between the outer ends of the magnetic poles 22g, the lengths L ₁ and L ₂ in the axial direction at the facing portions of the magnet structure 12 and the magnetic pole portions 22 are equal, so that the mover 1 moves Accordingly, a part of the magnet structure 12 is located outside the stator 2 (magnetic pole part).

For example, when the mover 1 moves to the right in the drawings (see FIGS. 8 and 9), the cylindrical permanent magnet 12a at the right end forming the magnet assembly 12 moves to the right from the right end of the magnetic pole 22a. The magnetic flux generated from the cylindrical permanent magnet 12a moves and leaks. Such a mover 1
And the stator 2 are in a positional relationship, the cylindrical permanent magnet 12a moved to the outside of the magnetic pole 22a and the magnetic pole 22a (stator 2)
A magnetic attraction force, that is, a restoring force for attracting the mover 1 to the central portion of the stator 2 is generated between the movable element 1 and the end of the stator 2.

This restoring force changes depending on the position of the mover 1 and is superposed on the thrust that is originally generated by passing a current through the drive coil 23. Therefore, this is a factor that impedes the high linearity of the thrust of the mover 1. Has become. As a means for reducing the generation of this restoring force as much as possible, a magnetic material is used as the flange portion 32 that constitutes the support portion 3, and the substantial axial length L ₂ of the magnetic pole portion 22 (stator 2) is increased. However, it is not necessarily a good idea from the viewpoint of miniaturization.

Further, even if the restoring force can be reduced by disposing the flange portion 32 made of a magnetic material, the detent force (the mover 1 moves to a magnetically stable position without energizing the drive coil 23). An attempted force, that is, a force to move the mover 1 to one end of the stator 2) is generated, and as a result, high linearity of thrust cannot be achieved.

The present invention is proposed for the purpose of solving the above-mentioned problems, and it is possible to reduce the size of the magnetic linear actuator without impairing the advantages of the large movable thrust actuator and the low price. The main purpose is to provide a linear actuator that achieves high linearity of thrust.

[0013]

According to the present invention, as a result of examining various configurations in order to achieve the above-mentioned object, the mover 1
By reducing the axial length L ₁ of the magnet structure 12 constituting the magnetic pole portion 22 to be smaller than the axial length L ₂ of the magnetic pole portion 22 constituting the stator 2, generation of a restoring force is reduced, Further, they have found that the object can be achieved by disposing an elastic body that gives an elastic force to the mover in the axial direction in order to cancel the detent force, and thus completed the invention.

That is, according to the present invention, at least a pair of cylindrical permanent magnets magnetized in the radial direction are arranged adjacent to each other in the axial direction in the outer peripheral portion so that the directions of the magnetization are alternately opposite. A magnet having a body, and a stator having a magnetic pole portion formed on the inner peripheral portion thereof to face the magnet structure and facing each other and having a drive coil wound around the magnet structure. The axial length of the magnetic pole portion is smaller than the axial length of the magnetic pole portion, and a detent force canceling elastic body that applies an elastic force to the movable element in the axial direction is arranged. It is an actuator.

[0015]

The operation of the linear actuator of the present invention will be described based on an embodiment shown in FIGS. 1 is a vertical cross-sectional explanatory view showing the overall schematic configuration, and FIG. 2 is a cross-sectional explanatory view taken along the line AA of FIG. Further, FIG. 3 is a vertical cross-sectional explanatory view showing a schematic configuration of another embodiment. Furthermore, FIGS.
FIG. 4 is a partial detailed explanatory view showing an arrangement configuration of a detent force canceling elastic body other than the arrangement configuration of the detent force canceling elastic body shown in the configurations of FIGS. 1 and 3. In FIG. 1, reference numeral 1 is a mover, and a plurality of (6 in the figure: 3 pairs) cylindrical permanent magnets 12a magnetized in the radial direction are provided on the outer peripheral portion of a substantially cylindrical movable yoke 11. … 1
2f is the direction of magnetization (in FIG. 1, the cylindrical permanent magnet 12
The directions of the arrows shown in a, ...
2a, ..., 12f) (showing the magnetization directions of 12a) are alternately reversed, and the magnet constituents 12 arranged adjacent to each other in the axial direction are fixed. In addition, 13 in the figure
Penetrates through the central portion of the movable yoke 11,
1 is an output shaft projecting from both ends.

Reference numeral 2 in the drawing denotes a stator, and a plurality of magnetic poles 22a, ... 22 which are opposed to each other in the inner peripheral portion of the cylindrical fixed yoke 21 by forming a predetermined gap with the magnet constituting body 12 of the mover 1.
and a drive coil 23 having a magnetic pole portion 22 of g.
Is arranged in a circumferential direction. Reference numeral 3 in the drawing denotes a support portion of the mover 1, which is composed of a flange portion 32 that supports the output shaft 13 of the mover 1 via a bearing 31 so as to be movable in the axial direction (left-right direction in the drawing). Are fixed to each end of the stator 2. The flange portion 32 is made of a flat non-magnetic material. 4 in the figure
Reference numerals a and 4b are elastic bodies for canceling the detent force, which are coil springs, and are arranged between both end portions of the movable yoke 11 and inner peripheral surfaces of the flange portions 32, and the movable element 1 is fixed as shown in the drawings. When in the center position of the child 2, elastic force acts in a direction (axial direction) that presses both ends of each movable yoke 11.

In the above structure, when a current is applied to the drive coil 23, a predetermined polarity is generated in the magnetic pole portion 22 of the stator 2 (each of the magnetic poles 22a, which are arranged adjacent to each other in the axial direction in advance).
... Each drive coil 2 so that the polarities of 22g are alternately different.
3 are connected), and the mover 1 moves in a predetermined direction by a magnetic action with each of the cylindrical permanent magnets 12a, ... 12f forming the magnet structure 12 of the mover 1. In the configuration of the present invention, as shown in the figure, the axial length L _{1 of the} magnet assembly 12 is smaller than the axial length L _{2 of the} magnetic pole portion 22, and the magnet is always in the moving range of the mover 1. Since the structural body 12 and the magnetic pole portion 22 are arranged so as to face each other, the generation of the restoring force is reduced, and moreover, the detent force is elastic by arranging the detent force canceling elastic bodies 4a and 4b having a predetermined spring constant. This is offset by the force, and the desired high linearity of thrust can be achieved.

The embodiment shown in FIG. 3 shows the simplest construction of the linear actuator of the present invention, in which the magnet assembly 12 constituting the mover 1 comprises a pair of cylindrical permanent magnets 12a, 12b. The magnetic pole portion 22 facing the magnet structure 12 with a predetermined gap is also composed of three magnetic poles 22.
a, 22b, and 22c only, the axial length L _{1 of} the magnet structure 12 is smaller than the axial length L ₂ of the magnetic pole portion, and both end portions of the movable yoke 11 and the flange portion 32 are formed. By arranging the elastic bodies 4a and 4b for canceling the detent force, which are coil springs, between the inner peripheral surface and the inner peripheral surface, respectively, as shown in FIG.
It is possible to obtain the same effect as that of the linear actuator having the configuration shown in FIG.

In the linear actuator of the present invention described above, each of the cylindrical permanent magnets 1 constituting the mover 1 is formed.
2a, ... 12f (in the case of FIG. 1) or 12a, 12b
Since (in the case of FIG. 3) is magnetized in the radial direction, a known cylindrical permanent magnet having anisotropy in the radial direction, such as a Fe—BR type sintered magnet or an R—Co type sintered magnet. Alternatively, a configuration in which a plurality of bow-shaped permanent magnets are arranged in a cylindrical shape can be adopted.

The linear actuator of the present invention requires at least a pair of cylindrical permanent magnets that are magnetized in the above-described magnetization direction and have magnetization directions that are alternately opposite to each other. It is desirable to select the quantity as well as the magnet material according to the dimensions. Further, in the configurations of FIGS. 1 and 3, the axial end faces of the adjacent cylindrical permanent magnets are arranged so as to abut each other, but the present invention is not limited to this configuration, and the axial end faces form a predetermined gap. Even if it is arranged as described above (see FIG. 8), the desired effect can be obtained.

In the present invention, the movable yoke 11 for supporting the magnet structure 12 is not limited to the structure shown in the figures, and the output shaft 13 and the output shaft 13 may be formed within a range that does not hinder the formation of the magnetic path in order to reduce the weight of the mover 1. It is also possible to configure the connection part of the aluminum alloy or the like. Further, although not desirable from the viewpoint of forming a good magnetic path, the magnet structure 12 is attached to the movable yoke 11.
Alternatively, even if the non-magnetic support member having the same shape as the movable yoke 11 is connected and fixed to the output shaft 13, the linearity of the thrust can be realized.

The structure of the stator 2 is not limited to the structure shown in FIGS. 1 and 3, and the magnet structure 12 is provided on the inner peripheral portion.
It is not always necessary to form a cylindrical shape as a whole as long as it has a structure in which a predetermined drive coil 23 is wound and arranged by forming a predetermined gap and opposing magnetic pole portions 22. That is, the inner peripheral portion where the mover 1 is arranged (the inner peripheral surface of the magnetic pole portion 22).
However, it may be formed in a predetermined shape so as not to hinder the movement of the mover 1 in the axial direction, and the outer peripheral portion may be rectangular. In particular, the stator 2 as a whole is made of a laminated body of silicon steel sheets, or a bulk material and a laminated body of silicon steel sheets are used in combination, and a specific configuration is selected in consideration of workability, assemblability, and the like. Is desirable.

As described above, in order to reduce the generation of the restoring force, the axial length L ₁ of the magnet assembly 12 is made smaller than the axial length L ₂ of the magnetic pole portion 22. It is necessary and selected according to the required movement amount of the mover 1 (stroke S), thrust force, etc., but at least (L ₂ −S) / L ₁ ≧ 1 is required to reduce the generation of restoring force. , Preferably L ₁ + S ≦ L ₂ ≦ L ₁ + S + P (P; a pair of magnet widths).

As the detent force canceling elastic body 4 for applying an elastic force to the mover 1 in the axial direction, the detent force generated based on the configurations of the mover 1 and the stator 2 is measured in advance. , It is desirable to select an elastic body having a spring constant that cancels the detent force.
The elastic body is not limited to the coil spring shown in FIGS. 1 and 3, and a leaf spring, a rubber film, or the like can be used, and various arrangements can be adopted for the arrangement as shown in FIGS. 4 to 6. .

That is, in FIG. 4, the flanges 14a and 14b are formed at both ends of the output shaft 13, and the flanges 14a and 14b and the non-magnetic flanges 32a and 3 fixed to both ends of the stator 2 are formed.
2 shows a configuration in which elastic bodies 4a and 4b for canceling the detent force, which are coil springs, are arranged between the elastic bodies 4b and 2b.
In this configuration, the mover 1 (not shown) is the stator 2
Of the detent force canceling elastic bodies 4a, 4b at the center position of
The elastic force acts in the direction (axial direction) of pressing 4b.

In FIG. 5, a flange portion 14 is formed on one side of the output shaft 13, and between the flange portion 14 and one non-magnetic flange 32 a fixed to the stator 2, and between the flange portion 14 and the stator 2. It shows a structure in which elastic bodies 4a and 4b for canceling the detent force, which are coil springs, are arranged between the end surface of a jig 5 provided in the vicinity thereof. In the figure, 51 is a through hole formed in the jig 5 for moving the output shaft 13. In this configuration,
When the mover 1 (not shown) is at the center position of the stator 2, the elastic bodies 4a and 4b for canceling the detent force are elastic forces in the direction (axial direction) pressing the flange portion of the output shaft 13. Is working.

In FIG. 6, the non-magnetic flange 32 for supporting the output shaft 13 is formed of a rubber film, and the non-magnetic flange 32 made of the rubber film functions as an elastic body for canceling the detent force. The rubber film 32 is arranged at one end or both ends of the stator 2. In this configuration, the mover 1
Is not applied to the mover 1 in the axial direction when is at the center position of the stator 2, it is possible to apply the elastic force in the detent force canceling direction as the mover 1 moves. Become. Besides the elastic body for canceling the detent force described above, various configurations can be adopted,
As explained above.

[0028]

【Example】

Example 1 As an example of the present invention, a linear actuator having the configuration shown in FIG. 3 was produced. As the cylindrical permanent magnets 12a and 12b constituting the magnet structure 12, Fe-BR type arc-shaped sintered magnets having a maximum energy product (BH) max = 40MGOe were used in a cylindrical shape. The outer diameter of the linear actuator was 68 mm, the length (thickness) was 48 mm, and the length of the output shaft was 68 mm. Incidentally, the difference between the axial length L ₂ of the axial length L ₁ and the magnetic pole portion 22 of the magnet arrangement 12 and 12 mm, and set the amount of movement of the mover 1 (stroke) in 4 mm, the detent force Upon measurement, the value indicated by the broken line in FIG. 7 was obtained. In addition, in this structure, the restoring force was substantially zero.

Based on the above measured values of detent force,
When the elastic bodies 4a, 4b for canceling the detent force, which are coil springs having a predetermined spring constant (about 0.4 kgf / mm), are arranged at the positions shown in FIG. 3, they are limited to the moving position of the mover 1 as shown in FIG. Without these, the resultant force is almost zero,
It was confirmed that high linearity of thrust could be realized. According to the experiment, the maximum value of the generated thrust is about 9 kgf, and the fluctuation of the thrust in all strokes is less than 5%.

Embodiment 2 A linear actuator of the present invention shown in FIG. 1 and a conventional linear actuator shown in FIG. 8 for obtaining a similar thrust (maximum value = 80 kgf) (however, a magnetic material flange is used to reduce the restoring force). ) And were measured, and the size thereof was measured, it became possible that the linear actuator of the present invention had a length of about 3/4 that of the conventional linear actuator.

[0031]

The linear actuator of the present invention has a large thrust which the magnet movable type linear actuator originally has,
By making the axial length of the magnet structure smaller than the axial length of the magnetic pole portion without impairing the merit of lowering the cost, the generation of restoring force is made substantially zero, and the moving element By arranging the elastic body for canceling the detent force that gives elastic force in the axial direction, it is possible to significantly reduce the influence of the detent force, and to provide a linear actuator that realizes downsizing and high linearity of thrust. Made possible

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view showing a schematic configuration of an entire linear actuator of the present invention.

2 is a cross-sectional view taken along the line AA of FIG.

FIG. 3 is a vertical cross-sectional explanatory view showing a schematic configuration of another embodiment of the linear actuator of the present invention.

FIG. 4 is a partial detailed explanatory view showing the arrangement configuration of another elastic body for canceling the detent force of the linear actuator of the present invention.

FIG. 5 is a partial detailed explanatory view showing an arrangement configuration of a detent force canceling elastic body according to another embodiment of the present invention.

FIG. 6 is a partial detailed explanatory view showing an arrangement configuration of a detent force canceling elastic body according to another embodiment of the present invention.

7 is a graph showing experimental data for confirming the effect of the elastic body for canceling the detent force in the linear actuator of FIG.

FIG. 8 is a vertical cross-sectional explanatory view showing the overall schematic configuration of a conventional linear actuator.

FIG. 9 is a partial detailed vertical cross-sectional explanatory view of a conventional linear actuator.

10 is a cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mover 2 Stator 3 Support part 4a, 4b Detent force canceling elastic body 5 Jig 11 Movable yoke 12 Magnet composition 12a-12h Cylindrical permanent magnet 13 Output shaft 14, 14a, 14b Collar part 21 Cylindrical fixed yoke 22 magnetic pole part 22a-22g magnetic pole 23 drive coil

Claims (1)

[Claims] 1. A movable member having, on its outer peripheral portion, a magnet assembly in which at least a pair of cylindrical permanent magnets magnetized in a radial direction are arranged adjacent to each other in the axial direction such that the directions of magnetization are alternately opposite. A stator and a stator having a magnetic pole portion formed on the inner peripheral portion of the magnet constituent member and forming a predetermined gap to face the magnet constituent member, and having a drive coil wound around the magnet constituent member. A linear actuator characterized in that a length is smaller than an axial length of a magnetic pole portion, and an elastic body for canceling a detent force for arranging an elastic force in an axial direction is arranged on the mover.