JPH03112354A - Linear actuator - Google Patents

Abstract

PURPOSE:To provide a simple supporting and guiding mechanism, to finely move without detection of a position and to reduce in size a linear actuator by forming a movable element of two sets each having two permanent magnets having different polarities as one set, and forming a stator of two cores of U shape in which coils are wound. CONSTITUTION:When a current so flows to a coil 31 as to generate an N pole at the right end of a stator core 11 and an S pole at the left end and a current so flows to a coil 32 as to generate an S pole at the right end of a lower stator core 12 and an N pole at the left end, a driving force is generated by attraction and repelling of a permanent magnet 2 and stator cores 11, 12, and a movable element moves leftward. On the other hand, a spring 6 is stabilized at a predetermined position, and a spring force F1 of spring constant K is generated in response to a lateral displacement (x). Thus, its structure can be simplified to be reduced in size.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a linear actuator, and particularly to a linear actuator suitable for use in a device that moves a minute distance at high speed.

[Conventional technology]

JP-A-62-193553 discloses a technique related to a permanent magnet type linear electromagnetic actuator that can improve the thrust constant compared to the voice coil type actuator used in dynamic speakers.

This consists of a cylindrical mover made of a permanent magnet that is supported and guided to move in the axial direction, and an electromagnet that applies a unipolar magnetic field to the cylindrical mover by sandwiching it from the inside and outside. The magnetic pole face facing the outer and inner circumferential surfaces of the cylindrical mover with a gap therebetween includes a stator having inductor teeth at a constant pitch, and means for passing an alternating current through the stator electromagnet.

[Problem to be solved by the invention]

However, in the above-mentioned prior art, there is no particular disclosure regarding the supporting and guiding mechanism of the movable element when the actuator is used for micro-movement applications such as positioning of a magnetic head, and the device is Although miniaturization has been attempted in the past, there is a problem that the support mechanism cannot be made into a /11 type, and there is room for improvement in this respect.

Similarly, in the case of micro-movement applications, providing a plurality of inductors or providing multiple permanent magnets with multiple poles inevitably results in an actuator length that is large relative to the amount of displacement.

Furthermore, there is also the problem that positioning within one pinch is not possible unless the amount of displacement is detected and the current is cut off.

The present invention has been made in consideration of the above points, and includes:
The purpose is to provide a linear actuator that has a simple support and guide mechanism, allows minute movement without position detection, and can be miniaturized.

Another object of the present invention is to eliminate the influence of leakage magnetic fields, which is a problem when considering the use of magnetic heads and the like.

(1) [Means for solving the problem] As a specific means for achieving the above object, the mover of the actuator is composed of two sets of permanent magnets, one set of two different polarity permanent magnets, and is fixed. The child consists of two U-shaped cores with coils wound around them, and the stator is placed with the mover sandwiched between them with a gap in between. In addition, the movable element is connected to the stator by a spring so that it is stabilized at a position where the polar boundary line of one set of permanent magnets and the center of one tip of the stator core coincide, and the spring is movable. It has spring characteristics only in the direction of movement of the child, and has high rigidity in other directions.

Further, as a specific means for achieving the other object, the actuator is covered with a soft magnetic material.

[Effect]

In the movable element of the actuator, a north pole is formed at one end of the stator core and an south pole is formed at the other end by passing a current through the coil of the stator. Since the polarity boundary of the permanent magnet of the mover and the center of the tip 4 surface of the stator core coincide, the magnetic pole side with the opposite polarity to the tip of the stator core is attracted, and the magnetic pole side with the same polarity is repelled. Thrust is generated in one direction. On the other hand, since the mover is connected to the stator by a spring, and this spring has spring characteristics only in the moving direction of the mover and has high rigidity in other directions, the mover , the displacement settles to the same value as the thrust and spring force. Furthermore, since the strength of the magnetic field induced in the stator core changes in proportion to the magnitude of the current, the thrust changes in proportion to the current value. Therefore, the amount of displacement of the movable element is proportional to the current value, and positioning is possible without performing position detection. Furthermore, by switching the current between positive and negative, the direction of movement can also be switched between positive and negative.

By the way, when the thrust generation principle of the actuator of the present invention is examined in detail, the following becomes clear.

The thrust F generated in one stator due to the magnetic flux generated by the permanent magnet and passing through the stator core, that is, the coil linkage flux Φ and the number of coil turns N, is given by dx when the coil current i flows. expressed.

Here, X is the displacement of the mover. Therefore, if the coil flux linkage changes significantly with respect to the displacement X, a large thrust will be generated. In other words, the movable element can be moved with a small current.

Since the actuator of the present invention is combined with a spring so that the boundary of the poles of the permanent magnet is located at the center point of the tip of the stator core when the coil current is zero, the coil interlinkage flux is zero at this position. On the other hand, when considering the rate of change of the coil interlinkage magnetic flux with respect to the position, it becomes the maximum value at this position. this is,
This is because in a range where the change in position is small, the change in magnetic flux can almost be regarded as a sine wave centered on the zero point. therefore,
Since the actuator of the present invention operates near the movable element position where the thrust is large, positioning can be performed with a small current.

〔Example〕

Hereinafter, the present invention will be explained based on one embodiment of FIGS. 1 to 4. FIG. 1 is an external view of a linear actuator according to the present invention, FIG. 2 is a longitudinal sectional view of FIG. 1, and FIG. 3 is a diagram showing the combination of the permanent magnet 2, and FIG. 4 is a diagram showing the assembly of the movable element.

As shown in FIG. 3, the mover consists of a pair of permanent magnets 2 arranged so that the polarities are different, and as shown in FIG. , S, N, and S are connected so that they appear alternately.

The stator has a coil 3 wound around a U-shaped stator core, and the mover is sandwiched between two sets of stators with a gap in between. Further, the stator is a cylindrical case 5 made of a non-magnetic material.
A spring 6 is provided on the upper and lower surfaces of the cylinder of the case 5, and the outer circumferential portion of the spring 6 is connected to the case 5, and the center portion of the spring 6 is connected to the movable element.

This spring 6 is a type of spring called a gimbal spring, and the second
It has spring characteristics with respect to displacement in the direction of the arrow in the figure, and is extremely hard in the direction perpendicular to the arrow, so that the displacement can be suppressed to zero.

Next, the operation of this actuator will be explained.

When the mover is in the state shown in Figure 2, a current is passed through the coil 31 so that the N pole is at the right tip of the upper stator core 11 and the S pole is at the left tip, and the lower stator core 12 so that the S pole is at the right tip and the N pole is at the left tip.
When a current is applied to the stator cores 11 and 12, a driving force is generated by the attractive and repulsive forces between the permanent magnet 2 and the stator cores 11 and 12, and the movable element moves to the left in the figure. On the other hand, the spring 6 is stabilized at the position shown in FIG. 2, and from there a spring force F1 (=- to -x) is generated according to the spring coefficient K in accordance with the left and right displacement X.

The positioning operation will be explained using FIG. 9. FIG. 9 shows the characteristics of the spring Fl and the actuator drive force F with respect to the displacement X.

Since the actuator driving force F is proportional to the coil current i and takes the maximum value at the reference position x=O, it shows a change as shown in the figure. Therefore, the spring force Fz and the actuator driving force F
It settles on the displacement X where and becomes equal. For example, when the coil current is 1==11, it settles at xl in the figure.

8- In this way, since the amount of movement changes depending on the magnitude of the current flowing through the coil, positioning can be performed without particularly requiring a position detection means. In addition, since the movable element is held by a spring,
The spring can also have the function of keeping the gap between the mover and the stator constant, and the structure can be extremely simple.

In this embodiment, a non-magnetic material is sandwiched between the permanent magnets, but the same effect can be obtained even without the use of a non-magnetic material.

FIG. 5 is a longitudinal sectional view of a linear actuator showing a second embodiment of the present invention.

This is applied for the purpose of driving the lens of an optical head of an optical disk device, etc., and the actuator of the present invention is placed on both sides of the lens 100, and the lens is moved in the radial direction (in the direction of the arrow) to perform tracking operation. It is designed to allow the user to perform the following steps.

FIG. 6 is an external view of a linear actuator showing a third embodiment of the present invention.

This is used to drive the lens of the optical head of an optical disk device, etc.
The actuator 20 of the present invention is especially applied for the purpose of focusing operation, and the actuator 20 of the present invention is installed around the lens 100.
0, and the lens is moved up and down (in the direction of the arrow) to perform a focusing operation. The actuator 200 has the same structure as shown in FIGS. 1 and 2, and a hole is made in the case so that the movable element and the lens can be connected, and a connecting beam is extended from the movable element to the end of the lens. There is.

According to the embodiments shown in FIGS. 5 and 6, the lens driving actuator can be made smaller, and the optical head can also be made smaller.

FIG. 7 is a longitudinal sectional view of a linear actuator showing a fourth embodiment of the present invention.

This has a movable element having a cylindrical shape, and stator cores 7.13 are provided on the inside and outside of the movable element, respectively.

The stator core 7 has a disk shape, the stator core 13 has a cylindrical shape, and ring-shaped coils 34 and 33 are disposed on the inner and outer circumferential sides of the stator core 13, respectively.

11 The stator core 7 is fixed to a spacer 51 and an end bracket 52 made of a non-magnetic material, and the stator core 13 is
It is fixed to the case 5 via a coil 33.

The mover has two ring-shaped permanent magnets magnetized in the radial direction.
Each pair is connected with the polarity reversed, and 2
A set of permanent magnets are connected via a ring 4 made of non-magnetic material.

Further, the movable element is held movable in the direction of the arrow in the figure with a small gap maintained between it and the stator core 13.7 by the spring 6.
Similar to the example shown in the figure, the magnitude of the current flowing through the coil,
The amount of movement of the movable element is determined by the direction, and positioning of the movable element can be performed without specifically detecting the position of the movable element.

Furthermore, in this embodiment, since the mover is cylindrical,
The surface area of the permanent magnet can be expanded without waste, and a small actuator with large thrust can be obtained.

FIGS. 8(a) and 8(b) are a vertical sectional view and an external view, respectively, of a linear actuator showing a fifth embodiment of the present invention.

The basic structure is the same as the embodiments of FIGS. 1 and 2.

The difference is that a permanent magnet 22 is newly provided in the center of the spacer 41 made of a non-magnetic material of the movable element, and a gap is formed so as to face the permanent magnet 22 and generate the attractive force of the permanent magnet in the vertical direction. A magnetic body 14 is provided on the lower surface of the coil 31 and the upper surface of the coil 32 via the coil 31 .

According to this structure, the permanent magnet 22 and the magnetic material 1
The movable element stops at a position where the attraction force between the two positions and the driving force of the actuator are balanced. To explain this using FIG. 10, the moving force F2 in the X direction due to the attractive force acting between the permanent magnet 22 and the magnetic material 14 increases until the position where it reaches the point where the force pulling it back toward the origin increases, and just Represents the stakeness characteristics of a spring. Therefore, when a coil current 1=iz is applied, the thrust force F of the actuator and the attractive force of the permanent magnet 22 are balanced by the displacement x1 in the figure, so the movable element of the actuator moves by xl.

In this embodiment, the spring 6 does not need to have spring characteristics in the moving direction of the mover, and only needs to be able to suppress displacement in the direction of the gap and keep the gap constant, which has the effect of making the actuator smaller. .

FIG. 11 is a longitudinal sectional view of a linear actuator showing a sixth embodiment of the present invention.

This is an application of the embodiment shown in FIGS. 1 and 2 to the movement of a magnetic head of a VTR or the like.

The magnetic head 300 is fixed to the movable element 13 by a support member 301, and as the movable element 13 moves, the magnetic head 3
00 moves. In addition, since the entire actuator is covered with the soft magnetic material 25, the magnetic field generated from the coils 31, 32 and the permanent magnet 2 does not have an adverse effect on the magnetic head 300 and the magnetic tape (not shown). Support for the mover of the actuator that moves it.

Even the guide mechanism can be downsized.

Figure 12 shows the figures 1, 2, 5, 7, and 8 above.
It is a front view of the spring 6 used in the figure.

This is called a gimbal spring, and by having a shape as shown in Fig. 12, it has spring characteristics only in the moving direction of the movable element. Spring properties can only be obtained in the penetrating direction).

〔Effect of the invention〕

The present invention is as described above.According to the present invention, positioning can be performed based on the magnitude of current without using a position detector, so that the structure can be simplified and miniaturization can be realized. Further, since the actuator of the present invention is used near the movable element position where the thrust is maximum, there is an effect that positioning can be performed with a small current.

[Brief explanation of drawings]

1 to 4 show an embodiment of the linear actuator according to the present invention, FIG. 1 is an external view thereof, FIG. 2 is a longitudinal sectional view of FIG. 1, and FIG. 3 is a combination of permanent magnets 2. 4 is a configuration diagram of a movable element, FIG. 5 is a vertical cross-sectional view of a linear actuator showing a second embodiment of the present invention, and FIG.
FIG. 7 is a vertical sectional view of a linear actuator showing a fourth embodiment of the present invention, and FIGS. 8(a) and (b) are respectively a fifth embodiment of the present invention. A vertical cross-sectional view and an external view of a linear actuator showing an embodiment, FIG. 9 is a diagram showing the relationship between displacement and force of the linear actuator shown in FIGS. 1 and 2, and FIG.
The figure shows the relationship between displacement and force of the linear actuator shown in FIG. 8, FIG. 11 is a vertical cross-sectional view of the linear actuator showing the sixth embodiment of the present invention, and FIG.
figure. 8 is a front view of the spring 6 used in FIGS. 2, 5, 7, and 8. FIG. DESCRIPTION OF SYMBOLS 1... Stator core, 2... Permanent magnet, 3... Coil, 4... Non-magnetic material spacer, 5... Case, 6...
··Spring.

Claims (1)

[Claims] 1. The movable element has a core in which a permanent magnet is arranged and a stator has a coil, and by passing a current through the coil, a thrust is generated in the movable element to cause the movable element to move in a straight line. In the linear actuator, the movable element is connected to the stator via a spring, and the spring has spring characteristics only in the linear direction of the movable element and has high rigidity in other than the linear direction of the movable element. A linear actuator comprising: 2. Mover permanent magnets having two polarities are opposed to one magnetic pole of the stator core through an air gap, and the position where the polarity boundary line of the permanent magnet and the center of the stator core coincide is set with a spring. The linear actuator according to claim 1, characterized in that the linear actuator is configured to provide a stable point. 3. The linear actuator according to claim 2, wherein the two stator cores on which the coils are disposed have a structure in which the movable element is sandwiched between the two stator cores from both sides with a gap therebetween. 4. A support member is connected to the mover, a magnetic head is disposed at the tip of the support member, and a hole is provided in the case to expose the magnetic head to the outside of the case. The linear actuator according to item 2. 5. The linear actuator according to claim 4, characterized in that the periphery of the linear actuator is covered with a soft magnetic material. 6. The linear actuator according to claim 3, wherein the lens and a movable element are connected to move the lens in a focal direction or a radial direction. 7. The linear actuator according to claim 2, wherein the permanent magnet is a rectangular parallelepiped, and the mover in which the permanent magnet is combined has a flat plate shape.