JPS6292756A - Linear actuator - Google Patents

Abstract

PURPOSE:To miniaturize a device and lighten the weight and enhance the rigidity and reduce the frictional action, by providing the first and second moving guide members of a linear actuator, with the first and second bearings fixed respectively and with a pressure-applying means. CONSTITUTION:A linear actuator is formed with the first moving guide member 10 of almost round cross-sectional area, the second moving guide member 11 set in parallel with the member 10 at a distance a, a cage unit 12, and the like. Besides, the actuator is provided with a moving member 20 moved and guided by the both members 10, 11, the bearing member 21 of a magnetic head, a coil 22 set on the moving member 20, yokes 30-31, and a permanent magnet 32. Then, the first bearing 40 butted to the moving guide member 10 at a distance b and fixed on the moving member 20, the second bearing 41 fixed on the moving member 20 butted by the moving guide member 11, and a plate spring 16 fixed on the moving guide member 11 with a screw 17 are arranged, and a force is generated by the plate spring 16 in the direction of an arrow head A. When the both members 10, 11 are deflected, then a compressive force applied to the moving member 20 is varied, and the members are driven with a reduced force.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is based on v! The present invention specifically describes several vibration characteristics of a linear actuator used for driving a magnetic head in a magnetic disk drive.

(Prior Art) A linear actuator is capable of obtaining direct linear motion without the use of a one-turn linear conversion mechanism, and is described in, for example, Electronic Communication Handbook (1979) P, 419.

FIG. 7 shows a schematic diagram of a magnetic disk device using such a linear actuator. In the figure, 50 is a spindle motor, 51 is a spindle motor 5
A plurality of disks are fixed at a predetermined distance d from each other on the main axis of 0. Among these disks 51, for example, 51h
Position information is written on one side, and necessary information is recorded on the other sides. 52 is a carriage movable in the direction of the arrow, 53 is a linear voice coil motor that drives the carriage 52, 54 is a head support plate fixed to the carriage 52 (C), and 55 is a recording head that reads information recorded on the disk surface. , 56 are leaf springs that press the recording head 55 against the disk 51, and the distance from the head support plate 54 to the disk 51 is IK.

In such an apparatus, in order to read the positional information of the disk 51h and move the recording head 55 to a predetermined position, the carriage 52 is moved in the direction of the arrow and the spindle motor 50 is rotated.

(Problems to be Solved by the Invention) However, according to the device having such a configuration, since the disk 51 and the linear voice coil motor 53 are arranged in a straight line via the carriage 52, the linear voice coil motor 53 is The device is longer.

Therefore, if a linear actuator with this configuration is used in a large 14-inch or 8-inch magnetic disk device, or if the linear actuator shown in Figure 7 is used in a small-sized 3-inch magnetic disk device, the advantage of miniaturization will be lost. There were some issues that were raised.

In fixed magnetic disk drives, the track density is 100
0 Tpi (Traek per 1nch), the positioning accuracy must be within ±0.51 Jm, and in order to set the average access time to 20 m5ec, K is the natural frequency of the linear actuator of 2 k.
It needs to be higher than Hz. A linear actuator that achieves these characteristics has a fixed member, a movable guide member that supports the movable member, and a low coefficient of friction between the movable member and the movable guide member. is required.

The present invention solves these problems and aims to realize a small, lightweight, high-rigidity, low-friction IJ near actuator.

(Means for Solving the Problems) The present invention achieves such an object by providing a predetermined interval (1)
first and second movement guide members installed in parallel with each other, and a movement member that moves while being guided by these movement guide members;
A hollow coil fixed to the movable member, and a yoke loosely inserted into the hollow portion of the coil and installed following the movable guide member.

In this linear actuator, the yoke is provided with a magnetic field generating means for generating a magnetic field, and the first movement guide member is in contact with the first movement guide member at least at a distance (b) smaller than the distance (1), and is fixed to the movement member. a second bearing that contacts and is fixed to the movement guide member, and a second bearing that is fixed to at least one of the first or second movement guide member and is fixed to the movement guide member; The present invention is characterized by further comprising a pressing means for applying force in a direction to narrow the distance (1).

(Example) The present invention will be explained below using the drawings.

FIG. 1 is a perspective view of the configuration of an embodiment of the present invention, with the magnetic head removed. 2 is a cross-sectional view of a portion of the apparatus of FIG. 1; FIG.

In the figure, lO is a first movement guide member having a substantially circular cross section;
Reference numeral 11 denotes a second movement guide member having a substantially circular cross section and provided in parallel with the movement guide member IO at a distance a.

12 is a housing that accommodates the linear actuator; 13 is a first boss that is fixed to the housing 12 and supports the movement guide member 10; and 14 is fixed to the housing 12 and supports the movement guide member 11. The second boss, 15, is boss 13.
A seat for fixing the movement guide member 10.11 to the movement guide member 10.14, which is provided at both ends of the movement guide member 10.11, and for example, a V block is used. , 16 are leaf springs fixed to the second movement guide member 11 via screws 17, which exert a force in the direction of narrowing the distance a (in the direction of the arrow).

Reference numeral 20 indicates a moving member that moves while being guided by the moving guide members 10 and 11. Reference numeral 21 indicates a head support member on which a magnetic head (not shown) is mounted. It is. , 22 is a coil provided on the moving member, and the inside is hollow.

30 is an E-shaped yoke made of a material with high magnetic permeability.
A member provided parallel to the central housing 12 is loosely inserted into the hollow portion of the coil 22 and is parallel to the movement guide member 10.11. Reference numeral 31 is an I-shaped yoke that pairs with the yoke 30, and 32 permanent six stones that generate a magnetic field in the yoke 30 and 31.

40 is a moving guide f! AU'lOK spacing (the first bearing that contacts at bl and is fixed to the moving member 20, one bearing is two bearings that contact the moving guide member 10 at an angle of 90 degrees in the same plane) This spacing is smaller than the spacing a. Reference numeral 41 designates a second bearing fixed to the movable member 20 that abuts on the movable guide member 11; Therefore, the total number of bearings 40°41 is 6 traps.

The operation of the device configured in this way will be explained. FIG. 3 shows the relationship between the rigidity of the moving member 10.11 and the moving guide member 20.

In the figure, a indicates the interval between the movement guide members 10.11, b indicates the interval between the bearings 400, and r indicates the ratio of a to b.

FIG. 4 is a diagram showing the mechanical relationship of the device shown in FIG. 1.

In the figure, denotes a spring constant for bending the movable guide member 10°11 in the direction of arrow A, and M denotes the mass of the movable member 20. In such a dynamical system, the natural frequency f
is expressed by the following formula.

Figure 3 shows this relationship, with the vertical axis representing the natural frequency f (Hz).

The ratio r is plotted on the horizontal axis. For convenience of calculation, M = 30 [g], K-2 (kgf/rrm
), and a is 20.30.40.50 (mm).

Since the natural frequency f decreases as the ratio r increases, the natural frequency f inevitably tends to become smaller in small magnetic disks where it is desirable to reduce the spacing. If the spacing a is made smaller, the natural frequency f becomes larger, but there is a limit to this due to the mounting of the magnetic head and the dimensions of the yoke. Therefore, keep the natural frequency high while keeping the ratio r greater than 1 (e.g. f = 2000 Hz)
In order to achieve this, it is expected that the spring constant K needs to be increased.

By reinforcing the plate spring 16, the spring constant can be increased compared to the rigidity of the movement guide member alone.

FIG. 5 is a cross-sectional view showing another embodiment of the present invention.
A) shows a plan view, and (b) shows a front view. In the figure, the ends of the movement guide members 10.11 are processed into a quadrilateral shape and are screwed to bosses 18 fixed to the housing 12. The boss K of the movement guide member 11 is provided with a load spring 19 for increasing the spring constant.

The diameter of the movement guide member 10.11 is 12nTnφ, and the interval t between the bosses 18 is 60 mm 1 The interval is 30 r
If rrn, then 1.

The stroke of the moving member 20 is 30 mm, which is 57
1n+ fixed disk recording m 1 in (= 25
rrm), and the spring constant is 16 Ckgf/irm without using the load spring 19.
) high rigidity can be obtained.

FIG. 6 shows the magnitude of preload F [kgf) per bearing of the load spring 19 and the movement guide member 10.
．． 11 and bearings 40 and 41. The relationship between the coefficient of friction μ between bearings 40 and 41 is shown. As the preload force F increases, the friction coefficient μ increases.

Therefore, if the bending rigidity of the inside of the movement guide section 10.11 is increased, the preload force of the load spring 19 may be reduced, and in this case, the friction coefficient μ is 1. It becomes a small value of OX 10-'. Furthermore, when the movable guide member 10.11 is bent due to bending, the compressive force applied to the movable member 20 changes, so the friction coefficient μ changes depending on the position of the movable member 2θ, but if the preload force P is small, this The change in friction coefficient μ is also small. When the friction coefficient μ is small, the moving member 20 can be driven with a small force, and the positioning accuracy is high.

(Effect of the invention) As explained above, the present invention has the following effects.

(1) Since a preload force P is applied to the movement guide member by the leaf spring 16 and the load spring 19, the natural frequency f
is high.

(b) The spacing is smaller than the spacing 3 (r≧
1), the length of the moving member 20 can be shortened, and the device can be downsized.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the configuration of an embodiment of the present invention, FIG. 2 is a cross-sectional view of a portion of the device shown in FIG. 1, and FIG. 3 is an explanatory diagram of a mechanical model of the device shown in FIG. 1. , FIG. 5 is a sectional view showing another embodiment of the present invention. Is the preload force in Figure 6? FIG. 7 is a schematic diagram of a conventional device. 10, 11... Movement guide member, 16. 19... Pressing means, 20... Moving member, 22... Coil, 30.
31... Yoke, 32... Magnetism generating means, 40.4
1...Bearing. Fig. 6 Preload force per 14 m of bearing F [kg +] Fig. 7

Claims (1)

[Claims] (1) A first and second movement guide member installed in parallel at a predetermined interval (1), a movement member that moves while being guided by these movement guide members, and a hollow member fixed to this movement member. A linear actuator comprising a coil, a yoke that is loosely inserted into a hollow part of the coil and installed following the movement guide member, and a magnetism generating means that generates a magnetic field in the yoke, wherein the first movement guide member a first bearing that abuts at least an interval (b) smaller than the interval (a) and is fixed to the moving member; a second bearing that abuts the second moving member and is fixed to the movement guide member; and a pressing means fixed to at least one of the first or second movement guide member and applying force to the movement guide member in a direction to narrow the distance (a). linear actuator.