JPH0233778A - Rotary type actuator - Google Patents

Abstract

PURPOSE:To decrease a positioning error by causing a material to be prescribed for a rotary shaft to rotate many head supporting arms and causing the rotary shaft to be thick and hollow. CONSTITUTION:Many head supporting arms 13 are fit to a rotary shaft 12 by a spacer 14 and a clamp 15, etc., and the rotary shaft 12 is fit rotably to a housing 6 by bearings 10 and 11. Then, the rotary shaft 12 is formed by the same type material, whose thermal expansion coefficient is almost equal with that of the housing 6, and a central part is made thick and hollow so that one part can be made vacant. Since the necessary use material is used without providing a fixed shaft to go through this shaft 12, thermal expansion difference is not generated between the shaft 12 and housing 6 and mechanical strength is secured by the thick and hollow shape. Then, the positioning error of a head is reduced and positioning accuracy is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rotary actuator, and particularly to a rotary actuator in which the rotary shaft is made of the same metal as the housing without passing through a support shaft made of a different metal at the center of the rotary shaft. This invention relates to a rotary actuator that can prevent displacement of the actuator due to thermal displacement.

[Conventional technology]

Conventional magnetic disk devices include, for example, Japanese Patent Application Laid-open No. 60-18
As described in Japanese Patent No. 2077, a rotating shaft for rotating an arm to which a plurality of heads are attached, and a fixed shaft k for penetrating and fixing the rotating shaft are each made of different materials.

FIG. 4 is a sectional view of a main part of the conventional magnetic disk device disclosed in the above publication.

As shown in FIG. 4, in the conventional magnetic disk drive, a plurality of ams 13 rotating around the rotating shaft 12 are attached to the rotating shaft 1-2 attached to the housing 6 with a spacer 1.
It is attached via 7.

This rotary shaft 12 is penetrated by a fixed shaft 43 fixed to the housing 6 with a screw 20, and between the fixed shaft 43 and the rotary shaft 12 are bearings 4.1. , 4.2 and a preload spring 16 are attached, and a clamp 15 is provided on the rotating shaft 12. Although not shown, a magnetic head is mounted on the tip of the arm J3.

In this way, the actuator includes a rotating shaft 12 on which a magnetic head is mounted and a bearing 41 that rotates the rotating shaft 12.
．． 42, and a fixed shaft 43 that supports these bearings 41 and 42.

A fixed shaft 43 is passed through the rotating shaft] 2,
The fixed shaft 43 is made of a material different from that of the rotating shaft 12 (stainless steel → thermal expansion coefficient 17.3 x
10-'/°C). That is, the rotating shaft 1
2 swings and rotates at high speed, so it is necessary to reduce the moment of inertia 1-, and therefore a lightweight aluminum alloy is used (coefficient of thermal expansion 24.3 x 10-'/°C). In addition, the main body of the magnetic disk drive is mainly made of aluminum alloy, and if there is unevenness in the coefficient of thermal expansion, off-I
・Since it causes racking, the purpose is also to equalize the coefficient of thermal expansion.

In this way, the fixed shaft 43 is made of a material different from that of the magnetic disk disk 13, which is a rotating recording body, and the housing 6, which fixes the actuator.

[Problem to be solved by the invention]

In this way, in conventional rotary actuators,
Only the strength of the materials of the fixed shaft 43 and the rotating shaft 12 is considered, and the difference in axial thermal expansion between the fixed shaft 43 and the rotating shaft 12,
Also, little consideration was given to the difference in thermal expansion between the fixed shaft 43 and the housing 6. Fixed shaft 43 and rotating shaft] 2
Since the materials of the fixed shaft 43 and the housing 6 are different, a difference in thermal expansion occurs when the temperature changes, and as a result, a slight relative displacement occurs between the magnetic heads attached to the rotating shaft 12, and the positioning There was a problem that errors occurred. The first challenge is to eliminate positioning errors caused by this difference in thermal expansion.

In addition, since the fixed shaft 43 passes through the rotating shaft 12,
Its shape is a thin-walled pipe. Therefore, in order to maintain mechanical strength, the fixed shaft 43 must also be made smaller in diameter to ensure the thickness of the rotating shaft 12.

It is necessary to maintain compatibility in the external dimensions of magnetic disk drives, and the magnetic disks themselves are also being standardized. Therefore, due to both constraints, the external dimensions (rotary shaft diameter) of the rotary actuator that is close to the magnetic disk are restricted. For this reason, when the diameter of the fixed shaft is increased, the rotating shaft 12 becomes thinner and its rigidity decreases.

Therefore, reducing the diameter of the fixed shaft 43 will reduce the mechanical strength of the actuator, which may cause deformation when an external force is applied or a decrease in the natural frequency. There is a problem in that the positioning error increases. The second problem is to eliminate positioning errors caused by this decrease in mechanical strength.

An object of the present invention is to solve these problems and provide a rotary actuator that can eliminate positioning errors due to differences in thermal expansion and positioning errors due to a decrease in mechanical strength.

[Means to solve the problem]

In order to achieve the above object, the rotary actuator of the present invention includes a rotary shaft that rotates an arm on which a magnetic head is mounted, a bearing that supports the shaft end of the rotary shaft, and a housing that holds the rotary shaft by the bearing. In the rotary actuator, the rotary shaft is not provided with a fixed shaft passing through the rotary shaft, but a center portion of the rotary shaft is partially hollow, and the rotary shaft is made of the same material having a coefficient of thermal expansion approximately equal to that of the housing. It is characterized by its thick structure.

[For production]

In the present invention, the fixed shaft passing through the rotating shaft is removed to prevent a difference in thermal expansion from occurring, and the rotating shaft of the actuator is made of the same material as the housing, and the rotating shaft is made of a member made of the same material. By supporting the rotary shaft with a fixed shaft and removing the fixed shaft, the rotating shaft can be thickened to improve its mechanical strength.

As described above, the rotary actuator of the present invention has the rotary shaft and the housing that supports it made of the same material, and does not have a fixed shaft made of a different material that passes between the bearings disposed at both shaft ends. The thermal displacement in the axial direction can be made almost equal between the rotation axis and the housing, and as a result, it is possible to eliminate distortion of the actuator rotation axis due to thermal displacement. Furthermore, since the rotating shaft can be a solid shaft, the mechanical strength of the actuator section including the rotating shaft can be improved, thereby eliminating positioning errors.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a main part of a rotary actuator showing an embodiment of the present invention, FIG. 2 is an exploded perspective view of the rotating shaft in FIGS. FIG. 2 is an exploded perspective view of the soto disk assembly.

As shown in FIG. 3, a head disk assembly (hereinafter abbreviated as HDA) which is the drive unit of a magnetic disk device
, a plurality of recording disks (magnetic disks) 1 are stacked,
The spindle parts 1 to 3 have built-in rotation motors 2, the rotatable actuator parts 5 are laminated and arranged to face the magnetic belly buttons 1 to 4 and the surfaces of the climbing board 1, and these spindle parts. 3 and an actuator section 5, and a sealing cover 7 for sealing one side of the housing 6. Note that the actuator section 5
The rotating shaft is rotated by the magnetic screw 1 to 8 and the coil 9.

A cross section of the actuator section 5 is shown in FIG. The sectional view of the rotary actuator shown in FIG. 1 differs from the conventional structure shown in FIG. 4 in that there is no fixed shaft within the rotating shaft 12. As shown in Figure 1, the rotation axis 1
The center portion of the rotating shaft 12 is hollow, and one end of the rotating shaft 12 protrudes and is fitted inside the bearing 10, and the outer ring of the bearing 11 is fixed to the other end. That is, in this embodiment, in order to lower the inertia of the rotating shaft 12, the hollowing is performed to the extent necessary to maintain the minimum necessary rigidity.

The arm 3 that supports the magnetic head 4 has a hole that fits into the outer diameter of the rotating shaft 12, and the spacer 14 inserted between the arms 13 and the plurality of arms 13 are connected to the rotating shaft 12. is fixed with a clamp 15. Further, between the rotating shaft 12 and the bearing 1o, an axial preload spring 16 and a spacer 17 are provided.
will be provided.

Further, a holder 18 for fixing the outer ring of the bearing 10,
Furthermore, it is built in the holder 18, and one end is attached to the holder 18.
A spiral spring 19 is provided whose other end engages with the tip of the rotating shaft 12, respectively.

Note that the coil portion 9 shown in FIG. 3 is attached to one of the spacers 14 shown in FIG. 1. Further, the actuator section 5 is attached to the housing 6 by screws 20 and pivots 1 to 21.
It is fixed at That is, in the actuator section 5, the holder 18 is fixed to the housing 6 by the screw 20, and the pivot 21 having a protrusion to be inserted into the inner ring of the bearing 11 at the other end of the rotating shaft 12 is inserted into the hole provided in the housing 6. is fitted and fixed. At this time, a seal 22 is provided at the fitting portion between the pivot 21 and the housing 6 to maintain airtightness, and a seal 23 is also provided around the fixing screw 20 of one of the holders 18.

With these, friction between the rotating shaft 12 side and the housing 6 side can be reduced. The material of the bearing is high carbon chrome steel (coefficient of thermal expansion is 12.5X10-6), and the material of the pivot is aluminum alloy (coefficient of thermal expansion is 24.3).
X] O-6/°C).

As shown in FIG. 2, the protruding tip of the rotating shaft 12 and the protrusion of the pivot 21 have a cross section in which a part of a circle is cut out, and a small hole is provided in the direction perpendicular to the axis. A round pin 31, a spring 32, and an E-ring 33 for engaging the pin 31 and holding it on the rotating shaft 12 are arranged. The rotating shaft 12 is coupled to the housing 6 by these.

Further, as shown in FIG. 1, the rotating shaft 12 and the housing 6
The shim 24 adjusts the relative position of the bearing 11 and the pivot 1.
It is inserted between -21.

The rotating shaft 12 of the actuator section 5 is supported by bearings 10.degree. 11, and is rotated in the radial direction of the disk 1 by a magnet 8 and a coil 9 that constitute the voice coil motor shown in FIG. Perform positioning.

As described above, in this embodiment, (a) the bearings 10 disposed at both ends of the rotating shaft 12 of the rotary actuator 5;
Since there is no fixed shaft passing through the housing 6, the rotating shaft] 2, the arm 13, the spacer 14, the clamp 15, the holder 18, and the pivot 21 can be made of the same material as the housing 6. Therefore, since these parts and the housing 6 are made of materials with coefficients of thermal expansion that are the same or similar, even when the HD A expands or contracts due to fluctuations in ambient temperature, the amount of heat applied to the actuator section 5 will be reduced. Distortion is extremely low. Further, the rotating shaft 12, the bearing 10, and the pivot 21 are each made of different materials, and the rotating shaft 12, the bearing 10, and the pivot 1- are in contact with these different materials.
21 and the bearing 11, as shown in FIG. 2, there is no gap between the pin 31 and the spring 32, so there is no error between the axes of the shaft ends that would affect the positioning accuracy of the magnetic spatula l'4. does not survive. (b) Also, since the rotating shaft 12 does not require a fixed shaft, the rotating shaft 12 becomes thinner due to the fixed shaft.
F Mechanical strength does not decrease, and the mechanical strength can be improved by increasing the thickness, so positioning errors caused by strength can be minimized.

〔Effect of the invention〕

As explained above, according to the present invention, displacement between magnetic heads due to temperature fluctuations is eliminated, so positioning accuracy can be improved and the mechanical strength of the rotating shaft can be improved.
2 can be performed, positioning errors caused by strength can also be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a rotary actuator showing an embodiment of the present invention, FIG. 2 is an exploded perspective view of the rotating shaft in FIG.
FIG. 3 is an exploded perspective view of an I-I DA to which the present invention is applied, and FIG. 4 is a sectional view of a conventional rotary actuator. 1: Recording disk, 2: Motor, 3 Varnish binder section, 4: Magnetic head, 5: Actuator, 6: Housing, 7:
Cover, 8: Magnet, 9: Coil, "0, 1F,"
41, 42: Bearing, 12: Rotating shaft, 13: Arm, 15
: Clamp, 16 two preload springs, ]7: Spacer, 18:
Holder, 19: spiral spring, 20: screw, 2]: pivot to 1, 22° 23: seal, 31: pin, 32: spring, 33° 34: ring, 43: fixed shaft. Diagram

Claims (1)

[Claims] 1. A rotating shaft that rotates an arm equipped with a magnetic head,
In a rotary actuator that includes a bearing that supports the shaft end of the rotary shaft and a housing that holds the rotary shaft by the bearing, the central part of the rotary shaft is fixed without providing a fixed shaft passing through the rotary shaft. 1. A rotary actuator characterized in that the rotating shaft is made of a similar material having substantially the same thermal expansion coefficient as the housing, and has a thick wall.