JPH0448475A - Linear actuator for head positioning mechanism for magnetic disk drives - Google Patents

Abstract

PURPOSE:To accurately position a head by arranging a reference face where a rail is mounted in a support and the traveling face of the rail on a same plane. CONSTITUTION:When ambient temperature rises, since rails 12 and 13 consist of ceramics, the coefficient of thermal expansion of them is small compared with that of other members 14, 15 to 17, 20, and the like which consist of aluminum alloy. When the rails 12 and 13 are thermal-expanded, they become relatively small to the other members as indicate with broken lines. However, traveling faces 21 and 22 of the rails 12 and 13 are on the same plane as the faces 21 and 22 where they are mounted to supports 10 and 11 and the position of them does not change. Thus, a carriage 14 does not change its position, the positional relation between a head and a magnetic disk does not change and the positioning of the head can be executed with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application] The present invention relates to a head positioning mechanism of a magnetic disk drive, and more specifically to an improvement of a linear actuator in the head positioning mechanism.

[Prior Art] This type of linear actuator is widely used because displacement of the head in directions other than the access direction is restricted and good positioning accuracy can be obtained.

For example, the linear actuator itself is
As described in Publication No. 877 and Japanese Patent Application Laid-open No. 196475/1987, a support is placed between the rails arranged in parallel, the support to which the rails are fixed, and the rails,
The head assembly is equipped with a carriage that holds the head assembly, and the head is moved in a straight line by moving the carriage while rolling rollers on the carriage along the running surface on the rail.

[Problems to be Solved by the Invention] The members constituting the linear actuator usually use aluminum alloys of different purity for the substrate members of magnetic disks, so it is difficult to use aluminum alloys that are possible. There is. This is because changes in ambient temperature were taken into account. If members with different coefficients of linear expansion are used together, each member will undergo elastic deformation due to thermal strain or stress when the ambient temperature changes, which will affect the positioning accuracy of the head. Therefore, we want to avoid this as much as possible. However, the rails that guide the carriage must have sufficient wear resistance, so materials harder than aluminum alloys, such as hardened steel or ceramic class, are used.

These rail materials have smaller thermal expansion than aluminum alloys, so when the ambient temperature rises, a minute gap on the order of several microns is created at the contact portion between the rail running surface and the rollers. When a gap occurs, the carriage rolls on the rail to fill the gap and changes its posture, which makes it difficult to position the head supported by the carriage at the desired position on the magnetic disk when the recording density is high. become unable to do so.

An object of the present invention is to provide an improved linear actuator that allows highly accurate head positioning even when the temperature changes.

[Means for Solving the Problems] In order to achieve the above object, the linear actuator of the head positioning mechanism for a magnetic disk of the present invention has a structure in which the running surface of the rail is located on the same plane as the reference surface on which the rail is installed in the support. It is configured as follows.

[Function] When the temperature rises, the size of the gap that occurs between the rail and the rollers is proportional to the distance between the rail installation reference surface on the support and the roller running surface. It is proportional to the change in temperature, or in other words, it is determined by how thick the rail is. Even if the temperature rises or falls, if the actual thickness of the guide rail is zero, the thermal strain caused by the difference in the material of the guide rail is zero, and no change in the posture of the carriage occurs.

In the head positioning mechanism according to the present invention, as described above,
The running surface of the rollers on the rail and the installation reference plane of the rail on the support are arranged in the same plane, the thickness of the rail is made to be substantially zero, and all rollers are forced to run on such a running surface. Therefore, even if the temperature changes, the posture of the carriage does not change.

[Examples] Examples of the linear actuator of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, reference numerals 10 and 11 indicate supports, 12 and 13 indicate rails installed on each of the supports, and 14 indicates a carriage that runs on these rails, respectively.

The support 10.11 consists of a block 15.16 and a bridge 17, respectively. Block 15.1
6 is a hollow channel-shaped member made of aluminum alloy, and wall surfaces 18 and 19 forming the groove bottom are arranged in a V-shape at an angle of 90°. These wall surfaces 18 and 19 serve as reference surfaces for attaching the rails to the aluminum alloy base so that the actuator forms an angle of 45° with respect to the recording surface of the magnetic disk that together constitute the magnetic disk device. It is fixed at 20. The bridge 23 is also made of aluminum alloy and blocks 21.2
2 and connected to the blocks 15, 16 and the base 20, respectively.

The rails 12.13 are made of hardened steel, for example.

As best shown in FIG. 2, the rail itself has a hexagonal cross section, with two side surfaces 21 and 22 serving as running surfaces. These running surfaces are arranged at right angles to each other. These rails are connected to the bridge 15.16 with the running surface 21.22 in contact with the installation reference surface 18.19.
It is fixed to the support by passing through the block and screwing a bolt 24 into the rail. For this reason, the rail running surface 2
1.22 is the block installation reference plane 18.1, respectively.
It is in the same plane as 9.

The carriage 14 has a head for recording/reproduction and a head assembly (not shown) having a mechanism for floating the head attached to the front side, and rollers 25 to 25 to the side.
It is equipped with 32. A set of four rollers is installed, one set at the front and one at the rear. Although only six of these rollers 25 to 30 are shown in the drawing, rollers 31 and 32 forming a pair with rollers 29 and 30 are arranged behind roller 27 and behind roller 32, respectively. There is. The rollers of each set are arranged at right angles to each other, as best seen in FIG. Roller 25 is spaced 90' apart from roller 28, roller 26 from roller 27, roller 29 from roller 32 located below the carriage, and roller 30 from roller 31 located below the carriage. They are arranged at an angle of 90° from each other. The roller itself consists, for example, of a rolling bearing, the inner ring of which is engaged with a shaft in the carriage and is prevented from being pulled out. For assembly to the rail, the rollers 25 and 29 are placed on the running surface 21 of the rail 12.
The roller 28 and the roller 32 behind this roller are connected to the running surface 22 of the rail 12, the rollers 26, 30 are connected to the running surface 21 of the rail 13, and the roller 27 and the roller 31 behind this roller are connected to the running surface of the rail 13. 22 and are placed between the rails 12 and 13, and these rollers roll on the running surfaces of the respective rails, thereby making it possible to travel in a straight line. .

The carriage 14 is moved by, for example, a voice coil motor. The voice coil is attached to a shaft 3 extending from the back of the carriage, indicated by a chain line in FIG.
It is supported by 3.

In such a head positioning mechanism, when the ambient temperature rises, since the rail 12.13 is made of ceramic class, the other member 14.1 made of aluminum alloy
The coefficient of thermal expansion is smaller than that of 5 to 17.20. When thermally expanded, the rails 12.13 become smaller relative to the other members, as shown by the dashed lines in FIG. However, the running surface 21.22 of the rail 12.13 is the support 10.
It is in the same plane as the plane 21, 22 which is located relative to the angle 11 and does not change its position. For this reason, carriage 1
No. 4 does not change its posture, and the positional relationship between the head and the magnetic disk does not change, and the head can be positioned with high precision.

FIG. 3 shows another embodiment of the linear actuator of the present invention.

In this linear actuator, the support includes a block and a bridge, and has a structure in which the blocks are integrally formed. In Figure 3,
Only blocks 115 in one of these supports are shown.

The block 115 consists of a closed cross-section member, and two sets of installation reference surfaces 118, 119 are provided on the wall surface forming the internal space. Among these wall surfaces, the wall surfaces 118 and 119 of the - group are arranged at right angles to each other, and the wall surfaces 118 and 119 of the other group are also arranged at right angles to each other.

This block is fixed to the base 120 together with another block placed at a distance behind the plane of the drawing, and is tightly connected by a bridge placed between them. has been done. Also at this time, the block 115 is connected to the wall surface 118.11.
9 is arranged on the base 120 so as to form an angle of 45° with respect to the recording surface of the magnetic disk.

The rail consists of four. Each of the rails is designated by reference numerals 112.112a, 113.113a. These rails are approximately triangular in cross section, with the slopes of the rails 112, 113 forming the running surface 121 and the rail 112a.

The slope at 113a forms a running surface 122.

Assembling to the support involves inserting these rails into the internal spaces of block 115 and another block, as well as inserting the running surfaces 121 on rails 112 and 113.
A part of the rail 112 is attached to the installation reference surface 118 of the support.
a, a part of the running surface 122 at 113a is installed on the installation reference surface 1
19 respectively, pass through the block, pass through the block 115, and screw the port 124 into the rail.

A roller is attached to the carriage 114. The rollers are arranged as a set of four rollers 125 to 128, one set each at the front and rear of the carriage. The four rollers forming each set are arranged at right angles to each other. The roller eye body is made of, for example, a rolling bearing, and is constructed by holding an inner ring on a fixed shaft on a carriage. For assembly, use carriage 114
are arranged between the rails 112.112a and 113.113a, and the roller 125 and the roller behind this roller are placed on the running surface 121 of the rail 112, and the roller 126 and the roller behind this roller are placed on the rail 1.
The roller 127 and the roller behind this roller are placed on the running surface 121 of the rail 113a, and the roller 127 and the roller behind this roller are placed on the running surface 122 of the rail 113a.
This is accomplished by bringing the roller 128 and a roller behind this roller into contact with the running surface 122 of the rail 112a.

In this linear actuator, the block 115 and bridge constituting the support are also made of aluminum alloy, and the rail is made of hardened steel.
, 113, 113a are on the same plane as the installation reference planes 118, 11'9 of Pro and Tsuk, respectively. Therefore, even if the temperature rises, the running surface 121.1
22 does not change, and the carriage 114 does not change its posture.

FIG. 4 shows a travel unit in yet another embodiment of the linear actuator.

In this actuator, the support 200 is
Like the embodiment shown in the figures, it has a block and a bridge, but the blocks on both sides are integrally formed. Only one block 215 is shown in the drawing,
This block is attached to the base 12 along with another block placed at a distance behind the plane of the drawing.
0 and are coupled by a bridge placed between them.

The block 215 is made of aluminum alloy.
A reference surface 21 having a letter-shaped form and on which the rail is installed.
8 is provided on a wall surface forming one side of the L-shape, and a reference surface 219 is provided on a wall surface forming the other side. The installation reference planes 218 and 219 are arranged on the block 215 so that they form an angle of 45° with respect to the recording surface of the magnetic disk when this linear actuator is configured into a magnetic disk device.

The rails 212, 213 have a substantially rectangular cross-sectional shape and have running surfaces 221, 222 adjacent to each other and separated by an angle of 90 degrees. Installation on the support is performed by placing only the running surface 221 in contact with the installation reference surface 218, placing it between the blocks 215, and bolts 12 that pass through the blocks and are screwed into these.
4 by fixing it to the block.

Similarly to the carriages in other embodiments, the carriage 214 is also provided with four sets 225 to 228, one set each in the front and back direction of the paper. To assemble the roller 225 and the roller behind it to the rail 21
The roller 226 and the roller behind it are placed on the running surface 221 of the rail 213, and the roller 226 is placed on the running surface 221 of the rail 213.
27 and the roller behind it contact the running surface 222 of the rail 213, and the roller 226 and the roller behind it contact the running surface 222 of the rail 212, and the carriage 214 is placed between the rails 212 and 213. It is done by

However, among these rollers, the roller 226 and the roller disposed behind this roller are connected to the carriage 22
4 and is supported by a leaf spring 236 and attached to a member 237. The leaf springs apply a preload to the carriage 224 due to their elastic force, and the rollers and the running surfaces 221. of the rails 212.213.
It is made to be pressed with a constant preload of 222.

In this linear actuator, the block 215 is made of aluminum alloy, and the rails 212 and 213 are made of hardened steel, and their linear expansion coefficients are different from each other.

As the temperature increases, the thermal expansion of the pro-nk 215 becomes relatively greater than that of the rail 212.213, e.g.
Thermal deformation of No. 13 is reduced. At this time, the positions of the running surfaces 221 and 222 of the rails do not change because they are in the same plane as the reference installation surface 218 of the block 215.

However, the running surface 221 of the rail 212 has a gap δ between the roller 227 and the roller placed behind it, and the running surface 221 of the rail 213 has a gap δ between the roller 227 and the roller placed behind it. Gap δ
will occur.

However, since the roller 226 and the roller placed behind it are supported by the leaf spring 236, the repulsive force of the leaf spring causes the entire carriage to move in parallel in the direction shown by the arrow 238 in FIG. Contact is maintained with each of the running surfaces 222, 221 of rail 212 and rail 213. At the same time, the roller 225 and the roller behind it are moved to the running surface 225 of the rail 212.
21, the roller 227 and the roller behind it move along the running surface 221 of the rail 213 with a gap δ.
, and their contact is also maintained. Therefore, the carriage 124 does not roll even if the environmental temperature changes.

In the linear actuator explained above, whether the running surface of the rail and the installation reference surface of the block are in direct contact,
A member made of a material with the same coefficient of linear expansion as the roller is placed between the running surface and the installation reference surface, so that even if the ambient temperature changes and the roller thermally expands, the member will thermally expand by the same amount. In addition, it is possible to minimize the rolling of the carriage by preventing gaps between the rollers and the rails, and to bring the running surface on the rail into direct contact with the rail installation reference surface on the support. Although they are arranged on the same plane, changes and improvements can be made within the scope of the present invention, such as arranging them separately within the same plane.

[Effects of the Invention] The linear actuator of the head positioning mechanism for a magnetic disk drive of the present invention does not cause the carriage to roll even when the temperature changes, so it is possible to position the heads with mutual precision, and to improve the recording density. Improvements can be made.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing the overall configuration of an embodiment of a linear actuator for a head positioning mechanism according to the present invention, and FIG. 2 is a front view thereof. FIG. 3 is a front view showing another embodiment of the linear actuator of the present invention, and FIG. 4 is a front view showing still another embodiment of the linear actuator of the present invention. 10, 100.200...Support

Claims (1)

[Claims] 1. A support, a rail disposed parallel to the support, and a carriage that runs on the rail and supports a head assembly, and the rollers on the carriage are connected to each of the running surfaces on the rail. In a linear actuator for a head positioning mechanism for a magnetic disk device, which moves the head in a straight line by moving the carriage while rolling along the rail, the reference surface on which the rail is installed on the support and the running surface of the rail are on the same plane. A linear actuator for a head positioning mechanism for a magnetic disk device, characterized in that the linear actuator is arranged in a head positioning mechanism for a magnetic disk device. 2. The linear actuator according to claim 1, wherein all reference surfaces on which the rails are installed in the support and all running surfaces of the rails are arranged on the same plane. 3. Each of the installation reference planes in the support forms an angle of 45° with respect to the recording surface of the magnetic disk that together with this linear actuator constitutes a magnetic disk device;
3. The linear actuator according to claim 2, wherein the running surfaces of the rails are respectively arranged at an angle of 45 degrees with respect to the recording surface and are brought into direct contact with each other. 4. A part of the running surface of the rail is placed in direct contact with the reference surface on which the rail is installed in the support, and the carriage is arranged so that the roller rolls on this running surface on one part and on the other running surface on the remaining part. A linear actuator according to claim 3 located above.