JPS636937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to magnetic disk drives;
In particular, it relates to a linear actuator for moving a pick up head of a disk drive.

A disk with a magnetic coating on its surface provides a memory for data bits, which can be randomly accessed at high speed to retrieve or store data. Typically, to store or detect data on concentric data tracks on the disk surface, a head with a small pick-up coil is moved across the disk surface while the disk is rotating. be moved quickly. The head rests on a thin layer of air created by the rotating disk, and the head is spaced from, but very close to, the surface of the disk.

Sealed disk drives have been introduced to alleviate read/write pickup head contamination and alignment problems. These devices contain a read/write head and carriage, a linear actuator for the carriage, a drive motor and spindle, and a magnetic disk sealed within a housing.

The size of this packaged disk drive is determined not only by the size of the disk, but also by the linear actuator required to move the read/write pickup head. This linear actuator has a cylindrical housing, and a magnet is attached to the inner surface of the housing. A voice coil wound on a bobbin is disposed within the cylindrical housing and is accessed to the magnet assembly. Energizing the voice coil causes the bobbin to move linearly within the housing, thereby moving the attached carriage and pick up head relative to the disk surface.

Conventional linear actuators have an open face on the side of the housing adjacent the disk, thus allowing some magnetic flux to escape from the magnet assembly. Therefore, in order to prevent this leakage magnetic flux from interfering with magnetic recording on the disk surface, the linear actuator must be spaced apart from the edge of the disk. Some disk drives include a magnetic shield between the disk and the linear actuator, but accommodating this shield requires significant space and therefore the mechanical design of the disk drive package. becomes complicated.

It is an object of the present invention to provide an improved linear actuator for a magnetic disk drive.

Another object of the invention is to provide a compact sealed disk drive.

Yet another object of the present invention is to provide a linear actuator for a disk drive that can be placed close to a magnetic disk.

Yet another object of the present invention is to provide a linear actuator with an improved magnetic flux path localized within the actuator.

Briefly, a linear actuator according to the present invention includes a generally cylindrical housing, and the housing includes a plurality of magnets mounted on the inner surface of the housing and a generally cylindrical bobbin. A coil is wound around the bobbin. The bobbin is disposed within the cylinder and is linearly movable with the coil in close proximity to the plurality of magnets. A first magnetic flux transmission means is attached to one end of the housing at the periphery of the housing to provide a magnetic flux path within the housing and prevent magnetic flux leakage. A second flux transfer means is attached to the other end of the housing to provide a second flux path for the magnet and prevent flux leakage.

In a preferred embodiment, the first magnetic flux transmission means comprises an annular iron ring attached to one end of the housing near the periphery of the housing. The second magnetic flux transmission means includes an iron plate covering the other end of the cylindrical housing. Advantageously, guide means for supporting the bobbin and guiding its linear movement are provided within the cylindrical housing and are supported by said first flux transmission means and provide a part of said flux path.

By providing a magnetic flux path completely within the cylindrical housing, leakage flux is minimized and the linear actuator can be placed closer to the disk drive, thereby reducing the size of the disk drive enclosure. .

The present invention and its objects and features will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

FIG. 1 is a perspective view of the disk drive with the top cover removed to show the components. The device comprises a bottom support 10, which includes a drive motor (not shown) and a spindle 1.
2 is installed. Mounted on spindle 12 and rotated by a drive motor is a magnetic disk 14, which is sealed in a drive package. The airflow generated by the rotating disk is captured by the guide body 16 and directed through the channel 18 to the filter 20, keeping the enclosed air clean.

Mounted around the periphery of support 10 is a linear actuator 22 that records and accesses data in concentric data paths on the surface of disk 14. To do this, the carriage 24 and the magnetic head mounted thereon are moved linearly across the surface of the disk 14 while the disk is rotating. Typically, this linear actuator includes a cylindrical housing, and a plurality of magnets are mounted on the inner surface of the housing. The carriage 24 is attached to the voice coil within the cylindrical housing. The voice coil is positioned in close proximity to the magnet assembly, and energizing the coil linearly moves the voice coil support and attached actuator.

FIG. 2 shows a cross-sectional view of a conventional voice coil actuator. This actuator includes a cylindrical casing 30, and permanent magnets 32 and 34 are mounted on the inner surface of the casing 30 with polarities as shown. An annular support, indicated generally by the reference numeral 36, is disposed within the housing 30, and a voice coil 38 is wrapped around the annular support.
The voice coil is placed in close proximity to the permanent magnets 32, 34 and is driven linearly relative to the magnets when it is energized.

The housing 30 is typically made of cast steel and includes an internal cylindrical portion 40 around which the boiling coil is positioned, thus establishing a magnetic flux path as shown by magnetic flux lines 42.

Since the housing is open on the side facing magnetic disk 44 to receive the voice coil and support, some leakage flux will occur from the actuator housing, as indicated by flux lines 46. In order to prevent such leakage magnetic flux from interfering with the magnetic data recorded on the disk surface, it is naturally necessary to place the linear actuator housing away from the disk. . In some conventional enclosed disk drives, a shield is provided within the enclosure between the open face of the linear actuator and the disk to reduce the negative effects of leakage magnetic flux. Furthermore, a distance between the actuator and the disk is required. Additionally, adding a shield to a disk drive package increases the mechanical design complexity of the enclosure, thereby increasing the manufacturing cost of the disk package.

FIG. 3 is a cross-sectional view of a linear actuator according to one embodiment of the present invention. In this embodiment, a magnetic flux transfer plate 52 is provided in the actuator housing 50 on the side of the actuator that is closer to the disk 54, thereby directing the magnetic flux within the housing 50 as indicated by magnetic flux lines 56 and 58. A more efficient and shorter flux path is created. A magnetic flux transmission plate 60 is provided on the opposite side of the actuator housing 50 so that the magnetic flux lines are completely contained within the housing. Because the magnetic flux lines are short, the iron required to provide the magnetic flux path is substantially reduced compared to known actuators with equivalent magnetic flux densities. In conventional designs, the required wall thickness requires casting or casting of iron. However, according to the invention, the wall thickness of the iron can be made sufficiently thin so that stamping and rolling manufacturing methods can be used, thereby saving manufacturing costs.

4 is an exploded perspective view of the linear actuator according to one embodiment of the invention shown in cross-section in FIG. 3; FIG. The actuator's cylindrical housing 50 has a magnetic flux transfer plate 52 that is either permanently attached to the face of the housing or removably attached by mechanical fasteners such as bolts. Integral to and supported by plate 52 are a plurality of iron fingers or guides 62 which fit within slots 64 of bobbin 66 with working clearance. Bobbin 6
6 is made of non-ferrous material and has a voice coil 68 wound around it, which is placed in close proximity to a permanent magnet mounted on the inner surface of the housing 50.

The carriage 70 for the magnetic head assembly 72 is attached to the bobbin 66 by screws 74, thus keeping the bobbin 66 and voice coil 6 within the housing 50.
8 linearly moves carriage 70 and magnetic head assembly 72 across the surface of disk 74. The carriage 70 is supported by a rod 76 attached to the lower support of the disk drive housing and moves linearly over the rod 76 with bearings 78 rolling over the guide plate 80 as before. An iron plate 6 is provided on the surface of the casing 50 opposite to the plate 52.
0 is provided, which completes the magnetic flux path of the housing 50. This plate 60 is attached to a bobbin 66 in the housing 50.
The housing 50 is designed for easy removal when assembling the
Preferably, it is bolted to. Patent application A-
A hole 76 is provided in the plate 60 for receiving a limiter assembly for a carriage such as that disclosed in US Pat.

By minimizing magnetic flux leakage in the linear actuator, the present invention provides a more compact disk file package. Such packages are particularly advantageous for use in compact storage racks used in minicomputer and microcomputer systems. Because the magnetic flux lines are shortened, iron consumption is reduced,
The actuator of the present invention is very lightweight and easy to manufacture.

In particular, the linear actuator of the present invention can be housed in a standard floppy disk size package for driving small disks (eg, 200 millimeter disks). A pack cage like this one has a height of 4.62 inches (11.73 cm) and a width of 8.55 inches.
inches (21.72 cm) and is only 14.25 inches (36.20 cm) long. Heretofore, such packages have required a step motor to drive the magnetic head carriage. However, the use of step motors limits the number of data tracks on the disk surface to about 170 tracks per inch. Voice coil actuator using track following servo controller is 1000
Trucks/inch can be accepted.
Therefore, the use of voice coil linear actuators in accordance with the present invention in small packages can significantly increase data storage capacity in floppy sized disks and packages.

Although the present invention has been described above with reference to specific embodiments, this description is for the purpose of explaining the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the invention.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a magnetic disk drive with the top cover removed, and Figure 2 is a sectional view of a conventional linear actuator for a magnetic drive, showing its magnetic flux path. 3 are cross-sectional views showing one embodiment of the linear actuator according to the present invention, and a diagram showing the magnetic flux path thereof, and FIG. 4 is an exploded view of one embodiment of the linear actuator according to the present invention. FIG. 10...Bottom support, 12...Spindle, 14
...Magnetic disk, 16...Guide body, 18...
Channel, 20... Filter, 22... Linear actuator, 24... Carriage, 50... Actuator housing, 52... Magnetic flux transmission plate,
54... Disc, 60... Magnetic flux transmission plate,
66...Bobbin, 68...Voice coil, 70...
... Carriage, 72... Magnetic head assembly, 74...
...Disk.

Claims (1)

[Claims] 1. A compact linear actuator for moving a pick up head with respect to a disk in a magnetic disk drive device, which includes a substantially cylindrical casing made of a magnetic material with a plurality of magnets attached to its inner surface and open at both ends. , having a substantially cylindrical bobbin arranged in the housing and capable of moving linearly within the housing with a coil wound around the periphery and the coil being brought close to the plurality of magnets; and a central opening; an annular ring made of a magnetic material and serving as a first magnetic flux transmission means that is attached to a peripheral portion of the housing at one end and provides a magnetic path for the magnet to prevent magnetic flux leakage; and the other end of the housing a second magnetic flux transmitting means attached to the magnet to provide a magnetic flux path for the magnet and prevent magnetic flux leakage; a plate of magnetic material extending through the central opening and configured to move linearly with the bobbin; pick-up head carriage means attached to the bobbin; and guide means integral with the annular ring and extending through the bobbin to provide a magnetic flux path between the annular ring and the plate through the bobbin. A linear actuator characterized in that the guide means includes a plurality of finger-like members, and the bobbin has a plurality of passages that engage with the finger-like members.