GB2174553A

GB2174553A - Carriage drive system for a disc drive

Info

Publication number: GB2174553A
Application number: GB08605066A
Authority: GB
Inventors: Hiroshi Doi
Original assignee: Tokyo Juki Industrial Co Ltd
Current assignee: Juki Corp
Priority date: 1985-02-28
Filing date: 1986-02-28
Publication date: 1986-11-05
Also published as: JPS61199278A; GB8605066D0; DE3606061A1

Abstract

In order to reduce the number of components and thereby reduce cost and increase reliability, a carriage drive system for a disc drive having a rectilinearly-movable carriage 1, has a magnetised strip 19 screwed to the side of the carriage 1 and divided into a number of parallel, mutually-spaced magnetic ribs 20a. There are two stators 26 each of which has a magnetic yoke 23 with two poles 24 divided into parallel, spaced ribs 24a. The yokes 23 carry coils 25, and a computer drive circuit 32 magnetises the magnetic ribs 24a alternately to thereby step the carriage 1 along at will in either direction of movement by non-contact magnetic forces. <IMAGE>

Description

SPECIFICATION Carriage drive system for a disc drive Background of the invention This invention relates to a carriage drive system for a disc drive for conventional floppy discs or hard discs, and more particularly to a way of moving a read-write head (normally a magnetic head) along a read-write opening in the sleeve (jacket or cover) of the disc.

Diskettes or floppy discs are well known. A circular plastic disc is coated with magnetisable material whose surface can record data, and the disc is inserted into a sleeve having the small read-write opening. During use, the sleeve is held stationary and the disc is rotated, a magnetic head moving along the read-write opening to read or record data on the disc.

One conventional disc drive carriage drive system is described below with reference to Figures 1 and 2. The disadvantage is that the configuration is rather complicated and the number of parts can cause greater inaccuracy due to the summing of tolerances. In order to achieve very high accuracy of the angle of rotation per pulse (for instance 1.8 +3% per pulse), and to maintain such accuracy, more parts are required and the cost is increased.

Furthermore, the thickness of the steel belt is approximately 50 microns, and the manufacturer of such a high quality steel belt requires advanced technology and is very costly. Nonetheless, breakage of the steel belt occurs and the reliability and maintenance of the steel belt transmission mechanism is not perfect.

A disc drive carriage drive system using a linear motor is described below with reference to Figure 3. The system is very complicated, especially having regard to its bearing construction, and is relatively large and costly.

The invention The present invention provides carriage drive systems for a disc drive as set forth in Claims 1 or 10, and a disc drive as set forth in Claim 11. The remaining Claims set forth preferred features of the invention.

The carriage drive system of the invention is actuated when pulses are applied to the magnetising means, which pulses can be provided from a conventional pulse motor drive circuit. The arrangement can be used for floppy discs or for hard discs.

The invention provides a magnetically-united, non-contact linear pulse motor acting directly on the side of the carriage. The invention eliminates complicated components and thus avoids problems inherent in the inaccuracy of rotary pulse motors, increased number of components or breakage of the steel belt, and the invention can provide increased reliability and lower cost by simplifying construction and reducing the number of parts.

The drawings The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a floppy disc, showing a read-write opening; Figure 2 is a plan view of a prior-art drive system; Figure 3 is a perspective view of part of the prior-art system of Figure 2; Figure 4 is a schematic, part-perspective view of another prior art system; Figure 5 is a plan view of an embodiment of the invention; Figure 6 is a perspective view of the system of Figure 5; Figure 7 is a sketch applicable to the system of Figures 5 and 6; and Figure 8 is a detail of Figure 5.

Figure 1 Figure 1 merely shows the read-write opening in a floppy disc sleeve.

Figures 2 and 3 (Prior Art) The system of Figures 2 and 3 has a carriage 1 made of plastics or any other light-weight material, and which carries a magnetic read-write head 2.

The carriage 1 is constrained to rectilinear to-andfro sliding motion by means of two parallel slide rods 3, fixed to a frame (not shown) and running through parallel holes provided in the carriage 1.

The carriage 1 is moved by a rotary pulse motor 4 (Figure 3) which is fixed to a mounting plate 5 fixed in turn to a boss portion of the frame (not shown) by screws 6. The pulse motor 4 has a pulley 7 fixed to its shaft. The pulley 7 drives the carriage 1 by means of a steel belt 8 (Figure 3) both of whose ends are screwed to the front side of the carriage 1; in this way, the magnetic head 2 is driven along the read-write opening in the floppy disc sleeve. In other words, the rotational motion of the pulse motor 4 is converted to linear motion by the pulley 7 and the steel belt 8.

Figure 4 (Prior Art) Figure 4 shows a stator 9 which is fixed to the frame (not shown) of the disc drive and has a plurality of magnetic poles. A carriage (generally as in Figures 2 and 3) carries a slider 10 which has a magnetic pole, a yoke and a coil.

Figures 5-8 (Embodiment of the Invention A carriage 1 (generally as in Figures 2 and 3) carries an integral strip or scale 19 made of magnetic material. The strip 19 is formed with a number of projections or rails or ribs 20a which are first, mutually-spaced, magnetic elements. The ribs 20a extend at right angles to the direction of motion of the carriage 1 and are of equal pitch. The strip 19 is fixed to the front side of the carriage 1 by screws 21.

The system has two stators 26. Each of the stators has a magnetic yoke 23 which includes magnetic poles 24 formed with ribs 24a like the ribs 20a and defining second magnetic elements. The ribs 24a face the ribs 20a with a small clearance.

The yokes 23 also have cores (not shown) each of which has a coil 25, acting as means for magnetising the poles 24 and ribs 24a. The yokes 23 are carried in a support body 27 made of non-magnetic material, the two stators 26 being clamped between arms on the support body 27 and fixed thereto by a bolt 28. The bottom of the support body 27 is fixed to a frame 29 of the disc drive by means of screws 30, with the interposition of a non-magnetic plate 30a (Figure 7). Wire leads 31 are shown connecting the respective coils 25 to a drive circuit 32 (which controls switching of electric current in response to command signals sent from a computer).

In the system of Figure 5, both coils 25 are wound in the same direction, providing a twophase linear pulse motor having two pairs of stator magnetic poles 24.

In operation, electric current is supplied to one coil 25 from the drive circuit 32. A magnetic circuit (through which magnetic flux flows) is formed as follows: yoke 23, magnetic pole 24 (ribs 24a), clearance 22, strip 19 (magnetic ribs 20a, material 20 bridging the magnetic ribs, further magnetic ribs 20a), clearance 22, another magnetic pole 24 (ribs 24a), back to yoke 23. Due to this magnetic action, the ribs 20a which are located nearest to the ribs 24a (arranged in pairs) are attracted and move say to the right in a single step. For the next step, the electric current is supplied to the coil 25 of the other stator 26 and the coil 25 of the first stator 26 is de-energised. The yoke 23 at the other stator 26 is magnetised, and the ribs 20a nearest the ribs 24a of the other stator 26 are attracted and move to the right. In this way, by alternately switching the current from the drive circuit 32 between the two stators 26 and keeping the current in the same direction, the carriage 1 is moved to the right in steps. The carriage 1 can be moved to the left by carrying out the same procedure, but using a current in the reverse direction. Thus the carriage 1 and the magnetic head 2 can be moved forwards or backwards.

Although a two-phase linear pulse motor is illustrated in Figures 5 to 8, single-phase excitation or single-double excitation can be used in other embodiments of the invention.

Many widely different embodiments of the invention may be made without departing from the scope thereof.

Claims

1. A carriage drive system for a disc drive, comprising: a movable carriage for carrying a read-write head; a series of first, mutually-spaced magnetic elements, which series extends along the carriage in the direction of motion; at least two stators each having at least one second magnetic element facing and adjacent the first magnetic elements; and means for magnetising the second magnetic elements alternately, in response to input signals, to thereby step the carriage along at will in either direction of movement by non-contact magnetic forces.

2. The system of Claim 1, wherein the polarity of magnetisation of the second magnetic elements can be reversed for reversing the carriage.

3. The system of Claim 1 or 2, wherein each of the first and second magnetic elements is a rib extending at right angles to the direction of motion of the carriage.

4. The system of any of the preceding Claims, wherein all the first magnetic elements are magnetically connected.

5. The system of Claim 4, wherein all the first magnetic elements are integral, being formed as projections on a member secured to the side of the carriage.

6. The system of Claim 4 or 5, wherein each stator has two groups of second magnetic elements which are spaced apart in the direction of motion of the carriage, the groups being connected to thereby provide a magnetic circuit with the respective first magnetic elements.

7. The system of any of the preceding Claims, wherein the groups of second magnetic elements are interconnected by a core carrying a coil forming said magnetising means.

8. The system of Claim 6 or 7, wherein each said group comprises a plurality of the second magnetic elements.

9. The system of any of the preceding Claims, wherein the carriage is rectilinearly slideable along fixed guide rods.

10. A carriage drive system for a disc drive, substantially as herein described with reference to, and as shown, Figures 5 to 8 of the accompanying drawings.

11. A disc drive incorporating the carriage drive system of any of the preceding Claims.