GB2240871A - Magnetic head and disk assembly - Google Patents

Abstract

A magnetic head and disk assembly includes two flexible magnetic disks (1a, 1b) separated by a Bernoulli's effect plate (2) and magnetic heads (4a, 4b) for reading data from and/or writing data to the magnetic disks. The magnetic disks, a magnetic disk rotating/supporting mechanism (10), and the magnetic heads are all housed in a sealed enclosure (7, 8). The Bernoulli's effect causes the flexible magnetic disks at high rotation speeds to act like rigid disks so that the heads are not in contact with the disk surfaces, thus permitting performance as in a disk drive using rigid disks The discs which may be elliptical due to tension on the web from which they are cut, have servo sectors along major and minor axes and a control unit stores a table of correction values for head positioning. <IMAGE>

Description

?--:2 _q C> E3 '11.1 1 1 MAGNETIC HEAD AND DISK ASSEMBLY This invention

relates to a magnetic head and disk assembly, and more particularly, to a magnetic head and disk assembly which employs a flexible magnetic disk in a fixed fashion similar to a hard disk drive.

A conventional magnetic head and disk assembly (disk drive) which employs rigid magnetic disks, a socalled hard disk drive, is expensive because the magnetic disks are expensive. Also, the overall weight of the magnetic head and disk assembly is high because of the use of rigid metal magnetic disks.

An object of the present invention is to provide a magnetic head and disk assembly which is inexpensive, thin (having a low profile) and lightweight.

Another object of the present invention is to provide a magnetic head and disk assembly having improved vibration-proof properties.

Another object of the present invention is to provide a magnetic head and disk assembly which has large capacity and high data density, such as that achieved in a hard disk drive.

According to the present invention there is provided a magnetic head and disk assembly including at least one flexible magnetic disk, means for rotatably supporting the magnetic disk, and a magnetic head for reading data from and/or writing data on the magnetic disk, all of which are housed in a sealed housing.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a plan view of a magnetic head and disk assembly with the upper cover removed; Figures 2(A), 2(B) are cross-sectional views of the magnetic head and disk assembly; Figure 2(C) shows a PG sensor; 1 Figure 3(A) is a plan view of a magnetic head support; Figure 3(B) is a section taken along the line AA' of Figure 3(A); Figure 4 is a cross-sectional view of a magnetic head; Figure 5 is a cross-sectional view of part of the magnetic head and disk assembly including the magnetic heads, magnetic disks, and a Bernoullils plate; Figure 6 is a plan view of a flexible magnetic disk; sectors; Figure 8 is a flowchart of a head position correcting operation which uses the servo sectors; Figure 9 is a cross-sectional view of an alternative magnetic head and disk assembly; and Figure 10 is a cross-sectional view of part of the magnetic head and magnetic disks.

Referring first to Figures 1 and 2(A), a magnetic head and disk assembly includes two flexible magnetic disks la, 1b of diameter 5.08 cm. (two inches) in one embodiment and each about 40 Am thick; a Bernoullils plate 2 disposed between the two magnetic disks la, lb and adjacent thereto, the Bernoullils plate 2 being diskshaped with the surfaces of the Bernoullils plate 2 providing the Bernoullils effect; a spindle motor 3 for rotatably driving the magnetic disks la, lb; two magnetic heads 4a, 4b for reading data from andlor writing data to the respective magnetic disks la, ib; arms 6a, 6b for supporting the magnetic heads 4a, 4b at their distal ends; a conventional stepper motor driving mechanism 5 which serves as a magnetic head access means for pivoting the arms 6a, 6b and thereby moving the magnetic heads 4a, 4b in the radial direction of the magnetic disks la, 1b; Figure 7 shows the configuration of the servo 1 1 is SPK1543 a base plate 7 on which the components are mounted; and an upper cover 8 for covering base plate 7.

Each of the two magnetic disks la, 1b includes a plurality (nine in one embodiment) of through-holes forming air ports 9 formed in the vicinity of its centre. Each rectangular-shaped port 9 measures 1 mm and by 2 mm and the ports are equally spaced radially on the disk. Between the two magnetic disks la, lb, lies the Bernoullils plate 2, having a thickness of about 0.3 mm, which prevents magnetic disks la, 1b from coming into contact or adhering to each other. The outer edge of the Bernoullils plate 2 extends past the outer periphery of magnetic disks la, 1b and includes protrusions toward each of the individual magnetic disks la, 1b by several microns to several hundreds of microns. These protrusions are formed by a conventional etching process. As spindle mctor 3 rotates at about 3,600 rpm, air flows between the Bernoullils plate 2 and each of the individual magnetic disks la, 1b through air ports 9 and then flows along the surface of the Bernoullils plate 2 from the inner periphery of magnetic disks la, ib to the outer periphery thereof, so that magnetic disks la, ib do not adhere to the Bernoullils plate 2. The surface of magnetic disks la, 1b each are separated from the Bernoullils plate by about 0.1 mm when the disk drive is operating. The Bernoullils plate 2, together with magnetic disks la, lb, are fixed to a spindle hub 10, described below, so that the Bernoullils plate 2 and magnetic disks la, 1b rotate as one unit.

Magnetic disks la, 1b are fixed to the spindle hub 10 with spaces (not shown) therebetween. Spindle hub 10 is a magnetic disk rotating/supporting means which is formed at the rotary portion of spindle motor 3. An enlarged view of a portion of the structure of Figure 2(A) is shown in Figure 2(B).Spacers 10b, 10c are each - 4 SPK1543 22.8 mm in diameter and have a thickness of 1.5 mm. Each spacer 10b, 10c is fastened to hub 10 and disks la, 1b by three screws, of which screw 10 d is shown. Hub 10 has a diameter of 20 mm and is made of stainless steel. On the upper surface of spindle hub 10 a pulse generator (PG) magnet 11 (see Figure 1) is provided, which is detected at each revolution of hub 10 by a sensor 19 so as to detect rotation of spindle motor 3 by counting pulses generated by PG sensor 19. PG sensor 19 is described 10 below.

The stepper driving mechanism 5, which is the magnetic head access means, includes a rotary shaft 12 having a diameter of 2.6 mm and made of stainless steel, on the distal ends of which are provided two pinions (not shown) of size 5.6 mm and made, for example, of Derlin (Trade Mark) from Dupont or similar plastics material coupled to each other by a spring (not shown). This configuration of the two pinions prevents backlash which would occur in the engagement of the pinions with racks 13a, 13b (described below), and thereby provides improved head positioning accuracy. on one end of each of arms 6, 6b a magnetic head 4a, 4b is disposed, and on the other end thereof are provided racks 13a, 13b, each of which meshes with one of the pinions. Arms 6a, 6b are supported so as pivot about an arm supporting shaft 14 in accordance with the rotation of rotary shaft 12. As the arms 6a, 6b pivot about arm supporting shaft 14, magnetic heads 4a, 4b move radially on magnetic disks la, 1b along the surface thereof to read and/or write on predetermined tracks.

The above- described components of the magnetic head and disk assembly are mounted on die-cast aluminium base plate 7. The components mounted on base plate 7 are covered by an aluminium upper cover 8 fixed to base plate 7 by four bolts 17a, 17b, 17c, 17d.A conventional 1 i SPK1543 gasket 18 formed of an elastomeric material such as rubber is provided between base plate 7 and upper cover 8 to hermetically seal the interior of the assembly. In one embodiment, no air filter is provided in the sealed assembly housing. Below base plate 7 is an electronic control board 16 (including conventional electronic components for control of the disk drive) covered by a lower cover 20. A connector (not shown) which is connected to a host computer system conventionally protrudes from the distal end of control board 16 to the outside of lower cover 20.

PG sensor 19, (as shown in Figure 2(C)) includes a copper wire coil 19b wound around an iron core 19c mounted on the inner surface of cupper cover 8 (Figure 2(A)) at a position whereby sensor 19 faces PG magnet 11 provided on the upper surface of spindle hub 10. PG sensor 19 detects in well known manner the magnetic flux generated by PG magnet 11 at each revolution of magnetic disks la, lb, and thereby detects their rotational speed.

Figures 3(A) and 3(B) show a pad 15a (a magnetic head supporting means) on which magnetic head 4a is mounted. Pad 15a is an aluminium sheet for example and has a part-annulus fan-like shape with a size of 4.6 mm by 8. 5 mm. It includes a central head mounting hole 15A on which magnetic head 4a is mounted. An airflow receiving end of the pad 15a (the upstream side of pad 15) includes a tapered portion 15D so that the stream of air caused by rotation of the disk flows easily between pad 15a and magnetic disk 1. A side 15E of pad 15a which is disposed on the outer periphery of the magnetic disk and a side 15F thereof which is disposed on the inner periphery are arcuate, having substantially the same curvature as the circumference of magnetic disk la. The air stream caused by the rotation of magnetic disk la flows arcuately having substantially the same curvature SPK1543 as magnetic disk la. This configuration of pad 15a causes the air stream to flow smoothly along the sides of pade 15a, and thereby reduces the force which the airflow exerts on pd 15a in the radial direction of the magnetic disk. The air stream enters the gap between magnetic disk la and pad 15a from tapered portion 15D, and passes through the gap at high speed, by means of which disk la is attracted toward pad 15a. Pad 15a also includes a central groove 15B which is closed on one end 15G thereof and whose sides 15H and 151 are arcuate, having the same curvature as sides 15E and 15F. Pad 15a also includes on the two sides of groove 15B a pair of thin grooves 15C whose depth and width are largest near the tapered portion 15D and decrease nearer the air flow-out end of pad 15a. Pad 15a is narrow at its sides 15J, and this allows the air stream to easily escape at sides 15J, dropping a positive pressure near the sides 15J which are disposed on the downstream side of magnetic disk la.

However, formation of thin grooves 15C enables the air stream to be led to sides 15J, thus generating a stable positive pressure near sides 15J. As a result, magnetic disk la makes contact only with magnetic head 4a, as shown in Figure 3(B), and wear of magnetic disk la is thereby minimized. A similar arrangement is provided for head 4b.

Figure 4 is a crossectional view of magnetic head 4a. Magnetic head 4a includes a curved surface 4B which, together with magnetic disk la, forms a gap G with a width of 0.3 gm, an inclined portion 4A which extends obliquely downward from the side of the curved surface 4B from which an air stream flows into the gap, a shoulder 4C which is formed vertically at a height of 100 gm or less on the side of the curved surface 4B from which an air stream flows out from the gap, and an inclined portion 4D extending obliquely downward from the lower i i i 1 SPK1543 1 end of shoulder 4C. As magnetic disk la rotates in the direction indicated by arrow b shown in Figure 4, an air stream enters the gap from the side of inclined portion 4A of magnetic head 4a. Part of the air stream flows downward along inclined portion 4A (in the direction indicated by arrow a in Figure 4), thereby reducing the amount of airflow which passes through gap G between magnetic disk 1 and curved surface 4B (in the direction indicated by the arrow b in Figure 4) as compared with the case where no inclined portion 4A is provided. This in turn reduces the number of dust particles in the air flow which passes through gap G and, hence, reduces the adverse effect of the dust particles on magnetic disk la and magnetic head 4a. Furthermore, since the air stream, which has passed through the gap G, suddenly falls along shoulder 4C and then flows out of gap G along inclined portion 4D (in the direction indicated by arrow c in Figure 4), backflow of the air stream into the gap G is prevented. Thus, with magnetic head 4a so structured, since an air stream which contains a relatively small number of dust particles flows smoothly through gap G between magnetic disk la and magnetic head 4a, the adverse effect caused by the dust particles is reduced and the life of magnetic head 4a is consequently prolonged. Magnetic head 4b is similar to magnetic head 4a. Heads 4a, 4b are each conventional ferrite heads of a size 2 mm by 1.85 mm.

Figure 5 shows magnetic disks la, lb, magnetic heads 4a, 4b and Bernoullils plate 2. As shown in Figure 5, the two magnetic disks la, 1b are respectively disposed on either sides of Bernoullils plate 2 and are adjacent thereto and parallel to the two surfaces of Bernoullils plate 2. Magnetic heads 4a, 4b with pads 15a, 15b are disposed essentially in contact with the surfaces of the individual magnetic disks lc-, 16 on which SPK1543 data is recorded and are each separated from Bernoullils plate by 0.58 mm. Also shown are arms 6a, 6b.

The base material of presently available conventional flexible magnetic disks is typically an organic polymer film formed of polyethylene terephthalate or the like. This material is used for magnetic disks la, lb. Flexible magnetic disks are conventionally manufactured by unrolling the organic polymer film by predetermined lengths and cutting the unrolled film portions into a circle.. Therefore, the rolled organic polymer film is subjected to tension in the longitudinal direction of the film during the cutting, resulting in magnetic media whose strain exhibits anisotropy in the direction of application of the tension. Also, temperature and humidity affect the dimensions of the magnetic disks. There factors determine the substantially elliptical form of the magnetic disk such as shown in Figure 6. Thus, Figure 6 shows a flexible magnetic disk la whose strain exhibits anisotropy.

Assuming that the direction in which strain under tension exists is a longitudinal axis X.(denoted by a horizontal line), and that the direction perpendicular to the longitudinal axis X is a lateral axis Y (designated by a vertical line) at least one servo sector S1 is formed in the direction of longitudinal axis X and at least one servo sector S2 is provided in the direction of lateral axis Y. Magnetic disk la includes at an innermost portion thereof a zone P where no data is stored, and a data zone D and a servo sector which are formed in the radial direction of the disk outside of Zone P. The servo sector consists of servo sector Si formed along the longitudinal axis X and servo sector S2 formed along the lateral axis Y with S1 and S2, disposed such that they form a right angle with respect to the centre of magnetic disk la.

a i A SPK1543 As shown in Figure 7, servo sectors S1 and S2 store conventional servo signals F each of the same frequency and located in a zig zag fashion at positions separated by the same distance from the centre lines C which run in the longitudinal direction of the conventional individual recording tracks T which are arranged circumferentially around the disk. Since the servo signals F are written in both servo sectors S1 and S1 using the same magnetic head 4a, the track width of the servo signals F and of the recording tracks T coincides with the length of the gap G. An offtrack indication is generated by measuring the deviation of the gap G of magnetic head 4a from a desired recording track T. The servo system thus operates conventionally in that when gap G of the magnetic head is located at the centre of track T, servo signals from the servo pattern to the left and right of gap G are equal. If the magnetic head gap G is off track, then servo signals from the servo pattern to the left and right of gap G are unequal.

Figure 8 is a flowchart showing the head position correction process performed by the servo system. This flowchart represents a portion of a control program conventionally provided in a micro-processor and associated memory on control board 16. First, servo signals are read by magnetic head 4a from both servo sector S1 (formed in the direction of the longitudinal axis X) and servo sector S2 (formed in the direction of the lateral axis Y), and the servo correction value conventionally obtained from the servo sector S1 is compared with that obtained from the servo sector S2 so as to check the presence or absence of a recording track T. If no eccentricity exists, subsequent servo signals are read. Eccentricity is detected by comparing expected servo signal values (written in advance in a table in memory) with the actual servo signal values for the SPK1543 elliptical disk so as to determine a measured amount of eccentricity. If there is an eccentricity, the amount is calculated, and the calculated amount of eccentricity is then corrected for. The correction is made by comparing a moving distance of the magnetic head for a true circular disk with the actual elliptical disk for a particular angular rotation of the disk. Thereafter, the preset correction value calculating table in memory is compared with the calculated amount of eccentricity so as to obtain the correction value which is required to obtain a desired recording track T.

Subsequently, a control signal is output to the head moving mechanism on the basis of the correction value. If the position of the gap G of the magnetic head 4a is corrected by the above-described operation, tracking continues. If the gap G is not present on the predetermined track, the head position correction is performed again. In other words, the head position follows a true circle under ideal conditions. If a desired track position is at a position displaced from the true circle (ie, is on an ellipse) the head must be moved to its desired track position. Thus a control signal must be provided to the head positioning mechanism on the basis of data pertaining to the elliptical shape of the disk using date recorded in advance in memory.

A second embodiment of the present invention is described with reference to Figures 9 and 10. In these figures, the same reference numerals are used to denote parts which are the same as those shown in Figures 2 and 5, the description thereof being omitted. As shown in Figure 9, two magnetic disks la, 1b are disposed close to each other. The distance between magnetic disks la, 1b ranges, for example, from several tens of gm to several mn. Magnetic heads 4a, 4b are disposed adjacent to magnetic disks la, 1b so they are in contact with

R i i 1 9 SPK1543 magnetic disks la, lb. Figure 10 shows magnetic heads 4a, 4b and magnetic disks la, lb. Since magnetic disks la, ib rotate at a high speed such as 3600 rpm, they become rigid during rotation, resulting in one disk la functioning as a Bernoullils plate with respect to the other disk lb. Consequently, the Bernoullils plate 2 which is incorporated in the first embodiment is eliminated, and lower cost and lighter weight are achieved.

The present invention is not limited to the aforementioned two embodiments but various modifications are possible without departing from the spirit and scope of the invention as set forth in the appended claims.

Non-limiting examples of modifications to the first is embodiment are as follows: one magnetic head and one magnetic disk may be incorporated in place of two magnetic heads and two magnetic disks. The Bernoullils plate may be eliminated if the magnetic disks are formed of a material which enables them to rotate stably.

Furthermore, if the magnetic disks are wear resistant, the pad which serves to attract the magnetic disk to the head thereto may be eliminated. If the magnetic disks are not flexible, an appropriate relative positioning between the disks and heads enables reading and writing of the disks by the heads without a negative pressure provided by the pads. Furthermore, the magnetic head access means may be externally provided, in which case the magnetic heads are moved to a predetermined position on the magnetic disks from outside of the magnetic head and disk assembly. Thus the immediate volume around the disks and heads is sealed to exclude dust, but the stepper motor and associated components need not be in the sealed volume. Furthermore, the magnetic disk driving means maybe provided externally as long as the motor or the like provided outside of the magnetic head and disk 1 is - 12 SPK1543 assembly is connected to the magnetic disk rotating/supporting means. Possible but non-limiting modifications to the second embodiment are as follows: it is not necessary that data is read from and written on both the two magnetic disks. Hence, it is not necessary to employ two magnetic heads. In a case where one magnetic head is incorporated, a magnetic head may be disposed on one side of the magnetic disk while a flexible flat plate, eg, a disk with no magnetic layer coated thereon, is disposed on the other side of the magnetic disk.

As will be understood from the foregoing description, in the present invention, the flexible magnetic disks can be used as if they were hard disks, and thus provide a thin (low profile) and lightweight magnetic head and disk assembly achieving high density and large capacity to be manufactured at a low cost. Furthermore, since the disks are flexible, damage to the magnetic disks and magnetic heads, which may be caused by collision of the magnetic heads with the magnetic disks, can be reduced. This provides a shockproof magnetic head and disk assembly.

The descriptions herein are illustrative and not limiting. It will be understood by those skilled in the art that modifications will suggest themselves without departing from the spirit and scope of the invention.

The Bernoullils effect as used in the above described embodiments of the invention cause the flexible magnetic disks to act like rigid disks at high angular velocities, thus p ermitting performance similar to that of a rigid or hard disk drive.

i i i 1 i i 1 1 SPK1543

Claims (13)

1. A magnetic head and disk assembly comprising: a flexible magnetic disk; means for rotatably supporting the magnetic disk; a magnetic head for reading data from and/or writing data to the magnetic disk; and a sealed housing containing the magnetic disk, the supporting means, and the magnetic head.

2 An assembly according to Claim 1, further comprising: means for accessing said magnetic head to a predetermined position on said magnetic disk; and means for rotatably driving.said magnetic disk; wherein both said access means and said driving means are contained in said sealed housing.

3. An assembly according to Claim 1 or Claim 2, further comprising supporting means fixed to said magnetic head for attracting said magnetic disk toward magnetic head by flow along the surface of said magnetic disk.

4. An assembly according to Claim 3, wherein a flat plate having Bernoullils effect is disposed adjacent a surface of said magnetic disk.

5. An assembly according to Claim 4, wherein said flat plate is disposed adjacent said magnetic disk on a second surface of said magnetic head.

6. An assembly according to Claim 4 or Claim 5, wherein said flat plate is flexible.

7. An assembly according to any one of Claims 4 to 6, wherein said flat plate is a magnetic disk.

8. An assembly according to any one of Claims 4 to 6, further comprising: a second rotatable magnetic disk disposed adjacent said flat plate on a surface thereof remote from said first magnetic disk, and a second magnetic head disposed adjacent to said second magnetic disk on a surface thereof remote from said flat plate.

9. An assembly according to Claim 8, wherein said k SPK1543 second magnetic head accesses said second magnetic disk by said access means.

10. An assembly according to Claim 8 or Claim 9, further comprising supporting means fixed to said second magnetic head for attracting said second magnetic disk toward said second magnetic head by flow of a fluid along a surface of said second magnetic disk. -

11. A magnetic head and disk assembly comprising:

two flexible rotating magnetic disks; a magnetic head driven radially on a surface of each magnetic disk so as to read data from and write data to each magnetic disk; and a flat plate for providing the Bernoullils effect; wherein the two magnetic disks are disposed on two sides of said flat plate in an opposed relation, and said two is magnetic heads are disposed adjacent to said two magnetic disks on surfaces thereof remote from said flat plate.

12. An assembly according to Claim 11, further comprising supporting means fixed to each of said magnetic heads for attracting an associated one of said magnetic disks thereto by virtue of flow of a fluid along a surface of the associated magnetic disk.

13. A magnetic head and disk assembly, substantially as hereinbefore described with reference to, and as illustrated by, Figures 1 to 8, or Figures 9 and 10J, of the accompanying drawings.

Published 1991 atThe Patent Office. State House. 66171 High Holborn. London WC1RA11P.Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point Cwmrclinfach. Cross Keys. Newrport, NP1 7HZ. Printed by Multiplex techniques lid, St Mary Cray. Kent- 1 1 i i