MAGNETIC DISC DEVICE

Abstract: A magnetic disc device comprising a case (13) composed of a base (13a) and a cover (13b); a plurality of magnetic discs (10) housed within the case (13); a plurality of magnetic heads (11) for read/write operations and conducting a seeking motion on each magnetic disc (10) surface; and arms (12e) for driving the magnetic heads (11), wherein a recess (18) for accommodating a printed circuit board (16) is formed on the outer surface of the base (13a) in an area outside of the range of movement of the magnetic heads (11) and the arms (12e). Preferably the recess (18) is located adjacent a drive motor (15) for the discs (10) and the printed circuit board (16) surrounds the drive motor (15).

Description: The present invention relates to a magnetic disc device used as a memory means for, for example, a mini-computer or a micro-computer. Conventionally, a magnetic disc device using a hard disc 3.5 inches (88 mm) in diameter is used as such a memory means, and is required to have a high memory density. A prior art magnetic disc device comprises magnetic discs rotatably supported within a case, magnetic heads for read/write operations on the magnetic discs, and a head actuator for driving the magnetic heads on the magnetic disc surface to read/write information data from and to the magnetic disc. Such devices are described in US 4,568,988 and in GB 2,092,834. The above-mentioned prior art magnetic disc device can hold only one or two magnetic discs, and this does not meet the present requirements for a high memory density. However, if the number of magnetic discs is increased, in order to enrich the memory density, the overall height of the magnetic disc device must be increased, and thus compatibility with conventional magnetic disc devices is lost. Attempts have been made to increase the number of magnetic discs whilst making the overall size of the device as small as possible. In US 4,194,255 a motor offset from the level of the head actuator is used to create a cooling airflow in the device as well as rotating the hub. By having one component doing many tasks, the device size may be reduced. Also, the prior art magnetic disc device comprises a printed circuit board of substantially the same size as the base of the case and attached to the outside of the base. Various control circuits for driving the magnetic disc device are mounted on the printed circuit board. Regarding the magnetic disc device using 5 inch (125 mm) diameter discs, all of the necessary control circuits can be mounted on one printed circuit board, since the case is relatively large, and thus a large printed circuit board is attached to the case. However, for the magnetic disc device using 3.5 inch ( 88 mm) diameter discs, all of the control circuits cannot be mounted on one printed circuit board having a relatively small size corresponding to the small sized case, and therefore, two printed circuit boards must be attached to the outside of the case, which increases the height of the magnetic disc device and impedes the realization of a small and compact magnetic disc device. The present invention especially relates to a half-height type magnetic disc device comprising a swing type actuator and four magnetic discs housed therein. This type of magnetic disc device is described in our co-pending European Patent Application No. 87304907.6 published as EP-A-248,650. The height dimension of the magnetic disc device is commercially standardized and a full-height type magnetic disc device is marketed. The half-height type magnetic disc device has been developed to realize a small size magnetic disc device which is compatible with the full-height type magnetic disc device, and advantageous from the standpoint of space saving since the height is a half of that of the full-height type magnetic disc device. On the other hand, when the capacity of the magnetic disc device is to be increased using an ordinary interface circuit, it is desirable to double the number of the discs, from the standpoint of easy installation of a new magnetic disc device having an increased capacity in place of an old device, since it is easy to exchange an old device with a new one and/or simultaneously use a new device with an old one through an ordinary interface circuit. Therefore, a two-disc magnetic disc device was developed as an improvement on a one-disc magnetic disc device. Subsequently, a magnetic disc device comprising four discs has been developed as an improvement on the two-disc device. The present invention facilitates the housing of four discs in a half-height type magnetic disc device. In accordance with the present invention a magnetic disc device comprises a case composed of a base and a cover; a plurality of magnetic discs housed within the case; a plurality of magnetic heads for read/write operations and conducting a seeking motion on each magnetic disc; and, arms for driving the magnetic heads, characterised in that a recess for accommodating a printed circuit board and including a stepped portion offset towards the inside of the case formed on an outer surface of the base in an area outside of a range of movement of the magnetic heads and arms. The provision of the recess on the outside of the base and the disposition therein of a printed circuit board for driving the motor, enables a greater number of discs to be accommodated within the case than the prior art structure without increasing its height. This enables four discs to be stacked in the shortened half-height type device housing. A particular embodiment of a magnetic disc device in accordance with this invention will now be described with reference to the accompanying drawings; in which:- Figure 1a is a plan with the cover removed; Figure 1b is a section through the magnetic disc device; Figure 1c is an under plan with the main printed circuit board removed; Figure 2 is an exploded perspective view; Figure 3 is a section showing the bottom plate attached; Figure 4 is a perspective view of a head arm actuating means of the magnetic disc device; and, Figure 5 is an exploded perspective view of the head portion of the magnetic disc device. Figures 1 and 2 illustrate an embodiment of the present invention, wherein Figure 1a is a view of the device from above, with the cover thereof removed, Figure 1b is a sectional view along the line b-b of Figure 1a, Figure 1c is a view of the device from below with the main printed circuit board removed, and Figure 2 is a view of the device when disassembled. As illustrated in Figures 1 and 2, a magnetic disc device according to the present invention comprises: a housing (case 13) formed by a base 13a and a cover 13b; four magnetic discs 10 secured to a spindle 14; eight magnetic heads 11 for magnetic read/write operations at the upper and lower surfaces of each magnetic disc 10; and a head actuator 12 for swinging the magnetic heads 11 in the direction of the arrow AA′ on the magnetic disc surface. The head actuator 12 comprises a drive motor 12a, a capstan 12b, a steel belt 12c, a sector 12d, head arms 12e, and a pivot 12f. Outside of the base 13a are disposed a spindle drive motor l5, a sub-printed circuit board l6 for driving the spindle drive motor l5, and a main printed circuit board l7 mounting a read/write circuit for reading data from and writing data to the magnetic disc. A recess l8 is formed on the outside of the base l3a in an area opposite to the head actuator l2 with respect to the spindle drive motor l5. The sub-printed circuit board l6 for driving the motor l5 is disposed in the recess l8 and secured therein with a flange of the motor l5, which flange is also disposed in the recess l8. The magnetic head ll is attached to an end of the head arm l2e through a gimbal spring and a load spring 28. On the main printed circuit board l7 are mounted an interface circuit, a read/write circuit and a servo control circuit for positioning the magnetic heads ll. It is preferable to dispose a disc spindle drive circuit on the sub-printed circuit board l6, since the sub-printed circuit board l6 is located in the vicinity of the spindle drive motor l5. With this structure, the sub-printed circuit board l6 can be accommodated without interfering with the head actuator l2 and the magnetic head ll, since the recess l8 is provided on the base l3a at an area opposite to the head actuator l2 with respect to the spindle drive motor l5, outside of the range of movement of the head actuator l2 and the magnetic head ll. Therefore, it is possible to accommodate four magnetic discs l0 without increasing the height of the device housing, and thus realize a compact magnetic disc device having a high memory density. The magnetic disc device illustrated in Fig. la is seen from above, with the cover removed, and Fig. 3 shows a vertical section thereof with the bottom plate attached. This magnetic disc device is of a half-height type having a commercially standardized outer shape dimension and using 3.5 inch discs. That is, the disc diameter is 95 mm, the longitudinal length of the device ℓ₁ = l46 ± 0.5 mm, the lateral length ℓ₂ = l0l.6 ± 0.5 mm, and the height ℓ₃ = 4l.3 ± 0.3 mm. A bottom plate 30 (Fig. 3) for covering the main printed circuit board l7 is disposed below the base l3a and secured thereto together with the main printed circuit board l7 by screws. The height ℓ₃ is the dimension between the lowest surface of the bottom plate 30 and the top surface of the cover l3b. The gap d between the adjacent magnetic discs l0 is 4.5 mm, and the thickness t of each magnetic disc l0 is l.27 mm. Five head arms l2e are arranged to conduct a seeking motion on both surfaces of the four magnetic discs l0, as shown in Fig. 3. The thickness of the two uppermost and lowermost head arms is 2.0 mm, and the thickness of the three intermediate head arms is 2.8 mm. The tip of each head arm l2e is thinned to l.l54 mm to allow the load spring 28 to be attached. The gap between the lower surface of the lowermost magnetic disc l0 and the upper surface of the base l3a is 3.5 mm. The head arms l2e and the magnetic head ll conduct a seeking motion, in the direction shown by the arrows A-A′, on the disc surface between the position of solid line and the position of dash line, as illustrated in Fig. la. Therefore, a space (gap) must be provided to allow movement of the head arm and the magnetic head when seeking the lower surface of the lowermost magnetic disc, between the base l3a and the lowermost disc. However, it is unnecessary to provide such a gap in the area outside of the range of movement of the arm and the head. Therefore, in accordance with the present invention, a recess l8 is formed on the outside (underside) of the base in the area outside of the range of movement of the arm and the head. The inner side (upper side) of the base protrudes inward (upward) corresponding to the thickness of the lowermost arm and the head. The depth D of this recess l8 is 4.7 mm (approximately 5 mm) (Fig. lb). The swing actuator structure of the head arm l2e is illustrated in detail in Fig. 4. The head arm l2e is rotatable about the pivot l2f, as shown by the arrow Q, and a mashroom-shaped sector l2d is secured to the head arm l2e. A capstan l2b is disposed facing and adjacent to the head of the sector l2d. The capstan l2b is rotatable about a shaft 48, as shown by the arrow P, a tension spring 47 is attached to the stem of the sector l2d, and an end of a steel belt l2c is bonded to the tension spring 47. Another steel belt l2c′ is secured to the opposite side of the sector l2d. Both steel belts are wound around the capstan l2b and secured thereto at the back thereof by a screw. Both steel belts may be formed as one integral strip. With this structure, the capstan l2b is rotated as shown by the arrow P to swing the sector l2d through the steel belts l2c, l2c′, thus rotating the head arm l2c as shown by the arrow Q about the pivot l2f. Numeral 60 designates a groove for holding the lead cable 25a′. The structure for supporting the magnetic head ll is illustrated in detail in Fig. 5. The load spring 28 is made from a leaf spring. A gimbal 29 also made from a leaf spring is bonded to an end of the load spring 28 by spot welding. A support piece 29a is formed by cutting the inner area of the gimbal 29. The support piece 29a is bonded to an upper recess surface 50 of the magnetic head ll. The magnetic head ll has a core 25d on which a coil (not shown) is wound and the coil lead 25a is taken out therefrom. The coil lead 25a is covered by a protecting outer tube to form a lead cable 25a′ from the end portion of the load spring 28. The root portion 28a of the load spring 28 is secured to the end of the head arm l2e (Fig. 2). As mentioned above, in accordance with the present invention, a compact magnetic disc device with a high memory density is realized with a simple construction, which is very advantageous in practical use. Also, it is possible to provide a half-height type 3.5 inch magnetic disc device having four discs accommodated therein.

Claims: A magnetic disc device comprising: a case (13) composed of a base (13a) and a cover (13b); a plurality of magnetic discs (10) housed within the case (13); a plurality of magnetic heads (11) for read/write operations and conducting a seeking motion on each magnetic disc (10) surface; and, arms (12e) for driving the magnetic heads (11), characterised in that a recess (18) for accommodating a printed circuit board (16) and including a stepped portion offset towards the inside of the case is formed on an outer surface of the base (13a) in an area outside of a range of movement of the magnetic heads (11) and arms (12e). A magnetic disc device according to claim 1, wherein a main printed circuit board (17) having a size substantially the same as the base (13a) is attached to the outside of the base and a sub-printed circuit board (16) is accommodated within the recess (18). A magnetic disc device according to claim 2, wherein an interface circuit, a read/write circuit and a servo control circuit for positioning the magnetic heads (11) are all mounted on the main printed circuit board (17) and a disc spindle drive circuit is mounted on the sub-printed circuit board (16). A magnetic disc device according to claim 1, 2 or 3, wherein the magnetic discs (10) are standard 3.5 inch (88 mm) sized discs. A magnetic disc device according to claim 4, wherein the device is of the half-height type and accommodates four magnetic discs. A magnetic disc device according to claim 3, 4 or 5 wherein : a motor (15) for driving a spindle (14) of the magnetic discs (10) is mounted with the main printed circuit board (17) outside of the base (13a) of the case (13), and a head actuator (12b, 12c) is housed with the magnetic discs (10) and the magnetic heads (11) within the case (13), the recess (18) being provided on an outer surface of the base (13a) in an area opposite to the head actuator (12b, 12c) with respect to the spindle drive motor (15). A magnetic disc device according to any one of the preceding claims, wherein each of said magnetic heads is mounted at a free end of the corresponding arm, and said arms are rotated to drive said magnetic heads. A magnetic disc device according to claim 6 or 7 wherein : the head actuator (12b, 12c) is mounted on an inner surface of said base; and the motor (15) for rotating the magnetic discs, is mounted on the outer surface of said base (13a) at a level which is offset inside of said case with respect to a level at which said actuator (12b, 12c)is mounted on the inner surface of said base in an area outside of a range of movement of said arms and said magnetic heads.

Inventors: MIHARA, TAKAHISA, SAITO, SIGEO
Applicants: FUJITSU LIMITED
Application year: 1987
Main classification: G11B25
IPC codes: G11B33, G11B19, G11B25