Patent Publication Number: US-5841610-A

Title: Miniature hard disc system having single voice coil magnet motor

Description:
This application is a File-Wrapper-Continuation of Ser. No. 08/484,685 filed Jun. 6, 1995, now abandoned, which is a Divisional of Ser. No. 08/181,888 filed Jun. 14, 1994, now abandoned, which is a File-Wrapper-Continuation of Ser. No. 08/056,984 filed May 3, 1993, now abandoned, which is a File-Wrapper-Continuation of Ser. No. 07/932,922 filed Aug. 20, 1992, now abandoned, which is a File-Wrapper-Continuation of Ser. No. 07/807,793 filed Dec. 12, 1991, now abandoned, which is a File-Wrapper-Continuation of Ser. No. 07/477,747 filed Feb. 9, 1990, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed generally to the field of hard disc drives, and more particularly to miniature Winchester-type hard disc drive systems. 
     BACKGROUND OF THE INVENTION 
     With the rapidly expanding development of personal computers into the field of first what were termed portable, then lap-top, and now notebook size computers, there has been a tremendous demand for maintaining the performance of the disc drive systems of such computers. The major development in this direction has been the development of smaller Winchester-type disc drives as replacements and enhancements to floppy disc drives for program storage. The Winchester disc drive, in general, provides higher capacities and faster speeds of operation, factors which are of great importance for the effective use of personal computers running advanced software packages. 
     The Winchester-type disc drives that have been developed for the personal computer market were initially based on the use of hard discs of a diameter of approximately 5.25 inches. Many of these disc drives used stepper motors for positioning a transducer over a selected track on the rotating disc, although larger capacity systems typically used voice coil motors. The next step in reduction of size of the disc drive was to cut the &#34;form factor&#34; (the dimensions of the external case for the complete disc drive) by one half, so that the resulting disc drive used a platter of 3.5 inch diameter. The height of the disc drive was also becoming a significant factor, and efforts were made to reduce the height of the disc drive as well, so that the size of the casing for the personal computer could be minimized. However, as to most lap-top and notebook computers, hard disc drives continue to be external devices. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a compact hard disc drive system having reduced length, width and height dimensions. 
     Another object of the invention is to provide a compact hard disc drive system which may be inserted and removed from the computer, both to maximize the effectiveness of the disc drive and provide additional storage capacity by interchanging disc drives, as well as to provide for security for the information stored on the disc drive. 
     A further objective of the present invention is to provide a disc drive which is compatible with the reduced power budget available in a battery-operated portable computer. Typically, portable computers only provide 5 V DC, which must be capable of providing sufficient power both to maintain the disc spinning at a constant speed, and powering the motor of the head arm actuator to selectively position the head over a track on the disc and maintain the head position over the target track on the disc. 
     Another object of the present invention is to utilize a voice coil motor design which is extremely compact yet capable of reliable positioning of the transducer supporting actuator arm relative to the disc on a long-term basis. 
     Yet another objective of the invention is to provide quick connect/interconnect capability on the outer portions of the head disc assembly to provide a simply-connected interface to the drive control electronics. 
     The compact Winchester-type disc drive of the present invention was specifically designed to provide a system which will meet the demands of notebook and lap-top size and type computer systems. In a preferred embodiment, the rotating disc dimensions will be 15 mm inside diameter to 45 mm outside diameter. 
     In the preferred embodiment of the present invention, two hard discs will be provided, although a single hard disc design may also be used. Storage on each disc in excess of 5 megabytes once the discs are formatted is provided. An actuator system supports two read/write heads for each disc, one head positioned on each side of the disc, to write digital information on and read digital information from the disc. A positioning mechanism is provided to move the transducer between the tracks on the discs and for holding the transducer accurately positioned over each track to write information on and read information from the disc. 
     In a preferred embodiment of the present invention, the actuator includes a rotary voice coil motor, which is arranged to move the transducer along a path extending in an approximately radial direction with respect to the hard disc to move the transducer selectively to any track between the inner diameter of 15 mm and the outer diameter of 45 mm. 
     Means will be provided for lifting the heads from the disc, comprising either a shape memory metal withdrawal system or a ramp system combined with a head rest area adjacent the outer diameter of the disc in order to provide a very high resistance to non-operating shocks. 
     By incorporating the features generally outlined above and to be described in further detail below, a disc drive having an overall outer dimension of about 70 mm by about 50 mm, with a thickness of 10 mm can be achieved, wherein the disc inner diameter is 15 mm and outer diameter is 45 mm. In this way, a high compact, easily inserted and removed disc drive is achieved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of the disc drive of this invention; and 
     FIGS. 2A and 2B are sectional views of the disc drive of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     The compact Winchester disc drive of the present invention is shown in a top plan view (with the cover removed) in FIG. 1 and in a vertical sectional view in FIG. 2. In this figure and in FIG. 2, like components are designated by like reference numerals. 
     Referring first to FIG. 1, the major elements of the compact disc drive of the present invention are shown, including a housing 2 which includes upright walls 4, 6, 8, and 10. It is anticipated that the housing may be slid into a slot provided within the computer for the disc drive system. In order to minimize the electronics which must be provided on this very small disc drive, an external connector generally indicated at 12 is provided on the housing wall to the rear of motor 11. A second connector may be provided on the bottom surface 16 of the disc drive to provide additional electrical connections from the disc drive to the electronics which are in turn supported within the computer. 
     By providing the electrical connectors 12, 14 immediately adjacent the voice coil motor 11 and the leads which run back from the transducer 22, the length of the runs of the wires is minimized. This is important especially with respect to the wire length from the external interconnect 12, 14 to the transducer 22 because the signals picked up from the transducer 22 are relatively weak. In order to amplify these signals, an internal preamplifier (not shown) may be provided mounted on the baseplate 16 of the housing 2. In this way, the signals picked up from the transducer receive sufficient amplification to be accurately replicated after being transferred over the connecting interfaces 12, 14 to the electronics incorporated in the disc drive. 
     The drive is mounted in a hard case without external shock mounts. It is anticipated that to accommodate the minimal size of the disc drive, an appropriate mount can be incorporated into the lap-top or notebook size computer with which this disc drive is especially intended to work. 
     The disc drive system designed in accordance with the preferred embodiment of this invention is a microprocessor-based device which moves the transducer 22 from track to track across the surface of the disc 30 in response to commands received by the microprocessor from the host system on the computer by way of a disc drive controller. The disc drive controller and microprocessor of the present invention are not shown herein, and would be mounted externally to the disc drive and connected by the interface 12 or 14 to the disc drive in order to minimize the parts count supported on the disc drive. Alternatively, certain critical electronic elements of the present invention may be supported from the base 16 of the disc drive internally or externally, provided appropriate shock damping and thermal isolation is utilized. 
     Turning to FIG. 2A, each disc 30A, 30B is mounted within the housing and on the hub of a spindle 32 supported on a spindle motor 34. Each of the discs has an inner diameter of about 15 mm and an outer diameter of about 45 mm, and is from 0.020 inch to 0.025 inch thick. In a preferred embodiment as shown in FIGS. 2A, 2B, 2C, two discs 30 are supported on the spindle 32, and transducers 22A, B, C, D are provided for reading and writing on both surfaces of each disc. The transducers 22 in a preferred embodiment comprise MR heads of the type made by PCI Components, Inc. of Minneapolis, Minn. 
     Each read/write head 22 is mounted on a gimble 40 mounted at one end of a flexure 42, the gimble supporting a 70 percent of normal length slider/gimble/suspension and a 50 to 70 percent of normal length flexure 42. 
     The supported end 44 of each flexure 42 is fastened to arm 46 which is rotated about pivot 48 by voice coil motor 50. The flexure and arm are arranged to provide a straight arm extending from the voice coil motor out to the disc in accordance with the teachings of the Gitzendammer U.S. Pat. No. 4,620,251, assigned to the assignee of the present invention. The supporting arm 46 is supported at pivot 48 on a steel shaft fixed to the races of a pair of ball bearings 49 which are in turn located in the base 16 of the housing 2. The shaft 48 rotates about the axis 52 to quickly and reliably alter the position of the transducers 22A-D relative to the tracks on the disc. 
     The voice coil motor 50 in a preferred embodiment comprises a single moving magnet 56 supported on the distal end of the arm 46 from the flexure 42. The single moving magnet motor 50 which comprises in a preferred embodiment a moving magnet and backarm which serves as a balancing counterweight is movable between two coils 57A, B supported above and below the magnet 50. Alternatively, a coil may be supported on the distal end of the arm 46, movable with selective activation of upper and lower magnets. In this instance, one of the magnets may be supported from the base casting 16 of the housing, with the other magnet being supported from the upper portion 62 (FIG. 2) of the housing. 
     Referring next to FIG. 2B, the voice coil motor 34 is clearly shown being an in-hub spindle motor which supports the disc on the outer rotating hub 64. To minimize the height of the motor, Hall-less driving circuits of the type disclosed in the patent application of A. Cassat, now U.S. Pat. No. 5,001,401, issued March 1991, are incorporated in the motor to determine its position and appropriately drive it in the correct direction. 
     Referring to both FIG. 1 and FIG. 2B, it is important to note that in order to maximize the ability of the system to handle shocks of up to 100 to 150 g&#39;s for portable applications, the system is designed to provide for landing the head gimble array on a separate area or ramp 80 adjacent the rotating disc, rather than allowing the head to rest on the disc as in most known smaller disc drives. One approach to achieving this goal is to use a shape memory metal head gimble assembly head lifting wire of the type disclosed in U.S. patent application Ser. No. 299,400, filed Jan. 23, 1989 (incorporated herein by reference), assigned to the assignee of this invention, wherein a wire would extend down the centerline of the flexure 42 and be attached to a point on the flexure, the wire being shortened in length in response to application of a current to cause the bending of the flexure 42 and to lift the flexure up off the rotating disc surface. Alternatively, an inclined ramp 81 may be utilized cooperating with the flexure 42 and a cam member incorporated as a ridge 90 in flexure 42 so that the flexure and head gimble assembly as it moves horizontally relative to the disc and reaches the edge of the disc, is lifted above the disc unloading the head from the disc even in the absence of rotation of the disc. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. The present embodiment is presented merely as illustrative and it is not intended that the invention be limited to the specific example described above and shown in the attached figures. It is believed that by using the combination of features described above, that a compact disc drive having dimensions of approximately 50 mm by 70 mm by 10 to 19 mm high can be achieved which can be driven with only a 5 V DC power supply. A sufficient capacity of 10 megabytes or more data storage can be achieved on a 15 mm ID by 45 mm outside diameter by 0.020-0.025 inch thick disc, and reliable positioning of the head relative to the disc can be achieved. The remaining critical dimensions which can be achieved by the novel combination of design features described above is listed below. 
     pivot/gap=1.040 
     pivot/head=1.046 
     gap/head=0.028 
     pivot/center=1.082 
     # of TKS=700 
     R0=0.840 
     R last --  TK=0.495 
     RPM=3000 
     The full scope of the present invention is to be limited only by the meaning and range of equivalency of the following claims.