Retaining Ring for Disc Drive Spindle Motor

This invention relates generally to the field of disc drive data storage devices. More specifically, the invention relates to a retaining ring for a spindle motor for spinning the discs on which data is recorded in such a device.

Disc drive data storage devices of the "Winchester" type are well-known in the industry. Such devices utilize rigid discs coated with a magnetizable medium for the storage of digital information in a plurality of circular concentric tracks. This information is written to and read from the discs using a data head mounted on an actuator mechanism which moves the head from track to track across the surface of the disc under control of electronic circuitry. The discs are mounted for rotation on a spindle motor which causes the discs to spin and the surface of the discs to pass under the heads.

Early five 1/4 inch Winchester disc drives included a brushless DC spindle motor which was mounted to a base of a drive housing. The actual motor components were outside of the housing and a shaft of the motor projected into the housing where it was coupled to a hub which was used to mount the discs.

As industry demands for smaller sizes of disc drives has lead to the introduction of half-height five and one-quarter inch drives, three and one-half inch, two and one-half inch, 1.8 inch and smaller drives, the size and configuration of the spindle drive motor has also changed. "Pancake" spindle motors have been used which employ an air gap in the motor which was positioned axially to the motor shaft. "In-hub" spindle motors used motor coils and magnets which were located inside the disc carrying hub.

Current and future generations of disc drives continue to shrink from 2.5 inch to 1.8 inch form factors and smaller. However, many of the assembly steps remain manual and require human interaction. For example, stator windings in the spindle motor are manually positioned and conductively attached to form an external connection. Additionally, with such small size drives the stiffness of the assembly becomes an issue because it can lead to undesired resonances which can limit performance of the disc drive.

The spindle motor of the present invention includes a rotating hub for mounting discs in a disc drive. The rotatable hub includes a magnet and is rotatably coupled to a motor base. The motor base carries a wiring assembly which includes a plurality of electrical contacts. A stator assembly includes a plurality of stator windings and is fixedly coupled to the motor base. A wire guide is coupled to the stator assembly and positions wires of the stator windings adjacent the electrical contacts of the wiring assembly. These wires are soldered to the electrical contacts. In one embodiment, the wire guide is removed from the spindle motor after the wires of the stator windings are soldered to the electrical contacts.

In one embodiment, the stator assembly is somewhat disc-shaped and the wire guide is a ring which conforms to the shape of the stator assembly. The wire guide includes a plurality of slots for carrying wires of the stator windings.

In another embodiment, an adhesive covers a portion of the stator windings. The adhesive acts to stiffen the stator assembly thereby damping the resonance during operation of the spindle motor. The wire guide blocks the adhesive from flowing beyond the edge of the stator assembly where it could interfere with the rotor hub.

FIG. 1 is a plan view of a disc drive data storage device in which the present invention is useful.

FIG. 2. is a perspective view of a retaining ring in accordance with the present invention.

FIG. 3 is an exploded side plan view of a retaining ring, stator assembly and motor base in accordance with the invention.

FIG. 4 is a top plan view of the stator assembly, retaining ring and base plate of FIG. 3.

FIG. 5 is a cut away top plan view of the stator assembly, base plate and non-removable retaining ring.

FIG. 6 is a side cross-sectional view taken along line 6--6 of FIG. 5 and showing a rotor hub of the disc drive motor.

FIG. 7 is a cross-sectional view of a disc drive motor in accordance with another embodiment of the present invention.

FIG. 1 shows a plan view of a disc drive 2 for use with the present invention. Disc drive 2 includes a base member 4 to which internal components of the unit are mounted. Base member 4 couples to top cover 6 which forms a sealed environment for critical parts of disc drive 2.

Disc drive 2 includes a plurality of discs 8 which are mounted for rotation on a spindle motor, shown generally at 10. A plurality of magnetic read/write heads 12, usually one per disc surface, are mounted to an actuator 14. In the example shown at drive 2, actuator 14 is a rotatory actuator which is mounted for pivoting about a pivot shaft 16. Actuator 14 includes a number of head mounting arms 18 which couple heads 12 to the actuator body via a plurality of load beam/gimbal assemblies 20. Actuator motor 22 is also coupled to actuator body 14 to provide a force to move heads 12 to a desired position on the surface of disc 8.

In operation, the spindle motor 10 causes disc 8 to rotate. Electronic circuitry 24 energizes actuator motor 22 causing actuator 14 to rotate about pivot 16 whereby magnetic read/write head 12 is moved through an arc radially across the surface of disc 8. Actuator 14 positions head 12 over a concentric track, for example track 26 of disc 8. This allows electronic circuitry 24 to read back or write information at desired locations on disc 8.

FIG. 2 is a perspective view of wire guide ring 40 in accordance with the present invention. Wire guide ring 40 is for use in spindle motor 10 as will be described below. Ring 40 includes outer circumference 42 and inner circumference 44 and is adapted for cooperation with a stator assembly (not shown in FIG. 2) of motor 10. Guide ring 40 includes guide structures 46a through 46i. Each guide structure 46a through 46i includes a wire channel 48a through 48i, respectively. Wire channels 48a through 48i are adapted for holding wires of windings carried on the stator assembly (not shown in FIG. 2). Wire guide ring 40 is constructed of a plastic or a metal, or hybrid of these materials, but is not limited to these.

FIG. 3 is an exploded side plan view of wire guide ring 40, stator assembly 50 and motor base 52. Stator assembly 50 includes a plurality of stator windings or coils and stator slots (not shown in detail in FIG. 3). Each stator winding includes a stator wire 54. Stator wires 54 are individually held in wire channels 48 in each guide structure 46 of wire guide ring 40. The guide ring 40 and stator assembly 50 are placed in motor base 52 which includes a drive shaft 56 and a wiring harness (not shown in FIG. 3). When properly positioned, each wire channel 48 positions each wire 54 of the stator windings over the appropriate electrical contact on the wiring harness or electrical connections. The wire 54 is then soldered or otherwise electrically connected to the wiring harness.

FIG. 4 shows a top plan view of wire guide ring 40 assembled with stator assembly 50 and motor base 52. FIG. 4 also shows wiring harness 60 which includes electrical contacts 62b, 62c, 62e, 62f, 62h and 62i. Stator assembly 50 includes stator windings 64a through 64i and stator slots 66a through 66i which are radially spaced around the axis of stator assembly 50. Each winding 64a through 64i is formed from a stator wire 54a through 54i, respectively. As shown in FIG. 4, wires 54b, 54c, 54e, 54f, 54h and 54i are held in their respective wire channels of guide ring 40. The wire channel is positioned at the appropriate stator wire position over contact 62b, 62c, 62e, 62f, 62h or 62i of wiring harness 60 and are soldered thereto. Inner circumference 44 of retaining ring 40 is designed to fit over stator slots 66. Spacing between adjacent stator slots 66 provide room for guide structure 46 and wire channel 48.

FIG. 5 is a detailed view of a portion of a non-removable wire guide which shows stator windings 64b through 64d. In FIG. 5, individual wires 60b and 60c of wiring harness 60 are shown in phantom. Wires 60b and 60c are soldered to stator wires 54b and 54c of harness 50 at contacts 62b and 62c, respectively. FIG. 5 also shows permanent magnet 70 which is carried in around outer circumference 42 of a rotor hub (not shown in FIG. 5).

FIG. 6 is a cross-sectional view of FIG. 5 taken the line labeled 6--6. FIG. 6 shows stator winding 64c on stator assembly 50. FIG. 6 also shows wire 54b of winding 64b (not shown in FIG. 6) connected to soldered contact 60b. Wire guide ring 40 holds wire 54b in wire channel 48b. A rotor hub 76 is rotatably carried on drive shaft 56 by bearings. Rotor hub 76 carries magnetic storage disc 8 (shown in FIG. 1). Interaction between stator coils 64 of stator assembly 50 and permanent magnet 70 cause rotor hub 76 to rotate thereby rotating disc 8.

FIG. 6 also shows adhesive 78 which covers stator windings 64. Adhesive 78 acts to rigidly bond stator assembly 50 to motor base 52. In addition to its function as a wire guide, ring 40 acts to block the flow of adhesive 78 beyond the outer circumference of stator assembly 50. This prevents adhesive 78 from interfering with the rotation of rotor hub 76. Adhesive 78 strengthens the structure of stator assembly 50 and motor base 52 thereby increasing its resonant frequency and damping its response. This provides for more stable disc operation and reduces reading and writing errors because vibrations in drive 2.

In one embodiment of the invention, wire guide 40 is removed following the soldering of wires 54 to contacts 60. Following removal of wire guide 40, rotor hub 76 is assembled for normal operation. The use of ring 40 ensures that wires 54 are properly placed over contacts 62 which reduces the required manual labor. Additionally, as the location of wires 54 and contacts 62 are known, the soldering process can be automated thereby further reducing manual labor. This reduction in human interaction decreases the cost of the overall disc drive and improves yields. In a subsequent operation, which could be automated, a flat blade cuts off the end of wire 54 which is between contact 60 and guide ring 40.

In another embodiment of the invention, the guide ring is not removed from the stator assembly and is used as a retaining ring to prevent the flow of an adhesive in which windings 64 of stator assembly 50 are potted. Following application of adhesive 78, it may be possible to remove ring 40. Ring 40 can be used as an adhesive retaining ring whether or not it is also used as a wire guide. The spacing between ring 40 and motor base 52 should be small enough to prevent the flow of adhesive between ring 40 and base 52. This is determined by the type of adhesive used and the viscosity of the adhesive. In a preferred embodiment, the adhesive is Chemseal 4.times.464C. In one embodiment, adhesive 78 comprises a single component acrylic UV cure or epoxy UV cure adhesive available from Chemitech, Inc., of Tokyo, Japan.

In another embodiment of the invention, ring 40 is attached to, or formed from, motor base 52 and used to retain the flow of adhesive 78 beyond the outer rim of stator assembly 50.

FIG. 7 is a cross-sectional view of a disc drive motor 100 in accordance with another embodiment of the invention. Disc drive motor 100 is a "in-hub" type design and shows a drive motor in which the stator wiring connections are not coupled to the base. Motor 100 includes rotor 102 and sleeve 104 which rotatably carries rotor 102. Rotor 102 carries discs 106 and 108, and is rotatably coupled to sleeve 104 through bearings 116 and 118. A stator assembly 110 is carried in motor 100 and interacts with permanent magnet 111 carried on rotor 102 thereby causing the rotation of rotor 102. Stator assembly 110 includes stator winding 112 having a wire which is electrically connected to wiring assembly 120. Typically, wiring assembly 120 is a flexible printed circuit or printed circuit board having a contact similar to contact 62 described above.

In this embodiment of the invention, the wire guide ring operates as described above and fits around stator assembly 110. The retaining ring positions the stator wire adjacent contacts carried in circuit board 120 during soldering of the connection. Once the connection is soldered, the retaining ring is removed and motor 100 is assembled as shown in FIG. 7.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, the invention can by used with different size disc drive assemblies and is not limited to the shapes shown in the figures. Further, the invention can be used in both stationary shaft and rotating shaft motors and "below hub" or "in hub" designs. Additionally, the wires may be connected to any suitable contact or connection other than the desired harness. In the figures, the position of the electrical contact has been illustrated as between the stator windings. However, it is to be understood that the contact could be in any appropriate position relative to the stator assembly, including outside the outer diameter of the stator assembly or inside the inner diameter of the stator assembly in, for example, a stationary shaft-type motor design.