Clamp ring and disc drive having the same

Abstract

A clamp ring that clamps a disc onto a spindle motor that rotates the disc includes an annular disc shaped body fixed onto a hub that rotates with a shaft of the spindle motor, the body arranging plural screw holes in a circumferential direction of the body, a screw that fixes the body onto the hub being inserted into each screw hole, wherein the body arranges plural stress relaxation holes between the plural screw holes so that each stress relaxation hole and each screw hole alternate in the circumferential direction of the body, each stress relaxation hole mitigating a deformation of the body in fixing the body onto the hub with the screw, a diameter of the stress relaxation hole being equal to or greater than a diameter of the screw hole in a surface of the body from which the screw is inserted into the body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an internal structure of a hard disc drive (“HDD”) according to one embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a magnetic head part in the HDD shown in FIG. 1.

FIG. 3 is a partially sectional and perspective view near a spindle motor shown in FIG. 1.

FIG. 4A is a perspective view of a clamp ring viewed from the upper side according to this embodiment. FIG. 4B is a perspective view of a clamp ring viewed from the lower side according to this embodiment.

FIG. 5 is a schematic sectional view of a pre-screwed clamp ring.

FIG. 6 is a graph for explaining effects of the clamp ring according to this embodiment.

FIG. 7A is a perspective view of a clamp ring viewed from the upper side which has small stress relaxation holes. FIG. 7B is a perspective view of a clamp ring viewed from the upper side which has large stress relaxation holes. FIG. 7C is a perspective view of a clamp ring that has screw holes but no stress relaxation hole.

FIG. 8 is a graph that investigates changes of the undulation sixth order component or sixth harmonics applied to the clamp ring by changing a stress relaxation hole condition and a fastening condition.

FIG. 9A is a schematic perspective view of an analysis model for explaining a relationship among the diameter, the center position, the thickness of the stress relaxation hole, and the undulation reduction effect. FIG. 9B is a graph as an analysis result.

FIG. 10 is a block diagram of a control system of a HDD shown in FIG. 1.

Claims

1. A clamp ring that clamps a disc onto a spindle motor that rotates the disc, said clamp ring comprising an annular disc shaped body fixed onto a hub that rotates with a shaft of the spindle motor, said body arranging plural screw holes in a circumferential direction of said body, a screw that fixes said body onto the hub being inserted into each screw hole, wherein said body arranges plural stress relaxation holes between the plural screw holes so that each stress relaxation hole and each screw hole alternate in the circumferential direction of said body, each stress relaxation hole mitigating a deformation of said body in fixing said body onto the hub with the screw, a diameter of the stress relaxation hole being equal to or greater than a diameter of the screw hole in a surface of said body from which the screw is inserted into said body.

2. A clamp ring according to claim 1, wherein the diameter of the stress relaxation hole is 1.11 times or greater as large as the diameter of the screw hole in the surface of said body.

3. A clamp ring according to claim 1, wherein the diameter of the stress relaxation hole is 1.14 times or greater as large as the diameter of the screw hole in the surface of said body.

4. A clamp ring according to claim 1, wherein said body has six screw holes and six stress relaxation holes, and the diameter of the screw hole is 3.5 mm.

5. A clam ring according to claim 1, wherein a circle that passes centers of the plural stress relaxation holes is greater than a circle that passes centers of the plural screw holes.

6. A clamp ring according to claim 1, wherein said clamp ring further includes an annular disc pressure portion that is provided onto said body and presses the disc, the stress relaxation holes being located inside the disc pressure portion.

7. A disc drive comprising a clamp ring according to claim 1.

8. A clamp ring that clamps a disc onto a spindle motor that rotates the disc, said clamp ring comprising an annular disc shaped body fixed onto a hub that rotates with a shaft of the spindle motor, said body arranging plural screw holes in a circumferential direction of said body, a screw that fixes said body onto the hub being inserted into each screw hole, wherein said body arranges plural stress relaxation holes between the plural screw holes so that each stress relaxation hole and each screw hole alternate in the circumferential direction of said body, each stress relaxation hole mitigating a deformation of said body in fixing said body onto the hub with the screw, an area of the stress relaxation holes being equal to or greater than an area of the screw holes in a surface of said body from which the screw is inserted into said body.

9. A clamp ring according to claim 8, wherein an area of each stress relaxation hole is greater than an area of each screw hole.

10. A clamp ring according to claim 8, wherein a gross area of the stress relaxation holes is greater than a gross area of the screw holes.

11. A disc drive comprising a clamp ring according to claim 8.