Rotor hub, spindle motor and hard disk drive
AssigneesNidec Corporation, Tokusen Kogyo Co., Ltd., Kent Engineering
InventorsToshiaki Miyauchi, Yasuo Yamamoto
Life of this patent
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Abstract
In a method for manufacturing a rotor hub for use in a spindle motor, free-cutting stainless steel is used as a material of the rotor hub. A slug of free-cutting stainless steel is subjected to a plastic working to form a disk mounting portion and a cylindrical surface positioned radially inwardly of the disk mounting portion. Then, a cylindrical disk fitting surface is formed by machining substantially the entirety of the cylindrical surface. The rotor hub contains A-type inclusions appearing in a cross section taken along a center axis of the disk mounting portion. The A-type inclusions are oriented in directions different than the center axis.
Claims22
A rotor hub, for use in a hard disk drive spindle motor, comprising:
- an annular disk mounting portion having a center axis and a disk mounting surface formed on one side of the disk mounting portion along the center axis;
- and
- a disk fitting portion having a cylindrical disk fitting surface positioned radially inwardly of the disk mounting surface,
- wherein the rotor hub is a single seamless part made of free-cutting stainless steel and contains A-type inclusions appearing in a cross section taken along the center axis, the A-type inclusions being oriented in directions different than the center axis, the orientation of the inclusions differing from place to place on the cross section, the cylindrical disk fitting surface being machined substantially in its entirety.
A method for manufacturing a rotor hub which is used in a hard disk drive spindle motor, the method comprising:
- a raw material preparation step for preparing a bar of free-cutting stainless steel;
- a slug preparation step for cutting the bar into a specified length to obtain a slug;
- a plastic working step for subjecting the slug to a plastic working to form a disk mounting portion and a cylindrical surface positioned radially inwardly of the disk mounting portion;
- and
- a disk mounting surface forming step for machining substantially the entirety of an annular surface of the disk mounting portion into a disk mounting surface.
Dependencies are inferred from the claim text.