Ntn Corporation

Jun Hirade

Tetsuya Kurimura

Kimihiko Bito

Tetsuya Yamamoto

Fuminori Satoji

Natsuhiko Mori

Isao Komori

Masaharu Hori

Yasuhiro Yamamoto

Shinji Komatsubara

Kimihiko Bitou

Kazuto Shimizu

Kazuyoshi Harada

Tatsuya Hayashi

Toshiaki Niwa

Mikihisa Fujiwara

Yukitaka Hayakawa

Masashi Yamagou

Shouhei Oka

Shuichi Komatsu

A fluid dynamic bearing deviceincludes: a shaft member; a bearing sleevethat has the shaft memberinserted into the inner periphery thereof; a housingthat holds the bearing sleeveon the inner periphery thereof and has a bottomed cylindrical shape having an opening at an end portion on one axial side; and a seal memberprovided at the opening of the housing. The seal memberhas a disk portiondisposed on one axial side of the bearing sleeve, and a protrusion (cylindrical portion) protruding to the other axial side from an outer diameter end of the disk portion. An outer peripheral surfaceof the seal memberis fixed to an inner peripheral surfaceof the housing

Fluid dynamic bearing device

A shaft member for a fluid bearing device includes, on an outer peripheral surface thereof, two bearing surfaces (and) separated from each other in an axial direction, and a middle relief portion () formed between the bearing surfaces (and) and having a diameter smaller than a diameter of the bearing surfaces. The middle relief portion () includes a cylindrical surface portion () having a ground surface, and stepped portions () arranged on both axial sides of the cylindrical surface portion and having a diameter difference from the cylindrical surface portion.

Shaft member for fluid bearing device, manufacturing method therefor, and fluid bearing device

Grinding is performed on an outer peripheral surface of a shaft member while rotationally driving the shaft member under a state in which both end surfaces of the shaft member are sandwiched between a pair of support portions. A convex surface is formed on one axial end surface of the shaft member or an end surface of one of the pair of support portions, and a flat surface is formed on the other of the one axial end surface of the shaft member and the end surface of the one of the pair of support portions. The flat surface and an apex of the convex surface are brought into contact with each other to support one axial end portion of the shaft member.

Shaft member for fluid dynamic bearing device and manufacturing method for shaft member

Providing a fluid dynamic bearing device, wherein the outer member comprises a member formed by a pressing process on a plate member, the radial bearing surface and at least the one of the thrust bearing surfaces of the outer member being formed by the pressing process, and wherein at least a part of the inner member, which forms the radial bearing surface and the thrust bearing surfaces of the inner member, is made of a sintered metal.

Fluid dynamic bearing device and assembly method for same

A shaft member is provided with a shaft portion and a flange portion coupled with a lower end surface of the shaft portion. The shaft portion is formed into a complete circular shape in cross section, and the flange portion is provided with a through-hole in which a part of a circumferential region is retracted to a radially outer side with respect to a lower end of the shaft portion so as to exhibit a non-circular shape. The shaft portion and the flange portion are coupled with each other in a state of butting the lower end surface of the shaft portion and an upper end surface of the flange portion against each other. With this, a fluid path is formed by opening both end surfaces of the flange portion.

To manufacture a shaft member, which is excellent in both accuracy and strength at low cost, a shaft member () includes a shaft portion () and a flange portion () provided to one end of the shaft portion (). The flange portion () has an annular shape, and the shaft portion () and the flange portion () are fixed by a welded portion (), which is formed by applying a laser beam () to an upper end of an inner periphery thereof.

A shaft portion is press-fitted to a flange portion, and a plastic working portion of a first jig is pressed against an upper end surface of the flange portion, whereby the flange portion is partially subjected to plastic deformation toward an inner peripheral side. With this, a caulked portion is formed between the flange portion and the shaft portion. Further, press-fitting and caulking are performed in a state in which both end surfaces of the flange portion are bound by a second jig and a third jig.

Shaft member for fluid bearing device and method of producing the same

In order to prevent degradation of accuracy and decrease of strength when a hydrodynamic bearing device is assembled and to reduce a cost of the hydrodynamic bearing device, a guide face serving as a guide when a disc hub is press fitted into a shaft member is formed on the shaft member. Then, the guide face, an outer circumferential surface of the shaft member adjacent to the guide face, and a boundary portion between the guide face and the outer circumferential surface are ground simultaneously, thereby forming a blunting portion having a radius r in the boundary portion. Thus, no edge remains between the guide face and the outer circumferential surface. Therefore, press-fitting resistance when the disc hub is press fitted to an end of the shaft member can be reduced.

Growing community of inventors

Kuwana, Japan

Jun Hirade