Ntn Corporation

Masaaki Toda

Masaharu Hori

Isao Komori

Tetsuya Yamamoto

Kenji Hibi

Kenji Ito

Kiyoshige Yamauchi

Nobuyoshi Yamashita

Isamu Yoshida

Kimihiko Bitou

Morihisa Yoshioka

Yoshiharu Inazuka

Koji Tateishi

Itsuo Murata

Masaya Soeda

A gap width out of the radial bearing gap is axially differed; a narrow width part which has a relatively smaller gap width in the radial bearing gap is arranged on the side relatively closer to a barycentric position of the rotating body, and a wide width part which has a relatively larger gap width in the radial bearing gap is arranged on a side relatively distant from the barycentric position of the rotating body; and a region facing at least the radial bearing gap of the bearing member is formed to an electroformed part made of deposited metal.

Fluid dynamic bearing device

Provided is a fluid dynamic bearing device in which an assembly of a bearing sleeve to a housing is facilitated and which has excellent moment rigidity. A fluid dynamic bearing device () includes radial bearing parts (Rand R) and thrust bearing parts (Tand T). Thrust bearing surfaces (C and D) are respectively provided to first and second step surfaces (and) of a housing (), and the thrust bearing parts (Tand T) are respectively formed between the thrust bearing surfaces (C and D) and end surfaces (and) of seal members (and) provided while protruding to an outer diameter side of a shaft member ().

Fluid dynamic bearing device and method of manufacturing the same

A fluid dynamic bearing device includes a bearing sleeve including a radial bearing surface, a shaft member to be inserted to an inner circumference of the bearing member, and a radial bearing part for non-contact supporting the shaft member in a radial direction by a dynamic pressure action of a fluid generated in a radial bearing gap between the radial bearing surface of the bearing member and an outer circumferential surface of the shaft member. Additionally, a plurality of bearing sleeves are axially arranged, and each bearing sleeve is formed having different axial length with respect to one another.

A fluid dynamic bearing device includes a housing injection molded with a bearing sleeve as an insert. Accordingly, the molding of the housing and the assembly of the housing and the bearing sleeve can be performed in a single step. In addition to this, by simply increasing the die precisions the housing and the bearing sleeve can be fixed easily with high precision. Since the housing is opened at both ends, it is possible to sandwich the bearing sleeve, and accordingly, the bearing sleeve can be accurately positioned inside the dies with reliability.

To provide a fluid dynamic pressure bearing device that achieves high rigidity against moment without degradation in assembly precision and bearing performance, bearing sleeves are arranged in an axial direction and coaxiality of radial bearing surfaces formed on inner peripheral surfaces of the bearing sleeves is set to 3 &#x3bc;m or less. This secures width precision between the radial bearing gaps to prevent a degradation in bearing performance and a failure such as wear etc. caused by contact between a shaft member and the bearing sleeves. Further, a first radial bearing surface and a second radial bearing surface are provided on at least one sleeve, and this allows a sleeve assembly constructed from the bearing sleeves to be supported at least three positions in the axial direction in a process of assembling the sleeve assembly. As a result, assembly work can be carried out with two bearing sleeves prevented from being bent at a midway thereof, and highly accurate coaxiality between both the bearing sleeves is secured.

Fluid dynamic bearing device and manufacturing method therefor

A fluid dynamic bearing unit is provided which has a high load capacity against a moment load, whose bearing sleeves can be manufactured and fixed easily, and which can provide a required fixing power. The bearing sleeve is inserted into an inner periphery of a housing, and its bottom end is fixed to the top end of a spacer part with an adhesive. Another bearing sleeve is inserted into another part of the inner periphery of the housing, and its top end is fixed to the bottom end of the spacer part with an adhesive.

Fluid dynamic bearing unit

The fluid dynamic bearing device includes a housing, two bearing sleeves fixed to the housing at positions axially spaced apart from each other, and a shaft member inserted along inner peripheries of the bearing sleeves. The housing includes a spacer portion protruding further radially inwardly than inner peripheral surfaces to which the bearing sleeves are fixed. An axial fluid path is formed in the spacer portion, and the axial fluid path communicates to flow paths formed by axial grooves of the bearing sleeves.

An electrically powered steering device comprises a ball screw mechanism for transmitting a steering force from a steering wheel to steerable vehicle wheels. The ball screw mechanism includes a rotary nut having a nut body in which a circulating passage is formed so as to extend axially thereof, and end caps and secured respectively to opposite ends of the nut body . Each of the end caps and has defined therein respective guideways and for balls that communicate opposite ends of the circulating tunnel with a ball rolling passage . The end caps and and the nut body are made of a sintered alloy. The nut body has an outer periphery of one end thereof that is axially progressively reduced in diameter to define a tapered surface.

Growing community of inventors

Kuwana, Japan

Masaaki Toda