Minebea Kabushiki-kaisha

Minebea Company, Limited

Hiroshi Yoshikawa

Rikuro Obara

Tomoyuki Yasuda

Hiroshi Sakaba

A fluid dynamic bearing having a shaft () and a bearing sleeve () rotatably supported relative to each other. At least one of the shaft and the bearing sleeve is made of steel or stainless steel made of by weight C: 0.6&#x2dc;1.20%; Si: 1.0% or less; Mn: 1.0% or less; Cr: 10.5&#x2dc;18.0%; Mo: 1.0% or less; S.: 0.03% or less; and Fe. The dynamic pressure bearing surface () is formed by ridges () remaining in between multiple dynamic pressure grooves () formed by electrochemical machining.

Fluid dynamic pressure bearing for spindle motors and storage disk drive devices and having ridge portions between grooves in the fluid dynamic pressure bearing

A method and apparatus for forming a fluid dynamic pressure groove in a fluid dynamic pressure bearing is provided. The method is accomplished by initially positioning and securing multiple workpieces to be machined to their respective machining devices. An electrochemical dissolving effect is imparted to each target surface of the multiple workpieces and then at least one fluid dynamic pressure groove is formed on each target surface of the multiple workpieces. Each groove may have a specified shape, dimension and surface condition. An electrolyte is directed from a common electrolyte tank to each of the machining devices used on the multiple workpieces.

Method and device for forming a dynamic pressure-generating groove in a fluid dynamic pressure bearing

In an outer rotor type spindle motor in which a shaft and a stator are supported by and fixed to a flange , damping members and are interposed between the flange and the stator and between the flange and the shaft , or the flange itself is formed of a damping material. Thus, electromagnetic vibration from the stator or rotating vibration from the shaft are damped and absorbed by the damping members and . Accordingly, the generation of vibration or noise in the flange can be prevented which is caused by the transmission of the electromagnetic vibration generated on the stator due to an alternating current supplied to a stator coil or by the transmission of the rotating vibration of a rotor received by the shaft to the flange.

Spindle motor

A spindle motor of the present invention is capable of keeping its ball ( )'s pre-load constant, because a sleeve ( ) is capable of being resiliently deformed due to its resiliency, and therefore capable of constantly keeping a pre-load applied to the balls ( ) from inner and inner ring raceways of inner and outer rings ( ) of ball bearings ( ). In this motor, a rotor hub ( ) has an axial center bore ( ). This bore ( ) is provided with: a large-diameter bore portions in its opposite axial ends; and, a small-diameter bore portion ( ) axially interposed between the large-diameter bore portions. An inner diameter of the small-diameter bore portion ( ) is smaller than an outer diameter of the sleeve ( ). The axial center bore ( ) of the hub ( ) is fitted to an outer peripheral surface of the sleeve ( ) in an insertion manner through a heating shrinkage fit process, so that the sleeve ( ) is subjected to a radially inwardly exerted pressure applied from outside to resiliently deform radially inwardly. As a result, a small-diameter portion ( ) is formed in the sleeve ( ) to extend radially inwardly between the outer rings ( ).

A spindle motor comprising a double row bearing device including a shaft, a sleeve surrounding the shaft, and a pair of upper and lower rows of balls, a cylindrical bearing holder extending upwardly from a base of the spindle motor for accommodating the sleeve within a vertical bore of the holder, and a rotor hub mounted on the shaft for journaling the rotor hub rotatably on the base, the spindle motor is characterized in that a reduced inner diameter portion of an inner diameter smaller than the outer diameter of the sleeve is formed on the inner surface of the bore of the bearing holder between the upper and lower larger inner diameter portions to urge the sleeve inwardly by the reduced inner diameter portion to deform it elastically to form a squeezed portion protruding inwardly of the sleeve between the upper and lower rows of balls.

In the manufacture of a casing base for a hard disc drive device, an elongate semi-product of a light metal having a predetermined sectional profile having opposite side frame portions, is extrusion molded and then cut to a predetermined length to obtain an eventual casing base, which is then formed with necessary holes and recessed or raised portions using a press, thus completing the casing base. Like the case of die casting, no cavities are generated, so that it is possible to readily carry out washing and surface treatment. In addition, unlike the case of forming frames in a sole press process, a large number of press forming steps are not involved, and it is possible to permit mass production of a highly accurate and highly rigid product in a small number of steps and at a low cost of manufacture.

Growing community of inventors

Miyota-machi, Japan

Hiroshi Yoshikawa