A dynamic pressure bearing device includes a rotary shaft, a dynamic pressure bearing member for supporting the rotary shaft, two radial dynamic pressure bearing parts and a thrust dynamic pressure bearing part formed between the dynamic pressure bearing member and the rotary shaft, and a lubricating fluid continuously filled in the two radial bearing parts and the thrust bearing part. A bypass passage for pressure release is provided for communicating across the two radial dynamic pressure bearing parts to flow the lubricating fluid corresponding to the amount of the unbalance caused by the unbalance of the pumping effect forces from a high-pressure side to a low-pressure side through the bypass passage to reduce the unbalance.

Dynamic pressure bearing device

A hydrodynamic bearing apparatus comprises two hydrodynamic bearing sections which have a shaft member, a bearing member fit to the shaft member with a predetermined space therein, lubricants filling the space between the shaft member and the bearing member, and which are separately placed in the axial direction of the shaft member. The lubricants of the two hydrodynamic bearing sections are separated from each other by an air layer. The lubricants are pressured by hydrodynamic generating grooves formed on the hydrodynamic bearing sections such that the shaft member and the bearing member are rotatably supported in relation to each other. The hydrodynamic generating grooves separately formed on the two hydrodynamic bearing sections are formed into an unbalanced shape such that the lubricants are moved in a predetermined direction to correct the slope of the shaft member and the bearing member when rotation is suspended. Capillary sealing sections are formed in continuation to end sections of each of the two hydrodynamic bearing sections to sustain the lubricants by capillarity. The maximum amount of the lubricant in one of the capillary sealing sections, which is located downstream in the moving direction of the lubricants, is established to be larger than the moving amount of the lubricants.

Hydrodynamic bearing apparatus

An improved capillary seal for use with a hydrodynamic bearing is disclosed, which provides a stronger or stiffer seal for a fluid dynamic bearing motor which is open at both ends, and is used with top cover attached motors utilizing fluid dynamic bearings. The design of the capillary seal uses centrifuigal force to actively push the oil back into the FDB while it is spinning, combined with the capillary tension which holds oil in the FDB during stationary periods. Also, the seal design comprises two walls which converge toward an apex near an adjacent fluid dynamic bearing. This design allows air, trapped within the seal and the associated FDB, to be expelled, eliminating air bubbles from the fluid dynamic bearing.

Centrifugal capillary seal for use with fluid dynamic bearings

A dynamic pressure bearing is provided in which leakage of liquid lubricant due to precession of a housing can be prevented from occurring. In the dynamic pressure bearing, the inner diameter of a tapered inner peripheral face 20 of the housing 1 which constitutes a capillary sealing portion 23 is gradually increased as moving from an opening 17 toward the inner area in the axial direction. When the housing 1 is rotated, therefore, a centrifugal force applied on liquid lubricant existing on the tapered inner peripheral face 20 acts in the direction along which the liquid lubricant is pushed toward the inner area, as indicated by an arrow 19 . Consequently, the centrifugal force which is due to precession of the housing 1, and which pushes the liquid lubricant 15 toward the outside as indicated by an arrow 29 can be cancelled by the force acting in the direction toward the inner area, with the result that leakage of the liquid lubricant due to precession of the housing 1 can be prevented from occurring.

Dynamic pressure bearing

In a hydrodynamic pressure bearing according to the present invention, the lubricating fluid held in the radial bearing portion is pumped toward the thrust bearing portion by grooves formed in the radial bearing portion. And the hydrodynamic pressure bearing is provided with a circumferential groove formed in the vicinity of the boundary region between the radial and thrust bearing portions so as to control the flow of lubricating fluid between the bearing portions depending on the amount of lubricating fluid held therein. The circumferential groove is formed on the sleeve member near the inner opening of a communicating hole which in turn axially passes through the thrust plate and communicates the gap defined by the shaft and the sleeve member therebetween with the external atmosphere. While a predetermined amount of lubricating fluid is retained in the gap, some extra lubricating fluid is also retained in the vicinity of the inner opening of the communicating hole. As the lubricating fluid is reduced by evaporation or other factors, air enters the gap through the communicating hole by the effect of atmospheric pressure. The air is retained near the circumferential groove and separates the lubricating fluid into the radial bearing portion and the thrust bearing portion. As a result, the flow of the lubricating fluid is interrupted.

Hydrodynamic pressure bearing

An electric motor construction includes a rotor housing and sleeve which surrounds a shaft/thrust plate. The thrust plate is enclosed in a dead end cavity and is surrounded by a fluid which forms a fluid bearing. The shaft has asymmetrical grooves which create a net pressure gradient from a capillary seal formed near the bottom of the shaft toward the dead end cavity. This helps maintain the capillary seal and reduce the risk of cavitation.

Fluid bearing with asymmetrical groove pattern

A construction for a fluid bearing in a rotary spindle apparatus includes a spindle having first and second ends, and at least one thrust plate coupled to a shaft which is surrounded by a hub having an enclosing sleeve. The sleeve surrounding the thrust plate and shaft defines several gap regions where bearing fluid resides. A first radial gap region is defined between the shaft and sleeve and a second radial gap region is defined between the outer diameter of the thrust plate and the sleeve. A first axial gap region is defined by an upper surface of the thrust plate and the sleeve, and a second axial gap region exists between the lower surface of the thrust plate and the sleeve. A bearing fluid is disposed within these gap regions and forms capillary seals at first and second ends of the spindle. The thrust plate includes holes or pressure compensation ports which connect the first and second axial gap regions. The pressure compensation ports allow the bearing fluid to flow between the upper and lower thrust plate surfaces so that ambient pressure is maintained near the inner diameter of the thrust plate.

Fluid bearing construction employing thrust plate with pressure compensation ports

In embodiments of the present invention, an optical device tester performs stressed eye testing on several optical receivers and transmission and dispersion penalty testing on optical transmitters at a variety of data rates wavelengths using single mode optical signals and multimode optical signals using a variety of supply voltages and temperatures.

Optical transceiver tester

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Fluid bearing with asymmetrical groove pattern

Fluid bearing construction employing thrust plate with pressure compensation ports

Optical transceiver tester