Vacuum pump comprising a housing, a rotor shaft disposed in the housing, at least one bearing rotatably supporting the rotor shaft against the housing including an inner race in contact with the rotor shaft and an outer race in contact with the housing, and an axial spring applying an axial force onto the outer race, wherein a bearing ring is disposed between the axial spring and the outer race, the bearing ring applying a clamping force to the housing.

A double-row rolling-element bearing unit of a medical pump, preferably syringe pump, has a bearing core forming a first inner running surface for first rolling elements, which first inner running surface faces in an axial direction, and forms a second inner running surface for second rolling elements, which second inner running surface is arranged oppositely to the first inner running surface in the axial direction. The pump has a bearing bush, which can be mounted on a housing portion and forms a first outer running surface, which lies opposite the first inner running surface, and the pump has a bearing pan, which forms a second outer running surface, which lies opposite the second inner running surface. At least one preloading element couples the bearing pan to the bearing bush with a defined preload to join the double-row rolling-element bearing unit as a unit.

In a housing that supports a rotating shaft via a rolling bearing which is subjected to predetermined position precompression, a wedge member, the radial thickness of which increases from the leading end towards the base end thereof, is inserted between the housing and the outer circumferential surface of the outer race of the rolling bearing and between the rotating shaft and the inner circumferential surface of an inner race of the rolling bearing, the wedge member being inserted from the leading end thereof along the radial direction of the rotating shaft. The wedge member is fixed by being fastened, ahead in the insertion direction, by bolts and nuts, so that precompression force along with predetermined position precompression is imparted to the rolling bearing.

In a housing that supports a rotating shaft via a rolling bearing which is subjected to predetermined position precompression, a wedge member, the radial thickness of which increases from the leading end towards the base end thereof, is inserted between the housing and the outer circumferential surface of the outer race of the rolling bearing and between the rotating shaft and the inner circumferential surface of an inner race of the rolling bearing, the wedge member being inserted from the leading end thereof along the radial direction of the rotating shaft. The wedge member is fixed by being fastened, ahead in the insertion direction, by bolts and nuts, so that precompression force along with predetermined position precompression is imparted to the rolling bearing.

A system for an unmanned aerial vehicle can include an altitude control system, which further includes a compressor assembly, a valve assembly, and an electronics assembly. The compressor assembly may include a driveshaft and a bearing assembly configured to rotate the driveshaft. The driveshaft may be formed from a first material and a compressor housing may be formed from a second material. The first and second materials may have different rates of thermal expansion. A dynamic preloading mechanism, such as a flexible plate, may be provided within the compressor assembly to exert a preloading force on the bearing assembly. Throughout the duration of the flight of the unmanned aerial vehicle, the preloading mechanism can continually compensate for differences in rates of thermal expansion between the first and second materials throughout.

A bearing assembly includes at least two bearings each having an inner ring and outer ring, the inner rings being mounted on a shaft, and a balancing piston being disposed between the two bearings. The balancing piston includes a first part and a second part, the first and second parts each contacting the outer rings of the two bearings in an axial direction. The balancing piston further includes an inlet for directing a pressure fluid between the first and second parts to provide pressure to the first and second parts such that the balancing piston adjusts or exerts axial force on at least one of the two bearings. The balancing piston includes an outlet for directing the pressure fluid to lubricate at least one of the two bearings. Also, the outer diameter of the balancing piston is greater than the outer diameter of the outer rings of the two bearings.

A bearing assembly includes at least two bearings each having an inner ring and outer ring, the inner rings being mounted on a shaft, and a balancing piston being disposed between the two bearings. The balancing piston includes a first part and a second part, the first and second parts each contacting the outer rings of the two bearings in an axial direction. The balancing piston further includes an inlet for directing a pressure fluid between the first and second parts to provide pressure to the first and second parts such that the balancing piston adjusts or exerts axial force on at least one of the two bearings. The balancing piston includes an outlet for directing the pressure fluid to lubricate at least one of the two bearings. Also, the outer diameter of the balancing piston is greater than the outer diameter of the outer rings of the two bearings.

Only an outer spacer (33) is cooled by an outer spacer cooling structure, thereby causing a temperature difference between an inner spacer (32) and the outer spacer (33). According to this temperature difference, an inner ring (37) of a bearing (31) is displaced relatively to an outer ring (38) in a direction in which a preload inside the bearing (31) decreases.

Only an outer spacer (33) is cooled by an outer spacer cooling structure, thereby causing a temperature difference between an inner spacer (32) and the outer spacer (33). According to this temperature difference, an inner ring (37) of a bearing (31) is displaced relatively to an outer ring (38) in a direction in which a preload inside the bearing (31) decreases.

An amount of decrease ΔC in an axial clearance of a hub unit bearing is found based on an amount of expansion ΔD of an inner ring of the hub unit bearing, which is the difference between the outer-diameter dimension D1 of the inner ring after the inner ring is externally fitted with a tubular fitting portion of a hub spindle of the hub unit bearing and after formation of a swaged portion of the hub spindle, the inner ring being held between the swaged portion and a stepped surface of the hub spindle, and an outer-diameter dimension D0 of the inner ring before the inner ring is externally fitted with the tubular fitting portion.