A motor bearing system has: a slide bearing operable as a gas-lubricated bearing by gas supplied from a pump; a rolling bearing; a switching mechanism switching between the slide bearing and the rolling bearing; and a controller. When a motor rotation speed is lower than a first speed, the controller controls the switching mechanism to apply the rolling bearing. When the motor rotation speed is equal to or higher than the first speed and lower than a second speed, the controller controls the switching mechanism to apply the slide bearing and controls the pump to operate the slide bearing as a gas-lubricated bearing. When the motor rotation speed is equal to or higher than the second speed, the controller controls the switching mechanism to apply the slide bearing and stops the pump.

A hydrodynamic bearing for accommodating and supporting a rotating element includes an unloaded sliding surface, a loaded sliding surface downstream of the unloaded sliding surface, a first injection pocket arranged within the unloaded sliding surface and a second injection pocket arranged within the loaded sliding surface. A radial recess arranged within the unloaded sliding surface and the loaded sliding surface extends in a circumferential direction such as to overlap the first and second injection pockets in the circumferential direction upstream and downstream. The radial recess defines or delimits an active area of the unloaded and loaded sliding surfaces. Each of the first and second injection pockets has an axial length which is smaller than an axial extension of the active area upstream or downstream in a corresponding circumferential sliding section of the unloaded sliding surface and loaded sliding surface in which the first and second injection pockets respectively are arranged.

A journal shaft for a journal bearing assembly of an aircraft engine includes a shaft body extending along a longitudinal axis. The shaft body has a radially outer surface and a radially inner surface radially spaced apart from the longitudinal axis to define an inner cavity. An oil pocket is defined in the radially outer surface. One or more passages extend through the shaft body from the radially inner surface to the oil pocket to provide fluid communication between the inner cavity and the oil pocket. The oil pocket includes a radially inner base surface and interconnecting transition surfaces extending between the radially inner base surface of the oil pocket and the radially outer surface of the shaft body. The interconnecting transition surfaces form a fluid-dynamically smooth and edgeless transition to the radially outer surface of the journal shaft.

[Problem] To provide a linear motion device using a highly reliable and environmentally friendly separator that improves a dimensional stability, ductility, and adhesion of greases based on poly-?-olefin oil, which are required for separators, and also prevents deformation at high speeds.

[Solution] Provided is a linear motion device including a linear motion body (15) that is fitted onto a screw shaft (11) and moves straight along the screw shaft (11), a large number of balls (B) held in a ball groove (14) formed on an inner surface side of the linear motion body (15) and rolling between the ball groove (14) and the screw shaft (11), a separator (100) interposed 10 between each ball (B), a circulation passage (18) formed in the linear motion body (15) and circulating the ball (B) from one end side of the ball groove (14) to the other end side, where at least one of the separator (100) and the circulation passage (18) is formed from polyamide 410 by injection molding.

A method for chipless machining of a surface region of a rolling-element bearing ring includes rotating the rolling-element bearing ring relative to a first tool having a first tool tip and a second tool having a second tool tip, positioning the first and second tool tips at start positions at first and second opposite axial ends of the surface region, and moving the first and second tools in opposite axial directions such that the first tool tip follows a first helical or spiral path on the surface region and the second tool tip follows a second helical or spiral path on the surface region, the first and second paths crossing at multiple points within an overlap region located between axial ends of the surface regions.

An exhaust gas turbocharger may include a bearing housing and a rotor. The rotor may have a shaft mounted in the bearing housing via two radial bearing bushes. Each radial bearing bush may have an inner surface facing the shaft. The inner surface may have a single chamfer, where the single chamfers of the two radial bearing bushes face one another, or two chamfers, where one of the two chamfers for each of the two radial bearing bushes facing one another are larger than the other of the two chamfers for each of the two radial bearing bushes facing away from one another.

Gearboxes for aircraft gas turbine engines, in particular arrangements for journal bearings such gearboxes, and related methods of operating such gearboxes and gas turbine engines. A gearbox for an aircraft gas turbine engine includes: a sun gear; a plurality of planet gears surrounding and engaged with the sun gear; and a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin.

A resin composition for a sliding member includes 75% to 97% by mass of a polyacetal resin; and, as additives, 2% to 20% by mass of an ultra-high-molecular-weight polyethylene resin, 0.01% to 3% by mass of a copolymer of ethylene and ,-unsaturated carboxylic acid, and 0.5% to 3% by mass of a lubricant.

A tribologically modified polyoxymethylene polymer composition is disclosed. The polyoxymethylene polymer composition is comprised of a polyoxymethylene polymer and at least one tribological modifier. The tribological modifier may comprise an ultra-high molecular weight silicone having a kinematic viscosity of greater than 100,000 mm.sup.2 s.sup.1. When tested against itself, the composition of the present disclosure exhibits an extremely low dynamic coefficient of friction and produces no discernible noise over a very broad temperature range, such as from 20 C. to 60 C.

A hydrodynamic bearing for accommodating and supporting a rotating element includes an unloaded sliding surface, a loaded sliding surface downstream of the unloaded sliding surface, a first injection pocket arranged within the unloaded sliding surface and a second injection pocket arranged within the loaded sliding surface. A radial recess arranged within the unloaded sliding surface and the loaded sliding surface extends in a circumferential direction such as to overlap the first and second injection pockets in the circumferential direction upstream and downstream. The radial recess defines or delimits an active area of the unloaded and loaded sliding surfaces. Each of the first and second injection pockets has an axial length which is smaller than an axial extension of the active area upstream or downstream in a corresponding circumferential sliding section of the unloaded sliding surface and loaded sliding surface in which the first and second injection pockets respectively are arranged.