A rolling bearing includes an inner ring, an outer ring, rolling elements, and a retainer that holds the rolling elements. The retainer includes a metal portion and a sliding resin portion The metal portion has communication holes each having a plurality of openings on the surface of the metal portion, and the sliding resin portion is disposed in the communication holes.

A rolling bearing includes an inner ring, an outer ring, rolling elements, and a retainer that holds the rolling elements. The retainer includes a metal portion and a sliding resin portion The metal portion has communication holes each having a plurality of openings on the surface of the metal portion, and the sliding resin portion is disposed in the communication holes.

A bearing system for a rotating vertical shaft includes a first ball bearing, having a first pitch diameter and a first axial stiffness and a second ball bearing having a second pitch diameter and a second axial stiffness. The first ball bearing is a deep groove Conrad bearing. The second ball bearing is an angular contact bearing. The first and second ball bearings are coaxial, secured to one another and rotatable together. The first pitch diameter is at least 1.5 times greater than the second pitch diameter. The bearing system has an axial stiffness ratio defined by the first axial stiffness divided by the second axial stiffness. The axial stiffness ratio is based on an axial preload force applied to the second outer ring such that an operating torque of the bearing system is within a predetermined range at temperatures from minus 40 to positive 85 degrees Celsius.

A turbomachine according to an embodiment of the present disclosure may include a rotary shaft, a magnetic bearing including a core body configured to surround the rotary shaft, a plurality of poles radially extending from an inner surface of the core body toward the rotary shaft, and coils wound around the plurality of poles to levitate the rotary shaft by using a magnetic force generated by a magnetic field formed by applied electric current, a sleeve journal bearing disposed between the rotary shaft and the magnetic bearing so as to surround the rotary shaft and configured to levitate the rotary shaft by generating a dynamic pressure when the rotary shaft rotates, and a permanent magnet disposed between the plurality of poles and configured to support the rotary shaft by using a magnetic force.

A bearing system for a rotating vertical shaft includes a first ball bearing, having a first pitch diameter and a first axial stiffness and a second ball bearing having a second pitch diameter and a second axial stiffness. The first ball bearing is a deep groove Conrad bearing. The second ball bearing is an angular contact bearing. The first and second ball bearings are coaxial, secured to one another and rotatable together. The first pitch diameter is at least 1.5 times greater than the second pitch diameter. The bearing system has an axial stiffness ratio defined by the first axial stiffness divided by the second axial stiffness. The axial stiffness ratio is based on an axial preload force applied to the second outer ring such that an operating torque of the bearing system is within a predetermined range at temperatures from minus 40 to positive 85 degrees Celsius.

A drive system as disclosed includes an input shaft, an output shaft, and at least two coupling elements respectively coupled to the input shaft and the output shaft. In order to absorb assembly and manufacturing tolerances with respect to the shafts, the coupling elements and their attachment to the shafts and thereby prevent jamming of the drive system, at least one coupling element has an elastically deformable section, the elastically deformable section having a different material or a different cross-section than an adjacent section of the coupling element.

A bearing test apparatus for testing a test bearing, including a chamber, a bearing cap disposed in the chamber and coupled to an outer wheel of the test bearing, a driving shaft connected to an inner wheel of the test bearing to rotate the inner wheel, an extension arm extending in a radial direction of the bearing cap from the bearing cap to expose one end thereof out of the chamber, and a measurement arm configured to make a contact with one end of the extension arm and configured to be rotatable by the extension arm. When a rotation force is applied to the bearing cap by the outer wheel, the extension arm is used to measure a force applied to the measurement arm, which is used to obtain an exclusive torque of the test bearing.

A bearing test apparatus for testing a bearing (hereinafter, referred to as a test bearing) has a chamber, a bearing cap disposed in the chamber and coupled to an outer wheel of the test bearing, a driving shaft connected to an inner wheel of the test bearing to rotate the inner wheel, an extension arm extending in a radial direction of the bearing cap from the bearing cap to expose one end thereof out of the chamber, and a measurement arm configured to make a contact with one end of the extension arm and configured to be rotatable by the extension arm, wherein an exclusive torque of the test bearing is obtained by measuring a force applied to the measurement arm by the extension arm when a rotation force is applied to the bearing cap by the outer wheel.

A cage includes: an annular body having pocket holes for receiving balls; and a resin portion formed through injection molding of a resin containing a solid lubricant with the body being set as an insert component. The resin portion includes: first parts formed along inner peripheral surfaces of the pocket holes of the body to form pocket surfaces to be held in sliding contact respectively with the balls; and a second part formed along an outer peripheral surface (or inner peripheral surface) of the body to form a guide surface to be held in sliding contact with an outer ring (or inner ring). The first parts and the second part are formed integrally with each other. Weld lines of the resin portion are formed at positions of avoiding exposure of the weld lines at both end portions of the pocket surfaces in a cage circumferential direction.

A lubricant fluid comprising a base oil, which utilizes carboxylic esters of carboxyl di-end-capped-polyethylene glycols, or a mixture thereof, to have ultra-low viscosity, high flash point, high viscosity index (VI), excellent low temperature properties (viscosity and pour/freeze points), and low elastohydrodynamic (EHD) shear strength, and to enable the production of high efficiency fluids with enhanced temperature properties for machines or machine elements that operate in the elastohydrodynamic regime of lubrication.