A main shaft device is attached to a work machine. The main shaft device is provided with a main shaft that supports a tool or a workpiece, and a main shaft motor that causes the main shaft to rotate. The main shaft device is provided with bearings that are rolling bearings which support the main shaft in an inner race, and a housing and a rear housing that secure an outer race of the bearings. The housing and the rear housing are formed of a material having a coefficient of thermal expansion greater than that of the main shaft.

An air journal bearing for a rotatable shaft of a turbomachine includes a journal sleeve having an inner cylindrical surface and a central axis defining longitudinal and radial directions, a top foil disposed radially inboard of the journal sleeve and configured to receive the rotatable shaft, and a bump foil disposed between the top foil and the journal sleeve and configured to bias at least a portion of the top foil against an outer surface of the rotatable shaft. At least one of the bump foil and a radially extending segment of the top foil is formed contiguous with the inner cylindrical surface. The journal sleeve, the top foil and the bump foil may be formed as a single piece made of selectively sintered ceramic-metal powder.

A connection element providing a first ring and a second ring, the two rings rotating relative to one another about a central axis, the first ring having a contact portion with a contact surface interacting with the second ring for the relative rotation, and a fastening portion configured to be rigidly secured to a support. The contact portion is made of a first material and the fastening portion is made of a second material, different to the first material, the first material having a hardness strictly greater than that of the second material, and the second material having a structural fatigue strength strictly greater than that of the first material.

An air journal bearing for a rotatable shaft of a turbomachine includes a journal sleeve having an inner cylindrical surface and a central axis defining longitudinal and radial directions, a top foil disposed radially inboard of the journal sleeve and configured to receive the rotatable shaft, and a bump foil disposed between the top foil and the journal sleeve and configured to bias at least a portion of the top foil against an outer surface of the rotatable shaft. At least one of the bump foil and a radially extending segment of the top foil is formed contiguous with the inner cylindrical surface. The journal sleeve, the top foil and the bump foil may be formed as a single piece made of selectively sintered ceramic-metal powder.

A main shaft device is attached to a work machine. The main shaft device is provided with a main shaft that supports a tool or a workpiece, and a main shaft motor that causes the main shaft to rotate. The main shaft device is provided with bearings that are rolling bearings which support the main shaft in an inner race, and a housing and a rear housing that secure an outer race of the bearings. The housing and the rear housing are formed of a material having a coefficient of thermal expansion greater than that of the main shaft.

A sliding member includes a back-metal layer and a sliding layer on the back-metal layer, and the sliding layer has a sliding surface. The sliding layer includes a synthetic resin and fibrous particles dispersed in the synthetic resin. A volume ratio of the fibrous particles in the sliding layer is 1 to 15%, and the fibrous particles are made of semi-graphite having a nano indenter hardness of 1000 to 5000 MPa. An average aspect ratio of the fibrous particles is not less than 5, where an aspect ratio is defined as a ratio of a major axis to a minor axis of the fibrous particle viewed from the sliding surface. An average grain size of the fibrous particles in cross-sectional view perpendicular to the sliding surface is 5 to 50 μm.

A bearing liner includes a binder with a resin material, a pre-preg, a structural yarn and a lubricating yarn, and particles of aluminum oxide (Al.sub.2O.sub.3). The particles of aluminum oxide may be embedded within the binder or within the lubricating yarn, or may be embedded within both the binder and the lubricating yarn. A plain bearing includes an inner ring, an outer ring and such a liner interposed or disposed between the rings.

An annular ring having a contact portion, a raceway and a squirrel-type cage secured to the contact portion. The contact portion is formed from a first metal material, and the squirrel cage is formed from a second composite-type material including a matrix in which reinforcing fibres are embedded, the pierced portion of the squirrel cage being attached to an outer surface of the contact portion. Also, a bearing assembly with rolling elements having an outer ring, an inner ring coaxial with the outer ring, and a plurality of rolling elements housed between the raceway of the contact portion of the outer ring and a raceway of the inner ring.

A connection element providing a first ring and a second ring, the two rings rotating relative to one another about a central axis, the first ring having a contact portion with a contact surface interacting with the second ring for the relative rotation, and a fastening portion configured to be rigidly secured to a support. The contact portion is made of a first material and the fastening portion is made of a second material, different to the first material, the first material having a hardness strictly greater than that of the second material, and the second material having a structural fatigue strength strictly greater than that of the first material.

A Hybrid rolling bearing includes an inner raceway and an outer raceway and a plurality of rolling elements arranged therebetween. The outer raceway and the inner raceway are made from bearing steel, having a first surface RMS roughness R.sub.q1. The rolling elements are made from a ceramic material and have second surface RMS roughnesses R.sub.q2,i. At least one of the rolling elements has an increased surface RMS roughness R.sub.q2,N, which is significantly higher than the RMS roughnesses R.sub.q2,i, of the remaining rolling elements. The hybrid rolling bearing can be installed within a refrigerant compressor.