A rolling bearing (1) including: an inner ring (2) and an outer ring (3) which are bearing rings; a plurality of rolling elements (4) interposed in a rollable manner between raceway surfaces (2a, 3a) of the bearing rings; and a retainer configured to retain the plurality of rolling elements (4), wherein a nozzle (10) configured to inject a cooling fluid (R) toward the rolling elements (4) is provided to a fixed-side bearing ring which is one of the inner ring (2) and the outer ring (3), with an outlet (10a) side of the nozzle (10) oriented forward in a revolution direction of the rolling elements (4).

A spindle-bearing protecting device is provided that captures an indication of failure of the spindle bearings of a machine tool and can prolong the time until the main bearing is scorched. A spindle-bearing protecting device for protecting a bearing that supports a spindle to be rotatable, includes: a rotating part provided more to an outer side in an axial direction than the bearing, and having a rotor blade that rotates along with the spindle; a supply part that supplies coolant or lubricant to between the rotor blade and the bearing; a detection unit that detects abnormality of the bearing; and a control unit that controls a supply of coolant or lubricant by way of the supply part and the revolution speed of the spindle, in a case of the detection unit detecting abnormality of the bearing.

A measuring device is adapted for measuring a change of linear dimension of a shaft body of a bearing device along an axis due to thermal expansion. The measuring device includes a stationary seat and a strain unit. The strain unit includes an actuator and a strain member. The actuator is adapted to be mounted to the shaft body, and is movable relative to the stationary seat along the axis as a result of the change of linear dimension of the shaft body. The strain member is deformable, is secured to the stationary seat and is connected to the actuator such that movement of the actuator along the axis results in a force applied to the strain member which deforms the strain member.

A bearing apparatus includes a bearing that rotatably supports a main spindle around a rotation axis, a spacer including an inner-ring spacer adjacent to an inner ring of the bearing and an outer-ring spacer adjacent to an outer ring, and a heat flux sensor provided in an inside surface of the outer-ring spacer. A distance in a direction along the rotation axis from a center of the bearing to a center of the heat flux sensor is longer than 0.5 time and shorter than one time of a dimension of the bearing in the direction along the rotation axis.

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.

In an angular ball bearing (10), an outer race (12) has at least one diameter-directional hole (15) that supplies lubricating oil and passes through from the outer circumferential surface to the inner circumferential surface along the diameter direction. In a cross-section taken along the axial direction passing through a center (O) of the ball (13), the axial-directional position of a line extending through a central axis (X) of the diameter-directional hole (15) in the outer circumferential surface of a retainer (14) is located between an intersection position (A), at which an outer circumferential surface (14a) of the retainer (14) and a surface of a ball (13) intersect, and an axial-directional end (B) of a pocket (P).

In an angular ball bearing (10), an outer race (12) has at least one diameter-directional hole (15) that supplies lubricating oil and passes through from the outer circumferential surface to the inner circumferential surface along the diameter direction. In a cross-section taken along the axial direction passing through a center (O) of the ball (13), the axial-directional position of a line extending through a central axis (X) of the diameter-directional hole (15) in the outer circumferential surface of a retainer (14) is located between an intersection position (A), at which an outer circumferential surface (14a) of the retainer (14) and a surface of a ball (13) intersect, and an axial-directional end (B) of a pocket (P).

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 machine element, in particular for a shaping machine, includes a lubricated bearing and/or a seal and a primary drainage conduit for catching a fluid medium issuing from the bearing and/or the seal, preferably substantially pressure-lessly. A collecting device is provided for collecting the fluid medium which is caught in the primary drainage conduit over a period of time, and a measuring device is adapted to directly and/or indirectly measure an amount of the fluid medium collected by the collecting device over the period of time.

A measuring device is adapted for measuring a change of linear dimension of a shaft body of a bearing device along an axis due to thermal expansion. The measuring device includes a stationary seat and a strain unit. The strain unit includes an actuator and a strain member. The actuator is adapted to be mounted to the shaft body, and is movable relative to the stationary seat along the axis as a result of the change of linear dimension of the shaft body. The strain member is deformable, is secured to the stationary seat and is connected to the actuator such that movement of the actuator along the axis results in a force applied to the strain member which deforms the strain member.