Provided is an electric actuator (1), including: a motor part (A); and a motion conversion mechanism part (B). The motion conversion mechanism part (B) includes: a ball screw shaft (33); and a ball screw nut (32), which is rotatably fitted to an outer periphery of the ball screw shaft (33), and is provided so as to be capable of transmitting torque with a rotor (24) of the motor part (A) rotatably supported through intermediation of a rolling bearing (27, 30). The ball screw shaft (33) advances toward one side in the axial direction or retreats toward another side in the axial direction in accordance with a rotation direction of the ball screw nut (32). In the electric actuator (1), a needle roller bearing (47) serving as a thrust bearing is arranged adjacent to the ball screw nut (32) on the another side in the axial direction.

Provided is an electric actuator (1), including: a motor part (A); and a motion conversion mechanism part (B). The motion conversion mechanism part (B) includes: a ball screw shaft (33); and a ball screw nut (32), which is rotatably fitted to an outer periphery of the ball screw shaft (33), and is provided so as to be capable of transmitting torque with a rotor (24) of the motor part (A) rotatably supported through intermediation of a rolling bearing (27, 30). The ball screw shaft (33) advances toward one side in the axial direction or retreats toward another side in the axial direction in accordance with a rotation direction of the ball screw nut (32). In the electric actuator (1), a needle roller bearing (47) serving as a thrust bearing is arranged adjacent to the ball screw nut (32) on the another side in the axial direction.

An axial rolling bearing consisting of at least one annular bearing disc which has a circumferential raceway arched in profile cross section, and consisting of a multiplicity of rolling elements formed as bearing needles or bearing rollers and arranged next to one another in a circular form, which roll on the raceway of the bearing disc and are kept at uniform distances from one another by a bearing cage. The arched raceway is formed having at least one circumferential groove-shaped depression at least in the region of one of the two ends of the rolling elements.

An axial rolling bearing consisting of at least one annular bearing disc which has a circumferential raceway arched in profile cross section, and consisting of a multiplicity of rolling elements formed as bearing needles or bearing rollers and arranged next to one another in a circular form, which roll on the raceway of the bearing disc and are kept at uniform distances from one another by a bearing cage. The arched raceway is formed having at least one circumferential groove-shaped depression at least in the region of one of the two ends of the rolling elements.

A thrust roller bearing includes a plurality of radially arranged rollers, and a pair of annular washers having raceway surfaces on which the rollers roll. The raceway surfaces are arranged to face each other. The roller is made of high-carbon chromium bearing steel and has a surface roughness of 0.01 to 0.10 in terms of Rvk and 0.01 to 0.08 in terms of Rk. At least one of the washers is made of carbon steel, surface compressive residual stress of the raceway surface is −1400 MPa to −1000 MPa, and Vickers hardness of surface of the raceway surface is 850 to 900.

A thrust roller bearing includes a plurality of radially arranged rollers, and a pair of annular washers having raceway surfaces on which the rollers roll. The raceway surfaces are arranged to face each other. The roller is made of high-carbon chromium bearing steel and has a surface roughness of 0.01 to 0.10 in terms of Rvk and 0.01 to 0.08 in terms of Rk. At least one of the washers is made of carbon steel, surface compressive residual stress of the raceway surface is −1400 MPa to −1000 MPa, and Vickers hardness of surface of the raceway surface is 850 to 900.

A thrust roller bearing includes a plurality of radially arranged rollers, and a pair of annular washers having raceway surfaces on which the rollers roll, the raceway surfaces being arranged to face each other. The roller is made of high-carbon chromium bearing steel, and contains 1.1 mass % to 1.6 mass % of carbon and 0.1 mass % to 0.6 mass % of nitrogen in a range of 0.1 mm from a surface. A surface compressive residual stress is smaller than −900 MPa, a surface roughness is 0.01 to 0.10 in terms of Rvk and 0.01 to 0.08 in terms of Rk, and a Vickers hardness of the surface is 860 to 980. At least one of the washers is made of carbon steel, and surface roughnesses of the raceway surfaces are 0.05 to 0.20 in terms of Rvk and 0.08 to 0.15 in terms of Rk.

A thrust roller bearing includes a plurality of radially arranged rollers, and a pair of annular washers having raceway surfaces on which the rollers roll, the raceway surfaces being arranged to face each other. The roller is made of high-carbon chromium bearing steel, and contains 1.1 mass % to 1.6 mass % of carbon and 0.1 mass % to 0.6 mass % of nitrogen in a range of 0.1 mm from a surface. A surface compressive residual stress is smaller than −900 MPa, a surface roughness is 0.01 to 0.10 in terms of Rvk and 0.01 to 0.08 in terms of Rk, and a Vickers hardness of the surface is 860 to 980. At least one of the washers is made of carbon steel, and surface roughnesses of the raceway surfaces are 0.05 to 0.20 in terms of Rvk and 0.08 to 0.15 in terms of Rk.

A trunnion roller thrust measurement assembly includes a trunnion roller assembly and a thrust measurement assembly. The trunnion roller assembly includes a roller configured to provide rotary support of a rotary drum; a shaft attached to the roller, the shaft being aligned with an axis of rotation of the roller; and a bearing housing configured support an end of the shaft. The thrust measurement assembly includes a bearing housing end cap attachable to an end of the bearing housing; and one or more thrust sensors disposed on the bearing housing end cap. The one or more thrust sensors are configured to sense a thrust force exerted on the bearing housing end cap by an axial displacement of the shaft. An adjustment mechanism is utilized to skew the roller based on the sensed thrust force.

A method of assembling a multi-row thrust bearing cage is disclosed. The method includes providing an inner cage and an outer cage, the inner cage including a first retainer and a first alignment guide, and the outer cage including a second retainer and a second alignment guide. The method includes positioning the inner cage and the outer cage relative to each other such that the first alignment guide is circumferentially aligned with the second alignment guide. The method also includes inserting the inner cage relative to the outer cage such that the first retainer of the inner cage engages with the second retainer of the outer cage and the inner cage is retained with the outer cage.