In a screw device where a shim is disposed between two nuts, a screw device that can detect preload is provided. The preload detectable screw device includes: two nuts; a shim sandwiched and compressed between the two nuts; a coupling portion configured to couple the two nuts in such a manner as to be incapable of relative rotation to each other; and a force sensor for detecting preload. A contact surface of at least one of the two nuts with the shim is provided with a recess, spaced apart from the coupling portion, in such a manner as to reduce the contact area. The force sensor is attached near the recess on an outer surface of the shim.

In a screw device where a shim is disposed between two nuts, a screw device that can detect preload is provided. The preload detectable screw device includes: two nuts; a shim sandwiched and compressed between the two nuts; a coupling portion configured to couple the two nuts in such a manner as to be incapable of relative rotation to each other; and a force sensor for detecting preload. A contact surface of at least one of the two nuts with the shim is provided with a recess, spaced apart from the coupling portion, in such a manner as to reduce the contact area. The force sensor is attached near the recess on an outer surface of the shim.

A screw device is provided which can facilitate management of a tolerance of a recess where a circulation component is housed. A circulation component is housed in a recess of a nut with clearance. At least part of the circulation component is blocked by a lid member fixed to the nut by fastening means. Upon a centrifugal force acting on a rolling element moving along a circulation path in the circulation component, the circulation component comes into contact at three points with the recess as viewed in an axial direction.

In a ball screw device, an inner peripheral rolling groove of a nut includes, between openings of mounting holes, a constant pitch circle diameter region where a pitch circle diameter is constant and gradually-changing pitch circle diameter regions where the pitch circle diameter gradually increases, in the ranges from opposite ends of the constant pitch circle diameter region to the respective openings. At least the constant pitch circle diameter region has a surface hardness greater than or equal to a predetermined value, among the constant pitch circle diameter region and the gradually-changing pitch circle diameter regions excluding edges at the boundaries between the respective openings and the inner peripheral rolling groove, and the edges at the boundaries between the respective openings and the inner peripheral rolling groove have a surface hardness less than the predetermined value.

A screw device is provided which can facilitate management of a tolerance of a recess where a circulation component is housed. A circulation component is housed in a recess of a nut with clearance. At least part of the circulation component is blocked by a lid member fixed to the nut by fastening means. Upon a centrifugal force acting on a rolling element moving along a circulation path in the circulation component, the circulation component comes into contact at three points with the recess as viewed in an axial direction.

An offset preload ball screw with expandable loading area includes: a screw, a nut, and a plurality of balls between the screw and the nut. The inner helical groove of the nut includes at least a first section, a second section and a third section which are continuously connected one another. The preload constantly and smoothly changes in the second section, and the balls can be subjected to loads in positive or negative direction in the second section. Therefore, the running smoothness, precision and load capacity of the ball screw of the present invention is enhanced.

An actuator assembly comprises a ball screw drive having a ball screw spindle rotatably mounted about a spindle axis, on which a spindle nut is received, and a thread track on an outer circumferential surface of the ball screw spindle, has a portion of a ball return on a circumferential wall of the ball screw spindle, which return connects a beginning and an end of the thread track to one another. At the beginning and at the end of the thread track, an insert is inserted in which a ball race is formed, which is part of the ball return. The inserts are arranged such that each end of a ball race adjoins a portion of the ball return and another end adjoins a beginning of a thread track or an end of the thread track. In a section perpendicular to a spindle axis, an angle of the ball race to a tangent to the thread track at an adjacent beginning or end of the thread track is greater than 90? in a central portion between the first and the second end of the ball race. To determine the angle, a side of the tangent on which a portion of the thread track directly adjacent to the beginning or the end lies is selected. To produce the ball screw spindle, a channel of the ball return is introduced into the circumferential wall, a thread is introduced into an outer circumferential surface of the ball screw spindle, and in each case one depression is introduced into the outer circumferential surface at the beginning and at the end of the thread track, and inserts are inserted into the depressions.

A multi-row ball screw includes a nut having a plurality of spiral grooves on an inner peripheral surface thereof, a screw shaft having a plurality of spiral grooves on an outer peripheral surface thereof, and a plurality of balls disposed so as to be rollable on rolling paths constituted by the plurality of spiral grooves of the nut and the plurality of spiral grooves of the screw shaft. The spiral groove of the nut includes a U-shaped first spiral groove having left and right flanks that are respectively able to come into contact with two-row balls and separated from each other in an axial direction, and two second spiral grooves continuous with each row of the first spiral groove and each having left and right flanks that are able to come into two-point contact with the ball.

In a ball screw device, an inner peripheral rolling groove of a nut includes, between openings of mounting holes, a constant pitch circle diameter region where a pitch circle diameter is constant and gradually-changing pitch circle diameter regions where the pitch circle diameter gradually increases, in the ranges from opposite ends of the constant pitch circle diameter region to the respective openings. At least the constant pitch circle diameter region has a surface hardness greater than or equal to a predetermined value, among the constant pitch circle diameter region and the gradually-changing pitch circle diameter regions excluding edges at the boundaries between the respective openings and the inner peripheral rolling groove, and the edges at the boundaries between the respective openings and the inner peripheral rolling groove have a surface hardness less than the predetermined value.

There is provided a ball screw device capable of allowing interference to be easily elastically deformable and decreasing friction resistance of a seal member with respect to a screw shaft without damaging seal properties of the seal member. A predetermined section of a land sliding-contact portion (46) of a sliding-contact portion (40) and a section of a seal piece (37) of a lip portion (31) corresponding to the predetermined section are bent to protrude in one side in the axial direction of a nut (7) so that a protrusion (55) is formed, the bent section of the land sliding-contact portion (46) and the bent section of the seal piece (37) configure a pair of side surface portions (58, 58) of the protrusion (55) and a bottom portion (61) connecting the one side ends of the pair of side surface portions (58, 58).