A ball screw drivel, in particular for a parking brake, comprises a threaded spindle, a spindle nut, and rolling bodies, namely balls, which are arranged in a thread turn between the threaded spindle and the spindle nut, Spring elements are arranged in the thread turn between nut-side stops. There is at least one setting of the threaded spindle and the spindle nut in which the balls and the spring elements are arranged in the thread turn with backlash.

In a ball screw apparatus, a ball train including a plurality of main balls is housed in a raceway between a ball track of a ball nut and a ball track of a ball screw shaft. A coil spring housed in the raceway includes a first end that engages with an end of the ball train and a second end supported by a stopper (a first recessed portion, a protruding portion, or the like) of the ball nut. A stopper ball having a diameter larger than the diameter of the main ball is interposed between the stopper and the second end of the coil spring.

A ball screw device includes a screw shaft; a nut having a second helical groove; and a plurality of balls. When the screw shaft is rotated about an axis of the screw shaft while being subjected to the external force, the balls are displaced from positions under no load condition toward one side in an axial direction. A second helical groove of the nut includes a stopping member configured to prevent the balls from falling off from the second helical groove. A plurality of coil springs are arranged in series along the second helical groove. An angle in a circumferential direction occupied by each of the coil springs about the axis is 180 degrees or less when the coil springs are disposed in the second helical groove.

Provided is a separator having excellent chemical resistance, impact resistance, and productivity. A bearing retainer (1) is a separator that is interposed between two spheres adjacent to and moving in conjunction with each other for retaining the spheres configured to be movable in conjunction with and apart from each other and is formed from a resin composition containing a fluororesin which is a polymer of a monomer containing vinylidene fluoride as a main component. The bending modulus of elasticity of the resin composition is 1600 MPa or less, and the Charpy impact strength of the resin composition is 26 kJ/m.sup.2 or more.

Provided is a separator having excellent chemical resistance, impact resistance, and productivity. A bearing retainer (1) is a separator that is interposed between two spheres adjacent to and moving in conjunction with each other for retaining the spheres configured to be movable in conjunction with and apart from each other and is formed from a resin composition containing a fluororesin which is a polymer of a monomer containing vinylidene fluoride as a main component. The bending modulus of elasticity of the resin composition is 1600 MPa or less, and the Charpy impact strength of the resin composition is 26 kJ/m.sup.2 or more.

In a ball screw apparatus, a ball train including a plurality of main balls is housed in a raceway between a ball track of a ball nut and a ball track of a ball screw shaft. A coil spring housed in the raceway includes a first end that engages with an end of the ball train and a second end supported by a stopper (a first recessed portion, a protruding portion, or the like) of the ball nut. A stopper ball having a diameter larger than the diameter of the main ball is interposed between the stopper and the second end of the coil spring.

A track member or a movable member constituting a motion guide device includes a rolling part formed of a metal material contacting with a plurality of rolling bodies and forming a rolling body rolling surface a, a mounting part formed of a metal material having a mounting hole for mounting an external member, and a track body or a movable body formed of FRP jointed with the rolling part and the mounting part and forming the track member or the movable member, and the mounting part and the track body or the movable body have joint holes, opened in a direction orthogonal to a lamination direction of FRP reinforced fiber sheets S forming the track body or the movable body at a time of the joint, and can be jointed using jointing means. An external member can be securely mounted to the motion guide device formed of FRP.

In a ball screw apparatus, a ball train including a plurality of main balls is housed in a raceway between a ball track of a ball nut and a ball track of a ball screw shaft. A coil spring housed in the raceway includes a first end that engages with an end of the ball train and a second end supported by a stopper (a first recessed portion, a protruding portion, or the like) of the ball nut. A stopper ball having a diameter larger than the diameter of the main ball is interposed between the stopper and the second end of the coil spring.

A ball screw device includes a screw shaft having a first helical groove provided on an outer periphery of the screw shaft; a nut having a second helical groove provided on an inner periphery of the nut, the nut being fitted on the outer periphery of the screw shaft; a plurality of balls that are disposed in a ball groove such that the plurality of balls are rollable, the ball groove being provided between the first helical groove and the second helical groove that are disposed so as to face each other in a radial direction; a helical member that extends in a helical shape along the ball groove and is displaceable along the ball groove; and a first biasing member that biases the helical member toward the plurality of balls.

A ball screw device includes a screw shaft; a nut having a second helical groove; and a plurality of balls. When the screw shaft is rotated about an axis of the screw shaft while being subjected to the external force, the balls are displaced from positions under no load condition toward one side in an axial direction. A second helical groove of the nut includes a stopping member configured to prevent the balls from falling off from the second helical groove. A plurality of coil springs are arranged in series along the second helical groove. An angle in a circumferential direction occupied by each of the coil springs about the axis is 180 degrees or less when the coil springs are disposed in the second helical groove.