Abstract: An outer joint member 31 and a hub wheel 16 are coupled so as to be able to transmit torque by meshing face splines 51 and 52 respectively provided and applying a tightening force in an axial direction between both the face splines 51 and 52. Shapes of tooth surfaces of both the face splines 51 and 52 are determined such that, in a process of bringing both the face splines 51 and 52 close to each other in the axial direction and meshing with each other, tooth surfaces 51a and 51b of both the face splines 51 and 52 first come into contact with each other in, among an outer diameter portion Ea of a meshing region X between both the face splines, an inner diameter portion Ec, and an intermediate portion Eb sandwiched between the outer diameter portion and the inner diameter portion, the intermediate portion Eb.

Abstract: A seat slide device comprises a rail unit consisting of upper and lower guide rails and rollers disposed between the upper and lower guide rails. The upper guide rail includes a substantially channeled member consisting of a downwardly-opening, channeled portion, a vertical portion extending vertically and longitudinally from an upper wall of the downwardly-opening, channeled portion, and flanged portions formed at lower ends of both side walls of the downwardly-opening, channeled portion. The flanged portions of the upper guide rail are slidably engaged with the respective flanged portions of the lower guide rail when assembling. The vertical portion, the downwardly-opening, channeled portion, and the flanged portions of the upper guide rail are integrally formed by bending a piece of metal sheet. The vertical portion is formed by doubling over the metal sheet at an essentially center of the metal sheet.

Abstract: A pick-up device which includes a light source and a condenser lens for effecting recording and reproduction of information by projecting a light beam as collected by the condenser lens onto a recording medium. A diffraction grating is provided between the light source and the condenser lens for dividing light returning from the recording medium by a diffraction grating so as to be directed to a photo-detector, to thereby obtain an optical detection signal.

Abstract: A focusing error detector comprises a light source, a collimator lens for making parallel the pencil of rays emitted by the light source, an objective lens which focuses the parallel pencil of rays to form a beam spot on a data-recording disc with data tracks and guide tracks formed thereon and which receives the pencil of rays reflected from the data-recording disc, an optical system for forming a beam spot from the reflected pencil of rays incident to the objective lens, and an optical detector having a plurality of divided optical sensor blocks for receiving the formed beam spot so as to detect the focusing error of the beam spot formed on the data-recording disc on the basis of the configuration of the received beam spot.