GB1213760A - Hydraulic actuators - Google Patents

Abstract

1,213,760. Differential gear. GENERAL MOTORS CORP. 9 Oct., 1969, No. 49670/69. Heading F2D. A thrust device 41 which employs hydrodynamic bearing pressure generated by the relative rotation of two contacting surfaces 31, 45 to produce axial thrust, used in this instance to load anti-spin clutch-discs 34 arranged between an input planet-carrier 11 and output side wheels 25, 26 of a limited slip differential gear on a motor-vehicle, comprises an annular piston 44 splined at 51 to rotate with the planetcarrier 11, and having on its outer face 45, contacting the plain bearing face 31 of the wheel 26, spiral grooves (Fig. 4, not shown) or radial grooves 46 between circumferentially-tapered trapezoidal recesses 48, 49 (of about 0À00025 inch depth), the depressions 48 terminating in axial holes 50, whereby when the piston 44 rotates forwardly relative to the adjacent sidewheel 26, their contacting faces 45, 31 develop in the recesses 48 hydrodynamic pressure which is fed through terminal holes 50 to an annular cylinder 42 in which the piston 44 has sealed slidable but not rotatable engagement. The axial thrust thereby applied to the cylinder 42 loads the clutch discs 34 to inhibit differential spin. As shown a thrust device 41 for each clutch loads only its own clutch and only for forward spin. In Fig. 3, not shown, a radial pin 21 supporting an inner thrust block 62 (65, Fig. 3) of the differential, has axial clearance in the block so that each thrust device loads both clutches. In Figs. 5-7, not shown, both the piston and cylinder have trapezoidally grooved pressuregenerating faces and there is an internal checkvalve (114) so that each face can develop pressure in opposite directions of rotation thus loading both clutches at once.