GB1249745A - Power steering apparatus - Google Patents

Abstract

1,249,745. Vehicle power steering. TOYODA KOKI K.K., [trading as TOYODA MACHINE WORKS Ltd.]. 17 Sept., 1969 [17 Sept., 1968], No. 45821/69. Heading B7H. Power steering apparatus includes two steering shafts 22, 38 (Figs. 1 and 4), connected by a resilient member such as a double torsion-bar 40, a flap-valve mechanism 33, 34 actuable in response to relative rotation between the shafts, an hydraulic motor 16 (Fig. 3) operable by the flap-valve mechanism to boost manual steering, pistons 42, 43 serving to damp vibrations of the flap-valve mechanism, and a surge pressure absorbing device for absorbing surge pressure in the apparatus. Steering shaft 22, which is coupled to shaft 38 via a coupling 30, is connected to a main valve member 29 in which are provided valve chambers 35, 36, each of which houses a respective flap-valve 33, 34. Flap-valve 33 comprises valve seats (33a) (Fig. 5, not shown) normally spaced from the openings of distribution ports (35a, 35b) which connect chamber 35 to annular grooves 31, 32 of valve member 29 via conduits (49, 50). Similarly, flap-valve 34 comprises valve seats (34a) (Fig. 6, not shown), normally spaced from the openings of jet ports (36a, 36b) connecting annular grooves 31, 32 to chamber 36 via conduits (51, 52). The annular grooves 31, 32 are connected via conduits 59, 60, to respective chambers 15a, 15b of the hydraulic motor 16. In the absence of steering torque, fluid pumped into chamber 35 through port 25 enters distribution ports (35a, 35b) of chamber 35 and hence is supplied to grooves 31, 32 from which it passes to chambers 15a, 15b of the motor as well as to chamber 36 via jet ports (36a, 36b) and thence to reservoir via outlet 26. Turning of steering shaft 38 clockwise results in distribution ports (35b) in chamber 35 to be closed by the valve seats so that groove 32 receives no fluid. However, distribution ports (35a) are fully opened so that groove 21 receives fluid which then passes via conduits (52) to jet ports (36b) of chamber 36. These, however, have been closed by their associated valve seats. Hence, pressure build-up in groove 31 causes fluid to pass to chamber 15a of the motor which thereby assists rotation of the output shaft 12 of the apparatus. In the embodiment shown, spring-urged pistons 42, 43 receive fluid from grooves 31, 32 and press against the flap-valves to eliminate their vibration. Centrally-mounted pistons 44 are provided to absorb surge pressures in the hydraulic circuitry. In other embodiments, throttling orifices may be included in conduits 59, 60 in addition to pistons 44 (Fig. 9, not shown), pistons 44 may be replaced by spool valves and throttling orifices in the conduits 59, 60 (Figs. 10, 11, not shown), pistons 42, 43 may have direct connection with chamber 35 and an arrangement of spool valves and throttling orifices in conduits 59, 60 (Fig. 12, not shown), or a surge pressure absorbing piston (80) (Fig. 13, not shown), may be provided externally of the main valve housing.