GB1400572A - Vehicle power-steering operated by fluid pressure - Google Patents

Abstract

1400572 Power assisted steering SOC ANON AUTOMOBILES CITROEN 22 Aug 1972 39150/72 Heading B7H A power assisted steering system for a vehicle includes a servomotor 1 of the differential type, the smaller chamber of motor 1 being connected to the source of pressurized fluid and the supply of fluid to the larger chamber being controlled by a movable distribution assembly 11 which co-operates with a control element 12 on the steering column 13 and on which assembly stresses engendered by the fluid pressures exerted on either side of the piston 3 are proportionately applied and in opposition to each other to provide "feel", the distribution assembly including a slide valve 23 which is arranged to close a passage leading to the larger chamber of motor 1 when in a rest position and to connect this passage to the source of fluid pressure, when displaced in one direction from the rest position, and to connect this passage to a fluid discharge passage when displaced in the other direction from the rest position, the pressure of the larger chamber being directly applied to one end of the slide valve. As described the distribution assembly is connected by line 16 to fluid pump 18 and accumulator 17, by line 20 to a reservoir 19, by line 21 to the smaller chamber of motor 1 and by line 22 to the larger chamber of motor 1. In a first embodiment (Fig. 2) the distribution assembly includes a body 11a housing a slide valve 23 connected to a lever 12a on the steering column 12 and a reaction piston 24 connected to the opposite side of the lever 12a. A passage 31 connects the smaller chamber of motor 1 to the piston 24 and to the pump line 16. A passage 27 connects the larger chamber of motor 1 to a chamber 32 at one end of valve 23 which in its neutral position blocks the passage 27 and in its operative position connects the passage 27 either to pump line 16 or reservoir line 20 depending on the direction of turn. The areas of the valve 23 and piston 24 correspond to the areas of the chambers of the motor 1, the arms of the lever 12a being of equal length. In a modification (not shown) the housing 11a surrounds the lever 12a which has a single arm, the valve 23 and piston 24 being arranged on opposite sides of the arm. In this case the valve 23 and piston 24 may be of equal area and are connected to the arm at different locations or may be of unequal area and connected to the arm directly opposite each other. In a second embodiment (Fig. 5) the pressure of the smaller chamber of motor 1 is applied directly to a chamber 35 at the opposite end of valve 23a to chamber 32, the areas of chambers 35 and 32 corresponding to the areas of the piston 3. In this case the valve 23a is positively connected to arm 12e by link 34.