| 摘要 |
A power assisted steering system of the rack and pinion type with a "centre take-off" 7 has its rack bar 1 carrying a piston 17 at one end thereof. The rack bar 1 forms with the piston opposed pressurized faces 20 and 21 which present pressurized areas in the ratio 1:2. Valve means 22 controllable by rotational input to the pinion 4 directs fluid at the same pressure to both piston chambers 18 and 19 to assist in displacement of the piston rod 1 in a sense to contract the piston chamber 18 or directs fluid to the piston chamber 18 and exhausts the piston chamber 19 to assist in displacement of the piston rod 1 in a sense to contract the piston chamber 19-the power assistance to displacement of the piston rod being substantially the same in both senses of direction. The rack bar 1 is slidably mounted by and longitudinally displaceable relative to two bearings 10 and 11 of which bearing 10 biases the rack 5 into engagement with the pinion and the bearing 11 is in the form of a bush which partly seals an end of the piston chamber 18. The bearings 10 and 11 restrain the rack bar for lateral displacement.
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