tailieunhanh - The Motor Vehicle 2010 Part 16

Tham khảo tài liệu 'the motor vehicle 2010 part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 1076 The Motor Vehicle Fig. now has a variable pitch so that when the roller follower B is in the central position shown the ratio angular motion of cam angular motion of drop arm C for a very small motion is about 21 1 but when the drop arm and follower have moved about 12 away from the central position that ratio has fallen to 13 1 and thereafter it remains constant at that value. The valve which controls the servo action now operates by the rotational displacement of its two main components instead of by their axial displacements as in the Ross system. The cam is carried in the casing on two angular contact ball bearings and is coupled at the left-hand side to the torsion bar D by a cross-pin. At the right-hand end the torsion bar is coupled also by a cross-pin to the sleeve E which is splined to the steering-wheel shaft and which forms the inner member to the valve. The left-hand end of the sleeve E is formed with splines F which engage splines formed in the right-hand end of the cam A but these splines are machined so as to allow 7 of freedom of rotation and are only to provide a safeguard against over-stressing of the torsion bar when the steering is operated without servo assistance. Pipes connect the pump which is driven by the engine to the valve and the latter to the outer end of the servo cylinder the inner end of the servo cylinder forms the casing which houses the cam A and follower assembly and the valve is directly connected to that space. The outer member G of the valve is coupled by the ball-ended pin H to the right-hand end of the cam A. The servo piston J is integral with a stem on which rack teeth are formed and these teeth engage teeth machined on the end of the drop arm forging C. The principle of operation of the valve is shown by the diagrams Figs a and b . It is really three valves in parallel parts relative to which are denoted by suffixes 1 2 and 3 - following the letters P and S in the diagrams - but the action will be .