| 摘要 |
The pump (10) is provided with a compensating valve (14) comprising a valve body (15) formed with a bore (18) and having an inlet (34), a first port (102), a second port (104), a valve sleeve (19) movable within the bore (18) and a valve spool (20) movable within the valve sleeve (19), the valve sleeve (19) and the valve spool (20) being biassed in opposite directions by means of respective springs (21,22). The outlet of the pump (10) is connected to the inlet (34), the first port (102) communicates with a chamber (100) formed in the body of the pump (10), and the second port (104) is a low pressure vent. A pump displacement control cylinder (12) has a piston (29) which is subject at one end (29a) to the fluid pressure within chamber (100), and at its other end determines the adjustment of a displacement control cam (11) which controls the displacement setting of the pump (10). The said one end (29a) of the piston (29) is shaped as a conical cam surface, and a pin (25) extends from this cam surface, through a bore (28) in a spacer block (17) which separates the pump housing (13) from the compensating valve housing (15), and into contact with an arm (23b) of a pivotal lever (23). The lever (23) has another arm (23a) engaged with the valve sleeve (19) and a third arm (23c) which cooperates with an adjustable pressure limit stop (26). As the hydraulic load on the pump (10) varies, so the pump outlet pressure varies which results in a corresponding movement of the valve spool (20) to either admit pressurized fluid from the pump output to the chamber (100) or to vent chamber (100) to port (104) in each case with a corresponding adjustment of the pump capacity via piston (29) and cam (11). For each adjustment, a corresponding adjustment of valve sleeve (19) is effected via the coupling between sleeve (19) and piston (29) via pin (25) and lever (23).
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