Hydraulic motor control system - has separate secondary system with relief valve to control primary pump speed

摘要

A hydraulic motor (2) and its drive pump (1) lie in a closed circuit (3, 4). Separately, a second pump (24) generates control pressure which, through a manual selector (22), is directed into one of two lines (19, 21) to a control valve (16) and to a control piston (28), thus determining the rotational direction of the pump (1). Pressure tapped from the main circuit (3, 4) opens the control valve (16) to connect the control pressure to a relief valve (36), so limiting it to a set value. To this corresponds a position of the control piston (28), which determines the rotational speed of the pump (1).