Patent ID: 6336324
Filing Date: 2002-01-08
Classification: E02F,F04B

Abstract:
Hydraulic control system (1) comprising an adjusting apparatus (6) for adjusting an actuating piston (7), which is disposed between two actuating pressure chambers (11, 12) and influences the displacement volume of a hydraulic pump (4), depending upon a pressure difference between two actuating pressure lines (13, 14) which are each connected to one of the actuating pressure chambers (11, 12), wherein the actuating pressure prevailing in the actuating pressure lines (13, 14) is defined by two control lines (33, 34), and one braking valve (19, 20) associated with each of the actuating pressure chambers (11, 12) and throttling return flow of hydraulic fluid from the associated actuating pressure chamber (11, 12) into a hydraulic fluid tank (21), characterized inthat disposed in each actuating pressure line (13, 14) is a control valve (27, 28), which is switchable between an open and a closed valve position, that a branch (15, 16) is provided in each actuating pressure line (13, 14) between the associated control valve (27, 28) and the associated actuating pressure chamber (11, 12), wherein the associated braking valve (19, 20) is disposed between the branch (15, 16) and the hydraulic fluid tank (21) and switchable between a throttled valve position (24, 25) and a closed valve position (22, 23), and that the braking valves (19, 20) and the control valves (27, 28) are activated by the control lines (33, 34), wherein the braking valves (19, 20) are closed and the control valves (27, 28) are opened when the greater of the control pressures prevailing in the control lines (33, 34) is greater than a defined threshold value and the braking valves (19, 20) assume their throttled valve position (24, 25) and the control valves (27, 28) are closed when the greater of the control pressures prevailing in the control lines (33, 34) is lower than the defined threshold valve.