Apparatus for the feed and the speed and torque control of a hydraulic motor with variable displacement at constant pressure

Claim 1

An apparatus for controlling the speed and torque of a hydraulic motor having variable swept volume comprising: hydraulic feed means dimensioned to supplying a hydraulic fluid under constant pressure and at a flow rate sufficient to satisfy all hydraulic requirements of said motor; a speed control circuit including: means for generating an electrical reference signal, sensing means responsive to a speed of the motor for detecting an actual value of the speed of the motor in response to a change of a load on said motor and generating an electrical signal representing said actual value, comparator means for comparing said reference signal and said actual value, and an electrically controlled flow regulating valve receiving a comparison signal from said comparator means and connected in series between said hydraulic feed means and said motor, said flow regulating valve varying flow of the hydraulic fluid between said hydraulic feed means and said motor for maintaining a predetermined rotational speed of the motor regardless of said change of the load, said flow regulating valve being formed with an outlet port connected to a feed inlet of said motor; and a hydraulic constant-pressure control circuit operatively connected with said outlet port of said valve, said constant-pressure control circuit including: means for varying a swept volume of the motor in response to the change of a pressure of said fluid at said outlet port and applied to said feed inlet of said motor until an equilibrium is reached between said pressure of said fluid at said outlet and a torque developed by said motor, said means for varying the swept volume of the motor including a pressure-reducing valve with a fixed threshold and a regulating valve connected with said outlet port of said flow regulating valve.

Claim 2

An apparatus for controlling the speed and torque of a hydraulic motor having variable swept volume comprising: hydraulic feed means dimensioned to supplying a hydraulic fluid under constant pressure and at a flow rate sufficient to satisfy all hydraulic requirements of said motor; a speed control circuit including: means for generating an electrical reference signal, sensing means responsive to a speed of the motor for detecting an actual value of the speed of the motor in response to a change of a load on said motor and generating an electrical signal representing said actual value, comparator means for comparing said reference signal and said actual value, and an electrically controlled flow regulating valve receiving a comparison signal from said comparator means and connected in series between said hydraulic feed means and said motor, said flow regulating valve varying flow of the hydraulic fluid between said hydraulic feed means and said motor for maintaining a predetermined rotational speed of the motor regardless of said change of the load, said flow regulating valve being formed with an outlet port connected to a feed inlet of said motor; and a hydraulic constant-pressure control circuit operatively connected with said outlet port of said valve, said constant-pressure control circuit including: means for varying a swept volume of the motor in response to the change of a pressure of said fluid at said outlet port and applied to said feed inlet of said motor until an equilibrium is reached between said pressure of said fluid at said outlet and a torque developed by said motor, said means for varying the swept volume of the motor including a pressure-reducing valve with a fixed threshold and a regulating valve connected with said outlet port of said flow regulating valve.