Abstract: The threshing cylinder or rotor of a combine harvester is driven by a rotor hydraulic motor. A rotor pump, driven by an internal combustion engine supplies hydraulic fluid to the rotor hydraulic motor to drive the rotor. A variable speed traction drive propels the harvester over the surface of a field to harvest crops. A control system varies the ground speed of the harvester based upon the pressure of hydraulic fluid supplied to the rotor hydraulic motor to maintain a substantially constant crop material feed rate through the threshing cylinder or rotor. The control system can be an electronic system that measures the pressure of hydraulic fluid on the inlet side of the rotor hydraulic motor and varies the ground speed to keep the measured hydraulic fluid pressure substantially constant. A control system can also include a pressure control valve that varies the ground speed to maintain a constant rotor motor inlet hydraulic pressure.

Abstract: The combine harvester has a threshing and separating rotor with a threshing cylinder section that cooperates with a concave to thresh crop material. A hydraulic motor drives the rotor. A hydraulic pump, driven by an internal combustion engine, supplies hydraulic fluid to the hydraulic motor to drive the rotor. An electronic controller receives a rotor speed measurement from a speed sensor and compares the rotor speed with a selected threshing and separating rotor speed selected by an operator of the harvester and stored in the electronic controller. When the rotor speed varies from the selected rotor speed, the electronic controller sends a signal to a displacement control to change the threshing and separating rotor speed to approach the selected rotor speed. The displacement control can reverse the flow of hydraulic fluid to the hydraulic motor to reverse the direction of rotor rotation.