Hydrostatic ground drive control system for a work machine with smooth transition between speed ranges

摘要

The control system allows selecting from multiple speed ranges for the ground drive of a work machine (20) without a mechanical transmission. The system does this by controlling a variable displacement fluid pump (34) supplying fluid to variable displacement fluid motors (28, 30) driving ground wheels (22, 24) of the machine. When a speed range is selected, the system automatically controls displacement of the pump and motors to provide operability within the range by movement of a speed input device. When another range is selected, the system provides a seamless transition, including to and from reverse, as no disengaging and engaging of mechanical gears, or change in the speed input position, is required. The system can also automatically adjust ground speed for the new speed range for the current speed input position.