CONTINUOUSLY VARIABLE HYDROSTATIC TRANSMISSION WITH NEUTRAL-SETTING HYDRAULIC CIRCUIT

摘要

A continuously variable hydrostatic transmission includes axially aligned input (14) and output (16) shafts journaled by a transmission housing (12) and respectively coupled to a prime mover and a load. The input shaft (14) drives a hydraulic pump unit (18) while a hydraulic motor unit (20) is grounded to the transmission housing (12). A wedge-shaped swashplate (22) is pivotally connected to the output shaft (16) in operative position to accommodate pressurized hydraulic fluid exchanges between the pump (18) and motor (20) units. A controller (24) is coupled to adjust the angular orientation of the swashplate (22) relative to the output shaft axis (35) and thus set the transmission ratio. A hydraulic circuit (26), connected into the hydraulic motor unit (20), is selectively operable to vent high and low fluid pressure sides of the swashplate (22) to atmosphere, thus imposing a neutral transmission ratio condition regardless of the transmission ratio set by the controller (24).