System for controlling a hydrostatic-mechanical transmission when an oil pressure exceeds a relief pressure

摘要

A control system designed such that if a heavy load is imposed on a vehicle during running and a hydraulic relief state in which an oil pressure in a hydraulic circuit for a hydrostatic transmission unit exceeds a relief pressure is detected, the angle of a discharge controlling swash plate for a pump is reduced to a specified value (e.g., 50% of the maximum angle) or less, whereby the stall of the vehicle and the overheat of machine parts are prevented.