Speed change control method of hydraulic driving apparatus for vehicles and speed changing device

摘要

The present invention relates to a speed change control method of a hydraulic driving apparatus for vehicles and a speed changing device which provide exellent running efficiency and controllability. In order to achieve the above-described advantages, the speed change control method comprises discriminating between at least a power running and a brake running from said accelerating amount (&thetas;) and the rotation speed ( omega out) of said hydraulic motor (50); and allowing return oil from said hydraulic motor (50) to a tank (6) to have a high pressure so as to be fed to the supply side of said hydraulic motor (50) if inlet pressure (Pp) to said hydraulic motor (50) is lower than permissible suction pressure of said hydraulic motor (50) when discriminating the brake running.