BACKPRESSURE CONTROL CIRCUIT FOR HYDRAULIC DRIVE DEVICE

摘要

A backpressure control circuit for hydraulic drive devices, which reduces loss in drive power and can suppress cavitation. Thus the backpressure control circuit for hydraulic drive devices is a hydraulic drive circuit for supplying to a hydraulic motor a pressure oil discharged from a hydraulic pump through a direction changeover valve, which is switched upon receipt of a pilot pressure, and permitting a throttle valve at the time of braking by the hydraulic motor to throttle a return oil from the hydraulic motor and a discharged oil from the hydraulic pump to generate a backpressure to supply the pressure oil to the hydraulic motor via a suction valve for prevention of cavitation. The backpressure control circuit comprises a pilot valve (60) for taking out a pressure on a drive side of the hydraulic motor (24) as a pilot pressure upon receipt of a signal from an operating lever (39), and a variable throttle valve (80) changes over a backpressure to a low pressure or a high pressure upon receipt of a pilot pressure from the pilot valve (60).