AUTOMATIC SPEED SHIFTING DEVICE

摘要

An speed change device is equipped with an automatic change-over valve (18) which opens and closes a pilot fluid line (16) that connects a pilot port of a control valve (12, 12a) of a variable capacity hydraulic motor (2, 2a) to a pilot pump (6). The automatic speed change valve (18) has one pilot port that is connected to a pressurized fluid feed line (8, 8a) leading to the hydraulic motor (2, 2a) and has another pilot port (26) connected to the return fluid line (10, 10a) of the hydraulic motor (2, 2a). The automatic speed change valve (18) is controlled over by an effective differential pressure between the two fluid lines.