AUTOMATIC TRANSMISSION EQUIPPED WITH AUXILIARY HYDRAULIC SPEED-CHANGING GEARS.

摘要

The invention relates to an automatic transmission for a hydraulic excavator and the like, which is equipped with auxiliary two-stage speed-changing gears. A hydraulic circuit (30) on the discharge side of a revolution-sensing hydraulic pump (3) connected to the input shaft (2b) of auxiliary speed-changing gears (1) is connected to one end of an automatic speed-changing valve (8) and the other end of the valve (8) is connected to the hydraulic circuit (30) on the discharge side of the pump (3) through an orifice (7). The valve (8) is controlled by the difference in pressure between a discharge oil of the pump (3) and another oil having passed the orifice (7) and, by changing over an automatic two-stage speed-changing valve (6) with the pilot pressure from the valve (8), a two-stage clutch can be changed over without damage to the hydraulic motor.