Concentric axial piston transmission

Abstract

A continuously variable transmission includes a housing enclosing an axial piston pump and an axial piston motor arranged concentrically with respect to the pump. The pump and motor have cylinder blocks with axial cylinders, each receiving a piston. Pump and motor swash plates are engaged with the pump and motor pistons for rotating and nutating relative to the cylinder blocks to convert between fluid pressure power and rotating mechanical power. Input and output shafts are journaled in the housing for rotation about a central axis and have inner ends coupled to the pump and to the motor swash plate, respectively. Fluid passages between the pump cylinder block and the motor cylinder block convey fluid pressurized in the pump to the motor cylinders and convey spent fluid displaced from the motor cylinder block back to the pump cylinders. A mechanism changes the angle of the motor swash plate and the angle of the pump swash plate relative to the central axis under automatic or operator control to vary the transmission control for operation of the vehicle. The input shaft exerts a first component of torque through the pump to the pump swash plate and thence to the output swash plate and the output shaft, and the fluid pressurized in the pump drives the motor pistons against the output swash plate to exert a second component of torque thereon in the same direction as the first component, combining in a variable ratio to produce output torque in the output shaft.