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A hydrostatic axial piston transmission having a continuously variable transmission ratio includes an axial piston pump driven by an input shaft, the pump having an annular pump cylinder block with a ring of cylinders in which pump pistons reciprocate to pressurize and displace fluid from the pump c

A hydrostatic axial piston transmission having a continuously variable transmission ratio includes an axial piston pump driven by an input shaft, the pump having an annular pump cylinder block with a ring of cylinders in which pump pistons reciprocate to pressurize and displace fluid from the pump cylinders. The pump is also coupled to an output shaft for conveying reaction torque from the input shaft directly to the output shaft as a first output torque component. An axial piston hydraulic motor has an annular motor cylinder block with a ring of motor cylinders in which motor pistons reciprocate in a power stroke to apply output torque to the output shaft, and a displacement stroke in which spent fluid is displaced from the motor cylinders for return to the pump cylinders. The pump cylinder block is concentrically disposed within the annulus of the motor cylinder block, and the input shaft and the output shaft lie on a longitudinal axis through the annulus. The pump cylinder block lies against a flat surface which is tilted at an angle with respect to the longitudinal axis of the machine, so that rotation of the pump cylinder block relative to the flat surface causes the pump pistons to reciprocate and displace fluid under pressure through commutating passages to the motor. Rotation of the input shaft drives the pump to displace pressurized fluid through pressure passages while also transmitting reaction torque to the output shaft. The fluid pressurized by the pump energizes the motor to produce a second component of output torque in the output shaft.

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[ Wherein we claim:] [1.] A hydrostatic axial piston transmission having a continuously variable transmission ratio, comprising:an axial piston pump driven by an input shaft, said pump having an annular pump cylinder block with a ring of cylinders in which pump pistons reciprocate to pressurize and

[ Wherein we claim:] [1.] A hydrostatic axial piston transmission having a continuously variable transmission ratio, comprising:an axial piston pump driven by an input shaft, said pump having an annular pump cylinder block with a ring of cylinders in which pump pistons reciprocate to pressurize and displace fluid from said pump cylinders, said pump pistons having piston heads coupled to an output shaft for conveying reaction torque from said input shaft directly to said output shaft as a first output torque component;an axial piston hydraulic motor having an annular motor cylinder block with a ring of motor cylinders in which motor pistons reciprocate in a power stroke to apply output torque to said output shaft, and a displacement stroke in which spent fluid is displaced from said motor cylinders for return to said pump cylinders;said pump cylinder block being concentrically disposed within the annulus of said motor cylinder block, and said input shaft and said output shaft lying on a longitudinal axis through said annulus;a wobble plate coupled to and driven by said input shaft and having a flat surface in contact with said pump cylinder block, said flat surface lying at an angle to said longitudinal axis;said wobble plate flat surface having a first slot opening therein for conveying fluid pressurized and displaced by said pump pistons through first passages in said wobble plate, and also having a second slot opening in said flat surface for conveying spent fluid conveyed through second passages in said wobble plate from said motor cylinders back to said pump cylinders in a suction stroke of said pump pistons;a port ring having a face in contact with said wobble plate and having pressure fluid slots opening in said face for conducting fluid pressurized in said pump and conducted through said first slot in said wobble plate and said first passages in said wobble plate to pressure passages in a housing block, and also having suction fluid slots opening in said face for conducting spent fluid displaced from said motor through suction fluid passages in said housing block and back to said wobble plate second passages by way of said suction fluid slots; andan annular cam plate having a cylindrical surface engaged with a corresponding cylindrical surface on said housing block for tilting at an angle relative thereto about an axis transverse to said longitudinal axis, said cam plate having a flat annular surface in contact with a corresponding flat annular surface on said motor cylinder block and having a pressure slot opening in said cam surface in fluid communication with said motor cylinders, and having a pressure passage through said cam plate communicating with a pressure slot opening in said cylindrical surface of said cam plate in fluid communication with a corresponding pressure slot in said cylindrical surface on said housing block in fluid communication with said pressure passages in a housing block;whereby rotation of said input shaft drives said wobble plate to rotate and cause said pump cylinder block to nutate in contact with said wobble plate flat surface, thereby causing said pump pistons to reciprocate in said pump cylinders and displace pressurized fluid through said wobble plate while also transmitting reaction torque to said output shaft, said pressurized fluid being commutated by said wobble plate and conveyed through said port ring, said housing block pressure passage, and said cam plate pressure passage to said motor where said pressurized fluid energizes said motor to produce a second component of output torque in said output shaft.