Axial piston machine having double acting pistons and a rotary control valve

In an axial piston machine having at least three double-acting cylinders, a housing mounting said cylinders in operative relation to a main axis for reciprocation of pistons within the cylinders along axes parallel to the main axis, a crankshaft mounted by the housing for rotation about said main axis, and a linkage mechanism including connecting rods connected to the pistons and means for establishing wobble plate drive points at which the connecting rods are operatively connected to the crankshaft, the improvement comprising extension of the pistons projecting from the cylinders in surrounding relation to the connecting rods, a swivel joint directly mounted within each of the pistons through which the connecting rods pivotally connect to the pistons at the drive points, and a control valve assembly mounted in axially spaced alignment with the crankshaft radially inwardly of the cylinders, said control valve assembly including a valve body fixed to the housing, a valve rotor within the valve body rotatable about the main axis, radially extending ports establishing fluid communciation between the valve body and the cylinders on opposite axial sides of the pistons, and valve passage means in the valve rotor for conducting fluid to and from the ports in response to rotation of the rotor, said valve passage means including axially spaced pressure chambers formed in the rotor in axial alignment with the ports, axial conduit means in the rotor for conducting pressurized fluid to and from the chambers, and pressure cavity means in the rotor for balancing internal hydraulic forces resulting from pressurization of the chambers.