A hydraulic system includes a piston, a swash plate opposed to the piston, and a swash plate supporting member supporting the swash plate so that a tilt of the swash plate is variable. An oil reservoir portion is provided between the swash plate and the swash plate supporting member, the oil reservoir portion communicating with a pressure oil introducing passage. An area of the oil reservoir portion between the swash plate and the swash plate supporting member varies with the tilt of the swash plate.

A drive device includes a housing forming a sump. A pump and motor are mounted on a center section having a porting system and a pair of ports with check plugs disposed therein. A bypass arm is engaged to one end of a bypass shaft external to the housing and rotates the bypass shaft to selectively cause engagement fingers to move each check plug to an open position. A housing projection is contacted by the bypass arm to selectively limit rotation thereof. The axes of rotation of a swash plate trunnion shaft, a pump input shaft and a motor output shaft may all be disposed in a single plane. The input shaft is supported by a housing bearing and an opening in the center section and is restrained from axial movement by the bearing and a thrust surface on the center section.

A cylinder block for use in an integrated drive generator has a shaft portion with a relatively small outer diameter and a cylindrical body portion having a larger outer diameter than the shaft portion, and said cylindrical body portion formed with a plurality of piston chambers, said cylindrical body portion extending from a first end to a second end, said second end being provided with cylindrical ports leading into said piston chambers and said cylindrical ports having a third end and a fourth end wherein a ratio of a first distance from said first end to said fourth end to a second distance from said first end to said second end being between 0.91 and 0.93. A generator and a method are also described.

An axial piston pump, particularly for hydraulic systems, includes a cylinder drum (1) rotationally driven about an axis (15) in a pump housing (7). Piston cylinder units are arranged in the drum in a circle at an offset. Pistons (21) are at least indirectly supported on a swashplate (3) by their actuation end (31) accessible outside the cylinder drum (1). Between the swept volumes (19) of the piston cylinder units and a stationary fluid inlet and stationary fluid outlet of the pump housing (7), a control device (23) is arranged that has fluid channels (25, 26) for the targeted transfer of fluid from the fluid inlet into the swept volumes (19) and from the swept volumes (19) to the fluid outlet. At least one pressure compensation channel (28, 30) is provided in the control device (23), between the fluid channels (25, 26), to build or release fluid pressure in the swept volumes (19) in a targeted manner.

Devices and methods for improving the efficiency of an axial piston hydraulic motor or other axial piston hydraulic device. In some embodiments, a valve cam, with specified geometry, is assembled to a conventional axial piston hydraulic device (e.g., hydraulic motor, hydraulic pump, hydraulic pump-motor) in a manner permitting selective rotation of the valve cam relative to the distributor valves (e.g., spool valves). The rotating valve cam facilitates variable piston stroke and can be provided in conjunction with (e.g., joint control) an adjustable swashplate according to a mathematical relationship in order to adjust the displacement of the axial piston hydraulic motor (or other device) while maintaining optimal pre-compression and decompression across a range of operating conditions. This configuration allows, for each desired effective displacement of the hydraulic motor, a set of optimal valve timing to achieve perfect pre-compression and decompression so as to eliminate associated throttling losses.

Hydraulic axial piston unit having a rotational group for driving or being driven by a driving shaft, and a tiltable displacement element for adjusting the displacement volume of the rotational group. The rotational group includes a rotatable cylinder block in which working pistons are mounted reciprocally moveable in cylinder bores for conveying hydraulic fluid from an inlet port to an outlet port on a valve segment. At least two control ports are located on the valve segment each between the inlet port and the outlet port. The control ports can be brought sequentially in fluid connection with the cylinder bores when the cylinder block is rotating. At least one hydraulic fluid injector is connected fluidly to one control port, for sequentially injecting pressurized hydraulic fluid via the control port into the passing cylinder bores. Via the other control port hydraulic fluid can be drained from passing cylinder bores.

Methods and systems for a bent axis motor are described. In one example, a bent axis motor includes a valve plate coupled to at least one piston of a cylinder block, the valve plate comprising a first plurality of grooves spaced about openings of the valve plate on a first side of the valve plate facing the cylinder block, the valve plate further comprising a second plurality of grooves arranged on a second side of the valve plate facing away from the cylinder block.

An articulated coupling is provided for a piston sealing device for a piston which includes a fixed skirt and a sliding skirt interconnected by a mechanical inter-skirt connection for axially compressing a continuous extensible segment under the action of a sliding skirt spring, the coupling replacing, on the one hand, the fixed skirt by a ball-joint skirt and providing, on the other hand, a troncospherical piston end which cooperates with a skirt troncospherical bearing surface provided on the ball joint skirt while an articulation unit interposed between the inter-skirt mechanical connection and the piston and/or between the connection and the sliding skirt.

In a drive device using a hydraulic pump controlled by a rotatable swash plate, the swash plate includes a pocket and a trunnion engaged to the pocket and rotatable about an axis of rotation offset from the swash plate axis of rotation. An interface is formed on a first end of the trunnion, and a first arcuate side of the interface engages a flat portion of the first side of the pocket as the trunnion is rotated in a first direction, and a second arcuate side of the interface engages a flat portion of the second side of the pocket as the trunnion is rotated in the opposite direction. The swash plate may also include at least one protrusion on a top surface extending in a direction perpendicular to swash plate axis of rotation to engage the housing and limit axial movement of the swash plate.

An opposed piston engine has a driveshaft with a spaced apart cams mounted thereon. Each cam has a circumferential cam shoulder of a curvilinear shape selected to enhance flow through intake and exhaust ports. The curvilinear shape may be a segmented polynomial shape forming lobes which lobes are asymmetrical so that the lobe wavelength distance from a first trough to the lobe peak of an ascending shoulder portion of the lobe is greater than the lobe wavelength distance from the peak to a second trough of a descending shoulder portion of the lobe. Opposing cam shoulders may be shaped so as to always be converging or diverging from one another.