A hydraulic motor apparatus includes a motor housing engaged to an end cap having a first porting system and an adapter connected to an external surface of the end cap and having a second porting system. A filter may be attached to the adapter and connected to the second porting system and a pressure reducing valve in the adapter is connected to the second porting system. The assembly may also include a controller operatively connected to the pressure reducing valve and system sensors measuring parameters affected by the output of the hydraulic motor apparatus, whereby the pressure reducing valve is operatively controlled by the controller in response to input from the system sensors.

A hydraulic motor apparatus includes a motor housing engaged to an end cap having a first porting system and an adapter connected to an external surface of the end cap and having a second porting system. A filter may be attached to the adapter and connected to the second porting system and a pressure reducing valve in the adapter is connected to the second porting system. The assembly may also include a controller operatively connected to the pressure reducing valve and system sensors measuring parameters affected by the output of the hydraulic motor apparatus, whereby the pressure reducing valve is operatively controlled by the controller in response to input from the system sensors.

A hydrostatic piston engine comprises a housing with a cylinder drum with cylinder bores mounted rotatably therein. Each of the cylinder bores receives a working piston in a longitudinally displaceable manner, via which a hydrostatic working chamber is delimited by the cylinder bore. The hydrostatic working chamber has an opening on an outer surface of the cylinder drum by which, when the cylinder drum rotates, outlets of a high-pressure chamber and of a low-pressure chamber of the piston engine and a reversing surface arranged between the two outlets in the rotational direction can be passed over in alternating fashion. At least one pressurizing medium channel is provided which, on one hand, opens out in the reversing surface and, on the other, into a pressurizing medium trough of the piston engine.

A hydrostatic piston engine comprises a housing with a cylinder drum with cylinder bores mounted rotatably therein. Each of the cylinder bores receives a working piston in a longitudinally displaceable manner, via which a hydrostatic working chamber is delimited by the cylinder bore. The hydrostatic working chamber has an opening on an outer surface of the cylinder drum by which, when the cylinder drum rotates, outlets of a high-pressure chamber and of a low-pressure chamber of the piston engine and a reversing surface arranged between the two outlets in the rotational direction can be passed over in alternating fashion. At least one pressurizing medium channel is provided which, on one hand, opens out in the reversing surface and, on the other, into a pressurizing medium trough of the piston engine.

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 rotary displacement piston pump is disclosed having rotatable single or dual valve/port plate(s). The valve plate, being rotatable forward and/or rearward with respect to the rotation of the piston carrier, alters the phasing of the land area of the pumping action thereby altering the phasing of piston speed inasmuch as the land area can be moved to a position to accelerate the piston(s) in a pre or decompression phase. In this way, pump noise, from colliding pressure fronts within the respective high and low pressure plenums, can be “tuned” out of the pump by adjusting the phasing and position of the valve plate(s) and raising or lowering the pre and decompression pressure(s) as necessary. Pump volume can also be controlled by advancing or retarding the valve plate(s), either in or out of synch, so as to shorten intake/exhaust piston stroke and overlap fluid flow between respective intake/exhaust plenums.

A displacement adjusting device of a swash plate pump includes: a tilting piston slidably inserted in a housing's accommodating hole, the tilting piston pressing the swash plate pump's swash plate; a sleeve forming a control pressure chamber between the sleeve and tilting piston, the sleeve including a pump port, tank port, and output port; a spool slidably held by the sleeve, the spool switching whether to bring output port into communication with one of the pump port and tank port or block the output port from the pump and tank port; a tilting spring urging the tilting piston and spool away from each other; and a solenoid including a rod that presses the spool from an opposite side to tilting spring. In the sleeve, reaction force chamber and communication passage are formed. The communication passage being a passage through which the control pressure chamber communicates with reaction force chamber.

A displacement adjusting device of a swash plate pump includes: a tilting piston slidably inserted in a housing's accommodating hole, the tilting piston pressing the swash plate pump's swash plate; a sleeve forming a control pressure chamber between the sleeve and tilting piston, the sleeve including a pump port, tank port, and output port; a spool slidably held by the sleeve, the spool switching whether to bring output port into communication with one of the pump port and tank port or block the output port from the pump and tank port; a tilting spring urging the tilting piston and spool away from each other; and a solenoid including a rod that presses the spool from an opposite side to tilting spring. In the sleeve, reaction force chamber and communication passage are formed. The communication passage being a passage through which the control pressure chamber communicates with reaction force chamber.

An inlet baffle chamber (40) is provided in the port cover (26) of a piston pump. The inlet baffle chamber (26) fluidly connects a compressed piston chamber to an adjacent lower pressure piston chamber while the lower pressure piston chamber is in the suction cycle and separately receiving fluid from an inlet manifold (38) of the port cover (26). Instead of de-compressing high pressure fluid directly to pump's inlet (36) as in prior art pumps, the inlet baffle chamber (40) directs fluid to the next piston that is already in the suction cycle.

A rotary displacement piston pump is disclosed having rotatable single or dual valve/port plate(s). The valve plate, being rotatable forward and/or rearward with respect to the rotation of the piston carrier, alters the phasing of the land area of the pumping action thereby altering the phasing of piston speed inasmuch as the land area can be moved to a position to accelerate the piston(s) in a pre or decompression phase. In this way, pump noise, from colliding pressure fronts within the respective high and low pressure plenums, can be tuned out of the pump by adjusting the phasing and position of the valve plate(s) and raising or lowering the pre and decompression pressure(s) as necessary. Pump volume can also be controlled by advancing or retarding the valve plate(s), either in or out of synch, so as to shorten intake/exhaust piston stroke and overlap fluid flow between respective intake/exhaust plenums.