A hydraulic pressure compensating pump assembly having a fluid flow regulation mechanism is provided. The fluid flow regulation mechanism is set to an initial stroked position that can be adjusted to accommodate various applications. The fluid flow regulation mechanism includes a biasing means that allows the pump to de-stroke in response to a pressure demand increase and to return to the initial pressure set point when pressure demand subsides sufficiently. Different spring types and spring rates can be specified to achieve a desired response to pressure demand fluctuations within a particular hydraulic circuit.

A hydraulic pressure compensating pump assembly having a fluid flow regulation mechanism is provided. The fluid flow regulation mechanism is set to an initial stroked position that can be adjusted to accommodate various applications. The fluid flow regulation mechanism includes a biasing means that allows the pump to de-stroke in response to a pressure demand increase and to return to the initial pressure set point when pressure demand subsides sufficiently. Different spring types and spring rates can be specified to achieve a desired response to pressure demand fluctuations within a particular hydraulic circuit.

The invention relates to a device for supplying ports to a machine section (26) of a hydraulic machine arrangement (40), the device (10) comprising a low-pressure inlet port (12), a leakage inlet (16), a low-pressure chamber (18) having a low-pressure opening (22) for establishing fluid communication with the machine section (26), a high-pressure outlet port (14), and a high-pressure chamber (20) that is in fluid communication with the high-pressure outlet port (14), the high-pressure chamber (20) having a high-pressure opening (24) for establishing fluid communication with the machine section (26), wherein the low-pressure inlet port (12) is in fluid communication with the low-pressure chamber (18), wherein a leakage path (36) extends from the high-pressure chamber (20) through the machine section (26) to the leakage inlet (16), characterized in that the device (10) further comprises a control valve member (28) connecting the leakage inlet (16) to the low-pressure chamber (18), wherein the control valve member (28) transfers to an open state when a pressure in the leakage inlet (16) with respect to a pressure in the low-pressure chamber (18) is higher than a predefined control pressure threshold. The device (10) reduces cavitation in hydraulic machine arrangements (40).

Provided are hydraulic systems comprising variable speed drives coupled to hydraulic pumps and methods of operating such systems. The drive speed is controlled based on the position of a hydraulic servo-control valve in order to reduce the flow through a bypass line. Specifically, the drive speed may be decreased as the valve is opening and sending a greater portion of the hydraulic fluid into the bypass line. This approach allows to reducing losses in the bypass line thereby increasing the overall efficiency of the hydraulic system. The position of the hydraulic servo-control valve may be determined using a position sensor or a flow sensor. Alternatively, the position may be estimated by increasing the drive speed and monitoring the pressure change in the hydraulic actuator. The differential pressure-speed ratio obtained during this speed increase is compared to a calibration set of values corresponding to different valve positions.

Provided are hydraulic systems comprising variable speed drives coupled to hydraulic pumps and methods of operating such systems. The drive speed is controlled based on the position of a hydraulic servo-control valve in order to reduce the flow through a bypass line. Specifically, the drive speed may be decreased as the valve is opening and sending a greater portion of the hydraulic fluid into the bypass line. This approach allows to reducing losses in the bypass line thereby increasing the overall efficiency of the hydraulic system. The position of the hydraulic servo-control valve may be determined using a position sensor or a flow sensor. Alternatively, the position may be estimated by increasing the drive speed and monitoring the pressure change in the hydraulic actuator. The differential pressure-speed ratio obtained during this speed increase is compared to a calibration set of values corresponding to different valve positions.

A hydraulic machine includes a housing interior space and a group of hydrostatic working chambers which are mounted in said housing interior space so as to be rotatable about an axis of rotation and which, as the group rotates, are connectable alternately to a high pressure and to a low pressure of the hydraulic machine and exhibit leakage into the housing interior space. A heat exchanger device is accommodated in the housing interior space. The hydraulic machine may be associated with a hydraulic assembly and a hydraulic axle.

Ports (11 and 12) are formed in a port plate (10). A plurality of valve plate holes are arranged on a circumference around the rotation axis (S). The port plate (10) includes a plurality of bridges (13) configured to divide the port (11) into a circumferential direction to provide a plurality of port holes (11a), and a plurality of bridges (14) configured to divide the port (12) into the circumferential direction to provide a plurality of port holes (12a). A summation of the number of port holes (11a) and the number of port holes (12a) is greater than the number of valve plate holes.

Ports (11 and 12) are formed in a port plate (10). A plurality of valve plate holes are arranged on a circumference around the rotation axis (S). The port plate (10) includes a plurality of bridges (13) configured to divide the port (11) into a circumferential direction to provide a plurality of port holes (11a), and a plurality of bridges (14) configured to divide the port (12) into the circumferential direction to provide a plurality of port holes (12a). A summation of the number of port holes (11a) and the number of port holes (12a) is greater than the number of valve plate holes.

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.