A hydraulic pump includes a cylinder block, a plurality of pistons, a swash plate, a first pressing unit, and a second pressing unit. The cylinder block has a plurality of cylinder bores and is disposed so as to be rotatable. Each of the plurality of pistons is retained in associated one of the cylinder bores so as to be movable. The swash plate is configured for controlling the amount of movement of the plurality of pistons in accordance with the size of the tilt angle. The first pressing unit is configured for pressing the swash plate in such a direction as to reduce the tilt angle of the swash plate. The second pressing unit is configured for pressing the swash plate in such a direction as to increase the tilt angle of the swash plate by a pressure supplied from the outside of the hydraulic pump.

In accordance with at least one aspect of this disclosure, a variable displacement pump system can include, a variable displacement pump disposed in a main line and configured to supply pressure to receive a low pressure fluid and to output a high pressure fluid. The main line can connect a hydraulic fluid source to a plurality of system actuators, where the variable displacement pump is disposed in the main line between the hydraulic fluid source and the plurality of system actuators to pressurize the hydraulic fluid.

An axial piston machine has a swash plate and an adjusting device having an adjusting cylinder and a double-acting adjusting piston which is longitudinally movable in the adjusting cylinder and includes a piston and a piston rod, which is fixedly connected to the piston and is articulated to the swash plate. The joint between the adjusting piston and the swash plate is a movable swivel joint having a joint body receptacle on one part and a joint body on the other part of the adjusting piston and the swash plate. The joint body is closely guided in the joint body receptacle in the direction of movement of the adjusting piston, is rotatable about an axis of rotation running parallel to the pivot axis of the swashplate, and is movable with a directional component perpendicular to the direction of movement of the adjusting piston and perpendicular to the axis of rotation.

An axial piston machine has a swash plate and an adjusting device having an adjusting cylinder and a double-acting adjusting piston which is longitudinally movable in the adjusting cylinder and includes a piston and a piston rod, which is fixedly connected to the piston and is articulated to the swash plate. The joint between the adjusting piston and the swash plate is a movable swivel joint having a joint body receptacle on one part and a joint body on the other part of the adjusting piston and the swash plate. The joint body is closely guided in the joint body receptacle in the direction of movement of the adjusting piston, is rotatable about an axis of rotation running parallel to the pivot axis of the swashplate, and is movable with a directional component perpendicular to the direction of movement of the adjusting piston and perpendicular to the axis of rotation.

A piston pump includes: a first biasing mechanism configured to bias a swash plate in accordance with control pressure supplied; a second biasing mechanism configured to bias the swash plate against the first biasing mechanism; and a regulator configured to control the control pressure in accordance with self-pressure of the piston pump. The regulator has: an outer spring and an inner spring configured to be extended and compressed by following tilting of the swash plate; a control spool configured to be moved in accordance with biasing forces exerted by the outer spring and the inner spring, the control spool being configured to adjust the control pressure; an auxiliary spring configured to exert biasing force to the control spool against the biasing forces exerted by the outer spring and the inner spring; and an adjusting mechanism configured to adjust the biasing force exerted by the auxiliary spring.

A piston pump includes: a first biasing mechanism configured to bias a swash plate in accordance with control pressure supplied; a second biasing mechanism configured to bias the swash plate against the first biasing mechanism; and a regulator configured to control the control pressure in accordance with self-pressure of the piston pump. The regulator has: an outer spring and an inner spring configured to be extended and compressed by following tilting of the swash plate; a control spool configured to be moved in accordance with biasing forces exerted by the outer spring and the inner spring, the control spool being configured to adjust the control pressure; an auxiliary spring configured to exert biasing force to the control spool against the biasing forces exerted by the outer spring and the inner spring; and an adjusting mechanism configured to adjust the biasing force exerted by the auxiliary spring.

There is disclosed a hydrostatic axial piston machine having a pulse reduction device. This device has a connection location or tap in the transition region in front of the high-pressure-side kidney-like elongate hole of a distributor plate. The connection location or tap is connected by means of one or two hydraulically passively controlled switching valves to a high-pressure store. It is used for precompression and consequently for the pulse reduction. In a development, the distributor plate also has a connection location or tap in the transition region behind the high-pressure-side kidney-like elongate hole. The connection location or tap is connected via one or two hydraulically passively controlled switching valves to a low-pressure store. This is used for the decompression and consequently also for the pulse reduction.

There is disclosed a hydrostatic axial piston machine having a pulse reduction device. This device has a connection location or tap in the transition region in front of the high-pressure-side kidney-like elongate hole of a distributor plate. The connection location or tap is connected by means of one or two hydraulically passively controlled switching valves to a high-pressure store. It is used for precompression and consequently for the pulse reduction. In a development, the distributor plate also has a connection location or tap in the transition region behind the high-pressure-side kidney-like elongate hole. The connection location or tap is connected via one or two hydraulically passively controlled switching valves to a low-pressure store. This is used for the decompression and consequently also for the pulse reduction.

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.

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.