Sauer-Danfoss Inc.

Danfoss Power Solutions Gmbh & Co Ohg

Sauer-Danfoss Gmbh & Co. Ohg

Reinhardt Thoms

Carsten Fiebing

Martin Wuestefeld

Bernd Hames

Peter Bahna

Martin Wüstefeld

Andrej Babusa

Markus Reimer

Sumeru Gourbidanur Srinivasamurthy

Sebastian Bujna

Peter Chlebana

Michael Knazek

Manual displacement control device (MDC) for hydraulic units has an input shaft mounted rotatably about an input shaft axis in an input shaft block. The input shaft protrudes from the input shaft block with a first end, onto which a rotating torque can be applied. The MDC further includes a control spool housed in a control housing, which is moveable by rotating the input shaft for controlling a servo pressure. The control device is configured for adjusting and fixing the lateral position of the input shaft with respect to the control housing in a direction perpendicular to the input shaft axis and perpendicular to the direction of a restoring force exerted on the input shaft.

Neutral setting device of an adjustable hydraulic unit

Manual displacement control device (MDC) for hydraulic units has an input shaft mounted rotatably about an input shaft axis in an input shaft block. The input shaft protrudes from the input shaft block with a first end, onto which a rotating torque can be applied. The MDC further includes a control spool housed in a control housing, which is moveable by means of rotating the input shaft for controlling a servo pressure. The control device has positioning means for adjusting and fixing the lateral position of the input shaft with respect to the control housing in a direction perpendicular to the input shaft axis and perpendicular to the direction of a restoring force exerted on the input shaft. The hydraulic unit is adjustable to its neutral position by means of a servo spring bracket providing an end stop surface for a servo spring seat towards the displacement element. The servo spring bracket is variably fixable to the hydraulic unit housing in a manner so that the orientation of the end stop surface can be adjusted parallel to the neutral position of the displacement element.

The invention relates to a high-pressure hydraulic fluid screening element () for inserting into a hydraulic line or into a hydraulic connection of a hydraulic device, having an annular main body (), which is aligned with respect to its axis of rotation () in a longitudinal direction (). The outside diameter of the main body () is greater than its axial length. The inner cross section of the main body () is covered over by a screening region (), which is provided with a multiplicity of apertures (). In this case, the main body () and the screening region () are produced integrally by the powder injection-molding process.

Screen for hydraulic fluid

Displacement control device for providing pressure fluid to a servo unit for adjusting the displacement of a pressure fluid unit, having a control cylinder in which a control spool is mounted shiftable along the longitudinal axis of the control cylinder, an inlet port, a servo port and a discharge port are formed in the control cylinder longitudinally spaced from each other, wherein the control spool comprising: a basically cylindrical outer surface; a front face on which an actuation force can act for shifting the control spool along the longitudinal axis; a discharge area opposite to the front face; a longitudinal bore inside the control spool, wherein one end of the longitudinal bore opens towards the front face and the other end is connected via a backpressure orifice with the discharge area; a control recess provided lengthwise in the outer surface; a radial bore which connects via a flow limiting orifice the longitudinal bore with the outer surface, wherein the opening of the radial bore at the outer surface is located in circumferential direction beside the control recess, such that the opening of radial bore overlaps with the servo port in an actuated position of the control spool, in which the control recess connects the inlet port with the servo port.

Displacement control device

Pressure relief valve () comprising a valve housing (), in which a double-side operable cylindrical pressure relief valve spool () is housed slidable along a longitudinal axis () of a cylindrical bore () in the valve housing (). The pressure relief valve spool () can be shifted into a first position by a first force acting on an actuating side () of the pressure relief valve spool () and can be shifted into a second position by a pressure force acting on a sealing side () of the pressure relief valve spool (). On the sealing side () of the pressure relief valve spool () a double-sealing, rotational symmetric poppet () is located having a rotational axis (), a first convex sealing surface () and a second convex sealing surface (). The first sealing surface () facing away from the pressure relief valve spool () is provided for sealing with an external valve seat (). The second sealing surface () facing to the stepped bore () in the valve spool () is provided for sealing with the smaller diameter of the stepped bore (). The poppet () and the rotational axis () of the poppet () are tiltable with respect to the longitudinal axis () of the cylindrical bore () in the pressure valve housing ().

Pressure valve

A Control unit of a hydraulic unit comprises a control piston slidable arranged in a control cylinder to provide a hydraulic fluid under servo pressure at a first outlet of the control unit suitable for the displacement of the hydraulic unit. The servo pressure is proportional to a sum of the inner forces of the hydraulic unit and the operational forces act on the control unit. The hydraulic fluid provided at the outlet is fed by a charge pressure supply at charge pressure at an inlet of the control unit. The control piston has a blind bore in the direction of a longitudinal axis of the control unit, in which a pressure relief valve is arranged functioning as a pilot-control unit having a two-sided pressure relief piston arranged in the blind bore and slidable relative to the control piston by means of an actuator.

Displacement control unit

The invention relates to a displacement unit () of a hydraulic machine, for which the hysteresis is reduced. For this purpose, in the control spool () and/or at the control spool () a mass body () and a spring () are arranged, which are excited to resonance vibrations. The vibrations are self-excited and sustained by a partial flow rate of the hydraulic fluid which is modulated periodically. The high frequent vibrations are transmitted over the spring () onto the associated control spool (), thereby reducing the friction and hence the hysteresis.

Hydrostatic displacement unit with reduced hysteresis

Method for deceleration of a hydrostatic transmissiondriven by a drive motorcomprising a closed hydraulic fluid circuit, in which a hydraulic pumpcoupled mechanically with the drive motorand a hydraulic motorare arranged. Two hydraulic linesconnect the hydraulic pumpand the hydraulic motorand constitute for the hydraulic motoraccording to the drive direction of the hydrostatic transmissiona supply lineand a return line. In at least one of the two hydraulic linesa throttle valveis arranged being adjustable in its throttle cross section which, if the corresponding hydraulic lineis a return linefor hydraulic fluid under high pressure towards the hydraulic pumpis being adaptable in its throttle cross section dynamically such that the adjustable hydraulic power in return linedownstream of throttle valveat any time during a coasting mode corresponds to the maximum power being supportable at the drive motorin consideration of the power consumption of auxiliary consumersand power losses.

Method and arrangement for the deceleration of a hydrostatic transmission

Hydrostatic adjusting device of a hydraulic machine, the swept volume of which can be adjusted by way of a servo adjusting unit, having a control unit which has a control cylinder which has at least one inlet for pressurized hydraulic fluid, at least one servo connector for a connecting line to the servo adjusting unit, and at least one outlet to a hydraulic fluid collecting region. A control piston is arranged in the control cylinder, which control piston can be displaced by means of at least one control piston actuator and has control edges. In interaction with control edges which are configured in the control cylinder, the inlet or the outlet can be alternately connected hydraulically to the connecting line, whereby the pressure which prevails in the connecting line can be returned hydraulically via a control line to at least one end side of the control piston.

Switchable hydrostatic adjusting device

The invention concerns a hydrostatic drive with a closed hydraulic fluid circuit comprising a hydraulic motor and a variable displacement pump. A feed pump feeds hydraulic fluid under pressure. A control device regulates pressure to a double-sided servo control unit comprising a control piston in a double-sided control cylinder so that the control piston can open a feed line for hydraulic fluid to one side while opening a discharge line on the other. The control device comprises an actuator at the cylinder by means of which force can be exerted onto the piston. A preload element exerts force onto the piston. The pressure generated by the variable displacement pump returns via a return line such that force is exerted in the direction of the piston, if inactive, the piston is maintained by the preload element and the pressure of the variable displacement pump.

Control device for hydrostatic drives

The invention relates to a neutral setting apparatus for adjustable hydraulic machines, in particular the adjustment of the neutral position of a servo valve. In particular, the invention relates to servo adjustment devices with mechanically adjustable control pistons, wherein the forces necessary for this can be applied mechanically, electro-magnetically, pneumatically or hydraulically. The invention relates to a neutral setting apparatus of an adjustable hydraulic machine, with a housing in which a mounted input shaft is arranged, to one end of which a torque can be applied for rotating the input shaft about an axis. Thus providing a robust and cost-effective setting mechanism for the neutral position of a servo valve.

Neutral setting apparatus of an adjustable hydraulic machine

The invention relates to an axial piston engine with a filling pump integrated in a receiving bore of the axial piston engine, which filling pump comprises a gerotor set with an externally toothed inner ring and an internally toothed outer ring and also an inner thrust plate and an outer thrust plate. The two thrust plates enclose the gerotor set between them and, on their surfaces facing away from the gerotor set, are in each case supported via a pressure field seal, which surrounds the pressure field regions formed in the thrust plates, in such a way on the housing walls axially enclosing the filling pump that lateral play in the form of axial mobility of the filling pump is guaranteed.

Axial piston engine with integrated filling pump

An arrangement for filtering a hydraulic fluid having a bypass line connecting the feed channel to the discharge channel where the bypass line is opened by a pressure switching valve when a pressure change is caused by the contamination of the filter element.

Arrangement for filtering hydraulic fluid

A hydrostatic variable displacement unit is provided having a swash plate which serves to adjust the stroke of displacement pistons in a cylinder block and can be pivoted in its angular position by means of a servo system, the servo system having at least one servo piston with two servo-piston end surfaces which are in each case assigned a servo cylinder and a servo-piston rear surface, and the servo cylinders, by means of the assigned servo-piston end surfaces, in each case bounding a servo-cylinder pressure space. The servo piston is acted upon by a spring arrangement having at least one spring arranged outside the servo-cylinder pressure space and clamped between two spring plates. The two spring plates are acted upon by the springs in the direction of a stop of the particular servo cylinder that is situated on its side such that in the neutral position, the spring plates bear against the servo-piston rear surfaces and against the stop of the particular servo cylinder.

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Neumunster, Germany

Reinhardt Thoms