Danfoss Power Solutions Gmbh & Co Ohg

Arne Streblau

Bernd Hames

Martin Wüstefeld

Suenje Marsch

Michael Hein

Hydraulic fluid flushing valve for hydrostatic units usable in closed hydraulic circuit propel applications, having a flushing valve housing with a first inlet port connected to a first working line, a second inlet port connected to a second working line, and a discharge port for draining hydraulic fluid. A two-sided flushing valve flushing valve spool which can be shifted is mounted within the flushing valve housing in a cylindrical valve bore, which, in a shifted position, enables a fluid flow from one of the first or the second inlet port at which the lower hydraulic pressure is present, to the discharge port. The flushing valve spool includes on each side a pressure surface each of which is connected to one of the two inlet ports. At each side of the flushing valve spool a flushing valve spring is located in the flushing valve housing in such a manner that, when the flushing valve spool is in its centre, non-shifted position, at each side of the flushing valve spool a distance between a spring contact surface on the flushing valve spool and a spring support surface in the flushing valve housing is greater than the axial length of the corresponding flushing valve spring.

Loop flushing system for hydraulic units

The invention relates to a hydraulic machine, in particular to a hydraulic motor with two working lines, from one of which a high pressure line and from the other one a low pressure line is branched off. An electronic control unit and a servo displacement unit are provided to control the displacement of the displacement volume of a drive mechanism of the hydraulic machine, wherein the displacement volume can be determinated by the displacement of a servo piston within the servo displacement unit. For this, the servo piston can be loaded at least on one side via a servo pressure line with hydraulic fluid under servo pressure, wherein the servo pressure level can be adjusted by a control spool arranged moveable within a control valve. For this, hydraulic fluid from the low pressure line or, perhaps, from the high pressure line is guidable via the control valve to the servo pressure line if a suitable control signal is available at a switching valve.

Device and method for controlling a hydraulic machine

A valve housing includes a cylindrical valve bore with a high pressure inlet, a low pressure inlet and a discharge outlet. A first flushing valve spool is arranged elastically pre-stressed within the valve bore for enabling a fluid connection between the low pressure inlet and the discharge outlet. A shuttle valve spool is arranged elastically pre-stressed within the valve bore for enabling the fluid connection between the low pressure inlet and the discharge outlet. The first flushing valve spool is moveable into an open position if the fluid pressure at the low pressure inlet exceeds a first threshold value, and the shuttle valve spool is moveable into an open position for connecting the low pressure inlet with the discharge outlet, if the pressure difference between the high pressure inlet and the low pressure inlet exceeds a second threshold value.

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Nortorf, Germany

Arne Streblau