Variable hydraulic transformer

Pumps in hydrostatic drivelines control fluid flow, but energy-source dynamics often induce low-frequency oscillations in long hydraulic-line circuits. Common pressure rail (CPR) systems eliminate such oscillations, offering more precise control by effectively isolating load from the energy source. Driving all loads individually from the secondary side of a pressure rail also reduces throttling losses to improve efficiency.

However, driving all loads from the same predefined rail pressure requires input pressure and flow-rate variations at each load. As a result, driving rotary loads requires fast and expensive actuators for changing a variable motor's swash-plate angle.

To reduce size, weight, cost, and improve efficiency, the Innas hydraulic transformer (IHT), combines pumping and motoring parts into one axial piston unit. To do this, the design uses a swiveling port plate with three, instead of two, kidney-shaped ports. One port connects to the supply line, another to the tank, and the third to the load pressure. When the transformer's barrel rotates, the cylinders pass the three kidneys sequentially. Depending on the pressure in each kidney and the cylinder position relative to the top of the dead center of the plunger movement, the plungers contribute to the torque on the barrel. As in conventional transformers, when the actual pressure ratio differs from the transformation factor, the unit accelerates or decelerates until the theoretical transformation factor is reached again.

Peter Achten,Innas,Nikkelstraat 15 NL-4823 AE breda, The Netherlands; Tel: 31 76 542 4080; Fax: 31 76 542 4090; E-mail:[email protected].

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