Electrohydraulic drive unit
An electrohydraulic drive unit is provided, comprising a cylinder-piston assembly having a piston-side first hydraulic working chamber and a piston-rod-side second hydraulic working chamber, a tank, a hydraulic pump, which can be driven at variable rotational speed and which has a tank connection point and a working connection point, a valve assembly, which is connected between the working connection point of the hydraulic pump and the cylinder-piston assembly, and an anti-cavitation valve, which is connected between the tank and the first hydraulic working chamber; and a machine controller. Switching valves of the valve assembly can be switched between loading of the first hydraulic working chamber and loading of the second hydraulic working chamber of the cylinder-piston assembly during pumping operation of the hydraulic pump from the working connection point of the hydraulic pump by the machine controller.
1. An electrohydraulic drive unit, especially for use on a machine press, having
a cylinder-piston arrangement ( 1 ) having a first hydraulic working chamber ( 5 ) on the piston side and a second hydraulic working chamber ( 6 ) on the piston-rod side
a tank ( 4 ) as a hydraulic-fluid reservoir,
a hydraulic pump ( 3 ) driven at variable rpm by an electric motor ( 2 ) and having a tank port (T) and a working port (P),
a valve arrangement connected between the working port (P) of the hydraulic pump ( 3 ) and the cylinder-piston arrangement ( 1 ) and comprising several electrically activatable switching valves (S 1 -S 6 ),
a servo-suction valve ( 8 ) connected between the tank ( 4 ) and the first hydraulic working chamber ( 5 ) of the cylinder-piston arrangement ( 1 ),
and a machine controller acting on the switching valves (S 1 -S 6 ) and on the electric motor ( 2 ), by means of which the switching valves (S 1 -S 6 ) can be reversed between pressurization of the first hydraulic working chamber ( 5 ) and of the second hydraulic working chamber ( 6 ) of the cylinder-piston arrangement ( 1 ) in pumping mode of the hydraulic pump ( 3 ) from its working port (P),
wherein a hydraulic decompression module ( 9 ) having a hydraulic accumulator ( 10 ), which can be placed in communication with the second hydraulic working chamber ( 6 ) via a first connecting line ( 11 ) having a pressure-limiting valve ( 15 ) having flow direction from the second hydraulic working chamber ( 6 ) to the hydraulic accumulator ( 10 ) and via a second connecting line ( 12 ) having a check valve ( 16 ) opening in flow direction from the hydraulic accumulator ( 10 ) to the second hydraulic working chamber ( 6 ).
2. The electrohydraulic drive unit of claim 1 , wherein the hydraulic decompression module ( 9 ) comprises a loading/unloading valve ( 14 ).
3. The electrohydraulic drive unit of claim 2 , wherein the loading/unloading valve ( 14 ) is disposed in a line section ( 13 ) common to the first connecting line ( 11 ) and the second connecting line ( 12 ).
4. The electrohydraulic drive unit of claim 2 , wherein the loading/unloading valve ( 14 ) opens in pressure-controlled manner, wherein the control-pressure line ( 17 ) communicates with the first hydraulic working chamber ( 5 ).
5. The electrohydraulic drive unit of claim 4 , wherein the loading/unloading valve ( 14 ) is of pressure-actuated design.
6. The electrohydraulic drive unit of claim 4 , wherein the loading/unloading valve ( 14 ) can be actuated by a pressure-controlled positioning drive.
7. The electrohydraulic drive unit of claim 2 , wherein the loading/unloading valve ( 14 ) can be actuated by a sequence-controlled positioning drive, which communicates with the machine controller.
8. The electrohydraulic drive unit of claim 2 , wherein the loading/unloading valve ( 14 ) can be manually actuated.
9. The electrohydraulic drive unit of claim 1 , wherein the cylinder-piston arrangement ( 1 ) is oriented with at least substantially vertical axis of movement (X) of piston ( 7 ), wherein the first hydraulic working chamber ( 5 ) is disposed above second hydraulic working chamber ( 6 ).
10. The electrohydraulic drive unit of claim 1 , wherein a filter unit ( 18 ) is connected between the working port (P) of the hydraulic pump ( 3 ) and the valve arrangement.
11. The electrohydraulic drive unit of claim 1 , wherein the hydraulic pump ( 3 ) is designed as a 2-quadrant pump and can be reversed by means of the machine controller in braking mode such that the directions of rotation and flow are reversed compared with pumping mode.