Filter device

1. A filter device, comprising:

a filter housing having at least one filter element configured to separate the filter housing into a raw side and a clean side,

a bypass valve for controlling a bypass circumventing the at least one filter element,

wherein the bypass valve has a valve member for controlling a bypass opening, which connects the clean side and a coupling chamber of the bypass valve the raw side,

wherein the valve member is configured to close the bypass opening via a pretension generated, at least partially, by a closing spring,

wherein the bypass valve has an actuating device for changing the pretension acting on the valve member, and wherein

the actuating device is coupled with at least one control chamber and is configured to set the pretension acting on the valve member based at least in part on a control pressure of the control chamber.

2. The filter device according to claim 1 ,

wherein the actuating device has an actuating member which separates the control chamber from the coupling chamber and which is adjustable as a function of a pressure difference between the coupling chamber and the control chamber for changing the pretension acting on the valve member.

3. The filter device according to claim 2 ,

wherein the closing spring is supported indirectly via the actuating member on one side and by an abutment fixed relative to the bypass opening on the other side.

4. The filter device according to claim 3 ,

wherein the closing spring and the actuating member are arranged on opposite sides with respect to the valve member.

5. The filter device according to claim 3 , wherein the actuating member and the closing spring are arranged on the same side with respect to the valve member.

6. The filter device according to claim 2 ,

the actuating member is a membrane which separates the coupling chamber from the control chamber.

7. The filter device according to claim 6 ,

wherein the control chamber is formed in a pressure cell, on which the membrane is arranged, wherein the control chamber is hermetically closed in the pressure cell,

wherein the pressure cell has a dividing wall containing the bypass opening, and

wherein the pressure cell and the bypass valve form a separate valve assembly with respect to the filter housing.

8. The filter device according to claim 7 ,

wherein the valve assembly is arranged on the filter element, and

the valve assembly and the filter element form a unit incorporated exchangeably into the filter housing.

9. The filter device according to claim 2 ,

wherein the actuating member is a piston configured to be stroke-adjustable in a cylinder and separate the cylinder into the coupling chamber and the control chamber.

10. The filter device according to claim 9 ,

wherein the cylinder is formed integrally in the filter housing, and

the control chamber is connected in a communicating manner via a connection opening with an environment of the filter housing.

11. The filter device according to claim 2 ,

further comprising an actuating member spring configured to pretension the actuating member in a direction reinforcing the pretension.

12. The filter device according to claim 2 ,

further comprising a first end stop configured to limit the adjustment path of the actuating member in a direction reinforcing the pretension, and

a second end stop configured to limit the adjustment path of the actuating member in a direction reducing the pretension.

13. The filter device according to claim 2 , wherein the closing spring is supported indirectly via a coupling rod, wherein the coupling rod connects the actuating member securely with the valve member so that an adjustment of the actuating member leads to an adjustment of the valve member.

14. The filter device according to claim 13 , wherein the closing spring is supported by the valve member on one side and by the coupling rod on the other side, wherein the coupling rod is securely connected with the actuating member so that an adjustment of the actuating member leads to a change of the pretension of the closing spring.

15. The filter device according to claim 14 , wherein the valve member is stroke-adjustable along the coupling rod.

16. The filter device according to claim 2 , wherein the closing spring is supported directly on the actuating member.

17. The filter device according to claim 1 ,

wherein the control chamber is at least one of hermetically closed, communicates with an environment of the filter housing, and is coupled with a control device for setting the control pressure.

18. The filter device according to claim 1 ,

further comprising a cylinder including the coupling chamber, wherein the actuating device has an actuating member adjustable for changing the pretension acting on the valve member, and configured as a piston, further wherein the piston separates the cylinder into a first control chamber and a second control chamber.

19. The filter device according to claim 18 ,

wherein the first control chamber is able to be acted on with a control pressure via a control pressure connection and the second control chamber is connected in a communicating manner via a connection opening with an environment of the filter housing.

20. The filter device according to claim 18 , wherein the second control chamber is able to be acted on via a further control pressure connection with a different control pressure.