Camshaft adjuster of an internal combustion engine

1. A camshaft adjuster for an internal combustion engine comprising a control valve ( 3 ) having a control piston ( 5 ) slidably supported in a valve housing ( 6 ), an operating unit ( 4 ) for adjusting the angular position of the camshaft ( 12 ) relative to the crankshaft of the internal combustion engine, a drive unit ( 8 ) with an electric motor ( 15 ) and a transmission structure ( 16 ) for moving the control piston ( 5 ) in a forward direction ( 17 ) against the force (f spring ) of a spring ( 9 ) into an equilibrium position between the force of the spring ( 9 ) and the adjustable force generated by the drive unit ( 8 ), said transmission structure ( 16 ) being non-self-locking and said spring ( 9 ) being capable of moving the control piston ( 15 ) and the drive unit ( 18 ) in a backward direction against a control force (f control ) provided by drive unit ( 8 ) in the equilibrium position.

2. A camshaft adjuster according to claim 1 , wherein the camshaft adjuster ( 1 ) comprises a hydraulic vane drive.

3. A camshaft adjuster according to claim 1 , wherein the control valve 3 is a multi-way valve.

4. A camshaft adjuster according to claim 1 , wherein the control piston ( 5 ) is positioned in the control valve ( 3 ) by a force equilibrium between the force (F spring ) of the return spring ( 9 ) and the control force (F control ) of the drive unit ( 8 ).

5. A camshaft adjuster according to claim 1 , wherein the non-self-locking transmission structure ( 16 ) is a rack and pinion drive which converts the rotational movement of the electric motor ( 15 ) into a linear stroke movement ( 17 , 18 ).

6. A camshaft adjuster according to claim 5 , wherein the linear stroke movement ( 17 , 18 ) is transmitted to the control piston ( 5 ) via a point of contact between the transmission structure and the control piston.

7. A camshaft adjuster according to claim 5 , wherein the linear stroke movement is effective in both linear directions.

8. A camshaft adjuster according to claim 1 , wherein the electric motor ( 15 ) and the transmission structure ( 16 ) form a single unit.

9. A camshaft adjuster according to claim 6 , wherein the point of contact between the drive unit ( 8 ) and the control piston ( 5 ) is near the axis of rotation ( 14 ) of the camshaft ( 2 ).

10. A camshaft adjuster according to claim 1 , wherein the transmission structure ( 16 ) includes low wear, low friction bearings.

11. A camshaft adjuster according to claim 1 , wherein the electric motor ( 15 ) and the transmission structure 16 are disposed in a housing ( 21 ) which axially positions and seals the drive unit ( 8 ).

12. A camshaft adjuster according to claim 11 , wherein the housing ( 21 ) is provided at a flange side ( 21 b ) thereof with a projection ( 21 a ) for positioning the drive unit ( 8 ) in a radial direction.

13. A camshaft adjuster according to claim 12 , wherein the projection is one of being conical and cylindrical.

14. A camshaft adjuster according to claim 1 , wherein the drive unit ( 8 ) is integrated into a cover which, at the same time, provides for sealing toward the valve drive housing of the internal combustion engine.

15. A camshaft adjuster according to claim 1 , wherein several drive units ( 8 ) are integrated into a cover which have common electrical connections.

16. A camshaft according to claim 15 , wherein the common connections are connected to additional components.

17. A camshaft according to claim 1 , wherein the control valve ( 3 ) is arranged in one of the camshaft ( 2 ) and the camshaft adjuster ( 1 ).

18. A camshaft according to claim 17 , wherein the control valve ( 3 ) is screwed to the camshaft ( 2 ) and used to mount an inner body ( 7 ) of the camshaft adjuster ( 1 ) to the camshaft ( 2 ).

19. A camshaft according to claim 17 , wherein the control valve ( 3 ) is firmly connected to at least one of the inner body ( 7 ) of the adjuster ( 1 ) and the camshaft ( 2 ).