Patent ID: 6089198
Filing Date: 2000-07-18
Classification: F01L,F16D,Y10T

Abstract:
A device for varying opening and closing times of gas exchange valves of an internal combustion engine, comprising a drive unit (2) which is in driving relationship with a crankshaft through a traction element and a driven unit (14) rotationally fixed to an intake or exhaust camshaft, said drive unit (2) being comprised of a drive pinion (3) and a housing (6) fixed thereon, an adjusting piston (9) which is axially displaceable by a hydraulic pressure medium between two end positions being sealingly guided on an inner wall (7) of said housing (6) while axially delimiting two pressure chambers (16, 17) which can be connected alternately or simultaneously to a pressure medium feed duct and a pressure medium drain duct, said adjusting piston (9) being made in one piece with a hollow cylindrical sliding sleeve (10) comprising, on an inner peripheral surface (11), a first helical gear section (12) and, axially spaced therefrom, an oppositely oriented, second helical gear section (13), the first gear section (12) cooperating with a complementary outer gearing (5) of a gear hub (4) which is rotationally fixed on the drive pinion (3), and the second helical gear section (13) cooperating with a complementary outer gearing (15) on the driven unit (14), characterized in that at least one coupling element (18) is arranged within the device (1) and, when a pressure of the hydraulic medium falls below a level required for a displacement of the adjusting piston (9), said coupling element (18) with the help of an auxiliary energy can establish a rotationally fixed, force-transmitting connection independently of the adjusting piston (9) between the drive unit (2) and the driven unit (14) in one or more relative angular positions of said drive and driven units and can further prevent a displacement of the adjusting piston (9) in an undesired direction of adjustment.