Hydraulic valve tappet

Claim 1

A self-adjusting hydraulic valve tappet arranged in a guide bore of a cylinder head of an internal combustion engine and contacted at one end face by a control cam and abutting with a second end face against the end of a valve stem, the tappet consisting of a cup-shaped housing (1) comprising a hollow cylindrical wall (2) closed at one end by an end member (3) against the outside of which the cam abuts, and a cylindrical guide sleeve (6,28) concentric with the cylindrical wall (2), said guide sleeve emanating from the end member (3) extends to the center of an annular flange element (5,29), which at its outer circumference merges into the cylindrical wall (2) of the housing (1) to define an annular oil reservoir (14) between the cylindrical wall (2) and the cylindrical guide sleeve (6,28), the oil reservoir being supplied with oil through a bore (15) leading to the outside of the housing, a self-adjusting hydraulic play compensating element (13) guided in the guide sleeve for slidable longitudinal movement and comprising an inner piston (17) and an outer piston (16) surrounding said inner piston, both pistons being guided for slidable longitudinal movement within each other to define an oil pressure chamber (23), which through a bore (21) closed by a check valve (22) in the inner piston (17) is connected to a centric oil reservoir (18) arranged in the inner piston (17), and defined, on the one hand, by the wall of the inner piston (17) and, on the other hand, by the inner surface (10) of the end member (3), against which the inner piston (17) abuts with its end face, the outer piston (16) being guided for slidable longitudinal movement in the cylindrical guide sleeve (6,28) with its closed end abutting against the end of the valve stem, characterized in that the guide sleeve has at a point distant from the end member (3) an intake port (26,31,53) that opens into a duct extending to the end member (3), which is defined, on the one hand, by the outer surface of the outer piston (16) and, on the other hand, by the bore of the guide sleeve (6), and an oil transfer port (19,34) leading into the centric oil reservoir (18) is provided at the end of the inner piston (17) facing the end member (3).