US Patent 7401584 Adjustable engine

A switchable cam follower (1) is proposed which serves to transmit a cam stroke in a variable manner from a cam to valve timing mechanism elements of an internal combustion engine. The cam follower (1) comprises substantially a cylindrical inner part (5) and a cylindrical outer part (2) which can be displaced into one another in the direction of their longitudinal axes and can be locked and unlocked in a relative position by means of coupling means (10) which are preferably actuated by pressure-modulated hydraulic medium, and also comprises at least one spring means (7) which is arranged between the inner part (5) and the outer part (2). The inner part (5) has a run-on surface (16) for the cam at one end side (17) and is radially guided in an inner wall (4) of the outer part (2) by way of an outer circumferential surface (6). The outer part (2) has an outer cylindrical circumferential surface (3), by way of which the cam follower (1) is guided in a housing hole of the internal combustion engine in a longitudinally movable manner, and an outer end face (25) facing away from the cam, as a contact face for valve timing mechanism elements which are operatively connected to the cam follower (1). Here, the outer circumferential surface (3) of the outer part (2) is to have substantially identical diameters in the region of the end face (25) which faces the valve timing mechanism element and in the region of an opening (26) which is oriented toward the inner part (5). At the same time, the spring means (7) is to be arranged within the outer part (2).