The invention relates to an apparatus for an internal combustion engine
which for each cylinder with associated piston has at least one inlet
valve and at least one exhaust valve for controlling the connection
between the combustion chamber in the cylinder and an intake system and
an exhaust system respectively. A rotatable camshaft with a cam lobe is
designed to interact with a main rocker arm and a secondary rocker arm,
the two rocker arms serving to transmit the movement of the cam lobe to
the inlet/exhaust valve. The cam lobe is arranged to act on both of the
rocker arms during each revolution of the camshaft. The secondary rocker
arm interacts with a hydraulic piston, which is displaceable in a
hydraulic cylinder and which forms part of a hydraulic circuit having a
hydraulic fluid source, and which permits switching between at least two
different working positions.