JPH0472969B

PURPOSE:To surely prevent malfunction from occurring by a method wherein a cam is loosely fitted onto a camshaft in the valve gear system of an internal combustion engine and an oil replenishing passage for ensuring the holding of a plunger, which is engaged with and disengaged from said cam in the camshaft, in the disengaged position is provided in the camshaft. CONSTITUTION:When an output signal is issued from a controller 14 so as to change-over an oil control valve 13 in order to lead pressure oil through an oil pipe 12 to the oil passage 201 in a camshaft 2 during light load running or the like, a plunger 19 in a guide hole 18 formed in the diametral direction of the camshaft 2 is shifted against a spring 21 from a position, at which the plunger 19 engages with the engaging dent 163 of a cam 16, to a position, at which the plunger 19 engages deeply in a guide hole 18. As a result, the camshaft 2 slides in the cam 16 instead of rotating the cam 16 and a suction and an exhaust valves are kept at the fully closed states. In this case, a plurality of oil replenishing passages 23 are fromed radially in the camshaft 2 so as to apply the pressure oil in the oil passage 201 in the camshaft 2 to a ramp groove 24 and the engaging dent 163 in order to ensure the retreat of the plunger 19 into the guide hole 18.