Variable valve mechanism of internal combustion engine

A variable valve mechanism of an internal combustion engine, comprising:

• a rocker arm including an input member driven by a cam and an output member that drives a valve when swung;
• a switching device that includes a first pin hole provided in the input member, a second pin hole provided in the output member, and a switching pin, and that switches a drive state of the valve by displacing the switching pin between a coupling position at which the switching pin extends between the first pin hole and the second pin hole and a non-coupling position at which the switching pin does not extend between the first pin hole and the second pin hole;
• and
• a lost motion spring that urges the input member toward the cam at a non-coupled time when the switching pin is disposed at the non-coupling position, wherein
• a displacement clearance in a direction of relative displacement of the input member with respect to the output member at the non-coupled time is formed between an inner peripheral surface of the first or second pin hole and an outer peripheral surface of the switching pin to permit the relative displacement in a range of the displacement clearance at a coupled time when the switching pin is disposed at the coupling position so that a tappet clearance is not formed between a base circle of the cam and the input member with the input member urged toward the cam by the lost motion spring also at the coupled time.