Valve timing adjuster for internal combustion engine

This application is based on and incorporates herein by reference Japanese Patent Application No. Hei. 11-355643 filed on Dec. 15, 1999. A torsion coil spring is installed in a circle groove of a chain sprocket. Both ends of the coil spring are bent in a radially outward direction. The first bent end is fit to a fixed pin protruding from the chain sprocket, and the second bent end is fit to a pin protruding from a vane rotor. The coil spring urges the vane rotor such that the vane rotor advances with respect to the chain sprocket. That is, the coil spring urges the vane rotor such that a camshaft advances with respect to an engine crankshaft.