A VVA apparatus includes drive-input and intake-side transmission sprockets provided
to an intake-side phase alteration device, an exhaust-side transmission sprocket
provided to the exhaust-side phase alteration device, a reduced-diameter portion
provided to a housing of the exhaust-side phase alteration device between a housing
main body and the exhaust-side transmission sprocket, and a torsion coil spring
arranged between the housing and vane rotor of the exhaust-side phase alteration
device to bias the two in the advance direction. The torsion coil spring is disposed
on the outer periphery of the reduced-diameter portion to have a reduced diameter
when the phase is changed from the phase at engine start.
