Patent ID: 7246581

Claim:
A variable valve timing control apparatus of an internal combustion engine comprising: a rotary member adapted to be driven by an engine crankshaft; a camshaft rotatable relative to the rotary member and adapted to have a series of cams for operating engine valves; a phase converter comprising: (a) a rotary phase-converter housing integrally connected to one of the rotary member and the camshaft, and having a lock-piston hole formed in the housing; and (b) a five-blade vane member having five blades radially extending from an outer periphery thereof and rotatably disposed in the housing and integrally connected to the other of the rotary member and the camshaft, the five blades of the vane member and the housing cooperating with each other to define five variable-volume phase-retard chambers and five variable-volume phase-advance chambers; a hydraulic circuit provided to supply hydraulic pressure selectively to either one of each of the phase-retard chambers and each of the phase-advance chambers to change a phase angle of the vane member relative to the housing; a lock piston slidably supported in a bore formed in a first one of the five blades, and being engaged with the lock-piston hole in a specified phase angle of the vane member relative to the housing and disengaged from the lock-piston hole in a phase-angle range of the vane member except the specified phase angle; and an area of an outside circumference of each of a first pair of blades, located on both sides of the first blade having the bore slidably supporting the lock piston, being dimensioned to be less than an area of an outside circumference of each of a second pair of blades, circumferentially spaced apart from the first blade rather than the first pair.