Patent ID: 6920855

Claim:
A valve timing adjustment device for controlling and adjusting a timing of at least one of an intake valve and an exhaust valve provided in a transmission system for transmitting drive torque from a drive shaft to a driven shaft, the device comprising: a driving rotary body rotating in synchronization with the drive shaft; a movable body; a guide rotary body including a guide passage having a variable dimension extending radially from a rotational centerline adapted to rotate relative to the driving rotary body to guide the movable body in a length direction of the guide passage; and a phase change means for setting a rotational phase of the driven shaft relative to the drive shaft to one of a delay side and an advance side when the movable body moves away from the rotational centerline and setting the rotational phase of the driven shaft to the other of the delay side and the advance side when the movable body moves closer to the rotational centerline, wherein the guide passage includes a gradually decreasing region and a gradually increasing region that are connected to each other in the length direction, the gradually decreasing region extends on a slant relative to an axis in a radial direction of the guide rotary body and includes a radial dimension relative to the axis that decreases toward an end of the guide passage, and the gradually increasing region extends on a slant relative to the axis in the radial direction of the guide rotary body and includes a radial dimension relative to the axis that increases toward the end of the guide passage.