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1. A variable cam timing mechanism for an internal combustion engine, the mechanism having a housing assembly with an outer circumference for accepting drive force and a rotor assembly for connection to a camshaft, having a plurality of vanes coaxially located within the housing, wherein the housing assembly and the rotor assembly define at least one chamber separated by a vane into an advance chamber with an advance wall and a retard chamber with a retard wall opposite the advance wall, the motion of the vane within the chamber acting to shift a relative angular position of the housing assembly and the rotor assembly by fluid by a control valve, the mechanism comprising:
a first lock pin and a second lock pin, each lock pin being slidably located in one of the rotor assembly or the housing assembly, the lock pins being movable from an unlocked position in which the end portion does not engage a recess in the other of the rotor assembly or the housing assembly, to a locked position in which an end portion engages the recess, locking the relative angular position of the housing assembly and the rotor assembly at a locked position; the first pin being biased by a spring toward the locked position, and the second lock pin being biased by a spring toward the unlocked position; the locked position of the first lock pin being in an intermediate position between the advance wall and the retard wall; the locked position of the second lock pin being at an end position when the vane is in a retard end stop position; a piloted valve movable between a first position to a second position, the piloted valve being biased by a spring into the second position and movable into the first position by fluid pressure; the control valve being movable into:
an advance mode in which fluid is routed to the advance chamber, the piloted valve and the first lock pin, moving the piloted valve to the first position and the first lock pin to the unlocked position, and fluid is not routed to the second lock pin, such that the second lock pin is moved to the unlocked position by the spring;a retard mode in which fluid is routed to the retard chamber, the piloted valve, the first lock pin, and the second lock pin moving the piloted valve to the first position and the first lock pin to the unlocked position, and pressurizing the second lock pin to move toward a locked position;an end stop lock mode in which fluid is routed to the retard chamber, the piloted valve, the first lock pin and the second lock pin, moving the piloted valve to the first position and the first lock pin to the unlocked position, and the second lock pin to the locked position; anda detent mode in which the rotor assembly is moved to and held in an intermediate phase angle position relative to the housing assembly through a plurality of detent lines communicating with the advance chamber or the retard chamber which are restricted or blocked when the rotor assembly is in or near an intermediate phase angle position, and in which fluid from the control valve is supplied to the piloted valve causing the piloted valve to move to the second position, and in which fluid is not supplied to either the first lock pin or the second lock pin, such that the first lock pin moves to the locked position and the second lock pin moves to the unlocked position. |
