Camshaft phaser

A camshaft phaser for use with an internal combustion engine for controllably varying the phase relationship between a crankshaft and a camshaft in said internal combustion engine, said camshaft phaser comprising:

• a stator having a plurality of lobes and connectable to said crankshaft of said internal combustion engine to provide a fixed ratio of rotation between said stator and said crankshaft;
• a rotor coaxially disposed within said stator, said rotor having a plurality of vanes interspersed with said lobes defining a plurality of alternating advance chambers and retard chambers, wherein said advance chambers receive pressurized oil from a phasing oil control valve in order to change the phase relationship between said crankshaft and said camshaft in an advance direction and said retard chambers receive pressurized oil from said phasing oil control valve in order to change the phase relationship between said camshaft and said crankshaft in a retard direction, said rotor being rotatable within said stator from a full retard position to a full advance position and being attachable to said camshaft of said internal combustion engine to prevent relative rotation between said rotor and said camshaft;
• a lock pin disposed within one of said rotor and said stator for selective engagement with a lock pin seat for preventing a change in phase relationship between said rotor and said stator at a predetermined aligned position between said full advance position and said full retard position when said lock pin is engaged with said lock pin seat;
• a first diverter valve that is switchable between two positions of 1) blocking communication between said phasing oil control valve and only one of said advance chambers while permitting communication between said one of said advance chambers and a first check valve and of 2) permitting communication between said phasing oil control valve and said one of said advance chambers while blocking communication between said one of said advance chambers and said first check valve;
• and
• a second diverter valve that is switchable between two positions of 1) blocking communication between said phasing oil control valve and only one of said retard chambers while permitting communication between said one of said retard chambers and a second check valve and of 2) permitting communication between said phasing oil control valve and said one of said retard chambers while blocking communication between said one of said retard chambers and said second check valve;
• wherein said first check valve allows oil to flow from said one of said retard chambers to said one of said advance chambers for at least some positions of said rotor relative to said stator when said first diverter valve permits communication between said one of said advance chambers and said first check valve;
• and
• wherein said second check valve allows oil to flow from said one of said advance chambers to said one of said retard chambers for at least some positions of said rotor relative to said stator when said second diverter valve permits communication between said one of said retard chambers and said second check valve.