Abstract: A variable camshaft phaser (VCP) has lash take up drive piston assemblies with inner and outer helical splines for phase changing and return springs mounted in pockets in the pistons to shorten overall length for a compact unit and also relieve lash take-up friction on the piston return strokes. Numerous other features are included. A three-way feed-discharge valve limits oil flow to that necessary to operate the drive pistons for phasing.

Abstract: A phase adjuster for engine camshafts and the like includes in a preferred embodiment a sprocket driving a camshaft attached hub through paired wedge packs that transfer torque and maintain a lash free connection. A plunger actuated by engine oil pressure and coating drive springs axially move alternate active wedges to oppositely vary the arcuate lengths of the wedge packs and thereby change the phase angle between the sprocket and camshaft. A three way valve shuts off pressure oil flow except when needed to advance the plunger, thus minimizing oil flow requirements.