Abstract

An internal DPCS feeds (13) engine oil pressure (32) to one side (19) of the spool and a solenoid controlled pressure (14) to a piston (12) that has twice the area as that side (19) of the spool. The spool end (21) that is fed control pressure is preferably twice the area of the spool end (19) that is fed with engine oil pressure. A spring (18) mounted in the phaser pushes the spool (25) to the default position in case of solenoid failure. A PWM solenoid valve (15) or a proportional solenoid valve controls the oil flow to the large area end (21) of the spool (25). In a preferred embodiment of the invention, a position sensor (34) further controls the position of the spool valve (28).