Abstract

A phaser for an internal combustion engine having at least one camshaft. The phaser has a housing and a rotor. The housing has an outer circumference for accepting a drive force and the rotor connects to a camshaft coaxially located within the housing. The housing and the rotor define at least one vane separating chambers, advance and retard. The vane shifts the relative angular position of the housing and the rotor. The phaser also includes a spool valve comprising a spool slidably mounted within in a bore in the rotor. The spool routes operating fluid from a supply of pressurized fluid to the chambers. At least one passage from the supply to the chambers provides makeup fluid. The passage includes a check valve and a restrictor.