CAMSHAFT PHASER

A camshaft phaser has a central-position locking device for locking the rotor in a central locking position relative to the stator. One or more of the vanes altogether have at least two pressure medium conduits each fluidically connect two working chambers of different directions of action. The pressure medium conduits have check valves of different directions of action which allow the pressure medium to be transferred in one direction and prevent it from being transferred in the respective opposite direction, depending on the direction of rotation of the rotor relative to the stator. A valve device is provided in the rotor hub, the at least one switchable valve device in one operating position allowing the working chambers between which transfer of pressure medium is prevented by the check valve or between which no check valve is provided to be fluidically connected to each other.