The camshaft phasing unit is designed as a hydraulic torque motor based on the vane principle. With the normal adjustment angles of 60° crank angle – corresponding to 30° rotation angle of the phasing unit – 5 double direction chambers can be achieved that support the load of the camshaft torques. The spring-loaded vanes ensure good seal integrity of the pressure chambers in relation to each other.
In the base position – typically "retarded" timing for intake phasing and "advanced" timing for exhaust phasing – a spring-loaded pin locks the phasing unit when the engine is turned off and this is hydraulically unlocked in operation.
When used as an exhaust camshaft phasing unit with the final position in the "advanced" timing, a spring is mounted on the phasing unit that supports the locked final position.