Pressure fluid supply system for a variable camshaft adjustment

Apparatus for adjusting a rotational relation between a camshaft and a timing pulley of an internal combustion engine of a type having a crankshaft for driving the timing pulley and a cylinder head for rotatably supporting the camshaft, said apparatus comprising:

• a housing;
• a double-acting piston reciprocating within the housing between a starting position and a working position and defining two pressure compartments which are fluidly sealed from one another;
• a control bushing secured to the piston and geared to the timing pulley via a first gearing and operatively connected to the camshaft via a second gearing;
• and
• hydraulic regulating means including a guide bush arranged within the housing and fluidly connected to the pressure compartments via fluid-carrying passageway means for alternately supplying a pressure fluid to the pressure compartments to effect an axial displacement of the piston and thereby a positional adjustment of the control bushing, said fluid-carrying passageway means including first and second axially spaced ring channels or distribution spaces which are fluidly connected to each other by a first transfer zone, and a third distribution space connected to one of the first and second ring channels by a second transfer zone, with the first and second transfer zones arranged in angularly offset disposition so that the piston is held in the starting position during starting phase of the internal combustion engine, said first and second ring channels and said first and second transfer zones being formed in the guide bush.