US Patent 7536986 Camshaft

The present invention relates to a camshaft (1) having an inner shaft (3) arranged coaxially in an outer shaft (2) and mounted to rotate with respect to the outer shaft (2). The camshaft (1) has a first phase adjuster (7) and a second phase adjuster (8), the first phase adjuster (7) adjusting a phase relation of the inner shaft (3) and thus of the first cams in relation to a drive, in particular a crankshaft, while the second phase adjuster (8) adjusts a phase relation of the outer shaft (2) in relation to the drive. Thus the first and second phase adjusters (7, 8) each have a switchable hydraulic valve (9, 10), both being arranged inside the inner shaft (3).