Belt tensioner

A belt tensioner for a generator belt drive of an internal combustion engine, the belt tensioner comprising:

• a tensioning arm with a tensioning roller supported on the arm,
• a tensioning spring applying a load on the tensioning arm adapted for pretensioning a belt,
• a tensioner housing adapted for mounting on the generator,
• the belt tensioner and the tensioner housing each have an open ring-shaped construction for mounting on the generator and, in a mounted state of the belt drive, the belt tensioner and the tensioner housing are each adapted to encompass a pulley of the generator and cover the belt in a plane that is spaced apart from a belt plane and runs on an other side of the belt plane with respect to the generator,
• the open ring-shaped construction, is adapted to allow the belt to be mounted in an assembled state of the belt tensioner on the generator axially through a ring opening of the belt tensioner and a ring opening of the tensioner housing onto the pulley of the generator.