Abstract: A friction wheel drive for an internal combustion engine's a unit belt drive for a secondary unit includes a control system, a friction wheel that engages frictionally with an outer side of a belt in a wrap-around portion of a drive wheel of the internal combustion engine and that is controlled by the control system to engage or disengage frictionally with a drive wheel of the secondary unit, and a guidance system having an arc section for guiding the movement of the friction wheel with the control system. The arc section is arranged equidistant from the axis of rotation of the drive or driven wheel relative to the driven wheel to the outside of the belt in the wrap-around portion for turning the secondary unit on and off.

Abstract: A belt drive for a secondary unit of an internal combustion engine includes a friction wheel drive having a friction wheel, a cam device for adjusting the engagement of the friction wheel to the drive wheel of the secondary unit, the cam device having a cam, a swivel arm by which the friction wheel is connected to the cam which is rotationally mounted on a side of the engine, and a spring biasing the swivel arm in a tension direction. The friction wheel is in permanent position of frictional engagement with a drive wheel of the secondary unit to drive the secondary unit and with an outside of a belt on a drive wheel of the internal combustion engine or of another secondary unit.