Suction unit and autonomous vacuum cleaner

The invention relates to a suction unit and relates to a vacuum cleaner. The suction unit comprises a drive system for driving the suction unit over a surface to be treated; a chassis supporting the drive system; a nozzle for removing particles from a surface to be treated which nozzle is configured to move with relation to the chassis in a direction away from the surface to be treated, the nozzle having an interior space defining an opening that faces the surface to be treated; and an outlet communicating with the interior space, the outlet being arranged for communication with a fan unit in operating conditions. The suction unit further comprises coupling means for coupling the nozzle to the chassis, wherein the coupling means is arranged to exert a force that is directed away from the surface to be treated when the under pressure in the interior space increases. In this manner the problem of the suction unit getting stuck on the floor can be overcome or at least be reduced. Furthermore the traction of the