Stiffening device for a motor vehicle

A stiffening device for a vehicle body of a motor vehicle, the vehicle body having a central tunnel with a U-shaped cross section and with sidewalls, wherein the central tunnel is connected by way of bent portions on the sidewalls to a floor panel of the vehicle body and wherein transverse seat carriers are disposed on both sides of the central tunnel and connected to the floor panel and to the central tunnel, the stiffening device comprising:

• a tunnel bridge disposed at an underside of the vehicle body facing toward the floor panel;
• said tunnel bridge including at least two transverse beams and longitudinal beams connected to said transverse beams;
• said transverse beams extending underneath the bent portions of the central tunnel in a vehicle transverse direction and having free ends to be fastened in each case to the vehicle body by connectors disposed in bores;
• and
• said transverse beams of said tunnel bridge including a rearward transverse beam, relative to a direction of travel, and said rearward transverse beam having, on an upper side, impact elements disposed as an extension of said longitudinal beams and lying in each case with a vertical support wall against an inside of the sidewalls of the central tunnel.