Transmission mechanism

A transmission mechanism comprising a main shaft, first and second disk sets mounted on the main shaft in a spaced apart and facing manner each having first and second disks mounted on the main shaft in close proximity perpendicular to the main shaft, a plurality of first and second radial slits formed in the first and second disks respectively, and a plurality of transmission wheels formed by a plurality of sprockets or pinions supported at intersections of the first and second radial slits in the first and second disk sets and a plurality of guide rods, and a composite transmission wheel for engaging with a driving force transmission chain or toothed belt is configured with the plurality of transmission wheels and the plurality of the guide rods;

• wherein
• each of transmission wheels is provided with at least one clutch mechanism capable of switching the transmission wheel between a rotation prohibited state and a rotation permitted state,
• through the clutch mechanism, each transmission wheel is put in the rotation permitted state during speed change operation, and is put in the rotation prohibited state during other than speed change operation.