Multistage transmission

A multistage transmission comprising:

• an input shaft connected to a prime mover, and supported by a transmission-case member;
• an output shaft arranged parallel to the input shaft and supported by the transmission-case member;
• an input disk which is installed on the input shaft and whose outer peripheral edge is arranged in close proximity to the output shaft;
• an output disk which is installed on the output shaft and whose outer peripheral edge is arranged in close proximity to the input shaft;
• a pair of pressure-application devices configured to be movable along a two-axes connecting line, interconnecting an axis of the input shaft and an axis of the output shaft, within a disk overlapping area that the input and output disks overlap with each other, and further configured to sandwich both outside faces of the input and output disks while applying contact pressure from the outside disk faces at a position corresponding to a required transmission ratio, for creating a torque-transmission contacting portion by elastic deformation of the input and output disks;
• the input disk having a plurality of input-side concentric ridged portions formed on its disk face and arranged concentrically with the axis of the input shaft as concentric circles with the same center, which center is identical to the axis of the input shaft, and respective different radii from the axis of the input shaft;
• the output disk having a plurality of output-side concentric ridged portions formed on its disk face and arranged concentrically with the axis of the output shaft as concentric circles with the same center, which center is identical to the axis of the output shaft, and respective different radii from the axis of the output shaft;
• and
• the plurality of input-side concentric ridged portions and the plurality of output-side concentric ridged portions being configured such that the entire length of the two-axes connecting line is divided into an input-side driving radius and an output-side driving radius, both determined based on the required transmission ratio of a plurality of transmission ratios, and that an apex of a selected one of the input-side concentric ridged portions, determined based on the required transmission ratio, and an apex of a selected one of the output-side concentric ridged portions, determined based on the required transmission ratio, are arranged to oppose each other on the two-axes connecting line.