Gear type power transmission

摘要

A manual power transmission includes a transmission casing (10), input (Si) and output (So) shafts coaxially aligned with each other and a countershaft (So) accommodated within the transmission casing (10) and positioned below the input (Si) and output (So) shafts. The input (Si) and output (So) shaft has a plurality of gears (1G-6G) of a varying size or diameter mounted thereon and associated with gearshifting positions and the countershaft (Sc) has a corresponding number of coutergears (1Gc-6Gc) of a varying size or diameter mounted thereon and paired with the gears (1G-6G) on the input (Si) and output (So) shafts. Some of the countergears (1Gc-6Gc) which serve as an idle gear are so juxtaposed in a direction axially of the countershaft (Sc) that an envelope enclosing all of the those countergears (1Gc-6Gc) while touching respective outer perimeters of those remaining countergears represents a generally barrel shape having a generally intermediate portion thereof bulged radially outwardly with respect to the countershaft (Sc).