Transmission system for a bicycle, and bicycle incorporating same

A transmission system comprising:

• a chain;
• a sprocket cluster comprising a plurality of transmission sprockets with different outer diameters, the sprocket cluster arranged along a sprocket axis common to each of the plural transmission sprockets;
• an operation cable;
• a changing mechanism detachably linked to the operation cable, the changing mechanism operable to shift the chain in an axial direction of the sprocket cluster such that the chain moves from one transmission sprocket to another among the sprocket cluster in response to selected movement of the operation cable,
• the changing mechanism comprising a linking part which permits detachable linking of the operation cable to the changing mechanism;
• and
• a transmission case for housing the sprocket cluster, the changing mechanism and the chain, the transmission case comprising an axially-directed case wall having a work opening formed therein, and a radially-directed case wall having an operation opening formed therein through which an end portion of the operation cable extends;
• wherein the operation cable and the linking part of the changing mechanism may be accessed via the work opening in the axially-directed case wall of the transmission case component to permit connection or disconnection of the operation cable, and wherein the chain may be lubricated via the work opening, wherein the work opening is situated adjacent to a transmission sprocket having the largest outer diameter among the sprocket cluster,
• the work opening positioned so as to lie above and outside the outer periphery of the transmission sprocket having the largest outer diameter among the sprocket cluster, and wherein, among the sprocket cluster, the transmission sprocket having the largest outer diameter is located closest to the work opening in a direction radial to the sprocket axis.

A transmission system, comprising:

• a transmission case having a work opening formed therein;
• a chain disposed in the transmission case;
• a sprocket cluster disposed in the transmission case and comprising a plurality of transmission sprockets having different outer diameters, the sprockets of the sprocket cluster being arranged along a common sprocket axis;
• a changing mechanism disposed in the transmission case, and an operation cable for use in operating the changing mechanism, the changing mechanism being operable to move the chain in an axial direction of the sprocket cluster such that the chain moves from one transmission sprocket to another among the sprocket cluster in response to movement of the operation cable, the operation cable being detachably linked to the changing mechanism;
• and
• a cap which is detachably secured over the work opening to plug and protectively cover the work opening, the cap configured and arranged to be removable from the transmission case without requiring removal of any other component;
• wherein the transmission case comprises an axially-directed case wall in which the work opening is formed, and a radially-directed case wall having an operation opening formed therein through which an end portion of the operation cable extends;
• wherein the operation cable and the linking part of the changing mechanism may be accessed via the work opening in the axially-directed case wall of the transmission case component to permit connection or disconnection of the operation cable, and wherein the chain may be lubricated via the work opening;
• and
• wherein a transmission sprocket having the largest outer diameter among the sprocket cluster is located closest in the sprocket axis direction to the work opening.