Bicycle transmission
View Patent ↗A bicycle transmission assembly that is mountable to a bottom bracket shell of a bicycle frame. The bicycle transmission assembly includes an input crank assembly, an output chainring, a planetary gear mechanism, a control system and a mounting system. The input crank assembly is mounted to a rotatable crank axle mounted to the bottom bracket shell. The planetary gear mechanism is mounted to the bottom bracket shell and provides a plurality of transmission paths. The planetary gear mechanism includes a sun gear, a ring gear and a locking element operatively connecting the sun gear and the ring gear. The control system is operatively connected to the planetary gear mechanism for selecting one of the transmission paths.
1. A bicycle transmission assembly mountable to a bottom bracket shell of a bicycle frame, the bicycle transmission assembly comprising:
an input crank assembly mounted to a rotatable crank axle mounted to the bottom bracket shell;
an output chainring for engaging a bicycle drive chain;
a planetary gear mechanism mounted to the bottom bracket shell and providing a plurality of transmission paths, the planetary gear mechanism including a plurality of planet gears operatively connected to the input crank assembly, a sun gear, a ring gear and a locking element operatively connecting the sun gear and the ring gear; and
a control system operatively connected to the planetary gear mechanism for selecting one of the plurality of transmission paths,
wherein rotation of the input crank assembly drives the planet gears to overdrive the ring gear in a first transmission path of the plurality of transmission paths.
2. The bicycle transmission assembly of claim 1 , wherein the output chainring is nonrotatably connected to the ring gear.
3. The bicycle transmission assembly of claim 2 , wherein the control system includes:
a sun pawl;
a collar configured to support the sun pawl, the sun pawl configured to be selectively positionable between an engaged position nonrotatably connecting the sun gear to the collar and a disengaged position allowing the sun gear to rotate relative to the collar; and
a shift actuator for selectively positioning the sun pawl between the engaged and disengaged positions.
4. The bicycle transmission assembly of claim 3 , wherein when the sun pawl is in the engaged position, rotation of the input crank assembly drives the planet gears to overdrive the ring gear in the first transmission path.
5. The bicycle transmission assembly of claim 4 , wherein when the sun pawl is in the disengaged position, rotation of the input crank assembly drives the planet gears to rotate the sun gear until the locking element engages the ring gear, locking the sun gear to the ring gear in a second transmission path.
6. The bicycle transmission assembly of claim 5 , wherein the locking element is a pawl.
7. A bicycle transmission assembly mountable to a bottom bracket shell of a bicycle frame, the bicycle transmission assembly comprising:
input crank means mounted to a rotatable crank axle mounted to the bottom bracket shell;
an output chainring for engaging a chain;
planetary gear means mounted to the bottom bracket shell and providing a plurality of transmission paths, the planetary gear means including a plurality of planet gears operatively connected to the input crank assembly, a sun gear, a ring gear and locking means operatively connecting the sun gear and the ring gear; and
control means operatively connected to the planetary gear means for selecting one of the plurality of transmission paths,
wherein rotation of the input crank means drives the planet gears to overdrive the ring gear in a first transmission path of the plurality of transmission paths.
8. The bicycle transmission assembly of claim 7 , wherein the output chainring is nonrotatably connected to the ring gear.
9. The bicycle transmission assembly of claim 8 , wherein the control means includes:
a sun pawl;
collar means configured to support the sun pawl, the sun pawl configured to be selectively positionable between an engaged position nonrotatably connecting the sun gear to the collar means and a disengaged position allowing the sun gear to rotate relative to the collar means; and
a shift actuator means for selectively positioning the sun pawl between the engaged and disengaged positions.
10. The bicycle transmission assembly of claim 9 , wherein when the sun pawl is in the engaged position, rotation of the input crank means drives the planet gear to overdrive the ring gear in the first transmission path.
11. The bicycle transmission assembly of claim 10 , wherein when the sun pawl is in the disengaged position, rotation of the input crank means drives the planet gears to rotate the sun gear until the locking means engages the ring gear, locking the sun gear to the ring gear in a second transmission path.
12. The bicycle transmission assembly of claim 11 , wherein the locking means is a pawl.