CN-122003361-A - Crank assembly for a bicycle

Abstract

A crank assembly for a bicycle includes a crank axle, a crank arm mounted to the crank axle to drive the crank axle to rotate, a carrier shaft slidably mounted to the crank axle and slidable relative to the crank axle, and a sprocket mounted to the carrier shaft. The position sensor is used to determine the relative position of the diametric axis of the sprocket with respect to the central longitudinal axis of the crank arm at the end of the power stroke. Further, the actuator is connected to the carrier shaft to operate the carrier shaft to slide the carrier shaft, and the controller is configured to drive the actuator based on an input of the position sensor to slide the carrier shaft relative to the crankshaft to change a start time of a power stroke of the sprocket.

Inventors

• Lance A. Hertz

Assignees

• 兰斯·A·赫兹

Dates

Publication Date

20260508

Application Date

20240325

Priority Date

20230511

Claims (20)

1. 1. A crank assembly for a bicycle, the crank assembly comprising: A crankshaft having a central axis and configured to rotate about the central axis; A pair of crank arms mounted on and at opposite ends of the crank axle, the pair of crank arms configured to facilitate rotation of the crank axle; A carrier shaft slidably mounted on the crankshaft and configured to slide in a direction substantially parallel to a central axis of the crankshaft and relative to the crankshaft; A sprocket mounted on the carrier shaft, the sprocket rotating in response to rotation of the crank shaft to thereby drive movement of the bicycle; a position sensor for determining the relative position of the diametric axis of the sprocket with respect to the central longitudinal axis of at least one of the pair of crank arms at the end of the power stroke of the sprocket; an actuator coupled to the carrier shaft for operating the carrier shaft and configured to slide the carrier shaft relative to the crankshaft, and A controller is communicatively coupled to the position sensor and the actuator and configured to drive the actuator based on an input from the position sensor to slide the carrier shaft relative to the crankshaft to vary a start time of the power stroke of the sprocket.
2. 2. The crank assembly of claim 1, wherein the crank axle includes a helical groove defined along an outer surface of the crank axle and the carrier shaft includes a key extending within the groove, wherein the carrier shaft rotates about a central axis of the crank axle in response to sliding of the carrier shaft relative to the crank axle to vary a start time of the power stroke of the sprocket.
3. 3. The crank assembly of claim 1 wherein the actuator comprises: The motor is arranged on the side of the motor, A screw adapted to be rotated by the motor, an And a lever connected to the screw to operate the screw and engaged with the bearing shaft, wherein the lever moves along a central axis of the crank shaft in response to rotation of the screw to cause the bearing shaft to slide with respect to the crank shaft.
4. 4. The crank assembly of claim 1, further comprising a bracket adapted to mount the crank assembly to a frame of a bicycle, wherein the crank axle is rotatably connected to the bracket.
5. 5. The crank assembly of claim 1, wherein the sprocket is an elliptical sprocket and a diametric axis of the sprocket is a major axis of the elliptical sprocket.
6. 6. The crank assembly of claim 1, wherein the angular orientation of the diametric axis of the sprocket relative to the central longitudinal axis of at least one crank arm changes in response to sliding movement of the carrier shaft relative to the crank axle.
7. 7. The crank assembly of claim 1, further comprising a tilt sensor for determining a tilt of a bicycle running surface, and the controller is configured to drive the actuator based on an input of the tilt sensor.
8. 8. A bicycle, comprising: A frame; front and rear wheels supported on the frame; A crankshaft having a central axis and configured to rotate about the central axis; a pair of crank arms mounted on and at opposite ends of the crank axle, the pair of crank arms configured to facilitate rotation of the crank axle; a carrier shaft slidably mounted on the crankshaft and configured to slide in a direction substantially parallel to a central axis of the crankshaft and relative to the crankshaft; A sprocket mounted on the carrier shaft, wherein the sprocket rotates in response to rotation of the crank shaft, thereby driving a bicycle to move; a tilt sensor for measuring a tilt of a bicycle running terrain; A position sensor for determining the relative position of the diametric axis of the sprocket with respect to the central longitudinal axis of at least one of the pair of crank arms at the end of the power stroke of the sprocket; An actuator coupled to the carrier shaft for operating the carrier shaft and configured to slide the carrier shaft relative to the crankshaft, and And a controller communicatively coupled to the tilt sensor, the position sensor, and the actuator and configured to drive the actuator to slide the carrier shaft relative to the crankshaft based on inputs from the tilt sensor and the position sensor, thereby changing a start time of the power stroke of the sprocket.
9. 9. The bicycle of claim 8, wherein the crank axle includes a helical groove defined along an outer surface of the crank axle and the carrier axle includes a key extending within the groove, wherein the carrier axle rotates about a central axis of the crank axle in response to sliding of the carrier axle relative to the crank axle to vary a start time of the power stroke of the sprocket.
10. 10. The bicycle of claim 8, wherein the actuator comprises: The motor is arranged on the side of the motor, A screw adapted to be rotated by the motor, an And a lever connected to the screw to operate the screw and engaged with the bearing shaft, wherein the lever moves along a central axis of the crank shaft in response to rotation of the screw to cause the bearing shaft to slide with respect to the crank shaft.
11. 11. The bicycle of claim 8, further comprising a bracket adapted to mount the crank assembly to a frame of the bicycle, wherein the crank axle is rotatably coupled to the bracket.
12. 12. The bicycle of claim 8, wherein the sprocket is an elliptical sprocket and a diametric axis of the sprocket is a major axis of the elliptical sprocket.
13. 13. The bicycle of claim 8, wherein the angular orientation of the diametric axis of the sprocket relative to the central longitudinal axis of at least one crank arm changes in response to sliding of the carrier shaft relative to the crank axle.
14. 14. A crank assembly for a bicycle, the crank assembly comprising: A bracket adapted to connect to a frame of a bicycle such that the crank assembly is mounted to the frame; A crankshaft rotatably mounted on the bracket, having a central axis, and configured to rotate about the central axis; A pair of crank arms mounted on and at opposite ends of the crank axle, the pair of crank arms configured to facilitate rotation of the crank axle; A carrier shaft slidably mounted on the crankshaft and configured to slide in a direction substantially parallel to a central axis of the crankshaft and relative to the crankshaft; A sprocket mounted on the carrier shaft, the sprocket rotating in response to rotation of the crank shaft to thereby drive movement of the bicycle; a tilt sensor for measuring a tilt of a bicycle running terrain; A position sensor for determining the relative position of the diametric axis of the sprocket with respect to the central longitudinal axis of at least one of the pair of crank arms at the end of the power stroke of the sprocket; An actuator coupled to the carrier shaft for operating the carrier shaft and configured to slide the carrier shaft relative to the crankshaft, and And a controller communicatively connected to the tilt sensor, the position sensor, and the actuator and configured to drive the actuator to slide the carrier shaft relative to the crankshaft in response to inputs from the tilt sensor and the position sensor, thereby changing a start time of the power stroke of the sprocket.
15. 15. The crank assembly of claim 14, wherein the crank axle includes a helical groove defined along an outer surface of the crank axle and the carrier shaft includes a key extending within the groove, wherein the carrier shaft rotates about a central axis of the crank axle in response to sliding of the carrier shaft relative to the crank axle to vary a start time of the power stroke of the sprocket.
16. 16. The crank assembly of claim 14 wherein the actuator comprises: The motor is arranged on the side of the motor, A screw adapted to be rotated by the motor, an And a lever connected to the screw to operate the screw and engaged with the bearing shaft, wherein the lever moves along a central axis of the crank shaft in response to rotation of the screw to cause the bearing shaft to slide with respect to the crank shaft.
17. 17. The crank assembly of claim 14, wherein the sprocket is an elliptical sprocket and a diametric axis of the sprocket is a major axis of the elliptical sprocket.
18. 18. The crank assembly of claim 14, wherein the angular orientation of the diametric axis of the sprocket relative to the central longitudinal axis of at least one crank arm changes in response to sliding movement of the carrier shaft relative to the crank axle.
19. 19. The crank assembly of claim 15, wherein the sprocket is an elliptical sprocket and a diametric axis of the sprocket is a major axis of the elliptical sprocket.
20. 20. The crank assembly of claim 15, wherein the angular orientation of the diametric axis of the sprocket relative to the central longitudinal axis of at least one crank arm changes in response to sliding movement of the carrier shaft relative to the crank axle.

Description

Crank assembly for a bicycle This patent application is a continuation of and claims priority from U.S. patent application Ser. No. 17/857,005, filed on 7.2022, and U.S. patent 11878766, filed on 11.2023, and granted on 23.1.2024. Technical Field The present invention relates generally to a crank assembly for a bicycle, and more particularly to a bicycle crank assembly that is capable of varying the start time of a power stroke of the bicycle. Background Conventional bicycles include a generally tubular frame having front and rear wheels that are steerable by handlebars. The rear wheel is driven by a chain which is wound around a sprocket driven by a pedal mounted to the crank. The sprocket is typically circular with a pedal stroke beginning when the crank is in a vertically upward position, which makes it difficult to provide optimal power transmission to the bicycle. To solve this problem, oval or elliptical sprockets are increasingly used. However, oval or elliptical sprockets also suffer from the problem of not having an optimal power stroke when the bicycle is traveling on an inclined terrain. There is a need for a transmission that continuously maintains the optimal power stroke of the bicycle during travel over sloped terrain. Disclosure of Invention According to one embodiment, a crank assembly for a bicycle is provided. The crank assembly includes a crank axle having a central axis and configured to rotate about the central axis, and a pair of crank arms mounted on the crank axle and disposed at opposite ends of the crank axle. The pair of crank arms are configured to facilitate rotation of the crank axle. The crank assembly further includes a carrier shaft slidably mounted on the crank axle and configured to slide relative to the crank axle in a direction substantially parallel to the crank axle central axis. In addition, the crank assembly includes a sprocket mounted on the carrier shaft. The sprocket rotates in response to rotation of the crank axle to move the bicycle. Further, the crank assembly includes a position sensor for determining a relative position of the sprocket diameter axis with respect to a central longitudinal axis of at least one of the pair of crank arms at an end of a sprocket power stroke, and an actuator coupled to the carrier shaft to operate the carrier shaft and configured to drive the carrier shaft to slide with respect to the crank axle. The crank assembly further includes a controller communicatively coupled to the position sensor and the actuator and configured to drive the actuator based on an input from the position sensor to slide the carrier shaft relative to the crankshaft to vary a start time of a power stroke of the sprocket. In this way, when the crank assembly is driven on a bicycle uphill or downhill, the sprocket is rotated relative to the crankshaft by rotating the carrier shaft, and the start time of the power stroke is advanced or retarded, so that the rider starts the power stroke perpendicular to the direction (force) of the earth's gravity. Therefore, the mechanism provides mechanical advantage to the rider, reduces the fatigue of the rider, thereby making the rider apply more stable force, and keeps the pedaling frequency unaffected by the change of the direction of earth gravity when driving on an uphill or downhill. Furthermore, the above mechanism allows the use of asymmetric oval bicycle sprockets on the bicycle without affecting the bicycle rider's specific cadence of pedaling frequencies. In some embodiments, the crank axle includes a helical groove defined along an outer surface of the crank axle and the carrier axle includes a key extending within the groove, wherein the carrier axle rotates about a central axis of the crank axle in response to sliding movement of the carrier axle relative to the crank axle to vary a start time of a power stroke of the sprocket. In some embodiments, the actuator includes a motor, a screw adapted to be rotated by the motor, and a lever coupled to the screw to operate the screw and engage the carrier shaft. The lever moves along the central axis of the crankshaft in response to rotation of the screw to cause the carrier shaft to slide relative to the crankshaft. In some embodiments, the crank assembly further comprises a bracket for mounting the crank assembly to a bicycle frame. The crank axle is rotatably connected with the bracket. In some embodiments, the sprocket is an elliptical sprocket and the diametric axis of the sprocket is the major axis of the elliptical sprocket. In some embodiments, the angular orientation of the diametric axis of the sprocket relative to the central longitudinal axis of the at least one crank arm changes in response to sliding of the carrier shaft relative to the crank axle. In some embodiments, the crank assembly further comprises a controller configured to drive the actuator based on the input of the inclination sensor. According to one embodiment, a bicycle is disclosed. A b