Asymmetric Shift Cam Indexing for AMT Torque Reduction
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Solution Overview
Problem
In Automated Manual Transmissions (AMT) for motorcycles, the existing shift mechanisms require increased torque to quickly rotate the shift cam, especially in bottom-neutral systems, which can lead to instability and inefficiency in gear changes.
Innovation Solution
A shift mechanism with an index cam fixed to the shift cam, a drive section to rotate the index cam, and a cam phase holding portion to hold the shift cam in each phase, where the concave portions on the index cam are arranged to maintain constant intervals, reducing the acute angle between the neutral and maximum speed phases, thus minimizing the torque required for rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the neutral position is set at the end on the lowest gear side in the shift mechanism (bottom-neutral shift pattern), then the gear positions can be arranged sequentially from neutral to top gear, but the acute angle between the neutral phase and maximum speed phase becomes too small, requiring increased torque to rotate the shift cam quickly
Solution Approach 1:
The patent applies asymmetry by making the acute angle between the neutral phase and maximum speed phase larger than the angles between other adjacent gear phases. This asymmetric angular distribution compensates for the bottom-neutral shift pattern configuration, ensuring that the shift cam can be rotated quickly without requiring excessive torque, thereby resolving the contradiction between ease of operation and torque requirement.
2Productivity
If constant feed angles are set for each stage transmission in the shift cam, then the drive and control of the actuator is simplified and shift change time is stabilized, but the acute angle between neutral and maximum speed phases becomes too small in bottom-neutral systems
Solution Approach 1:
The patent resolves this contradiction by introducing asymmetric angular spacing where the acute angle between neutral and maximum speed phases is deliberately made larger than other phase angles. This asymmetric design maintains constant feed angles for stable shift timing while preventing excessive torque requirements during shift cam rotation.
Solution Approach 2:
The patent changes the angular parameter distribution around the shift cam, specifically adjusting the acute angle between neutral and maximum speed phases to be larger than other adjacent phase angles. This parameter modification ensures both stable shift timing and acceptable torque requirements are achieved simultaneously.
3Ease of operation
If the shift cam is configured with equal angular intervals between all gear phases, then the rider can perform shift operations uniformly, but in bottom-neutral systems this creates an excessively small acute angle between neutral and top gear phases
Solution Approach 1:
The patent applies asymmetry by deviating from equal angular intervals and making the acute angle between neutral and maximum speed phases larger than other phase angles. This asymmetric configuration maintains operational uniformity for the rider while enabling faster shift cam rotation by preventing the excessively small acute angle problem in bottom-neutral systems.
Data Source
AI summary
A transmission apparatus includes: cam grooves 111 to 113 on a peripheral surface for moving shift forks 114 to 116; shift cam 110 that can change a rotation position from a neutral position to a maximum speed position through a first speed position; and shift mechanism 80 that intermittently rotates shift cam 110 in response to transmission operation to hold shift cam 110 at each position from the neutral position and the first speed position to the maximum speed position. Shift mechanism 80 holds shift cam 110 at a rotation position, in which a rotation angle between the neutral position and the first speed position is the same as a rotation angle between the first speed position and a second speed position, and a rotation angle between the maximum speed position and the neutral position is smaller than the rotation angle between the neutral position and the first speed position.