Shift Drum Cam Sleeve Constraint for Low-Resistance Gear Shifting
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Solution Overview
Problem
Existing shifting mechanisms face issues with increased sliding resistance and potential damage to engagement pins due to friction and posture changes when rotating a shift drum, as well as excessive load on dog teeth during gear shifting.
Innovation Solution
A shifting mechanism with a cam sleeve and fork shaft that includes a support stem and projection to restrict rotation of the cam sleeve, preventing posture changes of the engagement pin and reducing sliding resistance, while using an elastic member to absorb differences in movement distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fork shaft and shift fork are formed separately to allow relative movement, then the spring can absorb movement distance differences and protect dog teeth from excessive load, but the engagement pin is subjected to friction and pushing force that changes its posture and increases sliding resistance
Solution Approach 1:
The engagement pin is formed integrally with the shift fork, merging two previously separate components. This integration ensures that the engagement pin and shift fork move together as a unified structure, preventing relative rotation and posture changes of the engagement pin while maintaining the protective function against excessive load on dog teeth.
Solution Approach 2:
Instead of allowing the fork shaft to rotate relative to the shift fork (as in the prior art), the invention prevents rotation by forming the engagement pin integrally with the shift fork. This inverts the approach: rather than using relative movement to absorb shock, it uses rigid integration to maintain proper engagement pin posture.
2Object-affected harmful factors
If the engagement pin is formed integrally with the shift fork to prevent rotation, then sliding resistance is reduced, but the dog teeth are subjected to excessive load during interference
Solution Approach 1:
The spring acts as an intermediary element between the fork shaft and the shift fork. It absorbs the difference in movement distances between these components during gear engagement, protecting the dog teeth from excessive load while allowing the engagement pin to maintain its proper posture through integral formation with the shift fork.
3Ease of operation
If the fork shaft is connected to the shift fork through a spring to allow movement, then the shift drum can rotate smoothly, but the engagement pin is subjected to friction that changes its posture and increases sliding resistance
Solution Approach 1:
The engagement pin is formed integrally with the shift fork, merging two previously separate components. This integration ensures that the engagement pin and shift fork move together as a unified structure, preventing relative rotation and posture changes of the engagement pin while maintaining the protective function against excessive load on dog teeth.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively limits sliding resistance and prevents damage to the engagement pin by maintaining the posture of the engagement pin, allowing smooth rotation of the shift drum and reducing the load on dog teeth during gear shifting.
Implementation Method 1
an elastic member that is deformed in a situation where a traveling amount of the cam sleeve in an axial direction along the center axis of the cam sleeve and a traveling amount of the fork shaft in the axial direction are different
Data Source
AI summary
A shifting mechanism, in which a movable member integrated with an engagement pin will not be rotated by a friction acting between a cam groove and the engagement pin, includes: a shift drum that on which a cam groove is formed; a cam sleeve having an engagement pin inserted into the cam groove; a fork shaft reciprocated between predetermined positions by rotating the shift drum; a support stem extending parallel to a center axis of the cam sleeve; and a projection formed integrally with the cam sleeve to come into contact with the support stem when the cam sleeve is rotated.