Parabolic Shift Drum Grooves for Reduced Acceleration Peaks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional shift drums in manual transmissions cause noise and wear due to undesired acceleration peaks in shift forks, as their guide grooves are defined by a combination of straight and circular arc sections, leading to force peaks during gear shifting.
Innovation Solution
A shift drum with a groove profile defined by parabolic sections or spline functions of at least the second degree, ensuring constant axial acceleration and continuous transitions, minimizing noise and wear by maintaining constant acceleration or deceleration values throughout the shifting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If guide grooves are defined by a combination of straight and circular arc sections, then the manufacturing is simple, but acceleration peaks and force peaks occur during shifting
Solution Approach 1:
The patent changes the mathematical parameters defining the groove profile from linear and circular arc sections to parabolic sections or spline functions of at least the second degree. This parameter change transforms the acceleration characteristics from peaked values to constant or continuously varying values, eliminating harmful acceleration peaks while maintaining manufacturability through standard machining processes.
Solution Approach 2:
The patent applies continuous curvature through parabolic sections or spline functions to the groove profile, replacing the discontinuous curvature of straight and circular arc sections. This continuous curvature ensures smooth transitions and constant acceleration, eliminating the abrupt changes that cause force peaks during shifting operations.
2Device complexity
If conventional guide groove profiles are used, then the structure is simple, but noise and wear increase during shifting
Solution Approach 1:
The patent modifies the groove profile parameters to parabolic sections or spline functions, which create constant acceleration characteristics. This reduces impact forces and vibrations during shifting, thereby decreasing noise and wear on transmission components while maintaining a relatively simple overall drum structure.
Solution Approach 2:
The continuous curvature of parabolic or spline-based groove profiles eliminates abrupt directional changes that cause impact loading. This smooth curvature reduces mechanical shocks and vibrations, leading to lower noise levels and reduced wear on shift forks and related components.
3Device complexity
If straight and circular arc sections are used in guide grooves, then the design is straightforward, but acceleration is not constant during shifting
Solution Approach 1:
The patent changes the mathematical description of the groove profile from piecewise linear and circular arc functions to parabolic sections or spline functions of at least the second degree. This parameter transformation ensures that the second derivative (acceleration) is constant or continuously varying, providing controlled and constant axial acceleration during shifting operations.
Solution Approach 2:
The use of parabolic sections or spline functions provides continuous curvature throughout the groove profile, ensuring smooth and constant acceleration characteristics. This eliminates the acceleration variations inherent in straight and circular arc combinations, achieving more uniform shifting behavior.
Data Source
Figure 1~2
AI summary
A selector drum for a shift transmission of a motor vehicle includes a substantially cylindrical drum body which has a longitudinal axis and a guide groove on a radial outer face. An actuating pin of a selector fork of the shift transmission can engage into the guide groove. The guide groove has an active groove region, which defines an axial movement of the selector fork, and an inactive groove region, which defines an axially constant neutral position of the shift fork. A groove course at least of the active groove region of the guide groove is determined by parabola sections and/or a spline function.