Shift Drum Lead Groove Design for Vehicle Transmission
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Solution Overview
Problem
Existing vehicle transmission systems face challenges in increasing shift positions without enlarging the shift drum diameter and modifying the lead groove shape, which complicates design and operation.
Innovation Solution
A vehicle transmission design featuring a shift drum with a particular lead groove that continuously extends beyond one circle and has ends out of alignment axially, allowing for increased shift positions without enlarging the diameter, and a control unit that determines gear train states using a turning angle detector to manage engine start and gear shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the diameter of the shift drum is increased to accommodate more shift positions, then the number of shift positions increases, but the transmission size enlarges
Solution Approach 1:
The patent applies dimensionality change by making the lead groove continuous beyond one circle of the shift drum, utilizing the axial direction to create additional shift positions. The groove extends axially offset to one side, allowing the shift fork to engage at multiple positions (including a common shift position) without increasing the drum's radial diameter, thus adding shift positions while maintaining compact transmission size.
2Adaptability or versatility
If the shape of the lead groove is significantly changed to increase shift positions, then the number of shift positions increases, but design manhours increase
Solution Approach 1:
The lead groove is segmented into multiple engagement regions along its continuous path beyond one circle. The groove includes specific sections (first engagement section, second engagement section, third engagement section) that correspond to different shift positions, allowing the same groove structure to serve multiple functions without requiring complete redesign.
Solution Approach 2:
The continuous lead groove serves multiple functions: it guides the shift fork to different shift positions, establishes different gear trains, and provides a common shift position for both reverse and highest shift stage gear trains. This multi-functional design increases shift positions without requiring separate grooves for each function, reducing design complexity.
3Adaptability or versatility
If a common shift position is set at one position corresponding to both ends of the lead groove, then gear trains with two different shift stages can be established at one position, but the control system complexity increases
Solution Approach 1:
The patent employs a turning angle detector that provides feedback on the shift drum's angular position to the control unit. The control unit uses this feedback information to determine whether the shift drum is at the common shift position and which gear train is currently established, enabling accurate control despite the multi-functional nature of the common shift position.
Data Source
AI summary
An outer circumference of a shift drum of a vehicle transmission is provided with at least one particular lead groove among multiple lead grooves which continuously extends beyond one circle of the shift drum. Two ends of the particular lead groove are arranged so as to be out of alignment with each other in the axial direction of the shift drum. A common shift position adapted to establish gear trains with two shift stages different from each other is set at one position corresponding to the two ends of the particular lead groove along the circumferential direction of the shift drum. The resulting configuration prevents an increase in the diameter of a shift drum and eliminates the significant change of the shape of a lead groove, even as the number of shift positions set on the shift drum is increased.