Shift Drum Shared Lead Groove Layout for Flexible Shift Fork Design
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Solution Overview
Problem
The existing gear transmission systems with shared lead grooves on shift drums have limited design freedom due to predetermined opening angles between engaging protrusions, restricting the layout and design of internal combustion engines and shift forks.
Innovation Solution
The transmission system incorporates a shift drum with multiple lead grooves, including shared lead grooves, where the position of the boss center line is offset from the fork action part, allowing for a predetermined opening angle between engaging protrusions, enabling flexible design and layout without being limited by the fixed angle, and includes shift forks with overlapping fork pushing parts to reduce stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a shared lead groove is used to engage multiple shift forks, then the number of lead grooves is reduced and the shift drum width is reduced, but the opening angle between engaging protrusions is fixed at predetermined multiples of the feed angle, limiting design freedom
Solution Approach 1:
The shared lead groove is divided into multiple lead groove parts (first lead groove part, second lead groove part, etc.) that are dislocated in the circumferential direction. Each lead groove part engages with a corresponding engaging protrusion of a shift fork, allowing independent positioning of each shift fork while sharing a common groove structure. This segmentation enables reduced drum width while maintaining design flexibility.
Solution Approach 2:
The invention introduces a new degree of freedom by allowing the boss center line of a shift fork to be offset from the drum rotation center line by a predetermined opening angle. This dimensional change from radial alignment to angular offset enables the shift fork layout to be independently configured without being constrained by the fixed multiples of feed angle, thus improving adaptability while maintaining the compact shared groove structure.
2Reliability
If the opening angle between engaging protrusions is set to predetermined multiples of feed angle (e.g., 120 degrees for 5- or 6-speed transmission), then the shared lead groove can properly engage multiple shift forks, but the relative positions of fork shafts are restricted, limiting layout flexibility
Solution Approach 1:
The invention makes the system more dynamic by allowing the opening angle between the boss center line and the fork action part to be independently adjustable. This dynamic configuration enables the shift fork layout to adapt to different transmission designs while the lead groove parts maintain reliable engagement through their dislocated circumferential positions. The fork shafts can be positioned at different angles relative to the drum rotation center line, providing layout flexibility without compromising engagement reliability.
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
This configuration enhances the degree of freedom in designing internal combustion engines and shift fork layouts, improves shift operation characteristics, and allows for a more compact transmission mechanism while efficiently transmitting forces.
Implementation Method 1
multiple lead grooves engaging with engaging protrusions of shift forks are formed on a shift drum, and the shift fork moves as the engaging protrusion is pushed by the lead groove due to rotation of the shift drum
Data Source
AI summary
A transmission in which multiple shift forks are moved by a shared lead groove of a shift drum has an improved degree of freedom of design of an internal combustion engine as well as an improved degree of freedom of layout of shift forks. The transmission includes multiple shift forks having engaging protrusions that engage with a shared lead groove. At least one shift fork among the multiple shift forks has an opening angle α around a drum rotation center line of a shift drum between a boss center line as a cylindrical center line of a cylindrical boss that is axially supported by a fork shaft of the shift fork, and a fork action part of the engaging protrusion on which the shared lead groove acts in accordance with rotation of the shift drum.