Shift Drum Transmission Layout for Compact Dog Engagement
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Solution Overview
Problem
Existing vehicle transmissions with continuously variable transmissions face issues due to misalignment of shift dogs and gears, leading to undesirable twisting forces and increased size, which compromises space efficiency.
Innovation Solution
A transmission design featuring a shift drum with specific grooves and biasing members that control the translation of shift forks to ensure proper engagement of engagement dogs with gears, allowing for efficient torque transfer through multiple shift positions without excessive size or space consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rod is made lengthy to accommodate both shift forks and biasing elements, then the shift forks can be properly biased and positioned, but the overall size of the transmission increases
Solution Approach 1:
The transmission is divided into two separate rod systems: a first rod for the first shift fork and a second rod for the second shift fork. This segmentation allows each rod to be optimized independently, preventing the need for an excessively long single rod while maintaining proper biasing and positioning for both shift forks.
Solution Approach 2:
The biasing elements are positioned at different axial locations along their respective rods rather than being stacked linearly. This spatial arrangement in multiple dimensions allows both biasing elements to fit within a compact axial space, reducing the overall transmission size while maintaining proper function.
2Ease of operation
If the shift fork follows the groove while encountering resistance from misaligned shift dog, then twisting forces are generated on the shift fork and shift drum
Solution Approach 1:
The groove in the shift drum acts as an intermediary element that guides the shift fork's movement. The groove is specifically designed with bends that coordinate with the shift dog's movement path, allowing the shift fork to follow a controlled trajectory that accommodates minor misalignments without generating harmful twisting forces.
Solution Approach 2:
The groove includes bends that allow dynamic adjustment of the shift fork's path during engagement. These bends enable the shift fork to adapt its position slightly as it moves, facilitating smooth engagement even when there are minor alignment variations between the shift dog and gear 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 enables efficient torque transfer across various shift positions, minimizing twisting forces and reducing the overall size of the transmission, thereby improving space efficiency and operational performance.
Implementation Method 1
a first biasing member disposed around the shift rod, the first biasing member having a first end and a second end... a second biasing member disposed around the shift rod, the second biasing member having a first end and a second end... at least a portion of the second groove and the first biasing member causing the first shift fork to selectively translate along the fork rod... at least a portion of the third groove and the second biasing member causing the second shift fork to selectively translate along the fork rod
Data Source
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AI summary
A transmission includes a first shaft with two gears adapted for connecting to a motor and a second shaft with two corresponding gears adapted for connecting to a driveshaft; a shift drum selectively controlling torque transfer between the shafts and defining therein two grooves; a shift rod translatable along a rod axis with a driving member fixedly connected thereto and engaging one groove, at least a portion of the groove causing the driving member and the shift rod to translate along the rod axis upon rotation of the shift drum; an engagement dog disposed on the second shaft for selectively engaging the gears of the second shaft; two biasing members disposed around the shift rod; a fork rod supporting a shift fork slidably connected to the fork rod and the shift rod, the shift fork being engaged in another groove of the shift drum.