Shift Drum Transmission Layout for Compact Gear 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
The transmission design includes a support rod, parking lever, and biasing members to manage shift fork positioning, utilizing a chain drive for reverse torque transfer and strategically offset grooves on the shift drum to ensure proper engagement and disengagement of gears, reducing the need for lengthy rods and enhancing space utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rod includes springs to aid in biasing the shift forks toward different shift positions, then the shift forks can be biased toward different shift positions, but the rod becomes quite lengthy and the overall size of the transmission increases
Solution Approach 1:
The patent repositions the biasing springs from the longitudinal rod to the radial direction by mounting them on the shift drum. The springs extend radially outward from the drum surface, changing the dimensional orientation of the biasing mechanism from longitudinal to radial, thereby reducing the rod's length while maintaining the biasing function.
Solution Approach 2:
The shift drum serves as an intermediary component that carries the biasing springs on its surface. Instead of the rod directly supporting both the shift forks and the biasing elements, the shift drum acts as a mediator that provides mounting for the springs while the rod only needs to support the shift forks, reducing the rod's structural requirements and length.
2Ease of operation
If the shift drum groove has bends to cause the shift forks to translate along the rod, then the shift forks can be positioned correctly, but misalignment causes twisting forces on the shift fork and shift drum
Solution Approach 1:
The patent extracts the bending function from the groove design and replaces it with a straight groove combined with radially mounted biasing springs. The springs provide the necessary translational force on the shift forks without requiring the groove to have bends, thereby eliminating the twisting forces that occur when the groove bends while the shift dog is misaligned.
3Ease of operation
If the rod supports both shift forks and biasing elements, then the biasing function is provided, but the rod becomes lengthy and space efficiency is reduced
Solution Approach 1:
The biasing elements are relocated from the longitudinal dimension (rod) to the radial dimension (shift drum surface). This dimensional change allows the biasing function to be provided without increasing the longitudinal length of the rod, thereby improving space efficiency within the transmission housing.
Solution Approach 2:
The patent segments the functional responsibilities between the shift drum and the rod. The shift drum is assigned the function of mounting and providing the biasing elements, while the rod is assigned only the function of supporting the shift forks. This functional segmentation allows each component to be optimized for its specific purpose, reducing the overall size requirements.
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 design improves torque transfer efficiency, reduces the overall size of the transmission, and prevents unwanted rotation, thereby addressing the misalignment issues and space constraints in prior art.
Implementation Method 1
a biasing member disposed around the shift rod, the biasing member having a first end and a second end, the first end of the biasing member being axially fixed with respect to the shift rod; the biasing member selectively causing translation of the shift fork in a first direction to control engagement of the gear with the second shaft at a first rotational position of the shift drum
Implementation Method 2
selectively transferring torque from the first shaft to the second shaft via the chain drive
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.