Shift Fork Pin Rolling on Lead Groove to Reduce Torque
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Solution Overview
Problem
Conventional speed change apparatuses for power units face challenges in efficiently shifting gears due to high friction between the pin portion and the slant wall surface of the lead groove, requiring higher torque and limiting the miniaturization of the shift motor.
Innovation Solution
The design features a shift fork with a separate rotatably supported pin portion that rolls on the slant wall surface of the lead groove, reducing friction from sliding to rolling friction, and uses needle bearings to further minimize rotational friction, allowing for a more compact structure and reduced torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the pin portion slides on the slant wall surface of the lead groove, then the gear shifting function is achieved, but high friction occurs requiring higher torque
Solution Approach 1:
The pin portion is changed from a sliding contact design to a rolling contact design with a curved surface that rolls on the slant wall surface of the lead groove. This curvature transformation converts sliding friction into rolling friction, significantly reducing the friction force and torque requirement for gear shifting.
Solution Approach 2:
A needle bearing is introduced as an intermediary element between the pin portion and the lead groove. The needle bearing enables rolling motion and reduces direct contact friction, acting as a mediator that transforms the high-friction sliding interface into a low-friction rolling interface.
2Length of moving object
If conventional sliding friction is used between pin portion and lead groove, then gear shifting is achieved, but shift motor size cannot be reduced
Solution Approach 1:
The pin portion is designed with a curved rolling surface that contacts the slant wall surface of the lead groove. This curvature enables rolling motion instead of sliding, reducing the friction torque that the shift motor must overcome, thereby allowing for a smaller, more compact shift motor design.
Solution Approach 2:
The needle bearing serves as an intermediary that facilitates rolling contact between the pin portion and lead groove. By introducing this rolling element, the friction is dramatically reduced, enabling the use of a smaller shift motor with reduced size and weight.
3Loss of energy
If the pin portion is integrated with the main body portion, then structure is simplified, but friction cannot be reduced
Solution Approach 1:
The shift fork is divided into separate components: the main body portion and the pin portion. This segmentation allows the pin portion to be designed specifically for rolling contact with the lead groove, reducing friction, while the main body portion maintains the fork engagement function. The separation enables optimization of each component for its specific function.
Solution Approach 2:
The needle bearing is introduced as a separate intermediary component between the pin portion and the main body portion, enabling rolling motion. This additional component, while increasing structural complexity, dramatically reduces friction and energy loss, justifying the increased complexity through significant performance improvement.
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 reduces the torque required for gear shifting, enabling miniaturization of the shift motor and improving the efficiency and compactness of the speed change apparatus.
Implementation Method 1
reducing friction from sliding to rolling friction
Implementation Method 2
uses needle bearings to further minimize rotational friction
Data Source
AI summary
A cylindrical shift drum is rotatable around a third rotational axis. The cylindrical shift drum includes at least one lead groove in an outer circumferential surface of the cylindrical shift drum. A shift fork shaft extending in parallel to the third rotational axis is disposed opposite to the outer circumferential surface. At least one shift fork includes a main portion slidably supported by the shift fork shaft and a pin portion rotatably supported by the main body portion. The main body portion includes a fork portion to be engaged with at least one shifter gear. The pin portion is inserted in one of the at least one lead groove. The cylindrical shift drum is to be rotated to guide the pin portion along the one of the at least one lead groove to move the at least one shift fork to shift the at least one shifter gear.