Shift Fork Shaft Oil Path for Bidirectional Gear Shifting
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Solution Overview
Problem
Existing dog-clutch type stepped transmissions face challenges in providing adequate oil supply to shift forks, leading to insufficient lubrication and undesirable gear-shifting feel due to the complexity of oil supply systems and limited movement of shift fork shafts.
Innovation Solution
A transmission design that includes an oil supply path and radial oil supply holes in the shift fork shaft, allowing direct oil supply to shift forks, and the use of springs to maintain the shift fork shaft at a neutral position for bidirectional movement, ensuring proper gear-shifting feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oil supply path is provided inside the shift fork shaft, then oil supply to shift forks is improved, but the shift fork shaft cannot move bidirectionally due to hydraulic pressure
Solution Approach 1:
The shift fork shaft is divided into multiple sections with through-holes at different positions. Oil supply paths are provided in specific sections rather than continuously throughout the shaft, allowing the shaft to be segmented into oil-supplying portions and non-oil-supplying portions. This segmentation enables bidirectional movement by removing hydraulic pressure restrictions in certain sections while maintaining oil supply functionality where needed.
Solution Approach 2:
Different sections of the shift fork shaft have different structural characteristics. Some sections contain oil supply paths while others are open through-holes without oil supply paths. This local differentiation allows the shaft to provide oil supply where required while maintaining freedom of movement in sections where oil supply is not needed, resolving the contradiction between reliable oil supply and bidirectional movement capability.
2Reliability
If oil supply paths are provided in the shift fork shaft, then lubrication is improved, but the structure becomes more complex
Solution Approach 1:
The oil supply function is merged directly into the shift fork shaft structure itself rather than being provided by separate external oil supply systems. The shift fork shaft integrates both mechanical support and oil supply functions, eliminating the need for additional dedicated oil supply components and reducing overall system complexity while ensuring reliable lubrication.
Solution Approach 2:
Instead of providing continuous oil supply paths throughout the entire shift fork shaft, the oil supply paths are segmented and provided only in specific sections where needed. This selective segmentation reduces the complexity of the shaft structure compared to a fully enclosed oil supply system, while still achieving reliable lubrication at the shift fork contact points.
3Manufacturing precision
If the shift fork shaft is constrained to prevent movement, then positioning precision is improved, but gear-shifting feel deteriorates
Solution Approach 1:
The shift fork shaft is designed with dynamic positioning capability rather than rigid constraint. The shaft can move bidirectionally within the transmission case, allowing it to dynamically adjust its position during gear-shifting operations. This dynamic freedom of movement improves gear-shifting feel by reducing mechanical binding and friction, while the shaft still maintains adequate positioning through its engagement with shift forks and engagement with the transmission case at specific locations.
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 design enables efficient oil supply to shift forks, improving gear-shifting feel by allowing the shift fork shaft to move freely in both directions, thus enhancing the overall performance of the transmission.
Implementation Method 1
the oil supply path communicates with a first hole portion through a first opening, and communicates with a second hole portion through a second opening
Implementation Method 2
the use of springs to maintain the shift fork shaft at a neutral position for bidirectional movement
Data Source
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AI summary
A shift fork shaft 100 includes a first end portion 101 at which a first opening 101a is formed, a second end portion 102 at which a second opening 102a is formed that is open in an opposite way from the first opening 101a, an oil supply path 103 that extends in an axial direction, and an oil supply hole 103a that extends in a radial direction and is connected to an oil supply path 103. A transmission case 38 includes a first hole portion 141 into which the first end portion 101 of the shift fork shaft 100 is inserted, and a second hole portion 142 into which the second end portion 102 is inserted. The first hole portion 141 communicates with an oil pump 69 and communicates with the oil supply path 103 through the first opening 101a. The second hole portion 142 communicates with the oil supply path 103 through the second opening 102a.