Twin Countershaft Transmission Spline for Shaft Misalignment
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Solution Overview
Problem
The buildup of tolerances between the main transmission shaft and the sun gear in heavy-duty transmission designs leads to eccentric alignment, causing wear and early life failure, particularly in configurations like the 3x3x2 transmission where radial displacement of the input shaft increases, resulting in misalignment and increased linear displacement.
Innovation Solution
A clearance fit spline joint is introduced to accommodate radial displacement and misalignment between the main shaft and the range center shaft, allowing for proper torque transfer while reducing wear in bearings by providing axial clearance and balancing axial forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a direct engagement between the main shaft and sun gear is used to transfer torque, then torque transfer efficiency is improved, but tolerance buildup causes eccentric alignment leading to wear and early failure
Solution Approach 1:
A spline connection is introduced as an intermediary element between the main shaft and sun gear. The spline allows for relative radial movement to accommodate misalignment while maintaining torque transfer, thus resolving the contradiction between efficient power transfer and reliability by mediating the connection between the two components.
Solution Approach 2:
The invention changes the connection parameters from rigid direct engagement to a flexible spline connection with radial clearance. This parameter change allows the system to tolerate eccentric alignment caused by tolerance buildup while maintaining effective torque transfer, thereby improving reliability without sacrificing power transfer efficiency.
2Productivity
If the number of gear ratios is increased to facilitate skip shifting, then fuel efficiency is improved, but the range gearbox section increases device complexity
Solution Approach 1:
The planetary gear system is nested within the range gearbox section, allowing multiple gear ratios to be achieved through a compact nested structure. This nesting approach enables increased gear ratio options for improved fuel efficiency while minimizing the increase in overall device complexity through space-efficient design.
3Manufacturing precision
If tolerance buildup is reduced to maintain alignment, then manufacturing precision is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The spline connection with radial clearance serves as a beforehand cushioning mechanism that anticipates and accommodates tolerance buildup. Instead of requiring extremely tight tolerances during manufacturing, the spline's inherent clearance provides a buffer that absorbs misalignment, thereby maintaining alignment precision without requiring prohibitively expensive manufacturing processes.
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 spline joint effectively reduces eccentric loads and wear on bearings, maintaining proper alignment and torque transfer, thus extending the transmission's lifespan and operational efficiency.
Implementation Method 1
A clearance fit spline joint is introduced to accommodate radial displacement and misalignment between the main shaft and the range center shaft, allowing for proper torque transfer
Implementation Method 2
The spline joint effectively reduces eccentric loads and wear on bearings, maintaining proper alignment and torque transfer
Implementation Method 3
reducing wear in bearings by providing axial clearance and balancing axial forces
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A transmission includes a countershaft, a splitter section having an input shaft and a clutch that couples the input shaft to the countershaft, a main transmission assembly having a main shaft and a main transmission clutch, the main shaft coupled to the countershaft via the main transmission clutch, a range gear assembly having a an annulus gear, a sun gear, a planet gear, and center shaft that provides output from the transmission, and a spline joint that couples the main shaft to the center shaft and in operation transfers torque through and reduces eccentric loads between the main shaft and the center shaft that occur due to axial misalignment.