Power Transfer Unit Seal System for AWD Torque Efficiency
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Solution Overview
Problem
Conventional all-wheel drive (AWD) systems in motor vehicles experience power loss and higher costs due to inefficiencies in torque redistribution and reliability issues, particularly in driver-selectable AWD capabilities.
Innovation Solution
A power transfer unit with a first and second shaft, an engaging mechanism, and a seal system that includes a first and second seal, allowing for efficient torque transfer and lubrication, with a needle bearing for smooth rotation, and strategically positioned seal assemblies to reduce energy loss and improve lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional AWD systems redistribute torque continuously, then all-wheel drive capability is provided, but power loss increases and efficiency decreases
Solution Approach 1:
The system dynamically switches between 2WD and AWD modes based on actual driving conditions. The engaging mechanism allows the second shaft to be selectively coupled to or decoupled from the first shaft, enabling the system to adapt its torque distribution characteristics rather than continuously redistributing torque as in conventional AWD systems.
Solution Approach 2:
The system employs periodic engagement and disengagement of the engaging mechanism to switch between drive modes. This periodic action allows torque redistribution to occur only when necessary (in AWD mode), rather than continuously, thereby reducing overall power loss while maintaining AWD capability when needed.
2Loss of energy
If dynamic seal contact is minimized, then power loss is reduced, but sealing effectiveness may be compromised
Solution Approach 1:
The seal system is segmented into multiple seals positioned at different locations along the second shaft. This segmentation allows each seal to handle specific sealing requirements at different sections, enabling minimized dynamic contact at critical interfaces while maintaining overall sealing effectiveness through the distributed seal arrangement.
Solution Approach 2:
The seal assemblies act as intermediaries between the rotating second shaft and the stationary housing. These seals are strategically positioned to provide necessary sealing function while minimizing dynamic contact, effectively mediating between the conflicting requirements of sealing effectiveness and power loss reduction.
3Productivity
If torque redistribution is optimized, then efficiency improves, but system complexity increases
Solution Approach 1:
The engaging mechanism is merged with the torque transfer path, combining the functions of torque transmission and mode selection into a single integrated mechanism. This merging optimizes torque transfer efficiency by eliminating separate control systems while managing complexity through functional integration.
Solution Approach 2:
The second shaft serves multiple functions: it acts as a torque carrier when coupled to the first shaft, provides rotational freedom when decoupled, and interfaces with both the engaging mechanism and seal system. This multi-functionality optimizes torque redistribution efficiency while avoiding the need for additional dedicated components that would increase system complexity.
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 enhances torque transfer efficiency, reduces power loss, and improves reliability by minimizing dynamic seal contact and ensuring proper lubrication, thereby enhancing the overall performance and longevity of the drive train system.
Implementation Method 1
A needle bearing is provided between the first shaft and the second shaft to permit efficient rotation of the first shaft relative to the second shaft when the second shaft is decoupled from the first shaft
Implementation Method 2
A fluid is retained in a volume enclosed by the first and second seals
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A power transfer unit comprising a first shaft configured to receive an input torque from a first vehicle component, a second shaft configured to selectively receive the torque from the first shaft and transmit the torque to a second vehicle component, an engaging mechanism, a housing configured to enclose at least a portion of the power transfer unit, and a seal system having a first seal and a second seal. The engaging mechanism configured to operate in a first mode and a second mode. When in the first mode, the engaging mechanism selectively couples the second shaft to the first shaft, and when in the second mode, the second shaft is decoupled from the first shaft. The first seal is disposed between the housing and a first end of the second shaft, and the second seal is disposed between the housing and a second end of the second shaft.