Drive Axle Torque Disconnection for Churning Loss Reduction
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Solution Overview
Problem
Existing drive axle systems with planetary interaxle differentials face inefficiencies in torque transmission and fuel economy due to the continuous operation of differentials, leading to churning losses and reduced axle efficiency, especially when torque demands are low.
Innovation Solution
A method for controlling a drive axle system that includes an interaxle differential unit, shift collar, and wheel end disconnects, allowing for the discontinuation of torque transmission to the wheel assemblies when input torque is reduced, and shifting the shift collar to prevent further torque transmission, thereby reducing churning losses and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the planetary interaxle differential operates continuously, then torque can be transmitted to wheel assemblies under varying conditions, but churning losses increase and axle efficiency decreases during low torque demands
Solution Approach 1:
The control system preliminarily determines whether torque transmission should be discontinued by evaluating input torque thresholds before actual disconnection occurs. This preliminary assessment allows the system to prepare for efficient operation by anticipating low-torque conditions and preventing unnecessary differential operation, thereby reducing churning losses before they occur.
Solution Approach 2:
The system dynamically adjusts its operation by switching between engaged and disengaged states based on real-time torque conditions. The planetary differential transitions from a continuously operating component to a conditionally engaged component, allowing the system to optimize efficiency by disengaging during low-torque conditions while maintaining reliability when torque demands increase.
2Use of energy by moving object
If the wheel end disconnect operates to discontinue torque transmission, then fuel economy improves, but the complexity of the drive axle system increases
Solution Approach 1:
The wheel end disconnect mechanism serves multiple functions: it acts as a torque transmission path when engaged, provides a disconnection capability during low-torque conditions, and integrates with the existing differential and axle shaft structures. This multi-functionality allows the system to improve fuel economy without requiring entirely separate systems for each function, thereby limiting the increase in overall complexity.
Solution Approach 2:
The wheel end disconnect acts as an intermediary component between the differential and the wheel assembly, enabling controlled torque transmission or disconnection. This mediator approach allows the system to achieve fuel economy improvements through selective engagement while maintaining a relatively simple architecture compared to completely redundant systems.
3Productivity
If the shift collar is shifted to discontinue torque transmission to the differential, then axle operating efficiency improves, but the mechanical complexity of the torque path control increases
Solution Approach 1:
The shift collar integrates multiple control functions into a single component that simultaneously manages torque transmission paths to both the left and right axles. By merging the torque path control functionality into one unified mechanism rather than separate controls for each axle, the system improves operating efficiency while limiting the increase in mechanical complexity.
Solution Approach 2:
The shift collar provides segmented control capability, allowing independent engagement or disengagement of torque paths to different axles. This segmentation enables precise control of torque distribution to optimize efficiency in various operating conditions while maintaining a relatively simple overall structure through the use of a single collared component.
Data Source
AI summary
A method of controlling a drive axle system. The drive axle system may include first and second drive axle assemblies. A drive axle assembly may be disconnected by operating a wheel end disconnect to discontinue transmission of torque between a wheel assembly and a differential and by discontinuing the transmission of torque to the differential.