Planetary Interaxle Differential Shift Collar Torque Control
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Solution Overview
Problem
Current drive axle systems with planetary interaxle differentials face inefficiencies in torque distribution, leading to churning losses and reduced fuel economy, especially when torque demands are low, as they cannot selectively disconnect from the torque source and wheel assemblies without compromising axle operation.
Innovation Solution
A drive axle system with a shift collar mechanism that allows the interaxle differential unit to connect or disconnect the sun gear from either the drive pinion or the planet carrier, enabling selective torque transmission between the input shaft, drive pinion, and output shaft, thereby optimizing torque distribution and reducing churning losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the planetary interaxle differential is continuously engaged to maintain torque distribution capability, then axle operation reliability is improved, but churning losses increase and fuel economy deteriorates during low torque demand conditions
Solution Approach 1:
The system dynamically transitions between engaged and disconnected states based on torque demand conditions. The disconnect mechanism allows the planetary differential to be disengaged from the torque path during low-demand conditions, eliminating churning losses while maintaining the capability to re-engage when torque distribution is needed.
Solution Approach 2:
The patent extracts the planetary differential from the continuous torque transmission path by introducing a disconnect mechanism. This allows the differential to be removed from active operation during conditions where it would generate harmful churning losses, while preserving the ability to re-integrate it when needed for torque distribution.
2Loss of energy
If the planetary interaxle differential is disconnected to reduce churning losses and improve fuel economy, then energy efficiency is improved, but torque distribution capability is lost
Solution Approach 1:
The system employs dynamic state transitions, switching between connected and disconnected configurations based on operating conditions. The disconnect mechanism is reversible, allowing the planetary differential to be re-engaged when torque distribution becomes necessary, thus maintaining capability while improving efficiency during low-demand periods.
Solution Approach 2:
The system monitors its own operational needs and automatically transitions between engaged and disconnected states. The disconnect mechanism is designed to allow the differential assembly to remain stationary when not needed, self-regulating its participation in torque transmission based on demand conditions.
3Loss of energy
If the shift collar is used to selectively connect or disconnect the sun gear, then torque distribution optimization is achieved, but device complexity increases
Solution Approach 1:
The shift collar serves multiple functions: it selectively connects or disconnects the sun gear from the carrier, controls engagement of the planetary differential, and enables transition between torque distribution modes. This multi-functionality reduces the need for separate mechanisms for each control function.
Solution Approach 2:
The shift collar acts as an intermediary element between the input shaft and the planetary gear components. It mediates the torque transmission path, selectively allowing or blocking torque flow through the sun gear based on operational requirements, thus simplifying the overall control architecture.
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 solution enhances axle operating efficiency and fuel economy by allowing the differential assembly to remain stationary when not needed, reducing drag forces and improving torque distribution, thus enhancing vehicle propulsion and acceleration efficiency.
Implementation Method 1
The planet gear meshes with the planetary ring gear and the sun gear
Data Source
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AI summary
A drive axle system (12) having a planetary interaxle differential unit. A shift collar (44) may be movable along an axis between a first position and a second position. The shift collar may operatively connect a sun gear to a drive pinion (36) when in the first position. The shift collar may operatively connect the sun gear to a planet carrier when in a second position.