AWD Driveline Multi-Disconnect Mechanism for Flat Towing
Solution Overview
Problem
Current all-wheel drive (AWD) drivelines with front-wheel drive architecture face challenges in disconnecting the drivetrain during flat towing, leading to backdriving issues and increased complexity due to additional components required for secondary drivelines.
Innovation Solution
The implementation of a driveline system with a power take-off unit (PTU) and a multi-disconnect mechanism, including a shift sleeve and clutch members, allows for selective coupling and decoupling of drivetrain components to manage power transmission and disconnection, enabling efficient flat towing by controlling the engagement and disengagement of drivetrain segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-disconnect mechanism with shift sleeve and clutch members is implemented, then the ability to disconnect drivetrain components during flat towing is improved, but the device complexity increases
Solution Approach 1:
The drivetrain is divided into separable segments through the multi-disconnect mechanism. The shift sleeve can disconnect the power take-off unit from the secondary driveline, and the clutch members can disconnect the differential output from the primary driveline. This segmentation allows the drivetrain to be disconnected in multiple stages, enabling flat towing while maintaining manageable complexity through modular disconnection points.
Solution Approach 2:
The disconnect mechanism transforms the static drivetrain into a dynamic system that can change its connectivity state. The shift sleeve moves between engaged and disengaged positions, and the clutch members can be selectively activated or deactivated. This dynamic capability allows the system to adapt between different operating modes (AWD, 2WD, flat towing) without permanent structural changes.
2Adaptability or versatility
If additional components are added to enable disconnecting the drivetrain, then the operational versatility is improved, but the manufacturing complexity increases
Solution Approach 1:
The shift sleeve and clutch members serve multiple functions within the drivetrain system. The shift sleeve not only disconnects the power take-off unit but also manages the engagement between different driveline segments. The clutch members provide both connection and disconnection capabilities while also serving as torque transmission elements when engaged. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
The disconnect mechanism components are nested within the existing drivetrain structure. The shift sleeve is positioned within the power take-off unit housing, and the clutch members are integrated into the differential and driveline connections. This nesting approach allows the additional components to be incorporated into the existing manufacturing flow without requiring completely separate assembly processes.
3Device complexity
If the drivetrain is kept connected during flat towing, then the structural simplicity is maintained, but harmful backdriving effects occur
Solution Approach 1:
The harmful backdriving effect is eliminated by extracting the connection between the drivetrain components during flat towing. The shift sleeve disconnects the power take-off unit from the secondary driveline, and the clutch members disconnect the differential from the primary driveline. This extraction of the mechanical connection prevents the backdriving force from being transmitted through the drivetrain components.
Solution Approach 2:
The disconnect mechanism provides preliminary protection against backdriving by preemptively disconnecting the drivetrain components before towing begins. Rather than allowing backdriving to occur and then correcting it, the system is configured to be disconnected in advance, preventing the harmful effect from occurring in the first place.
Data Source
AI summary
An all-wheel drive vehicle driveline that includes a PTU input member, a spindle, a stub shaft, an axle shaft, a PTU clutch and a stub shaft clutch. The PTU input member, the spindle, the stub shaft and the axle shaft are rotatable about a first rotary axis. The axle shaft is received through the spindle. The PTU clutch is operable in a first PTU clutch mode, in which the PTU input member is rotatably coupled to the spindle, and a second PTU clutch mode in which the PTU input member is rotatably decoupled from the spindle. The stub shaft clutch is operable in a first stub shaft clutch mode, in which the stub shaft is rotatably coupled to the axle shaft, and a second stub shaft clutch mode, in which the stub shaft is rotatably de-coupled from the axle shaft.