PTU Synchronizer Decoupling for AWD Fuel Efficiency
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Solution Overview
Problem
Modern all-wheel drive (AWD) drivelines based on front-wheel drive (FWD) architecture are less fuel efficient due to components being rotatably driven even when power is not transmitted, resulting in a one to two miles per gallon disadvantage compared to similar FWD drivelines.
Innovation Solution
A vehicle driveline system comprising a primary driveline, a power take-off unit (PTU) with a synchronizer for selective decoupling, and a secondary driveline with a propshaft, differential, and torque transfer devices, allowing for efficient power distribution to both sets of wheels and enabling disconnection of power transmission when not needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an all-wheel drive driveline is used to improve traction and performance, then vehicle capability is enhanced, but fuel efficiency deteriorates due to continuous rotation of driveline components even when power is not transmitted
Solution Approach 1:
The patent implements a dynamic disconnect mechanism that allows the driveline to transition between connected and disconnected states. The synchronizer assembly enables the output shaft to be dynamically decoupled from the input shaft when all-wheel drive is not needed, allowing components to rotate only when power is actively transmitted, thereby improving fuel efficiency while maintaining vehicle capability when required
Solution Approach 2:
The driveline is segmented into separable components with the ability to disconnect the secondary driveline from the primary driveline. The synchronizer mechanism divides the power transmission path, allowing the secondary driveline (including propshaft, differential, and axles) to be isolated from the power source when not in use, eliminating parasitic energy losses while preserving full AWD capability when needed
2Use of energy by moving object
If a disconnectable all-wheel drive system is implemented to improve fuel efficiency, then energy consumption is reduced, but device complexity increases due to additional synchronizer and decoupling mechanisms
Solution Approach 1:
The synchronizer assembly serves multiple functions: it acts as a disconnect mechanism, a synchronization device for smooth engagement, and a control point for switching between FWD and AWD modes. This multi-functionality reduces the need for separate components and simplifies the overall system architecture despite the added capability
Solution Approach 2:
The synchronizer assembly acts as an intermediary mechanism between the primary and secondary drivelines. It provides a controlled interface that manages the connection and disconnection process, smoothing transitions and reducing the complexity of direct coupling mechanisms while enabling fuel efficiency improvements
Data Source
AI summary
A vehicle with primary and secondary drivelines and a power take-off unit (PTU). The primary driveline has a first differential that is configured to distribute power to a first set of wheels. The PTU has a PTU input, a PTU output and a synchronizer for selectively de-coupling the PTU output from the PTU input. The secondary driveline is configured to distribute power to a second set of wheels and has a propshaft, a second differential, a pair of half-shafts and at least one torque transfer device (TTD). The propshaft transmits rotary power between the PTU output and an input of the second differential. The half-shafts are rotatably coupled to an output of the second differential and are configured to transmit rotary power to the second set of wheels. The at least one TTD is configured to selectively inhibit torque transmission through the second differential to the second set of wheels.