Power Transfer Unit Non-Rotating Piston Driveline Efficiency
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Solution Overview
Problem
Current all-wheel drive vehicle drivelines experience efficiency losses due to oil churning, viscous drag, inertia, and friction when operating in 4x2 mode, necessitating a solution to completely idle the secondary auxiliary drive system and reduce driveline losses.
Innovation Solution
A power transfer unit (PTU) with a non-rotating piston and housing design, coupled with an electronic control unit (ECU) and hydraulic control unit (HCU), allows for the disconnection and re-engagement of the secondary auxiliary drive system across all operating speeds, enabling efficient torque transfer and reduced driveline losses by idling the secondary system in 4x2 mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the secondary auxiliary drive system remains connected during 4x2 mode operation, then the vehicle maintains all-wheel drive capability, but driveline efficiency losses occur due to oil churning, viscous drag, inertia, and friction
Solution Approach 1:
The patent implements a dynamically reconfigurable driveline system where the secondary auxiliary drive system can transition between connected and disconnected states. A disconnect coupling device enables the secondary drive shaft to be selectively separated from the primary drive system, allowing the system to adapt its configuration based on operating mode (4x2 or 4x4), thereby eliminating energy losses during 4x2 operation while maintaining AWD capability when needed
Solution Approach 2:
The driveline system is segmented into independent modules: primary drive system, secondary auxiliary drive system, and a disconnect coupling device. This segmentation allows the secondary drive system to be isolated and idled separately from the primary system during 4x2 mode, eliminating parasitic losses while preserving the ability to re-engage for 4x4 operation
2Loss of energy
If the secondary auxiliary drive system is disconnected to idle during 4x2 mode, then driveline efficiency losses are reduced, but the complexity of the drive system increases due to additional disconnect and re-engage mechanisms
Solution Approach 1:
A disconnect coupling device serves as an intermediary mechanism between the primary and secondary drive systems. This intermediary component facilitates the selective connection and disconnection of the secondary drive shaft, enabling efficient idling during 4x2 mode while providing a controlled interface for re-engagement when 4x4 capability is required, thereby managing system complexity through a dedicated control mechanism
3Volume of moving object
If a conventional rotating piston design is used in the power transfer unit, then torque transfer is maintained, but packaging efficiency within the vehicle driveline is reduced
Solution Approach 1:
The patent inverts the conventional piston design by making the piston non-rotating while allowing the piston housing to rotate with the input shaft. This inversion enables more efficient packaging within the power transfer unit by eliminating the need for the piston to rotate, thereby reducing the volume required for piston movement while maintaining torque transfer capability through the stationary piston and rotating housing configuration
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 effectively reduces driveline efficiency losses, improves fuel economy, and enhances packaging efficiency within the vehicle driveline by allowing the secondary auxiliary drive system to coast to a non-rotational stop, while maintaining operational readiness for 4x4 mode.
Implementation Method 1
a hydraulic control unit (HCU) in hydraulic communication with the piston chamber to supply hydraulic pressure to the piston chamber to actuate the piston
Implementation Method 2
allowing the secondary auxiliary drive system to rotationally coast to a stop
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A power transfer unit (PTU) (101) for a motive device includes an outer housing (229, 230) and a torque transferring clutch (216, 217, 218, 222). The PTU (101) also includes a piston housing (240) located between the outer housing (229, 230) and the torque transferring clutch (216, 217, 218, 222), and a piston (211) in the piston housing (240). The piston (211) is arranged to provide actuation forces to the torque transferring clutch (216, 217, 218, 222), and to restrict reaction forces back to the piston housing (240).