Idle-able Power Transfer Unit for Driveline Loss Reduction
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Solution Overview
Problem
Conventional AWD drivelines experience significant losses and inefficiencies when operating in 4X2 mode due to frictional losses in the secondary rear drive axle, which affects fuel efficiency and requires a means to completely idle the auxiliary drive system.
Innovation Solution
The implementation of an idle-able power transfer unit with a hydraulically-actuated multi-plate clutch and wheel hub disconnects allows for the selective disconnection of the auxiliary drive system, enabling complete idling by controlling hydraulic pressure to manage torque transfer and disconnect the rear drive wheels from the half shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the secondary rear drive axle remains connected in 4X2 mode, then the vehicle maintains all-wheel drive capability, but driveline losses increase due to frictional losses in the auxiliary drive system
Solution Approach 1:
The power transfer unit incorporates a hydraulically-actuated multi-plate clutch that enables dynamic switching between connected and disconnected states. The clutch allows the auxiliary drive system to be completely idled when not needed, while maintaining the ability to re-engage for all-wheel drive operation, thus resolving the contradiction between energy loss and drive capability.
Solution Approach 2:
The invention extracts the torque transfer function from the continuous connection and places it under controlled engagement through the multi-plate clutch. This allows the auxiliary drive system to be completely separated (idled) when not needed, eliminating frictional losses while preserving the ability to re-engage when all-wheel drive is required.
2Use of energy by moving object
If the auxiliary drive system is completely idled, then fuel efficiency improves, but the ability to transfer torque to the rear wheels is lost
Solution Approach 1:
The hydraulically-actuated multi-plate clutch provides dynamic control of torque transfer. When hydraulic pressure is applied, the clutch engages to transfer torque to the rear wheels. When pressure is released, the clutch disengages to idle the auxiliary drive system, improving fuel efficiency. This dynamic switching resolves the contradiction between power transfer capability and energy efficiency.
Solution Approach 2:
The invention uses hydraulic actuation to control the multi-plate clutch engagement. Hydraulic pressure enables the clutch plates to engage and transfer torque when needed, while release of pressure allows the clutch to disengage for fuel-efficient idling. This hydraulic control mechanism resolves the contradiction between maintaining torque transfer capability and achieving fuel efficiency.
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 minimizes driveline losses and enhances fuel efficiency by allowing the auxiliary drive system to be completely idled, reducing energy consumption and improving operational efficiency when shifting from 4X4 to 4X2 mode.
Implementation Method 1
a hydraulically-actuated multi-plate clutch for all wheel drive, the rear axle, and a rear shaft assembly
Data Source
AI summary
A vehicle driveline (10) comprising a primary drive system including at least one primary drive wheel (28) and an auxiliary drive system including at least one auxiliary drive wheel (46) is disclosed. The vehicle driveline (10) may further comprise a system for idling the auxiliary drive system. The system may include at least one wheel disconnect device (50) for selectively connecting and disconnecting the auxiliary drive wheel (46) from the auxiliary drive system and a power transfer unit (20) for selectively engaging and disengaging the auxiliary drive system from the primary drive system. The power transfer unit (20) may include a multi-plate clutch (34) in series with a dog clutch.