Modular Power Transfer Unit for Vehicle Drive Mode Transition
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Solution Overview
Problem
Existing power transfer units in vehicles are inefficient in transitioning between two-wheel drive and four-wheel drive modes, leading to a full-time fuel drain with limited part-time benefits, and lack a low range drive ratio for off-road conditions due to conventional transmission designs.
Innovation Solution
A modular power transfer unit with integrated mode selection and range selection assemblies, featuring a two-stage, two-speed gear assembly and a differential that provides gear ratios from 1:1 to 4.3:1, allowing for efficient torque transfer and mode shifting between two-wheel drive, all-wheel drive, and four-wheel drive modes, reducing stress on components and improving fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power transfer unit is kept in a ready state for all-wheel drive, then traction capability is improved, but fuel efficiency deteriorates due to full-time energy drain
Solution Approach 1:
The power transfer unit transitions from a static ready state to a dynamic on-demand engagement system. The clutch assembly selectively engages and disengages the power transfer unit based on detected wheel slip conditions, allowing the system to adapt between two-wheel drive and all-wheel drive modes rather than remaining permanently engaged.
Solution Approach 2:
The system uses the vehicle's existing wheel slip detection capability to automatically trigger power transfer unit engagement only when needed. The control system monitors wheel rotation speeds and autonomously activates the clutch assembly to engage the power transfer unit, eliminating the need for driver intervention or continuous system operation.
2Device complexity
If conventional transmission design is used without additional gear reduction, then device complexity is reduced, but adaptability deteriorates due to inability to provide low range drive ratio
Solution Approach 1:
The drivetrain is divided into separate functional modules: the conventional transmission handles high-range gear selection, while the independently controlled power transfer unit with clutch assembly provides low-range reduction and all-wheel drive capability. This segmentation allows each module to be optimized for its specific function without increasing overall system complexity.
Solution Approach 2:
The patent combines the power transfer unit with differential assembly into an integrated unit that provides both speed reduction and wheel-independent torque distribution. This merging of functions into a single compact assembly delivers low-range capability and four-wheel drive functionality without requiring separate complex mechanisms.
3Volume of moving object
If a compact power transfer unit is designed, then packaging requirements are improved, but device complexity increases due to integrated differential and shaft inputs
Solution Approach 1:
The differential assembly is nested within the power transfer unit housing, and the clutch assembly is integrated into the same structure. Multiple functional components (gear reduction, differential, clutch mechanism) are arranged concentrically and spatially optimized to share common mounting structures and lubrication systems, achieving compact packaging despite the complexity of integrated functions.
Data Source
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Figure 3A
AI summary
A power transfer unit assembly for a vehicle. The power transfer unit includes a housing, an internal variable speed differential positioned within the housing, a first front side shaft rotatively connected to the differential, a second front side shaft rotatively connected to the differential, an input shaft interconnected to at least one of the first and second side shafts, and at least one shifting mechanism for engaging at least one of the first and second shafts with at least one mode selection gear set. Engagement of the mode selection gear set transfers torque through the input shaft to selectively engage with a second gear set interconnected to a power transfer final drive unit assembly having an internal variable speed differential.