Power Transfer Unit Disconnecting Input Shaft
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Solution Overview
Problem
Existing power transfer units in front-wheel-drive based all-wheel-drive systems operate in a full-time ready state, leading to a significant drain on fuel efficiency, despite being used only part-time, which negatively impacts vehicle fuel efficiency without providing proportional benefits.
Innovation Solution
A power transfer unit assembly featuring a first input shaft and a second input shaft connected through a gear train and propshaft, with a selective engagement element that can be moved between engagement and disengagement positions, allowing for efficient disengagement in two-wheel drive mode and engagement in all-wheel drive mode, utilizing an actuator assembly to control the selective engagement element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power transfer unit operates in a full-time ready state, then the all-wheel drive system is always prepared for operation, but fuel efficiency deteriorates significantly
Solution Approach 1:
The power transfer unit transitions from a static full-time ready state to a dynamic state that can engage and disengage. The disconnecting input shaft allows the system to adapt its operational state based on driving conditions, being connected when all-wheel drive is needed and disconnected when front-wheel drive suffices, thereby resolving the contradiction between constant readiness and fuel efficiency.
Solution Approach 2:
The system alternates between engaged and disengaged states based on periodic assessment of driving conditions. The actuator assembly periodically activates to disconnect the second input shaft when all-wheel drive is not required, creating a rhythmic pattern of engagement that maintains readiness when needed while conserving energy during normal operation.
2Adaptability or versatility
If the power transfer unit is always engaged, then all-wheel drive capability is maintained, but fuel consumption increases
Solution Approach 1:
The power transfer unit is segmented into two separate input shafts: a first input shaft that remains continuously connected to the transmission, and a second input shaft that can be selectively disconnected. This segmentation allows the system to maintain all-wheel drive capability through the first input shaft while eliminating the energy loss associated with continuously engaging the second input shaft and its associated gear train.
3Use of energy by moving object
If a disconnecting mechanism is added to the power transfer unit, then fuel efficiency improves, but device complexity increases
Solution Approach 1:
An actuator assembly serves as an intermediary mechanism that automatically controls the engagement and disengagement of the second input shaft based on driving conditions. This intermediary component manages the complexity by providing automated control, eliminating the need for manual intervention while maintaining the fuel efficiency benefits of the disconnecting mechanism.
Data Source
AI summary
A power transfer unit assembly for a vehicle is provided comprising a first input shaft providing rotational drive. A second input shaft is in communication with a gear train assembly which is in communication with a propshaft. A selective engagement element is movable between an engagement position wherein the second input shaft is placed in rotational communication with the first input shaft and a disengagement position wherein the second input shaft is disengaged from the first input shaft. An actuator assembly moves the selective engagement element into the engagement position for all wheel drive mode and into the disengagement position for two wheel drive mode.