Hydraulically Actuated Power Transfer Unit Fluid Integration
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Solution Overview
Problem
Conventional all-wheel drive drivetrains have separate fluid management systems for the transaxle and power transfer unit, leading to complexity and inefficiency due to the use of different lubricants and actuation methods.
Innovation Solution
A power transfer unit that utilizes hydraulic fluid from a transmission pump to actuate and lubricate clutches within the power transfer unit, allowing for seamless integration with the transaxle and enabling efficient power distribution to all wheels while maintaining a shared fluid management system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate fluid management systems are used for transaxle and power transfer unit, then each system can be optimized for its specific lubricant requirements, but the overall system complexity increases and efficiency decreases
Solution Approach 1:
The patent combines the transaxle and power transfer unit into a single integrated assembly that shares a common fluid management system. The housing contains both the transaxle and power transfer unit, allowing them to use the same lubricant (gear oil) and hydraulic fluid circulation system, thereby reducing overall system complexity while maintaining reliability through proper lubrication of all components.
Solution Approach 2:
The common fluid management system serves multiple functions: it provides lubrication for both the transaxle gears and the power transfer unit gears, and it supplies hydraulic fluid for actuating clutches in both systems. This multi-functional approach eliminates the need for separate fluid reservoirs, pumps, and filtration systems, reducing complexity while ensuring proper lubrication.
2Reliability
If different lubricants are used for transaxle and power transfer unit, then each component is properly lubricated, but the actuation and fluid management systems become separate and more complex
Solution Approach 1:
The patent merges the actuation systems of the transaxle and power transfer unit by using a common hydraulic fluid supply from a single reservoir. Both the transaxle clutch and power transfer unit clutch are actuated by hydraulic pressure from the same fluid source, eliminating the need for separate actuation systems and reducing overall complexity while ensuring reliable clutch engagement.
3Device complexity
If integrated fluid management system is used, then system complexity is reduced and efficiency is improved, but the viscosity compatibility between hydraulic fluid and gear oil must be maintained
Solution Approach 1:
The patent applies local quality by providing different fluid characteristics to different regions of the integrated system. The gear oil provides high viscosity lubrication for gear contacts in both the transaxle and power transfer unit, while the hydraulic fluid (with lower viscosity) provides actuation pressure for the clutches. The system design ensures that each component receives the appropriate fluid properties needed for its specific function.
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
Simplifies the fluid management system, enhances power transfer efficiency, and improves vehicle performance on various road conditions by integrating hydraulic fluid circulation for both actuation and lubrication within the power transfer unit.
Implementation Method 1
a transmission having a pump for circulating hydraulic fluid from a sump
Implementation Method 2
The first clutch and the second clutch are each hydraulically actuated using the hydraulic fluid from the pump
Implementation Method 3
the power transfer unit is lubricated by gear oil that has a much higher viscosity than conventional hydraulic fluid
Data Source
AI summary
A power transfer unit for an all-wheel drive drivetrain that includes an engine, a transmission having a pump for circulating hydraulic fluid from a sump, and a driveshaft. The power transfer unit includes an input for receiving driving power from the transmission, an output for delivering driving power to the driveshaft, a first clutch, a first fluid supply path for delivering the hydraulic fluid from the pump to the first clutch, and a fluid return path for returning the hydraulic fluid from the power transfer unit to the sump of the transmission.