Externally Pumped Limited Slip Differential
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Solution Overview
Problem
Current limited slip differentials with internal pumps face packaging issues and increased parasitic drag, negatively impacting fuel efficiency due to larger assembly size and additional components.
Innovation Solution
A hydraulically locking limited slip differential design with an externally located fluid pump and a reduced high-pressure dynamic seal interface diameter, minimizing the span between support bearings and reducing parasitic losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an internal pump is used in the limited slip differential, then the clutch can be hydraulically engaged, but the assembly size increases causing packaging issues
Solution Approach 1:
The pump is extracted from the internal differential assembly and relocated to an external position. This removes the pump's volume from the LSD assembly, directly resolving the packaging issue while maintaining the hydraulic clutch engagement capability through external fluid supply.
2Reliability
If additional pump and clutch-pack components are added, then hydraulic locking capability is achieved, but parasitic drag increases reducing fuel efficiency
Solution Approach 1:
By extracting the pump from the rotating differential assembly and positioning it externally on the housing, the patent eliminates the parasitic drag that would be generated by an internally mounted pump. The external pump does not rotate with the differential, thereby reducing energy losses and improving fuel efficiency while maintaining hydraulic locking capability.
3Power
If the pump is located internally in the differential housing, then fluid pressure can be applied to the clutch, but the span between carrier support bearings increases
Solution Approach 1:
The pump is extracted from the internal differential assembly and repositioned externally on the housing. This relocation allows the carrier support bearings to be positioned closer together, reducing the span between them and improving packaging compactness, while the external pump continues to supply fluid pressure to the clutch through the housing.
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 design results in a more compact LSD assembly with reduced parasitic losses, enhancing fuel efficiency and addressing packaging challenges.
Implementation Method 1
The pump is in fluid communication with the pressure chamber via a fluid pathway and is arranged for selectively engaging the clutch via fluid pressure applied in response to signals received from an externally located controller
Implementation Method 2
A high-pressure dynamic seal may be required at the interface between the rotating differential carrier and the stationary pump. Typically, high-pressure dynamic seals generate considerable rotating friction which results in parasitic losses and reduced vehicle fuel efficiency
Data Source
AI summary
An improved hydraulically locking limited slip differential assembly for a drivetrain of a motor vehicle having a fluid pump external to a differential carrier and arranged for preventing slip between the wheels by selectively pressurizing a differential clutch internal to the carrier, and a controller arranged for selectively activating the fluid pump.