Differential Disconnect System Isolating Thrust Loads
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Solution Overview
Problem
Four-wheel and all-wheel drive vehicles experience parasitic drag due to back-driving of secondary driveline components, which increases fuel consumption despite efforts to disconnect the secondary differential, as existing solutions like dog clutches introduce frictional drag from thrust loads.
Innovation Solution
A differential disconnect system with an output gear and translatable collar that allows selective connection and disconnection of the wheel-side and differential-side shafts, using an electric motor for actuation, and employing needle and ball bearings to minimize frictional drag by isolating thrust loads from the output gear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a dog clutch is used to disconnect the secondary differential from the axle-shaft, then the mechanical interference is removed and back-driving is prevented, but the wheel-side shaft must be supported by a thrust bearing which creates considerable frictional drag
Solution Approach 1:
The invention extracts the thrust bearing function from the wheel-side shaft support system. By relocating thrust load support to the differential-side shaft through the translatable collar mechanism, the wheel-side shaft can use low-friction needle bearings only, eliminating the energy loss associated with thrust bearing friction while maintaining the ability to prevent back-driving.
Solution Approach 2:
The translatable collar acts as an intermediary element between the wheel-side shaft and differential-side shaft. It transfers thrust loads from the wheel-side shaft to the differential-side shaft, enabling the wheel-side shaft to be supported by low-friction bearings while still maintaining structural integrity and load-bearing capability during both connected and disconnected states.
2Reliability
If secondary driveline components are permanently installed to provide four-wheel or all-wheel drive capability, then enhanced tractive capabilities are achieved, but additional mass and friction increase fuel consumption
Solution Approach 1:
The invention implements a dynamic disconnect mechanism that allows the secondary driveline to transition between connected and disconnected states. The translatable collar can be actuated to engage or disengage the differential from the axle-shaft, enabling the system to adapt its configuration based on driving conditions - providing four-wheel drive when needed and reducing frictional losses when two-wheel drive is sufficient.
3Power
If the collar is translated to connect the wheel-side shaft and differential-side shaft, then torque transmission is enabled, but axial loads are imposed on the output gear
Solution Approach 1:
The invention segments the driveline into distinct components (wheel-side shaft, output gear, translatable collar, differential-side shaft) with clearly defined functional boundaries. The translatable collar is positioned to engage splines on both the wheel-side shaft and differential-side shaft, creating a modular connection system where axial loads are isolated to specific components rather than being distributed to the output gear.
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 system reduces driveline friction and improves fuel efficiency by minimizing axial loads on the output gear, allowing for efficient torque transmission and disconnection of the drivetrain components.
Implementation Method 1
The wheel-side shaft may be fixed to a wheel hub and the wheel hub may be rotatably supported by a needle bearing at an interface of the wheel hub and the housing
Implementation Method 2
The output gear may be rotatably supported by a ball bearing at an interface of the output gear and the housing
Implementation Method 3
the differential-side shaft may be rotatably supported by a needle bearing positioned at an interface of the output gear and the differential-side shaft
Data Source
AI summary
An axle disconnect system for selectively connecting or disconnecting a wheel-side shaft and a differential-side shaft having a common axis of rotation in a drivetrain of a motor vehicle. In the axle disconnect an output gear is splined to the wheel-side shaft on an outside diameter of the wheel-side shaft, and a translatable collar is splined to the output gear on an outside diameter of the output gear. The collar is arranged to be translated along the common axis of rotation for splined connection with the differential-side shaft while retaining the splined connection with the output gear.