Axle Assembly Layout for Low-Speed Differential Clutch Locking
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Solution Overview
Problem
Electric vehicles with axle assemblies face increased engagement forces and lash due to the inclusion of differentials at final drive speeds, leading to higher rotary speeds and potential noise, wear, and the need for larger clutches to handle these speeds.
Innovation Solution
An axle assembly design incorporating two gear reduction stages, an open differential, and a clutch positioned downstream of the second gear reduction stage, allowing for differential output shafts to rotate at different rates and the clutch to selectively lock or permit relative rotation between side shafts, reducing lash and engagement energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a differential is included at final drive speed, then torque distribution to wheels is enabled, but rotary speed increases leading to higher lash and engagement forces
Solution Approach 1:
The transmission system is divided into two separate gear reduction stages: a first stage reducing speed from motor output to intermediate levels, and a second stage further reducing speed to final drive levels. The differential is positioned between these stages, allowing it to operate at the lower intermediate speed rather than full motor speed, thereby reducing lash and engagement forces while maintaining torque distribution functionality.
Solution Approach 2:
An intermediate speed stage is introduced between the motor and the differential. This intermediate stage acts as a mediator that reduces the speed transmitted to the differential, allowing the differential to operate at reduced speeds with correspondingly reduced lash and engagement forces while still performing its torque distribution function.
2Reliability
If clutch engagement occurs at high rotary speeds, then wheel locking capability is achieved, but engagement energy and noise increase
Solution Approach 1:
The speed reduction is segmented into two stages, with the clutch positioned after the second stage. This allows the clutch to engage at the lower final drive speed rather than high motor speed, significantly reducing engagement energy and noise while maintaining the wheel locking capability when needed.
Solution Approach 2:
The operating speed parameter for the clutch is changed from high motor speed to lower final drive speed through the two-stage reduction. This parameter change reduces the kinetic energy that must be managed during clutch engagement, thereby reducing engagement energy consumption and noise while preserving the clutch's wheel locking function.
3Device complexity
If single stage gear reduction is used, then device complexity is reduced, but clutch must handle higher speeds increasing wear
Solution Approach 1:
The gear reduction is segmented into two stages with the clutch positioned after the second stage. Although this adds a gear stage, it significantly reduces the speed at which the clutch operates, thereby reducing wear and improving durability. The segmentation allows the clutch to handle lower speeds with correspondingly lower wear rates.
Solution Approach 2:
The additional gear stage, while increasing complexity, converts the harmful effect of high-speed clutch operation into a benefit by reducing clutch speed and wear. The extra reduction stage acts as a protective element that extends clutch life by operating it in a lower, less stressful speed regime.
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 minimizes lash, noise, and engagement energy by optimizing clutch operation at lower speeds, enabling efficient torque distribution and reduced wear, while allowing for differential rotation and selective locking of wheels.
Implementation Method 1
The clutch is a friction clutch or a dog clutch... the clutch is a friction clutch that includes limited slip capability
Data Source
AI summary
An axle assembly includes a gear train having multiple outputs that rotate at different speeds. A differential is engaged with a first output at a first speed, and a clutch is engaged with a second output at a second speed, and the second speed is lower than the first speed. The first output may be radially spaced from the second output, relative to axes of rotation of the differential and the clutch.