Drive Axle Boot Assembly for Low-Drag Bearing Sealing
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Solution Overview
Problem
The integration of the wheel bearing and driveshaft in an integrated drive axle increases drag torque, affecting vehicle fuel efficiency, and the conventional bearing internal seal allows foreign substances to enter, causing friction noise.
Innovation Solution
A drive axle assembly design that eliminates the bearing internal seal by using a boot assembly to cover the space between the external and internal rings, preventing rotation of the boot and incorporating a separable shaft assembly with a dust cover and bearing seal unit to block foreign substances, while maintaining lubrication performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bearing internal seal is used to prevent foreign substances from entering the wheel bearing, then sealability is improved, but drag torque increases
Solution Approach 1:
The patent removes the bearing internal seal from the wheel bearing assembly and replaces it with a boot assembly that covers the external ring. This extraction eliminates the source of high drag torque while maintaining protection against foreign substances through the boot's sealing function
Solution Approach 2:
The boot assembly serves as an intermediary component that provides both sealing protection and rotational freedom. It mediates between the need for sealability and the need to reduce drag torque by allowing the boot to rotate with the driveshaft rather than using a fixed internal seal
2Reliability
If the boot is fixed to prevent rotation, then foreign substance introduction is prevented, but friction noise increases due to fold contact
Solution Approach 1:
The boot assembly is designed to rotate dynamically with the driveshaft rather than being fixed. This dynamic adaptation allows the boot to maintain its sealing function while avoiding the friction noise that would occur from stationary folds contacting the road surface during steering movements
3Weight of moving object
If the wheel bearing and driveshaft are integrated, then weight and cost are reduced, but drag torque increases
Solution Approach 1:
The patent extracts the bearing internal seal from the integrated wheel bearing-driveshaft assembly, eliminating the primary source of drag torque while preserving the weight and cost benefits of the integrated structure
Solution Approach 2:
The boot assembly acts as a flexible shell that replaces the rigid internal seal, providing protection against foreign substances while allowing rotational movement that reduces friction and drag torque in the integrated drive axle system
Data Source
AI summary
A drive axle assembly includes a wheel bearing mounted to an axle housing, a shaft assembly including a first shaft on an inboard side thereof to which a driving force of a power train is transmitted, and a second shaft on an outboard side thereof which is shaft-connected to the inside of the axle housing by a constant-velocity joint and is separably assembled to the first shaft, and a boot assembly including a first end portion fixed to an external ring of the wheel bearing and a second end portion assembled to the shaft assembly to be rotatable relative to the shaft assembly, and configured to restrict rotation of the boot and prevent foreign substances from being introduced therein.