CV Joint Boot Lip Structure for Bearing Sealing and Low Drag
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Solution Overview
Problem
Conventional constant velocity joints face issues with foreign substances entering the bearing assembly, leading to abnormal noise, shaking, and increased bearing drag torque, which affects the vehicle's performance and fuel efficiency.
Innovation Solution
A constant velocity joint design featuring a boot with a protruding lip that prevents foreign substances from entering the bearing assembly by creating a labyrinthine path, combined with a reduced bearing seal overlap to minimize drag torque, includes a hub housing with a forming portion to apply pre-load to the inner race and a boot seat with a thickness of 5 mm or more to enhance rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bearing seal overlap amount is increased to prevent foreign substances from entering the bearing assembly, then sealing effectiveness is improved, but bearing drag torque is increased
Solution Approach 1:
The sealing function is divided into two independent parts: the bearing seal for sealing the bearing assembly and the boot lip for blocking foreign substances at the boot-knuckle interface. This segmentation allows each sealing component to be optimized independently, enabling the bearing seal to have minimal overlap (reducing drag torque) while the boot lip provides the necessary foreign substance blocking capability.
Solution Approach 2:
The boot lip acts as an intermediary element between the boot and the knuckle, creating a labyrinthine path that blocks foreign substances from reaching the bearing assembly. This intermediary structure provides the sealing function without requiring increased bearing seal overlap, thus maintaining low drag torque while achieving effective sealing.
2Reliability
If the distance between the outer race of the constant velocity joint and the knuckle is minimized to prevent foreign substances from entering, then sealing effectiveness is improved, but the risk of foreign substances entering through the bearing seal increases
Solution Approach 1:
Instead of relying solely on minimizing the axial distance between the outer race and knuckle, the solution adds a radial dimension of protection through the boot lip that protrudes toward the knuckle. This creates a multi-dimensional sealing approach where the boot lip blocks foreign substances radially before they can reach the bearing assembly, eliminating the need to minimize the axial distance and reducing the risk of foreign substance intrusion.
3Object-affected harmful factors
If a lip of the bearing seal is overlapped by a maximum amount to seal the bearing assembly, then foreign substance blocking is improved, but bearing drag torque is increased
Solution Approach 1:
The foreign substance blocking function is extracted from the bearing seal and transferred to the boot lip. The bearing seal is designed with minimal overlap to reduce drag torque, while the boot lip protrudes toward the knuckle to provide the foreign substance blocking capability. This extraction allows the bearing seal to focus solely on sealing without the burden of excessive overlap.
4Reliability
If the boot lip protrudes toward the knuckle to prevent foreign substances from entering the bearing assembly, then sealing effectiveness is improved, but the complexity of the boot structure is increased
Solution Approach 1:
The boot structure maintains simplicity in most areas but introduces a localized feature - the boot lip - that protrudes toward the knuckle at the critical interface where foreign substance blocking is needed. This local modification provides enhanced sealing effectiveness without requiring complex structural changes throughout the entire boot, thus minimizing the increase in overall device complexity.
Data Source
AI summary
A constant velocity joint for a vehicle is provided and may include hub housing, a bearing assembly, a power transmission member, and a boot. The hub housing is combined with the constant velocity joint in the hub housing. The bearing assembly includes an inner race fitted on an outer surface of the hub housing, an outer race spaced a predetermined distance apart from the inner race and fitted on a knuckle. The power transmission member is disposed between the inner race and the outer race. The boot has a band seat positioned on the inner race and a fixing band fixed on a top of the boot and the boot is coupled to the inner race by the fixing band. The boot further includes a boot lip that is formed at one end or both ends of the band seat and protrudes toward the knuckle.