Constant Velocity Universal Joint Boot Mounting Sealability
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Solution Overview
Problem
Existing constant velocity universal joints face sealability issues due to compressive stress relaxation and poor interference balance between boot components, leading to lubricant entry and increased working costs, with complex structures contributing to high costs and reduced operability.
Innovation Solution
A constant velocity universal joint design featuring a boot with a large-diameter and small-diameter mounting portion, connected by a bent portion, where the large-diameter portion has a circumferential band groove and a protruding portion that fits into a recessed portion on the outer joint member, and the small-diameter portion has a circumferential clamp groove and a projection that bites into the shaft, ensuring a stable close-contact area and reduced stress transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the boot mounting structure uses a simple clamp groove design, then the device complexity is reduced, but the sealability deteriorates due to compressive stress relaxation and poor interference balance
Solution Approach 1:
The boot mounting structure incorporates a projection at a specific location on the inner peripheral surface of the large-diameter mounting portion. This projection creates a localized interference fit with the boot, concentrating the sealing action at a critical position. The projection has optimized dimensions (height h1 and width w1) to provide sufficient interference pressure for sealing while maintaining overall structural simplicity.
Solution Approach 2:
The clamp groove is positioned at a predetermined location relative to the projection, allowing the fastening clamp to apply compressive force that pre-loads the boot against the projection. This preliminary action ensures that the boot is firmly held in the recessed portion before operation, preventing stress relaxation and maintaining sealability throughout the boot's service life.
2Reliability
If the projection and recessed portion provide strong interference fit, then the sealability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The projection dimensions (height h1 and width w1) are specifically designed to provide optimal interference fit. The height h1 is set to create sufficient radial interference pressure for sealing, while the width w1 is optimized to distribute the contact pressure. These parameter optimizations ensure reliable sealing performance while accommodating normal manufacturing tolerances without requiring excessive precision.
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
The present invention relates to a constant velocity universal joint in which a large-diameter mounting portion (80a) is fastened and fixed by a fastening clamp (82A (82B)) in a state of being externally fitted onto a boot receiving portion (85) of an outer joint member (55 (62)), and in which a small-diameter mounting portion (80b) is fastened and fixed by a fastening clamp (83A (83B)) in a state of being externally fitted onto a boot receiving portion (86) of a shaft (50). A circumferential clamp groove (90) to which the fastening clamp (82A (82B)) is fitted is formed in an outer peripheral surface of the large-diameter mounting portion (80a) A protruding portion (91) is formed at a boot outer side end portion of an inner peripheral surface of the large-diameter mounting portion (80a). A recessed portion (92) to which the protruding portion (91) of the large-diameter mounting portion (80a) is fitted is formed in the boot receiving portion (85) being a cylindrical surface of the outer joint member (55 (62)). A projection (93) is formed in the vicinity of a boot inner side of the recessed portion (92).