Constant-Velocity Joint Boot Mounting Structure Preventing Silicone Cracks
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Solution Overview
Problem
The silicone boots for constant velocity universal joints are prone to cracking due to interference with the band's folded-back portion and edge portions, which compromises their sealing performance, especially under high and low temperature conditions.
Innovation Solution
A no-interference structure is implemented by curving or bending the axial outer-peripheral-edge portion of the band to the radially-outer side, or forming a circumferential groove in the fitting groove, preventing interference between the band and the groove, thus avoiding cracks and maintaining stable sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a boot band with folded-back portion is used to fix the silicone boot, then the boot can be securely attached to the joint, but cracks occur in the silicone boot due to interference with the folded-back portion and edge portions
Solution Approach 1:
The band is designed with curved surfaces instead of sharp edges. The axial outer-peripheral-edge portions are curved to eliminate concentrated stress points that cause cracks in the silicone boot, while maintaining the clamping function for secure attachment.
Solution Approach 2:
Different portions of the band have different structural characteristics. The axial outer-peripheral-edge portions are specifically modified with curved surfaces to prevent interference with the silicone boot, while other portions maintain the necessary clamping strength for secure fixation.
2Reliability
If the band is decreased in diameter to clamp the boot, then secure fixation is achieved, but interference between the band edge portions and groove bottom causes cracks
Solution Approach 1:
The axial outer-peripheral-edge portions of the band are curved to eliminate concentrated stress points during the diameter reduction process. This prevents interference with the groove bottom and avoids cracking the silicone boot material while maintaining effective clamping force.
Solution Approach 2:
The curved edge portions are designed in advance to prevent stress concentration before the clamping action occurs. This proactive design prevents cracks from forming during the diameter reduction and clamping process.
3Temperature
If silicone material is used for the boot to withstand high and low temperatures, then temperature resistance is improved, but the material becomes more susceptible to cracking from band interference
Solution Approach 1:
The band's axial outer-peripheral-edge portions are curved to eliminate sharp corners that concentrate stress on the silicone material. This prevents crack initiation in the temperature-resistant silicone boot while maintaining its thermal performance characteristics.
Solution Approach 2:
The band structure is locally modified at the axial outer-peripheral-edge portions to have curved surfaces, while the rest of the band maintains its clamping functionality. This localized modification protects the silicone boot from cracking without compromising temperature resistance.
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
Provided are a boot-mounting structure for a constant velocity universal joint and a silicone boot for a constant velocity universal joint, which can prevent a crack caused by interference with a boot band while maintaining a stable sealing property. The boot band (69) is fitted into a fitting groove of a silicone boot (65), and is decreased in diameter while being attached into the fittinggroove, to thereby fix the silicone boot (65). The boot band (69) is formed into an annular body not provided with a folded-back portion. There is provided a no-interference structure means (S) for preventing interference caused, when the boot band is decreased in diameter, between an axial outer-peripheral-edge portion (69a or 69b) of the band (69) and a bottom end portion (82a or 82b) of the fitting groove (75) corresponding thereto.