CV Joint Boot Shoulder Structure for High-Angle Durability
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Solution Overview
Problem
Existing boots for constant velocity universal joints face durability and fatigue issues when operating at high angles, particularly exceeding 50 degrees, due to increased stress, interference, and reduced film length, which limits their ability to support quick vehicle turns and expanded cabin space demands.
Innovation Solution
A boot design featuring two small crest portions on the large-diameter side to prevent interference, extended film length on the tension side to alleviate tensile stress, and increased curvature radii of crest and trough portions closest to the small-diameter-side mounting portion to reduce stiffness and stress, along with a cylindrical shoulder portion that deforms to promote overlapping crest portions, ensuring durability and fatigue resistance at super high operating angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tapered shoulder portion is used to improve folded shape and reduce contact stress, then durability is improved, but the film length is reduced and tensile stress on trough portions is increased
Solution Approach 1:
The invention changes the geometric parameters of the shoulder portion from a tapered shape to a cylindrical shape with a diameter equal to or larger than the large-diameter-side mounting portion. This parameter change increases the film length and reduces tensile stress on trough portions while maintaining durability through the cylindrical configuration that prevents radial protrusion during bending.
2Reliability
If the boot size is increased in axial direction to accommodate high operating angles, then durability is improved, but mounting position is shifted and clearance with peripheral devices is reduced
Solution Approach 1:
The invention changes the shoulder portion diameter parameter to be equal to or larger than the large-diameter-side mounting portion, which allows the boot to achieve high operating angle durability without increasing the axial length. The cylindrical shoulder portion configuration enables the boot to accommodate high operating angles within the existing spatial constraints.
3Reliability
If crest portions are formed on shoulder portion to suppress protruding deformation, then fatigue is reduced and durability is improved, but device complexity is increased
Solution Approach 1:
The invention extracts the crest portions from the shoulder portion, simplifying the structure to a smooth cylindrical shape. The durability function previously achieved by crest portions is replaced by the cylindrical configuration itself, which prevents radial protrusion through its geometric form rather than through surface features.
4Duration of action of moving object
If a cylindrical shoulder portion is used to increase film length and reduce tensile stress, then fatigue resistance is improved, but interference with clamp ear portion may occur at high operating angles
Solution Approach 1:
The invention optimizes the cylindrical shoulder portion diameter to be equal to or larger than the large-diameter-side mounting portion, which creates a specific geometric relationship that prevents interference with the clamp ear portion. This parameter optimization ensures that the boot deforms in a controlled manner at high operating angles without the cylindrical portion interfering with surrounding components.
Data Source
Figure 1
Figure 2a
Figure 2b~2c
AI summary
Provided is a boot (1) for a constant velocity universal joint, including: a large-diameter-side mounting portion (4), which is to be mounted on an outer peripheral surface of an outer joint member (32) of a constant velocity universal joint (31), and is to be fixed to the outer peripheral surface of the outer joint member (32) through fastening with use of a boot clamp (5); a small-diameter-side mounting portion (6), which is to be mounted on an outer peripheral surface of a shaft (46), and is to be fixed to the outer peripheral surface of the shaft (46) through fastening with use of a boot clamp (5'); a bellows portion (3) configured to integrally couple the large-diameter-side mounting portion (4) and the small-diameter-side mounting portion (6) to each other; and a cylindrical shoulder portion (2), which is formed at a bellows portion-side end of the large-diameter-side mounting portion (4), and is connected to the bellows portion (3) through two auxiliary crest portions (3c) and one auxiliary trough portion (3d) between the auxiliary crest portions (3c), wherein a radial distance (H1) between each of the auxiliary crest portions (3c) and the auxiliary trough portion (3d) is set shorter than a radial distance (H2) between a crest portion (3a) and a trough portion (3b) of the bellows portion (3), wherein a diameter (D1) passing through a center (Ho) of the radial distance (H1) between each of the auxiliary crest portions (3c) and the auxiliary trough portion (3d) is set larger than a diameter (D3) of the cylindrical shoulder portion (2), and wherein the boot (1) has such a deformation mode that, when the constant velocity universal joint (31) forms a high operating angle, the auxiliary crest portions (3c) overlap each other in a radial direction on the outer peripheral surface of the outer joint member (32).