Disc Brake Bellows Geometry for Stable Long Stroke Sealing
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Solution Overview
Problem
Bellows in disc brakes face instability and deformation during extension, leading to leaks and premature wear due to limited installation space, causing frictional contact and abrasion with adjacent components, which results in reduced service life and increased maintenance costs.
Innovation Solution
A rotationally symmetrical bellows design with a first and second end ring and multiple folds, where the second end ring is axially spaced from the first end ring, maintaining a circular contour even when stretched, preventing lateral deflection and minimizing stretching forces, thus ensuring stability and reducing frictional contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the bellows is stretched to compensate for great movement travel (>50 mm), then the stroke capability is improved, but the flanks become unstable and deviate from circular shape
Solution Approach 1:
The bellows is designed with a circular cross-section contour that is maintained throughout its extension range. The folds are configured with specific curvature radii and flank angles that prevent buckling and polygonal deformation even when stretched to compensate for brake pad wear, ensuring the circular shape is preserved during the entire stroke movement.
2Length of moving object
If the height of the flanks is increased to achieve desired stroke, then the stroke capability is improved, but the flanks become unstable and buckle during extension
Solution Approach 1:
The bellows design optimizes specific geometric parameters including the height of the folds, the radius of curvature at the bends, and the angle of the flanks. These parameters are carefully selected to provide sufficient stroke capability while preventing buckling and maintaining structural stability during extension, avoiding the polygonal deformation that occurs with conventional designs.
3Length of moving object
If the bellows extends during braking operations, then the adjustment travel is achieved, but frictional contact with adjacent components occurs causing wear
Solution Approach 1:
Instead of allowing the bellows to extend outward and contact adjacent components, the design inverts the approach by configuring the folds and flanks to maintain a compact circular profile during extension. This prevents the bellows from buckling outward and contacting the brake caliper or other components, thereby eliminating frictional wear while still achieving the required adjustment travel.
Data Source
AI summary
A rotationally symmetrical bellows has a first end ring and a second end ring with a smaller diameter, and multiple folds, which in a relaxed position each have two flanks running in opposite directions with respect to one another while forming a bend. The flanks extend approximately parallel to an axis of rotation of the bellows. The rotationally symmetrical bellows is designed such that in a relaxed position of the bellows, the second end ring is arranged at an axial distance to the first end ring.