Asymmetric Hold-Down Spring for Disc Brake Preload
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Solution Overview
Problem
Conventional disc brakes for commercial vehicles experience loss of spring preload and material fatigue due to the second area of the spring legs lifting off in full-load conditions, leading to deformation and destruction, especially under extreme accelerations and frequent loading.
Innovation Solution
The hold-down spring is designed with a trough shape surrounding the hold-down bracket's rods, where the second areas of the spring legs form the trough's bottom, ensuring they remain in contact with the pressure device even in extreme conditions, and the trough is asymmetrical with a lower wall height on one side to allow for adequate movement and leverage, preventing shear and compressive stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second area of the spring legs is designed to contact the pressure device directly, then the spring preload is maintained, but the spring legs are subjected to excessive shear and compressive stresses leading to material fatigue
Solution Approach 1:
A lever arm is introduced as an intermediary element between the spring legs and the pressure device. The lever arm transfers the spring force from the first area (where it applies) to the second area (where it contacts the pressure device), converting direct shear and compressive stresses into bending moments. This mediator structure reduces stress concentrations and prevents material fatigue while maintaining reliable spring preload.
Solution Approach 2:
The design transitions from a direct radial contact arrangement to a lever arm configuration that extends in the circumferential direction. By adding this dimensional element, the force transmission path is lengthened and optimized, allowing the spring force to be applied more effectively while reducing harmful stress components on the spring legs.
2Ease of manufacture
If the hold-down spring is designed symmetrically, then installation errors are avoided, but the spring legs cannot accommodate extreme accelerations and full-load conditions
Solution Approach 1:
The hold-down spring is designed with asymmetric geometry, specifically with the lever arm extending preferentially in the direction of brake disc rotation. This asymmetric design allows the spring to better accommodate extreme accelerations and full-load conditions by optimizing the force distribution and leverage arms for the specific loading scenarios encountered during braking operations.
3Power
If the spring legs are positioned close to the pressure device, then the leverage is optimized, but the spring preload is lost when the second area lifts off in full-load conditions
Solution Approach 1:
The spring leg design incorporates a dynamic lever arm mechanism that allows the contact point with the pressure device to shift between the first area and the second area depending on loading conditions. This dynamic adaptation ensures that the spring preload is maintained through the lever arm's rotational movement, preventing lift-off and maintaining consistent leverage efficiency across varying load conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design maintains optimal damping and spring effect throughout the full-load range, preventing deformation and material fatigue, while allowing for adjustment and improved leverage for optimal performance.
Implementation Method 1
the inner elasticity of the spring, it is supported on the one hand in the grooves and on the other hand radially outwards on the tabs
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to a disc brake comprising a pressing device that is pressed against a brake disc in order to brake, a hold-down spring (30) in the form of a leaf spring that holds down the pressing device, and a hold-down bracket which comprises two rods (34, 36) and preloads said hold-down spring against the pressing device, said hold-down spring being designed to be symmetrical with respect to its transverse plane and comprising two spring legs and a central region between said two spring legs which extends radially outwards (form-fittingly) between the two rods of the hold-down bracket, the two spring legs each having an opening into which one projection in each case extends on the pressing device, said spring legs each comprising a first region on which one rod (34, 36) of the hold-down bracket lies so as to hold down same, and a second region (56, 58) which lies against the pressing device so as to hold down same, said first regions of the spring legs being held at a distance from the pressing device when in the resting state, and the spring legs initially extending radially outwards from the first region towards the second region.