Brake Pad Slot Layout to Reduce Low-Frequency Brake Whistle
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Solution Overview
Problem
Existing brake pads and caliper assemblies in disc brakes for vehicles tend to generate mechanical vibrations during braking, leading to undesirable whistle-like noises at low frequencies.
Innovation Solution
The brake pad design features strategically positioned first and second slots for accommodating pins, with the first slot radially outer and the second slot radially inner with respect to the pad's barycenter, which reduces vibrational frequencies that cause whistling phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the eyelets are positioned on a circumference centered on the disc rotation axis having a radius equal to the distance between the disc axis and the barycenter of the pad, then the braking force transmission is optimized and detachment between pin and pad is avoided, but mechanical vibrations and whistling phenomena occur during braking
Solution Approach 1:
The patent applies asymmetry by positioning the eyelets at different radial distances from the disc rotation axis, rather than symmetrically on the same circumference. Specifically, the first eyelet is positioned at a first radial distance while the second eyelet is positioned at a second radial distance that is different from the first, breaking the rotational symmetry that causes resonant vibrations. This asymmetric configuration disrupts the natural vibration modes of the pad-caliper-disc system, thereby eliminating the whistling phenomena while maintaining effective braking force transmission.
Solution Approach 2:
The patent changes the positional parameters of the eyelets from a symmetric configuration (both eyelets on the same circumference) to an asymmetric configuration (eyelets at different radial distances). By varying the radial distance parameter for each eyelet independently, the system alters the vibration characteristics of the braking assembly, shifting the natural frequencies away from the excitation frequencies that cause whistling, thus resolving the harmful vibration issue.
2Force
If the pads are supported by pins with clearance eyelets to allow sliding during braking, then the pads can transmit braking force effectively, but mechanical vibrations are promoted between pads, pins, caliper body and disc
Solution Approach 1:
The asymmetric positioning of eyelets at different radial distances creates an uneven distribution of forces and moments during braking, which disrupts the synchronous vibration patterns that occur with symmetric positioning. This asymmetry in the support configuration reduces the coupling between pad vibrations and caliper-disc vibrations, thereby improving vibration stability while preserving braking force transmission capability.
Solution Approach 2:
The pins with clearance eyelets act as intermediaries that allow relative motion between the pad and caliper body. By positioning the eyelets asymmetrically, the patent modifies how these intermediary pins transmit forces and accommodate movements, reducing the direct transmission of vibrations from the pad to the caliper and disc, thus improving overall vibration stability.
Data Source
AI summary
A brake pad may have at least one plate and at least one friction material supported by the plate. The friction material surface may have a barycenter. The plate may have a first slot and a second slot. The first slot may have a first slot edge adapted to accommodate a first pin mounted on the caliper body. The second slot may have a second slot edge adapted to accommodate a second pin mounted on the caliper body. In a forward braking condition, the brake pad rests on the first pin with a first slot first portion, and the brake pad rests on the second pin with a second slot first portion. The first slot is arranged in a radially outer position with respect to the barycenter and the second slot is arranged in a radially inner position with respect to the barycenter. The first slot and the second slot may be radially external with respect to a barycenter circumference centered on a rotation axis and passing through a barycenter.