Abstract
Keywords - Squeal, Disk Brake, Low frequency, Stiffness, Stability analysis
Abstract - In these days, not only braking performance but also comfort of passengers is required for the brake system of automobiles. Squeal noise of a disk brake system is one of the major problems for comfort. Squeal has wide frequency range (1-10 kHz), especially the low frequency squeal (1.8-2.5 kHz), which is the coupled vibration between rotor and caliper through brake pads, and strongly focused today. Practically, low frequency squeal is restrained by changing stiffness of the brake system (ex. support of carrier), but the details of the squeal have not been discussed theoretically. So the objective of this study is to investigate the mechanism of low frequency squeal and to inspect the influence of changing stiffness and the moment of inertia of the brake system by simulation.
In this paper, disk brake is modeled as a two-degree-of-freedom model, because it is effective to use the reduced order model to analyze a fundamental behavior of a complicated system.
Rotor is assumed to be fixed, brake pads are modeled as contact springs and carrier has two degree of freedom of rotation and in perpendicular direction to rotor. Response analysis and stability analysis by Hurwitz stability criterion were conducted for normal disk brake system. The system becomes unstable and the squeal (self-excitation vibration) occurs when the coefficient of friction between pads and rotor is relatively high. This result is quite reasonable as it shows the property of the brake model.
Further simulations had been conducted using this model. It was clarified that the higher the coefficient of friction between rotor and pads becomes, the easier the squeal occurs. Also it was shown that it is possible to restrain the low frequency squeal by changing stiffness or moment of inertia of caliper, especially when the stiffness of trailing side is bigger than leading side, the system always becomes stable.
The future studies are a comparison between experimental and computational results and a developing of a minute model of the disk brake using the frictional vibration model from this study.