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Disc brake squeal is caused by flutter of dynamic unstable systems under small disturbance. Therefore the research of small disturbance is very important technical issues for disc brake squeal reduction. The experimental set-up for basic research was developed based on the actual disc brake squeal vibration mode in experiment and its theoretical analysis, which replaces actual caliper and pads to cantilever type pad-caliper. Disc brake squeal depends on the natural frequency of cantilever type pad-caliper, which occurred at 2.7 kHz, 2.0 kHz and 5.3 kHz for each cantilever length L=40 mm, 50 mm and 80 mm in each friction test. In friction tests L=40 mm and 50 mm, cantilever type pad-caliper vibrates with the 1st order bending vibration mode and disc vibrates with the 1st or 2nd order bending vibration mode. In friction test L=80 mm, cantilever type pad-caliper vibrates with the 2nd order bending vibration mode and disc vibrates with the 4th order bending vibration mode.

It is well known that disc brake squeal is often caused by high friction coefficient pad materials. Disc brake squeal is caused by dynamic unstable system under small disturbance of friction force variation. Today, disc brake squeal comes to be simulated by FEA, but it is very difficult to put so many dynamic unstable solutions into stable solutions. Therefore it is very important to make it clear the influence of friction force variation. This paper describes a study on trigger of disc brake squeal generation. First, the development of experimental set-up for disc brake squeal basic research and experimental results are described. Second, the equation of motion in disc brake squeal is derived and the vibration induced by small disturbance are analyzed. Furthermore, kinetic energy increase per 1 cycle in minute vibration are calculated, which represents the influence of friction and wear between disc and pad with caliper.

The vehicle requires high brake performance and mass reduction of disc brake for vehicle fuel economy. Then disc brake will be designed by downsizing of disc and high friction coefficient pad materials. It is well known that disc brake squeal is frequently caused by high friction coefficient pad materials. Disc brake squeal is caused by dynamic unstable system under disturbance of friction force variation. Today, disc brake squeal comes to be simulated by FEA, but it is very difficult to put so many dynamic unstable solutions into stable solutions. Therefore it is very important to make it clear the influence of friction force variation. This paper describes the development of experimental set up for disc brake squeal basic research. First, the equation of motion in low-frequency disc brake squeal around 2 kHz is derived.

Many papers of brake noise research were presented before. Today it is required in brake design stage to predict the influences of countermeasure for every brake noise. For example, moan noise is sometimes caused by the countermeasure of low-frequency disc brake squeal. The countermeasure should be derived from the analysis for reducing both brake noises, but there is no paper of relationship research between each brake noise. This paper describes that moan noise is given by one of the dynamic instable solutions in low-frequency disc brake squeal, which is given by 4 degrees of freedom of caliper with suspension and brake disc. On the lower stiffness of caliper fixed on suspension, the vibration amplitude of disc is sufficiently small and the amplitude of disc is considered to be negligible. Then the equation of motion is reduced into 2 degrees of freedom, which gives the equation of motion in moan noise.