Brake Judder Analysis of Vehicle Disc Brakes
Date Issued
2007
Date
2007
Author(s)
Hsueh, Jen-Chun
DOI
zh-TW
Abstract
This study analyzes causes of the brake judder, the forced vibration of the fore brake system and the front chassis system to the vibratory response of the brake judder and the effect of design parameters on the brake judder. Elastic contact equations are derived by using the two-dimensional contact surface between the brake pad and the brake disc. An elastic contact model is built, and the surface pressure distribution, the surface deformation, the deformational friction and the brake torque are obtained when the sliding contact occurs between the brake pad and the brake disc. The effects of the brake disc surface wave amplitude and design parameters of the fore brake system on the brake torque variation are analyzed. The brake torque variation increases when the brake disc surface wave amplitude or the disc thickness variation increases. The brake torque variation is quite sensitive to design parameters of the brake system. If the modulus of elasticity of the brake disc increases 10 percent, the brake torque variation decreases about 10 percent.
Dynamic machnical software ADAMS is used to build a dynamic model of the front chassis system including brakes.The frequency response of the vehicle caused by the brake torque variation is analyzed. The results show that the front chassis system has significant frequency response when it is subjected to forced vibration with frequencies of 22.6 Hz and 38.2 Hz. The effects of the bushing stiffness, the damping coefficients and mass of the component in the front chassis system on the frequency response are analyzed. It shows that the bushing stiffness and the damping coefficient of components in the front chassis system has significant effect on the vibratory response, especially the stiffness and damping coefficient in the x direction of the aft bushing connected by the lower control arm and the vehicle body. If the stiffness of the bushing in x direction becomes twice of the original value, the frequency response of the vehicle body and the steering wheel shifts from 22.6 Hz to 29 Hz. The correspond vehicle speed increase from 21.8m/s (78.4 km/hr) to 28 m/s (100.6 km/hr), that is higher than the common vehicle driving speed. If the damping coefficient of the bushing in x direction becomes twice of the original value the vibratory acceleration amplitude decreases from 2.4 mm/s2 to 1.6 mm/s2. Hence, the brake judder can be improved by varing bushing parameters.
Subjects
碟式煞車
煞車抖顫
煞車碟盤厚度變動
彈性接觸
振動
disc brake
brake judder
disc thickness variation
elastic contact
vibration
Type
thesis