車輛碟式煞車之煞車抖顫分析

Brake Judder Analysis of Vehicle Disc Brakes

薛任鈞(Jen-Chun Hsueh)

指導教授 ： 黃元茂

國立臺灣大學/工學院/機械工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.03120

摘要

本研究分析煞車抖顫現象的形成原因、前煞車系統的強迫振動與車輛前底盤系統對於此煞車抖顫的振動響應、與設計參數對煞車抖顫之影響。研究方法為將煞車蹄片與煞車碟盤之接觸面以二維接觸面推導彈性接觸方程式，建立煞車碟盤與煞車蹄片的彈性接觸模型，以求得煞車蹄片與煞車碟盤間滑動接觸所產生的表面壓力分布、表面應變、應變摩擦力與煞車扭矩。分析不同的煞車碟盤波面之振幅及前煞車系統設計參數對於煞車扭矩變動的影響，當煞車碟盤波面之振幅增大時，煞車扭矩變動亦會隨之增大，因此，若煞車碟盤厚度變動增大時，會產生較大的煞車扭矩變動。煞車扭矩變動對於煞車系統的設計參數相當的敏感，增加10 %的煞車碟盤彈性模數，可以減低約10 %的煞車扭矩變動。因此，改變前煞車系統設計參數可達到減低煞車扭矩變動的目的。
利用動態機構軟體ADAMS建立車輛前底盤系統的動態模型，分析煞車扭矩變動所造成之車輛頻率響應，結果顯示車輛前底盤系統於22.6 Hz 及38.2 Hz的強迫振動時有顯著的頻率響應。分析車輛前底盤系統中襯套之剛性與阻尼係數和底盤元件之質量對於車輛頻率響應的影響，得知車輛前底盤系統的襯套剛性與阻尼對於振動特性有極大的影響，尤其連結下控制臂與車身之後方襯套於x方向的剛性與阻尼係數。增加此襯套於x方向的剛性為原值的2倍時，會使得車身與方向盤的頻率響應由22.6 Hz提升為29 Hz，使得煞車抖顫發生的車速由21.8 m/s (78.4 km/hr)提升至28 m/s (100.6 km/hr)，高於一般車輛的行駛車速。增加此襯套於x方向的阻尼為原值的2倍時，會使得車身的加速度振幅由2.4 mm/s2減低至1.6 mm/s2，因此改變襯套參數可以改善車輛的煞車抖顫。

關鍵字

碟式煞車 ； 煞車抖顫 ； 煞車碟盤厚度變動 ； 彈性接觸 ； 振動

並列摘要

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.

並列關鍵字

disc brake ； brake judder ； disc thickness variation ； elastic contact ； vibration

參考文獻

[1] Jacobsson, H., 2003, “Aspects of Disc Brake Judder,”Proceedings IMECHE, 217, Part D: J. Automobile Engineering, pp.419- 430.

[2] Kubota, M., Suenaga, T., and Doi, K., 1998, “A Study of The Mechanism Causing High-Speed Brake Judder,” SAE, International Congress and Exposition, 980594, pp.1- 6.

[3] Donley, M. and Riesland, D., 2003, “Brake Groan Simulation for a McPherson Strut Type Suspension,” SAE, 2003 Noise and Vibration Conference and Exhibition, 2003-01-1627, pp.1- 9.

[5] de Vries, A., and Wagner, M., 1992, “The Brake Judder Phenomenon,” SAE Transactions, 101, Sect 6, 920554, pp.652-660.

[7] Hartsock, D. L., and Fash, J. W., 2000, “Effect of Pad/Caliper Stiffness, Pad Thickness, and Pad Length on Thermoelastic Instability in Disk Brakes,” Journal of Tribology, 122, pp.511-518.