Design of Hydraulic Bushing and Vehicle Testing for Reducing the Judder Vibration

Youngman Kim,Sangjin Jeong,Heungseob Kim,Van-Quyet Nguyen,Kwangsuck Boo,J Detand,D Ruxu

doi:10.1051/matecconf/201816702012

Abstract

Generally, judder vibration is a low-frequency vibration phenomenon caused by a braking force imbalance that occurs when a vehicle is lightly decelerated within a range of 0.1 to 0.2g at a speed of 120 to 60 km/h. This comes from the change in the brake disk thickness (DTV), which is mainly caused by the side run-out (SRO) and thermal deformation. The adoption of hydro-bushing in the low arm G bushings of the vehicle front suspension has been done in order to provide great damping in a particular frequency range (<20Hz) in order to prevent this judder vibration from being transmitted to the body. The hydro bushing was formulated using a lumped parameter model. The fluid passage between the two chambers was modelled as a nonlinear element such as an orifice, and its important parameters (resistance, compliance) were measured using a simplified experimental setup. The main design parameters are the ratio of the cross-sectional area of the chamber to the fluid passage, the length of the fluid passage, etc., and their optimal design is such that the loss angle is greater than 45 ° in the target frequency range of 10 to 20 Hz. The hydro bushing designed for reducing the judder vibration was prepared for the actual vehicle application test and applied to the actual vehicle test. In this study, the proposed hydro bushing was applied to the G bushing of the low arm of the front suspension system of the vehicle. The loss angle of the manufactured hydro bushing was measured using acceleration signals before and after passing through the bushing. The actual vehicle test was performed on the noise dynamometer for the performance analysis of the judder vibration reduction.

Highlights

The suspension application of the hydro-bushing was applied to the lower arm G bushing of the front suspension in Fig.1 to reduce the steering wheel judder vibration due to the braking force imbalance. [1~2]
Judder is known to be caused by disc thickness variation (DTV), which is caused by side run-out (SRO) during manufacturing and thermal deformation resulting from the braking process
A simulation for predicting the dynamic stiffness and loss angle of hydro bushings with nonlinear elements such as fluid passages was performed

Summary

Introduction

The suspension application of the hydro-bushing was applied to the lower arm G bushing of the front suspension in Fig. to reduce the steering wheel judder vibration due to the braking force imbalance. Judder vibration is a low-frequency vibration phenomenon in the range of 10 ~ 20Hz caused by unbalance of braking force when the vehicle is braking at a light deceleration of 0.1 ~ 0.2g at a speed of 120km/h, which is a highway driving speed. The main design parameters are rubber spring constant, fluid characteristics, and the shape of the chamber and inertia track. The frequency characteristics of the hydro bushing applied to the G bushing of the front suspension low arm were designed to effectively reduce the judder vibration. The performance of the hydro bushing was verified by performing the actual vehicle test on the noise dynamo using the vehicle with the hydro bushing manufactured

Characteristic design of hydrobushing

Simulation for predicting the performance characteristics

Design parameters

Frequency characteristics

Conclusions