Test Analysis And Control Of Brake Judder Of Vehicular Brake Disc

Brake judder is a low-frequency forced vibration in the car’s braking process,mainly represented by steering wheel judder,which may be accompanied by brake pedal and floor shake.The occurrence of brake judder not only seriously affects the normal driving of the vehicle,but also affects the safety of the driver.Therefore,improving vehicle brake judder levels is also the goal of OEMs and component suppliers.This paper takes a vehicle with brake judder in an enterprise as the object,analyzed the brake judder problem by means of test analysis,proposes improvement measures and implements it.Firstly,the vehicle braking test is used to reproduce the braking judder phenomenon,the vibration acceleration signal characteristics during the braking judder process are analyzed,the braking judder excitation source is confirmed,and the suspension system modality can be used to simulate the vibration signal of the braking judder excitation source amplification.A bench test was performed on the brake system.The test analyzes the friction coefficient and temperature change of the brake disc during braking,and eliminates the possibility of braking brake torque fluctuation caused by the change of friction coefficient during braking,which may cause braking judder.The bench test also analyzes the braking torque variation during the braking process,and verifies that the braking torque variation amplitude will increase as the braking disk thickness variation amplitude increases.The thickness variation of the brake disc thickness increases as the mileage(number of brakes)increases.Modal test analysis of the suspension and steering system was carried out.The modal test confirmed that the suspension system has a 22.8Hz asynchronous torsional mode and a 23.4 Hz synchronous torsion mode in the X direction of the vehicle.The steering system has an 11.9Hz torsional mode.These three modes are in the range of 5Hz~30Hz excitation frequency of braking judder,which is an important cause of braking judder.The influencing factors and control measures of braking judder are analyzed from two aspects of excitation source and transmission path.The excitation source is mainly affected by the disc thickness variation,the disc and the pad.The main factors affecting disc thickness variation are geometric irregularities,uneven wear,uneven friction film,uneven heating and uneven pressure distribution.The compression stiffness of pad,the thermal performance and ventilation structure design of disc have the greatest impact on brake judder.The transfer path,i.e.the suspension and steering system modes,is an important cause of brake judder.The stiffness and mass of the suspension system and steering system should be designed to avoid the brake judder excitation frequency.Finally,starting from the cost control and feasibility of the enterprise,the brake judder improvement scheme for improving the accuracy of the brake disc and the stiffness of the lower control arm is proposed,and the real vehicle verification effect is obvious.