Brake Judder Analysis And Improving For Vehicle Disc Brake

In the past, most of braking system designs only focused on function design.However, with users’ substantially increase of requirements on entire comfort ofcar, the NVH (noise, vibration and harshness) problem of braking system isincreasingly prominent. As a typical NVH problem, brake judder is alow-frequency vibration phenomenon, which can be shown as circumferentialreciprocating swing of steering wheel, severe vibration of brake pedal andsevere vibration of under frame and be felt by driver in case of braking withincertain speed. The brake judder seriously impacts the comfort of vehicle andincrease the possibility of misoperation by less experienced drivers and thedriving fatigue. Moreover, low-frequency vibration accelerates the fatigue andageing of relevant parts and components. Therefore, researches on suppressionmethod of braking judder have significant meaning for improvement of drivingsafety, decrease of users’ complaint and increase of service life of auto parts.First of all, the paper introduces the current research status of brakingvibration at home and abroad and the present main approach and researchmethod for solving braking vibration. Then, combined with actual situationsencountered by enterprises, road braking vibration test has been taken towardstarget product, and the excitation source–brake as well as the vibrationtransmission path–brake, knuckle (including tire and arm), steering rod andfinally steering wheel have been confirmed. Next, the relation between the discthickness variation (DTV) and the brake torque variation (BTV) and brakevibration acceleration is analyzed through dynamometer test, and throughanalysis on the frequency and order of DTV, BTV and brake vibrationacceleration in the dynamometer test, it is confirmed that DTV growth willincrease the BTV growth, so as to cause braking judder. In addition, dynamicmodel of brake is established; the mathematic relation between DTV andstiffness&damping of braking system and BTV is summarized; the occurrencemechanism and influencing factors of braking judder is theoretically analyzed.After testing the stiffness of braking system and obtaining the system dampingthrough reference documents, simulation analysis on the pad stiffness and as well as the impact of DTV on BTV is conducted in Matlab by inputting actuallymeasured brake thickness fluctuation data and applying Runge-Kutta method.Finally, the solution satisfies the target requirements of customers through theoptimal design of several calipers systems and the verification by multi-wheeldynamometer test and vehicle road test by taking suppression of brakein-process DTV increase as target.Through researches on brake judder problem of certain vehicle, this paperintroduces vibration test system and brake road test system for enterprises, andon such basis, the paper concludes the development procedure for brake judder,the DTV dynamometer test and assessment specification, the BTV dynamometertest and assessment specification as well as the specification for brake vibrationroad test, establishing a technology platform with continuous accumulation andlaying a good foundation for subsequent further research and development work.