Brake Squeal Experimental And Improvement Analysis On Disc Brake Assembly

The noise produced by the braking process of the brake assembly which is an important component of vehicle will affect the ride comfort seriously.Aiming at the abnormal braking noise during the development and validation of a disc brake assembly in an enterprise,the reasons leading to the noise are checked,the structure of the disc brake assembly is improved,and the abnormal noise of disc brake is eliminated effectively.The main conclusions are as follows:(1)Through the analysis of the real vehicle road test,the main frequency of the brake noise is near the 5860 Hz,which is relevant with braking pliers,stent,brake block assembly and brake disc.Moreover,the happening rate of brake noise is related with brake disc temperature and braking deceleration.(2)The natural frequencies and modes of the associated parts in free state and constrained state are calculated and measured by means of finite element modal analysis and hammer striking method.Under constraint condition,one order natural frequency of brake pliers is 5775 Hz,the second order natural frequencies of the inner and outer braking block assembly are 5746 Hz and 5856 Hz respectively,which is very close to that of the braking scream noise.The two frequency components are inclined to cause the modal coupling,leading to resonance overlay and the brake noise.(3)A variety of measures is adopted to improve the brake block assembly structure,the natural frequency is changed,the surface pressure uniformity is improved,and the damping ratio is increased to solve the noise problem.The slotting and chamfering of the brake block assembly,and the improving of the contact pressure of the working surface of the brake disc are not effective;The silencer of the brake is changed to MS18035 with the damping ratio changed.The brake noise disappears in the platform test and the real vehicle test,the brake noise problem is solved well.In conditions of trying not to change the brake assembly structure and friction materials,the transmission path of braking self-excited vibration is controlled,the damping ratio of the silencer is increased,the brake screaming noise is restrained effectively with the optimal cost.(4)The modal coupling mechanism is the fundamental cause of brake assembly screaming noise,the natural frequencies of at least two disc brake components are close to noise frequency.At the beginning of the design and development,the modal of the key components affecting the brake screaming noise should be analyzed to avoid the modal coupling of components such as braking pliers,stent,brake block assembly and brake disc.The natural frequency of these parts should be 200 Hz apart as far as possible,which could reduce the product structure changes caused by the brake scream noise and the cost and period of a long time validation.