The Effects Of Bead On PCR Tire Uniformity

The uniformity of passenger car radial tyre plays an important role in vehicle comfort and safety,which is an important evaluation index of tire performance.Tire is a complex mixture of rubber,cord and steel wire with a long production process,whose uniformity is affected by many factors.At present,the research on tire uniformity mainly focuses on tread,belt and carcass etc.However,as the main load-bearing component of bead,the bead ring has great influence on tire uniformity.the uniformity influence law and mechanism of bead ring are not fully clearified,which is a key technical problem that needs further research in tire industry.In this paper,the influence of bead ring structure design and manufacturing process on tire uniformity was studied.The uniformity test method of low flange hub is innovatively proposed,which greatly improves the stability of test data.The influence of bead inner circumference,mold design,bead molding process and bead assembly accuracy on the uniformity of radial tire is investigated with quantitative influencing factors analysis and research.Through actual tire test,factors of the bead ring structure design(clearance between bead and rim,bead compression ratio and vulcanization mold structure)are studied,the reasonable range of structural design parameters is determined.The results show that tire uniformity,anti rim displacement performance and fit uniformity should be considered in the design of the gap between the bead ring and the rim between 1.8-3.6 mm;when the compression ratio of bead bottom is between 15% and 35%,the requirements of vehicle braking performance and tire uniformity can be met at the same time;when the mold angle is set at 9 ° / 17 °,the thickness distribution of the compound at the bottom of the bead is more uniform,which improves the uniformity of the wheel assembly and the dynamic performance of the whole wheel.With the systematical tests,influence of bead manufacturing process factors(pre bending process,bead assembly accuracy and winding process)on tire uniformity is studied in depth.The reasonable range of manufacturing process parameters was determined.When the ratio of diameter between pre bending wheel and winding disk is 2.0%,the quality of bead ring is the optimal.When the clearance between the buckle plate and the bead is 0.1-0.2 mm,the uniformity and dynamic balance performance of the tire are the optimal.When the ratio of the width of the buckle plate to the width of the bead is in the range of 60 % to 90 %,the uniformity and dynamic balance performance of the tire are the optimal.When the opening of the winding disc is 39.5 mm,the diameter stability and accuracy of the produced bead are the optimal.The research results of this paper have achieved obvious results in the improvement of tire uniformityin the company,Both indoor and outdoor tests verify the effectiveness of the research conclusion,which has a very good practical value.Work in this paper can provide some theoretical guidance for tire manufacturers in the future,especially in the bead part design and manufacturing process,in order to improve the uniformity of car radial tire to some extend.