带式制动器动态制动力矩特性

Dynamic braking torque characteristics of a band brake

带式制动器作为动力保持型三挡自动变速器(automatic mechanical transmission,AMT)换挡执行元件之一,其动态力矩特性对换挡品质至关重要。为进一步研究带式制动器的动态力矩特性,论文建立了带式制动器有限元模型,设计了样机实验台架,完成了不同工况的实验测试。结果表明:动态制动力矩不仅与制动鼓转速、制动力大小、制动力作用半径等因素有关,同时也取决于制动力加载的速度;相同条件下,制动力加载速度越快,制动带产生的动态制动力矩越小,并从动水升力角度作了定性分析。依据实验结果,提出等效动摩擦因数、等效力矩输入系数及补偿系数的概念,得到动态制动力矩的经验公式,从而将制动力加载速度融入到动态制动力矩中。

Band brakes are used as shift actuators in uninterrupted powertrain automatic mechanical transmissions(AMT).The dynamic characteristics of the brake band then strongly affect the shift quality.The dynamic torque characteristics of a band brake were studied using a finite element model of the band brake with experimental tests for various working conditions.The results show that the dynamic braking torque is not only related to the brake drum speed,braking force,and braking force radius,but also depends on the braking force loading speed.When the other conditions are kept the same,a faster braking force loading leads to a smaller braking torque on the band.The effect was described using a qualitative analysis of the hydrodynamic lift force.The results were used to define an equivalent dynamic friction coefficient,an equivalent torque input coefficient and a compensation coefficient with an empirical equation for the dynamic braking torque that integrates the braking force loading speed into the dynamic braking torque.