多片式离合器局部高温区成因与系统稳定性研究

离合器在接合过程中常发生热弹性不稳定性,这是导致摩擦副表面出现局部高温区的重要原因. 针对车辆换挡机构用多片式离合器,采用伽辽金法建立了离合器摩滑过程三维有限元分析模型,将温度场扰动变化问题转化为矩阵特征值问题,求解并通过试验验证了系统发生TEI时的临界速度、摩擦界面温度扰动增长率和温度场分布的相互关系. 研究表明,当离合器转速超过临界速度时,1 s内温度波动由3%上升到35%,对偶钢片表面沿圆周方向出现局部高温区,符合离合器实际使用过程中出现的表面热斑和烧损痕迹. 离合器对偶片及摩擦衬片厚度、半径、内外径比、摩擦材料的导热系数及弹性模量均对离合器热弹性不稳定性均有重要影响,摩擦材料热膨胀系数影响较小. 

Research on Hot Spots of the Multi-Disk Clutch and Stability of the System

Thermoelastic instability (TEI) during the synchronizing process of clutches is the main reason for hot spots on the frictional pair. On the basis of vehicular shift clutches, a three dimensional finite element model was built by Galerkin method for determining the critical speed of TEI, the growth rate of the perturbation and the temperature on the nodes, which were confirmed by the bench test. In the process, the growth rate of the temperature perturbation was calculated by an eigenvalue solution. Both theoretical and experimental results show that a strong inhomogeneous temperature field appears (its temperature fluctuation rises from 3% to 35% in 1 second), and hot spots appear along the circle of the mating disk on condition that the working speed exceeds the critical speed. Some structural and material properties, e.g., the thickness of the mating disk and frictional disk, the radius of the clutch and the ratio between inner and outer radius, the thermal conductivity and the elastic modulus of the frictional material, have significant effects on the unstable behavior of the clutch, but the effect of their heat-expanding coefficient is less.