湿式DCT双离合器联合起步控制建模与仿真

应用平均雷诺方程和粗糙表面弹性接触模型,建立了湿式离合器接合过程动态传递转矩模型。在湿式离合器接合过程动态传递转矩模型的基础上,建立了车辆起步过程中湿式双离合器联合起步动力学模型,并利用Matlab/Simulink仿真平台对模型进行了仿真验证。以20%油门开度起步为例,分别对引入动态传递转矩模型和经典静态转矩模型的湿式双离合器联合起步过程进行了仿真分析,结果表明,引入湿式离合器动态传递转矩模型能够更加真实地表征湿式DCT起步过程中转速、冲击度及滑摩功变化规律。     

湿式换挡离合器在不同起步挡位对传动系统动态特性影响的仿真

结合在研项目,建立了某综合传动装置上湿式换挡离合器工作过程中的转矩传递模型和离合器油缸充油过程的模型,并应用MATLAB软件针对不同起步挡位对车辆传动系统动态特性的影响进行了仿真研究．     

湿式摩擦离合器多目标优化设计

湿式离合器的带排转矩影响传动装置的效率，离合器的接合转矩影响传动装置的可靠性，但在通常情况下，降低带排转矩和增大接合转矩是相互矛盾的。以湿式摩擦离合器为研究对象，以湿式离合器摩擦片内径、外径、径向槽深、径向槽宽和径向槽数、摩擦副间隙为优化设计变量，以离合器的带排转矩最小和接合转矩最大为优化目标，建立优化设计数学模型，给出了Matlab的优化工具箱求解方法；并以某压裂车变速箱离合器为实例，进行了多目标优化设计。优化后带排转矩减小了31.67%，接合转矩增加了33.51%。结果表明，所提优化方法有效，可为湿式离合器的摩擦片结构设计与参数优化提供理论参考。     

重型非公路汽车湿式离合器表面系数对接合特性影响的研究

针对湿式离合器在接合过程中存在的磨损和高温的问题,通过引用湿式离合器表面系数,以重型非公路汽车湿式离合器为研究对象,运用微凸体分布模型,研究湿式离合器在不同材料状态下摩擦因数和制动接合特性变化规律。分析结果表明,使用韦伯微凸体分布分析效果比使用传统分布模型接合时间长,接近实际工况;通过引入表面系数和韦伯分布后,在离合器接合初始阶段存在转矩波动,该转矩波动是造成震颤的主要原因;在接合末期存在制动转矩增加,可以通过引入斜率为正的摩擦因数-速度曲线解决,此外磨平材料的啮合时间要比跑合阶段的时间短。     

双圆弧槽摩擦片摩擦系数影响因素分析及实验测试

湿式换挡离合器摩擦片摩擦系数受压力、转速和润滑流量等多种工况参数影响,研究摩擦系数随工况参数的变化规律对于离合器设计具有重要意义。以铜基粉末冶金双圆弧摩擦片为研究对象,对摩擦系数的影响因素进行了分析,利用Simulink搭建了油膜厚度仿真模型,计算了摩擦副实际接触面积的大小,并讨论了实际接触面积对摩擦系数的影响;通过实验采集转矩值,计算得到了平均摩擦系数;选择研究较少的双圆弧摩擦片进行分析和实验研究。结果表明:控制油压在(0.3~0.7)MPa范围内,稳定磨损期的动摩擦系数随压力增加而减小,控制油压低于0.4MPa时摩擦系数随转速差和润滑流量单调递增,反之单调递减;台架试验测试的静摩擦系数与厂家给定值略有差别,论文研究结果对湿式离合器工程设计具有一定参考意义。     

湿式双离合器扭矩传递特性对换挡品质影响的研究

湿式双离合变速器中离合器扭矩传递模型的精准度将直接影响其控制效果。本文通过建立包含粘性扭矩和粗糙扭矩的湿式双离合器扭矩传递模型,分析温度及主从动盘转速差对离合器扭矩传递特性的影响,并将其嵌入到搭载湿式双离合器的整车模型中,研究了扭矩传递特性变化对车辆换挡品质的影响。仿真结果表明粘性扭矩对整车的换挡品质有较为显著的影响,尤其温度变化时更加显著。     

磁粉性能对磁粉离合器特性影响分析研究

研究了磁粉离合器转矩传递的工作机理,建立了磁粉离合器磁场场域的分析模型,重点分析研究了磁粉的磁性能和粒径对磁粉离合器转矩传递特性的影响关系,仿真结果与磁粉离合器实际工作特性相吻合。研究结果表明,通过提高磁粉材料磁性能、减小磁粉粒径可有效提高磁粉离合器转矩传递性能。     

湿式离合器对偶片间油气两相流动的数值模拟

湿式离合器高速旋转时内部形成的复杂油气两相流动会对离合器的性能产生影响,因而需要对湿式离合器内的两相流动特性展开研究。基于有限体积法,采用流体体积函数(Volume of fluid,VOF)多相流模型、RNG k-ε湍流模型,建立考虑径向沟槽影响的三维湿式离合器对偶片间油气两相流动模型。通过对流动模型中油气两相N-S方程进行数值求解,获得了湿式离合器对偶片间油气两相流动的流场分布特性,分析沟槽数量和转速对流场中油相分布及带排转矩的影响。结果表明:湿式离合器内部的润滑油分布是不均匀的,随沟槽的分布呈现出周期性变化,沟槽处润滑油油液体积分数最大;转速和沟槽数目的增加均会使对偶片间油液体积分数下降,影响湿式离合器内润滑油分布的不均匀性;沟槽总面积不变时,增加沟槽数量能使带排转矩最大值减小,最大转矩对应的转速提前。本研究为湿式离合器内部流场分析和带排转矩研究提供了一种新方法。     

基于发动机恒转速控制的DCT双离合器联合起步研究

建立了DCT车辆双离合器联合起步的数学模型。基于发动机恒转速控制原则,推导了起步过程中离合器传递转矩与冲击度之间的关系,优化了两离合器传递转矩的变化过程。利用PID控制器解决了维持发动机恒转速与离合器接合速度的矛盾,建立了仿真模型进行验证。     

新型重载摩擦离合器

介绍一种新型摩擦离合器，该离合器其当量摩擦系数为一般摩擦离合器的摩擦系数的10～30倍以上，所以体积小，传递转矩大，且结构简单、工艺性好、造价低廉、寿命长，是一种较为理想的新型摩擦离合器。     

液体粘性调速离合器中摩擦副的调速分析

介绍了液体粘性调速离合器中摩擦副的工作机理。在调速范围内 ,液体粘性调速离合器中摩擦副往往在流体润滑、混合润滑、边界润滑直到直接接触的工况条件下工作 ,不同的工况以及负载对液体粘性调速离合器的输出转速和输出转矩有很大的影响。采用表面粗糙度的平均模型 ,以及GT微凸体接触模型 ,对液体粘性调速离合器在调速过程中摩擦副所涉及的工况进行了分析讨论。提出了在稳态条件下 ,输出转速与输出转矩的计算方法。     

Clutch Shudder Correlated to ATF Degradation through Local Friction vs. Velocity Measurements by a Scanning Force Microscope

Shudder in continuously slipping wet clutch (CSWC) systems is an instability that manifests itself as a vibration of the automobile's drive train. Dynamometer experiments imply that the shudder is connected to degradation of the frictional properties of the clutch friction material-automatic transmission fluid (ATF) system. The poor friction characteristics are revealed in negatively sloped torque vs. slip-speed curves which can result in dynamic friction oscillation instabilities. The authors report local measurements of friction vs. velocity with the use of a scanning force microscope (SFM) on new and glazed wet clutch friction material with either new or degraded ATF acting as a lubricant. The friction material was a commonly used cellulose/phenolic resin material. Results in the very low-speed dynamic regime indicate that the fluid condition plays a critical role in determining the slope characteristics of the friction vs. velocity curve. ATF degraded in service imparts a flat or negative slope to the friction vs. velocity curve, whether on new or glazed (degraded) friction material. A positive slope is measured for fresh ATF. The SFM measurements are therefore consistent with dynamometer and vehicle experiments which measure gross properties of the friction clutch system. The ability of the SFM to reproduce the dynamometer results on a local scale implies that shudder is not due to the gross fluid flow or mechanical effects that are present in a complete torque converter. The frictional characteristics of the clutch plate materials and the ATF are paramount. This technique allows continuous monitoring of ATF fluid degradation in test fleet vehicles without ATF replenishment since only a few ccs of fluid are necessary for these tests.     

Thermal influence on torque transfer of wet clutches in limited slip differential applications

Wet clutches operating under low velocity and high load are studied with the aim of obtaining reliable models for the torque transfer during boundary lubrication conditions. A friction model which takes temperature, speed and nominal pressure into account is developed and used with temperature calculations to be able to simulate behavior of a wet clutch working in boundary lubrication regime. Predicted torque and temperatures from the model agree well with experimental data.     

应用铜基粉末冶金摩擦片的粘液传动的承载能力分析

铜基摩擦材料已经在各种机械和工业车辆的离合器和制动器的摩擦衬面中广泛应用,根据表明,湿式摩擦式的性能对动摩擦系数和承载能力有很大的影响。粘液传动是利用主动和从动摩擦片间的油膜剪力来传递运动和转矩实现无级变速的一种新型传动。本文将着重讨论采用带油槽的铜基粉末冶金摩擦力的粘液传动的传动机理,分析摩擦片间油膜的承截能力,并进一步讨论油槽深度和油槽数目对承载能力的影响。     

Wet Clutch Friction Interfaces under Water-Contaminated Lubricant Conditions

The performance of wet clutches used for automatic transmissions or other applications usually includes the desired positive friction characteristics and a shudder-free torque generation. Changes in the operating variables such as the lubricant conditions influence the formation of a tribofilm, and friction characteristics and can alter the degradation of the friction interfaces. In this work, the friction characteristics and degradation of the paper–steel friction interfaces were monitored when a commercial fully formulated automatic transmission fluid (ATF) was contaminated with water. It was found that water in ATF influenced the clutch stability by increasing the mean coefficient of friction (µ) and the negative friction–velocity slope. Surface studies of the posttest friction interfaces clearly indicated reduced surface porosity and permeability, increased wettability, and changed elemental composition on the contacting surfaces after tested with water-contaminated ATF. Moreover, water-contaminated paper liners' thermal decomposition shifted to a lower temperature compared to an uncontaminated liner during thermal analyses. These results displayed faster degradation and reduced service life of the clutch friction interfaces due to water contamination. The resultant surface condition can be associated with the observed unstable friction and negative friction–velocity slopes.     

分形特征在湿式离合器磨合状态预测中的运用

针对湿式离合器试验过程中磨合状态的预测问题,提出利用摩擦转矩信号分形特征来预测和评价磨合状态的新方法.首先,分别阐述了摩擦转矩信号盒子维数和关联维数的计算方法;然后,在湿式离合器试验台上提取了磨合试验的摩擦转矩信号,并对信号进行了自相似性分析;最后,应用盒子维数和关联维数分别对摩擦转矩信号进行了分形研究.分析结果表明:盒子维数和关联维数都能定量描述试验过程中摩擦转矩信号的分形特征,随着磨合次数的增加,摩擦转矩信号的盒子维数和关联维数的波动范围都逐渐减小,并且最终收敛于较小的波动范围.因此,利用试验中摩擦转矩信号的分形特征能够在不开箱条件下定量地预测和评价湿式离合器的磨合状态.     

基于动摩擦系数的微型车离合器起步接合过程动力学仿真

针对常用机械式自动变速器(automated mechanical transmission,AMT)起步控制策略由于将离合器动摩擦系数视为常量,而忽略其变化所导致的车辆起步冲击度大的问题,对某款微型车AMT的起步过程进行了研究,提出了基于动摩擦系数的微型车离合器起步接合过程的动力学研究方法,根据摩擦学原理及其试验,讨论了离合器动摩擦系数随转速变化的关系,建立了离合器三维实体模型,并利用ADAMS软件对离合器起步接合过程进行了动力学仿真,分析了干式膜片弹簧摩擦离合器的动摩擦系数与其摩擦力矩和冲击度的关系。研究结果表明,与动摩擦系数为常量的离合器相比,动摩擦系数为变量的离合器半接合点和同步点的冲击度更大。其中,半接合点的冲击度增加率为110%,验证了动摩擦系数变化对车辆起步冲击度作用的重要性。     

Influence of operating conditions on friction and temperature characteristics of a wet clutch engagement

To optimise the gear change in automatic transmissions, more knowledge is needed of the engagement behaviour of wet clutches. A factorial design investigation of the engagement of a wet clutch has been carried out. The friction and temperature characteristics have been studied. The experiments were carried out in an apparatus that can vary sliding velocity, drive torque, inertia, force rate, and lubricant flow. The results show how these parameters affect the response data: engagement time, developed energy, temperature rise, maximum torque, maximum power, static friction, dynamic friction, and initial friction. There are interaction effects between some of the input parameters, but they are relatively small. The friction coefficient varies over time but is independent of the input parameters, except for dynamic friction, which decreases with increasing sliding velocity, drive torque, and inertia. The temperature rise was found to be proportional to developed energy and both these were most affected by sliding velocity. The drive torque and force rate have the greatest effect on the engagement time.     

Thermal Behaviour of a Slipping Wet Clutch Contact

Wet clutches are used in automatic transmissions to enable gear changes and also to reduce energy loss in the torque converter. These friction devices are susceptible to stick–slip effects, which result in the vehicle giving an unsteady ride. Stick–slip effects can be avoided by ensuring the wet clutch and lubricant combination produces a friction coefficient that increases with sliding speed. Although wet clutches have been studied throughout the industry for many decades, the mechanism of the generated friction is still not fully understood. It is known that, because of the fibrous nature and thus very large roughness of friction material, the overall contact between clutch plates actually consists of many small, independent, contact units, which are the sites of the generated friction. Some authors have suggested that a temperature rise due to friction either at these contact units or of the overall clutch plate may be important in controlling friction behaviour. In this study, the flash temperatures at the contact units formed in the wet clutch contact have been measured using an infrared camera. Three friction materials have been tested. It was found that measured flash temperature in a pure sliding system similar to that present in a slipping clutch remain well below 5 °C, and are therefore unlikely to play a major role in the observed friction-speed dependency of slipping wet clutches at speeds below 2 m/s.     

考虑摩擦副接触应力场和冷却流场的湿式离合器温度场分析

温度对湿式离合器摩擦副的摩擦特性和热失效具有重要影响。为了获取湿式离合器温度场的分布规律,建立摩擦副接触应力分布有限元模型和摩擦片沟槽内冷却流场数值计算模型,获得了摩擦副接触应力随离合器接合油压的变化规律和冷却流场对流换热随离合器转速的变化规律。在此基础上,提出考虑离合器摩擦副接触应力分布时变特性和冷却流场分布时变特性的离合器温度场数值计算模型。将所建温度场模型的仿真结果与试验结果作对比,验证了所建温度场模型的正确性。通过计算获得了湿式离合器接合过程中不同钢片在半径和厚度方向的温度分布规律,揭示了摩擦副接触应力场和摩擦片沟槽内冷却流场对离合器温度场的影响规律。结果表明,在离合器摩擦副半径方向上,摩擦副的温度分布规律与接触应力分布规律相一致。而摩擦片沟槽内冷却流场的对流换热主要影响离合器同步阶段的温度分布。