Dynamic Engaging Characteristics of Wet Clutch in Automatic Transmission

Wet clutch is an important shifting component in automatic transmission,and its properties will affect the gear shift performance. By comparing the calculated and test results,the static friction torque model was proved to be capable of describing the real pressure and torque only in the situation of high-energy engagement.Therefore,a dynamic torque model was proposed on basis of hydrodynamic properties between friction surfaces, in which the clutch engagement was divided into three phases for hydrodynamic lubrication, mixed lubrication, and mechanical contact. The proposed dynamic torque model was validated by comparing the calculated and test results. The effects of temperature,pressure,and pressure changing rate of automatic transmission fluid( ATF) on the clutch torque were analyzed. Based on these results,the clutchto-clutch torque control during shifting in automatic transmission was optimized,and as a result,the shifting comfort was significantly improved since the problems such as the fluctuation and sudden drop of the engine rotating speed during shifting were eliminated.

Developing Additive Technology for Wet Dual Clutch Transmissions

Wet dual clutch transmissions(W-DCTs) show overall benefits including excellent fuel efficiency,wide torque capacity range,long durability,driving comfort and sportiness.Many breakthroughs have been made to further improve the fuel efficiency by design innovations and introductions of new hardware.Each W-DCT has its unique design and hardware.It demands the lubricant to provide excellent wet clutch friction performance and anti-shudder friction durability,good synchronizer friction performance and durability,high load-carrying ability,excellent bearing performance,strong anti-corrosion performance,high thermal and oxidative stability,excellent material compatibility,etc.Particularly,the requirement of the wet clutch friction performance in W-DCT is much more severe than conventional ATFs and CVTFs.We report here our latest W-DCTF technologies developed for different W-DCT applications.DCTF-1 was optimized for a two-sump W-DCT application with the clutch lining material of friction material A(FM-A).DCTF-1 shows high and stable dynamic friction,static friction,particularly,high quasi-static friction without any shudder tendency in GK tests.DCTF-2 was designed for a one-sump W-DCT application with the same clutch lining material of FM-A.DCTF-2 completes 42,000 cycles of the severe GTI chassis dynamometer vehicle test without any issues,which is comparable to the factory fill fluid DCTF-FF.DCTF-3 was developed for a one-sump W-DCT application with a different clutch lining material of FM-B.DCTF-3 shows high and stable dynamic friction in the severe newly developed SAE DCT test procedure.DCTF-3 also gives excellent LVFA durability of over 720 h in the JASO M349 test procedure on FM-B.

Adaptive Clutch Engaging Process Control for Automatic Mechanical Transmission

Based on detail analysis of clutch engaging process control targets and adaptive demands, a control strategy which is based on speed signal, different from that of based on main clutch displacement signal, is put forward. It considers both jerk and slipping work which are the most commonly used quality evaluating indexes of vehicle starting phase. The adaptive control system and its reference model are discussed profoundly. Taking the adaptability to different starting gears and different road conditions as examples, some proving field test records are shown to illustrate the main clutch adaptive control strategy at starting phase. Proving field test gives acceptable results.

Application of clutch to clutch gear shift technology for a new automatic transmission

For the purpose of engineering development for a new 8-step speed automatic transmission,a simplified dynamic model for this gearbox was established and key parameters which affected the shift quality were analyzed.Aiming at four different shift types,the ideal characteristics of shift clutch and engine control were set up.By using torque estimation method,PI slip control algorithm and engine coordinated control principle,the control model and transmission controller were well developed for three shift phases which included rapid-fill phase,torque phase and inertia phase.The testing environment on the rig and prototype vehicle level was built and the testing results obtained in ultimate condition could verify the accuracy and feasibility of this shift control strategy.The peak jerk during shift process was controlled within ±2 g/s where the smooth gearshift was obtained.The development proposal and algorithm have a high value for engineering application.

Simulation study on starting of dual clutch transmission for tracked vehicles

In order to study the application of dual clutch transmission （DCT） on tracked vehicles, a simulation moclel and two control methods were performed for starting analysis. Based on a certain transmission of an existing tracked vehicle, a DCT structure was proposed. Matlab/Simulink was a dopted as a platform to develop the simulation model. The engine speed was controlled to follow the target speed as a launch strategy. Two control methods, a proportional integral derivative （ PID ） control method and a fuzzy control method, were proposed to control the engine throttle and oil pressure in order to track the target engine speed. Simulation results show that either the PID control or fuzzy control method can improve the starting performance compared with no loop control meth od. Fuzzy control method can lead a better starting quality compared with PID control method.

Design of Multi-domain Collaborative Simulation System for Dual Clutch Transmission Based on CAN Bus

A multi-domain collaborative simulation(MDCS) system for dual clutch transmission(DCT) was presented based on controller area network(CAN) bus.An interface card of CAN bus was designed,in which MDCS subsystems were linked as the nodes according to the interface mode of MDCS.A DCT simulation model was established based on Matlab/Simdriveline,whose running process was accurately controlled by the designed control system.The playback system of vehicle state(VPS) was proposed whose input was the road-test data,with a real vehicle test environment for the development of transmission control unit(TCU) being provided.A DCT kinematic system model was set up,and the running status of DCT parts could be displayed in real time.The functions of MDCS were verified based on the extra-urban driving cycle(EUDC) and the vehicle road-test data respectively.The results show the functions of MDCS are accomplished,and the unified supporting platform for the development of TCU is achieved by MDCS.

OPTIMAL TORQUE CONTROL STRATEGY FOR PARALLEL HYBRID ELECTRIC VEHICLE WITH AUTOMATIC MECHANICAL TRANSMISSION

In parallel hybrid electrical vehicle （PHEV） equipped with automatic mechanical transmission （AMT）, the driving smoothness and the clutch abrasion are the primary considerations for powertrain control during gearshift and clutch operation. To improve these performance indexes of PHEV, a coordinated control system is proposed through the analyzing of HEV powertrain dynamic characteristics. Using the method of minimum principle, the input torque of transmission is optimized to improve the driving smoothness of vehicle. Using the methods of fuzzy logic and fuzzy-PID, the engaging speed of clutch and the throttle opening of engine are manipulated to ensure the smoothness of clutch engagement and reduce the abrasion of clutch friction plates. The motor provides the difference between the required input torque of transmission and the torque transmitted through clutch plates. Results of simulation and experiments show that the proposed control strategy performs better than the contrastive control system, the smoothness of driving and the abrasion of clutch can be improved simultaneously.

Influence of oxidation of automatic transmission fluids (ATFs) and sliding distance on friction coefficients of a wet clutch in the running-in stage

In this paper,the influence of oxidation of automatic transmission fluids(ATFs)and sliding distance on the friction coefficients of a wet clutch in approached running-in conditions was investigated.The ATFs were oxidized by a laboratory process approaching oxidation occurred in actual ATFs.Oxidation was evaluated by means of increase in carbonyl compounds and depletion of zinc dialkyldithiophosphates(ZDDPs)additives.Also,the changes in kinematic viscosity and viscosity index were evaluated.Pin-ondisk tests were conducted to replicate the actual sliding contact in a wet clutch.The pin specimens were cut from friction material composite plates and the disks were actual steel separators both from an automotive wet clutch.Friction coefficient, μ,was measured at progressive sliding velocity,ν,to obtain μ–νcurves at 26 and 100°C.Three μ–νtests were consecutively run using the same pair of specimens and oil.The cumulative sliding distance for each μ–νtest generated surface flattening using the oils.The friction coefficients of the wet clutch increased due to the ATFs oxidation meanwhile the dm/dv values decreased in most cases.It suggests that ATF oxidation can enhance torque capacity of the wet clutch,but it could reduce anti-shudder property.Progressive sliding distance improved the slopes in the μ–νresults using fresh ATFs meanwhile it generated a slope decrease by using aged ATFs.

考虑离合器摩擦性能衰减的湿式DCT车辆起步控制研究

建立了考虑离合器摩擦系数变化及离合器性能衰减的湿式双离合变速器(dual clutch transmission,DCT)车辆起步过程动力学模型,以车辆起步过程冲击度、滑摩功和起步滑摩时间为优化目标,采用线性二次型最优控制方法获得了车辆起步过程离合器最优传递转矩。针对离合器摩擦系数变化及离合器性能衰减对车辆起步过程离合器压力控制的影响,提出了一种离合器压力非线性鲁棒控制策略,以实现对离合器最优传递转矩的跟踪。结果表明,所提出的非线性鲁棒控制策略能够在离合器摩擦系数变化的情况下实现对离合器最优传递转矩的有效跟踪,跟踪误差不大于0.02 N·m,且能够适应摩擦性能衰减导致不同寿命阶段摩擦系数的不同变化规律,与比例-积分-微分(proportion-integral-differential,PID)控制策略相比具有更精确的控制效果和更强的鲁棒性。

汽车自动变速器换挡控制自动校准算法研究

为改善自动变速器的换挡特性,提出了一种基于模型的自动变速器离合器液压自动校准方法,实现离合器换挡参数的自动调整。该校准方法包括自动变速器仿真模型、车辆仿真分析算法和基于优化过程的自动校准算法,并在优化过程中进行迭代仿真和分析。以通电换挡为研究对象,仿真结果表明无论是通电升挡,还是通电降挡,该方法均能够有效地执行离合器液压曲线的基本映射,通过所提出的校准方法能够缩短实际车辆试验前的校准时间,提高自动变速器开发过程的效率。

一种变速箱离合器自动安装机构的设计

离合器是变速箱的重要核心组件,也生产装配工艺中重要的环节。本文介绍了离合器在变速箱装配生产线上实现自动装配的方法和自动装配机构的设计,该自动装配机构和工业机器人组合应用,利用PLC作为电气控制核心,采集外部信号,通过Profinet总线网络与机器人交互信息,实现对离合器的自动化装配。这个机构设备可以很好的解决离合器在安装时容易磕碰到输入轴齿和油泵斜齿轮的问题。对工厂来说,解决了人工装配中的难点痛点,也节省了成本,提升变速箱的装配质量和效率。从自动装配行业来说,未来发展趋势是向着无人的方向发展,为以后提高变速箱装配线的自动化水平提供参考。

双离合器变速箱换挡集成学习控制器设计及分析

为了提高车辆运行的稳定性,设计了一种双离合器DCT变速箱换挡集成学习控制器。基于预测模型建立MPC控制器,以补偿转矩保障转速精准追踪。研究结果表明,在0.11 s时DCT开始出现升挡转矩相,车速整体维持稳定变化的态势,车辆冲击度的最大值是4.8 m/s^(3),有利于大大提高换挡的稳定性。相比其他控制方法,基于经验知识MPC换挡方案获得更优的平顺性控制效果,滑摩功也发生降低,可以更快完成动力响应。该研究有助于提高汽车自动控制,为后续的换挡控制奠定理论基础。

预选挡对双离合变速器敲击动力学影响的试验研究

搭建可模拟发动机转速波动的变速器敲击动力学试验台架,采集双离合变速器(dual-clutch transmission, DCT)的壳体振动和齿轮瞬时转速信号,研究不同预选挡位下DCT变速器的敲击响应和齿轮系统动力学随输入角加速度幅值变化的演变规律。根据齿轮系统间隙非线性动力学模型的计算结果和齿轮啮合基本定律,提出了一种基于齿轮特征频率角加速度幅值特性的齿轮运动状态判定准则。台架敲击试验结果表明预选挡显著改变DCT变速器的敲击响应和齿轮副动力学行为,当输入角加速度幅值增加到某一数值时,DCT变速器敲击响应发生向上跳跃现象,主动和被动子变速器之间产生明显的低频动力学耦合,承载齿轮转速信号呈现显著的多谐波非线性特性。根据提出的齿轮运动状态判定准则判断跳跃突变后的承载齿轮副发生齿面分离和敲击现象,动力学突变后的动力学耦合导致DCT变速器的敲击响应急剧恶化。最后,在整车上验证了台架试验的动力学耦合和敲击响应突变现象。

基于液压系统的自动挡变速器的故障分析与处理

本文阐述了自动变速器液压驻车系统的工作原理,利用CANape软件对双离合器自动变速器由液压驻车系统和液压控制模块引起的常见的故障进行详细分析,并针对故障提出可行的解决措施,为解决自动挡变速器常见故障等问题提供了理论和实践依据。

自动变速器牙嵌式离合器进挡概率研究与应用

文章以某9挡自动变速器的牙嵌式离合器为研究对象,建立了离合器结合各阶段的动力学模型。根据长短齿设计特征,分别计算无任何齿形接触、长齿接触长齿、长齿接触短齿、长齿接触长齿和长齿接触短齿同时发生四种场景在不同初始速差条件下的进挡概率。考虑随机齿形接触位置的终止速差,计算得到牙嵌式离合器进挡的最优速差,可用于滑行降挡最优进挡策略的制定,提升换挡质量。选取实车滑行五挡降四挡工况,进行进挡概率校验,结果和理论计算概率相符合。

双离合自动变速器台架路谱试验方法研究

介绍了一种基于双离合变速器的路谱采集及台架试验应用方法,通过前期实车采集路谱数据、转化合成台架路谱测试方法、开展动力总成级的台架路谱测试,对双离合自动变速器质量进行评价。试验结果显示,台架路谱测试工况达成与整车测试基本一致,针对硬件验证可对整车开展有效替代。

基于灰色关联和模糊理论的双离合变速器车辆起步品质评价

针对目前双离合变速器(DCT)车辆起步评价以驾驶员主观评价为主,主观性过强导致评价不准确的问题,基于灰色关联分析法和模糊综合评价法建立了DCT车辆起步品质评价体系。考虑动力性、舒适性和经济性,选取起步响应延迟时间、起步加速时间、起步加速度峰值、发动机转速波动以及冲击度作为评价指标;使用变异系数法计算了各指标的客观权重,并基于灰色关联分析法明确了各指标与起步品质的关联度排序,验证了权重计算结果的准确性与可靠性;最后,基于模糊综合评价法建立起步品质评价模型并进行客观评分,使DCT车辆的起步品质评价更加客观真实。

P2.5-PHPS发动机至混合驱动模式切换过程动态协调控制研究

搭载双离合变速器的P2.5插电式混合动力系统传动效率高,换挡和模式切换过程无动力中断,应用前景广阔,但其模式切换过程由于发动机与电机的扭矩响应特性存在差异,扭矩波动明显,影响驾乘体验。针对上述问题,提出一种发动机驱动至混合驱动模式切换的协调控制策略,以搭载双离合变速器的P2.5插电式混合动力系统为研究对象,对其发动机至混合驱动模式切换过程进行分析,依据分析结果将系统模式切换过程划分为4个阶段。在此基础上,基于PID反馈原理控制动力源的实际输出转矩并通过控制加速踏板开度变化率限制发动机的扭矩变化率,利用驱动电机扭矩快速响应的优势补偿发动机扭矩响应滞后来降低输出扭矩波动,制定模式切换过程多阶段双动力源扭矩协调控制策略。搭建基于P2.5插电式混合动力系统的发动机至混合驱动模式切换动态协调控制仿真模型。仿真结果表明,模式切换过程无动态协调控制策略的最大冲击度约7.1 m/s^(3),策略下最大冲击度约1.78 m/s^(3),减小74.9%,表明所提出的控制策略能有效减小模式切换过程冲击度,提高整车平顺性。

双离合变速器动力系统加速工况扭振和敲击的被动控制措施研究

为研究不同预选挡机制下的双离合变速器敲击特性和控制方法,分别在整车和敲击台架上评价变速器的敲击主客观表现和随角加速度变化的敲击灵敏度;其次,根据敲击灵敏度,整车扭振响应和敲击主客观结果的相关性提出了一种定量评价变速器输入轴角加速度的无敲击扭振阈值。在相同整车上分别评价不同扭振和敲击的被动控制措施,包括离合器式扭转减振器,双质量飞轮式扭转减振器,以及离合器微滑摩和离心摆吸振器与扭转减振器的组合方案。台架试验结果表明预选挡显著改变双离合变速器的敲击特性,在某一激励幅值时产生敲击突变现象。整车试验结果表明离合器式和双质量飞轮式扭转减振器无法满足双离合变速器加速工况无敲击扭振阈值要求,在低转速段产生明显敲击;离合器微滑摩和离心摆吸振器与扭转减振器组合方案的输入轴角加速度幅值满足无敲击扭振阈值要求,消除了双离合变速器动力系统存在预选挡时的加速敲击。

考虑DCT车辆起步过程离合器接合稳定性的双质量飞轮参数优化

在车辆起步过程中,发动机输出转矩波动会导致离合器接合不稳定,从而影响整车动力传动系统的平顺性。双质量飞轮(dual mass flywheel,DMF)可减小发动机转矩波动对离合器及整车动力传动系统的影响。针对起步过程离合器接合不稳定影响整车平顺性的问题,以双离合器自动变速器(dual clutch automatic transmission,DCT)车辆为研究对象,研究了DMF的刚度、阻尼和初级与次级飞轮惯量比对DCT车辆起步过程离合器接合稳定性的影响,并建立了以离合器黏滑比和整车冲击度为目标函数的多目标优化模型,利用遗传算法对模型进行优化,得到了使离合器接合稳定性提高且整车冲击度明显降低的DMF最优参数组合。