【作者】 张飞铁；

【导师】 周云山；

【作者基本信息】 湖南大学 ， 车辆工程， 2008， 博士

【摘要】 汽车技术正朝着节能、环保、安全舒适的方向发展,新技术层出不穷。在汽车变速器方面,20世纪60年代,就出现了对传统离合器与手动机械变速器的半自动变速器,随后发展成为目前市场上的AMT技术。自20世纪70年代起,由液力变矩器和行星齿轮构成的自动变速器(AT)的性能得到迅速发展,成为目前美国、日本轿车的主导产品。20世纪80年代发明了金属带,解决了皮带摩擦传动的本质缺陷,于是机械无级变速器(CVT)在变速器的市场份额中迅速扩大。在AMT基础上发展的双离合器变速器(DSG),由于可以弥补换档时动力中断的固有缺陷,也成为汽车自动变速器的重点发展方向。在我国发展自动变速器,其中AMT、AT、CVT、DSG的任何一种,都有一个共性的关键技术问题,就是起步离合器的控制问题。本文重点研究CVT湿式离合器控制问题,内容包括:离合器机械传动与液压执行机构的动态建模;湿式离合器片的摩擦特性;离合器接合过程的理论分析;满足产品需要的电子控制装置及工程化控制软件。所取得的主要研究成果为:1)根据湿式离合器机械传动、液压执行机构工作原理,结合发动机和液力变矩的数字模型,建立了湿式离合器状态空间模型X = AX(式2.26),为离合器结合过程动态分析和控制策略优化奠定了基础。通过对湿式离合器典型工况的仿真表明:当摩擦片的摩擦系数具有正斜率特性时,其传递的转矩是收敛的,具有负斜率性,其传递的转矩是发散的,这与实际测试结果是一致的。仿真分析还看出:离合器压力波动对离合器传递转矩的特性影响较大,在特定条件下可能出现共震现象,导致液力变矩器涡轮、主动摩擦片与从动摩擦片一起振动。2)开发了起步离合器电子控制装置,包括硬件、软件两部分。软件由底层驱动、操作系统和用户软件构成,其中用户软件由液压执行机构的标定和基于控制理论提出的控制算法组成。硬件部分包括压力传感器、转速传感器、档位开关、油温传感器的设计与选型,高速开关阀的驱动电路设计。高性能高可靠性驱动是离合器电子控制硬件设计的关键,本文通过仿真分析研究了高速开关阀的电磁特性,奠定了高速开关阀驱动电路设计的理论基础,并设计了高端驱动低端电流传感、低端驱动高端电流传感、高端驱动高端电流传感三个方案。大量的台架和路面试验证实,所设计的高端驱动高端电流传感驱动电路全面达到CVT使用要求。3)研究了摩擦片摩擦系数的影响因素。测试了同一条件下CVTF-EXx、CVT-F-x、EZL-7xx三种油液的摩擦系数;采用CVTF-EXx油液研究温度对摩擦系数的影响,测试数据显示温度越高,摩擦系数越小,并拟合了摩擦系数随温度变化的特性曲线;测试了离合器压力对摩擦系数的影响,结果显示压力的变化对摩擦系数的影响不大;测试了滑摩转速对摩擦系数的影响,发现滑摩转速小于100r/min时,摩擦系数随滑摩转速急剧上升,大于100r/min后,反而下降,到达200r/min后,摩擦系数趋于稳定。4)根据湿式离合器实际接合过程,提出各阶段的控制目标及评价指标。起步离合器接合过程的四个阶段为:空行程阶段、建压阶段、滑摩阶段、同步接合阶段。研究发现,空行程阶段对起步性能并无影响,要尽快结束;建压阶段离合器压力与充油时间影响最大,直接决定起步的快速性;滑摩阶段决定起步的平顺性,摩擦系数对这一过程影响很大;同步接合阶段不产生滑摩功,并且接合快慢对车体冲击度影响不大,需快速接合。根据控制目标及评价指标,开发了湿式离合器接合过程模糊控制算法,各类试验证实了算法的有效性。5)湿式离合器的起步试验伴随CVT控制软件的调试,历时二年,经过台架试验,新疆吐鲁番环境温度高达60℃的高温标定试验,昆仑山口海拔高度4647米的高原标定试验,以及黑河最低温度为-32℃严寒标定试验,所取得的研究成果对离合器软件开发和标定流程具有很好的借鉴意义和工程应用价值。6)自动变速器起步离合器的标定是软件产品开发的核心技术。本文基于离合器常态特性标定了起步离合器的基本模型;根据汽车的极限工作环境导致特性变化,标定了影响基本模型的环境修正模型;通过疲劳寿命试验测试了核心部件的衰减特性(如摩擦片磨损、离合器间隙变化、液压阀磨损、电磁线圈磁力特性衰退等),标定了修正基本模型的衰减特性修正模型;在三个标定模型得基础上,加上非正常驾驶的安全保护措施,成功地解决了国产CVT进入市场的关键技术问题,为中国汽车电子的自主开发贡献了一份力量。更多还原

【Abstract】 Automobile technology is developing in a direction of saving more energy and friendly environment. New technologies are emerging. For the transmission system, from the 1960s, semi automatic mechanical transmission has been made which improved from mechanical clutch and manual transmission into AMT now. Since the 1970s, Automatic transmission (AT), which is composed of torque converter and planetary, is greatly improved. AT is at a dominant position in the market of the United States and Japan. In 1980s, due to metal belt invented, the essence problem of strap transmission was resolved which made rapid increase of market sales. The direct shift gearbox (DSG), developed from ATM, will be one of the major auto transmission to be developed in the future. To develop transmission system in China, there is a common key technology among AMT、AT、CVT、DSG which is wet clutch starting control. The key technologies of CVT wet clutch control researched in this paper include: dynamic models of mechanic transmission and hydraulic system of transmission, the friction characteristics of wet clutch, theory analysis of engaging process of clutch, ECU and engineering software for products. The research achievements are shown below.1) Based on mechanic theory, hydraulic system theory and mathematics model of engine and torque converter, the status-space model X = AX(formats 2.26) is established. And this is the base of engaging process analyze and control strategy optimization. From the simulation results for some working conditions, we can see that, for coefficient of friction with positive slope, the torque is convergence and for the coefficient of friction with negative slope, the torque is the divergence, which is according with actual tests. We can also see that the clutch pressure fluctuations have great influence on torque transfer. The whole system is oscillating with the fluctuated clutch pressure under certain conditions. That is to say, the turbo、primary friction plates and slave friction plates oscillate together.2) The wet clutch of electronic control system is developed which includes hardware system and software system. Software system is composed of two parts: one part is the control method of the hydraulic components, the other is the system control method based on control theory. Pressure sensors, speed sensors, shifting sensors and the oil temperature sensor characteristics are introduced. The drive circuit design of high-speed on-off valve is the key of the control system. The high-speed on-off valve’s characteristics is analyzed and simulated, which is the foundation of the drive circuit design of high-speed on-off valve. Driving circuit is designed using three different methods which are the high-side drive and low-side current sensing, low-side drive and high-side current sensing, high-side drive and high-side current sensing. The design of high-side drive and high-side current sensing can meet the requirement of test bench testing and road testing.3) The factors of friction of clutch are researched. A test bench is built and friction coefficient of CVTF-EXx, CVT-Fx,and EZL-7xx three types of oil is tested. By using CVTF-Exx, the impact of oil temperature on friction coefficient is studied. Test data show that when oil temperature is becoming higher, the value of friction coefficient will be smaller. With the test data, the curve of friction coefficient with the temperature is fitted. Researching results of the impact of clutch pressure on the friction coefficient show that the changes of the oil pressure have little impact on friction coefficient. In the study of the impact of temperature on the friction coefficient, we have found that before sliding speed reaches 100r/min, the coefficient of friction rises sharply, but declines after 200r/min, then stabilizes.4) According to the actual process of the wet clutch engagement, we give object control and evaluation for four stages: free-stage, oil-filled stage, slipping-stage and synchronous engaging-stage. The study found that free-stage has no effect on performance, to be end as soon as possible; the pressure and oil-filling time in oil-filled stage are the key, which directly determines the speediness of the starting; slipping-stage decides the comfort of the starting, and the friction coefficient is important for this stage, synchronous engaging-stage don’t product slipping loss, and don’t impact the jerk of the vehicle, needing to be finished fast. According to control object and evaluate guidelines, the fuzzy control algorithm is developed and different experiments verify the correction of algorithm.5) With the debug of CVT control software, the experiment is finished in two years which includes test bench experiment, 60℃high temperature test in Tulufan of Sinkiang province, 4647 meters high altitude test at Kunlun mountains, as well as the minimum temperature of -32℃test at Heihe. The achievement is useful for software development of clutch control and calibration flow.6)Calibration of wet clutch is the key technology of software product. The basic model of starting wet clutch is calibrated basing on common characteristics. The revised model of circumstance is calibrated basing on asperity working conditions of vehicle. The attenuation model is calibrated basing on key parts attenuation characteristics through fatigue testing (such as, clutch worn, gap between clutch plates, hydraulic valve worn, attenuation of elec-magnetic valve). On the basis of the three calibration work and safety modes, the key technology problems of product are resolved in this paper and this paper contributes a support to the self-design auto electronic technology.更多还原