【作者】 梁艳红；

【导师】 吕新民；

【作者基本信息】 西北农林科技大学 ， 机械设计及理论， 2009， 硕士

【摘要】 工程车辆工作环境极其恶劣,负载变化范围很广,为了适应外载荷急剧变化,需要不断变换挡位。然而,频繁换挡增加了驾驶员劳动强度,驾驶员容易疲劳,导致工作效率降低,工作质量下降。因此,为了提高工程车辆传动效率、改善工程车辆操纵性能、提高作业生产率、减轻驾驶员劳动强度,必须采用自动变速技术。对装载机的动力传动系统的组成及各部件的性能进行了分析,运用最小二乘法对发动机和液力变矩器的相关特性进行拟合,建立了发动机速度特性与变矩器原始特性的数学模型。分析发动机与变矩器的共同工作的输入、输出特性。并在原有发动机与液力变矩器匹配理论的基础上,提出了优化匹配的概念,以装载机的动力性能为目标,建立发动机与液力变矩器的优化模型,最后选取评价参数对匹配方案进行了分析评价。将发动机和液力变矩器作为一个整体考虑车辆的动力性,通过分析它们的共同工作特性,提出了以油门大小、泵轮转速和涡轮转速的三参数自动变速策略。通过计算不同油门特性下装载机的牵引特性得到在一定的油门开度下,各挡位不同油门状态时的换挡点的参数,然后将不同油门开度下的同一挡位的换挡点参数,在坐标图上做出可得该挡的换挡曲线。本文通过曲线拟合,确定各个挡位的换挡规律方程。这样,在实际工作过程中,同样通过检测发动机转速(变矩器泵轮转速)、车速(或变矩器涡轮转速)和相对应的油门开度,确定对应挡位下装载机的工作点,该点与该挡的相应换挡曲线比较确定范围决定是否换挡。建立了装载机动力学方程。最后在Matlab/Simulink图形建模技术的支持下,建立了发动机、液力变矩器、变速器、整车模型。通过对装载机换档逻辑的研究,利用仿真软件MATLAB/Stateflow建立了最佳换档规律的换档过程仿真模型。并对其进行了模拟分析,验证了方案的有效性。仿真结果表明,本文建立的仿真模型和设计的换挡规律是合理的,可行的。更多还原

【Abstract】 The working condition of loader is extremely poor. The range of load is very wide. In order to adapt to rapidly changing external load, it need drivers shift frequently. However, the manual shift is heavy. And frequent shift will increase the labor strength of the driver. So drivers feel tired easily. This will lead to lower work efficiency. Therefore, in order to improve the transmission efficiency, the handling performance and the productivity of the loader, and reduce labor intensity of the driver, techniques of automatic shift must be used.Matching between the engine and hydraulic toque converter has important influence on each full playing performance and wheel loader full playing performance .This paper analyzes the disadvantages of traditional matching through the input character of engine and torque converter working together. Base on the principle of matching between the engine and hydraulic toque converter, the optimum model was presented. In this model, numerical approximation of some characteristics of diesel engine and hydraulic toque converter were carried out by the method of least square, and wheel loader power characteristic was taken as object. Several detailed evaluation parameters are used to be analysis and compared by traditional matching and optimal matching. Besides, the theory is proved by an example, and the practical guiding significance is presented.The engine and torque converter were considered as a new power. By analyzing the characteristics of their common work, a shift schedule of three parameter has proposed with position of the throttle,the rotational speed of pump and the rotational speed of turbine,and has received shift forms and made the automatically controlled scheme. The output of the engine changes with the throttle which was actuated by the operator. To calculate more easily, all the research and analysis here are based on the fixed throttle open angle, and the engine works steadily. Under fixed throttle open angle and engine works steadily, count out each parameter under different throttle state. The curve can be get by the same gearshift, then, the formula can be get. In actual, the shift is decided by the engine speed, throttle open angle and the rotational speed of turbine.The dynamics equation of the vehicle transmission has set up. Have set up models of the engine,hydraulic torque converter,gearbox, and vehicle load by Matlab/Simulink figure modeling technology. And simulation analysis carried out to verify the effectiveness of the shift schedule. Simulation results show that the established simulation model and shift schedule is reasonable and feasible. Verify the effectiveness of the shift schedule.更多还原