【作者】 李晶洁；

【导师】 贾跃虎；

【作者基本信息】 太原科技大学 ， 机械电子工程， 2010， 硕士

【摘要】 随着工业技术的迅速发展,能源短缺问题日趋严重。装载机在使用过程中经常出现油温过高现象,而液压系统的油温过高会造成装载机操作不灵活、铲斗举升和翻转困难,以及工作压力降低等故障,已逐渐成为人们普遍关注的对象。目前,国内装载机工作装置液压系统都是由定量泵驱动,在转速相同的情况下,定量泵的输出流量始终保持不变,不能适应负载的变化。而装载机工作装置负载变化频繁且变化范围较大,导致液压系统存在较大的溢流损失。因此,由定量泵驱动的装载机工作装置液压系统有逐渐被节能型的新型液压系统取代的趋势。本文从液压泵与负载匹配的角度出发,将负载敏感变量泵应用到装载机工作装置液压系统的设计中。本论文以856Ⅲ轮式装载机工作装置液压系统为研究对象,主要从装载机工作装置液压系统节能角度出发,从理论分析和联合仿真分析两个方面展开研究,主要工作如下:(1)以现行装载机的代表856Ⅲ轮式装载机为研究对象,分析装载机工作装置现行液压系统在一个标准工作循环过程中处于不同工况时的功率损失。结果证明,定量泵不能根据负载的变化输出压力和流量,装载机工作装置现行液压系统存在较大的溢流损失、中位卸荷损失和节流损失。(2)为了解决装载机工作装置液压系统中溢流损失、节流损失和中位卸荷损失较大的问题,本论文以856Ⅲ轮式装载机的设计任务和主要技术参数为依据,设计了装载机工作装置负载敏感液压系统。(3)利用功率键合图法建立装载机工作装置负载敏感液压系统的数学模型,为使用AMESim仿真软件建立装载机工作装置液压系统的仿真模型做理论基础。(4)装载机在运动过程中,随着运动状态和速度不断变化,负载阻力及工作装置重力的作用力臂也随之不断发生变化,最后导致铲斗液压缸和动臂液压缸所受的作用力不断发生变化。因此,要想真实模拟装载机的动态特性需要将AMESim和ADAMS进行联合仿真。本论文利用AMESim仿真软件建立装载机工作装置负载敏感液压系统及其各主要液压元件的仿真模型。分析各主要液压元件的建模依据,对各主要液压元件进行静动态特性分析,并将仿真结果与各主要液压元件样本提供的静动态特性进行对比,验证各主要液压元件仿真模型建立的正确性。(5)利用ADAMS仿真软件对装载机工作装置进行动力学仿真分析。首先,测量856Ⅲ轮式装载机工作装置的尺寸,利用三维建模软件PRO/E建立装载机各零部件的三维模型并根据实际连接情况进行装配。其次,利用MECH/Pro将装配好的装载机三维模型导入到动力学仿真软件ADAMS中,并添加约束和负载,以便对装载机的动臂液压缸和铲斗液压缸在一个标准工作循环过程中的受力情况进行接近实际的仿真分析。(6)以装载机工作装置液压系统的AMESim仿真模型为主体,将建好的ADAMS动力学仿真模型导入到AMESim仿真模型中,然后建立装载机工作装置现行液压系统和负载敏感液压系统的联合仿真模型。通过仿真分析装载机工作装置负载敏感液压系统在一个标准工作过程中主要参数的变化,并对比分析装载机工作装置现行液压系统和负载敏感液压系统在一个标准工作循环过程中的功率损失。最后通过将仿真结果与理论计算结果对比,验证联合仿真模型建立的正确性。结果证明:装载机工作装置负载敏感液压系统能够根据负载的需求提供泵的输出压力和流量,液压系统不会出现溢流损失和中位卸荷损失,只存在少量的节流损失,比较节能。更多还原

【Abstract】 With the rapid development of industry, the problem of energy shortage is on the rise.Loaders often have the problem of excessively high oil temperature.Too high oil temperature of hydraulic will cause many failures with the result that the operation of loader is not flexible,the lifting and turning of bucket is difficult and the working pressure of hydraulic becomes reduced and so on,which have gradually become the object of common concern.At present,the hydraulic system of domestic loader is driven by the fixed displacement pump,when the engine speed is fixed,the flow rate of fixed displacement pump remains unchanged.And the load of loader changes frequently and varies greatly,which may result in much overflow loss of the hydraulic system of loader.The hydraulic system of loader driven by the fixed displacement pump will be replaced gradually by energy-saving hydraulic system,which is a tendency.This paper applies load-sensing variable pump to the hydraulic system of loader considering the matching of pump and the load.Taking the 856Ⅲwheel loader as an example,focusing on the energy-saving characteristic and controllability of the hydraulic system of loader,this paper mainly does some theoretical analysis and co-simulation.The main work is summarized as below:Firstly,taking the 856Ⅲwheel loader as representation,this paper analyses the power loss of the existing working device hydraulic system of loader during the course of different operating conditions.The result indicates that the output pressure and flow rate of the fixed displacement pump can not change according to the load.The existing working device hydraulic system of loader has much overflow loss, unloading loss and throttling loss.Secondly,for reducing the overflow loss,unloading loss and throttling loss of the existing working device hydraulic system of loader,this paper designs the load-sensing working device hydraulic system of loader according to the design task and the main technical parameters of 856Ⅲwheel loader.Thirdly,this paper establishes a mathematical model for the load-sensing working device hydraulic system of loader with the power bond method,which provides a basis for the AMEsim simulation model of the load-sensing working device hydraulic system of loader.Fourthly,when loader is moving,the state of motion and speed are constantly changing which cause the torque arms of the load force and the working device’s gravity are also constantly changing,leading to the load force of the hydraulic system that is exerted on the hydraulic cylinders constantly changing. Therefore, it is necessary that we simulate dynamic characteristics of the loader with the co-simulation method with AMESim and ADAMS.This paper establishes AMESim simulation models for the working device load-sensing hydraulic system of loader and its main components.The principles of the main components are analyzed,and the static and dynamic characteristics of the main components are analyzed,and then the static and dynamic characteristics are compared between the results of simulation and the results provided by sample,the results show that the AMESim simulation models of the main components are right.Fifthly,this paper does some dynamic simulation analysis for the loader working device with the software ADAMS.First of all,based on the actual size,the three-dimensional models of components of the loader working device are built with Pro/E,and are assembled according to the actual connecting situation.Secondly,the three-dimensional model of loader working device is passed to the dynamics simulation software ADAMS,and then add the constraint and the load force for the ADAMS model of the loader working device in order to analysis the force that being exerted on boom cylinder and bucket cylinder during the course of different operating conditions.Sixthly,this paper views AMESim model of the working device hydraulic system of loader as the main body,and passes ADAMS model of the working device to AMESim model,and then establishes the co-simulation models for the existing working device hydraulic system of loader and the load-sensing working device hydraulic system of loader.The main parameters of the load-sensing working device hydraulic system of loader are simulated and analyzed,and the power losses are compared between the existing working device hydraulic system of loader and the load-sensing working device hydraulic system of loader with the co-simulation models.Finally,for verify the correctness of co-simulation models,the paper compares the simulated results and the theoretical results.The simulation results show that the load-sensing working device hydraulic system of loader can provide the output pressure and flow rate according to the needs of the load.The load-sensing working device hydraulic system of loader has less throttling loss and is more energy-efficient.更多还原