【作者】 张树忠；

【导师】 邓斌；

【作者基本信息】 西南交通大学 ， 驱动技术与智能系统， 2011， 博士

【摘要】 随着世界范围内工业技术的迅速发展,能源短缺和环境污染问题日趋严重。液压挖掘机由于其用量大、耗油高、排放差,已逐渐成为人们普遍关注的主要对象之一。日本神钢公司研究结果表明传统挖掘机的液压系统效率仅为30%左右,表明对液压系统进行改进具有较大的潜力,是液压挖掘机节能研究的一个重要方向。液压挖掘机前端工作装置质量重、惯性大,在下放过程中,重力势能和动能绝大部分在主阀的节流口转化为热能；上车的回转质量大,工作频繁,用于回转的能量最后几乎全部变成热能。上述两种情况不仅造成了能量的浪费,而且使液压系统温度升高,为了降低油温进行散热,又将引起附加能量消耗。为了解决这一问题,应考虑开展能量回收。主要研究内容如下：以某公司7吨和20吨级液压挖掘机为研究对象,围绕其液压系统的可回收能量分布,分别建立执行机构、液压系统模型以及系统能量损耗模型,进行仿真研究,开展7吨级液压挖掘机动臂和斗杆快速下放以及20吨级挖掘机典型挖掘循环工况的可回收能量实验研究,得出液压挖掘机在工作过程中系统各部分的能量消耗情况,在此基础上挖掘液压系统的节能潜力,找出当前条件下切实可行的节能方法。基于传统动臂液压系统能量损耗分析以及液压式能量回收与及电力式能量回收系统的比较,根据进出口独立节流调节、流量再生和能量回收三种提高液压系统效率的方法,提出了变压利用和直接利用两种新型动臂节能系统,阐述了其运行机理和技术优势;通过静态分析,阐明了新系统的节能方法和所节约能量的源头,对所提出的两种动臂节能方案进行了综合比较,选取直接利用方案作为主要研究对象。系统地提出了新型动臂能量回收系统的设计步骤和方法。以7吨级液压挖掘机为设计对象,通过动臂快速升降实验进行对象分析,制定系统控制策略,进行主要元件参数匹配,建立系统数学模型,开展动态特性分析,得出影响其动态性能的主要因素。以7000kg的质量块作为负载,对系统的运行过程进行分析,结果表明系统在恒定负载下运行良好。根据动臂系统负载变化频繁且幅度大的特点,建立了执行机构模型,对液压系统进行比例化改造,采用PID控制器对各执行元件的运行进行精确控制。将能量回收系统应用于比例控制的挖掘机上,通过动臂快速升降,典型挖掘循环(包括空载和带载)工况下的仿真研究,来分析系统的节能性和控制性,结果表明,新型动臂节能系统运行良好,节能效果显著。通过能量回收系统试验,测试系统能量回收效果和控制性能,验证其运行机理。根据实验结果和仿真分析,对动臂节能系统提出了分阶段控制,在动臂下放加速阶段采用节流控制,而后采用调节能量回收系统中的变量泵排量进行控制,提高马达—变量泵运行的平稳性。更多还原

【Abstract】 Currently, energy saving has become one of the most important world problems because of the energy crisis and the resulting increase of fuel cost. Only 30% of the hydraulic system input power is utilized in a conventional type excavator. Many proposals for energy saving in oil hydraulic systems had been discussed. One of the most important research directions of improving hydraulic system efficiency is to reutilize the gravity potential energy and kinetic energy.The hydraulic excavator’s massive work device, when lowered, generates a great deal of force on the rod end of the boom cylinder. In turn, this exerts huge forces on the fluid and blind end of the cylinders. Fluid forced from the boom cylinder at several ten bars, in most instances, throttles through valves and returns to the reservoir. The result:potential of energy is lost as heat when the boom lowers. Also, a large amount of energy is wasted during lowering of stick and bucket and braking of upper structure. To resolve this problem, it is necessary to reutilize the potential energy and kinetic energy.The main contents are briefly introduced as following:Base on the distribution of recoverable energy in 7-ton and 20-ton excavator hydraulic system, multi-body dynamics, hydraulic system and system energy loss model is developed; the potential recoverable energy during the typical working cycle is calculated. Then the boom fast down and up experiment of 7-ton excavator and typical working cycle experiment of 20-ton excavator are carried out. After analysis, the results present the amount of the recoverable energy distributions and find the way to improve the efficiency of the hydraulic system.The inefficiency of the traditional boom system is analyzed. And hydraulic energy recovery is compared with electrical energy recovery system. According to the separate meter-in meter-out, flow regeneration and hydraulic energy recovery technology, two innovative boom energy saving systems are brought forward. Firstly the principle of the system and the advantage compared with traditional hydraulic boom system are presented. Then through theoretical analysis, the method of energy saving and the sourse of the saved energy are described. Finally, comprehensive comparison between the two energy saving systems is maked and direct use system is selected as the main research object.The design procedures and method for the innovative energy saving system are presented systematically based on the above study. According to the analyses of the design object, the corresponding control strategy is developed, and the components are parameter matched. Then a hydraulic energy saving system for 7-ton excavator is designed using these rules. And the designed system is simulated in the built model under a constant mass load. The simulation results show this system works well.Due to the load of the boom system varies frequently and at large amplitude, mechanical model of work set is constructed, then the hydraulic system of excavator is proportionally reconstructed and adopted PID controller to accurately control the motion of each work component. Then the energy saving system is applied to the proportional excavator. After the simulation research of three operating mode (boom fast down, typical work cycle without and with load), the result shows the innovate energy saving system runs well and has good energy saving effect.Energy saving system experiment is carried out to test and investigate the energy saving effect and controllability, vertify the working principle. On the basis of the experitment result, the energy saving system is revised. During the accelerating period of boom down, restriction control is adopted. And then system is controlled by adjusting the variable disaplacement pump of the energy saving system.更多还原