【作者】 赵国明；

【导师】 郝万军； 甄建军；

【作者基本信息】 吉林大学 ， 工程硕士（专业学位）， 2016， 硕士

【摘要】 热平衡性能是液压挖掘机的一个重要性能,直接影响着整机的使用。目前国产挖掘机生产厂家都在小型液压挖掘机上投入大量的精力进行研究,以期能在市场上占有一席之地。挖掘机冷却不良导致的温度过高,会使得发动机的热效率降低、油耗升高和尾气排放变差,同时由于温度过高会引起润滑效率降低,严重时可能导致机器磨损加剧而缩短寿命。本文结合市场发生的挖掘机高温故障现象,通过理论分析、现场调查、设计改善等,对冷却系统主要组成部品对热平衡性能的影响进行了研究。首先,探讨冷却系统的主要组成部分并以此详细分析可能影响热平衡的因素。热平衡性能主要决定因素是冷却系统,对于挖掘机而言,其冷却系统主要包括散热器、冷却风扇、水泵、节温器等。目前的液压挖掘机都设有系统自动检测高温报警装置,出现报警时,我们首先要对报警故障进行实际确认,排除误报警。引起高温的原因,简单来说主要有,散热器堵塞、冷却液不足、风扇故障、散热器周边密封不良、节温器故障等,液压油温度过高或与散热器串联的空调冷凝器温度过高也可能是导致故障的原因。然后,根据市场反馈对故障挖掘机进行现场对策处理。市场上的挖掘机在发生高温故障的时候可能并不是在一年当中温度最高的时期,这表明外界非环境温度的因素对机器高温有重大的影响,而这个因素就是容易被发动机吸风风扇吸入散热器芯体中的杨絮和枯草、枯叶。通过实际的调查,发现在挖掘机部品未收损坏的前提下,散热器堵塞是导致整机温度过高的主要原因。这也说明了散热器密封与散热器防尘的重要性。最后,对影响效果较大的散热器、冷却风扇、发动机舱等进行了改善设计,通过对新散热器、新冷却风扇、新发动机舱的热平衡测试,验证了各部分对冷却系统性能的影响。通过在同一台挖掘机上进行改善验证后发现,相同转速下,在不改变风扇和发动机舱进出风面积的时候,仅更换散热面积加大的散热器对冷却效果的改善较小;在更换风量加大的冷却风扇之后,水温和油温的热平衡温度有了较大的降低,说明加大通风量可以更有效提升冷却系统的换热量;在加大了发动机舱的进风孔和出风孔面积后,测得整机热平衡性能在改善风扇的基础上又有所提升,说明通过增大进出风面积的方法能有效提高散热系统的性能。更多还原

【Abstract】 Heat balance is an important performance of hydraulic excavator,which affects the usability of the machine.At present, domestic excavator manufacturers all invest a lot of energy on small hydraulic excavator in order to gain a foothold in the market. High temperature will make lower thermal efficiency,higher fuel consumption and bad emissions,also may cause lower lubrication efficiency,which will shorten the machine’s life.In this paper,we researched the main parts of cooling system,combined with the market survey.Firstly,we did research to the main parts of the cooling system.For the excavator,its cooling system mainly includes radiator,cooling fan,water pump,thermostat,etc.Nowdays,almost all hydraulic excavators are equipped with automatic alarm device,when alarmed,we should confirm first in case of fault.In simple words,the causes of high temperature including blockage,less of cooling liquid,poor sealing of the radiator and so on,In addition,the overheat of hydraulic oil and air conditioning condenser also may be the cause.Secondly,according to the market feedback,we dealed with the overheat machines in the spot.In general,the malfunction is not always occur in the period of maximum temperature,this shows some external factors may have a significant impact on the machine,which are likely to be flocculant and grass and leaves sucked by fan.After investigation, the radiator blockage was found the main cause of overheat,and this also proves the importance of sealing and dustproof.Finally,we tested the heat balance of improved radiator, cooling fan and hood on the same excavator.According to the test results,if the increase of the radiator cooling area is small,the improvement is small too,while the improvement of fan has more progress.Also the increase of ven makes great improvement.更多还原