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9-DA468型发动机曲轴加工工艺与专用机床夹具设计【长430】(含CAD图纸和说明书)

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长430 DA468 发动机 曲轴 加工 工艺 专用 机床 夹具 设计 430 CAD 图纸 说明书
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附录AInvestigation on Pressure Impact in ConcretePumping Hydraulic System Abstract:The pressure impact in hydraulic systems of such concrete pumping machinery as trailer concrete pump,transported concrete pump,and truck mounted concrete pump,is a key factor affecting their reliability and usage lifeBased on the pressure forming principle of the oil in a hydrostatic closed pressure chamber,the mechanism of producing pressure impact is analyzed synthetically,and the theory that oil flow matches requirement, and pump displacement control harmonizes valve shifting time control,to mitigate pressure impact,is put forwardThe quantitative controlling parameters about shifting time and displacement control are introduced to realize accurate controlThe experiment investigations of pressure impact property and its control are carried through on an experimental system which is able to simulate concrete pumping conditionThe basic law that pressure impact and controlling parameters vary with working condition respectivelyThe feasibility and validity of the technology proposed in this paper to control pressure impact are confirmed.Keywords: Pressure impact;Hydraulic system; Concrete pumping machinery1 IntroductionDuring working process of such concrete machinery as trailer concrete pump,transported concrete pump,and truck mounted concrete pump,two oil cylinders drive two concrete delivery cylinders respectively,and quickly switch direction with the possible highest frequency of more than 30 times per minute,which generates serious hydraulic impactIt is an important factor resulting in bad performance and low use reliability of the machine, and vibration,noise and overheating etcso its a key of improving concrete pumping machinerys reliability to gain a mastery of pressure impact property in concrete pumping hydraulic system and its controlling technologySuch technological measures as follows were taken to reduce pressure impact:(1)installation of a hydraulic accumulator or unloading valves,(2) change of sliding spools structure,(3)control of the switching speed of sliding spool,etc1Though these measures play an important role in absorption of pressure surges,there are obvious limitations, and they are passive measuresLiterature.2. investigated the switching process of concrete pumping hydraulic system,and put forward active measure of regulating oil pumps displacement to reduce pressure impactLiterature3studied the intrinsic relationship between shifting time and pressure impact,and proposed a new concept of optimal shifting timeTherefore,in this paper, experiments were conducted to find out pressure impact forming law, and both oil pumps displacement and directionalcontrol valves shifting time were controlled simultaneously to seek optimal control scheme for effective reduction of pressure impact2 Experimental principleThe pressure variation of the oil in a pressure chamber depends upon the difference between volumes of the oil flowing in and out the chamber2Its obvious that effective reduction of this difference is of positive significance for depressing pressure impact As far as concrete pumping hydraulic system is concerned, the pressure impact resulting from the main oil cylinders stroke terminal lies upon the suitability of shifting time to a great extent3So its feasible and effective for absorbing pressure impact to accurately control oil pumps displacement according to hydraulic systems requirement,and combine it with shifting time control techniqueWhat is shown in Fig.1 is the principle drawing of the experimental system sued to study characteristics of pressure impact in concrete pumping hydraulic system and its controlling techniquesThe main oil pump(1)is a swash-plate type axial piston pump,which is provided with the function of constant horsepower control。negative flow contr01The pressured oil used to contr01 oil pumps displacement comes from tilting systemIn this controlling oil line,a 3-way,2-position directional valve(11)with one solenoid and a pressure reducing valve(12)are installed in seriesWhen the solenoid of valve(11)is de-energized,the pressured oil from tilting system is stopped,and the pressured oil in the displacement control device of oil pump(1)is introduced into oil reservoir simultaneously by the valve(11)Here,the oil pressure in the displacement control device is zero or very low,the oil pumps displacement can come to maximumOn the other hand,when the solenoid of valve(11)is energized,the pressured oil coming from tilting system is introduced by the valve(11),and is decompressed by pressure reducing valve (12),and comes into the displacement control device,so 8s to make oil pumps displacement be reduced to minimum or zero.Two hydraulic cylinders(6.1,6.2)are connected in series,and four check valves and four throttle valves,which perform the functions of suction and cushioningare installed on the cylindersTwo non-contacting sensors(9,10)are used to provide shifting signalsFour pressure sensors are installed at the testing points M1,M2,M3 and M4 respectivelyThe signals provided by these sensors are collected and analyzed synchronously by a spectrum instrument and a microcomputerThe sampling frequency is 1 kHzThe sampling time is one minutes at a time so as to gain several pressure signals during shifting from a samplingDuring the experimental process,the pressure signals only during such shifting process as oil cylinders(6.1and 6.2)extends and retracts to the end respectively were analyzedWhen the sensor(10)obtains the signal of cylinder(6.2)retracting stroke terminal,the electrical system gives the instrument for regulating oil pumps displacement to decrease its swash-plates angle,and gives signal to make valves(8,7)shift after a certain time 1ag During such shifting process,the shifting time of valve(1)depends on following two factors:one is the sensor(10)s installation position relative to the cylinder(6.2);the other is the shifting time lag iethe difference between the times when main oil pump(1)begins regulating displacement and when the hydro-piloted directional contr01 valve (7)begins to shiftIn order to simplify the experiments,the sensor(10)s installation position relative to the cylinder(6.2)is changeless,and the oil pumps displacement regulating time is also invariableThe difference between the times when the oil pumps displacement begins to reduce and when begins to increase is 0.2s3 Experimental results and analysis Figure.2 shows the curves of pressure versus time,which were measured at points M1 and M2 when time lag At.is 0.12sIt can be seen from the curves shown in Fig.2 that the pressure impact extent in the chamber in which the testing point M1 is situated decreases gradually along with an increase in the working pressureThe main reason is that the pump adopts constant power control,in response to the rise of the working pressure,the swash-plates tilting angle is decreased,and pumps displacement is reduced。the main oil cylinders velocity becomes smallerSo the pressure impact decreasesIts also seen from Fig.2 that there are two pressure peaks in the curves measured at testing point M1.The time of producing those two pressure peaks corresponds with the two transitional positions of directional control valve(7)during its spool shiftsFigure3 shows the curves of pressure versus time,which were measured at points M1 and M3 when time lag At:is 0.09s,and the working pressure is10 MpaIt can be seen from Fig3 that the second pressure peak in the curve measured at point M1 is much smaller than the first oneThe main reason is as follows:when the sliding spool of directional control valve(7)moves to the first transitional position,its impossible that obvious variation of swashplates tilting angle takes place,and the oil flow is still big When the sliding spool of directional control valve(7) moves to the second transitional position,swash-plates tilting angle has become relatively small,and the oil flow is also smallTherefore,the volume difference of the oil between flowing in and flowing out the pressure chamber at the second transitional position is much smaller than at the first transitional position,which results in that the second pressure peak is much smaller than the first oneIt can be seen;by a comparison between Fig2(a)and Fig3,that the time lag At:has obvious influence upon pressure impact at the testing point M1Too short time lag.附录B混凝土运输车中液压泵压力的影响摘要 本文介绍了混凝土运输车中液压泵中的压力大小对整个液压系统的影响,液压泵的压力大小是影响整个工作系统的可靠性和使用寿命的关键因素,如何确定液压油在封闭液压缸中产生的压力的大小,要通过综合和理论上进行分析才能确定该工况下产生压力的影响,比如,油流量的要求,泵排量的控制,协调阀反应时间的控制,通过这些方面的控制,通过改变其中任何一个都可以减轻压力对整个系统的影响,只要通过定量控制这些参数的变化时间以及位移的控制就能做到,本文介绍了为实现准确控制,通过实验调查压力的影响以及控制其影响的实验系统,这个实验系统能够模拟混凝土泵在工作情况中的基本参数,这种压力的影响和控制参数的不同分别与工作条件的可行性和有效性的技术,本文提出了如何控制压力影响进行了验证。关键词 压力的影响;液压系统; 混凝土运输液压系统中的液压泵1简介在工作过程中,例如混凝土运输装置比如用卡车作为混凝土泵的运输装置,用来放置混凝土泵,混凝土运输车,两个汽油气缸来驱动两个具体交换气瓶分别和快速切换方向,频率最高能够超过30次每分钟,这会产生严重的液压冲击,这是一个重要因素对于增加系统的不良性能并且降低系统的可靠性,如何降低这种这种机器振动、噪声和系统温度过高的影响,关键的因素是增强混凝土机械泵的可靠性并且掌握压力的影响,完善混凝土运输系统中液压泵以及液压系统及其控制技术。采取如下几种措施可以减少压力对系统的影响;1 安装液压储能器或卸载阀,2改变滑动阀芯的结构,3控制开关速度滑动阀芯等。虽然这些措施具有很重要的作用,可以吸收激增的压力,但还是有明显的局限性,他们是被动的措施,调查过程中对于具体的液压系统,提出了新的方法调节油泵流量,减少压力的影响,通过研究液压油流量时间和压力的内在影响,提出了新的方法来优化流量时间,因此,通过大量的实验在次基础下找出压力影响的规律,在油泵转速和方向阀的改变时间被控制的同时,寻求最佳控制计划,有效减少压力影响。2实验原理压力的变化取决于在压力室中液压油流入量与流出量之间的差异,很明显,有效的减少这种差别是具有重要意义的减少压力的影响。至于混凝土运送液压系统而言,压力造成的影响主要是液压油在液压缸终端的撞击的移动时间过快。所以根据液压系统的要求,可行和有效的吸收压力的影响,以及精确控制油泵流量和活塞运动时间的控制。如图1所示是研究压力影响的液压系统的原理图,混凝土运送系统的液压系统及其控制技术,主油泵1是一种柱塞泵,这是提供液压力的装置。出油控制对照来控制油泵系统,通过这个控制油路3个油路,2个换向阀11,同一个的电磁铁和降压阀12安装在一起。当电磁阀11断电时液压油换向系统停止工作,并迫
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