外文翻译--混凝土运输车中液压泵压力的影响

附录 A Investigation on Pressure Impact in Concrete Pumping 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 life Based 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 forward The quantitative controlling parameters about shifting time and displacement control are introduced to realize accurate control The experiment investigations of pressure impact property and its control are carried through on an experimental system which is able to simulate concrete pumping condition The basic law that pressure impact and controlling parameters vary with working condition respectively The feasibility and validity of the technology proposed in this paper to control pressure impact are confirmed. Keywords: Pressure impact； Hydraulic system； Concrete pumping machinery 1 Introduction During 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 impact It is an important factor resulting in bad performance and low use reliability of the machine， and vibration， noise and overheating etc so it s a key of improving concrete pumping machinerys reliability to gain a mastery of pressure impact property in concrete pumping hydraulic system and its controlling technology Such technological measures as follows were taken to reduce pressure impact： (1)installation of a hydraulic accumulator or unloading valves， (2) change of sliding spool s structure， (3)control of the switching speed of sliding spool，etc1 Though these measures play an important role in absorption of pressure surges， there are obvious limitations， and they are passive measures Literature.2. investigated the switching process of concrete pumping hydraulic system， and put forward active measure of regulating oil pumps displacement to reduce pressure impact Literature3studied the intrinsic relationship between shifting time and pressure impact， and proposed a new concept of optimal shifting time Therefore， in this paper, experiments were conducted to find out pressure impact forming law， and both oil pump s displacement and directional control valves shifting time were controlled simultaneously to seek optimal control scheme for effective reduction of pressure impact 2 Experimental principle The pressure variation of the oil in a pressure chamber depends upon the difference between volumes of the oil flowing in and out the chamber2 It s 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 extent3 So it s feasible and effective for absorbing pressure impact to accurately control oil pumps displacement according to hydraulic system s requirement， and combine it with shifting time control technique What 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 techniques The main oil pump(1)is a swash-plate type axial piston pump， which is provided with the function of constant horsepower control。 negative flow contr01 The pressured oil used to contr01 oil pump s displacement comes from tilting system In this controlling oil line， a 3-way,2-position directional valve(11)with one solenoid and a pressure reducing valve(12)are installed in series When 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 pump s displacement can come to maximum On 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 pump s 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 cushioning are installed on the cylinders Two non-contacting sensors(9,10)are used to provide shifting signals Four pressure sensors are installed at the testing points M1， M2，M3 and M4 respectively The signals provided by these sensors are collected and analyzed synchronously by a spectrum instrument and a microcomputer The sampling frequency is 1 kHz The sampling time is one minutes at a time so as to gain several pressure signals during shifting from a sampling During 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 analyzed When the sensor(10)obtains the signal of cylinder(6.2)retracting stroke terminal， the electrical system gives the instrument for regulating oil pump s displacement to decrease its swash-plate s 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 i e the difference between the times when main oil pump(1)begins regulating displacement and when the hydro-piloted directional contr01 valve (7)begins to shift In order to simplify the experiments， the sensor(10) s installation position relative to the cylinder(6.2)is changeless， and the oil pump s displacement regulating time is also invariable The difference between the times when the oil pump s displacement begins to reduce and when begins to increase is 0.2s 3 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 0.12s It 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 pressure The main reason is that the pump adopts constant power control， in response to the rise of the working pressure， the swash-plate s tilting angle is decreased， and pump s displacement is reduced。 the main oil cylinder s velocity becomes smaller So the pressure impact decreases It s 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 shifts Figure 3 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 Mpa It can be seen from Fig 3 that the second pressure peak in the curve measured at point M1 is much smaller than the first one The 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 swash plates 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 small Therefore， 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 one It can be seen； by a comparison between Fig 2(a)and Fig 3， that the time lag At： has obvious influence upon pressure impact at the testing point M1 Too 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，并迫使液压油流 入油泵 1，进入油箱。在这种情况下，液压油的压力控制装备的位移为零或者非常低，油泵位移可以到最高。