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外啮合齿轮泵的间隙优化及振动和噪声的研究
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摘要
齿轮泵作为一种液压传动的基础元件,除具有公认的结构简单、体积小、重量轻、价格低等优点外,还有结构上容易实现多联化、抗污染能力强、可在恶劣条件下工作等特长,成为使用最可靠、应用最广泛的一种液压元件。自液压技术应用以来,齿轮泵高压的研究从未间断过。但随着压力升高,齿轮泵的效率降低,内泄漏增加,造成功率损失。由于一般液压系统的能量有60%的输入功率转化为热能消耗掉,而无功功率不仅造成能源的浪费,而且转化为热量,使油温发热,并引起较大的振动和噪声。严重影响油泵的工作稳定性和使用寿命。故现代液压系统的设计,把提高系统效率,降低能耗作为重要的质量指标。液压泵作为能量转换装置,对液压系统的总效率影响很大,而效率的高低,主要取决于元件的结构设计,而齿轮泵的效率主要包括容积效率和机械效率。容积效率与间隙的三次方成正比,机械效率与间隙成反比,因此,有必要对齿轮泵的间隙进行参数寻优。同时,外啮合齿轮泵的噪声比较大,作为液压系统主要的噪声源,大约的70%的振动和噪声起源于泵。而振动和噪声已成为液压技术向高压,高速发展的主要障碍。因此有必要对噪声产生的机理,影响因素和控制方法进行分析和探讨。
    为提高齿轮泵的效率,需对其能量损失进行分析。齿轮泵的能量损失主要包括容积损失和机械磨擦损失。容积损失主要体现为泄漏。泄漏分为内泄漏和外泄漏,外泄漏主要发生在泵体与前,后端盖之间的接合面上,主要由两者间的密封不良引起,外泄漏应该避免,或者减小到最低程度。内泄漏的主要形式为间隙泄漏,内泄漏的主要途径为:齿轮端面间隙的泄漏,齿轮径向间隙的泄漏,齿面接触处的泄漏,液体压缩时的弹性损失。泵的机械损失主要体现为各部分的摩擦损失,主要包括:齿顶与液体的粘性摩擦损失,齿轮端面与液体的粘性摩擦损失,轴和轴承的摩擦损失,齿轮啮合的摩擦损失,轴和轴封的摩擦损失。
    CBZb2系列的外啮合齿轮泵,其端面泄漏约占总泄漏的~,径向泄漏约占总泄漏的37%~49%,弹性损失约占总泄漏的2%~3%。齿轮泵在的能量损失相对两部分损失比较,占的份额较少,因此只考虑与间隙有关的机械损失。而容积泄漏与间隙的三次方成
    
    
    正比,机械磨擦损失与间隙成反比。要使功率损失最小,就需要合理控制间隙的大小.而总功率损失为泄漏功率损失和粘性磨擦损失之和。因此必然存在一个兼顾二者的最佳间隙,使总功率损失最小。为此,我们建成立了轴向间隙和径向间隙的功率损失方程:
    (Ⅰ)端面间隙的功率损失:由端面泄漏量引起的功率损失和齿轮端面所受到的粘性磨擦损失两部分组成。
    
     =
    
    (Ⅱ)径向间隙的功率损失:由径向泄漏和齿顶面受到的粘性磨擦阻力所组成。
    
     =
    为求得这个最优间隙,令
     ,则
    得最优轴向间隙方程为: (m)
    最优径向间隙方程为: (m)
    由仿真程序JLZY.CPP求得最优轴向(径向)间隙,并由JLCY.CPP求得在优化间隙下的各效率值。可知,对于CBZb2系列各型号齿轮泵,理论最优轴向间隙为10e-5数量级,理论最优径向间隙为10e-6数量级。间隙值较小,效率
    
    
    较高,但由于间隙过小,导致磨擦副润滑不良,抗污染能力减弱,齿轮泵寿命缩短。这主要因为该模型只是在考虑了功率损失最小,能量利用率最高的情况下求得的。在实际应用中,最佳间隙是一个多元函数,从最优化方法求之,需要考虑许多目标函数。CBZb2050型齿轮泵的轴向间隙取值为: ,径向间隙取值为:。这是因为在实际确定间隙大小时,还要综合考虑各方面的因素。如在确定径向间隙时,除应保证磨擦副间的良好润滑外,还应考虑轴承中的间隙以及齿轮泵受径向力产生的偏心,同时还要保证齿轮在运转过程中,齿顶不能刮伤壳体(扫膛)的情况出现。由于CBZb2系列外啮合齿轮泵采用了径向浮动补偿装置,所以,在实际中,径向间隙值的大小是由起润滑作用的一层油膜的厚度所决定的,对于轴向间隙,由于该系列齿轮泵具有轴向浮动补偿结构,故其轴向间隙值的确定方法为:在摩擦副前侧,是由起润滑作用的一层油膜厚度决定,而在摩擦副后侧,是由自动浮动侧板的浮动补偿来控制的。
    有效控制摩擦副的间隙,一直是改善泵转换效率的重要措施。CZBb2系列外啮合齿轮泵,采用了端面和径向间隙补偿装置,合理控制和保证了其间隙均匀,不仅使高压齿轮泵的效率得到了很大提高,而且拓宽了高效工作区。从实用的角度看,高效率区宽广比最高效率值大更有实际意义,因为客观需要泵不仅在额定工况下运转,更多的工况是在不同压力下运转。故应力求泵工作压力和输入转速对泵的工作效率影响不敏感。
    在液压装置中,液压泵产生噪声的名次居第一位,传递噪声的名次居第二位,液压泵是液压系统主要的噪声源。本文以CBZb2050型外啮合齿轮泵为研究对象,对其产生机理,影响因素和控制方法进行了探讨。CBZb2050型外啮合齿轮泵噪声较大,这主要是因为一方面本身由于压力流量脉动,困油现象,气穴气蚀,齿轮啮合冲击等原因,导致流体噪声较大。另一方面,CBZb2050 型齿轮泵采用的轴承是长圆柱滚子轴承,长圆柱滚子轴承在转动过程中,造成
The gear pump is an essential component in hydraulic system . This type of pump featuring the ease in realizing multi-unit design , high resistance to contamination ,workability under adverse conditions as well as its well-known compact construction ,light weight and low cost has become one of the most reliable and most popular hydraulic power sources .Since the use of hydraulic pressure technique ,high pressure research of gear pump has never interrupted .Yet with the pressure ascend ,the effectiveness of gear pump cuts down ,inner leakage adds ,make drive power loss .Since sixty percent of ordinary hydraulic pressure system input energy has been transformed to the heat energy and used up .But the power without work not merely creates energy resources waste ,but also transform to amount of heat ,and causes the oil temperature generate heat .Moreover arouse greater vibration and noise .It makes grave effect to gear pump work stability and service life .Therefore contemporary hydraulic pressure system design ,the total effectiveness of raise ,cut down the energy consumption was thought of as the significant indicator of quality .The hydraulic pump as the energy transformation unit ,has great effect to total efficiency of hydraulic pressure system .But the effectiveness is decided chiefly by the element physical design .But the gear pump effectiveness consists of volume efficiency and mechanical efficiency mainly .The volume efficiency is against three direct ratios in the gap ,and the mechanical efficiency succeeds the inverse proportion against the gap .So there is indispensability to carry on the parameter optimization .At the same time ,the external gear pump noise is comparatively greater .As main noise source of hydraulic pressure system ,there is about seventy percent of vibration and noise that comes from gear pumps .But vibration and noise have become the main obstruction to high pressure and high rotation .Hence the analysis of the noise ,influential factors and method of control is necessary.
    In order to raise gear pumps’ effectiveness, we should analysis energy loss .The gear pump energy loss chiefly consists of the volumetric loss and mechanical loss .The volumetric loss acts as leakage . Leakage is divided into inner leakage and outward leakage .The outward leakage chiefly happen at the junction surface between the before and back lid .It is aroused by two seals badly
    
    
    airtight .The outward leakage should be averted, or decrease up to the lease degree .Inner leakage is mainly through the gap .The main method of inner leakage is :gear end face gap leakage ;gear radial gap leakage ;tooth contact part leakage ;reliance loss when liquid compressed .The main embodiment of mechanical loss is friction loss .Mainly including :the viscosity friction loss of tooth peak with liquid ;viscosity friction loss of gear end face with liquid ;the friction loss of shaft and bearing ;the friction loss of gear coupling;,the friction loss that shaft and shaft seal .
    To external gear pumps of CBZb2 set , in total leakage, is about 48%-60% , is about 37%-49%, is about 2%-3%.Comparing with , ,the energy loss at , , is little ,hence we merely consider the loss ,that have something to do with the gap . The volume efficiency is against three direct ratios in the gap , and the mechanical efficiency succeeds the inverse proportion against the gap .In order to make drive power minimal ,we should control the gap .But the total loss is the sum of the volumetric loss and that of viscosity friction .So it must have the optimum gap of two that make energy loss minimal .For this reason ,we put up the energy loss equation of axial gap and radial gap:
    (Ⅰ)Energy loss in end face gap :It consists of the end face leakage loss and the viscosity friction loss.
    
     =
    
    (Ⅱ)Energy loss in radial gap :It consists of the radial leakage loss and the tooth peak viscosity friction.
    
    
     =
    In order to obtain the most optimization gap , we suppose,
     ,then
    The most optim
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