面接触形式下牵引油拖动特性的研究

牵引传动是利用牵引油膜在传动接触区产生的剪切力来传递运动和动力的,所以油品本身牵引特性的高低直接影响牵引传动的牵引效率,因而对各种油品特性的研究也较多。在HZS-1型动压滑动轴承试验台上对8号液力传动油面接触形式下的拖动特性进行了实验研究,并运用Matlab软件对实验结果进行了处理,分析比较得出结论。     

粘性牵引传动--行星滚子变速器

牵引传动最早开始用于汽车工业,用它有助于解决把汽车发动机动力传递到汽车后轮.现代牵引传动是利用金属滚动体之间的粘性液体油膜把动力源的动力作有效传递.该金属滚动体可以是锥形体、圆柱形、圆盘和环节.因此所谓牵引传动必须包含三个元件:即(1)输入滚动体(2)粘性牵引液(3)输出滚动体.行星滚子牵引传动采用行星环和滚子,最早由Walter Chery为农用设备变速传动开发设计的.本文将对这种传动的几何字、运动学和力学等传动机理作比较详细的分析.     

牵引传动研究综述

牵引传动是一种性能优越的传动.牵引传动可分为固定速比传动(FRT)和连续变化速比传动(CVT).牵引传动需要一定的正压力,产生正压力的方法可分为恒压式和自动式.自动加压的牵引装置有多种多样.由于现有牵引介质的牵引能力不够大,我们提出用磁流体牵引代替弹流体牵引的设想,以提高牵引传动的牵引能力.     

行星牵引传动在冷却塔中的应用

光滑圆柱体组成的行星牵引传动具所有超低噪音、超低振动的优良特性，非常适合对噪音要求较高的场所。本文研究了行星牵引传动的原理，实现牵引传动的技术关键及加载机构的设计。给出了一种应用牵引传动原理设计低噪音冷却塔行星牵引传动减速器的依据和要点。     

牵引式无级变速器牵引效率研究

以牵引式无级变速器为研究对象,推导出了自转角速度、由油膜滑动产生的牵引力和由自转产生的力矩等解析式。通过实例,计算和分析了牵引效率与接触压力、油膜牵引力、输入转速和几何曲率比等因素间的变化规律。     

Effect of EHL Contact Conditions on the Behavior of Traction Fluids

New infinitely variable transmission (IVT) systems are under development for the automotive industry as a means to achieving significant fuel economy benefits. These systems rely on the lubricating fluid to transmit the drive train loads across the interface of the transmission components. This requires the development of new fluids that exhibit high traction properties under elastohydrodynamic lubrication (EHL) conditions. However, it has been reported recently that the traction performance of some fluids can reduce dramatically as temperature is reduced. This may place severe operational limits on IVT systems and suggests that the low-temperature traction properties of fluids for these systems should be studied in order to understand the mechanism for the observed reduction in traction.

The work reported here is an experimental study aimed at identifying whether low temperature traction reduction is related to a fundamental change in rheological behavior specific to the fluids tested or to more generic changes in the EHL contact conditions. A series of model experiments were performed using a mini traction machine (MTM) on three high-viscosity polybutene samples. The results have been mapped against previously reported non-dimensional parameters used to identify different EHL regimes. The results show that dramatic reductions in traction occur when the contact transitions from the rigid piezo-viscous (RP) toward the rigid iso-viscous (RI) region. Similar results were also found for two other high-viscosity fluids of different molecular structure and lower traction properties. The results support the hypothesis that the reduction in traction observed at low temperature is due to a change in EHL contact conditions rather than being solely due to a change in the rheological performance of the test fluids.     

High‐pressure short time behavior of traction fluids

The squeeze film formation ability of traction fluids is studied under impact load by dropping a steel ball‐bearing against a flat anvil made of mild steel. The effect of the pressure–viscosity coefficient and of the viscosity is investigated for plastic impact. The depth difference between the lubricated surface dent and the dry dent increases linearly with the product αη of the pressure–viscosity coefficient α and the viscosity η. The importance of the lubricant parameter αη is observed under the squeeze film formation ability from contact voltage or elastohydrodynamic lubrication central film thickness measurement at rolling condition. The intensity of each impact collision is measured by means of an acoustic emission (AE) sensor. The high‐pressure short‐time solidification of traction fluids was confirmed by dent analysis after the impact tests and AE analysis under impact loads. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of surface roughness on elastohydrodynamic traction. Part 2

To investigate the performance of a traction‐drive toroidal continuously variable transmission, the traction characteristics under partial elastohydrodynamic lubrication contact were calculated theoretically based on roller test results. A calculation model was constructed for considering the effects of surface roughness on performance. The model incorporated a viscoelastic and elastic‐plastic model using a nonlinear Maxwell model to represent the rheological behaviour of the traction fluid. The validity of the model was confirmed by its good agreement with the experimental results described in Part 1 of this paper. Various calculations were made to investigate the effect of surface roughness on traction under the operating conditions of an actual traction drive. The results indicated that the effect of surface roughness on durability could not be ignored.     

振子驱动型牵引传动研究

在常规牵引传动和往复牵引传动的基础提出了一种依赖反复微小振动进行动力传动的振子型牵引传动。先通过振子振动形成油膜实验得出在接触区施以微小振动更易形成油膜的结论,又通过圆周运动型牵引传动实验得出了其相对于摩擦传动磨损小的优点。利用微小振动形成润滑油膜的方法引起的磨损小,可广泛应用于光学聚焦等精密运动领域。     

行星锥环无级变速器几何滑动率数值计算方法

本文根据牵引式行星锥环无级变速器的结构特点和传动原理，推导了各接触点牵引系数和传动系数的计算公式，提出了一种确定牵引传动滚动点和圆周力作用点位置的数值计算方法，计算了XM750型无级变速器几何滑动率的理论曲线，测试证明理论曲线与实验曲线基本吻合。     

液粘调速离合器摩擦片的测试和研究

液粘调速离合器是利用摩擦片间的相对滑动来实现无级变速的新型传动装置.由于它的动力传递、转矩改变和转速的调节都是靠液体的粘性牵引来实现的,所以这种传动实质上就是液体粘性的牵引传动.着重阐述在实际工况,根据对比试验,证实我们设计研制摩擦片的适应性.     

PERFORMANCE SIMULATION OF VEHICLES EQUIPPED WITH TRACTION DRIVE CVTS

0 INTRODUCTIONVehicles equipped with continuously variable transmission(CVT) have the potential of better fuel economy than vehicleswith conventional stepped ratio transmissions. Although the mar-ket penetration of CVT vehicles today is still insignifican…     

弹性圈高速行星牵引传动机构

在总结浙大化机所超高速传动机构的设计与应用的基础上，提出了一种新的弹性圈高速行星牵引传动机构。该机构利用计算机控制高压油路系统，可任意调节与中空滚子接触处的弹性圈的变形量，以确保任意转速下传动机构的传动能力。利用有限元方法分析弹性圈的有效变形及应力的大小与分布状况，证明此机构完全能达到设计要求，能够胜任高速、超高速机械运动。     

常功率无级变速器(CP-CVT)工作原理和分析

本文是一种新颖的常功率无级变速器(CP-CVT)牵引传动发表的系列论文的首篇.本文提出了常功率的基本机能原理和证实了该装置的特性.该装置属于大家知道的圆环牵引传动系列,它由两个输入盘、一个圆锥形环和另一圆环、一个锥形输出盘和若干钢球组成.各钢球的转轴按相对于输入和输出圆盘的几何位置作自行调整,输出转矩的变化使钢球相对盘的位置改变从而造成速比变化,首先进行钢球运动学和动力学分析,再推论了有关功率传递动力学公式和几何参数.最后提出CP-CVT可提供的良好的功能稳定功率特性满足汽车工业要求的结论.     

Experimental investigation of temperature rise in elliptical EHL contacts

A toroidal traction drive continuously variable transmission (CVT) transmits power by the shearing action of lubricant film under heavy loads at contact points on the CVT rollers. In other words, rolling and sliding motions produce traction force. Furthermore, due to the geometry of the toroidal CVT, spin motion is produced at the contact points. These contact points, which are elliptical in shape, are where shear stress of the lubricant generates frictional heat. Temperature rise at the contact point has never been measured under the conditions of high rolling speed (velocity) and minute amounts of sliding (slippage), nor has the influence of spin motion on temperature rise been examined thus far. The authors et al. measured temperature distribution at contact points under conditions of high rolling speed and minute amounts of sliding, such as what is found in a toroidal CVT, using an FZG twin-disk test machine and thin-film sensors. The influence of spin motion on temperature rise was also experimentally investigated.     

航空润滑油拖动特性动态数据库的建立

建立的润滑油拖动特性动态数据库具有查询、计算、绘图、比较、维护和设置步长等多项功能.通过该数据库,可以查到多种航空润滑油在多种工况条件下的拖动系数及拖动系数计算公式中的系数值,可以对不同润滑油的拖动系数进行比较及同一种油的计算值和试验值进行比较.     

The Elastohydrodynamic Traction of Synthetic Base Oil Blends

The aim of this study was to investigate the elastohydrodynamic (EHD) properties of lubricant blends. Three base fluids of very similar viscosities, a polyalphaolefin, a diester and an alky lated aromatic, have been obtained and their EHD film thickness and traction behavior measured at a range of pressures. Blends of these fluids have been prepared and the influence of blending on film thickness and traction has been investigated. Traction measurements were conducted at film thicknesses between 100–200 nm and thermal analysis was incorporated to correct for in-contact shear heating. The blends showed a broadly linear relationship between the inlet pressure-viscosity coefficient and blend composition. Isothermal traction comparisons revealed that traction is not an additive property of lubricant blends.     

The nature of the logarithmic traction gradient

Great significance has been attached to the logarithmic traction gradient in elastohydrodynamic lubrication. It has been used to justify the assumption of logarithmic constitutive behavior.We have calculated viscous traction curves from the viscous shear response that is observable by simulation or experiment out of contact. This response includes Newtonian, shear-thinning of the ordinary power-law type, and rate independent behavior. The calculated traction curves can be reasonably described by a sinh law using fictitious viscosity and Newtonian limit. These system model parameters behave as expected from cases where the same system model was applied to measured traction.We conclude that for point contact, the logarithmic gradient results from rate-independent (limiting stress) behavior combined with greater than exponential pressure-viscosity behavior. Shear-thinning has little effect on this gradient in point contact. On the other hand for line contact, shear-thinning of the ordinary type (Carreau) is essential for the appearance of a logarithmic gradient.     

Increase of Traction Coefficient due to Surface Microtexture

Increasing the traction coefficient of a traction drive system is a key factor in obtaining a smaller, lighter unit and also greater torque capacity. This study focused on the microtexture of the rolling elements, and effect of microtexture was examined with the aim of improving the traction coefficient in the viscous region. Three textures—dimple, transverse, and longitudinal—were examined using a 4-roller tester that enabled tests to be conducted under high pressure and high rolling speed. As a result, it was found that the longitudinal surface texture is the best for improving the traction coefficient. The results obtained with EHL analysis showed that only the surface texture with longitudinal grooves increased the traction coefficient, just as in the tests conducted with the 4-roller tester. The longitudinal surface texture was optimized using the 4-roller tester. The test results made it clear that the groove depth, groove pitch, and also the radius of curvature of the convex portion of the rolling elements are important parameters of the longitudinal grooves for improving the traction coefficient while assuring high durability at the same time. An attempt was then made to increase the traction coefficient of an actual CVT variator by applying the optimized longitudinally grooved microtexture to the traction surfaces. The test results show that the traction coefficient can be increased without sacrificing durability by optimizing the surface microtexture.     

A non-averaging method of determining the rheological properties of traction fluids

Traction machines have been frequently used to study the rheological responses of lubricants in elastohydrodynamic lubrication (EHL) contacts. Fundamental properties are inferred from EHL traction measurements based on the average pressures and temperatures in the contact. This average approach leads to uncertainty in the accuracy of the results due to the highly nonlinear resonse of the fluid such as viscosity to both pressure and temperature. A non-averaging method is developed in this paper to study the elastic and plastic properties of traction fluids operating in EHL contacts at small slide-to-roll ratios. A precision line-contact traction rig is used to measure the EHL traction at a given oil temperature and Hertz pressure. By choosing a sensible pressure-property expression, the parameters of the expression can be determined through the initial slope and peak traction coefficient of the traction measurements. The elastic shear modulus and the limiting shear stress of the lubricant corresponding to a single pressure can then be calculated for a range of pressures and temperatures of practical interest. Two high-traction fluids are studied, and their elastic moduli and limiting shear stresses presented.