Mathematical Model and Experiment Validation of Fluid Torque by Shear Stress under Influence of Fluid Temperature in Hydro-viscous Clutch

The current design of hydro-viscous clutch（HVC） in tracked vehicle fan transmission mainly focuses on high-speed and high power. However, the fluid torque under the influence of fluid temperature can not be predicted accurately by conventional mathematical model or experimental research. In order to validate the fluid torque of HVC by taking the viscosity-temperature characteristic of fluid into account, the test rig is designed. The outlet oil temperature is measured and fitted with different rotation speed, oil film thickness, oil flow rate, and inlet oil temperature. Meanwhile, the film torque can be obtained. Based on Navier-Stokes equations and the continuity equation, the mathematical model of fluid torque is proposed in cylindrical coordinate. Iterative method is employed to solve the equations. The radial and tangential speed distribution, radial pressure distribution and theoretical flow rate are determined and analyzed. The models of equivalent radius and fluid torque of friction pairs are introduced. The experimental and theoretical results indicate that tangential speed distribution is mainly determined by the relative rotating speed between the friction plate and the separator disc. However, the radial speed distribution and pressure distribution are dominated by pressure difference at the lower rotating speed. The oil film fills the clearance and the film torque increases with increasing rotating speed. However, when the speed reaches a certain value, the centrifugal force will play an important role on the fluid distribution. The pressure is negative at the outer radius when inlet flow rate is less than theoretical flow, so the film starts to shrink which decreases the film torque sharply. The theoretical fluid torque has good agreement with the experimental data. This research proposes a new fluid torque mathematical model which may predict the film torque under the influence of temperature more accurately.

Numerical film torque modeling of friction pair in hydro-viscous clutchs

A numerical model to predict film torque of hydro-viscous clutch was developed.The model was established with computational fluid dynamics（CFD）.The pressure distribution,velocity of flow and film torque were obtained based on vertical-horizontal grooved plate and radial grooved plate separately.The boundary conditions,such as the relative rotation,the fluid temperature and the oil feeding pressure,were also discussed.The results showed that the film torque of two kinds of grooved plate increased with increasing relative rotation.However,the film torque decreased with increasing fluid temperature and feeding pressure.Meanwhile,the film torque of radial grooved plate was less than vertical-horizontal grooved plate at the same condition.Our study showed that the model can efficiently calculate the film torque with complex geometry parameters and boundary conditions.

Mechanism of hydro-viscous soft start of belt conveyor

The mechanism of a hydro-viscous soft start is of great importance in the design of a hydro-viscous clutch and its control system. To explain the mechanism of a hydro-viscous soft start, the startup process of a belt conveyor was numerically analyzed with the modified Reynolds equation, an energy equation and a temperature-viscosity equation. The effect of temperature and grooves of the friction disk surface on torque transfer and load capacity of the oil film have also been analyzed. The results show that 1) the grooves are the basis of forming dynamic pressure but they may reduce the capacity of torque transfer to a certain extent, 2) during the startup process, temperature has little effect on torque transfer and load capacity and the variation in load capacity of the oil film is very small, indicating that it is preferable to use the flow rate as a control object than the pressure of the feed cylinder. The results have been verified by an experiment.

Analysis Groove Characteristics of Friction Dishes in Wet Speeding Clutch

The impacts of different groove shapes, numbers, and angle of friction dish on transmitting torque, speed, push pressure in wet speeding clutch are discussed in this paper. Since the wet speed governing clutch works within hydrodynamic lubrication, mixture lubrication, boundary lubrication and contact situation, the oils combining with α hydrocarbon or polyester are getting widely used as lubricant. The power law fluid model with Patir Cheng average flow model, GT asperity contact model and oil film inertia are applied for average Reynolds equation setting. In order to investigate the relationship between average push pressure within hydrodynamic lubrication and mixture lubrication, average transmitting torque and output speed, the numeral calculation and analysis are presented. According to calculation, it is found that the groove shape, groove angle and groove numbers affect the average transfer torque and push pressure with the speed rate.

高速斜撑超越离合器楔合动态响应研究

针对斜撑式超越离合器高速楔合容易产生故障的实际情况,对其楔合动态过程进行研究。工作过程中,斜撑式超越离合器内部楔块之间、楔块与内外环间以及各部件同保持架间存在碰撞。首先基于Hertz接触理论,求解了碰撞刚度,为明确各参数对高速斜撑超越离合器动态响应的影响程度,建立了包括楔合延迟时间、冲击力矩、最大转速差等在内的评价指标。同时,将高速斜撑超越离合器的楔合动态过程进行划分,以研究几何参数对不同响应阶段的影响。最后,开展了楔块与内环的摩擦条件、弹簧力、碰撞刚度、阻尼和负载等对高速斜撑超越离合器楔合动态响应的研究。结果表明,不同参数对所定义的评价指标的影响程度不同,极端情况下可导致楔合失败。该研究可为工程实践提供一定的理论参考和指导。

空载湿式离合器临界碰摩转速影响机理分析

定义空载湿式离合器摩擦片/钢片的周期无量纲轴向位移范围λ,根据其值确定湿式离合器的临界碰摩转速。通过分析润滑油温度、供油流量、摩擦副间隙与特征量λ变化趋势的关系,得到工况参数对湿式离合器临界碰摩转速的影响规律。从力学角度出发,分析流场刚度和阻尼的变化规律,探寻摩擦片/钢片三自由度运动的影响因素,在此基础上提出流场临界刚度和临界阻尼的概念,揭示湿式离合器工况参数对其临界碰摩转速的影响机理,并进行了试验验证。研究结果表明:润滑油温度升高或摩擦副间隙增大会导致流场中的交叉刚度系数和交叉阻尼系数变大,湿式离合器的临界碰摩转速降低;供油流量增大会导致流场中的交叉刚度系数和交叉阻尼系数减小,湿式离合器的临界碰摩转速升高。

超越离合器试验台关键部件设计与计算

根据模拟离合器在实际工作状态下试验离合器的工作性能,设计了一种搭载2台异步电动机的超越离合器试验台,2台电动机分别与增速圆柱齿轮箱和减速圆柱齿轮箱配合模拟离合器在实际工作中的驱动模块和加载模块。采用斜齿圆柱齿轮传动齿根危险截面弯曲强度校核公式,对增速圆柱齿轮箱大小齿轮进行强度校核;基于SolidWorks软件Simulation模块对增速箱大小齿轮不同扭矩进行静应力仿真分析;计算传动轴的1、2阶临界转速,判断轴的工作转速是否处在安全范围、增速圆柱齿轮箱传动轴在高速运转过程中是否发生共振现象。为超越离合器相关研究提供参考。

基于工况识别的纯电动汽车2DCT换挡策略研究

为使纯电动汽车具有更好的经济性,同时保持较好的动力性,针对自主研发的纯电动汽车两挡干式双离合变速器(2DCT),提出一种基于工况识别的实时换挡策略。通过径向基神经网络预测车速,利用动态规划提取7种循环工况的最优换挡点,并搭建基于相似度比对的工况识别模型,对车辆行驶工况进行识别,实现实时换挡。基于MATLAB/Simulink进行仿真并完成2DCT台架实验。结果表明,提出的基于工况识别的实时换挡策略能同时兼顾车辆的经济性和换挡频率。

无离合器机械式变速器转速控制方法研究

常规的无离合器机械式变速器转速控制方法主要使用AMT生成转速控制单元,易受执行机构影响,导致换挡转矩波动过高,因此,需设计一种全新的无离合器机械式变速器转速控制方法。即设计无离合器换挡转速控制策略,利用简化扭振模型,调整无离合器机械式变速器发动机转速,以实现无离合器机械式变速器转速控制。结果表明,设计的无离合器机械式变速器转速控制方法的换挡转矩波动较小,证明了设计方法的控制效果较好,具有可靠性和一定的应用价值,为降低无离合器机械式变速器运行风险作出了一定贡献。

两挡混动变速器低成本液压系统开发

传统变速器和混动变速器的液压系统一般采用先导比例电磁阀和滑阀组合的形式控制主压,主压经过比例减压阀调压之后成为离合器控制压力,此类液压系统较为复杂,成本较高。为降低混动变速器的成本,开发基于节流孔调节离合器控制压力的液压系统,通过AMESim仿真软件进行仿真计算,节流孔孔径设计值为0.70 mm,为保证产品的一致性,减少制造误差的影响,节流孔孔径的公差值为±0.015 mm。经过制作样件,搭载混动变速器进行试验,结果验证有效,满足设计需求。

自动变速器牙嵌式离合器进挡概率研究与应用

文章以某9挡自动变速器的牙嵌式离合器为研究对象,建立了离合器结合各阶段的动力学模型。根据长短齿设计特征,分别计算无任何齿形接触、长齿接触长齿、长齿接触短齿、长齿接触长齿和长齿接触短齿同时发生四种场景在不同初始速差条件下的进挡概率。考虑随机齿形接触位置的终止速差,计算得到牙嵌式离合器进挡的最优速差,可用于滑行降挡最优进挡策略的制定,提升换挡质量。选取实车滑行五挡降四挡工况,进行进挡概率校验,结果和理论计算概率相符合。

An improved method for evaluating the rotational speed stability of a hydro-viscous clutch in mixed lubrication

Rotational speed stability is an important evaluation indicator of the performance of a hydro-viscous clutch(HVC).To improve the rotational speed stability of HVCs in mixed lubrication and the running condition of the friction pairs,the speed stability of an HVC in mixed lubrication was studied.To this end,the friction coefficients of both copper-based and paper-based friction pairs were experimentally tested using an MM1000-III wet friction machine.Theoretically,a torsional vibration model of the system is presented.The phase plane analysis method is applied to evaluate the stability of the torsional vibration model,where a critical negative gradient(CNG)is defined.The results show that the friction coefficient in mixed lubrication is an important parameter for the stability of the rotational speed.The system will be unstable when the negative gradient of the friction coefficient-slip speed is larger than the CNG.According to the definition of the CNG,suggestions regarding choice of friction pairs are made to improve the rotational speed stability of an HVC in mixed lubrication.

高速斜撑式超越离合器楔合性能影响因素分析

针对某型高速斜撑式超越离合器在使用过程中存在楔合失败、楔合响应慢等问题,基于ADAMS建立该离合器的动力学仿真模型,分析了斜撑块与内、外圈的摩擦因数、弹簧等效力矩、负载等效质量、阻尼、接触刚度对离合器楔合性能的影响,结果表明:负载、接触刚度对离合器楔合性能影响较大,摩擦因数、弹簧等效力矩、阻尼对离合器楔合性能影响较小。

离心脱开型斜撑离合器脱开转速计算及试验验证

脱开转速是斜撑离合器的主要技术指标,对斜撑离合器的使用寿命和主机安全性有重要影响。介绍了离心脱开型斜撑离合器的结构,建立力学分析模型,推导出离心脱开型斜撑离合器脱开转速的计算公式,并以某典型型号离合器为例进行脱开转速理论计算,同时提出了一种试验方法测试该型号离合器脱开转速,理论计算值与试验值基本一致,验证了脱开转速理论计算方法的正确性。

台虎钳的集成夹紧系统研究

针对目前常用的丝杆加力台虎钳工作效率低、夹持力小和劳动强度大等问题,提出1种集丝杆加压、双速柱塞泵增压、液压缸驱动夹紧的多重增压方式及抱合支承于一体的新型集成夹紧系统。分析了台虎钳的研究进展概况,论述了集成夹紧系统的工作原理、结构特点、相关参数的计算方法,并通过设计计算,得到两种液压台虎钳夹紧系统的工作参数。结果表明:新型台虎钳夹紧系统结构紧凑,增压比大,采用较小的手动力和较少的手柄转动数圈,即可实现对工件的夹持,夹紧力大且稳定可靠;手工推动活动钳身部分进行快速移动,工作效率远高于丝杠传动,使用方便快捷,特别适合工件尺寸范围大、大小工件调换频繁的场合。

高转速差航空摩擦离合器的接合特性与控制策略研究

摩擦离合器是航空飞行器动力系统的关键部件,其接合过程中的动力学特性直接影响航空飞行器的灵活性、平稳性和安全性。在高转速差接合情况下,摩擦离合器接合过程转速变化大、接合冲击大、非线性因素复杂,如何实现摩擦离合器在高转速差接合状态下的平稳和快速接合一直是航空飞行器所需突破的难题。以某短距起落航空飞行器中传动系统中的干式摩擦离合器为研究对象,考虑摩擦系数的非线性特性、飞行器传动系统负载的非线性变化因素,根据动力学原理建立干式摩擦离合器的动力学模型,分析离合器接合过程中的主/从动盘转速、摩擦扭矩和冲击度。引入摩擦离合器的接合时间和冲击度作为接合特性的评价指标,提出分段式接合压力加载控制策略,对比分析线性接合压力控制策略,所提出的控制策略具有接合时间短、冲击小的特点。研究工作可为某短距起落航空飞行器的干式摩擦离合器接合控制提供参考,提高我国航空飞行器的机动性和可靠性。

相对转速对湿式多片离合器磨合过程摩擦磨损特性的影响

湿式多片离合器摩擦元件磨合过程对其使用寿命和工作品质有重要影响.以铜基粉末冶金摩擦片和30CrMnSiA对偶片为研究对象,针对实车转速工况,使用SAE#2试验台进行湿式离合器循环接合试验.从全局摩擦特性和瞬时摩擦波动性两方面对磨合过程进行研究,应用金相显微镜得到磨合前后摩擦表面微观形貌特征和磨损机理.结果表明:转速的增加降低了磨合初期平均摩擦系数的下降速率及其随后的波动幅度;平均摩擦系数在低转速工况下呈现下降趋势,而高转速工况下呈现上升趋势.虽然提高转速可获得平滑的摩擦表面,并降低瞬时摩擦波动幅度,然而转速过高时,摩擦界面较大温升会使其发生热塑性变形,从而使瞬时摩擦波动越来越剧烈.低转速工况下,摩擦表面微凸体在界面匹配阶段发生严重剪切断裂,而后主要为塑性变形;高转速工况下,微凸体发生渐进式剪切同时伴随弹塑性变形.

湿式离合器欠约束摩擦副临界碰摩转速及带排转矩分析

带排转矩会降低湿式离合器的传动效率,缩短其使用寿命和降低其工作可靠性。目前针对湿式离合器带排转矩的研究大多基于平均间隙分布模型,但各摩擦副之间的间隙分布对带排转矩有重要影响,且获取处于工作状态的湿式离合器各摩擦副间隙分布是很困难的。因此,本文提出了一种湿式离合器各摩擦副间隙分布的仿真模拟方法,采用次序统计方法模拟各摩擦片和钢片的位置,获得各摩擦副初始间隙分布规律;在此基础上,通过仿真分析不同工况下欠约束多摩擦副系统的临界碰摩转速及带排转矩,并通过了试验验证。结果表明,在湿式离合器总间隙不变的情况下,欠约束多摩擦副系统的临碰摩转速小于基于平均间隙分布假设下的临界碰摩转速;随着湿式离合器总间隙的增加,临界碰摩转速逐渐下降;欠约束多摩擦副系统的带排转矩明显大于基于平均间隙分布假设下的带排转矩,随着湿式离合器总间隙的增加,带排转矩逐渐下降。

基于高速开关阀的湿式离合器缓冲控制系统研究

湿式离合器是大功率液力机械传动装置重要的传动部件,其工作状态直接影响设备的安全可靠运作。为了提高湿式离合器工作效率,通过分析离合器的工作原理,基于电磁式高速开关阀设计一种用于湿式摩擦离合器的液压控制系统,构建液压系统模型,通过MATLAB/Simulink仿真求解该液压系统的压力输出信号。计算结果显示:该液压系统可以用于控制湿式离合器的接合,能够为湿式离合器提供稳定的接合油压缓冲信号。

高线速状态湿式离合器带排转矩特性研究

为研究湿式离合器空载状态下摩擦片高线速工况带排转矩产生回升变化的机理与规律,基于流体动力学模型,考虑润滑油膜表面张力与高线速油-气两相流的影响,建立了带排转矩数学模型和带排间隙油膜VOF两相流仿真模型,对油膜的变化进行分析验证。对模型进行分析获知,摩擦片高线速下油-气两相流产生部分带排转矩是带排转矩回升的主要原因。在摩擦元件高速带排试验系统中进行了带排转矩试验,分析了旋转方向、润滑油温度、流量、带排间隙、摩擦片尺寸对湿式离合器带排转矩的影响规律。