Efficiency Evaluation of Continuously Variable Transmissions Including a Planetary Gear Train

With their advantages, continuously variable transmissions have gained more popularity in the last decade by their use in mechanical transmission systems. The present paper aims to analysis the efficiency of the transmission based on the mechanical efficiency of the planetary gear train integrated in such transmission. In this analysis, we consider the mechanical efficiency of the transmission has been determined considering how the efficiency of the CVT members changes as a function of the operating conditions. The efficiency of the planetary gear train as a function of the configuration, speeds in his three input/output shafts, and also with respect to the power flow type. Results are compared with those obtained from other methods performance evaluation of the transmission, available in the literature.

Study on the Fuzzy Reliability of the Bearing in Planetary Transmission System for Heavy-Loaded Vehicles

Based on the fuzzy mathematics theory and reliability design methods, the fuzzy reliability of the rolling bearing in the planetary transmission system for heavy-loaded vehicles is analysed. The reliability and the fuzzy life expectancy of bearings in a practical planetary gear box are calculated in detail. The results show that the methods give a reference to the correct assessment of such type of bearing. Some measures to improve the reliability are also

Non-undercutting condition and parameter optimization for cycloid ball planetary transmission

The transmission performance of cycloid ball planetary transmission(CBPT) is affected by cycloid tooth undercutting directly, and the design of CBPT can be optimized by the non-undercutting condition. Firstly, the theoretical equation of cycloid tooth is given, and the curvature radius of cycloid tooth profile is derived. Secondly, according to the relationship between the curvature radius and the distribution circle of balls, the non-undercutting condition of cycloid tooth profile is established, and the non-undercutting critical condition is deduced. Finally, the validity of the non-undercutting critical condition is verified by simulation. The result shows that the non-undercutting critical condition can be used to optimize the design of CBPT.

Analysis of the Relationship Between the Meshing Stiffness and the Inherent Characteristics of Planetary Gear Transmission Mechanism

According to the relationship between the meshing stiffness and the inherent characteristics of a seven-speed three-row coupled planetary transmission mechanism,a equivalent concentrated mass dynamics model of the planetary transmission mechanism is established.The natural frequency of the planetary gear train at a specific gear is calculated and extracted.The relationship between the meshing stiffness of each row and the natural frequency of the system is analyzed,thereby avoiding possible resonance behavior by changing the meshing stiffness.These results show that the meshing stiffness,in its range of possible values,has nearly no effect on the low order natural frequency(<4.000.Hz),and that the time-varying meshing stiffness mainly affects the natural frequencies of the higher-and middle-order parts of the system.Changes of the natural frequencies lead to the change of the system's corresponding vibration mode,which will change the vibration situation of the system.

Automatic Scallion Seedling Feeding Mechanism with an Asymmetrical High-order Transmission Gear Train

The current automatic scallion-transplanting machine is a complicated mechanism composed of two linkage mechanisms and two band carriers.It delivers seedlings ine ciently because of the movement limitations of the linkage mechanism.This paper proposes a new high-order non-circular gear train for an automatic scallion-seedling feeding mechanism.The proposed gear train has an asymmetrical transmission ratio;i.e.,its transmission ratio varies.This allows the mechanism’s execution component to move in a long displacement and rotate in a large rotation angle.The long displacement enables the execution component to reach the designed working position,and the large rotation angle allows it to feed a scallion in the required pose.A mathematical model for calculating the asymmetrical transmission ratio was established according to the closure requirements and the full-cycle motion of the driven gear pitch curve.Then,the parameter-design model of the new seedling-feeding mechanism was established,based on precise pose points and trajectory-shape control points.Moreover,an aided-design program was developed to obtain the parameter-solution domain of the scallion-seedling feeding mechanism.The mechanism parameters,which met the seedling-feeding function,were optimized to determine the transmission ratio,using a program and a kinematic simulation.Finally,a prototype of the mechanism was produced,and a seedling-feeding experiment was carried out.One-thousand seedlings were tested at a rate of 100 seedlings per minute,and the statistical success rate was 93.4%.Thus,the automatic scallion-seedling feeding mechanism significantly improves the e ciency of automatically transplanting scallions.

The Influence of the Atmospheric Transmission for the Solar Radiation and Earth’s Surface Radiation on the Earth’s Climate

The physical and mathematical model of the planetary heat balance is developed to establish the influence of the atmospheric transmission for the solar radiation in the shortwave spectrum range and for the surface IR radiation in the longwave spectrum range on the Earth’s climate. It is shown the possibility of the decreas- ing of the atmospheric and surface temperatures with the decreasing of the atmospheric transmission for IR spectrum range, and this decreasing can’t be equilibrated with the change of the atmospheric transmission for the incoming solar radiation.

Investigation of Self Excited Torsional Vibrations of Different Configurations of Automatic Transmission Systems during Engagement

The vehicle drive line system is subjected to torsional vibration from different sources of the system such as;engine fluctuating torque, Hook’s joint and the final drive. However, the essential source is the friction torque induced in the friction elements, during their engagement. In the automatic transmission system, the planetary gear set includes several friction elements such as;clutch, band brakes, and one way clutch. During the engagement, severe torsional vibration is induced by friction which is noticeable by the passengers in the form of what so called vehicle shunt. In present paper, a torsional vibration model for Drive Line (DL) system includes three different configurations of automatic transmission is constructed. A computer program using MATLAB subroutines is implemented to obtain the system response. Effect of system parameters on the dynamic behavior and stability has been investigated. The system damping and the trend of the friction coefficient have an essential effect on the dynamic behavior and stability of the system. The system response is now predictable with change of the system parameters which opens up the opportunity in future to control the vibration level.

Study of Stress Sources and Critical Stress Combinations for the Input Shaft of a Longitudinally Mounted Four Speed Automotive Automatic Transmission Model

In the present paper;two models of the input shaft for a Longitudinal Mounted four Speed Automotive Automatic Transmission for the first time were introduced to describe the input shaft critical loads. In the first model;the DC (Direct Clutch) connects two gears together. This gives no change in the set torque (the set output torque equal to the set input torque). In the second model;the ODB (Over Drive Brake) fixes one element of the planetary set. This is resulting, the gear set gives reduction ratio (the set output torque is not equal to the set input torque). So, the transmission input shaft is worked under two different working operating conditions of torque. Also, it is loaded by a two vertical loads which are coming from the turbine and planetary set loads respectively. They are shown that there are three critical combinations of forces (contact force, shear force, and normal force) applied on the input shaft. The critical forces can be possibility exist three types of cracks for the input shaft cross section they are: transverse (torsion stress), longitudinal (bending stress), and vertical (shear stress). The three cracks are studied in this article. The article considers three stress factors: shearing torsion stress, shear stress, and bending stress.

微型行星齿轮传动设计与分析

提出一种应用于某航空发动机中空气涡轮起动机的微型行星齿轮传动设计方案,对传动系统的构型进行结构设计、参数匹配;采用有限元分析软件ANSYS对其重要零部件进行强度校核,基于正交试验法对减速器结构进行优化,为微型行星减速结构在航空发动机起动机等航空产品中的推广与应用提供理论支撑。

某金属带式无级变速器振动仿真分析与多工况下试验验证

为分析某金属带式无级变速器(CVT)振动产生机理,采用集中参数法建立双级行星齿轮非线性扭转动力学模型,应用四阶龙格库塔方法进行动态响应求解,利用ADAMS软件进行动力学仿真,对动态响应进行验证,进行CVT振动台架试验测试。研究结果表明:四阶龙格库塔方法与ADAMS动态仿真得到的动态响应结果基本一致;台架试验结果表明前进挡转速为2500 r/min时,低速挡输入轴轴向位置的振动加速度最大为0.623 m/s^(2),转速为1000 r/min时,低速挡输入轴轴向位置的加速度最大为0.309 m/s^(2);倒挡工况下,转速为2500 r/min时,倒挡输入轴轴向位置的振动加速度最大为0.703 m/s^(2),转速1000 r/min时,倒挡输入轴轴向位置的加速度最大为0.504 m/s^(2);倒挡工况下的振动加速度幅值比前进挡高12.85%;倒挡阶次谱中54.4阶和108.8阶振动信号最为明显,挡位切换过程中双级行星齿轮啮合次数增多,啮合间隙是CVT在倒挡动力传递中振动增大的主要原因。

重型液力自动变速器行星排非线性动力学分析

建立了重型液力自动变速器在某挡位下行星齿轮传动系统的非线性纯扭转动力学模型,该挡位工作模式充分体现了行星排之间的复合关系,该动力学模型综合考虑了时变啮合刚度、齿侧间隙与啮合误差幅值等系统内部激励因素,在此基础上推导出系统在广义坐标下的无量纲动力学方程。采用4阶龙格-库塔法对非线性微分方程组进行求解,得到了系统的非线性动态响应。综合运用时域响应、频域响应、相平面图、系统分岔和Poincare截面研究了具体的输入转速与系统响应的关系,得出了该挡位下的合理转速。研究了复合结构导致的各级行星排之间的响应差异,发现单个行星排可以影响甚至决定整个传动系统的响应,可以此为根据指导生产制造,降低生产成本。

重载行星轮系安装误差对系统均载性能的影响

行星轮安装误差的存在会导致行星轮系产生不均载问题,进而会影响减速器的传动性能和寿命。以往的研究未明确定义不同角度下的安装误差对系统均载性能的影响,并且关于多行星轮对系统均载影响的研究(在不同安装误差和不同输入功率下)也较少。为此,研究了实际应用中行星轮系安装误差对系统均载性能的影响。首先,以重载四行星轮系为研究对象,建立了行星轮径向和切向安装误差的综合误差表达形式;然后,基于轮系的传动模型,分析了单行星轮不同安装误差角和误差数值对系统均载的影响;最后,在单行星轮的基础上分析了不同工况和误差配置下多行星轮对系统均载的影响。研究结果表明:行星轮的切向安装误差对系统均载影响最大,径向安装误差对系统均载影响最小,当单行星轮安装误差数值为60μm,安装误差角θ从径向往切向方向靠近时,行星系统的均载系数增大了9.6%;误差绝对值越大,均载系数越大,当单行星轮安装误差数值从-30μm到-60μm时,系统的均载系数增大了4.6%;多行星轮存在切向安装误差对系统均载的影响可以用有效误差来衡量;齿轮承载范围内,随着输入功率的增大,安装误差对系统均载的影响逐渐减小。

齿面粗糙度对风电齿轮箱行星轮系动力学特性影响

为研究齿面粗糙度对行星轮系动力学特性的影响,提出行星轮系齿轮副动态承载接触分析与系统振动位移耦合方法。以某型兆瓦级风电齿轮箱行星轮系为研究对象,基于分形理论对轮齿粗糙表面进行分形表征,通过齿轮副啮合变形协调条件,构建齿面动态承载接触状态与构件振动位移、粗糙齿面啮合误差以及摩擦力的关联关系,建立风电齿轮箱行星轮系动力学模型,分析粗糙齿面啮合误差与摩擦力对系统动态特性的影响。结果表明:随着粗糙度的增大,齿面载荷峰值与波动幅值增大,动态啮合刚度幅值出现明显波动,均载性能降低;增大粗糙度会降低行星轮系临界转速,在低转速区域内,其具有激励增振作用,而在临界转速区域附近,其具有阻尼减振作用;摩擦力主要影响行星轮系各构件振动位移,可改变动态啮合力在少齿啮合区的幅值。

考虑啮合误差的复式行星传动系统均载特性研究

为研究复式行星传动系统的均载特性及影响均载特性的因素,通过势能法建立齿轮刚度求解模型,求解了传动系统的时变啮合刚度;计入阻尼、时变啮合刚度、啮合误差等因素影响,采用集中质量法建立了系统的平移-扭转耦合动力学模型,利用Newmark-β积分法求解了系统的动态响应,以均载系数量化均载性能,分析了转速、负载及单构件和多构件偏心误差对系统均载性能的影响。分析结果表明,提高转速会降低系统的均载性能,增加负载会提高系统的均载性能;偏心误差的增大会使系统的均载性能降低,当偏心误差同时作用在内啮合的构件上时会使均载系数下降3.1%;当同类行星轮的偏心误差以旋转中心作用时,会有效降低偏心误差对系统均载性能的影响。

基于故障树和贝叶斯网络的履带车辆行星变速机构可靠性分析

行星变速机构作为履带车辆传动系统的核心部件,其可靠性直接影响履带车辆的正常运行。以履带车辆行星变速机构为研究对象,基于实测试验结果建立故障树,将故障树转化为贝叶斯网络(Bayesian Network,BN)模型,并考虑行星变速机构正常、普通故障、严重故障3种状态进行可靠性分析。研究结果表明,行星变速机构失效概率为89.34×10^(-8)h^(-1),其工作400 h的可靠度为0.99964,符合设计要求;利用贝叶斯网络双向计算的功能,可知当行星变速机构发生失效,由主轴断裂或摩擦片烧蚀、翘曲、断裂或齿轮疲劳断齿引起的可能性较大。为后续装备检修、改进设计提供理论依据。

考虑误差下的变位齿轮行星轮系载荷特性研究

针对制造误差和安装误差使得变位齿轮行星轮系行星轮在径向和周向的安装位置与无偏移值存在偏差,进而使行星轮间所受载荷不均匀的问题,开展了变位齿轮行星轮系载荷特性研究。基于转子动力学理论,考虑时变刚度和行星轮的径向与周向偏移,建立了变位齿轮行星传动系统5自由度动力学模型;采用龙格库塔法求解了系统的响应和频域图,研究了变位齿轮行星轮系的载荷特性,分析了在不同径向偏移量、周向偏移量、复合偏移量情况下的行星轮间载荷分布特性,探讨了行星轮的径向与周向偏移对行星轮系载荷分配的影响,得到了变位齿轮行星轮系载荷振动幅值在时间和频率下的变化规律。仿真结果表明,考虑误差的行星轮系载荷特性与无偏移情况下的载荷特性有较大的差异,其幅值受径向偏移的影响较大,其中,径向偏移量大对行星轮所受载荷的影响最大;在安装过程中,行星轮的微小偏移都可能导致载荷特性的巨大变化。搭建了行星传动系统振动测试试验平台,测试了行星减速机壳体的倍频振动响应信号,得到了行星传动系统载荷与振动响应之间的关系。试验结果的振幅变化趋势与仿真分析结果中的振幅变化趋势相似,证明所建立的动力学模型及理论计算比较准确。

行星传动系统均载与动载系数试验测量改进设计

试验测量行星传动系统均载与动载系数的精准度是评价系统动态性能的基础。针对现有行星传动系统均载与动载系数测量方法存在灵敏度与精度欠佳、系数测试算法缺失、测试应力点存误等问题,本文提出了一种方便、实用且具有高精度的行星传动系统均载与动载系数测试方法,定义了系统系数的测试算法与概念,明确了精确应力测试位置点及不同位置间差异性,采用应变片电桥传感器串并联设计,实现了拉压应力叠加、温度补偿以及繁琐标定免除等优点,为精准测取行星传动系统均载与动载性能提供了重要的理论基础和技术手段。

考虑齿廓修形的行星齿轮传动系统动力学特性研究

基于对行星齿轮传动系统高传动效率和低噪音等要求,以行星齿轮传动系统为研究对象,采用集中参数法建立了考虑偏心误差和安装误差的斜齿行星齿轮传动系统的弯⁃扭⁃轴耦合动力学模型,利用四阶Runge⁃Kutta法求解动力学方程得到行星齿轮的动态啮合力、动态传动误差和动载系数等动态特性,并以此为评价指标展开行星齿轮的修形研究。建立了齿廓修形后的齿面方程和考虑齿面修形的动力学方程,研究不同修形量的行星齿轮传动系统动态特性变化。研究结果表明,随着修形量的增大,行星齿轮的动态啮合力、动态传动误差和动载系数都有不同程度的降低,降到最低值后又开始增大,最终确定齿轮的合理修形量。经过整机性能测试发现合理修形下的行星减速器振动噪声降低、传动性能提升,为行星齿轮传动系统的减振降噪、传动效率提升设计提供了理论支撑。

特性参数连续可变复合传动的优化与选型

复合传动系的核心技术在于匹配,基于不同复合传动系统中各项评价指标实际的重要性与适应性,从所有可能适用的功率分流方案中选出最优方案,完成一次完整的优化选型设计。为避免优秀方案被漏选的问题,对12种复合传动的速比和转矩进行分析,根据传动系统各部件的转矩能力,提出传动路线中3个关键位置的转矩系数。以速比变化范围和3个转矩系数为目标函数,使用非支配遗传算法NSGA-II优化两个固定齿轮副传动比,得出12种复合传动的综合最优状态。基于评价指标重要性与适应性,提出一套行星排特性参数连续可变复合传动系统的分级多步选型方法,完成一次完整的优化选型设计。相比优化前的系统:速比范围提高24%,最大输出转矩提高18.92%,效率提高2.25%。