Design and Experimental Research on Seedling Pick-Up Mechanism of Planetary Gear Train with Combined Non-circular Gear Transmission

Currently, transplanting mechanisms for dryland plug seedlings in China are mainly semiautomatic and have low efficiency. The rotary seedling pick-up mechanism with a planetary gear train for non-uniform intermittent transmission, and a concave and convex locking arc device, has a large rigid impact. To solve these problems, according to the design requirements for a dryland plug seedling transplanting mechanism, a rotary seedling pick-up mechanism of a planetary gear train with combined non-circular gear transmission of incomplete eccentric circular and noncircular gears was proposed. This has the characteristics of two-times greater fluctuation of the transmission ratio in a cycle, and can achieve a non-uniform continuous drive. Through analysis of the working principle of the seedling pick-up mechanism, its kinematics model was established. The human–computer interaction optimization method and self-developed computer-aided analysis and optimization software were used to obtain a set of parameters that satisfy the operation requirements of the seedling pick-up mechanism. According to the optimized parameters, the structure of the seedling pick-up mechanism was designed, a virtual prototype of the mechanism was created, and a physical prototype was manufactured. A virtual motion simulation of the mechanism was performed, high-speed photographic kinematics tests were conducted, and the kinematic properties of the physical prototype were investigated, whereby the correctness of the theoretical model and the optimized design of the mechanism were verified. Further, laboratory seedling pick-up tests were conducted. The success ratio of seedling pick-up was 93.8% when the seedling pick-up efficiency of the mechanism was 60 plants per minute per row, indicating that the mechanism has a high efficiency and success ratio for seedling pick-up and can be applied to a dryland plug seedling transplanter.

Kinematic Modeling and Characteristic Analysis of Eccentric Conjugate Non-circular Gear & Crank-Rocker & Gears Train Weft Insertion Mechanism

A novel weft insertion mechanism named eccentric conjugate non-circular gear & crank-rocker & gears train weft insertion mechanism was proposed in order to better meet the requirements of rapier loom's weft insertion mechanism as well as reduce the manufacturing difficulty. Meanwhile, based on the working principle of this mechanism, kinematical mathematic models of this mechanism were established and an aided analysis and simulation software was compiled. The influences of eccentricity ratio, deformation coefficient, and other important parameters on the kinematics characteristics of this mechanism were analyzed by using the software. A group of preferable parameters which could meet the requirements of weft insertion technology were obtained by means of human-computer interactive optimization method. The maximum velocity, maximum acceleration, and variation of acceleration of this mechanism are smaller than those of the conjugate cam weft insertion mechanism applied on TT96 rapier loom under the conditions of the same unilateral total stroke of rapier head and the same rotary speed of loom spindle; meanwhile the other demands of weaving technology can be met by this novel weft insertion mechanism.

Design and Experiment of Non-circular Combined Gear Train Beating-up Mechanism

The most important performance of a beating-up mechanism is that the dwelling time of the sley must ensure the completion of the weft insertion. To meet this requirement, a new non-circular combined gear train beating-up mechanism which is composed of two-stage planetary gear trains is proposed. The first-stage is a Fourier planetary gear train and the second-stage is a non-circular planetary gear train. For designing of this new mechanism, the ideal kinematic equations of the sley are constructed first. Then the kinematic model of the first-stage Fourier planetary gear train is established and the reverse solution for the pitch curves of the second-stage non-circular gears is deduced. With a computer-aided design program, the influences of several important parameters on the pitch curves of the second-stage non-circular gears are analyzed, and a set of preferable structural parameters are obtained. Finally, a test bed of this mechanism is developed and the experimental results show that this new beating-up mechanism can achieve the designed dwelling time, namely it can meet the requirements of beating-up process.

Reliability Analysis for a Gear-Rack Based on Combination of Simulation and Experiment

In order to analyze the gear-rack reliability under the most serious limit loads which was the new-type transmission mechanism of aircraft slats,the gear-rack static strength under the single tooth meshing was analyzed based on the simulation and experiment. Then,it randomized the load of gear-rack based on the precise finite element analysis( FEA) model,and analyzed the static strength reliability of the gear-rack. Finally,the gear-rack under the most dangerous situation has not been destroyed and it also has a high reliability.

Calculating method of contact stress for non-circular gears

According to Hertz theory, the difference of contact stress for non-circular gears and equivalent gears is compared in the paper, a calculating method of contact stress for non-circular gears by using equivalent gears is researched, and computing formulas of power and rotation speed for equivalent gears are deduced. A numerical simulation of contact stress for non-circular gears has also been conducted based on the finite element method. By the comparison of fitting curves, the feasibility of using equivalent gears instead of non-circular gears to calculate the contact stress is testified.

Research on Design Method of Non-Circular Gear Pair with Double Generating Angles

In order to enhance the bearing capacity of non-circular gear pair, the non-circular gear pair with double generating angles is proposed based on the design idea of unsymmetrical gear with double pressure angles. The tooth profile is designed by generating cutting theory, the pure rolling mathematic model that the center line of unsymmetrical rack roll along non-circular pitch curve is built, the digital model of non-circular gear with double generating angles is created through the second development method of CAD software, and then the drive characteristic and tooth strength are analyzed. The results show that the design method for double generating angles non-circular gear proposed in this paper is feasible, which is significant to improve the bearing capacity of non-circular gear pair.

非对称齿轮啮合刚度精确求解及齿廓参数分析

非对称齿轮是一种轮齿两侧采用不同压力角的新型渐开线齿轮,其齿廓参数对齿轮齿廓形状、运动特性、承载能力、传动效率和动力学特性等有至关重要的影响。基于齿轮啮合原理,运用李特文矢量法,根据加工刀具齿廓参数方程推导了非对称齿轮全齿廓方程;应用材料力学理论,建立非对称齿轮时变啮合刚度的数值求解模型,并通过有限元方法验证了该模型的有效性。基于所建立数值分析模型进行算例研究,总结了刀具圆角、压力角和变位系数对齿轮啮合刚度和重合度的影响规律。结果表明,随着轮齿工作侧压力角的增大,齿轮齿根厚度增加,单齿对的啮合刚度加大,齿轮的承载能力得到有效提高。加工工作侧轮齿齿廓刀具圆角的增大,也有利于提高齿轮的啮合刚度;同时,工作侧齿廓压力角的增大会使齿轮的齿顶厚度降低、啮合重合度减小,会导致齿轮的齿顶强度和冲击韧性降低。非对称齿轮齿廓设计时,应根据实际工况合理设置压力角参数。

齿轨车辆牵引电机布置模式及系统耦合振动特性

为探究牵引电机布置模式对齿轨车辆动态特性及齿轮-齿轨啮合特性的影响,在考虑齿轮-齿轨非线性啮合行为及其动态时变激扰和轮轨非线性接触关系的条件下,分析了不同电机布置模式下的车辆动力学特性。以Strub齿轨系统为原型,建立了齿轨车辆-轨道垂纵耦合动力学模型,研究了三种不同电机驱动形式对齿轨车辆动态特性的影响规律,并在此基础上提出了适用于齿轨车辆的牵引电机布置方案。研究表明:牵引电机双置工况下齿轮啮合力和垂向、纵向振动加速度更小;其中电机双置时齿轮齿轨啮合力约为电机后置和前置时的50%,平直段齿轮垂向和纵向加速度的最大幅值差分别为4.04和6.01 m/s^(2),爬坡段电机后置时齿轮振动加速度最大,其垂向、纵向加速度幅值比电机双置时大45%;平直线路上电机后置与前置时齿轨车辆的舒适性较好,而爬坡段牵引电机双置模式下更好;鉴于齿轨车辆主要应用于爬坡线路,且爬坡时电机双置齿轨车辆的动力学指标最好,因此建议牵引电机双置为最优布置模式。

重心偏置下齿轨车辆系统的动态行为

针对大坡度下车辆动态特性受齿轨车辆重心偏置影响的问题,在解析齿轮齿轨啮合激扰产生机理的基础上,考虑齿轮齿轨啮合冲击与轮轨动态接触行为的扰动效应,建立齿轨系统车轨耦合动力学模型,并经过现场实验验证了模型的有效性;采用所建立的模型,探究平直段以及坡道段车体重心横纵偏置对驱动齿轮动态接触行为以及齿轨车辆运行安全平稳性的影响。结果表明:齿轨车辆存在重心偏置时,齿轮齿轨啮合激扰对车辆运行特性有显著影响;车体重心横向偏置对轮轨垂向力与轮重减载率呈线性影响,当重心横向偏置达到0.3 m时,轮轨垂向力达到75 kN,轮重减载率达到0.44;轮轨作用力除受车体重心偏置作用产生增减载外,亦受齿轮齿轨动态啮合影响产生剧烈振动;轮重减载率、车体垂向加速度与车体平稳性对车体重心纵向偏置较敏感,当车体重心后置0.2 m时,平直段的车体垂向加速度增大1.8倍,坡道段增大3.7倍,车体重心后置1 m时,车体平稳性达到最优。研究结论可为我国山地齿轨铁路设计及安全运维提供理论支撑。

大模数齿轮齿条副均匀磨损弯曲强度分析及验证

针对齿面磨损条件下大模数齿轮齿条啮合时的齿轮齿根弯曲强度问题,以三峡升船机齿轮齿条传动副为研究对象,搭建立式齿轮齿条起升机构工况模拟实验台,通过齿轮变位方法分析沿齿廓载荷、磨损后齿轮齿厚等相关参数的变化,对正常、1/12磨损、1/6磨损和1/4磨损的齿轮齿根弯曲应力进行解析计算和实验验证。结果表明:齿轮弯曲应力随着磨损加剧和载荷的增大而增大,单齿啮合区间的弯曲应力比双齿啮合区显著增大,单齿啮合占比时间随着磨损量的增加而增加,表明齿轮磨损劣化了传动系统工况,加速了传动系统的性能退化过程。通过对单、双齿段啮合弯曲应力进行定量分析,解析计算与实验验证的误差最大值为4.02%,处于较低水平,2种方法的结果相互验证,保证了分析的正确性和精度。

齿轮偏心对齿轨车辆动力学性能影响研究

为研究齿轮偏心对齿轨车辆动力学性能的影响,基于齿轮齿条传动原理与车辆动力学理论,使用SIMPACK软件建立了齿轨车辆多体动力学模型,研究了齿轮不同偏心量下的齿轮动态特性以及齿轨车辆直线运行平稳性和曲线运行安全性。仿真结果表明,齿轮齿条间的啮合冲击随齿轮偏心量的增加而逐渐增大,进而加剧车体的振动,使得齿轨车辆的直线运行时,车体振动加速度与平稳性指标增大,但相对横向振动,齿轮偏心对车体垂向振动影响更为明显。此外随齿轮偏心量的增加,齿轨车辆通过曲线时的脱轨系数和轮重减载率也有所增大。

自升式海洋平台升降装置自动润滑系统的设计与应用

目前国内船厂在建的自升式海洋平台,大多采用齿轮齿条式升降装置,也有部分配备了自动润滑系统,但由于设计或者选型不当等问题,导致自动润滑系统形同虚设,最后不得不转为人工涂抹润滑油脂。本文主要介绍齿轮齿条式海洋平台的升降装置的自动润滑系统的工作原理、设计要点和安装方法等,为此类平台的升降装置在作业时,提供一套完整、高效、系统的自动润滑技术解决方案。

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.

Research on stepless transmission utilizing noncircular gears

In view of the lack of systemic analysis for stepless transmission using noncircular gears, two basic noncircular gear units, an addition unit adopting differential mechanism and a multiplication unit applying a fixed gear train, are proposed. Then, the design methods of the noncircular gear pair of each unit, transmission ratio relationship, rotation angle relationship and key parameters with specific physical meanings are studied. The adjusting properties, composing strategy and varying range of transmission ratio etc. are investigated in detail for each unit. Following this, several examples of using a noncircular gear pair in the units and their manipulation technique are introduced.

海域天然气水合物保压取心钻具的研制与试验

天然气水合物的勘探和开发需要从地层中获取保压岩心进行地层的物化性测试、储量评估以及开采工艺等方面的研究。然而,钻探过程中,伴随温度和压力的改变,天然气水合物很容易发生分解,这给水合物钻探取心工作带来了很大的困难。为了解决天然气水合物保压取心钻具的保压可靠性问题,开展了一种新型齿轮-齿条关闭球阀式水合物保压取心钻具的研制,采用绳索打捞的提拉力驱动球阀工作。详细介绍了该保压取心钻具的结构和工作原理;计算了球阀的工作密封比压及打捞内管所需的提拉力;介绍了该保压取心钻具的室内试验和海试情况。研究表明:该水合物保压取心钻具的取心工艺简单、球阀翻转和密封性能良好、取心成功率高,各项功能和性能指标均达到了设计的要求。

基于势能原理的铰接支撑齿条-齿轮时变啮合刚度解析计算

齿轮齿条传动是一种重要的机械传动方式,其内部时变啮合刚度是一种主要的激励源,对系统振动噪声水平有着重要影响。针对齿轮齿条时变啮合刚度高效、准确的解析计算问题,提出了一种基于势能原理的铰接支撑齿条与齿轮啮合刚度解析计算方法,计算获得了不同参数下的齿轮齿条时变啮合刚度,并利用有限元法验证了建立的解析计算模型的正确性。同时,利用建立的解析计算方法分析了垂向间隙、压力角、齿条长度等参数对齿轮齿条时变啮合刚度的影响规律。结果表明,建立的解析计算方法能够准确计算齿轮齿条时变啮合刚度,为齿轮齿条传动系统动态特性分析提供了理论支撑。

Reverse design and tests of vegetable plug seedling pick-up mechanism of planetary gear train with non-circular gears

In the previous research,the seedling pick-up mechanism of the planetary gear train with incomplete eccentric circular gear and non-circular gears for vegetable plug seedlings still has two shortcomings.One is that not enough seedling pick-up depth leads to a low success ratio of seedling pick-up at high rotation speeds,the other is that the smaller seedling pushing angle results in poor seedling pushing effect.Therefore,the reverse design of the seedling pick-up mechanism based on its motion trajectory was carried out.The local trajectory of seedling pick-up and seedling pushing sections was adjusted to obtain the theoretical motion trajectory of the seedling pick-up mechanism.The cubic non-uniform B-spline curve was used to fit the adjusted trajectory.A novel seedling pick-up mechanism of the planetary gear train with non-circular gears was proposed,including three combined non-circular gears,four non-circular gears,one planetary carrier,and two seedling pick-up arms.The reverse design model of the mechanism was established.The analysis and design software of the mechanism was developed to obtain the mechanism parameters meeting design requirements.The virtual prototype of the mechanism was established and its physical prototype was manufactured.Through the virtual motion simulation and high-speed photographic kinematics bench tests of the mechanism,the kinematic model and results of reverse design of the mechanism were verified,with the kinematic performances of the mechanism prototype studied.The seedling pick-up tests of the mechanism were conducted in the laboratory.The success ratios of seedling pick-up were 94.2%,95.6% and 90.2% while the seedling pick-up efficiencies of the mechanism were 60,80 and 100 plants per minute per row,respectively.Besides,the seedling pushing effect was improved mush because of the greater seedling pushing angle.The seedling pick-up mechanism through revise design is of high value to be applied in the practical vegetable plug seedling transplanters.

齿轮齿条传动的运动精度计算分析

齿轮齿条传动可以实现较高精度、较长行程的直线运动。针对齿轮、齿条以及相关结构的加工和装配精度对运动精度的影响进行分析。以某典型齿轮齿条传动方案为例,给出可实现运动精度指标的选型和计算过程,为同类直线传动系统的设计提供参考。

基于弹簧刚度法的螺栓分布研究

螺栓组载荷分布不均是齿轮齿条钻机产生振动甚至损坏的重要原因之一。工程中,螺栓连接点常常会受到复杂的时变低速重载,螺栓组容易因载荷分布不均而发生断裂,从而影响钻机的稳定性。为研究不同螺栓分布情况下螺栓组所受应力情况,通过建立多螺栓连接的力学模型对螺栓载荷分布情况进行分析,并在此基础上考虑结构复杂的连接件提出一种多螺栓连接载荷计算方法。设计并进行了试验研究和有限元分析,通过对比其结果,验证了计算方法的准确性。基于提出的理论计算方法,给出载荷作用下螺栓剪切应力的分布规律,对比了螺栓均匀分布模型和非均匀分布模型的剪切应力分布特点,结果发现非均匀螺栓分布的承载分布均匀性要优于均匀分布的螺栓。

齿轮齿条应用于井下采油设备的动力学分析

将齿轮齿条机构用于井下采油设备,可以避免有杆式采油设备的杆管偏磨。介绍了井下采油设备的组成与工作原理,对齿轮齿条机构的强度进行了校核和有限元分析,建立了齿轮齿条传动机构的动力学模型并进行动力学仿真。结果显示,齿轮齿条机构强度符合理论要求,但轮齿啮合时会出现周期性振动,且齿条换向时存在惯性载荷冲击,在许可范围内,验证了齿轮齿条机构应用于井下的可行性。