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.

Reverse Design and Test of Non-circular Gear & Crank-Rocker & Gear Trains Weft Insertion Mechanism

For the purpose of obtaining satisfactory performance of the non-circular gear & crank-rocker & gear trains (NCCRG) weft insertion mechanism which was proposed in this paper, the ideal kinematic curve of this weft insertion mechanism was given, and the reverse solution models of this mechanism were established. A reverse design and simulation software was compiled based on Visual Basic 6.0 to obtain the mechanism parameters, including the pitch curves and tooth profiles of the non-circular gears. A test-bed of this mechanism was developed according to these parameters. The kinematic performance of this weft insertion mechanism was tested by high-speed video tape recorder with its corresponding video analytical software Blaster's MAS. And the test results were identical with the theoretical calculation. Compared with the conjugate cam weft insertion mechanism which is applied on TT96 rapier loom, under the condition of same weft insertion rate, the variation of acceleration of this mechanism is smaller. This novel weft insertion mechanism can meet the requirements of weft insertion on rapier looms with smooth and steady motion.

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.

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.

Matching between mechanics and thermodynamics among 4 individual strokes in a 4-stroke engine by non-circular gear mechanism

The relationship between engine mechanics and thermo-dynamics has been investigated by means of numerical simulation.The inherent mismatching between the mechanical behaviors and the thermodynamic process in internal combustion engine is identified,which is believed to be one of the important limiting factors of energy efficiency for conventional engines available in the current market.An approach for engine efficiency improvement through optimal matching between mechanics and thermodynamics(OMBMT)is proposed.An ideal matching model is defined and the conflicts due to the constraints among the mapping strokes in a 4-stroke engine are analyzed.A novel mechanical model is built for approaching optimal matching among all 4 individual strokes in a 4-stroke spark-ignition engine,which is composed of non-circular gears(NCG)and integrated with conventional slider crank engine mechanism.By means of digital mechanical model and numerical simulation,the matching gains among all 4 strokes are defined and calculated for quantifying the NCG engine efficiency improvement by comparing with a baseline engine.The potentials with the OMBMT implemented and the enhancements made by NCG mechanism for engines in terms of overall engine efficiency are reported.Based on the results achieved,it is recommended that the feasibility studies and the experimental validations should be conducted to verify the engine matching concept and effectiveness of the NCG mechanism engine model proposed,and the engine performance and NCG design parameters should be further optimized.

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.

考虑金属带张紧力影响的CVT噪声分析与优化

金属带式CVT在传递转矩时,会在主动和被动带轮轴间产生轴间作用力,使被动带轮轴发生变形,影响被动带轮轴齿轮与中间轴齿轮的啮合,产生偏载,增大齿轮间的传递误差,从而加大变速器的啸叫噪声。本文中以某款金属带式CVT为研究对象,对其进行动力学分析,并通过仿真和试验,分析验证了金属带张紧力对变速器啸叫噪声的影响,同时,以最小化系统变形和齿面载荷密度为目标函数,采用基于遗传算法的多目标优化算法对该齿轮副齿轮的修形参数进行优化。结果表明,金属带张紧力引起的轴间作用力对被动带轮轴齿轮和中间轴齿轮的偏载情况影响较大,它增强了变速器加速过程中的啸叫噪声,而优化后的齿轮,降低了变速器的啸叫噪声,提高了变速器的声品质。

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.

CVT封闭的2K-H型差动轮系啮合效率分析

针对封闭式无级变速器内部容易发生功率循环而造成效率降低的问题,以输入耦合CVT(Continuously Variable Transmission)传动系统为研究对象,简单地介绍了其基本结构及工作原理,在无能量损失的理想状态下详细推导了该传动系统实现功率分流的充分条件。其次,在该充分条件下简化了输入耦合CVT传动系统中起汇流作用的2K-H型差动轮系啮合效率表达式,得到了影响啮合效率的输入构件结构参数和运动状态等因素,求证了其获得最大值的条件。最后,通过实例验证了所得到的2K-H型差动轮系啮合效率最大条件的正确性。结果表明,该条件从设计的角度保证了2K-H型差动轮系啮合效率最大,是一种行之有效的设计方法。

NOVEL COMPOSITE CVT SYSTEMS WITH DIVERGING AND DUAL-MODE CONVERGING POWER FLOW

A new type of composite CVT(continuously variable transmission) systemsfeatured by power flow divergence and dual-mode convergence, capable of improving CVT's efficiencyand power capacity or making AMTs(automated manual transmissions) become continuously variable, isstudied. With specific mechano-mechanical and electromechanical composite CVT systems as detailedexamples, its basic working principles are expatiated. General methods and key points in designingand realizing such systems are also analyzed and discussed.

DESIGN OF NONCIRCULAR GEARS WITH DISCONTINUOUS PITCH CURVE

When the noncircular gear pair is applied to the continuously variable transmission （CVT） with gear, the transmission ratio function is discontinuous. In accordance with this unique characteristic, a new approach to design and analyze noncircular gears with discontinuous pitch curve is proposed. The design courses of various noncircular gear pairs with discontinuous pitch curve are unified based on the numerical algorithm of spline fitting and ＂fairing boundary condition＂. According to the particularity of discontinuous pitch curve, the rules and procedures for teeth distribution are recommended. It is explained in detail why the undercut is formed and how to manage the undercut based on meshing principle.In addition, the calculation formulas for each tooth profile segment are also derived. If the tooth profile data are calculated, the measurement and the incision process for noncircular gear can be conducted and the CAD simulation can be achieved easily. To ensure the continuity of the transmission, the transmission interference of the tooth which is located at the pitch curve joint point is managed by utilizing Bezier curve with CAD software. And the contact ratio of gear pair is obtained. The case study shows that this approach is successful and opens up a new way for the design of noncircular gear.

新型CVT无级变速器动力传递机构的设计

详细叙述了一种新型CVT无级变速器动力传动机构的设计。其中推杆和楔型滑块的运动可实现相应的变速;为了使变速器的传动比达到要求,可以在从动轮后加装行星齿轮机构,方案在一定程度上具有可行性。

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.

CVT车型驾驶性提升方法研究

本文主要研究了搭载无级自动变速器(CVT)车型驾驶性提升的方法。从优化CVT速比控制,提升换挡响应的核心机理出发,分别从驱动力设计、硬件和软件控制方法、最优驾驶性的换挡设计、运动模式开发等方面优化和提升CVT车型的驾驶性,为驾驶员提供动力充足、平顺的驾驶体验,提高CVT车型的驾驶性认可度。

金属带式无级变速器电液控制系统

金属带式无级变速器机液控制系统通用性差,难以实现夹紧力和速比的任意控制。提出了一种使用液压系统内反馈机制的单一液压源开环电液控制系统,并给出了具体的解决方案。详细阐释了电液作动原理并建立了系统的模型。通过对电液控制系统进行硬件在环仿真,同时与实车实验所测得的数据进行分析表明,该电液控制系统结构简单,响应快速准确,系统稳定可靠。

功率分流无级变速器多种组合传动效率计算分析

功率分流无级变速器(PS-CVT),是一种新型无级变速系统,在结构上其结合了CVT和机械式齿轮变速器的优点,同时还强化了功率传递方面能力。由于行星齿轮效率与输入输出元件相关,再结合并联式、串联式PS-CVT的各种组合,PS-CVT传动效率计算较繁琐。推导出一适合并联、串联各种组合的PS-CVT传动效率计算公式,并通过计算分析,各选出一种并联、串联结构,其传动效率最高,研究成果对设计PS-CVT机械结构有一定指导意义。

弧块-滚柱式低副超越离合器的研究

针对传统超越离合器的运动副效率低、功率小、寿命短的问题,提出了弧块-滚柱式低副超越离合器.对其主要结构、工作原理、自锁条件、传动能力、接合效率和启闭特性进行了研究.实例计算表明,弧块-滚柱式超越离合器与同等尺寸的传统滚柱式超越离合器相比,具有较大的传动能力和较高的接合效率.同时,试验证明了该离合器具有自锁可靠,启闭灵敏,传动能力大和抗冲击能力强等优点,为解决超越离合器的性能问题提供了新的途径.

封闭式锥盘无级变速器无循环功率条件及应用

通过对封闭式行星锥盘无级变速器运动学和系统内部功率流、功率分配系数与封闭系统内部功率流的关系的分析,建立了功率分配系数与系统内部各单元传动比的关系表达式,确定了行星锥盘无级变速器无循环功率的必要条件,列出了16种无循环功率的差动轮系单元与行星锥盘无级变速器的组合形式.为无循环功率的封闭式行星锥盘无级变速器的设计提供了一种简便的分析方法.

行星齿轮功率分流式无级变速器液压控制系统设计

针对无带传动的新型行星齿轮功率分流式无级变速器的传动方案,设计液压控制系统,采用两个换挡电磁阀组合控制相关离合器、制动器工作以实现不同基本挡位,利用数字阀控制起步离合器的平稳起步和基本挡与无级变速挡的平稳换挡。该液压控制系统结构简单,控制方便,具有较好的实用价值。