Clearance Influence on Dynamic Response of Intermittent Roller Chain Drive

The clearances appear in chain link hinges induced by manufacturing tolerance or wear of components are the most important factor that influences the dynamic performance of the intermittent roller chain drives. Due to the existence of the clearances in chain link hinges, the serious impact vibration phenomenon which influences the stability and the position accuracy of the chain drive system would be caused in the intermittent motion. But, the problem may be that a reasonable modeling on the chain with clearances is difficult due to the large clearance＇s number in chain system and the fact that the clearance＇ size are different. Currently, the studies on the dynamics of the intermittent roller chain considering the multi-clearance＇ joints are rare. Most research works have only focused on the constant moving chains. Taking the intermittent roller chain system as an object, this paper designs and builds the experimental device of this kind of mechanical system. The Longitudinal vibration response of the intermittent chain under the different motion laws was tested. The experimental study shows that the clearances presented in chain link hinges can cause severe impact vibration in the intermittent motion of chain. In subsequent work, the dynamic model of the intermittent roller chain system with the multi-clearance＇ joints was established. By calculating the dynamic response of this kind of mechanical system under the different motion laws, the effect of the clearances on the dynamic response of the intermittent chain drive system was analyzed. The theoretical simulation shows that the serious impact vibration phenomenon of the chain system can be caused by the clearances at the start accelerating period, and the chain drive system is often accompanied by the severe shock and vibration at the moment that the chain moves from the acceleration period to deceleration period. The research conclusions made by the experimental and theoretical studies indicate that the use of motion laws with small and continuous jerk at conversion point can effectively suppress the impact vibration at this point caused by clearances＇ effect. Additionally, the use of nonsymmetrical motion laws with small jerk approaching the end of the indexing period can obtain a smaller residual vibration. The presented motion law can provide an important reference for the improvement of the dynamic performance of the intermittent chain drive systems.

Dynamic Modeling of a Roller Chain Drive System Considering the Flexibility of Input Shaft

Roller chain drives are widely used in various high-speed, high-load and power transmission applications, but their complex dynamic behavior is not well researched. Most studies were only focused on the analysis of the vibration of chain tight span, and in these models, many factors are neglected. In this paper, a mathematical model is developed to calculate the dynamic response of a roller chain drive working at constant or variable speed condition. In the model, the complete chain transmission with two sprockets and the necessary tight and slack spans is used. The effect of the flexibility of input shaft on dynamic response of the chain system is taken into account, as well as the elastic deformation in the chain, the inertial forces, the gravity and the torque on driven shaft. The nonlinear equations of movement are derived from using Lagrange equations and solved numerically. Given the center distance and the two initial position angles of teeth on driving and driven sprockets corresponding to the first seating roller on each side of the tight span, dynamics of any roller chain drive with two sprockets and two spans can be analyzed by the procedure. Finally, a numerical example is given and the validity of the procedure developed is demonstrated by analyzing the dynamic behavior of a typical roller chain drive. The model can well simulate the transverse and longitudinal vibration of the chain spans and the torsional vibration of the sprockets. This study can provide an effective method for the analysis of the dynamic characteristics of all the chain drive systems.

Modal analysis on transverse vibration of axially moving roller chain coupled with lumped mass

The modal characteristics of the transverse vibration of an axially moving roller chain coupled with lumped mass were analyzed.The chain system was modeled by using the multi-body dynamics theory and the governing equations were derived by means of Lagrange's equations.The effects of the parameters,such as the axially moving velocity of the chain,the tension force,the weight of lumped mass and its time-variable assign position in chain span,on the modal characteristics of transverse vibration for roller chain were investigated.The numerical examples were given.It is found that the natural frequencies and the corresponding mode shapes of the transverse vibration for roller chain coupled with lumped mass change significantly when the variations of above parameters are considered.With the movement of the chain strand,the natural frequencies present a fluctuating phenomenon,which is different from the uniform chain.The higher the order of mode is,the greater the fluctuating magnitude and frequency are.

Roller Screw and Threaded Chain Speed Reducer: An Experimental Evaluation

We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuration lessens wear, increases load capacity, and improves efficiency. The threaded chain consists of nut-shaped links. This paper presents the results of tests carried out on a prototype with a reduction ratio of 46.

对链条零件加工工艺的探讨

现阶段,链条在动力传动中得到了大规模的应用,特别是在速度不高、功率强,以及温、高压、多尘等恶劣环境中。为防止链传动过程中产生“弹性打滑”现象,需要杜绝链条长时间工作下出现的磨损情况,防止链条的传动平稳性受到干扰,在工作时生成附加载荷、振动与噪音等。本研究以滚子链为案例,探讨滚子链链条链板、套筒、销轴、滚子等零件的加工工艺,旨在分析加工链条零件的工艺,满足链传动动力传递标准。

滚子链外链节压出力计算与分析

外链节的压出力是影响滚子链质量的重要指标之一,它与销轴和链板孔之间的过盈量有关。以往外链节压出力的分析中,只考虑了弹性变形的问题,在此基础上,将链板销轴组合简化为厚壁圆筒组合,运用弹性力学和塑性力学知识,进一步分析过盈量与压出力的关系,计算出各种型号外链节开始发生塑性变形的弹性极限过盈量。根据米塞斯屈服条件,推导出在弹塑性变形状态下压出力和过盈量之间的计算方法和计算公式。根据公式计算了多种型号链条外链节的有效弹性极限过盈量。

WEAR FAILURE MECHANISM AND MULTI-IMPACT PROPERTY OF AUTOMOTIVE ENGINE CHAIN

The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area between pin, bush and roller are also analyzed based on scanning electron microscope. The results show that the main wear mechanism of automotive engine chain is fatigue wear, and its failure mechanism is the forming, extending and flaking of cracks on top layer of pin and bush. In addition, the material, hot-treatment method and shaping technique for roller have a great influence upon the resistance to multi-impact. Ensuring sufficient strength and plasticity of roller, as well as adopting suitable shaping technique are the effective method to increase its resistance to multi-impact.

一种可变中心距链条张紧装置

一种可变中心距链条张紧装置安装在自动辊道升降式振动台上。在辊道升降时会导致固定链轮和辊道链轮中心距变化。用此装置可以在链轮中心距变化时使链条一直保持张紧状态,防止辊道下降时中心距变小而使链条与设备相碰。此次介绍一种可变中心距链条张紧装置,具有结构灵巧紧凑、安装调整便捷、可靠性高、有效保护链条等优点。

链式气动冲切自动化干红枣去核机设计

红枣去核是干红枣产业深加工的关键技术,现有的红枣去核机普遍存在自动化程度低、人工辅助多、去核机构复杂等缺点。为解决现有的技术问题,该文研究设计了一种链式气动冲切自动化干红枣去核机,整机由单片机程序控制所有工序动作,包括辊轮输送链上料、摄像头拍照检测红枣排布情况、辊轮夹持链定位、间歇时间内气缸驱动旋转插杆去核机构去核和卸料输出。选择横径范围为20～30 mm,纵径范围为35～45 mm的干制红枣去核对象进行样机试验,结果为红枣定位率≥98.3%,去核率≥93.75%,平均破碎率为1.46%。该文设计的链式气动自动化干红枣去核机可实现个体自动定向排布上料、有效去核,同时采用图像检测和机械装置结合技术实现精确定位,降低无效的空冲概率。该研究为进一步完善机械装置的设计,实现机构连续性去核提供了参考。

链传动啮合冲击理论分析及有限元模拟

啮合冲击是引发链传动产生振动、噪声以及链条零部件发生疲劳损坏的主要原因,因此,精确地分析与计算啮合冲击载荷是进行轮齿强度计算以及链传动系统动力学研究的重要内容.为此,建立了链轮轮齿滚子间啮合冲击动力学模型,计算了啮合冲击力幅值;采用赫兹接触理论,对齿面接触应力进行了静态条件下的理论计算;建立了套筒滚子链传动系统有限元模型,采用三维弹性接触问题有限元分析方法,对轮齿滚子间的啮合冲击效应进行了精确模拟,分析了具有标准齿廓形状轮齿滚子瞬时啮合时,冲击载荷变化规律及应力分布情况.计算结果表明:在动态条件下轮齿滚子作为弹性体发生冲击接触时,接触区域变形并非理想的长方形区域;轮齿齿面的冲击接触力分布是不均匀的;在理论接触区域两侧冲击应力较大;在考虑了链轮齿形、间隙及弹性变形等多种影响因素的条件下,动态冲击载荷远大于静态条件下的理论计算值.

套筒滚子链的动力学建模研究

以套筒滚子链为工作执行机构的一类机械系统为研究对象,分析了其动力学影响因素,探讨了该类系统的动力学建模方法。应用有限单元法将链条离散化为若干个链节为基本单元在节点彼此相连的组合体,视每个基本单元为纵向振动的杆单元,通过组集各单元的质量矩阵、刚度矩阵及广义力列阵得到系统质量矩阵、系统刚度矩阵及系统广义力列阵,建立了该系统的动力学方程。在此基础上,应用振型叠加法对动力学方程进行了求解计算,分析了套筒滚子链以修正正弦、修正等速等多种不同运动规律实现间歇运动时链节加速度响应的区别,以及对应同一种运动规律实现间歇运动时链条上不同链节处加速度响应的变化规律。

链传动中纵向振动问题的研究

利用多自由度系统的振动理论研究了链条的纵向振动问题,在对滚子链纵向振动问题建立力学模型的基础上,推导了链条的纵向振动方程式,给出了计算固有频率的公式及主模态的计算方法,并且提出了防止链传动中链条共振的几种措施。

滚子链传动的振动特性分析

链传动是一种重要的机械传动方式,但它受振动的影响很大。本文讨论链传动的振动的主要类型和引起振动的主要原因。

滚子链耐磨性能的研究

磨损是衡量滚子链产品质量的基本指标，新国际标准ＩＳＯ１０８２３—１９９６所规定的短节距滚子链的额定功率曲线是以磨损失效为基础制订的。通过大量试验研究，摸清了国产滚子链耐磨性能的总体水平和基本规律，指出提高滚子链耐磨性能的重要途径。

滚子链链板表面加工质量系数的研究

从滚子链链板孔常用的加工方法入手，研究了表面加工质量对滚子链疲劳强度的影响通过对板孔加工方法不同的系列试样的成组疲劳试验，得到了相应于板孔不同加工方法试样的Ｒ－Ｓ－Ｎ曲线。进而求出了不同预期寿命时表面加工质量系数的分布，并从微观上分析与研究了典型工艺下的疲劳裂纹萌生及扩展速率。

基于虚拟样机技术的步进链传动系统动力学仿真研究

以步进链传动系统为研究对象,分析了该类系统的动力学特性及影响因素,构建了步进链传动系统虚拟样机模型,分析了该类系统采用不同步进运动规律及在不同预紧力状态下动力学特性的变化规律。通过计算机仿真,验证了虚拟样机模型的合理性与正确性,研究结果可为以链传动为执行机构的一类步进传动系统的动力学分析与设计提供借鉴。

滚子链低噪声试验与研究

作者从噪声对人体与环境的危害入手,为降低链传动噪声,设计出了低噪声滚子链条。为研究低噪声滚子链降噪性能,特对同等规格普通滚子链与低噪声滚子链做噪声对比试验,并对试验结果进行了分析与评价。经权威噪声检测机构检测表明:低噪声滚子链较普通滚子链在中高速时降噪8～10dB。

摩托车传动用滚子链磨损特性的研究

道路行驶磨损试验结果表明，摩托车传动用滚子链套筒和销轴零件的主要磨损形式是磨粒磨损，并伴随有疲劳磨损的特征．由微观分析和链条的磨损伸长量可知：套筒和销轴的初始表面硬度较高，有利于改善其磨损表面形貌状态和耐磨性；在磨粒磨损机制下，套筒和销轴零件的表面硬度较低，容易产生“犁切”，表面层的循环硬化现象比较明显，磨损严重；在油池润滑条件下，套筒和销轴零件的表面硬度较高，裂纹的扩展速率较快，循环软化现象也较明显，当表面硬度较低时发生循环硬化．循环软化与循环硬化是导致磨损严重的原因之一．

滚子链传动系统的减振降噪研究

链传动是机械行业中应用非常广泛的一种传动机构,但它产生的振动和噪声具有很大的破坏作用。在分析链传动振动和噪声来源的基础上,提出了链轮齿形的修正方法,分析了采用修形链轮减振和降噪的机理。对由修形链轮组成的滚子链传动系统和标准滚子链传动系统分别进行了多体系统动力学仿真分析。结果表明采用修形链轮有利于减小链传动过程中的啮入冲击和多边形效应,因而能够有效减小链传动过程中的振动和噪声。

国产高速链滚子的失效分析

对国产高速链滚子的早期破坏进行了失效分析。结果表明，在循环载荷作用下，多冲疲劳裂纹首先萌生于冷镦加工在滚子内表面所形成的加工划痕及台阶处，并扩展至断裂。因此，滚子内表面加工质量差是滚子早期失效的主要原因，并提出了改进措施。