Head-cutter for optimal tooth modifications in spiral bevel gears

A method for the determination of optimal tooth modifications in spiral bevel gears based on improved load distribution and reduced maximum tooth contact pressure and transmission errors is presented. The modifications are introduced into the pinion tooth-surface by using a head-cutter with bicircular profile and with optimal diameter. In the optimization of tool parameters the influence of relative position errors of the mating gears is included.By using the computer program developed for load distribution calculation, the influence of head-cutter parameters and relative position errors of the mating gears on tooth contact and transmission errors is investigated. Based on the results obtained, the radii and the position of the circular tool profile arcs and the cutter diameter for pinion teeth finishing were optimized. By applying the optimal tool parameters, the maximum tooth contact pressure is reduced by 45% and the maximum angular position error of the driven gear by 60%, in regard to the spiral bevel gear pair with a pinion manufactured by a cutter of straight-sided profile and of diameter determined by the commonly used methods.     

Modelling, Implementation, and Manufacturing of Spiral Bevel Gears with Crown

The operational performance of gears in terms of smoothness, quietness, wear and life span is largely affected by how gear and pinion teeth make contact. To enhance the operational performance, a crown is often applied to a standard (nominal) gear tooth surface. Regardless of the presence of a crown, all the gears are machined by special types of machine tools, such as gear hobbers and shapers. This paper develops a tooth surface for a spiral bevel gear with a crown so that it can be machined by numerically controlled machine tools. Specifically, we derived: 1. A bi-parametric tooth surface model for a standard spiral bevel gear. 2. A crown model along the spiral curve direction. 3. A crown model along the involute curve direction. The developed algorithm was tested and implemented in a prototype software system called GearCAM. With the GearCAM system, a set of spiral bevel gear and pinion was machined using a 4-axis CNC milling machine to check the validity and effectiveness of the crowning method. Through various verifications, it is shown that the models developed for the standard and crown gears can be used as a means for design and verification of spiral bevel gears.     

Pinion tooth surface generation strategy of spiral bevel gears

Aviation spiral bevel gears are often generated by spiral generated modified(SGM) roll method.In this style,pinion tooth surface modified generation strategy has an important influence on the meshing and contact performances.For the optimal contact pattern and transmission error function,local synthesis is applied to obtain the machine-tool settings of pinion.For digitized machine,four tooth surface generation styles of pinion are proposed.For every style,tooth contact analysis(TCA) is applied to obtain contact pattern and transmission error function.For the difference between TCA transmission error function and design objective curve,the degree of symmetry and agreement are defined and the corresponding sub-objective functions are established.Linear weighted combination method is applied to get an equivalent objective function to evaluate the shape of transmission error function.The computer programs for the process above are developed to analyze the meshing performances of the four pinion tooth surface generation styles for a pair of aviation spiral bevel gears with 38/43 teeth numbers.The four analytical results are compared with each other and show that the incomplete modified roll is optimal for this gear pair.This study is an expansion to generation strategy of spiral bevel gears,and offers new alternatives to computer numerical control(CNC) manufacture of spiral bevel gears.     

弧齿锥齿轮双重螺旋法切齿原理及齿面接触分析研究

弧齿锥齿轮双重螺旋法具有高效、可实现干切削的特点,是Gleason制弧齿锥齿轮的先进加工方法。为揭示双重螺旋法的切齿原理,以大轮成形法加工的弧齿锥齿轮双重螺旋法为研究对象,以啮合原理和微分几何学为基础,根据刀盘、机床、工件之间的运动位置关系,利用矢量法、基于齿面3个参考点建立切齿数学模型,推导机床调整参数的计算过程;然后,以齿槽中点作为参考点,修正弧齿锥齿轮副的齿坯几何参数;另外,以小轮产形面方程代替其共轭齿面方程,提出新的齿面失配设计新方法,与传统方法相比简化计算过程。以一对7×43的准双曲面齿轮副为例进行设计计算和切齿加工,齿面接触分析与滚动检查结果验证所提出的双重螺旋法切齿原理的正确性,并根据该切齿原理开发弧齿锥齿轮双重螺旋法的设计软件,为该方法在国内的推广提供理论基础与技术支撑。     

有误差的螺旋锥齿轮传动接触分析

以多体系统误差建模理论和齿轮啮合原理为基础,提出含有机床运动几何误差以及齿轮副安装误差的螺旋锥齿轮齿面接触分析(Error tooth contact analysis, ETCA)方法。以SGM法(大轮展成法加工,小轮变形法加工)加工的弧齿锥齿轮为例,通过ETCA分析,得到机床运动误差和安装误差对螺旋锥齿轮齿面加工质量影响的定量关系,对ETCA和TCA的结果进行对比分析,结果表明机床运动误差和安装误差对螺旋锥齿轮的齿面接触质量有较大的影响,为了通过齿面接触分析达到更准确的反调加工参数的目的,采用ETCA的分析结果指导加工参数反调更为合理。     

弧齿锥齿轮小轮锥度切削原理及其仿真

介绍了弧齿锥齿轮锥度切削的加工方法和切齿原理;根据局部综合法建立了小轮实现锥度切削的加工条件;利用TCA分析对锥度切削齿面啮合质量进行了仿真;利用三维软件Pro/E,绘制出了小轮锥度切削的三维轮齿模型;证明了在数控铣齿机上实现锥度切削的可行性。     

Reverse engineering of machine-tool settings with modified roll for spiral bevel pinions

Although a great deal of research has been dedicated to the synthesis of spiral bevel gears, little related to reverse engineering can be found. An approach is proposed to reverse the machine-tool settings of the pinion of a spiral bevel gear drive on the basis of the blank and tooth surface data obtained by a coordinate measuring machine(CMM). Real tooth contact analysis(RTCA) is performed to preliminary ascertain the contact pattern, the motion curve, as well as the position of the mean contact point. And then the tangent to the contact path and the motion curve are interpolated in the sense of the least square method to extract the initial values of the bias angle and the higher order coefficients(HOC) in modified roll motion. A trial tooth surface is generated by machine-tool settings derived from the local synthesis relating to the initial meshing performances and modified roll motion. An optimization objective is formed which equals the tooth surface deviation between the real tooth surface and the trial tooth surface. The design variables are the parameters describing the meshing performances at the mean contact point in addition to the HOC. When the objective is optimized within an arbitrarily given convergence tolerance, the machine-tool settings together with the HOC are obtained. The proposed approach is verified by a spiral bevel pinion used in the accessory gear box of an aviation engine. The trial tooth surfaces approach to the real tooth surface on the whole in the example. The results show that the convergent tooth surface deviation for the concave side on the average is less than 0.5 μm, and is less than 1.3 μm for the convex side. The biggest tooth surface deviation is 6.7 μm which is located at the corner of the grid on the convex side. Those nodes with relative bigger tooth surface deviations are all located at the boundary of the grid. An approach is proposed to figure out the machine-tool settings of a spiral bevel pinion by way of reverse engineering without having known the theoretical     

对数螺旋锥齿轮齿面接触区的相关特性

介绍了对数螺旋锥齿轮轮齿接触检测的方法。在Y9550型锥齿轮滚动检查机上进行了对数螺旋锥齿轮样件齿面接触区的检测实验,通过实验获得了对数螺旋锥齿轮接触区的位置、形态和大小等结果,并将实验结果与格里森螺旋锥齿轮接触区进行了对比,得出了对数螺旋锥齿轮齿面接触区的相关特性。     

螺旋锥齿轮点接触齿面生成法

提出一种能直接生成点接触,满足啮合配对要求的齿面方法,该方法利用齿面接触分析设计齿面,为齿轮ＮＣ加工运动计算提供新的途径。     

螺旋锥齿轮大轮齿形误差的在机测量

为了在国产数控螺旋锥齿轮磨齿机上实现大轮齿形误差的在机测量,对大轮齿形误差的在机测量方法进行了研究。基于齿轮坐标系与机床坐标系之间的关系,建立了将齿面离散点坐标及法矢从齿轮坐标系转换到机床坐标系的方法。根据大轮的齿面几何特征,建立了大轮齿形误差的在机测量方法以及测量流程。根据在机测量得到的测球球心空间坐标,运用曲面拟合技术和最优化算法,计算了实际齿面相对于理论齿面沿各离散点法矢方向的齿形误差值。通过对比在机测量和齿轮测量中心的齿形误差测量结果,验证了螺旋锥齿轮大轮齿形误差在机测量方法的正确性。     

基于实际切齿方法的弧齿锥齿轮三维造型

发展了格利森制弧齿锥齿轮实际切制过程的模拟方法,利用展成法的原理得到实际加工弧齿锥齿轮齿面上的点,利用曲面重建的方法由点得到三维弧齿齿面,最后建立了格利森制弧齿锥齿轮的三维实体模型。由于弧齿锥齿轮的三维实体模型,基于实际的加工方法,可以模仿弧齿锥齿轮机床加工时的调整,灵活的进行三维弧齿齿面调整,以实现弧齿锥齿轮的虚拟试切,降低成本,提高效率,同时使齿面啮合接触区更加合理。     

The meshing angular velocity and tangential contact force simulation for logarithmic spiral bevel gear based on Hertz elastic contact theory

To obtain the change tendency of output angular velocity and tangential contact force of a gear when the pinion under the step input during meshing of a new type of spiral bevel gear, which is a logarithmic spiral bevel gear, the tooth flank equation of logarithmic spiral bevel gear is deduced based on the formation mechanism of the tooth flank formation. A three-dimensional model of a pair of logarithmic spiral bevel gears whose number of teeth was 37:9, with modules being 4.5 mm, normal pressure angle being 20 degrees and spiral angle being 35 degrees were built and assembled. Based on Hertz elastic contact theory, the calculation formulas and parameters sets of contact force for conventional spiral bevel gear meshing simulation and logarithmic spiral bevel gear meshing simulation were done. Consider the dynamic simulation about meshing angular velocity and tangential contact force for conventional spiral bevel gear meshing and logarithmic spiral bevel gear meshing, respectively. Finally, by analyzing and comparing the simulation data, the results show that under the same input conditions, the fluctuation of the gear angular velocity and tangential contact force of logarithmic spiral bevel gear meshing are smaller than the conventional spiral bevel gear. That is, the transmission stationary of logarithmic spiral bevel gear meshing is superior to conventional spiral bevel gear.     

弧齿锥齿轮的齿面主动设计及试验验证

齿面印痕和传动误差对齿轮传动的性能起着决定作用,根据齿面印痕的位置、方向及传动误差幅值的要求,在齿面上设计三个啮合点,通过对这三个啮合点的控制,达到对齿面啮合质量的全程控制。在此基础上,为了满足不同的加工要求,又提出按照给定的垂直轮位的值对齿面进行再设计,保证传动误差的幅值不变且接触迹线仅有较小的改变,为弧齿锥齿轮副设计提供了新的方法和途径。最后在磨齿机上加工了一对齿轮,通过印痕检测验证了本文设计方法的正确性。     

Manufacture of face-hobbed straight bevel gears using a six-axis CNC bevel gear cutting machine

Face hobbing is a continuous indexing and double-flank cutting process whose high productivity and precision has made it one of the leading methods for fabricating spiral bevel and hypoid gears. The current method is inappropriate, however, for cutting straight bevel gears (SBGs) because it generates extended epicycloidal flanks. Nonetheless, a mathematical model of a face-hobbed SBG was successfully established in earlier research that enables straight cutting paths to cut straight tooth spaces based on a hypocycloidal straight-line mechanism in which the rolling circle radius equals half the base circle radius. This mathematical model, however, is based on a virtual universal cradle-type bevel gear cutting machine that has not yet been developed. This paper therefore proposes another mathematical model of face-hobbed SBG based on a modern six-axis computer numerical control (CNC) bevel gear cutting machine. The six-axis nonlinear machine settings are derived through conversion from the cradle-type machine settings. Meanwhile, the usage of electric gearbox (EGB) for bevel gear cutting is not revealed because of commercial consideration. Therefore, we also provide a solution to use EGB of Fanuc 16i CNC controller. A cutting experiment validates the proposed mathematical models using our developed six-axis CNC bevel gear cutting machine to cut the face-hobbed SBGs. Finally, a flank topographic correction is made that, according to postcorrection simulated topographic errors, can effectively reduce manufacturing errors. This paper successfully implements a face-hobbing process for manufacturing SBGs on a modern six-axis CNC bevel gear cutting machine.     

螺旋锥齿轮基于离散点描述齿面接触分析研究

详细讨论了用 B样条函数拟合表示的螺旋锥齿轮轮齿齿面接触分析方法 :1建立了螺旋锥齿轮拟合齿面的接触点求解模型 ,并给出了该模型的求解方法 ;2给出了拟合齿面接触区及传动误差曲线的绘制方法 ,最后给出了一个实例。该方法经适当变化后也可用于其它种类齿轮的齿面接触分析。     

机床调整参数误差对螺旋锥齿轮齿面形状误差影响的研究

通过齿面点离散的方法,评判机床调整参数误差对螺旋锥齿轮齿面误差的影响程度,进一步分析齿面形状变化趋势,指出了由于齿面误差引起啮合区位置偏移,从而导致的不良啮合状态,为机床误差补偿及提高螺旋锥齿轮的制造精度提供了依据.     

弧齿锥齿轮成形法数控加工仿真建模与实现技术

针对半滚切法加工的弧齿锥齿轮,根据机床、刀具和被加工工件之间的位置关系和切齿过程,由齿轮啮合原理和弧齿锥齿轮切齿原理推导出弧齿锥齿轮齿廓曲面方程。根据实际的弧齿锥齿轮参数,基于CAT IA曲面建模方法,运用上述数学方程,建立了锥齿轮三维实体模型,验证了该方法的有效性。     

螺旋锥齿轮齿面扫描式测量法及其应用研究

螺旋锥齿轮的实际齿面形状是影响其动力学性能的一个非常重要的因素。本文介绍了采用虚拟共轭基准面的螺旋锥齿轮齿面的扫描式测量、数据处理及应用方法，即大齿轮的基准面采用的是由机床设定参数计算出的理论齿面，而小齿轮的基准面采用的是与大齿轮共轭的假想小齿轮齿面。由于采用了二维测头进行齿面测量，有效地避免了测头与齿面间摩擦力的影响，既能保持高精度，又能进行快速测量。同时，该种测量采用连续扫描的方法，信息量大、速度快，适合于大批量生产中的螺旋锥齿轮的齿面质量管理与控制。由于扫描式测量采用了虚拟共轭基准齿面，所以从测量数据本身就可以判断齿面的接触斑点位置与形状，因而可以直观、有效地对齿面质量进行管理与控制。     

数控端铣弧齿锥齿轮的刀背与轮齿干涉避免方法

在五轴数控机床上端铣加工弧齿锥齿轮时,为了避免中凹盘铣刀背锥面与对侧齿面发生干涉,提出了基于刀具和齿轮结构的干涉避免方法。通过确定加工轨迹上刀背圆锥面最突出母线与对侧齿面的位置关系,保证刀具背锥面沿进给方向的法曲率小于对侧齿面法曲率,优化确定刀具边缘厚度和背锥角,实现了端铣齿面时刀背不干涉对侧齿面。最后,以一对弧齿锥齿轮副的小轮为例,通过比较虚拟加工模型和理论模型,验证了所提干涉避免方法的有效性。     

Face-milling spiral bevel gear tooth surfaces by application of 5-axis CNC machine tool

In order to solve some common problems of CNC-machined spiral bevel gears such as small cutting strip width and poor surface quality, while milled by the ball-end, a machining method of face milling using a disk cutter with a concave end is presented. The research theories are based on the foundation of spiral bevel gears’ geometry structure. Firstly, a bigger diameter disk cutter with a concave end is selected. Then, change the setting order of cutter orientation angles. The functions of cutter tilt and yaw angle are separated, and tooth surfaces machined with big cutting strip width and no bottom land gouge can be expected. Since the cutter yaw angle, determined firstly by cutting contact point, positions in the tooth surface machine, the bottom land gouge interference can be avoided effectively. Then, the tilt angles of the gear pair, both side tooth surfaces, are determined by the theory of sculptured surfaces machined by the flat-end cutter, respectively. As a result, the improved cutting strip width and machining efficiency can be realized. Finally, feasibility of this method is verified through machining experiment and measurement of a spiral bevel gear pair.