基于齿顶厚约束条件下的直齿圆柱齿轮变位系数研究

依据齿轮传动原理和泰勒级数展开式,导出了齿顶圆直径与齿顶圆压力角、啮合角、变位系数的近似计算公式,并将得到的近似值代入齿顶圆直径、齿顶圆弧齿厚、变位系数之间的关系表达式,用C语言编程实现齿项圆直径、变位系数极限精确值的快速计算,为变位系数的数字化实现提供了算法。     

奇数齿直齿圆柱齿轮齿顶圆直径的测量和计算

一、前言 在机械维修工作中,经常遇到奇数齿直齿圆柱齿轮齿顶圆直径的测量问题。在测量时,因为量具直接测量到的尺寸不是齿顶圆直径d_a,而是一个齿的齿顶到对面齿间齿顶圆弦的距离H(图1)。通常齿顶圆直径d_a按下式计算: d_a=KH (1) 系数K值可从有关资料中查得。 用这种方法计算齿顶圆直径,当齿数较少时,误差较大,不能满足工作要求,而对于变位齿轮、短齿齿轮、     

渐开线斜齿圆柱齿轮齿形参数的测量与计算

渐开线斜齿圆柱齿轮齿形复杂，齿形几何参数多，各主要参数计算公式中相互交叉使用，没有固定的测绘模式。从测量齿顶圆直径和齿根圆直径着手，根据公法线长度的测量原则测出公法线长度，初步求出法面模数，并判定齿顶高系数和径向间隙系数；利用滚印法及滚齿机测得分度圆螺旋角。并求得变位系数；最后验证跨测齿数及法面模数。     

关于变位齿轮变位系数优化设计

在进行变位齿轮设计的过程中,合理选择变位系数是设计变位齿轮的关健环节。本文论述了利用电子计算机对直齿外接圆柱齿轮的变位系数进行优化设计,以及计算最佳变位系数状态下的中心距、重合度系数、齿顶圆直径、基圆直径和公法线长度的方法。一、齿轮变位方式     

滚切渐开线直齿锥齿轮

在进口汽车的配件加工中,常会遇到渐开线直齿锥形齿轮。这种齿轮的加工方法,一般在普通滚齿机上,增加一套保证滚刀轴向、径向进给联动装置的附加锥度挂轮机构,就可以对工件进行滚切加工。 1.渐开线直齿锥形齿轮的特征渐开线直齿锥形齿轮是带有锥度的连续变位渐开线:赶齿轮。滚切后的这种齿轮具有以下主要特征。 (1)齿轮齿廓面与端面不垂直、呈倾斜,有大端面、小端面之分。 (2)在齿轮垂直于齿轮轴线各截面上的全齿高都相等,齿轮模数、分度圆直径和分度圆压力角也都相等。 (3)齿轮各截面上的变位系数都不相等,齿顶圆直径、齿根圆直径、齿顶高、齿根高和分度圆齿厚也     

短齿变位渐开线内齿轮的加工

在一般的工厂中,常常会遇到短齿变位直齿内齿轮的加工问题。由于工厂一般不可能存有非标准短齿插齿刀,而到工具厂联系非标准刀具定货,一是不经济,二是时间长。如果用标准插齿刀来加工短齿内齿轮,就会出现齿根圆能满足尺寸,但分度圆齿槽宽减小;或分度圆齿槽宽满足尺寸,但齿根圆直径过大、切得过深的现象。为了使加工短齿变位内齿轮时,既能满足分度圆齿槽宽度尺寸要求,又不超过规定的齿根圆直径,我们采用把标准插齿刀的顶圆直径沿顶后刀面磨小的方法,满足了加工短齿变位内齿轮的要求。经实     

3K-Ⅱ行星传动机构四个关键参数的确定方法

配齿以及中心距、变位系数和齿顶圆直径的确定是3K-Ⅱ(NGWN-Ⅱ)行星传动机构设计的关键技术,针对3K-Ⅱ行星传动机构的特点,提出根据传动比确定各齿轮齿数以及如何合理的确定中心距、各齿轮变位系数和齿顶圆直径的方法,并根据齿轮传动质量的关键指标对比分析,验证此方法的合理性,有一定的实际应用价值。     

标准插齿刀改制短齿内齿插齿刀

加工齿厚和齿根圆直径均有较高精度要求的短齿内齿轮时,一种是用标准插齿刀先切削至齿根圆直径,然后通过分齿移位法加工至齿厚尺寸;另一种是设计专用插齿刀加工,同时保证齿厚和齿根圆直径公差。前者适用于单件生产。如果批量生产,要求有专用插齿刀加工。从工具厂制造的通用短齿插齿刀很难满足这种内齿轮的加工精度要求,因而需要专门设计制造。一般中、小工厂难于加工。为此,作者将标准插齿刀的外径磨小,改成专用插齿刀。 1.测量标准插齿刀的实际变位系数。测量时用公法线千分尺测出插齿刀的公法线长度W′,然后用下列公式计算其变位系数:     

细长齿斜齿轮的测绘与计算

通过测量细长齿斜齿轮的螺旋角及公法线长度等计算出准确的变位系数,再根据测量所得齿顶无直径及齿根园直径计算出齿顶高系数ha^*和径向间隙系数C^*,这种测量计算方式它使所取参数与被测齿轮的实际参数能完全吻合。     

直齿圆锥齿轮的测绘

直齿圆锥齿轮的测绘比圆柱齿轮困难,但它的各部尺寸也是以模数、压力角、齿顶高系数、顶隙系数为计算的依据,这些参数的测绘也都在大端背锥上进行。实际测绘一个圆锥齿轮,要经过观察、分析、测量和计算四个步骤,一般来讲,比较可靠的数据有齿数、轴突角、根锥角、齿根圆直径。不易测量准确的数据有压力角、齿顶圆直径、顶锥角、齿高、齿厚等(齿高和齿顶圆直径要考虑倒棱的大小及其影响)。     

Performance prediction and flow field calculation for airfoil fan with impeller inlet clearance

The performance prediction of an airfoil fan using a commerical code, STAR/CD, is verified by comparing the calculated results with measured performance data and velocity fields of an airfoil fan. The effects of inlet tip clearance on performance are investigated. The calculations overestimate the pressure rise performance by about 10–25 percent. However, the performance reduction due to tip clearance is well predicted by numerical simulations. Main source of performance decrease is not only the slip factor but also impeller efficiency. The reduction in performance is 12–16 percent for 1 percent gap of the diameter. The calculated reductions in impeller efficiency and slip factor are also linearly proportional to the gap size. The span-wise distributions of phase averaged velocity and pressure at the impeller exit are strongly influenced by the radial gap size. The radial component of velocity and the flow angle increase over the passage as the gap increases. The slip factor decreases and the loss increases with the gap size. The high velocity of leakage jet affects the impeller inlet and passage flows. With a larger clearance, the main stream moves to the impeller hub side and high loss region extends from the shroud to the hub.     

转基因超微量注射控制器的研制及其特性分析

注射法是当今构建转基因动物模型的主要方法。注射量是关系到细胞的外源基因容受量及至细胞成活率的重要因素。目前，生物工程界普遍应用的手工注射控制器不能精确控制注射量，注射效率和成活率低下。介绍了一种气压电控式超微量注射控制器的原理与设计。在理论模型推导的基础上，应用多元变换回归设计对出流量与注射时间、注射压力和端内径间的关系进行了正交试验与分析。     

Highly controllable fabrication of fiber probe for photon scanning tunneling microscope

A selective chemical etching was used to fabricate fiber probes for the photon scanning tunneling microscope (PSTM). The cladding diameter of the fiber probe was controlled by varying the first-step etching time. The cone angle of the fiber probe tip was controlled by varying the doping ratio of the fiber and the composition of the etching solution. A cladding diameter of 8 μm and a tip diameter of about 3 nm were fabricated. The smallest cone angle was 14°.     

Highly controllable fabrication of fiber probe for photon scanning tunneling microscope

A selective chemical etching was used to fabricate fiber probes for the photon scanning tunneling microscope (PSTM). The cladding diameter of the fiber probe was controlled by varying the first-step etching time. The cone angle of the fiber probe tip was controlled by varying the doping ratio of the fiber and the composition of the etching solution. A cladding diameter of 8 μm and a tip diameter of about 3 nm were fabricated. The smallest cone angle was 14°.     

The effect of injection pressure and fuel viscosity on the spray characteristics of biodiesel blends injected into an atmospheric chamber

An experimental study was conducted to examine the effect of injection pressure and fuel type on the spray tip penetration length and the angle of spray injected into atmospheric chamber. The objective of the present study is to formulate empirical correlations of the spray tip penetration and the spray angle for non-evaporative condition. The experiment was performed by a common rail type high-pressure injector for the diesel engine at the injection pressure 40??100 MPa and four different fuels (D100, BD25, BD45, and BD65). The results showed that the biodiesel content increased the spray tip penetration and decreased the spray angle. The correlation of spray tip penetration is expressed for each region before and after spray break-up time in terms of injection pressure, fuel viscosity and time after start of injection. The correlation is also obtained for spray angle equation terms of injection pressure and fuel viscosity.     

Electric near-field enhancing properties of a finite-size metal conical nano-tip

Finite-difference time-domain (FDTD) technique simulations are performed to study the near-field resonance properties of a silver conical nano-tip with a rounded end. Varying the tip geometry, we have computed the electric field distribution, as well as the electric field enhancement factor in the immediate vicinity of the tip apex. The aim of this study is to find optimal geometric parameters of the conical tip, such as its angle and length, in order to maximize the electric field enhancement factor. The increase of the tip length is shown to result in a redshift of the tip resonance wavelength. In addition, some subsidiary (non-dipole) peaks appear for relatively long tips. The peak enhancement values for the small-angle tips increase with the tip length while those for the large-angle ones decrease with it. At the same time, the dependencies of the field enhancement on the cone angle exhibit non-monotonic behavior. In other words, an optimal angle exists allowing one to maximize the electric near field. Finally, the effect of the supporting dielectric medium on the electric field near the tip apex is discussed. In the approximation used, the effect is shown to leave the main conclusions unchanged.     

离心压气机改型设计及扩压器前掠分析

本文主要研究单级离心压气机的改型设计,并采用数值方法对楔形扩压器前掠展开了详细研究。在保持原有压气机叶轮外径不增加、流量和设计转速不变的条件下,将压比由4.0提高到4.5。在设计离心叶轮时,首先需要确定叶轮后弯角,为了真实评估叶轮后弯角对离心压气机效率和稳定性的影响,详细设计了后弯角为20°,25°,30°和35°的三维叶轮以及相匹配的楔形扩压器,最终选择35°后弯角叶轮。其次,后弯角为35°叶轮的设计点压比相对于设计目标偏低,将hub处弯角减小到30°达到增加设计点压比。最后,考虑到楔形扩压器各截面载荷的不同,研究了楔形扩压器前掠对性能影响。     

单一斜齿圆柱齿轮精确测量的简便方法

从制造的角度出发,阐述了精确测量单一斜齿圆柱齿轮齿形参数的简便方法,测量公法线长度计算基圆齿距从而查表确定模数和压力角,测齿顶圆直径估算分度圆螺旋角,用滚齿机修正分度圆螺旋角,并以实例说明测算的步骤,结果表明,该法避开了与加工无关的参数的反复测算,且测绘的精度能满足使用的要求。     

精确测绘单一斜齿圆柱齿轮

介绍了精确测绘单一斜齿圆柱齿轮齿形参数的简便方法,即测量公法线长度计算基圆齿距从而查表确定模数和压力角;测量齿顶圆直径估算分度圆螺旋角,用分度头在铣床上修正分度圆螺旋角,并进行误差分析。该方法避免了与加工无关参数的反复测算,测绘的精度能满足修配使用的要求。     

Influence of Tip Relief Modification on the Wear of Spur Gears with Asymmetric Teeth

Recently, spur gears with asymmetric teeth have been considered a way of increasing performance while maintaining the gearbox dimensions. Asymmetric teeth have different pressure angles on drive and coast sides. They provide, among other advantages, a high bending strength and low vibration. In spur gears with asymmetric teeth, wear has been observed to be a major failure mode. In this study, the impact of tip relief modification and pressure angle on the wear of spur gears with asymmetric teeth is numerically investigated. Here, the focus is on sliding wear. A wear model based on Archard's equation is employed to predict wear depth. The pressure angle and the tip relief are parameterized. In the analysis, instantaneous contact loads and Hertz pressures are used in wear depth calculations. It is shown that as the amount of the tip relief increases, the wear depth, particularly at the beginning and end of the mesh, decreases. As the number of wear cycles increases, the effect of the tip relief modification on wear depths decreases slightly. It was also shown that with an increase in tip relief, the dynamic load decreases. However, if the amount of tip relief modification increases excessively, the maximum dynamic load also increases. Therefore, an excessive increase in tip relief modification should be avoided, whereby the level of excessive increase depends on the tip relief configuration.