Study of the Judder Characteristics of Friction Material for an Automobile Clutch and Test Verification

The friction judder characteristics during clutch engagement have a significant influence on the NVH of a driveline.In this research,the judder characteristics of automobile clutch friction materials and experimental verification are studied.First,considering the stick-slip phenomenon in the clutch engagement process,a detailed 9-degrees-of-freedom(DOF)model including the body,each cylinder of the engine,clutch and friction lining,torsional damper,transmission and other driveline parts is established,and the calculation formula of friction torque in the clutch engagement process is determined.Second,the influence of the friction gradient characteristics on the amplification or attenuation of the automobile friction judder is analyzed,and the corresponding stability analysis and the numerical simulation of different friction gradient values are carried out with MATLAB/Simulink software.Finally,judder bench test equipment and a corresponding damping test program are developed,and the relationship between the friction coefficient gradient characteristics and the system damping is analyzed.After a large number of tests,the evaluation basis of the test is determined.The research results show that the friction lining with negative gradient characteristics of the friction coefficient will have a judder signal.When the friction gradient value is less than-0.005 s/m,the judder signal of the measured clutch cannot be completely attenuated,and the judder phenomenon occurs.When the friction gradient is greater than-0.005 s/m,the judder signal can be significantly suppressed and the system connection tends to be stable.

Design and Performance Study of Clutch Disc Assembly of Wide-Angle, Large-Hysteresis, Multistage Damper

The clutch is an important component of the vehicle driveline system.One of its major functions is to attenuate or eliminate the torsional vibration and noise of the driveline system caused by the engine.Based on experiments of vibration damping under different vehicle conditions,the structure and functional principle of a clutch-driven disc assembly for a wide-angle,large-hysteresis,multistage damper is investigated in this study using an innovative combined approach.Furthermore,a systematic integration of key technologies,including wide-angle low-stiffness damping technology,large-hysteresis clutch technology,a novel split pre-damping structure technology,damping structure technology for component cushioning,and multistage damping structure technology,is proposed.The results show that the total torsional angle of the wide-angle large-hysteresis,multistage damper is more than twice that of the traditional clutch damper.The multistage damping design allows a better consideration of various damping requirements under different vehicle conditions,which can effectively address problems of severe idle vibrations and torsional resonance that occur under idled and accelerated conditions.Meanwhile,the use of a large-hysteresis structure and wear-resistant materials not only improves the vibration damping performance,but also prolongs the product service life,consequently resulting in multi-faceted optimization and innovative products.

纳米氧化铝改性酚醛树脂增强纸基摩擦材料的热学与力学性能

以纳米氧化铝改性的酚醛树脂作为黏结剂和增强剂,采用造纸工艺制备纸基复合摩擦材料,研究改性树脂含量(质量分数)和固化温度对材料耐热性能、剪切强度和压缩回弹性能的影响。结果表明,随酚醛树脂含量增加,材料的耐热性能略有降低,剪切强度增大;在第1~4次压缩回弹实验中,第1次的回弹率随树脂含量增加而明显增大,而第2~4次的回弹率很接近,并受树脂含量影响较小;材料的压缩率随树脂含量增加而降低,第1次的压缩率明显高于后面3次的压缩率。在较高固化温度下制备的纸基复合材料具有高耐热性能和剪切强度,随固化温度升高,第1次的压缩率明显降低而回弹率明显升高,第2~4次的回弹率和压缩率接近,且受固化温度的影响较小。当改性酚醛树脂的质量分数为40%,固化温度为160℃时,所得纸基摩擦材料的耐热性能较好,剪切强度较高,并具有较高的压缩率和回弹率。

六钛酸钾晶须增强汽车干式离合器摩擦片的热衰退和振颤特性

汽车离合器用摩擦片是影响离合器使用寿命、动力传递效率和舒适性的关键零件,提高其在滑磨过程中摩擦因数稳定性和对振颤的衰减特性是避免传递扭矩不稳定,汽车发生振颤的重要技术手段。本文制备一种六钛酸钾晶须增强离合器摩擦片,研究该类材料的热衰退特性,并进行振颤台架试验。结果表明:添加8%(质量分数)六钛酸钾晶须的汽车离合器摩擦片在400℃时摩擦因数大于等于0.2,优于德国大众3101程序热衰退测试标准350℃的要求;其在20000个循环后在500 r/min和800 r/min的平均阻尼因数小于等于0.05 N∙m∙s,满足德国3102程序振颤测试规定标准;在20000个循环后在500 r/min的最大阻尼因数小于等于0.1 N∙m∙s规定标准,对振颤有明显衰减作用。

矿用卡车离合器用锌钨合金增强铜基粉末冶金摩擦材料的摩擦磨损性能

在现有铜基粉末冶金摩擦材料配方中加入Zn-W合金,设计不同锌钨合金含量w(Zn-W)以及不同压制密度,制备矿用卡车离合器用铜基摩擦材料,分析和测试材料的组织与摩擦磨损性能,并进行能量/功率等级递增试验和台架试验。结果表明:铜基摩擦材料的表面硬度随w(Zn-W)增加而下降,随致密度增加而升高;摩擦因数随w(Zn-W)增加而增大,随致密度增加而减小。w(Zn-W)为6%、且致密度比现有配方的铜基摩擦片致密度提高10%的铜基摩擦片具有合适的表面硬度和动/静摩擦因数以及较好的耐磨性能,并能降低汽车的噪声、振动及声振粗糙度,比不添加锌钨合金的铜基摩擦片的能量输出提高2级,可承受第6级能量输出(753.16 J/cm^2),主要性能略高于国外进口铜基摩擦片。

碳纳米管对汽车刹车片用陶瓷摩擦材料性能的影响

设计研发安全环保和高性能的汽车刹车用摩擦材料是当前的研究重点。本文以碳纳米管作为增强剂制备了汽车刹车片用陶瓷摩擦材料,分析了碳纳米管含量对摩擦材料的微观结构、力学性能和摩擦磨损性能的影响,利用扫描电子显微镜对摩擦材料的磨损前后微观形貌进行了观察。研究结果表明:碳纳米管能够显著增强材料间的黏合作用,随着含量增加(15%以内),摩擦材料的抗压和抗剪切强度提高;材料摩擦因子和磨损率小且稳定,热稳定性好,350℃下无明显热衰退,但是当碳纳米管含量继续增加(>15%),材料的综合性能会衰减。

硫氮共渗齿轮的干摩擦特性试验研究

为进一步提高碳钢制齿轮的摩擦学性能,采用硫氮共渗处理技术对常用45钢齿轮进行处理,研究它在干摩擦条件下的摩擦磨损性能。在室温下,不使用任何液体润滑剂进行齿轮的磨损试验,并对相同参数的45碳钢齿轮进行氮化、渗碳淬火、高频淬火和硫氮共渗+氮化的复合等不同表面处理。采用齿轮检测仪测量6种齿轮试验后轴间距离,并将其变化作为磨损量。采用摩擦磨损试验机测量各种表面处理的摩擦因数,并观察试验4 h后的6种齿轮的齿面状态。结果表明:相比其他表面处理技术,经硫氮共渗处理的齿轮磨损量明显较小,而表面硬度与其他处理相当或较低;硫氮共渗+氮化复合表面处理的磨损量最低;硫氮共渗形成的硫化物层厚度约为1μm,远低于试验4 h后的磨损量,但是硫化物层磨损后润滑作用仍然存在。因此,硫氮共渗+氮化复合表面处理可有效改善碳钢齿轮在常温空气中的固体润滑性能。

某车型弧形弹簧双质量飞轮的设计

双质量飞轮与普通飞轮的不同点在于双质量飞轮采用初级飞轮与次级飞轮共同储能的结构,初级飞轮与连接法兰盘之间的弧形腔内装有弧形弹簧,起到减震器的作用。结合双质量飞轮的工作原理专门设计适用于某车型的双质量飞轮结构及扭转特性。为优化扭转特性,设计了双质量飞轮的内、外弧形弹簧,并利用CATIA建立了其3D模型。最后对设计的内、外弧形弹簧传扭能力及双质量飞轮工作时的温升进行了校核,结构能满足设计要求。