A nonlinear model of anti-backlash gear with time-varying friction and mesh stiffness was proposed for the further study on dynamic characteristics of anti-backlash gear. In order to improve the model precision, appli...A nonlinear model of anti-backlash gear with time-varying friction and mesh stiffness was proposed for the further study on dynamic characteristics of anti-backlash gear. In order to improve the model precision, applied force analysis was completed in detail, and single or double tooth meshing states of two gear pairs at any timing were determined according to the meshing characteristic of anti-backlash gear. The influences of friction and variations of damping ratio on dynamic transmission error were analyzed finally by numerical calculation and the results show that anti-backlash gear can increase the composite mesh stiffness comparing with the mesh stiffness of the normal gear pair. At the pitch points where the frictions change their signs, additional impulsive effects are observed. The width of impulsive in the same value of center frequency is wider than that without friction, and the amplitude is lower. When gear pairs mesh in and out, damping can reduce the vibration and impact.展开更多
柴油机噪声影响着农业机械操作者的身心健康,该文为了解决某型柴油机在怠速工况下的异响噪声问题,采用仿真与试验相结合的方法进行研究。首先,通过声强和声压测试确定了噪声的主要产生部位;然后,基于Hypermesh和Abaqus软件建立了曲轴及...柴油机噪声影响着农业机械操作者的身心健康,该文为了解决某型柴油机在怠速工况下的异响噪声问题,采用仿真与试验相结合的方法进行研究。首先,通过声强和声压测试确定了噪声的主要产生部位;然后,基于Hypermesh和Abaqus软件建立了曲轴及整机零部件的有限元模型,并通过模态试验验证了有限元模型的准确性,基于Excite软件建立了配气正时传动系统和整机的多体动力学模型,发动机整机振动计算时考虑了缸内燃气压力、正时系统及配气机构全阀系激励和活塞敲击激励。多体动力学仿真结果表明:齿轮的反向敲击出现时,齿轮工作面的接触力消失,进排气齿轮在背隙侧发生接触产生冲击力,进而造成发动机在怠速时产生"哒哒"的异响噪声;整机振动仿真结果表明:使用消隙齿轮可以消除进/排气凸轮轴齿轮的反向敲击,在1 000~2 500 Hz范围内,使得齿轮室盖和缸盖罩的振动速度级降低了7 d B左右。最后在半消声室的发动机台架上,对有无消隙齿轮的柴油机进行了振动加速度、噪声和声品质的对比试验,试验表明:怠速工况下,使用消隙齿轮后,前端发出的"哒哒"异响噪声消失,齿轮室盖振动降幅很大,前端1 m噪声声压级降低了5~9 d B(A),声品质也有了明显改善。因此,当内燃机其它齿轮传动部位出现齿轮反向敲击声时,可考虑使用消隙齿轮予以解决。展开更多
A novel specific type of worm drive, so-called end face engagement worm gear(EFEWD), is originally presented to minimize or overcome the gear backlash. Different factors, including the three different types, contact...A novel specific type of worm drive, so-called end face engagement worm gear(EFEWD), is originally presented to minimize or overcome the gear backlash. Different factors, including the three different types, contact curves, tooth profile, lubrication angle and the induced normal curvature are taken into account to investigate the meshing characteristics and create the profile of a novel specific type of worm drive through mathematical models and theoretical analysis. The tooth of the worm wheel is very specific with the sine-shaped tooth which is located at the alveolus of the worm and the tooth profile of a worm is generated by the meshing movement of the worm wheel with the sine-shaped tooth, but just the end face of the worm(with three different typical meshing types) is adapted to meshing, and therefore an extraordinary manufacturing methods is used to generate the profile of the end face engagement worm. The research results indicates that the bearing contacts of the generated conjugate hourglass worm gear set are in line contacts, with certain advantages of no-backlash, high precision and high operating efficiency over other gears and gear systems besides the end face engagement worm gear drive may improve bearing contact, reduce the level of transmission errors and lessen the sensitivity to errors of alignment. Also, the end face engagement worm can be easily made with superior meshing and lubrication performance compared with the conventional techniques. In particular, the meshing and lubrication performance of the end face engagement worm gear by using the end face to meshing can be increased over 10% and 7%, respectively. This investigate is expect to provide a new insight on the design of the future no-backlash worm drive for industry.展开更多
基金Project(51175505)supported by the National Natural Science Foundation of China
文摘A nonlinear model of anti-backlash gear with time-varying friction and mesh stiffness was proposed for the further study on dynamic characteristics of anti-backlash gear. In order to improve the model precision, applied force analysis was completed in detail, and single or double tooth meshing states of two gear pairs at any timing were determined according to the meshing characteristic of anti-backlash gear. The influences of friction and variations of damping ratio on dynamic transmission error were analyzed finally by numerical calculation and the results show that anti-backlash gear can increase the composite mesh stiffness comparing with the mesh stiffness of the normal gear pair. At the pitch points where the frictions change their signs, additional impulsive effects are observed. The width of impulsive in the same value of center frequency is wider than that without friction, and the amplitude is lower. When gear pairs mesh in and out, damping can reduce the vibration and impact.
文摘柴油机噪声影响着农业机械操作者的身心健康,该文为了解决某型柴油机在怠速工况下的异响噪声问题,采用仿真与试验相结合的方法进行研究。首先,通过声强和声压测试确定了噪声的主要产生部位;然后,基于Hypermesh和Abaqus软件建立了曲轴及整机零部件的有限元模型,并通过模态试验验证了有限元模型的准确性,基于Excite软件建立了配气正时传动系统和整机的多体动力学模型,发动机整机振动计算时考虑了缸内燃气压力、正时系统及配气机构全阀系激励和活塞敲击激励。多体动力学仿真结果表明:齿轮的反向敲击出现时,齿轮工作面的接触力消失,进排气齿轮在背隙侧发生接触产生冲击力,进而造成发动机在怠速时产生"哒哒"的异响噪声;整机振动仿真结果表明:使用消隙齿轮可以消除进/排气凸轮轴齿轮的反向敲击,在1 000~2 500 Hz范围内,使得齿轮室盖和缸盖罩的振动速度级降低了7 d B左右。最后在半消声室的发动机台架上,对有无消隙齿轮的柴油机进行了振动加速度、噪声和声品质的对比试验,试验表明:怠速工况下,使用消隙齿轮后,前端发出的"哒哒"异响噪声消失,齿轮室盖振动降幅很大,前端1 m噪声声压级降低了5~9 d B(A),声品质也有了明显改善。因此,当内燃机其它齿轮传动部位出现齿轮反向敲击声时,可考虑使用消隙齿轮予以解决。
基金Supported by National Natural Science Foundation of China(Grant No.51305356)Spring Sunshine Plan of Ministry of Education of China(Grant No.14202505)Talent Introduction of Xihua University,China(Grant No.Z1220217)
文摘A novel specific type of worm drive, so-called end face engagement worm gear(EFEWD), is originally presented to minimize or overcome the gear backlash. Different factors, including the three different types, contact curves, tooth profile, lubrication angle and the induced normal curvature are taken into account to investigate the meshing characteristics and create the profile of a novel specific type of worm drive through mathematical models and theoretical analysis. The tooth of the worm wheel is very specific with the sine-shaped tooth which is located at the alveolus of the worm and the tooth profile of a worm is generated by the meshing movement of the worm wheel with the sine-shaped tooth, but just the end face of the worm(with three different typical meshing types) is adapted to meshing, and therefore an extraordinary manufacturing methods is used to generate the profile of the end face engagement worm. The research results indicates that the bearing contacts of the generated conjugate hourglass worm gear set are in line contacts, with certain advantages of no-backlash, high precision and high operating efficiency over other gears and gear systems besides the end face engagement worm gear drive may improve bearing contact, reduce the level of transmission errors and lessen the sensitivity to errors of alignment. Also, the end face engagement worm can be easily made with superior meshing and lubrication performance compared with the conventional techniques. In particular, the meshing and lubrication performance of the end face engagement worm gear by using the end face to meshing can be increased over 10% and 7%, respectively. This investigate is expect to provide a new insight on the design of the future no-backlash worm drive for industry.