Theoretical Analysis And Experimental Investigation Of An Involute Cylindrical Worm-helical Gear Drive

This research is supported by the Natural Science Foundation of China (grant No.50175112).Involutes cylindrical worm and wheel drive can achieve a big drive ratio, and smooth transmission, has less noise , and it can also be made self-locking when necessary. Its shortcomings include large sliding velocity along tooth trace, leading to low drive efficiency; poor lubricate condition, and big heat generation during the gear tooth engagement. It needs hobboing cutter or specially made cutting tools , the processing cost of the former is high, and the latter has low processing efficiency and poor processing precision, and because the geometry of tooth profile shape is very complex, the worm tooth flank can not be grinded, so can not reach higher precision. However, cylindrical helical gear can adopt all basic processing methods of gear shape . It not only suits a large quantity of production, but also suits the single production; and the flexibility of gear production is very good, and it can reduce the cost greatly. The manufacture of helica gears, especially after shrewd roll flute, its precision can raise a lot and, strength the hardness largely. with the worm helical gear drive, it can avoid various shortcoming of the wheel processing, and maintain the advantages of the cylindrical helical gears, such as convenient processing, shortcut, high efficiency and so on, An hence, it can raise production efficiency and reduce produce cost greatly.This project is to carry out theoretical and experimental investigation for the worm helical gear drive, to gain the necessary knowledge and understanding of its mating characteristics and performance. In the theoretical aspect, the following have been analyzed: the meshing principle of the worm helical gear drive, lubrication condition and the correct meshing condition that use helical gear to replace worm. In the experimental aspect, the work carried out includes design and made the mechanical drive-testing stand, and comparison of the mechanical drive efficiency for worm and wheel drive and the worm helical gear drive. The results reveal that, in some cases, the efficiency of helical gear is not as good as that of worm and wheel drive ; however, the efficiency of the worm helical gear drive in certain torque and the scope of rotational speed is still more close to that of worm and wheel drive. In order to improve the efficiency of the worm helical gear drive further, according to the theory of gear tooth profile modification, the gear tooth profile modification to the helical gear has been carried out by the way of hand work, then the experiment is conducted. The results showed that the drive efficiency of the worm helical gear can be improved a lot, which nearly reach to the level of the worm and wheel drive, presently, this show us a beautiful prospect of the engineering application of the worm helical gear drive.