Compound modification of globoidal worm drive with variable parameters

The meshing theory is built for the globoidal worm drive systematically. Several modification parameters, including the center distance, the transmitting ratio and the height of the cutter frame, are taken into account concurrently and they are all variable. Many types of modification in the foregoing study can be viewed as the special cases of this work. A new method is proposed to obtain the velocity ratio modification function. The height modification function is recommended to adopt a linear function, whose coefficients may be determined by the trial method. The meshing function of the worm pair is deduced by virtue of the vector rotation approach. In the case of the modification with single constant parameter, the classification standard of the drive type is proved strictly. The computing methods of the contact zone, the contact line, and the instantaneous meshing point are expounded explicitly. The reason why a globoidal worm drive can implement the double-line contact between the teeth is uncovered clearly. The reason why a modified globoidal worm gearing can shun the curvature interference is discovered. The comparative researches on the mesh characters of the diverse modified drives are implemented adequately. Some kinds of the modified drive, containing the compound modified drive with variable parameters, are recommended to be utilized in practice for the excellent mesh performances.