In the process of shape modification development and application research aimed at the bottleneck problem of helical gear vibration noise and strength (life), many enterprise helical gear design engineers blindly experienced shape modification or even compound shape modification, which not only caused the accident of helical gear strength (life) reduction and transmission noise increase, but also reduced the enterprise benefit. In order to reduce the occurrence of such accidents and provide a set of systematic gear modification ideas, this chapter, on the basis of fully understanding the mechanism of gear vibration and noise, comprehensively considers the selection of tooth tip and root modification, long and short modification, profile and tooth direction modification, large and small modification, gear tooth modification and composite modification of tooth profile and tooth direction, Based on KISSsoft software, the modification scheme of helical gear pair of an electric vehicle gearbox was preliminarily optimized with the goal of reducing transmission error and Hertz contact stress, and the influence of helical gear parameters and gear modification technology on its meshing performance was explored and summarized, hoping to be helpful or enlightening to gear design engineers.
Taking the helical gear pair of an electric vehicle gearbox as the research object, the influence of helical gear modification technology and helical gear parameters on its meshing performance is investigated by using KISSsoft software, and a preliminary optimization modification scheme is obtained with the goal of reducing transmission error and Hertz contact stress. The main conclusions are as follows:
(1) The transmission efficiency and Hertz contact stress of helical gear pair can be improved by properly increasing the tooth width and pressure angle of helical gear, but the transmission error will be increased; Proper helix angle can reduce transmission error and Hertz contact stress of the helical gear pair, but larger helix angle is, lower transmission efficiency is.
(2) Under the premise of tooth top modification of long tooth profile (linear, involute, circular arc, broken line circular arc), it is recommended to modify both large and small gears or only large gears. If only small gears are modified, it will only increase the cost and cannot reduce the transmission error and Hertz contact stress.
(3) The tooth profile modification is mainly to reduce the Hertz contact stress on the tooth surface of the gear, that is, to improve the strength (life) of the helical gear, but also to reduce the transmission error; The tooth modification is mainly to reduce the transmission error, that is, to reduce the internal dynamic excitation of the gear, but also to reduce the Hertz contact stress.
(4) When only long tooth profile tooth top modification (linear, involute, circular arc, broken line circular arc) is adopted for large gears, the possibility of compound modification shall be considered.
(5) From the point of view of reducing the Hertz contact stress and transmission error of helical gear, among all the preliminary optimization modification schemes of the helical gear pair, the linear effect of the addendum of long tooth profile is the best when the big and small gears are modified at the same time; When the tooth profile is drum shaped, the effect is better only for big gears or small gears; The drum shape effect of tooth profile is best only for big gear modification.
(6) After preliminary optimization and modification, the meshing performance (oil film thickness, flash temperature, contact temperature, tooth surface load distribution, etc.) of the helical gear pair is obviously improved.