In order to solve the problem of serious squealing and knocking noise of helical gears in the reduction gearbox, improve the current situation of excessive vibration noise caused by dynamic excitation in the process of helical gear engagement, reduce the serious wear of automotive helical gears in the meshing area due to long-term high strength working conditions, and avoid excessive increase in the cost of helical gear processing and manufacturing, many scholars began to apply helical gear modification technology to engineering practice. At present, helical gear modification technology is mainly divided into two types: profile modification and tooth direction modification according to different efficacy.
As shown in Figure 1, tooth profile modification is a means to remove the “interference” parts of helical gear pair under the non ideal meshing state, reduce the meshing in and meshing out impact generated during the actual meshing of helical gear pair, and effectively improve the degree of sudden change of the load on gear teeth when the number of meshing teeth changes alternately, so as to avoid the violent vibration of helical gear.
If the material removal parts of helical gears are distinguished, the tooth profile modification can be divided into addendum modification, addendum root modification, and root modification. If the major and minor modification gears are selected, the tooth profile modification can be divided into large gear modification, simultaneous modification of major and minor gears, and pinion modification. If the modified tooth shape is distinguished, the tooth profile modification can be divided into linear modification, arc modification, involute modification, etc. Figure 2 shows the schematic diagram of different tooth profile modification shapes. Although there are many types of tooth profile modification, they can not be separated from three key parameters: modification curve, modification length and modification amount.