Straight tooth profile gear is a new-style stamping gear.It can not only be conveniently machined and easy to obtain high precision of tooth surface

but also low cost and high precision transmission.Based on meshing theory

by using the principle of coordinate transformation

tooth profile equations and meshing line equations of the special mating gear pairs are deduced.By using the calculated conjugate tooth profiles

the change of transmission ratio is analyzed by example of calculation when center distance deviates from the standard distance

which lays a theoretical foundation for its correct application and further research of noise and vibration during the process of transmission.