In mechanical transmission, gear transmission, belt pulley transmission and sprocket transmission are the three most common transmission mechanisms. Compared with belt pulley drive and sprocket drive, involute gear drive has the characteristics of high transmission efficiency, stability, small size of mechanism, etc., so gear drive is most widely used. There are three common types of gear tooth profiles: involute tooth profile, circular arc tooth profile and cycloidal tooth profile, and the involute tooth profile has the characteristics of fixed transmission ratio, so the involute gear is the most common.
(1) For standard involute gears with standard installation, the starting point of engagement is the intersection of the addendum circle of the driven gear and the theoretical engagement line, and the end point of engagement is the intersection of the addendum circle of the driving gear and the theoretical engagement line. The actual engagement line is a section of the theoretical engagement line, which is the engagement process of full tooth involute gears. If it is an incomplete gear, its meshing line will change.
(2) The more teeth, the greater the coincidence, the more stable the transmission, and the greater the power and torque that can be transmitted. Therefore, when designing the involute gear, it is necessary to consider not only the size of the involute gear allowed by the cost and position, but also the torque, power, coincidence, etc. transmitted by the involute gear.