What is a Coincident Indicator?

Gear transmission is achieved by the sequential meshing of each pair of gears. The ratio of the length of the actual meshing line to the pitch of the base circle is called coincidence. In order to enable continuous transmission of gears, it should be ensured that when the first pair of gears are disengaged, the latter pair of gears will be engaged, so the coincidence degree should be greater than 1.

To keep the two gears continuous and stable in the transmission, it is necessary to ensure that before the end of the meshing of the first pair of tooth profiles (at least at the same time), the second pair of tooth profiles have already meshed, otherwise the transmission will be interrupted. As you can see in the picture to the right, when a pair of teeth

When the point is disengaged,

Coincidence of externally meshed standard spur gears

As shown on the right, the actual meshing line

,and:

(1) As a condition for measuring the continuous transmission of gears, it should meet the coincidence degree

. The greater the coincidence degree, the better the continuity and smoothness of the gear transmission. In general machinery manufacturing, the allowable coincidence degree of gear transmission

, Which means

.

(2) The average value of the number of pairs of gear teeth participating in the meshing at the same time, such as

Means that on average 1.6 pairs of gears are engaged. According to this, the single-tooth meshing interval and the double-tooth meshing interval can be obtained to reflect the transmission state of the gear.

(3) As an index to measure the bearing capacity of the gear and the smoothness of the transmission. The greater the degree of coincidence, the better the smoothness of the transmission ^[2] .