Basic Parameters of Roller Chain

# Basic Parameters of Roller Chain

Summary

Roller chains have the advantages of high transmission efficiency and strong overload capacity and have great applications in transportation and transmission in various industries. This article will specifically introduce the basic parameters of the roller chain.

The different components of the roller chain have corresponding parameters, and the different parameters also determine the type and size of the roller chain. If you want to choose a relatively high-quality and efficient roller chain, we need to have a detailed understanding of the following basic parameters.

1. Pitch

The distance between two adjacent pins is the pitch of the chain, which is equal to the chain number multiplied by 25.4/16mm. It is the basic characteristic parameter of the chain. The size of the pitch reflects the size of each part of the chain and sprocket teeth, and also determines the load-bearing capacity of the chain drive. Generally speaking, the larger the pitch, the higher the load-bearing capacity, but the polygon effect of the transmission will also increase, so the vibration, shock, and noise will be more serious. Therefore, under the premise of ensuring the load-carrying capacity of the chain transmission, a chain with a smaller pitch should be selected as much as possible. The selection principles are as follows:

(1) To make the transmission structure compact and have a long life, a single-row chain with a smaller pitch should be selected as much as possible.

(2) The chain speed is high and the transmission power is large, and a small pitch multi-row chain should be selected.

(3) From an economic point of view, small pitch multi-row chains should be used for transmissions with small center distances and large transmission ratios.

(4) For low-speed, heavy-duty, large center distance, and small transmission ratio, large-pitch chains are optional.

2. Number of sprocket teeth

The recommended number of teeth for z1 and z2 small sprocket is as follows: when v=0.6～3m/s, z1≥17; when v=3～8m/s, z1≥21; when v＞8m/s, z1≥25; when v=25m/s z1≥35. For chain drives that are subjected to impact loads at high speeds, at least 25 teeth should be selected for the small sprocket, and the tooth surface should be hardened. The number of teeth of the large sprocket z2 = iz1 and rounded to an integer. Usually, the maximum number of teeth of the sprocket is limited to zmax=114.

3. Transmission ratio

When the transmission ratio is too large because the wrap angle of the chain on the small sprocket is too small, the number of meshing teeth will be reduced, and the teeth skipping or the wear of the acceleration gear teeth are prone to occur. Therefore, the transmission ratio of chain drive is usually limited to I≤6, and the recommended transmission ratio is 2～3.5. When v<2m/s and the load is stable, the transmission ratio can reach 10.

4. Center distance

If the center distance of the chain drive is too small, when the transmission ratio is constant, the wrap angle of the chain on the small sprocket will decrease, and the number of meshing links between the chain and the small sprocket will decrease; at the same time, the number of chain links will be reduced. In the case of a constant speed, the number of bending extensions of the same chain link per unit time increases, which accelerates the wear of the chain. Properly increase the center distance, the chain will grow, the elasticity will increase, and the anti-vibration ability will be improved, so the wear will be slower and the chain will have a longer service life. However, if the center distance is too large, the sag of the driven side will increase, which will cause the loose side to vibrate up and down and make the transmission run unstable. Therefore, the center distance should be selected according to the recommended value. In addition, the general center distance should be designed to be adjustable, the adjustment amount is 2p, and the actual center distance is smaller than the theoretical center distance (0.002～0.004)a.

5. Row spacing

Transmission chains are divided into single-row, double-row, and multi-row. The carrying capacity of the multi-row chain is basically proportional to the number of rows.