The chain tensioner acts on the timing belt or timing chain of the engine, guiding and tensioning it, so that it is always in the optimal tension state. Generally divided into oil pressure and mechanical methods, they can automatically adjust the tension of the timing belt and timing chain.

Driven by the timing belt or timing chain, the camshaft drives the valve to open and close at the correct time, and cooperates with the piston to complete the four processes of intake, compression, work and exhaust. Because the timing belt and timing chain will jump when running at medium and high speeds, and the timing belt will be elongated and deformed due to the belt material and force during long-term use, resulting in jumping teeth, resulting in inaccurate timing of gas distribution. This may cause malfunctions such as fuel consumption, weakness, and knocking. When the teeth jump too much, because the valve opens too early or closes too late, the valve will collide with the upward piston and damage the engine.

In order to keep the timing belt and timing chain with proper tension, that is, not too loose and the teeth jump or damage due to too tight, there is a special tensioning system, which consists of a tensioner and a tensioner or Guide rail composition. The tensioner provides pressure directed to the belt or chain. The tensioner wheel is in direct contact with the timing belt, and the guide rail is in direct contact with the timing chain. They operate with the belt or chain while exerting the pressure provided by the tensioner on it. , So that they maintain a proper degree of tightening.