在 正时皮带或正时链条的传动下，凸轮轴驱动气门在正确的时间开闭，配合活塞完成进气、压缩、做功和排气四个过程。由于正时皮带和正时链条在中高速运转时会发生跳动，而且正时皮带在长期使用中会因为皮带的材质和受力，发生拉长、变形产生跳牙导致配气正时的不准确，从而引起车辆费油、无力、爆震等故障。当跳牙过多时因为气门 过早打开或过晚关闭还会使气门和上行的活塞碰撞损坏发动机。为了能让正时皮带和正时链条保持合适的涨紧度，即不因过松而跳牙也不因过紧而发生损坏，有一个专门的涨紧系统，由涨紧器和涨紧轮或导轨组成。涨紧器提供指向皮带或链条的压力，涨紧轮与正时皮带直接接触，而导轨直接与正时链条 接触，它们在随皮带或链条运转的同时将涨紧器提供的压力施加在其上，使它们保持合适的涨紧程度。
under the timing belt or timing chain drive, camshaft drive valve at the right time to open and close, with the piston to complete the intake, compression, work and exhaust four processes. Because of the timing belt and timing chain in high-speed operation will occur when the beating, and timing belt in the long-term use because of belt materials and stress, deformation, occurrence of elongated teeth caused valvetiming inaccurate, causing the vehicle costs oil, weakness, detonation. When the valve is too long or the valve is too early to open or close the valve and the piston will crash the engine damage. In order to make the timing belt and timing chain to maintain the appropriate tension, that is, not too loose because of jumping teeth and not too tight and damage, there is a special tension system, by the tensioner and the tension wheel or rail composition. Tensioner provided to the belt or chain pressure, timing belt tensioner and direct contact, and direct and guide the timing chain contact with them in the belt or chain operation will also provide the tensioner pressure exerted on it, so that they maintain appropriate tension degree.