Do you know what a tensioner bearing is? See how it works

(1) Concept

With the popularization and application of high-position camshafts and overhead camshafts in modern automobile engines, the synchronous chain transmission and gear transmission of camshafts have gradually been replaced by toothed belt transmissions. At the same time, the transmission of the fuel injection pump of the automobile diesel engine also uses a synchronous toothed belt. In order to facilitate the installation and adjustment of the synchronous toothed belt, it is generally necessary to use a tensioner on the loose edge of the toothed belt. In a more complex toothed belt drive, a fixed idler is often used on the tight side of the toothed belt to increase the wrap angle of the transmission wheel or change the position of the toothed belt.

(2) Design analysis

1. Tensioner for seat plate installation

There are two typical designs for the tension wheel with the seat plate. It is provided with an oscillating tension belt passing through the seat plate, and the seat plate is fixed by a bolt; by the oscillating tension belt of the seat plate, but fixed by a bolt passing through the inner hole of the bearing . The rolling INA bearings used in the above two designs are double-row radial sealed ball bearings. In the tension wheel installed on the seat plate, single-row radial sealed ball bearings are often used.

2. Eccentric tensioner

The eccentric tensioning wheel is used to tension the belt by swinging around the eccentric hole in the supporting pin. The supporting pin is fixed by a double-ended stud and a nut passing through the eccentric hole.

3. Lightweight design

The most noticeable development of the aforementioned tensioner is the so-called lightweight design. The development of light-weight design has greatly reduced the quality of the tensioner, and at the same time effectively reduced the manufacturing cost of the tensioner.

4. The role of tensioner

The function of the tensioner is to adjust the tightness of the timing belt, maintain the belt tension, avoid belt slippage, and compensate for the elongation caused by belt wear and aging. Adjust and compensate the deviation of the center distance of the engine system caused by the machining error of the shaft and the positioning hole. To a certain extent, it can eliminate the abnormal noise in the operation of the engine block caused by the extension or swing of the belt. Suppress the vibration of the transmission system .

5. Working principle of tensioner

When the engine system is unloaded, the belt that the tensioner is close to will become slack in the case of poor tension, that is, the tensioner needs to react quickly along its own central axis under the torsion force of the torsion spring. The hour hand swings to make up for the reduction of the tension on the belt in time; on the contrary, when the crankshaft performs a loading motion, the belt that the tensioner is close to will be further tightened, and the pulley needs to rotate and swing along its own central axis. At the same time, the kinetic energy of the belt system is converted into the elastic energy of the torsion spring and stored in the torsion spring for use during unloading. In order to maintain proper belt tension, avoid belt slippage, compensate belt wear and elongation caused by aging, the tensioner needs a certain torque during actual use. When the belt tensioner is running, the moving belt may excite vibration in the tensioner, which will cause premature wear of the belt and tensioner. To this end, a resistance mechanism is added to the tensioner. However, because there are many parameters that affect the torque and resistance of the tensioner, the influence of each parameter is not the same, so the relationship between the components of the tensioner and the torque and resistance is very complicated. The torque change directly affects the change of resistance, and it is the main influencing factor of resistance. The main factor that affects the torque is the parameter of torsion spring. Appropriately reducing the middle diameter of the torsion spring can increase the resistance value of the tensioner.