Tension wheel bearing

(1) Concept

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

(2) Design analysis

1. The tensioning wheel installed on the seat plate

There are two typical designs for the tensioning wheel with the seat plate. The seat plate is fixed by a bolt through the swinging tensioning belt of the seat plate.By the swing tensioning belt of the seat plate, but fixed by bolts through the inner hole of the bearing.The rolling bearings used in the above two designs are double-row centripetal sealed ball bearings.In the tensioning wheel mounted on the seat plate, a single row centripetal sealed ball bearing is often used.

2. Eccentric tensioning wheel

The eccentric tensioning wheel tensifies the belt by swinging around the eccentric hole in the supporting pin. The supporting pin is fixed by a double-headed stud through the eccentric hole and a nut.

3. Lightweight design

The most striking development of the above-mentioned tensioning wheel is the so-called lightweight design.The development of lightweight design greatly reduces the quality of the tensioning wheel, and also effectively reduces the manufacturing cost of the tensioning wheel.

4. Function of tensioning wheel

The function of the tensioning wheel is to adjust the tightness of the timing belt, maintain the tension of the belt, avoid the slip of the belt, and compensate the elongation caused by the wear and aging of the belt.Adjusts and compensates the deviation of engine system center distance caused by machining error of shaft and orifice.To a certain extent, the abnormal sound caused by belt extension or swing in the operation of the engine set can be eliminated.Suppresses the vibration of the transmission system

5. Working principle of tensioning wheel

When the engine system is unloaded, the belt that the tensioning wheel is close to will become relaxed under the condition of tension difference, that is, the tensioning wheel needs to swing rapidly counterclockwise along its own central axis under the action of torsion spring torque and make up for the tensioning force on the belt.On the contrary, when the crankshaft is loaded, the belt against which the tensioning wheel is attached will be further tightened. At this time, the pulley needs to rotate and swing along its own central axis. Meanwhile, the kinetic energy of the belt system will be 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 slip, compensate for belt wear and aging caused by elongation, the tensioning wheel needs a certain torque.When the belt tensioner is in operation, the moving belt may arouse vibration in the belt tensioner, which will cause premature wear of the belt and the belt tensioner.To this end, the tension wheel to add resistance mechanism.However, because there are many parameters affecting the torque and resistance of the tensioner, and the influence of each parameter is not the same, the relationship between the components of the tensioner and the torque and resistance is very complicated.The change of torque directly affects the change of resistance, and is the main factor affecting the resistance. The main factor affecting the torque is the parameter of torsion spring.The resistance value of the tensioning wheel can be increased by appropriately reducing the middle diameter of the torsion spring.