The transmission system of a motorcycle consists of several parts such as primary deceleration, clutch, gearbox, and secondary deceleration.
1. Primary deceleration
The primary deceleration is mainly composed of the driving sprocket (driving gear) installed on the crankshaft end, the sleeve roller chain and the driven sprocket (driven gear) on the clutch, as a deceleration and transmitting the engine power to the clutch.
2. Clutch
Motorcycle clutches have the following structural types:
(1) Wet multi-plate friction clutch The clutch assembly is immersed in engine oil to work, and it is divided into three parts: active, driven and separated. The power of the engine is driven by a sprocket-type gear to the drive cover. There are grooves on the periphery of the cover. Five signs are embedded with friction plates (active plates) of rubber cork friction material. The bumps on the outer edge are placed in the grooves of the drive cover. It then rotates together as the active part of the clutch. The four steel driven plates are connected with the fixed basin of the driven plates through internal teeth to form the driven part. The main and driven plates are installed alternately. The fixed basin is connected with the main shaft of the gearbox with internal splines. The four clutch springs on the gland tightly press the friction plates and the driven plates to transmit power to the gearbox. The clutch is of the normally engaged type. When the clutch handle is pressed tightly to make the screw sleeve rotate in the left cover through the steel cable, the adjusting screw in the screw sleeve moves to the right, pushing the separation push rod and the gland, the spring pressure disappears, the friction sign and the follower plate Separate.
(2) Automatic centrifugal clutch This structure is used on mopeds such as Yamaha CY80, Suzuki FR50, etc., according to the engine speed to automatically control the separation and engagement of the clutch. The clutch is composed of active, driven and disengaged engagement mechanisms. The active part is composed of clutch cover, thrust plate, clutch plate and so on. The driven part is composed of friction plate, center sleeve, etc. When the engine is running, as the speed increases, the centrifugal force generated by the steel ball also increases. Its axial component force overcomes the tension of the release spring and moves outward along the groove in the clutch cover, pressing the thrust plate tightly. The pressure clutch plate and the friction sign make the clutch in the engaged state and output the power. When the engine speed is reduced to idling or flameout, the centrifugal force of the steel ball is reduced or not. The tension of the separating spring overcomes the centrifugal force of the steel ball to return the steel ball to its original position along the groove, and the clutch is separated.
(3) The structure of shoe-type automatic clutch is used in some mini-motorcycles. The active part is a fixed seat driven by the crankshaft. There are three shoe assemblies on the seat, which are connected to the fixed seat by a pin. The block is pulled toward the center of the crankshaft to maintain a certain gap between the shoe plate of the shoe block assembly and the clutch disc of the driven part. When the rotation speed increases, the centrifugal force generated by the shoe block is greater than the pulling force of the spring, it will be thrown away, and when the centrifugal force reaches a certain value, it will engage with the clutch disc, generating friction to drive the driven part to rotate and transmit power.
3. Secondary reduction and transmission
With different motorcycle models, there are three transmission modes: belt drive, chain drive and universal joint shaft drive. In mini-motorcycles, belt transmission is often used as the rear transmission device, and the size of the main and driven pulleys determines the secondary reduction ratio. Generally, motorcycles use chain drive for rear drive. Chain drive, simple structure, few parts, easy to manufacture and repair. There is a rear drive driving sprocket on the output shaft of the gearbox and a driven sprocket on the rear wheel, and the corresponding sleeve roller chain is used to transmit power. In motorcycles with higher power engines (such as the Yangtze River 750 motorcycle), its rear drive adopts universal joint shaft transmission, and the rear wheel is equipped with a subsidized speed reduction of a spiral bevel gear.