Motorcycle Transmission System
The transmission system of a motorcycle consists of several parts, including primary reduction, clutch, gearbox, secondary reduction, etc.
1. Primary deceleration
The primary reduction 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, which acts as a primary reduction and transmits the engine power to the clutch.
2. Clutch
Motorcycle clutches have the following types of structures:
(1) The wet multi plate friction clutch assembly is immersed in oil and operates in three parts: active, driven, and disengaged. The power of the engine is transmitted through a chain wheel type gear transmission active cover, with grooves around the cover. The friction plates (active plates) made of rubber and cork friction materials are embedded in the five features, and the convex blocks on the outer edge are placed in the grooves of the active cover, which then rotate together to form the active part of the clutch. Four steel driven plates are connected to the fixed basin of the driven plate through internal teeth to form the driven part. The main and driven plates are installed in a staggered manner, and the fixed basin is connected to the gearbox main shaft with internal splines. The four clutch springs on the pressure cover tightly press the friction plate and driven plate, transmitting power to the gearbox. The clutch is a normally engaged type. When the clutch handle is tightly pinched to make the screw sleeve rotate in the left housing through a steel cable, the adjusting screw in the screw sleeve moves to the right to push the release push rod and gland, the spring pressure disappears, and the friction sign separates from the driven plate.
(2) The structure of automatic centrifugal clutch is used in moped such as Yamaha CY80 and Suzuki FR50 to automatically control the separation and engagement of the clutch according to the engine speed. The clutch consists of an active, driven, and disengaged engagement mechanism. The active part consists of a clutch cover, thrust plate, clutch plate, etc. The driven part is composed of friction plates, center sleeves, etc. When the engine is running, as the rotational speed increases, the centrifugal force generated by the steel ball also increases. Its axial component overcomes the tension of the separation spring and moves outward along the groove in the clutch housing, compressing the thrust plate and pressing the clutch plate tightly. The friction characteristic causes the clutch to be in a engaged state, outputting power. When the engine speed decreases to idle or stalls, the centrifugal force of the steel ball decreases or disappears. The tension of the release spring overcomes the centrifugal force of the steel ball, causing the steel ball to return to its original position along the groove, and the clutch disengages.
(3) The structure of shoe type automatic clutch is used in some micro motorcycles. The active part is a fixed seat driven by the crankshaft, which has three shoe assemblies connected to the fixed seat with a pin. The spring pulls the shoe towards the center of the crankshaft, maintaining a certain gap between the shoe of the shoe assembly and the clutch disc of the driven part. When the speed increases, the centrifugal force generated by the shoe block is greater than the tensile force of the spring, and it swings outward. When the centrifugal force reaches a certain value, it engages 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 transmission, chain transmission and universal joint shaft transmission. In micro motorcycles, belt transmission is commonly used as the rear transmission device, and the size of the main and driven pulleys determines the secondary reduction ratio. Generally, motorcycles use chain transmission for rear transmission. Chain drive, simple structure, few parts, convenient manufacturing and repair. There is a rear drive sprocket on the output shaft of the gearbox, and a driven sprocket on the rear wheel. The corresponding sleeve roller chain is used to transmit power. In the motorcycle with larger engine (such as Changjiang 750 motorcycle), its rear transmission mode adopts universal joint shaft transmission, and the rear wheel is equipped with a pair of spiral bevel gears for secondary deceleration.
