Motorcycle classification and its basic composition

A motorcycle classification

For the classification of motorcycles, different countries have different classification methods. The International Standard (ISO3833-1977) classifies motorcycles into two categories based on speed and weight: dual-use motorcycles and motorcycles. There are roughly two classification methods for motorcycles in China: one is according to the displacement and the highest design speed, divided into mopeds and motorcycles. Moped engine working volume does not exceed 50 ml, and the maximum design speed is not more than 50 km/h. A motorcycle is a two or three-wheeled motorcycle with an engine capacity of more than 50 milliliters and a maximum design speed of more than 50 kilometers per hour. The other is based on the number and location of the wheels, divided into three categories of two-wheeled vehicles, side tricycles and tricycles.

It is customary to categorize according to use, structure and engine type and work volume. For example, if it is used only as a means of transport within a short distance of a city, a micro-motorcycle or moped with a speed of no more than 50 kilometers and a compact and compact structure is selected. Need to go between urban and rural areas often, can ride two people, should choose the engine working volume 125 ~ 250 ml ordinary motorcycle. If you have poor road conditions and require high-speed driving or general competition, use off-road motorcycles.

Second, the basic composition of motorcycles

The motorcycle consists of five parts: engine, transmission system, traveling system, steering, braking system and electrical instrumentation equipment. The overall structure of the motorcycle and the names of its components.

(a) Engine

1, the characteristics of motorcycle engines

(1) The engine is a two-stroke or four-stroke gasoline engine.

(2) Air-cooled cooling, natural air cooling and forced air cooling. General models rely on natural air-cooling cooling methods that rely on the air blowing through the cylinder head and the heat sink on the cylinder liner to remove heat. In order to ensure low speed and cooling of the engine before unraveling, a high-power motorcycle engine adopts a forced air-cooling method of installing a fan and an air hood, and using forced introduction of air to cool fins.

(3) The engine speed is high, generally above 5,000 rpm. The boost power (effective power emitted per litre of engine displacement) is large, generally around 60 kW/l. This shows that the motorcycle engine has a high degree of reinforcement and the engine has a small external dimension.

(4) The engine crankcase is integrated with the clutch and gearbox design, and its structure is compact.

2, the body

The body consists of cylinder head, cylinder block and crankcase. The cylinder head is made of aluminum alloy with heat sink. The new 4-stroke motorcycle engine adopts overhead valve, chain transmission and overhead camshaft structure. The cylinder block material is made of bimetal (aluminum heat-dissipating cast iron cylinder liner), so as to obtain better heat dissipation effect. Some motorcycles use wear-resistant cast iron cylinders, such as the Yangtze River 750 type, Jialing JH70 type, in some small portable motorcycles, such as Yuhe brand YH50Q small displacement (50 cubic centimeters) engine using aluminum alloy cylinder wall 0.15 mm hard plated The structure of the chromium layer. The crankcase is made of aluminum alloy die-casting with a combination of two boxes. Some motorcycles have a buffer block between the heat dissipation signs to suppress the noise emitted by the heat sink vibrations.

3、Crank connecting rod

The crankshaft of the motorcycle engine adopts a combined type and is formed by press-fitting the left half crankshaft, the right half crankshaft and the crank pin. The main shafts of the left and right axle shafts are equipped with ball bearings for supporting the crankshaft on the crankcase. Both ends of the crankshaft are equipped with flywheels, magneto motors and clutch drive gears, respectively. The connecting rod has a monolithic structure with a large head in the form of a circular ring and is internally provided with a needle roller bearing and a crank pin which are combined into a crank connecting rod group. In the two-stroke engine, when installing the piston ring, the opening of the piston ring must be aligned with the positioning pin in the piston ring groove to prevent the piston ring from rotating in the ring groove, resulting in air leakage and scratching the inlet and the row on the cylinder sleeve. Air port.

4, carburetor

The carburetor is an important component of the motorcycle fuel supply system and is located between the air cleaner and the engine air intake. General motorcycle engines use the intake air flow direction as the suction type, the throttle valve is a plunger type, and the float chamber type carburetor. The carburetor structure mainly consists of two parts: the float chamber and the mixing chamber. The float chamber is located at the bottom of the carburetor. The fuel pipe is connected to the fuel tank through the throttle switch and passes through the needle valve on the float to maintain a certain height in the oil surface of the float and stabilize the oil supply pressure. The role of the mixing chamber is to atomize the vaporized gasoline and mix the air so that the engine can obtain the desired mixture at various loads and speeds. It consists of art valves, injection needles, fuel injection pipes, and gas and oil passages.

Through the rotation of the throttle handle of the motorcycle, the throttle wire lanyard is operated to move the throttle valve and the injector needle up and down to change the cross section of the inlet throat and the fuel supply, so as to adapt to the needs of the mixture at different speeds and loads. An idling adjustment screw is installed on one side of the carburetor to adjust idle speed. The idle stop screw is used to prevent the throttle valve from turning and to adjust the minimum opening of the throttle valve. There is a return spring above the throttle valve and the throttle valve is closed when the throttle handle is not rotating.

In some two-stroke motorcycle engines, a one-way reed valve for controlling the intake air is installed between the carburetor and the cylinder block in order to prevent the backlash phenomenon of the carburetor from occurring at a low speed. The reed is made of thin spring steel sheet. The valve seat is made of aluminum alloy. There is an air inlet on the valve seat. A layer of oil rubber is attached to the contact surface of the air inlet and the reed contact part to reduce the impact and vibration of the reed and valve seat. . When inhaling, a certain degree of vacuum is formed in the crankcase. Under the action of the pressure difference, the reed valve opens the mixture gas and enters the crankcase. When the piston descends, the ventilation port is not yet opened and the pressure in the crankcase increases. The valve is closed, preventing the reverse flow of the air-fuel mixture, improving the dynamic and economical performance of the engine at low speed.

5, lubrication system

The four-stroke engine uses a combination of splash lubrication and pressure lubrication. Two-stroke engines are generally used in a mixed lubrication system in which gasoline is mixed with a certain percentage of QB-grade gasoline engine oil. However, regardless of the engine operating conditions, the lubricant oil of this kind of lubrication method supplies lubricant oil at a predetermined ratio, increases the consumption of lubricant oil, incomplete combustion, and has a large amount of coke deposition and exhaust pollution. The new generation of two-stroke engines are separated and lubricated with a separate lubricated oil reservoir and oil pump. The oil pump generally uses a reciprocating plunger-type variable oil supply pump. The crankshaft gear is driven by a worm gear and a worm. The amount of oil supplied is linked to the throttle valve of the carburetor through the throttle handle, the control cable, and the engine oil supply amount changes with the change of the engine speed. The oil supply at high speed is more, the oil supply is less at a low speed, the oil supply is reasonable, and the oil supply is reasonable. Compared to the way it can save more oil. The oil is blown into a tiny mist through the high-speed air-fuel mixture to supply the parts that need to be lubricated to reduce the oil that enters the combustion chamber. The mixture burns completely, reducing coke and exhaust pollution.

6, start

The starting of the motorcycle is mainly based on the pedal starting method. The starting mechanism is a sector gear starting mechanism represented by the XF250 motorcycle. The pedal activates the gear shifter to drive the sector gear, the starter ratchet, the clutch assembly sprocket, the front chain, and the crankshaft sprocket to drive the crankshaft to rotate and start the engine. When the engine is started, the starting mechanism is returned to its original position by the one-way action of the starting ratchet and the action of the return spring. This kind of starting mechanism, when starting, put the starting gear lever to the neutral position, and step on the pedal to start.

The other is a start-up lever type starter mechanism used by some introduced models. Unlike the former, when starting, the clutch handle must be squeezed first to disengage the clutch. The shift lever can be placed in any position. It does not have to be placed in neutral. After starting, the clutch is released and the throttle can be started. When depressing the starting mast, the pawl on the starting mast shaft meshes with the inner ratchet teeth of the starting mast transmission gear, so that the transmission gear rotates, and the crankshaft is driven by the idle gear, the driven gear, the clutch gear, and the starter pinion gear Start the engine. After starting, the foot leaves the starting mast, the return spring rotates the mast in the opposite direction, and the pawl disengages from the inner ratchet teeth to restore the original position.

Motorcycles such as Changjiang Brand 750D Motorcycle, YAMAHA Two-cylinder Motorcycle, SUZUKI GT750 Three-cylinder Motorcycle and Honda-Honda CL1000 Four-cylinder Motorcycle are all used to start larger displacement motorcycles. Motor start.

(b) Transmission system

The transmission system of the motorcycle consists of primary deceleration, clutch, gearbox and secondary deceleration.

1, the primary deceleration

The primary deceleration is mainly composed of a driven sprocket (drive gear) mounted on the crankshaft end, a sleeve roller chain, and a driven sprocket (driven gear) on the clutch, serving as a deceleration and transmitting the engine power to the clutch.

2. Clutch

Motorcycle clutches have the following types of structure:

(1) The wet multi-plate friction clutch clutch assembly is immersed in the oil and is divided into three parts: active, driven and separated. The power of the engine is transmitted through the sprocket gear drive active cover, the periphery of the cover is grooved, and the five signs are embedded with rubber cork friction material (active sheet), and the outer edge bumps are placed in the groove of the active cover. With one of the same rotation as the active part of the clutch. The four steel follower plates are connected to each other via the inner teeth and the follower plate fixing basin to form the driven part. The main and follower plates are staggered and installed. The fixed pots are connected to the transmission main shaft by internal splines. The four clutch springs on the gland cover press the friction plates and follower plates to transmit power to the transmission. The clutch is normally engaged. When the clutch handle is tightly squeezed, the screw sleeve is rotated in the left cover by the wire rope, the adjusting screw in the screw sleeve is moved rightward, the push rod and the cover are separated, the spring pressure disappears, the friction sign and the follower piece Separated.

(2) Automatic centrifugal clutch This type of structure is used on light motorcycles such as the Yamaha CY80 and Suzuki FR50. The clutch is automatically separated and engaged according to the engine speed. The clutch consists of active, driven, and disengaged joints. The active part consists of the clutch cover, thrust plates, and clutch plates. The driven part consists of a friction plate, a center sleeve, and the like. When the engine is running, as the rotation speed increases, the centrifugal force generated by the steel ball also increases, and its axial component force moves outward along the groove in the clutch cover against the tension of the separating spring, compressing the thrust piece tightly. Pressing the clutch plate and the frictional clutch make the clutch engaged and output power. When the engine speed is reduced to enthalpy or flameout, the centrifugal force of the steel ball decreases or not, and the tension of the separating spring overcomes the centrifugal force of the steel ball to retreat the steel ball along the groove and the clutch disengages.

(3) Shoe block type automatic clutch This kind of structure is used in some micro-motorcycles. The active part is a fixed seat driven by the crankshaft. There are three shoe block assemblies on the seat, and the pins are connected to the fixed seat. The spring will move the shoes. The block is pulled toward the center of the crankshaft to maintain a certain clearance between the shoe of the shoe block assembly and the clutch plate of the driven portion. When the rotation speed increases, when the centrifugal force generated by the shoe is greater than the pulling force of the spring, it throws outwards. When the centrifugal force reaches a certain value, it engages with the clutch plate to generate a friction force to drive the driven part to rotate and transmit power.

3, secondary deceleration and transmission

With the different motorcycle models, there are three transmission methods: belt drive, chain drive and universal joint shaft drive. In the micro-motorcycles, belt drives are used as the rear drive. The size of the main and driven pulleys determines the secondary speed reduction ratio. General motorcycles use chain transmission as the rear drive. Chain drive, simple structure, fewer parts, manufacturing and repair are convenient. On the output shaft of the gearbox, there is a rear drive drive sprocket, and on the rear wheel there is a driven sprocket, and the power is transmitted by the corresponding sleeve roller chain. In a motorcycle with a larger power engine (such as the Yangtze River 750 motorcycle), its rear drive adopts universal joint shaft transmission, and it is equipped with a subsidy-grade deceleration for the rear bevel gear.

(III) Walking System

The function of the walking system is to support the weight of the whole vehicle and the loading, to ensure the stability of the operation and the comfort of riding. The walking system mainly includes a frame, a front fork, a front shock absorber, a rear shock absorber, and a wheel.

(1) Frame It is the skeleton of the entire motorcycle, which is welded by steel pipes and steel plates. It connects the engine, transmission, fork, rear suspension, etc. to each other and has high strength and rigidity. Scooters are mostly made of steel frame stamped and welded. General motorcycles use welded steel frame, cradle type frame or steel plate, and steel pipe combination frame. Some high-power engine motorcycles use steel-welded double-bracket cradle type frames.

(2) The front fork of the front fork is the guiding mechanism of the motorcycle. The frame and the front wheel are organically connected. The front fork is composed of a front shock absorber, an upper and a lower plate, and a steering column. The direction column and the lower plate are welded together, and the direction column is set in the front casing of the frame. In order to make the direction column move flexibly, axial thrust ball bearings are installed on the upper and lower neck and neck, and the left and right plates are passed through the upper and lower plates. A front shock absorber is connected to the front fork.

(3) Front and rear shock absorbers The front shock absorbers are used to attenuate the shock caused by the front wheel impact load and keep the motorcycle running smoothly.

The rear shock absorber and the rear rocker of the frame constitute the rear suspension device of the motorcycle. The rear suspension device is an elastic connection device between the frame and the rear wheel, and bears the load of the motorcycle, relieves it, and absorbs shocks and vibrations that are transferred to the rear due to the unevenness of the road surface.

(4) Wheels The front wheels of motorcycles are guide wheels, and the rear wheels are drive wheels, all of which are spoke wheels. The wheels consist of tires (inner and outer tires), rims, spokes, hubs, brake rims, bearings, and front and rear axles. The rims (steel rims) are rolled and welded with steel plates. The hubs are die-casted from aluminum alloy, and the brake steel rims are die cast into one body. Flanges are used at both ends to install spokes. The spokes are similar in shape to the bicycle spokes to connect the rim and hub. The brake is installed in the hub, the front wheel is also equipped with a worm gear and worm gear for the speedometer, and the rear wheel is equipped with a drive mechanism.

(4) Steering and braking systems

(1) The steering wheel and the handlebar cooperate to control the direction of the motorcycle. The handlebar is mounted on the upper plate. When the handlebar rotates around the direction column, the upper and lower plates rotate with it, and the front wheel is driven through the front shock absorber to rotate left and right. The right end of the handlebar is equipped with a throttle handle for controlling the opening degree of the carburetor throttle valve, and a brake handle for controlling the front wheel brake; the left side is equipped with a grip and a handle for controlling the clutch. Rearview mirrors and various electrical switches are also mounted on the right and left ends of the handlebars. Handle and brake lever control the front wheel brake, clutch and carburetor through steel cable. The wire ropes have different specifications. The brakes and clutches are made of single wire ropes of 1 × 19 OD ∮ 2 ~ ∮ 2.5 mm, and carburetors are made of single wire ropes of 1 × 7 OD ∮ 1.2 ~ ∮ 1.5 mm.

(2) Braking Generally, the front brake is controlled by the hand brake, and the rear brake is made by the foot pressing on the brake pedal. Motorcycle brakes include mechanical drum brakes and hydraulic disc brakes. The drum brake structure is similar to that of a car or a tractor. A brake shoe block is die-casted from an aluminum alloy, and a friction brake pad is stuck on the brake shoe. The brake arm rotates the brake cam and pushes the brake shoe block to act as a brake.

The brake consists of a fuel tank, a plunger valve oil pump (all on the handlebars), a hydraulic hose, a caliper, and a brake disc. Brake staggering is fixed close to the fork guide and is a fixed part of the brake device. The brake disc is fixed with the wheel and rotates with the wheel. When braking, grip the brake lever, move the plunger valve, and push the hydraulic oil along the hydraulic tubing into the two cylinders of the brake caliper. Under the action of the pressure oil, the oil cylinder pushes the friction plate to clamp the brake disc tightly from both sides, generating a great frictional resistance, forcing the wheel to stop rotating. When the brake lever is released, the pressure in the hydraulic oil circuit quickly falls back, and the oil cylinder drives the friction plate back to its original position, releasing the brake.

(5) Inspection and adjustment of motorcycles

Inspection and adjustment are required during the purchase and sale of motorcycles.

1, motorcycle inspection

First of all, a visual inspection is carried out. The parts of the vehicle should be intact and there should be no missing parts. The paint layer, the chrome plating layer, and the galvanized part should be bright and shiny without scratching and falling off. Vehicles should have product certification, product instructions, and acceptance of spare parts and tools by the packing list. Then start the inspection. At room temperature, the cold start is not more than three times. The hot car should be started with one foot. When the engine is running, there should be no abnormal sound and knocking sound, and the idle operation is stable without leakage of gasoline and oil.

2. Inspection and adjustment of components

(1) Front-wheel braking The front-wheel brake is operated by the right hand, first checking its free stroke. The so-called free stroke refers to the part of the journey from the start of the handle to the moment the brake begins to function. Before the stroke is too small, the brake shoe block and the brake drum of the front wheel are not completely detached, which affects the driving speed; the stroke is too large and the braking efficiency is affected and the brake cannot be braked in time.

(2) Rear wheel brake The rear wheel brake is controlled by a foot pedal. First, check the free travel of the brake pedal.

(3) The clutch clutch is normally operated by the left hand and checked for its free travel during adjustment.

(4) Rear shock absorber

(5) After the transmission, the adjustment of the transmission is mainly to check the tightness of the transmission chain (transmission belt). Check the position between the front and rear sprocket (pulley), and use the finger to move the chain up and down to see the distance up and down. Small The motorcycle is 10 to 20 mm, and the ordinary motorcycle is 20 to 30 mm. The tightness of the triangle drive belt, press with hand [press with 49 Newtons (5 kg force)] belt, the belt sagging 10 to 20 mm.

(6) Carburetor Idling idle is the lowest stable speed when the engine is unloaded. When the throttle handle is in the minimum position, the engine can keep running continuously. When adjusting, first start the engine, gradually turn the throttle handle, check the free stroke of the throttle handle, generally set to 2 ~ 6 mm, if the rotation does not exceed 2 mm, the engine speed increases, indicating that the free stroke is too small; such as rotation If the stroke exceeds 6 mm and the engine speed does not increase, the free stroke is too large.

(VI) Electrical Instrument

1. Arrangement of meters and switches

2, electrical circuit

The electrical circuit of a motorcycle is basically similar to that of a car. Electrical circuit is divided into power, ignition, lighting, instrumentation and audio parts.

The power supply section is generally composed of an alternator (or powered by a magneto charging coil), a rectifier, and a battery. Magneto motors for motorcycles vary in structure depending on the type of motorcycle. There are generally two types of flywheel-type magnetic motor and magnetic rotor-type magnetic motor. Flywheel type magneto motors are generally used in small-displacement miniature and light motorcycles. In the interior of the flywheel, four magnetic steels are evenly distributed. As the engine crankshaft rotates together, the stator frame is fixed on the crankcase, and the magnets are fixed on it. The motor coil, the illumination coil, and the breaker assembly, when the flywheel rotates, the magnetic field lines alternate through the coils, causing the coils to generate inductive alternating current. In the magnetic rotor type magnetic motor, its structure is opposite to the above, six magnetic steels are evenly distributed on the circumference of the rotor. The magnetic steel and the rotor are die-casted together with an aluminum alloy, and the rotor is connected with the crankshaft by a key. Six coils wound around the core are distributed within the stator. As the rotor rotates within the stator, the lines of magnetic force alternate through the stator coils to induce AC induction.

Ignition methods for motorcycles include battery ignition systems, magneto ignition systems, and transistor ignition systems. In the ignition system, there are two types: contact capacitor discharge ignition and contactless capacitor discharge ignition. Non-contact capacitor discharge is abbreviated as C. D. I, C. D. I actually refers to the combination of capacitive charge and discharge circuit and thyristor switch circuit, commonly known as electronic ignition.

There are various colors of wires distributed in the motorcycle circuit. It is customary to use the red wire as the power “+” wire, the black wire as the ground wire “-” wire, the orange wire as the ignition coil wire, and the magneto output current as the white wire. Blue is the headlight line, etc. This is just a general idiom for reference.