Seven important systems of automobile (engine, transmission, chassis, electronic appliances)

The engine is composed of two major institutions and five major systems.

Two main mechanisms of the engine:

1, crank-connecting rod mechanism

2. Air valve

Five engine systems:

1, fuel supply system

2. Lubrication system

3. Cooling system

4. Ignition system

5. Start the enrichment system

Gasoline engines are mainly divided into two major institutions and five major systems.

Two institutions

(1) crank-connecting rod mechanism

Crank-connecting rod mechanism is the main moving part of engine to realize working cycle and complete energy conversion. It consists of a machine body group, a piston connecting rod group and a crankshaft flywheel group. In the power stroke, the piston moves linearly in the cylinder under the pressure of gas, which is transformed into the rotary motion of the crankshaft through the connecting rod, and the power is output from the crankshaft. In the intake, compression and exhaust strokes, the energy released by the flywheel converts the rotary motion of the crankshaft into the linear motion of the piston.

(2) Valve train

The function of the valve train is to open and close the intake valve and exhaust valve regularly according to the working sequence and process of the engine, so that the combustible mixture or air can enter the cylinder and the exhaust gas can be discharged from the cylinder to realize the ventilation process. The valve train mostly adopts overhead valve train, which is generally composed of valve group, valve drive group and valve drive group.

These five systems include: fuel supply system, starting system, cooling system, lubrication system and ignition system.

1, fuel supply system:

The fuel supply system consists of air supply system, fuel supply system and electronic control system.

2. Start the system:

It is mainly composed of battery, starting control and transmission mechanism and starter (motor).

3. Cooling system:

The cooling system is mainly composed of water pump, radiator, fan, water jacket and thermostat.

4. Lubrication system:

Lubrication system consists of oil pump, oil filter, oil cooler and filter collector. In addition, the lubrication system also includes oil pressure gauge, thermometer and oil pipeline.

5. Ignition system:

Composition of ignition system: The traditional type consists of battery, generator, ignition coil, circuit breaker and spark plug. The common ignition system is similar to the traditional ignition system, except that the circuit breaker is replaced by electronic components. The electronic ignition system is an all-electronic ignition system, which completely cancels the mechanical device. The ignition time is controlled by electronic system, including battery, generator, ignition coil, spark plug and electronic control system.

Diesel engine has no ignition system. The working principle of diesel engine is that air enters the cylinder, is compressed into a high-temperature body, and is directly injected into the cylinder by a high-pressure diesel pump through a nozzle, and generates kinetic energy after spontaneous combustion.

However, both diesel engines and gasoline have four strokes: intake stroke, compression stroke, combustion stroke (power stroke) and exhaust stroke.

The chassis system of an automobile is a comprehensive system, which is as important as the power system of an automobile.

It specifically includes the following systems:

1. Transmission system (including clutch, transmission, transmission shaft, drive axle, main reducer, differential, half shaft, etc.). )

Second, the drive system (including frame, axle, suspension, tires and wheels)

Three, steering system (including steering gear, transmission system, control mechanism, etc.). )

4. Brake system (including wheel brake, i.e. caliper, brake pad and parking brake, i.e. hand brake).

First, the main components of automobile electrical appliances

1. Power supply system

Comprises a storage battery, a generator and a regulator. Among them, the generator is the main power supply. When the generator works normally, it supplies power to the electrical equipment of the whole vehicle and charges the battery at the same time. The function of the regulator is to keep the output voltage of the generator constant.

Battery, battery is a reversible DC power supply. The most widely used lead-acid battery in automobiles is the starting lead-acid battery, which is connected in parallel with the engine to supply power for electrical equipment. The function of the battery is to supply power to the starter and ignition system when the engine starts; When the starter does not generate electricity or the voltage is low, power is supplied to the electrical equipment; When more electrical equipment is connected at the same time and the generator is overloaded, the auxiliary generator supplies power; When the battery is insufficient and the load of the generator is less, the electric energy of the generator can be converted into chemical energy and stored. Therefore, it occupies an important position in the car. How to use and maintain the battery correctly is very important to prolong its service life. Therefore, the garage should undertake the maintenance, repair and operation of new batteries.

Generator is the main power supply of automobile electrical system. During normal operation, power is supplied to all electrical equipment except the starter, and the battery is charged to supplement the electric energy consumed by the battery in use.

The generators used in cars are DC generators and AC generators. DC generator is rectified by mechanical commutator and AC generator is rectified by silicon diode, so it is also called silicon rectifier generator.

Automobile electrical appliances are designed according to a certain DC voltage. Gasoline engines usually use 12V, and diesel engines usually use 24V. In the automobile, the generator is not only the power supply of electrical appliances, but also the charging device of batteries. In order to meet the requirements of electrical appliances and batteries, the power supply voltage and current range of generators are also limited.

The regulator of DC generator is generally composed of voltage regulator, current limiter and cut-off relay. And the alternator regulator can be greatly simplified. Because of the unidirectional conductivity of silicon diode, when the generator voltage is higher than the dynamic potential of the battery, the diode can prevent the reverse current, so the alternator no longer needs to cut off the relay.

Because the alternator has the ability to limit the output current, there is no need for a current limiter. But its voltage still varies with the speed, so it is necessary to install a voltage demodulator in order to get a constant DC voltage.

2. Start the system

Comprises a series-excited DC motor, a transmission mechanism and a control device. Its function is to start the engine.

Starter is used to start the engine, which is mainly composed of motor, transmission mechanism (or meshing mechanism) and start switch.

3. Ignition system

Include ignition switch, ignition coil, distributor assembly, spark plug, etc. Its function is to generate high-voltage electric spark and ignite the mixture in the cylinder of gasoline engine.

In modern gasoline engines, the mixture of fuel and air in the cylinder is mostly ignited by high-voltage electric spark. Spark ignition has the advantages of fast spark formation, accurate ignition time and easy adjustment and ignition of mixed gas.

In order to generate high-voltage sparks in the cylinder, a special ignition device must be used. According to different sources of electric energy, ignition devices can be divided into battery ignition and magneto ignition.

4. Lighting system

Comprise various illuminating lamp inside and outside that automobile and a control device thereof. Used to ensure the safety of driving at night. It mainly includes headlights, fog lights, taillights, brake lights, shed lights, electric horns, turn signal flashers, etc.

5. Signal system

Includes speakers, buzzers, flashers and various traffic signal identification lights. Used to ensure the safety of people and vehicles when vehicles are running.

6. Instrument system

Including all kinds of electrical instruments (ammeter, charging indicator or voltmeter, oil pressure gauge, thermometer, fuel gauge, speedometer, engine tachometer, etc. ). It is used to display the working state of the engine and related equipment when the car is running.

The function of automobile instrument is to help the driver know the working condition of the main parts of the automobile at any time, find and eliminate possible faults and unsafe factors in time, and ensure good running state. Commonly used instruments in automobiles include ammeter, water thermometer, oil pressure gauge, fuel gauge and speedometer, and some automobiles also include engine tachometer and brake cylinder barometer.

(1) ammeter

The ammeter is connected in series in the charging circuit to indicate the charging and power generation status of the battery. According to the structure, it can be divided into electromagnetic type, moving magnetic type and photoelectric indicator type. The most commonly used is electromagnetic ammeter, which has the characteristics of simple structure and vibration resistance.

(2) Oil pressure gauge

The oil pressure gauge (oil pressure gauge) can be used to indicate the engine oil pressure and whether the engine lubrication system is working normally. It consists of an oil pressure indicator installed on the dashboard and a sensor installed on the main oil passage or primary filter of the engine.

(3) Water thermometer

The water thermometer can be used to indicate whether the working temperature of the cooling water in the engine water pump is normal. It consists of a water temperature indicator installed on the dashboard and a water temperature sensor (commonly known as a temperature sensing chamber) installed on the engine cylinder head water pump, which are connected by wires. The commonly used water temperature indicator is bimetal electromagnetic type, and the sensor has bimetal and thermistor.

(4) Fuel gauge

The fuel gauge can be used to indicate how much fuel is stored in the fuel tank. It consists of two parts: the fuel indicator installed on the dashboard and the sensor installed in the fuel tank. There are two kinds of fuel indicators: electromagnetic and bimetallic, and the sensors are all variable resistors.

(5) speedometer

The speedometer is an instrument used to display the vehicle speed and accumulated mileage. It consists of speedometer and odometer.

7. Auxiliary electrical system

Including electric wiper, air conditioner, low-temperature starting preheating device, tape recorder, cigarette lighter, glass lifter, etc.

With the development of automobile auxiliary industry and the application of modern technology in automobiles, there are many auxiliary electrical equipment used in modern automobiles, except car audio equipment, communication equipment, car TV and other service equipment, which are all related to the performance of the automobile itself. Such as electric wiper, electric window washer, electric glass lifter, warm air ventilation device, electric seat moving mechanism, electric fan of engine cooling system, electric fuel pump, electromagnetic clutch of air conditioning compressor and so on. These auxiliary electrical equipment can be roughly divided into three categories: motors, electromagnetic separators and electric pumps.

(1) Two-speed electric wiper

Two-speed electric wiper generally consists of a DC parallel excitation (or compound excitation) motor and a set of deceleration transmission mechanism.

(2) Windshield anti-frost equipment

It is easy to frost on the windshield in winter, and the wiper cannot be removed. An effective way is to heat the glass. In an air-conditioned car, blowing hot air to the windshield can avoid freezing.

For cars without air conditioning, you can heat the windshield with resistance wires, and three nickel-chromium wires are stuck on the inner surface of the windshield. By heating, frosting can be prevented. This device consumes 30-50W of power, and the effect is very good. Some luxury cars abroad use electronic heaters, and the resistance wires are electrified and heated by the control of three-stage tubes.

(3) glow plug

In winter, due to the low temperature of air entering the diesel engine, the compressed mixture can not reach the ignition temperature, which makes it difficult to start. In order to make the diesel engine easy to start in winter, a glow plug is installed in the combustion chamber of the diesel engine to increase the air temperature in the cylinder.

(4) transistor electric gasoline pump

Although the diaphragm gasoline pump commonly used in automobiles has simple structure and good effect, because it is installed on the engine block, the oil supply system often has "air resistance" because of the high engine temperature in summer, which makes the gasoline circulation not smooth. In recent years, due to the development and application of semiconductors, electric gasoline pumps have been installed in automobiles to replace diaphragm gasoline pumps.

(5) Electromagnetic clutch

Electromagnetic clutch is a common automatic control element, which has the characteristics of simple operation and easy remote control. In automobiles, it is often used as the clutch for driving air-conditioning compressor and the clutch for the fan of engine cooling system. When the refrigeration capacity in the automobile air conditioning system is excessive, the drive pulley is separated from the compressor spindle through it; When the cooling capacity of the radiator of the automobile engine is excessive, the fan can slip to reduce the power consumption of the engine. In the low temperature season, only the fan clutch can reduce the fuel consumption rate of the car by about 2%.

8. Electronic control system

Including electronic fuel injection device, electronic ignition device, anti-lock braking device, automatic transmission, etc.

Second, the characteristics of automotive electrical system

1, low voltage-gasoline vehicles mostly use 12V, and diesel vehicles mostly use 24V.

2, DC-mainly from the battery charging to consider.

3. Single-wire system-Single-wire system refers to connecting the power supply and electrical equipment with one wire, and replacing the other wire with the metal part of the car body or engine body. Single-wire system can save wires, make lines simple and clear, and facilitate installation and maintenance.

4. Negative electrode grounding-connecting the negative electrode of the battery with the car body is called negative electrode grounding.