The composition, principle and characteristics of the car

First, the main components of automotive electrical appliances

1. Power system

Including batteries, generators, regulators. The generator is the main power source. When the generator is working normally, the generator supplies power to the whole vehicle electrical equipment, and at the same time, the battery is charged. 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 in automobiles is the starting lead storage battery, which is connected in parallel with the engine to supply power to the consumer. The function of the battery is to supply power to the starter and ignition system when the engine is started;

When the power is not generated or the voltage is low, the power is supplied to the power equipment; when the power equipment is connected at the same time, the generator is overloaded to assist the generator to supply power; when the battery is insufficient, and the generator load is less, It converts the electrical energy of the generator into chemical energy

Save it. Therefore it occupies an important position in the car. How to properly use and maintain the battery is extremely important to extend the life of the battery. Therefore, auto repair shops are responsible for maintenance, repair and activation of new batteries.

The generator is the main power source of the electric vehicle system. During normal operation, it supplies power to all the electric equipment except the starter and charges the battery to supplement the electric energy consumed by the battery during use.

Generators used in automobiles include DC generators and alternators. The DC generator is rectified by a mechanical commutator, and the alternator is rectified by a silicon diode, so it is also called a silicon rectifier generator.

Automotive electrical appliances are designed according to a certain DC voltage. Gasoline engines are commonly used for 12V, and diesel engines are commonly used for 24V. In a car, the generator is both a power source for the appliance and a charging device for the battery. In order to meet the requirements of electrical appliances and batteries for generators

There are also limits to the range of supply voltage and current variations.

The regulators matched by the DC generator are generally composed of a voltage regulator, a current limiter, and a cut-off relay. The alternator regulator can be greatly simplified. Due to the unidirectional conductivity of silicon diodes, when the generator voltage is higher than

When the cell is moving, the diode has a function to prevent reverse current, so the alternator no longer needs a shut-off relay.

Since the alternator has the ability to limit the output current, the current limiter is no longer needed. However, its voltage still varies with the speed of rotation, so in order to obtain a constant DC voltage, it is necessary to install a voltage demodulator.

2. Start system

Including series-excited DC motors, transmissions, and control devices. Its role is to start the engine.

The starter is used to start the engine. It is mainly composed of a motor part, a transmission mechanism (or an engagement mechanism) and a starter switch.

3. Ignition system

It includes an ignition switch, an ignition coil, a distributor assembly, a spark plug, etc., and its function is to generate a high-voltage electric spark to ignite the mixture in the cylinder of the gasoline engine.

In modern gasoline engines, the mixture of fuel and air in the cylinder is mostly ignited by high voltage electric spark. Electric spark ignition has the advantages of rapid spark formation, accurate ignition timing, easy adjustment, and ignition of the mixture.

In order to generate a high voltage spark in the cylinder, a special ignition device must be used.

The ignition device can be divided into two categories: battery ignition and magnetoelectric ignition according to different sources of electric energy.

4. Lighting system

Including various lights inside and outside the car and its control devices. Used to ensure safe driving at night. There are mainly headlights, fog lights, tail lights, brake lights, shed lights, electric horns, turn signal flashers and so on.

5. signal system

Including speakers, buzzers, flashers and various driving signal identification lights. It is used to ensure the safety of people and vehicles when the vehicle is running.

6. Instrumentation system

Including various electrical instruments (current meter, charging indicator or voltmeter, oil pressure gauge, thermometer, fuel gauge, speed and odometer, engine tachometer, etc.). It is used to show the working condition of the relevant equipment in the engine and the car.

The role of the car instrument is to help the driver to keep abreast of the working conditions of the main part of the car, to detect and eliminate possible faults and unsafe factors in time to ensure a good state of exercise. The car commonly used meters have ammeter, water temperature gauge, engine oil pressure

Force gauges, fuel gauges and speedometers, and some cars also have engine tachometers and brake system air cylinder pressure gauges.

1 ammeter

The ammeter is connected in series in the charging circuit and is used to indicate the state of charge and power generation of the battery. It can be divided into electromagnetic type, moving magnetic type and photoelectric indicator type according to the structure. The most commonly used is an 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 the engine lubrication system is working properly. It consists of a hydraulic indicator on the instrument panel and a sensor mounted in the main oil gallery of the engine or on the coarse filter.

3 water temperature gauge

The water temperature gauge can be used to indicate whether the operating temperature of the cooling water in the engine water pump is normal. It consists of a water temperature indicator mounted on the instrument panel and a water temperature sensor (commonly known as the greenhouse) mounted on the engine cylinder head water pump. Commonly used

The water temperature indicator is a two-metal electromagnetic type, and the sensor has two types of 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 a fuel indicator on the instrument panel and a sensor mounted in the fuel tank. The fuel indicator is available in both electromagnetic and bimetallic versions, and the sensors are variable resistors.

5 speed odometer

The speedometer is a meter used to indicate the speed of the car and the accumulated mileage of the car. It consists of a speedometer and an odometer.

7. Auxiliary electrical system

Including electric wipers, air conditioners, low temperature start preheaters, tape recorders, cigarette lighters, glass lifts, etc.

With the development of the automotive auxiliary industry and the application of modern technology in the automotive industry, there are many auxiliary electrical equipment for modern automobile installations. Apart from the automotive audio equipment, communication equipment and car TV and other service devices, some of them are used with the car itself.

Related electrical equipment. Such as electric wipers, electric window washers, electric glass lifts, heater ventilation, electric seat moving mechanism, engine cooling, electric fan, electric fuel pump, electromagnetic clutch for cold air compressor, etc. These auxiliary electrical installations

The equipment can be divided into three categories: motors, electromagnetics and electric pumps.

1 two-speed electric wiper

Two-speed electric wipers are generally composed of a DC-excited (or re-excited) motor and a set of reduction gearing mechanisms.

2 windshield anti-icing equipment

It is easy to freeze on the winter window glass. It cannot be removed with a wiper. The effective way is to heat the glass. In a car with an air conditioner, blowing hot air to the windshield can avoid freezing.

In a car without air conditioning, the windshield can be heated by a resistance wire, and three nickel-chromium wires are attached to the inner surface of the windshield, and the frost can be prevented by heating. The power consumption of the device is 30-50W. good results. Some foreign luxury cars use electronic

The heater is electrically heated by the control of the three-stage tube.

3 glow plug

In winter, due to the low temperature of the air entering the diesel engine, the compressed mixed air does not reach the temperature of the fire, so starting is difficult. In order to make the diesel engine easy to start in winter, a glow plug is installed in the diesel engine combustion chamber to increase the air temperature in the cylinder.

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4 transistor electric gasoline pump

The diaphragm type petrol pump generally used in automobiles has a simple structure and high performance. However, since it is installed on the engine body, in summer, because of the high engine temperature, the oil supply system generates a "air resistance" phenomenon, so that the gasoline is not circulated. Chang, in recent years due to the development of semiconductors

For the exhibition and application, an electric gasoline pump has been installed on the car to replace the diaphragm type gasoline pump.

5 electromagnetic clutch

The electromagnetic clutch is a common automatic control component, which has the characteristics of work* and easy remote control. In automobiles, it is often used as a cold air compressor drive clutch and an engine cooling fan clutch. Cooling capacity in automotive air conditioning systems

When there is excess, it will disengage the drive pulley from the compressor main shaft; when the car engine radiator has excess cooling capacity, it can make the fan slip to reduce the engine's power consumption. In the low temperature season, only the fan clutch One can reduce

The fuel consumption rate of a car is about 2%.

8. Electronic control system

Including electronically controlled fuel injection devices, electronic ignition devices, anti-lock brakes, automatic transmissions, etc.

Second, the characteristics of automotive electrical systems

1. Low pressure - 12V for gasoline vehicles and 24V for diesel vehicles.

2, DC - mainly from the charge of the battery to consider.

3. Single-wire system—The single-wire system uses one wire connection from the power supply to the electrical equipment, while the other wire is replaced by the metal part of the car body or the engine body. The single-wire system saves wires, making the circuit simple, clear, and easy to install and overhaul.

4, the negative grounding - the negative pole of the battery is connected with the car body, called the negative ground.