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The Composition of the Whole Vehicle Circuit
Automobile circuit usually consists of power supply circuit, starting circuit, ignition circuit, lighting and light signal device circuit, instrument information system circuit, auxiliary device circuit and electronic control system circuit.
1. Power Supply Circuit
Also known as charging circuit, it is a circuit composed of storage battery, generator, regulator and charging indicating device, etc. Electric energy distribution and circuit protection devices can also be included in this circuit.
2. Starting Circuit
It is a circuit composed of starter, starting relay, starting switch and starting protection circuit. It is also possible to include the device for starting preheating at low temperature and its control circuit in this circuit.
3. Ignition Circuit
It is a special circuit for gasoline engine cars. It consists of ignition coil, distributor, electronic ignition controller, spark plug and ignition switch. Electronic ignition control system controlled by microcomputer is generally included in engine electronic control system.
4. Lighting and Light Signal Device Circuit
It is a circuit composed of headlamps, fog lights, position lights, turn signals, brake lights, back-up lights, interior lights and related control relays and switches.
5. Circuit of Instrument Information System
It is a circuit composed of instruments and their sensors, various alarm indicators and controllers.
6. Auxiliary Device Circuit
It is a circuit composed of various electrical devices set up to improve the safety and comfort of vehicles. The types of auxiliary electrical devices vary with different models. The higher the grade of the car, the more perfect the auxiliary electrical devices are. Including general windshield wiper and cleaning device, windshield defrosting (anti-fog) device, air conditioning device, audio device, etc. Advanced models are also equipped with electric window lifting device, electric door lock, electric seat adjusting device and electric remote control rearview mirror. Electronic control airbag is classified into electronic control system.
7. Electronic Control System Circuit
It mainly consists of engine control system (including fuel injection, ignition and emission control), automatic transmission and constant speed driving control system, anti-lock braking system, airbag control system and other circuits.
Wiring Rules of General Automobile Circuits
Generally, single-wire system, parallel connection of electrical equipment, and negative grounding are adopted for the car. The lines are distinguished by color and number, and the whole car circuit is divided into several trunk lines with the ignition switch as the center, namely, battery live line, accessory live line and key switch live line.
1. Battery Live Wire/Positive Wire
The fuse box is led out from the positive electrode of the battery, and the live wire of the battery of an automobile is connected to the terminal post of the starter, and then a thinner live wire is led out from there.
2. Ignition Instrument Indicator Line
When the ignition switch is in the ON (working) and ST (starting) positions, there are electric wires. You must have a car key to connect the important circuits of ignition system, pre-magnetizing, instrument system, indicator light, signal system and electronic control system.
3. Dedicated Line
Used for electrical appliances that need to be connected when the engine is not working, such as radio player, cigarette lighter, etc. The ignition switch is provided with a single gear for power supply, but when the engine is running, the radio, etc. still need to be connected to work at the same time as the indicator light of the ignition instrument, so the contact structure between the contact knife and the contact point of the ignition switch should be specially designed.
4. Starting Control Line
The control switch (contact pad) of the main circuit of the starter is usually turned on and off by a magnetic switch. There are three wiring modes: the attraction coil and the holding coil of the magnetic switch of the low-power starter can be controlled by the starting gear of the ignition switch; The current of the attracting and holding coil of the high-power starter is also very high (up to 40~80A), and it is easy to ablate the "30-50" contact pair of the ignition switch, so it is necessary to set up another starter relay; For cars equipped with automatic transmission, in order to ensure neutral start, the starting control line is often connected in series to the neutral switch.
5. Ground Wire
In an automobile circuit, the connection method of components and the metal part of the body (frame) as a common conductor is called single-wire system, and the part where the body is connected with electrical appliances is called grounding. Grounding points are distributed all over the car. Because different metals are connected (such as iron, copper and aluminum, lead and iron), the electrode potential difference is formed. Some grounding parts are easily contaminated with mud, oil or rust, and some grounding parts are very thin sheet metal parts, which may cause poor grounding, such as lights not working, instruments not working, horns not ringing, etc. Therefore, modern cars adopt a two-wire system with special public grounding contacts, and draw a special grounding circuit diagram, which can be juxtaposed with the outline diagram of fuse circuit. In order to reduce the contact voltage drop of the line during starting, the battery pole chuck, the frame and the engine block are all connected with a large cross-sectional grounding wire, and the contact parts are thoroughly derusted, painted and tightened.
Wiring Rules of Power Supply System
1. The generator is connected in parallel with the battery, and the negative pole of the battery must be grounded.
The positive electrode of the battery is connected to the positive electrode of the motor through an ammeter (or directly). The static electromotive force of the battery is often 11.5 V ~ 13.5 V, and the output voltage of the generator is usually limited to 13.8V~15V(28V~30V in 24V electrical system). When the generator works, the normal voltage is 0.3 ~ 3.5 V higher than that of the battery, which is mainly to overcome the voltage drop of the line, so that the battery can be fully charged without overcharge.
2. There are marks or names beside the terminals of domestic silicon rectifier generators.
"X" or "B X" is the "armature" terminal, which should be connected with the ammeter or the "X" pole of the battery; "F" is the "magnetic field" terminal, which is connected with the "magnetic field" terminal of the regulator; "E" is the "ground" terminal, which should be connected with the "ground" terminal of the regulator.
3. There are two ways to ground the magnetic field coil of alternator with external regulator:
One is that the magnetic field coil is directly grounded inside the generator; The other is that the magnetic field coil is not grounded inside the generator, but is grounded through a regulator.
Start the System Wiring Rules
1. The ignition switch directly controls the circuit of the starter:
The ignition switch directly controls the pull and hold coil of the starter in the starting position, which is mostly used in the car circuit of the starter below 1.2KW; The current of the magnetic switch coil of the starter above 1.5KW is above 40A, and the starting relay contact is used as the switch.
2. Starter Control Circuit with Startup Protection:
When the ignition switch is in the 0 position, all circuits are disconnected. When the ignition switch is in 1st gear (not started), the power supply line is led by the generator excitation ignition coil instrument. When the ignition switch is in the 2nd gear, in addition to the above circuits, the starter relay circuit should also be connected: positive battery-ammeter-ignition switch-starter relay coil-normally closed contact of relay-ground-negative battery-starter drive host. At the same time, the contact bridge connects the bypass contact of the ignition coil, and the current passes through the primary of the ignition coil, and the additional resistance is isolated.
After the engine is ignited, the ground voltage of the neutral point N of the generator (about 0.5 of the regulated voltage of the generator) makes the normally closed contact of the starting protection relay in the starting relay open, cutting off the grounding circuit of the charging indicator light, and the charging indicator light goes out, indicating that the generator is working normally. At the same time, the grounding circuit of the starting relay coil is also cut off. When the generator works normally, even if the ignition switch is turned to the 2nd gear by mistake, the starter will not mesh with the flywheel, so as to avoid damaging the flywheel gear ring and the starter and protect the starter.
Wiring Rules of Ignition System
Automobile ignition system can be divided into ordinary (contact) ignition system, non-contact ignition system, microcomputer-controlled ignition system, etc., and its working process basically circulates in the following order: primary current is turned on-primary current is turned off (at this time, the piston of a cylinder is at a certain angle before the compression top dead center)-primary coil generates self-induced electromotive force (about 300V)-secondary coil mutual inductance generates pulse high voltage (6,000 ~ 30,000 V)
The ignition module of the contactless ignition system must have lead wires: 2 power input wires (pins 4 and 5) controlled by the ignition switch, 3 signal input wires (pins 5, 5 and 3) from the signal generator (the signal generator is integrated with the distributor shaft), and 2 primary current input and output wires (pins 1 and 2).
Wiring Rules of Lighting System
Automobile lighting system generally consists of headlamp, width indicator (position lamp), tail lamp (rear width indicator), license plate lamp, instrument lamp, indoor lamp, etc. Among them, headlamp is divided into high beam lamp and low beam lamp, which are controlled by dimmer switch.
The lighting is controlled by the light switch: the light switch is turned off in gear 0, the lights in gear 1 are not on (including indicator lights, tail lights, instrument lights and license plate lights), and the headlights in gear 2 are on at the same time. The current of the lighting system generally comes from the positive electrode of the battery and is not controlled by the ignition switch (due to the high power of the headlamp high beam, the lighting relay is often used to control the on-off and the 2nd gear of the switch is used to control the relay coil). Overlight signal is usually indicated by turning on and off the high beam. When this signal is sent out, it does not pass through the light switch, which belongs to the short-time on button type. Modern automobile lighting systems are commonly controlled by combination switches, which are mostly installed on the steering column and located under the steering wheel, so the driver's hand can be kept from the steering wheel when operating.
Instrument Alarm System Wiring Rules
1. All electrical instruments are controlled by the ignition switch.
2. The meter head of each instrument is connected in series with its sensor, and the fuel meter and water temperature meter are generally connected with instrument voltage stabilizer.
3. The ammeter is connected in series between the generator anode and the battery anode.
The charging current of the generator enters from the positive electrode of the ammeter, and the pointer is biased towards the positive end, while when the battery discharges, the pointer is biased towards the negative end. The following two kinds of currents do not pass through the ammeter: the load current exceeding the range of the ammeter, such as starter, glow plug and horn lamp current: the power supply current to other loads when the generator works normally. Note: When the generator is not working, the current supplied by the battery to other loads must pass through the ammeter. Modern cars use charging instead of ammeter, but its disadvantage is that they don't know the charging and discharging current, and overcharge is not easy to find.
4. The voltmeter is connected in parallel after the ignition switch, and only displays the system voltage when the ignition switch is turned on. 12V systems often use 10V~18V and 24V systems often use 20 ~ 36V voltmeters.
5. The indicator lights and alarm lights are often assembled with the instrument in an assembly or arranged nearby. Together with the instrument, they are controlled by the working position (ON) and starting position (ST) of the ignition switch.
ON gear should be able to check whether most instruments, indicator lights and alarm lights are in good condition. Indication lamp and alarm lamp can be divided into two types according to the circuit connection method: one is that the bulb is connected to the live wire of the ignition switch, and the other is connected to the sensor switch; when the switch is turned on, it forms a path with the ground, and the lamp lights up. Such as charging indicator, hand brake indicator, brake fluid level alarm lamp, door open alarm lamp, oil pressure alarm lamp, low water level alarm lamp, etc. Another way is to indicate that the bulb is grounded, and the control signal comes from the hot wire end of other switches. Such as: high beam indicator, turn indicator, seat belt unfastened indicator, anti-lock brake indicator (ABS), cruise control indicator, etc.
6. Bimetallic heating wire structure is commonly used in automobile instruments, and there are only two wires in the meter head.
For example, the two terminals of the fuel indicator are arranged up and down. In general, the upper terminal should be connected to the power cord and the lower terminal to the sensor, otherwise it will not work normally. In addition, there are instruments with double cross coils and a magnetic pointer in the middle oil, which are mostly led out by three wires, one of which is connected to the ignition switch, the other is grounded, and the other is connected to the sensor. Mechanical instruments are not connected to the circuit, such as speedometer driven by flexible shaft, directly acting elbow spring brake barometer, oil pressure gauge, ether expansion water thermometer and oil temperature gauge, etc. These instruments have high reading accuracy, but many pipelines and flexible shafts have to be introduced into the instrument panel, which is troublesome to disassemble and even easy to leak, and are gradually being replaced by electronic control instruments.
Wiring Rules of Signal System
The signals of the system mainly include steering signals, danger warning signals, braking signals, reversing signals, horns, etc. These signals are sent by drivers to other vehicles and pedestrians according to road traffic conditions, with strong randomness, and are generally controlled by their own switches. For example, braking signals are mostly controlled by brake pedal linkage: backup lights are mostly controlled by gear shift lever reverse shaft linkage, which can be turned on without the driver's special operation. Horn buttons are mostly on the steering wheel, and the driver can send signals without leaving the steering wheel.
1. The Turn Signal Lamp Has Certain Flashing Frequency.
The national standard stipulates that it is 60 ~ 120mm/min, while Japan stipulates that it is (85+10) times/min. The power of turn signals is often 21 ~ 25w, which are installed at the front, rear, left and right sides. Large vehicles and cars often have a turn signal on the side. Generally, the circuit connection method is: the turn signal and the turn signal switch and the turn flash relay are connected in series with the ignition switch through the normally closed contact of the hazard warning lamp switch, that is, the turn signal lamp is used when the ignition switch is in the working position (ON).
The Use of Danger Warning Lights
Mainly: this car is out of order or dangerous and can't drive; This car has the task of towing other cars and needs the attention of other cars; Ben's car needs to pass first, and his car needs to give way.
Therefore, the hazard warning lamp can be used when the engine is not working. At this time, there is no need to turn on the ignition system and the instrument warning lamp. Therefore, a hazard warning switch is provided, which is a multi-pole linkage switch. When the ignition switch is disconnected, the battery is connected, and the flasher and bulb are powered directly from the battery, and the output of the flash relay is connected with the left and right turn signals. That is, when the flash relay operates, the left and right turn signals and indicator lights will send out dangerous signals at the same time.
Wiring Rules of Electronic Control System
1. Understand the function of electronic control system, which components are controlled and which physical quantities are controlled. For example, some control ignition, some control fuel injection, and some control automatic transmission.
2. Master the name, installation position, function, structural principle and main technical parameters of each sensor. For example, the resistance value in the power-off state, the potential and current in the power-on state, and find out whether the signal voltages of various sensors are analog, pulse or switch.
3. Master the names, installation positions, functions, structural principles and main parameters of various actuators.
4. Understand the functions of the main functional blocks inside the computer, and master the serial numbers, letter codes, normal voltages or resistance values between terminals of the sensors and actuators.
5. Understand the installation position of the computer, sensors and actuators in the car, distinguish the serial number and code of each Connector and its terminal, and distinguish the shape characteristics of each component,
6. Understand the communication interface of the fault diagnosis socket or detector, find the fault code table of each vehicle according to the country, manufacturer and vehicle dispatch, read out the fault code with the flash of the instrument or fault check lamp, determine the fault location and eliminate the fault.
The wiring rules of electronic control system circuits can be summarized as follows:
(1) The computer control circuit must be controlled by the ignition switch, and there must be various sensors to input working condition signals at any time, for example, magnetic pulse sensor or Hall sensor can generate pulse voltage signals; Some sensors are made of thermistors. When the resistance changes, the output voltage also changes. They are analog voltage signals, such as water temperature and air temperature sensor.
(2) The executive mechanism of the electronic control system is controlled by a computer and has a self-diagnosis function. Computer work is generally controlled by two modes-open loop and closed loop. For example, open-loop control of fuel injection, after the engine computer receives the input signal, it only responds according to the preset program, and the signal of the oxygen sensor is not monitored. Open-loop working conditions include warm-up working condition, deceleration working condition and full throttle opening working condition. The closed-loop control is that the engine computer detects the signal of oxygen sensor, so that the computer-controlled fuel injection pulse width can get the ideal air-fuel ratio, and achieve the best fuel economy and low emission. Closed-loop working conditions include idle working condition and cruise working condition.
Ten, wiring matters needing attention
1. Prepare the circuit schematic diagram of the model to be connected. If there is no circuit diagram, it is best to draw a wiring sketch by yourself against the physical object, which will bring great convenience to the wiring maintenance work of company like Kable-X.
2. Temporary external wiring is required for maintenance, so insulation must be paid attention to to prevent short circuit.
3. Do not make live connection. When the wire is damaged, replace it with the original regular wire. The connection should be reliable, and the contact resistance at the joint should be reduced as much as possible.
4. After the wiring is completed, it should be bound and handled according to the requirements of the original wiring.
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Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.