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In modern cars, electronic control systems and wire harnesses are closely related. If the computer, the sensor and the implementation of the function of the components with the human metaphor, it can be said that the computer is equivalent to the human brain, the sensor is equivalent to the sensory organs, the implementation of components equivalent to the movement tube. Obviously, only the mind and various organs, no nerves and blood vessels, the body's hand and foot will not be able to play the proper function.
The electrical harness that connects the electrical and electronic components of a car and makes it function is the role of "nerves and blood vessels" in the car. The wiring harness is composed of electric wires that make up the circuit. It is necessary to ensure the transmission of electrical signals, but also to ensure the reliability of the connection circuit, to supply electrical and electronic components with a specified current value, to prevent electromagnetic interference to the surrounding circuit, and to exclude electrical short circuit.
The wiring harness of the car is divided by a function line, a signal line for transmitting a sensor input command, and a power line carrying a driving actuator (actuator). The signal line is a fine wire that does not carry electricity (optical fiber communication), and the power line is a thick wire that carries high current. For example, the cross-sectional area of the conductor circuit for the signal circuit is 0.3, 0.5mm2; in the motor, the conductor cross-sectional area of the actuator is 0.85,1.25mm2, and the power supply circuit has a cross-sectional area of 2,3,5mm2; and the special circuit , Alternator, engine ground wire, etc.) are 8,10,15,20 mm2 different specifications. The larger the cross-sectional area of the wire, the greater the current capacity. The choice of wire, in addition to considering the electrical performance, but also by the physical performance of the vehicle when the constraints, so its wide range of options. For example, the frequent opening / closing of the car on the car and across the body between the wires should be composed of good bending performance of the wire. In the high temperature parts of the use of wire, generally use the insulation and good heat resistance of vinyl chloride, polyethylene coated wire. In recent years, weak signal circuit using electromagnetic shielding lines are also increasing.

In addition, the connection harness and electronic, electrical components, circuit important parts - connectors in recent years have also been improved. For example, the use of resistance welding manufacturing of automotive connectors and new wiring harness material successfully applied to the roof module (roof module).
With the modern car safety, comfort and environmental protection requirements continue to improve, the number of cars on the circuit and electricity consumption increased significantly, so that a large number of wiring harness in a limited car space, how effective and reasonable layout has become the automotive industry is facing problem. This paper focuses on the automotive wiring harness and introduces the present situation and future development of vehicle communication technology.
Development of Automobile Harness
Automotive wiring harness in order to adapt to the high functionality of the vehicle and the diversification of user needs, in the vehicle space gradually expanded. In fact, in order to improve the fuel economy and reduce the weight of the car, the wire itself from the original AV line continue to reduce the diameter, after AVS line to AVSS line. The diameter of the harness is decreasing. And in recent years the use of multi-channel transmission technology (car LAN (LAN)) makes the number of circuits greatly reduced. Figure 1 shows the 1800 ~ 2000mL displacement of the number of passengers on the passenger car and the maximum diameter of the wire harness change process. But from the development trend of the wiring harness, the number of its car is still increasing, and in the limousine on the number of circuits even more than 2000.
One of the effective ways to reduce the weight of the harness is the supply voltage of 42V. From the electric power steering (EPS) or electric air conditioning devices and other requirements of large power load, because no increase in current conditions (wire cross-sectional area does not increase) may increase the power supply, it is considered an effective method. On the other hand, as the power supply voltage rises, there are safety problems such as electromagnetic noise or leakage, and a shielded wire or waterproof connector has to be taken, and the weight of the harness is increased. Therefore, with the popularity of automotive LAN applications, requiring the use of electromagnetic interference with high shielding characteristics of the wire material.

In the multi-channel communication function, in the development situation, the communication protocol is developed to the higher speed and the high reliability because of the increase in the traffic and the expansion of the application of the security function and the acquisition of the multimedia information. It is expected that in the future, network technology will be further applied not only in the vehicle, but also between roads and vehicles, between vehicles and vehicles. Conductor as the vehicle's internal communication medium, will be high-speed, anti-electromagnetic interference and to "photochemical" (that is, the use of light guide technology development direction) changes.
High voltage of the wiring harness (42V)
Due to the high voltage of the wiring harness power supply voltage, the current consumption is reduced and the diameter of the electric wire is reduced. Therefore, it is possible to reduce the wiring harness and improve the assembling convenience of the wiring harness in the vehicle. However, the power supply voltage from the existing 14V to 42V, about 2 times higher, it will produce a lot of problems must be solved.
● Leakage
● Short circuit
● Electrification
● Electromagnetic noise
● Arc discharge
One of the most important and most difficult to solve is the arc discharge. Arc discharge refers to the discharge, when the contact or terminal separation occurs when the discharge phenomenon. In the 42V occasion, then called the stability of the arc will occur. This arc and 14V power supply voltage compared to the long duration, the discharge energy is also very large. The center temperature of the arc is as high as several thousand degrees, which is a very dangerous phenomenon.
In particular, when the connector is pulled out of the arc discharge, due to direct contact with the user, so take the appropriate protection measures as soon as possible. The following describes how to protect the plug from the arc discharge.
● Take the optimized terminal material
• Effective dispersion of the terminal's double-contact arc discharge energy
• Improve the connector housing to increase the pull-out speed of the connector
● Eliminate arc discharge with magnets
Implementation of the 42V electrical system will start from a dual voltage (14V, 42V) system and gradually transition to a single 42V electrical system. How long does it take to complete a 14V to 42V change, depending on the development of automotive electronics and consumer endurance.
Current Situation and Development Trend of Communication Protocol in Local Area Network (LAN)
With the widespread use of electronic technology in the car, resulting in a large and complex body wiring. According to statistics, a traditional wiring method of high-class cars, the wire length of up to 2km, electrical contacts up to 1500, and thus the automotive network technology came into being, as a direction for the development of automotive technology.
For a long time, multi-channel communication technology has been seen as a way to solve the increasing use of automotive wiring harness. The world's major automobile manufacturers have developed special standards. However, multi-channel communication technology is expensive only for high-class cars. In recent years, the automotive electronic system is increasing, the data transmission speed is insufficient, and the small economy car also requires the development to the high function direction, together with the harness increasing, the formation of "hypertrophy", therefore, as the background, since 2000 Year, in the foreign car began to use the controller local area network (CAN) standard communication protocol.
Now, the most widely used communication protocol is high-speed CAN, the most important local area network used in power transmission system and parts of the body line communication. Controller Local Area Network (CAN) is characterized by the event trigger, CSMA / CA mode (if the bus is no load, all electronic control units can send a signal, and when the signal conflict, let the high priority signal first Issued, and then issued by other signals). When the amount of online information increases, it is difficult to ensure that response time and predictability. In the modern limousine with more than 70 electronic control unit, the amount of information on the network there is an increasing trend, so the network to be divided in each body or powertrain lines are equipped with only the necessary data through the network The gateway is forwarded (two communication protocols are applied in the vehicle).