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Talk about the metal wire of the car cable harness

Blog | news | Jan 03,2023

The function of the wire harness is expanded from ordinary signal transmission to data transmission. Due to the limitations of wire transmission signals, the development of the whole vehicle is increasingly hindered. Therefore, the extensive use of optical cables will usher in the third leap in the manufacturing technology of automotive wiring harnesses. Optical cables have fast transmission speed, large capacity, small size, and confidentiality. Strong performance, good anti-interference and other advantages, will soon become an important preferred material for future automotive data processing and exchange, making the power and signal distribution system enter a new historical stage of development.

Automotive wiring harness refers to the contact terminal (connector) punched from copper, which is crimped with the wire and cable, and then molded on the outside with an insulator or a metal shell, etc., and is bundled with a wire harness to form a connected circuit assembly. Wire harnesses are widely used and can be used in automobiles, household appliances, computers and communication equipment, various electronic instruments and meters, etc.
Automotive wires, also known as low-voltage wires, are different from ordinary household wires. Ordinary household wires are copper single-core wires with a certain hardness. The automotive wires are all copper multi-core flexible wires, some of which are as thin as hair, and several or even dozens of soft copper wires are wrapped in plastic insulating tubes (polyvinyl chloride), which are soft and not easy to break.

Automotive wiring harnesses have very strict requirements on materials: including their electrical properties, material distribution, temperature resistance, etc., are higher than general wiring harness requirements, especially when it comes to safety: important components such as steering control systems and brakes The wiring harness, the requirements are more stringent. Metal materials for automotive wiring harness cables are as follows:
Copper: second only to silver in electrical conductivity, second only to gold and silver in thermal conductivity; anti-corrosion, non-magnetic, good plasticity, easy to weld, and widely used. Copper alloys are mainly used to improve the wear resistance, corrosion resistance and mechanical and physical properties of copper.
Silver: The metal has the highest electrical conductivity and thermal conductivity, has good corrosion resistance and oxidation resistance, and is easy to weld; it is mainly used for plating and cladding; it is mainly used for high temperature resistant wires and (note: according to the principle of skin effect) Do high-frequency communication cable conductors.
Aluminum: The electrical conductivity is second only to silver, copper, and gold; it has good thermal conductivity, good corrosion resistance, average mechanical strength, good plasticity, and small specific gravity. The disadvantage is that the tensile strength is low and it is not easy to weld. Aluminum alloy is mainly to improve the mechanical strength, heat resistance and weldability of aluminum.
Gold, nickel: used as high temperature resistant wire.
Iron (steel): It is often used as a reinforcing material for composite conductors, such as steel-cored aluminum stranded wire, copper-clad steel, aluminum-clad steel wire, etc.
Zinc: Used as a coating for steel wire/strip/iron conductors to prevent corrosion.
Tin: It is used as a coating for steel wire/copper wire to prevent corrosion and facilitate the welding of copper wire.
Types, specifications and standards of automotive wiring harness cables
Automotive wiring harness cables have great applications in automobiles. What kind of wire type to choose for the automotive wiring harness cable plays an important role in the performance of the automotive wiring harness. To design a good wire harness, there is no room for sloppy selection of wire types. Wires can be divided into electronic wires and cable wires according to their properties: electronic wires include unshielded wires and shielded wires (UL1571 wires will have shielded wires, and other electronic wires are generally unshielded wires); cable wires also include unshielded wires and shielded wires. Shielded wires, such as UL2464, can be divided into these two types. According to the standards: UL/CSA (safety line), CCC (national standard line), VDE (German standard line), PSE (Japanese standard line), etc., among which UL/CSA, VDE, CCC are relatively common lines, currently used Most of them are UL/CSA lines.

The commonly used specifications of the wires in the automobile wiring harness are wires with a nominal cross-sectional area of 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 4.0, 6.0 and other square millimeters. Each of them has a allowable load current value and is used for different power electrical equipment of wires. Taking the vehicle wiring harness as an example, the 0.5 gauge line is suitable for instrument lights, indicator lights, door lights, dome lights, etc.; the 0.75 gauge line is suitable for license plate lights, front and rear small lights, brake lights, etc.; Lights, etc.; 1.5 gauge wires are suitable for headlights, horns, etc.; main power lines such as generator armature wires, ground wires, etc. require 2.5~4mm2 wires. This only refers to the general car, the key depends on the maximum current value of the load, for example, the ground wire of the battery and the positive power wire are used separately for special automobile wires, and their wire diameters are relatively large, at least a dozen square millimeters Above, these “big mac” wires will not be woven into the main wiring harness.
The types of wires commonly used in automotive wiring harnesses include Japanese standard (AVSS, etc.), national standard (QVR), German standard (FLRY), American standard and other major series. AVSS wire is characterized by thin insulation and good flexibility; QVR is characterized by thick insulation, relatively soft, and good ductility; German standard wire insulation is thinner and has good flexibility; American standard wire insulation is generally thermoplastic or thermosetting Elastomers, as well as those processed by irradiation. The appropriate type of wire can be selected according to the needs of users and different working environments. The wires commonly used in automotive wiring harnesses usually use stranded copper wires, and the insulation is PVC insulation.
Wire harness wires should have characteristics such as temperature resistance, oil resistance, wear resistance, waterproof, corrosion resistance, oxidation resistance, and flame retardancy. The wires selected for the automotive wiring harness should fully consider the environment and function of the wiring harness. For example: the ambient temperature around the engine is high, and there are many corrosive gases and liquids. Therefore, it is necessary to use high-temperature resistant, oil-resistant, vibration-resistant, and friction-resistant wires; the wires on the trunk lid must maintain their elasticity at low temperatures, so cold elastic wires must be used to ensure their normal operation; the wires on the automatic transmission must be resistant High temperature and hydraulic oil resistance, the temperature stability is better; weak signal sensors should use shielded wires, such as knock sensors, crankshaft position sensors, ABS wheel speed sensors, etc.; the door inner wires require high bending resistance.
Technical Requirements for the Cross-section of Automobile Low-Voltage Electric Wire Harness
Automotive wiring harness is one of the products with the fastest development, the largest market demand and easy installation in the industry in today’s electronic and information age. The interior of the car is equipped with complete functions, but the electrical circuits hidden inside the car body are complicated and large in size, making it difficult to replace them. The reliability of the wiring harness is a key component that affects the performance of the vehicle, and the quality control of the wiring harness is very necessary. The requirements of the national standard for the cross-sectional analysis technology of low-voltage wire harnesses for automobiles and the cross-sectional analysis technology for crimped connection terminals are as follows:
The size of the wire harness should meet the following requirements: the length of the main line and the protective sleeve should not be less than 100mm, and the riveting section should be a multiple of 10. Such as: 100mm, 110mm, 120mm; the length of the branch line of the terminal slice analysis system should not be less than 30mm; the distance between the contact point and the branch point should not be less than 20mm; the connection between the wire and the terminal When it is necessary to install an insulating sleeve, the length of the insulating sleeve shall not be less than 20mm.

The connection between the terminal and the wire should preferably adopt the crimping method. The connection should meet the following requirements: the terminal should be pressed tightly on the conductor and the insulation layer respectively, the conductor should not be broken, and the insulation should not be broken. The layer should not be pressed into the crimping part of the conductor, and the wire conductor should be visible, but it should not hinder the insertion. The cross-section analysis of the crimping terminal of the automobile wiring harness after no less than 3 cycles of bending test on the crimping part of the insulating layer. The cross-section of the terminal and the wire crimping place using the crimping method shall meet the requirements of the specification for the connector metallographic analysis system.

Terminal and conductor crimping and cross-sectional inspection of crimping joints should be carried out according to the following methods , Take one side as a sample, its cross-section should be ground flat, and chemically etched until it can be inspected.

According to relevant national technical regulations, wires of different circuits, wires of different voltages, different AC wires and DC wires cannot be worn in the same protective tube. Because the purpose and specifications of different lines are different, the power load is also different. If they are worn together, the larger power load will interfere with and damage the lower power line. If the power line is blown, it will cause a short circuit, sparks, and cause a fire. . Weak current signal lines cannot go together with strong current, because the electromagnetic field generated by strong current will affect the signal of weak current, affecting communication and video effects. The cross-sectional area of the lighting wire and the socket wire is different, and the load power is even more inconsistent. Frequent use of the socket wire will cause electric shock, short circuit and other phenomena. Therefore, wires with different purposes and functions must not be worn in the same protective tube.

Before arranging the wiring harness, it is necessary to draw a wiring harness diagram in advance. The wiring harness diagram is different from the circuit schematic diagram. The circuit schematic diagram is an image that expresses the relationship between various electrical parts. It does not reflect how the electrical parts are connected to each other, and is not affected by the size and shape of each electrical component and the distance between them. The wiring harness diagram must take into account the size and shape of each electrical component and the distance between them, and also reflect how the electrical components are connected to each other. After the wiring harness factory makes the wiring harness board according to the wiring harness diagram, it will cut and arrange the wires according to the regulations of the wiring board.

The main wiring harness of the whole vehicle is generally divided into engine (ignition, EFI, power generation, starting), instrumentation, lighting, air conditioning, auxiliary electrical appliances and other parts, with main wiring harness and branch wiring harness. A vehicle main wiring harness has multiple branch wiring harnesses, just like tree trunks and tree branches. The main wiring harness of the whole vehicle often takes the instrument panel as the core part and extends forward and backward. Due to the length relationship or the convenience of assembly, the wiring harness of some cars is divided into the front wiring harness (including instrument, engine, headlight assembly, air conditioner, battery), rear wiring harness (taillight assembly, license plate light, trunk light), roof Wiring harness (door, dome light, audio horn), etc.

Each end of the wire harness will be marked with numbers and letters to indicate the connection object of the wire. The operator can see that the mark can be correctly connected to the corresponding wire and electrical device, which is especially useful when replacing the wire harness. At the same time, the color of the wire is divided into single-color wire and double-color wire, and the use of the color is also regulated, which is generally the standard set by the car factory. my country’s industry standards only stipulate the main color, for example, it is stipulated that the single black color is used exclusively for the ground wire, and the red single color is used for the power line, which cannot be confused. The wiring harness is wrapped with woven wire or plastic adhesive tape. For safety, processing and maintenance convenience, woven wire wrap has been eliminated, and now it is wrapped with adhesive plastic tape.

The wiring harness is wrapped with woven wire or plastic adhesive tape. For safety, processing and maintenance convenience, woven wire wrap has been eliminated, and now it is wrapped with adhesive plastic tape. The connection between the wire harness and the wire harness, between the wire harness and the electrical parts, adopts connectors or wire lugs. Connecting plug-in unit is made of plastics, and is divided into plug and socket. The wiring harness and the wiring harness are connected with a connector, and the connection between the wiring harness and the electrical parts is connected with a connector or a wire lug. With the increase of automobile functions and the widespread application of electronic control technology, there will be more and more electrical components, more and more wires, and the wiring harness will become thicker and heavier. Therefore, advanced automobiles have introduced the CAN bus configuration and adopted a multiplex transmission system.
Compared with the traditional wiring harness, the multiplex transmission device greatly reduces the number of wires and connectors, making wiring easier.

The conductor of the automobile wire is made of many copper wires twisted, and the twisted conductor has good bending and flexibility. The copper wire of the stranded conductor is drawn by a wire drawing machine to draw a very thick copper rod through multiple drawing. The size of the copper wire is about 0.1~0.4mm, which is about the thickness of a hair. The traditional wire drawing machine can only draw one copper wire at a time. The copper wire drawn by the single-head wire drawing machine is drawn by different equipment at different times, and the process conditions are very different. The mold, lubrication, drawing It is difficult to keep consistent various process parameters such as force, tempering temperature and time. Such copper wires are put together, and their size, material, metallographic structure, mechanical elastic modulus, and ultimate elongation at break are all very different. The current advanced wire drawing machine is a multi-head wire drawing machine with continuous annealing, which can draw a bundle of copper wires at a time, and there are more than a dozen copper wires in this bundle. This kind of wire drawing machine occupies less land, has high production efficiency, remarkable energy saving, less labor force and low labor intensity. The multi-head wire drawing technology is widely used by foreign automobile wire manufacturers, mainly because it ensures the high quality of automobile wires.

Automotive wiring harness materials generally use copper core polyvinyl chloride (QVR), copper core polyvinyl chloride – nitrile compound insulated low-voltage wire (QFR), and copper core heat-resistant 105 ℃ polyvinyl chloride (OVR-105) is used in Electrical appliances and instrument lines in the high temperature area of the vehicle. Delphi, a world-renowned auto parts company, has developed a recyclable Halogen Free (Halogen Free) wire harness material, which is a major breakthrough in the development of power wire technology in the past 30 years. The halogen-free wiring harness coating adopts “flexible Noryl resin” from GE Advanced Materials Company of the United States. Flexible Noryl resin is halogen-free, chlorine-free and lead-free, with a maximum operating temperature of 110°C, excellent temperature characteristics and flame retardancy. What’s more, this material is very environmentally friendly and recyclable.

Harness Color: Bus wiring harnesses are intricate. In order to facilitate wiring and repair, the wire ends should be visually distinguished, and the wires of the same diameter in the same bundle should be distinguished in color as much as possible. The color of the wiring harness can be divided into single color or double color: the double color is composed of the main color and the auxiliary color, and the auxiliary color is two axial straight bars, which are distributed in symmetrical positions. RG); the color and code of the single-color logo are red R, orange O, yellow Y, green G, brown N, blue U, purple P, black B, white W, and gray S.

As the main carrier of power transmission, wire and cable should pay attention to the following points when purchasing automotive wiring harness cables: When purchasing wire and cable products, you should observe the product certificate for product model, specification, rated voltage, number of cores, production date, implementation standards, Whether the relevant information such as the license number is fully marked, the physical surface of the product should be printed with the continuity mark of the factory name, product model and rated voltage, and verify whether the relevant information is consistent. The outer plastic skin of the wire is bright in color and fine in texture, whether there are burrs or protrusions on the surface, whether the appearance is smooth, round, and uniform in color. The conductor uses electrolytic copper, and the outer layer is bright and slightly soft. Look at the section of the cable again, the copper (aluminum) core should be in the middle, and the thickness of the plastic layer should be uniform. There is a length mark on the certificate of conformity. You can first estimate the length of a coil of the finished product package, and then count the number of coils on the coil to estimate the approximate length of the entire coil. In addition, pay attention to the diameter of the conductor. length and section. When choosing wire and cable products, it is best to consult an experienced professional electrician, and use cables with appropriate cross-sectional size and voltage level according to your own electrical load.

To sum up, with the increase of automobile functions and the widespread application of electronic control technology, there will be more and more electrical components, more and more wires, and the wiring harness will become thicker and heavier. Hyundai has introduced the CAN bus configuration, using a multiplex transmission system. Compared with the traditional wiring harness, the multiplex transmission device greatly reduces the number of wires and connectors, making wiring easier.

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