Lets talk about the metal wires used in automotive cable harnesses

Metal materials used for automotive wiring harness cables

Automotive wiring harnesses refer to components formed by crimping copper contact terminals (connectors) with wires and cables, and then plasticizing insulators or adding metal shells on the outside to bind the wiring harnesses and connect circuits. Wire harnesses have a wide range of applications and can be used in automobiles, household appliances, computers and communication equipment, various electronic instruments and meters, etc.

Automobile wires, also known as low-voltage wires, are different from ordinary household wires. Ordinary household wires are single-core copper wires with a certain degree of hardness. Car wires are all copper multi-core flexible wires. Some of these flexible wires are as thin as hair. Several or even dozens of soft copper wires are wrapped in plastic insulating tubes (polyvinyl chloride), which are soft and not easy to break.

The requirements for materials of automotive wiring harnesses are extremely strict: including their electrical performance, material dissipation, temperature resistance, etc., all of which are higher than those of general wiring harnesses. Especially for those related to safety, such as the wiring harnesses of important components like the steering control system and brakes, the requirements are even more stringent. The metal materials used in automotive wiring harness cables include the following types:

Copper: Its electrical conductivity is second only to silver, and its thermal conductivity is second only to gold and silver. Corrosion-resistant, non-magnetic, good plasticity, easy to weld, and widely used. Copper alloys are mainly used to enhance the wear resistance, corrosion resistance and mechanical and physical properties of copper.

Silver: It has the highest electrical and thermal conductivity among metals, excellent corrosion resistance and oxidation resistance, and is easy to weld. Mainly used for coatings and coating layers; It is mainly used as a high-temperature resistant wire and (Note: According to the skin effect principle) as a conductor for high-frequency communication cables.

Aluminum: Its electrical conductivity is second only to that of silver, copper and gold. It has good thermal conductivity, excellent corrosion resistance, average mechanical strength, good plasticity and low specific gravity. The disadvantage is that it has a low tensile strength and is not easy to weld. Aluminum alloys are mainly used to enhance the mechanical strength, heat resistance and weldability of aluminum.

Gold and nickel: used as high-temperature resistant wires.

Iron (steel) : It is often used as a reinforcing material for composite conductors, such as steel-cored aluminum stranded wire, copper-clad steel, and aluminum-clad steel wire, etc.

Zinc: It is used as a coating for steel wire/steel 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 cable materials

Automotive wiring harness cables have a wide range of applications in automobiles. The type of wire chosen for automotive wiring harness cables plays a crucial role in the performance of the automotive wiring harness. To design a good wiring harness, there can be no room for the slightest carelessness in the selection of wire types. Wires can be classified into electronic wires and cable wires based on their nature: Electronic wires include unshielded wires and shielded wires (UL1571 type wires will have shielded wires, while other electronic wires are generally unshielded wires). Cables also include unshielded wires and shielded wires, such as UL2464, which can be divided into these two types. According to the standards, they can be classified as UL/CSA(safety standard line), CCC(national standard line),VDE (German standard line), PSE(Japanese standard line), etc. Among them, UL/CSA,VDE, and CCC are the most commonly seen lines. Currently, UL/CSA lines are the most widely used.

The common specifications of wires in automotive wiring harnesses include those with nominal cross-sectional areas 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 an allowable load current value and is used as a wire for electrical equipment of different powers. Take the vehicle wiring harness as an example. 0.5 specification wires are suitable for instrument lights, indicator lights, door lights, ceiling lights, etc. The 0.75 specification line is suitable for license plate lights, front and rear small lights, brake lights, etc. 1.0 specification line is suitable for turn signals, fog lamps, etc. 1.5 specification wires are suitable for headlights, speakers, etc. The main power lines, such as the generator armature line and grounding line, require 2.5 to 4mm ² wires. This only refers to ordinary cars. The key lies in the maximum current value of the load. For instance, the grounding wire of the battery and the positive power line are dedicated automotive wires used separately. Their wire diameters are relatively large, at least tens of square millimeters or more. These "giant" wires are not included in the main wire bundle.

The commonly used types of wires in automotive wiring harnesses include several major series such as Japanese standard (AVSS, etc.), Chinese standard (QVR), German standard (FLRY), and American standard. The characteristics of AVSS conductors are thin insulation and good flexibility. The characteristics of QVR are thick insulating skin, relatively soft and good ductility. The insulation of German standard wires is thinner and more flexible. The insulation of American standard conductors is generally made of thermoplastic or thermosetting elastomer, and there are also those processed by irradiation technology. Appropriate types of wires can be selected according to the user's requirements and different working environments. The commonly used wires in automotive wiring harnesses usually employ multi-strand stranded copper wires, with PVC insulation material as the insulating sheath.

The wires used for wiring harness should have properties such as heat resistance, oil resistance, wear resistance, water resistance, corrosion resistance, oxidation resistance and flame retardancy. The wires selected for automotive wiring harnesses should fully take into account the environment and function of the wiring harnesses. For instance, the ambient temperature around the engine is high, and there are also many corrosive gases and liquids. Therefore, it is essential to use high-temperature resistant, oil-resistant, vibration-resistant and friction-resistant wires. The wires on the luggage compartment lid need to maintain their elasticity at low temperatures, so cold-elastic wires should be selected to ensure their normal operation. The wires on the automatic transmission must be resistant to high temperatures and hydraulic oil, and have good temperature stability. Weak signal sensors should use shielded wires, such as knock sensors, crankshaft position sensors, ABS wheel speed sensors, etc. The inner line of the door has high requirements for bending resistance.

Technical requirements for the cross-section of automotive low-voltage wiring harnesses

Automotive wiring harnesses are one of the products that are developing rapidly, have the largest market demand and are easy to install in the current electronic and information age industry. The interior configuration of the vehicle is fully functional, but the electrical circuits hidden inside the body are complex, large in size and not easy to replace. The reliability of the wiring harness is a key component that affects the overall performance of the vehicle, and the quality control of the wiring harness is extremely necessary. The requirements of the national standard for the cross-sectional analysis technology of automotive low-voltage wiring harnesses and the cross-sectional analysis technology of crimped connection terminals are as follows:

The dimensions of the wire harness should comply with the following requirements: F-type crimped terminal profile analyzer: The length of the main line and protective bushing should be no less than 100mm and be a multiple of 10. Riveted profile computer analyzer. For example: 100mm, 110mm, 120mm; The branch line length of the terminal slicing analysis system should be no less than 30mm. For the cross-sectional metallographic analysis instrument of automotive low-voltage wiring harnesses between contacts, the distance between the contacts and the branch points should be no less than 20mm. When insulating sleeves need to be installed at the connection between wires and terminals, the length of the insulating sleeves shall not be less than 20mm.

The connection between terminals and wires should preferentially adopt the crimping method. The connection should meet the following requirements: Terminals should be respectively crimped onto the conductor and the insulation layer. The conductor should not be broken, and the insulation layer should not be pressed into the crimping part of the conductor. The wire conductor should be visible, but it should not hinder the insertion. Analysis of the cross-sectional area of the crimped terminal of the automotive wiring harness after no less than three cycles of bending tests at the crimped part of the insulation layer. The cross-section of the crimping point between the terminal and the wire by crimping method should comply with the requirements of the specification for the connector metallographic analysis system.

The terminal crimping with the conductor and the cross-sectional inspection of the crimping contact points should be carried out in accordance with the following method: Sample preparation for the wire harness terminal testing equipment: After cutting the sample to be inspected (avoiding the reinforcing ribs of the terminal), take one side as the sample. Its cross-section should be ground flat and chemically corroded until it can be tested.

According to relevant national technical standards, wires of different circuits, wires of different voltages, and different AC and DC wires cannot be run through the same conduit. Due to the different uses and specifications of various circuits, their electrical loads also vary. If they are strung together, the circuit with a larger electrical load will interfere with and damage the one with a smaller electrical charge. In case the power line melts, it will cause a short circuit, generate sparks, and lead to a fire. Weak current signal lines must not run together with strong current. This is because the electromagnetic fields generated by strong current can affect the signals of weak current, influencing communication and video effects. The cross-sectional areas of lighting wires and socket wires are not uniform, and their load capacities are also inconsistent. Socket wires are frequently used repeatedly, which can cause electric shock, short circuits and other phenomena. Therefore, wires of different uses and functions must never be run through the same conduit.

Arrangement and processing of wire materials for automotive wiring harness cables

Before arranging the wiring harness, a wiring harness diagram should be drawn in advance. A wiring harness diagram is different from a circuit schematic diagram. A circuit schematic diagram is an image that depicts the relationships among various electrical components. It does not reflect how electrical parts are connected to each other and is not affected by the size, shape of each electrical element or the distance between them. The wiring harness diagram must take into account the size and shape of each electrical component and the distances between them, and also reflect how the electrical components are connected to each other. After the wiring harness factory makes the wiring harness layout board according to the wiring harness diagram, it then cuts and arranges the wires in accordance with the regulations of the layout board.

The main wiring harness of a complete vehicle is generally divided into parts such as the engine (ignition, electronic fuel injection, power generation, starting), instrument panel, lighting, air conditioning, and auxiliary electrical appliances, and there are main wiring harnesses and branch wiring harnesses. A main line harness of a complete vehicle has multiple branch harnesses, just like the trunk and branches of a tree. The main line bundle of the entire vehicle often takes the dashboard as the core part and extends forward and backward. Due to reasons such as length or ease of assembly, some car wiring harnesses are divided into front-end wiring harnesses (including instrument panels, engines, headlight assemblies, air conditioning, and batteries), rear-end wiring harnesses (taillight assemblies, license plate lights, and trunk lights), and roof wiring harnesses (doors, roof lights, and audio speakers), etc.

Each end of the wiring harness is marked with numbers and letters to indicate the connection objects of the wires. When the operator sees the marks, they can correctly connect to the corresponding wires and electrical devices. This is particularly useful when replacing the wiring harness. Meanwhile, the colors of wires are divided into single-color wires and two-color wires, and there are also regulations on the uses of the colors, which are generally the standards set by the car manufacturers themselves. China's industry standards only stipulate the main colors. For instance, it is stipulated that single black is exclusively used for grounding wires, while single red is used for power lines. They must not be confused. The wire harness is wrapped with woven thread or plastic adhesive tape. For safety, convenience in processing and maintenance, the wrapping with woven thread has been phased out. Now, it is wrapped with adhesive plastic tape.

The wire harness is wrapped with woven thread or plastic adhesive tape. For safety, convenience in processing and maintenance, the wrapping with woven thread has been phased out. Now, it is wrapped with adhesive plastic tape. The connection between wire harnesses and between wire harnesses and electrical components is made by using connectors or wire lugs. The connectors are made of plastic and are divided into plugs and sockets. Wire harnesses are connected to each other with connectors, and the connection between wire harnesses and electrical components is made with connectors or wire lugs. With the increase in the functions of automobiles and the widespread application of electronic control technology, there are more and more electrical components, and so are the wires. As a result, the wiring harnesses have become thicker and heavier. Therefore, advanced automobiles have introduced CAN bus configurations and adopted multi-channel transmission systems.

Compared with traditional wiring harnesses, multi-channel transmission devices significantly reduce the number of wires and connectors, making wiring simpler.

The conductors of automotive wires are made by twisting together many copper wires, and the twisted conductors have good bendability and flexibility. The copper wire used for twisting conductors is made by drawing very thick copper rods through multiple drawing processes using a wire drawing machine. The size of the copper wire is approximately 0.1 to 0.4mm, which is about the same thickness as a human hair. Traditional wire drawing machines can only draw one copper wire at a time. The copper wires drawn by single-head wire drawing machines are drawn at different times and with different equipment, and the process conditions vary greatly. It is difficult to keep various process parameters such as molds, lubrication, drawing force, tempering temperature and time consistent. When such copper wires are put together, their size, material and metallographic structure The mechanical elastic modulus and ultimate elongation at break vary greatly. At present, the 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 this bundle of copper wires contains more than ten pieces. This type of wire drawing machine takes up less space, has a high production efficiency, saves energy significantly, requires fewer workers and has a low labor intensity. Multi-head wire drawing technology is widely adopted by foreign automotive wire manufacturers, mainly because it ensures the high quality of automotive wires.

Selection of wire materials for automotive wiring harnesses and cables

The materials for automotive wiring harnesses are generally selected as copper-core polyvinyl chloride (QVR) and copper-core polyvinyl chloride-nitrile composite insulated low-voltage wires (QFR), while copper-core heat-resistant 105℃ polyvinyl chloride (OVR-105) is applied to the electrical and instrument circuits in the high-temperature areas of vehicles. The world-renowned automotive parts company Delphi has developed recyclable halogen-free wiring harness materials, which is a major breakthrough in the development of power wire technology in the past 30 years. The halogen-free wire harness is coated with "flexible Noryl resin" from GE Advanced Materials of the United States. Flexible Noryl resin is free of halogen, chlorine and lead, with a maximum service temperature of 110 ℃. It has excellent temperature characteristics and flame retardancy. More importantly, this material is very environmentally friendly and recyclable.

The color of the wiring harness: The wiring harness of the bus is intricate and complex. To facilitate wiring and repair, it should be possible to visually distinguish the wire ends. 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 either single-color or two-color: The two-color system is composed of a main color and an auxiliary color. The auxiliary color consists of two axial straight bars, distributed symmetrically. The layout method is to have the main color first and then the auxiliary color, such as red-green wire (RG). The colors and codes of the monochrome 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 for power transmission, when purchasing automotive wiring harness cables, pay attention to the following points: When purchasing wire and cable products, one should observe whether the product's certificate of conformity is fully marked with relevant information such as the product model, specification, rated voltage, number of cores, production date, implemented standard, and license number. The surface of the product should be printed with continuous marks of the factory name, product model, and rated voltage, and verify whether the relevant information of the two is consistent. The outer plastic sheath of the wire is bright in color, fine in texture, and whether there are burrs or protrusions on the surface. The appearance is smooth, round and uniform in color. The conductor uses electrolytic copper, with a bright and slightly soft outer layer. Take another look at the cross-section of the cable. The copper (aluminum) core should be in the middle and the thickness of the plastic layer should be uniform. The length is marked on the certificate of conformity. You can first estimate the length of one coil of the finished product packaging, then count the number of coils of the reel to estimate the approximate length of the entire roll of wire. In addition, pay attention to the diameter of the conductor, and check the length and cross-section of the cable. When choosing wire and cable products, it is best to consult an experienced professional electrician and select cables with appropriate cross-sectional sizes and voltage levels based on your own electrical load.

Closing remarks

To sum up, with the increase in the functions of automobiles and the widespread application of electronic control technology, there are more and more electrical components, and the number of wires will also increase. As a result, the wiring harnesses will become thicker and heavier. Modern automobiles have introduced CAN bus configuration and adopted a multi-channel transmission system. Compared with traditional wiring harnesses, multi-channel transmission devices significantly reduce the number of wires and connectors, making wiring simpler.