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The development trend of lightweight automotive wiring harness

release time:2021-07-08publisher:Howdy

  1. The components of the wiring harness constitute the structure preface

  The composition of the automotive wiring harness is 75~80% for wires, 15% for terminals and connectors, 10% for outsourcing materials and others.

  1.1 wire

  Traditional automobile wires are copper alloy wires, and the wire diameter is 0.35~25mm. The wires of each automobile are assumed to be connected end to end about 2KM. Based on the weight of a B-class car, the weight of the wire is about 25-30KG. For every 100km of the car, the vehicle will consume nearly 0.1kg of gasoline.

  The wire is an important component of the wire harness, and it is assumed that the use of lighter and more reliable alternative products has become a hot topic in the field of wire harness lightweighting. In recent years, aluminum wires, ultra-thin wires, alloy wires and mixed-core wires have emerged in an endless stream, and are increasingly being paid attention to by wire harness manufacturers and OEMs.

   1.1.1 Lightweight plan for power cord

   Power cords are more and more accepted by wire harness manufacturers because of their large current-carrying capacity, thick wire diameter, and strong pulling force for terminals and wires. Therefore, the plan to use aluminum wires instead of copper wires is increasingly accepted by wire harness manufacturers. Because the wire characteristics of aluminum wire are relatively close to that of copper, the weight is lighter than copper. Therefore, the use of aluminum wire has been widely used in the replacement of 2.5mm~50mm copper alloy wire in the past few years. This plan is relatively old and has achieved significant results in terms of lightweight.

   1.1.2 Lightweight plan for signal lines

  Although the functions of copper and aluminum are relatively close, the tensile strength of aluminum is far inferior to copper. The lightweight plan for small diameters, and the plans chosen by the manufacturers are contending.

  (1) Use of 0.75mm aluminum wire

  Some manufacturers have not discarded the use of aluminum wires, and continue to study whether the tensile strength of their alloys can compensate for the lack of pure aluminum wires. Take the aluminum wire development of a wire manufacturer as an example. In order to satisfy the policy that 0.75mm aluminum wire can replace 0.5mm copper wire, the conductivity policy of aluminum alloy wire is set to satisfy 58%IACS and the tensile strength policy is 110MPa. Although the conductivity of pure aluminum can reach 62% IACS, its tensile strength is only 70 MPa. Then it is necessary to add a second metal in the aluminum wire, the most preferred is Fe, but after analyzing the proportion of Fe, it is found that the processing function decreases after satisfying the requirement of electrical conductivity. Therefore, continue to add the third element. The third element must be satisfied with the processing function to compensate for the shortcomings of Fe, that is, the MS must be small, and the solid solution content of the tensile strength must be high, so Mg is just right.

  In this way, the aluminum alloy mixed with the other two metals is a good substitute for the copper alloy wire, that is, it satisfies the design requirements in terms of electrical conductivity and tensile strength, and greatly reduces the weight of the wire. However, the problems faced are more difficult to deal with.

  CuO and Al2O3 have a conductivity of 10~7s/cm, both of which are non-conductive materials, so the conductivity can only be ensured by crimping and damaging the oxide film. However, there are also hostility to compression ratio and persistence. For Al alloy wires, the suitable crimping area is narrower than that of Cu alloy wires, making it more difficult to handle. Therefore, the manufacturer improved the shape of the terminal crimping groove to improve the wire sticking force and current connection function.

   dealt with the problem of crimping, but also faced the problem of corrosion protection. The metal vividness of aluminum is more vivid than that of copper, so in the process of crimping with the copper terminal, the contact direction will simply cause contact corrosion. In a vulcanized environment, metallic aluminum is very simple to dissolve. In order to deal with this problem, the contact orientation (including the crimping part to the rear of the terminal) using resin material heat shrink sealing can effectively deal with this problem.

  (2) Copper alloy ultra-fine wire

The wire utilization rate of the signal wire has always been very low. The 0.5mm/0.35mm copper wire can accept a current of about 10A (ambient temperature is 24℃), but the real current flowing in the signal wire is often only a few milliamperes, which is a waste of resources. It has become the focus of many wire harness manufacturers. Wires of 0.13mm2, 0.08mm2, and 0.05mm2 are now available and used in many companies.

How to reduce the wire diameter so that the low wire diameter wire can not only meet the requirements of signal transmission, but also meet the tensile strength of crimping, the column force of the terminal penetration, etc. are the key issues for the wide application and wider promotion of ultra-fine copper wires. . In order to meet the requirements of mechanical function, adding alloy to copper wire is also the solution to this problem. CuSn, CuAg, CuMg and copper clad steel are the favorite products of various wire harness manufacturers in recent years.

   Take the 0.35mm wire and the copper alloy 0.13mm wire as an example, the electrical function is similar, but the weight is reduced by 60%, and the overall outer diameter is also reduced by 20%. These data flashed its excellent market prospects and economic benefits. However, it does not mean that the 0.13mm copper alloy wire can completely replace the 0.35mm copper wire. Anyone who understands physics knows that the current carrying capacity of metals changes with temperature, and this change becomes more obvious as the resistance increases. Generally speaking, in the environment below 110 degrees, the function of 0.35mm copper wire and 0.13mm copper alloy wire is not much different, and it can be replaced in signal wire. Therefore, this bundles the application environment of the 0.13mm wire, which can be widely used in the cabin, but the engine room needs to be carefully calculated and used according to the address.

   Although the 0.13mm copper alloy wire has great market prospects, its mechanical strength and the column force to penetrate the plug-in unit are the directions for further research in the future. Different from the aluminum wire method, because the wire diameter is too small, even if new alloys are incorporated into the alloy, it is difficult to meet the requirements of economic efficiency with both mechanical and electrical functions. Therefore, some wire harness manufacturers have jumped out of the metal-strength binding, and seek a treatment plan on the outsourcing of the wire. Fortunately, so far, many manufacturers need to find good alternative resources. The original wire insulation layer is made of PVC, XLPE materials, and contains halogen and other toxic substances.

   In recent years, after the World Environmental Protection Organization has put forward the standards for the recycling of automobile environmental protection, a new type of halogen-free insulation layer has been developed into PPE. Its composition is safe, environmentally friendly, and has other flame retardant properties. Used by more and more manufacturers. Change from PVC to PPE data. With the standard 0.35mm wire, the diameter is reduced by 27% and the area is reduced by 47%.

   Assuming a more specific analysis of copper alloy wires, it can be known that CuSn has excellent metal strength characteristics, and CuAg has excellent electrical functions. This can be used as a different reference basis for wire crimping and function selection.

  (3) Ultra-fine wire of mixed materials

   Japanese companies have always been the first in terms of cost saving and power control. The 0.13mm2 wire first developed at SUMITOMO is the thinnest wire. It uses a mixed material method. The center is a copper material and the periphery is another material. The copper wire diameters of the center and the periphery are also Are not the same. Although this wire also satisfies the electrical performance requirements of transmission, its shortcomings are also obvious: the manufacturing process is cumbersome, the production cost is high, ultrasonic welding is not possible, the crimping of the terminal is attributed to the unconventional crimping, and special equipment is required. Therefore, it was not promoted at the time.

  2, miniaturization of connectors

   The development of wires and connectors have always been complementary. With the development of special wires, the miniaturization of connectors has become faster and faster. The manufacturers of all connectors are vigorously developing miniaturized connectors. Since the mid-1990s, terminals with a width of 0.64 slices have been available. Typical MQS terminals of TE and 0.64 terminals of SUMITOMO. This kind of small terminal can be used in signal transmission, can greatly reduce the utilization rate of 1.5 slice width, and directly reduce the standard standard of the connector.

  3. Lightweight protection of wiring harness

   There are many ways to protect the harness, including guard plates, rubber parts and brackets. In order to reduce the weight of the work, the following work can be developed for the protection of the wiring harness:

   (1) Reduce the structure of the metal bracket, and use high-strength plastic shields instead of metal brackets: such as fuse box brackets and engine compartment tissue brackets (selected according to ambient temperature).

  (2) Reduce the selection of plastic guard plates, and use body structure, special karting and fixing parts instead of guard plates.

  (3) Reduce the use of corrugated pipes and use wear-resistant fiber and cloth-based fiber pipes instead of corrugated pipes. It can not only reduce costs, but also reduce noise.

  (4) Reduce the use of rubber parts, and use foam instead of rubber parts where the sealing requirements are not high.

  (5) The organization of the wiring harness reduces the internal connection as much as possible, which not only reduces the component of the connector, but also reduces the component component and the body structure component required for the connector to be fixed.

   4. Summary

   This topic starts with the total components of automobile wiring harness, analyzes the direction of weight reduction, and the development trend of light weight of various parts and components. It specifically introduces the technical development direction and technical difficulties of wires, connectors, wiring harness protection, etc. The in-depth discussion on the subject of lightweight automotive wiring harnesses is of great significance.