Harness cost reduction from a design perspective

The pressure of cost reduction has always run through the whole process of automobile research and development. The following is about the cost reduction of automobile wiring harness from the perspective of design. First, the universality and continuity of wiring harness design platform is an important aspect of modern product design. In short, at the beginning of the design, the same mature platform model should be used as a reference as far as possible, for example, choosing the same electrical functional parts, wiring harness accessories (including ties, rubber products, bracket), wrapping methods, etc., can not only shorten the development cycle of vehicle wiring harness (conducive to the long-term development of the company), but also shorten the procurement cycle of new parts for new projects. In this way, the cost is reduced, and once 2 to 3 models are designed in this way, the cost will be greatly reflected. However, the establishment of a mature power system platform is not smooth sailing, which requires a lot of time, energy, material resources and later test and promotion, but it is beneficial to the long-term development of the industry, and it is necessary to standardize the packaging mode of the project platform (including the simplification of conductor specifications, the standardization of conductor color selection, the standardization of electrical functions, and the standardization of wiring harness accessories). This virtually saves design cost, risk cost and manufacturing cost. 2. Refinement and optimization of design process At present, many people in China are very casual in style and single in thinking when designing wiring harness, which is very unscientific. When designing the wiring harness direction, the design of wiring harness nodes and grounding points shall be fully considered, and the principle of proximity shall be adopted as far as possible to avoid line winding. At the same time, when designing the wiring harness, the wire diameter is usually enlarged. Of course, this can improve the safety of the car. However, if the design process is not refined, the original 1mm2 wire is enough. Choosing the 2mm 2 wire will obviously increase the cost. If the design of wiring harness is divided into single wires, the cost of wiring harness can be reduced by fully considering the use, length and length of each wire. 3. Three-dimensional simulation of wiring harness design controls the design process from the source to realize electronic loading. Simulate the direction of the vehicle line with the digital model, repeatedly verify whether the direction is reasonable, and verify the direction and length of the harness by using the sample in the real vehicle. Through several rounds of three-dimensional data and real vehicle loading verification, the problem of interference between wire harness and sheet metal is avoided in the design stage, the problem of branching is solved, the wire length is effectively controlled, and a large number of rework in the later stage is avoided. The simulation demonstration and optimization design are carried out by using the three-dimensional prototype vehicle, which greatly saves time and energy, and also saves the cost to a certain extent. 4. To optimize the layout of wiring harness, first of all, we should fully understand the electrical principles of the vehicle and divide the wiring harness of the vehicle reasonably (engine compartment wiring harness assembly, engine wiring harness assembly, instrument panel wiring harness assembly, etc.). However, the design of the wiring harness in the engine compartment is particularly important, which is related to the selling point of the real vehicle in the future. Therefore, the engine layout (horizontal and vertical), the electrical principle of the whole vehicle and the later electrical fault maintenance need to be considered comprehensively in the design. There is also a project to go with the new powertrain, which requires the wiring harness to be replaced at the same time. The basic models of the previous platforms are all MT vehicles with lower configuration, while the new vehicles include AT powertrain models with higher configuration, and there are fewer reserved holes when the engine harness is connected with the engine compartment harness at the beginning of the design. There are two schemes for re-design: Scheme 1: According to the traditional idea, the engine ECU and the whole vehicle harness are completely connected to the engine harness. The result shows that the 40-hole connector at the interface between the engine harness and the engine compartment harness is insufficient (18 holes are missing). Consider replacing the multi-hole connector first, but the multi-hole connector cannot be replaced due to the narrow wiring space. In the preliminary stage, a docking connector is added. Considering that this is the docking of the EFI system, a pair of 20-hole hybrid inlet connectors are selected to try to find a fixing point on the ECU bracket. Option 2: The pin definition of the engine ECU is analyzed. It is found that among the four connectors connecting the engine ECU and the vehicle harness, two connectors (temporarily called A and B) are related to the sensors on the engine EFI system, and the actuator is not directly connected, so A and B can be considered to be placed in the engine compartment harness to reduce the number of docking holes. Through the real vehicle verification, it is found that the scheme is feasible, and the thickness of the engine harness is reduced, and the hole position is fully utilized. The key is to save two imported connectors and a fixed buckle. If the cost of saving 2 yuan per vehicle is calculated, 50000 units can be produced annually after SOP, and only one pair of connectors can save 100000 yuan. The layout of the wiring harness is reasonable, waste is avoided, and the cost is effectively controlled. 5. Reasonable design of harness protection The whole car body is roughly divided into three environmental zones: ① hot/wet zone (mainly in the front cabin); ② cold/dry zone (mainly indoor); ③ cold/wet zone (mainly in the tail). Various environments have different requirements for harness design. ① Thermal conductor, bellows such as TXL/PP, etc. ② Use wires with low temperature resistance requirements at low temperature, such as TWP/PE. ③ Use sealed plastic products and heat-shrinkable tube with adhesive for crimping. ④ Crimping with non-sealed plastic parts and tape protection. According to the characteristics of these different environments, the types of wires and bellows should be reasonably selected to avoid waste.

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