Automotive wiring harness systems are relatively weak and easily damaged parts. During the development and use of the vehicle, vehicle function failures due to wiring problems frequently occur. This article mainly systematically summarizes the failure problems caused by the wiring harness system in the vehicle manufacturing process, and proposes improvement measures based on the PDCA scheme, which effectively controls the failure modes of the wiring harness in the vehicle development and manufacturing process.
With the significant increase in the number of circuits and power consumption in automobiles, how to more effectively and rationally arrange a large number of vehicle wiring harnesses in a limited automobile space has become a problem faced by the automobile manufacturing industry. This article summarizes, summarizes and organizes the wiring harness failure problems in automobile production, and proposes improvement plans, which plays a certain guiding role in the design and layout of automobile wiring harnesses.
1 Automotive wiring harness layout and failure modes
1.1 Automotive wiring harness layout
With the development of vehicle safety, intelligence and comfort, sensors, cameras and ECUs occupy a certain amount of space, causing the wiring harness layout space to become increasingly narrow. At the same time, the increase in functions means that the number and volume of wires continue to increase. Vehicle assembly and disassembly and transportation convenience also put forward higher requirements for wiring harnesses.
Figure 1 shows the wiring harness distribution diagram of a certain vehicle model. In order to facilitate transportation and assembly, the entire vehicle wiring harness is cut into 10 parts.
1.2 Failure modes of automobile wiring harness
The wiring harness is a relatively weak part of the vehicle. It is easily damaged or failed whether during manufacturing, assembly, or subsequent use. The article sorts out the failure modes of wire harnesses from various aspects such as wire harness manufacturing, transportation, vehicle assembly and subsequent use, and analyzes typical problems.
1.2.1 Wiring harness manufacturing failure
Automotive wiring harnesses are mainly composed of wires, terminals, connectors, wrappers, staples and wire trough brackets. The composition of irregular parts makes wiring harness manufacturing a low-automation, labor-intensive industry.
Numerous manual operations affect the standardization of wire harnesses, so failure during the wire harness manufacturing process is a random and uncontrollable failure mode. Table 1 shows the most common failure modes of automotive wiring harnesses during the manufacturing process. The manufacturing quality of wire harnesses needs to be ensured in all aspects of manufacturing: setting reasonable specifications and parameters for mechanical equipment, establishing standardized manual operations and comparison panels, and finally conducting spot checks and comprehensive inspections on wire harnesses to ensure the manufacturing quality of wire harnesses.
1.2.2 Wiring harness assembly failure
The layout of the wiring harness on the actual vehicle will be broken up into multiple parts based on the vehicle assembly process, thereby improving assembly and maintainability. However, at the same time, the increase in wiring harness interfaces and positioning parts means that the probability of failure increases. The article classifies and summarizes the failure cases that occurred in the assembly process of the vehicle to improve the assembly reliability of the wiring harness.
The assembly of the wire harness almost continues from the final assembly interior station to the final assembly station. The span is very large and there are many contact areas. Combining its failure modes and manifestations, it can be roughly divided into fixed failure (40%), functional failure (20%), cosmetic failure (20%) and other failure modes (20%).
1) Fixation failure is when the positioning parts of the wiring harness itself fall off at the fixing holes or ties. This type of failure does not affect the function and use of the entire vehicle.
2) Functional failure is a relatively serious failure mode, which will cause the loss of a certain function of the entire vehicle, which will seriously affect the safety of the car and the driver.
3) Cosmetic failure is a form of failure that affects customer perception.
Wiring harnesses are often arranged in areas that are not easily perceived by customers. However, due to factors such as the wiring harness supplier's process or space, the assembly of parts attached to them will be affected, causing matching or aesthetic problems. For such problems, in the early design, it is necessary to consider whether the motion envelope area of the wire harness or connector is in contact with the surrounding components.
There is a risk of interference, so choose the appropriate position to arrange the fixed points to ensure that the aesthetics is improved while meeting the function.
1.2.3 Wiring harness durability failure
Durability failure is a failure mode that forms in the intermediate links as the car is used. It occurs randomly along with the life cycle of the car and is unpredictable. Once it fails, it will cause great complaints from customers about the brand. This type of failure mostly occurs in the envelope area of moving parts and occurs after the wire harness reaches a certain degree of wear, so it is not easy to detect in the early stage.
In summary, the layout of the wire harness in the motion envelope area needs to be strictly controlled, and strict evaluation standards must be followed for the wear of the wire harness.
2 Measures to improve the reliability of wire harness design
Wire harness design is a process of continuous improvement and optimization, and its entire life cycle should be considered.
In the early stages of vehicle design, the layout and motion envelope of the wiring harness are fully considered and identified. At the same time, combined with DV/PV testing of wiring harness components, the weak links in the design are continuously strengthened. Finally, continuous attention is paid during the actual vehicle assembly stage and after-sales stage. , and at the same time classify and summarize the problems that occurred, and input them into the early development of the next model, thereby avoiding the recurrence of problems and improving the consistency between virtual design and real vehicle performance.
3 Conclusion
Lines are a type of parts that are prone to problems in the vehicle system. Only by conducting adequate pipeline assessments in the early design and project stages can line problems be effectively controlled. This article combines the preparation of a certain vehicle model's wire harness itself and the vehicle assembly process to summarize the various failure modes and control methods of the wire harness. At the same time, it proposes a control method for the wire harness PDCA. Combined with the later failure modes, integrated simulation and dynamic envelope virtualization are performed in the early stage of wire harness layout. The analysis improves the quality of wire harness development and provides a good reference for the wire harness in the early design stage.