Quality verification and analysis of automobile harness

Automobile harness is an important part of modern automobile and the network main body of automobile circuit. It guides the current to all the electrical components of the vehicle and plays an important role in realizing the intention of vehicle personnel. The engine is equivalent to the human heart, and the harness is like the human blood vessel or nervous system.

Among all kinds of automobile faults, the adverse effects caused by wire harness account for a large proportion. If the wire, rubber and hose in the harness are damaged, resulting in short circuit or open circuit of the wire, the transmission function will be damaged. This will not only lead to the inaction of various equipment, but also lead to major problems such as smoke, fire, walking, turning, braking and so on.

As the harness occupies such an important position in the whole vehicle, as the quality management personnel of the automobile manufacturer, we must focus on controlling and strictly managing the quality of the harness. In order to let customers ride safely and comfortably, the quality of harness must be verified through systematic and professional work. This method is the harness certificate, also known as w.p.t verification, that is, the viewpoint of harness verification.

1. Overview of harness validation.

Harness verification is called w.p.t verification. W.p.t refers to the initials of wire, pipe and tube. It generally refers to harness, cable, hose, rubber hose and other components to check whether they are damaged, i.e. w.et verification.

In the development and trial production stage of Dongfeng Honda new model, the factory quality personnel need to complete the harness verification in a specific stage, and the harness verification in each stage is different.

Although the content and form of harness verification are different in each stage, the verification viewpoint of each harness verification is the same. With these views, we can effectively find and solve problems, so as to improve quality and prevent defective goods from flowing out of the next process.

2. Harness validation point of view.

Common harness problems include interference, bite, insufficient Cl, difficult installation, improper installation, wrong assembly, stretching, stretching, etc. To solve these problems, the harness verifier will find and solve the problems from the corresponding point of view.

For the convenience of explanation, the following discusses the viewpoints to be adhered to in the process of harness verification based on the problems existing in various harness verification.

2.1 interference.

After the assembly of the whole vehicle, the harness contacts and interacts with the sharp edges of the components around the harness (sheet metal, trim panel, functional components, etc.), indicating the interference between the harness and the object components. Interference is the easiest and most common problem in harness verification.

Considering the possibility of interference between harness and blue control box, the length of clip 1 and clip 2 points ~upointb can be calculated. If the length with harness Max is less than the tolerance, interference will occur. If the length is greater than the max tolerance of the harness, there is no interference.

Calculate the distance from Clip1 to pointb: l01mm.

Distance from clip2 to pointb: 200.5mm.

When the maximum length of trunk line is 305m, 305 > 101 + 200.5, there will be interference between harness and control box.

During extension, if the data values of a, B and D3 change (C = a + b), what will happen to the judgment of harness interference. It can be seen that by calculating the distance between the nearest two fixed points of the possible interference parts of the wire sheet and the possible interference points of the components, whether the harness and the control box interfere can be determined. In the early stage, when there are only faces and the car is not completed, you can find the part that may interfere as the key position.

2.2 cutting.

Harness cutting is a more obvious manifestation after the interference of wire harness and surrounding components, which more directly reflects the consequences of harness interference. Wire harness cutting will lead to exposed copper wire or wire cutting, resulting in short circuit or open circuit. Its external manifestation is that the relevant functions do not move, and the car burning phenomenon is more serious.

In the whole vehicle, due to the relationship of spatial structure, the direction design of harness inevitably has some compact areas. The actual completed vehicle cannot have a perfect non-interference layout. At this time, it is necessary to consider whether there is a hidden danger of harness cutting in the area where the harness must contact the surrounding components. Therefore, in the harness verification, the following factors need to be considered to determine the risk of cutting at the interference part.

2.2.1 protection form of harness.

The wiring harness has the following protective devices: Twisttube, bellows (Cortube), hose (PVCTube), PVC tape (PVCTube), polyurethane foam (UrethaneFoam) and cotton tape (CushionTube).

Each kind of exterior decoration has different models, but the basic physical and chemical properties of the same exterior decoration between different models are roughly the same. Appropriate protective exterior decoration can be selected according to its characteristics.

As for the hidden danger of wire harness cutting, it is mainly aimed at the wear resistance of external fittings, which can be simply sorted from strong to weak: twisttube > cortube > cushiontape > pvctube > urethanefoam > pvctape.

2.2.2 harness.

Compare the 2D drawings to determine the wire length, external installation and model between the two fixing points of the harness at the interference part. Tolerance shall be considered for line length. What is the degree of harness interference under the limit Max or min state; What is the external installation of the harness, what is the model, and whether it has a protective effect in the current environment: sometimes there is no PVC tape around the corrugated pipe (cortube). If the bellows model is not appropriate, the wire may jump out of the bellows opening. In this case, we should pay attention to the possibility of interference around us.

2.2.3 materials of contact parts.

If there is relative movement and friction at the contact part, the harness may be broken. Generally, the default sharp edge of sheet metal cannot interfere with the harness wrapped by non bellows or twisttube. There are welding spots at the welding parts of sheet metal. If there are long burrs on the welding joint and the harness is close to the burr, the burr may go deep into the harness and puncture the wire, resulting in the cutting of the harness.

2.2.4 contact part shape.

The harness protected by the bellows is in contact with the sharp edge of the sheet metal. Although protected by bellows, the harness may also be damaged if the relative positions of bellows and sharp edges are perpendicular to each other.

2.3 bite.

The seizing phenomenon is basically due to the fact that the harness direction (either the design direction or the tolerance fluctuation) is just located at the assembly position of the surrounding part, resulting in the extrusion of the harness between the two mating parts.

In the process of harness verification, it is sometimes found that the harness is stuck between components, sometimes it may be due to the natural sag of harness gravity, and sometimes it may be due to too long or too short tolerance fluctuation.

The harness is mainly composed of wires and their protective devices. Harness verification is to ensure that the wires in the harness are not damaged by external forces, affecting the function. Therefore, the slight deformation of the protective exterior can be accepted by the quality personnel without causing wire damage. In other words, as long as the bite degree does not affect the wires in the harness, it can be considered that there is no problem with the harness here.

3 conclusion

As an important part of electrical installation, harness verification requires quality management personnel to continuously improve professional knowledge and accumulate experience in combination with various types of verification performance. The above views on harness verification hope to attract jade and form a perfect and mature viewpoint on harness verification.

In the future, if we can evaluate the whole vehicle harness from the perspective of designer, quality manager and assembler in combination with the designer's design point of view; Then the harness verification can be promoted more comprehensively. It also ensures that customers get the most comfortable user experience.