A brief discussion on the design of automobile wire harness welding contact

1 Define the wiring harness contact

The wiring harness contact refers to the connecting point of more than 2 wires hinged in the wiring harness.

2 Design Method

The common ways of automotive wire harness contact design are ultrasonic welding, U-type terminal crimping, J/C adapter, solder and so on.

2.1 Ultrasonic Welding

The application of frequency modulation vibration is transmitted to two metal surfaces to be welded, and under pressure, the fusion between the molecular layers formed by the friction between the two metal surfaces in a solid state, so as to reach the welding effect).

The advantages of this method are that there is no need to use materials, high efficiency, good electrical conductivity, environmental protection and safety, and it is the development trend of the wiring harness contact. The defect is that the price and maintenance cost of welding equipment are high. Ultrasonic welding has the following requests.

1) For long solder joints, 5 wires are allowed on each side, and 15 more wires are allowed on the single end solder joints.

2) Allowed wire combinations must meet the request.

3) The tensile force of the wire in the solder joint must reach the requirements in Table 2. The peeling force of the wire in the solder joint must reach the request.

4) Ultrasonic welding is evaluated according to the tightness V to determine whether the solder joint is qualified, and the tightness V should be between 85% and 95%. The formula of tightness is:

V=100(Ak/AI)%

Where: V -- tightness; Ak - cross-sectional area of the solder joint; Al - Sum of line cross sections.

2.2 U-shaped terminal crimping

Physical crimping of wire and copper wire uniformly through U-shaped terminals is a kind of contact method that is widely used at present.

The advantages of this method are easy to operate, high efficiency, good electrical conductivity, crimping equipment and U-shaped terminals are relatively low price; The lack is that compared with ultrasonic welding, it needs to use crimping materials and increase the quality. U-shaped terminal crimp has the following requirements.

1) For U-shaped terminal crimping, 5 wires are allowed on each side.

2) The conductor should be pressed into the crimp part of the terminal, the wire end should be visible on both sides of the terminal and the extension length should not be more than 3mm, the inlet R should be visible on both sides of the terminal, and the wire insulation cover should not be pressed into the terminal.

2.3 J/C adapter

Replace the contact by adding BUSBAR to the connector. The wire passes through the adapter, and the BUSBAR in the adapter cover completes the interconnection of the wiring harness circuit. The advantage of this method is that it is easy to maintain, but it requires crimping terminals, and the cost of using the adapter is higher, while making the wiring harness thicker. It is usually used in the connection of CAN bus.

2.4 Soldering

Soldering is a way of welding the solder wire at the hinged point of the wire with an electric soldering iron. This method is not easy to operate, arbitrary, low consumption efficiency, not environmentally friendly, has been gradually eliminated, and has rarely been used in wire harness design

3 Contact maintenance

If the maintenance of the wiring harness contact is not reasonable, the insulation at the wiring harness contact will be punctured and the short-circuit defect will be formed. In general, the distribution of automotive contacts is divided into two categories: dry zone and wet zone, the contact in the dry zone uses a special tape to stop maintenance, and the contact in the wet zone needs to use a rubber containing heat shrink tube or butyl rubber to stop maintenance to achieve the effect of waterproof sealing.

4 Select the contact position

At present, the wiring harness drawing is stopped by CHS, VESYS and other related software, and the contact position can be displayed in the 2D drawing. The position of the contact is not only related to the cost of the harness, but also to the quality choice of the harness. Unreasonable design will increase the cost of wiring harness, increase the quality of wiring harness, and may also constitute problems such as assembly difficulties. The wiring harness contact position is set with the following points:

1) Select the position where the wiring harness is arranged more smoothly, and cannot select the moving part and the position with greater disturbance.

2) The contact is arranged near the intersection point of each signal line and the trunk, which can effectively reduce the wire and save money.