Automobile wiring harness is the main body of automobile circuit network, and there is no automobile circuit without wiring harness. Wire harness refers to a component that is connected to a circuit after the contact terminal (connector) made of copper is crimped with a wire and cable, and then plasticized to an insulator or an external metal shell. Wire harness industry chain includes wire and cable, connectors, processing equipment, wire harness manufacturing and downstream application industry, wire harness application is very wide, can be used in automobiles, household appliances, computers and communication equipment, a variety of electronic instruments and meters, the body wire harness connected to the entire body, the general shape is H-shaped.

Main specifications and performance requirements of automotive wiring harness

1. Cross-sectional area of the conductor

The cross-sectional area of the conductor is selected according to the load current of the electrical equipment. The general principle is that the electrical equipment working for a long time can choose the conductor with the actual carrying current of 60%, and the electrical equipment working for a short time can choose the wire between 60% and 100% of the actual carrying current. At the same time, the voltage drop and wire heating in the circuit should also be considered, so as not to affect the electrical performance of the electrical equipment and the allowable temperature of the wire; In order to ensure a certain mechanical strength, the general low-voltage wire cross-sectional area is not less than 1.0mm².

2. Color of wire Car circuits have color and numbering characteristics. With the increase of automobile electrical equipment, the number of wires is also increasing, in order to facilitate the identification and maintenance of automobile electrical equipment, the low-voltage line in the automobile circuit is usually composed of different colors, and the color letter code is marked on the automobile electrical circuit diagram. The color code of the wire is usually marked on the automobile circuit diagram (represented by one or two letters), the color of the wire on the car is generally different, and there are two selection principles of monochrome and two-color commonly used. For example: red (R), black (B), white (W), green (G), yellow (Y), black and white (BW), red and yellow (RY). In the two-color line, the former is the main color, and the latter is the auxiliary color.

3. Physical properties of the wire (1) Winding performance, the wire between the door and across the body should be composed of wires with good winding performance. (2) high temperature resistance, the wires used in the parts with high temperature are generally covered by vinyl chloride and polyethylene with good insulation and heat resistance. (3) Shielding performance, in recent years, the electromagnetic shielding lines used in weak signal circuits have also been increasing.

(1) The cable is half folded, coated with insulating paint and dried to increase the strength and insulation performance of the cable. (2) The new type of wire harness, the local plastic wrap is put into the plastic corrugated tube of the side incision, so that its strength is higher, the protection performance is better, and the search of line faults is more convenient.

Production process of wire harness

The first station of wire harness production is the open wire process. The accuracy of the opening process is directly related to the entire production schedule, once there is an error, especially the opening size is short, it will lead to rework of all stations, time-consuming and laborious affecting the production efficiency. Therefore, in the preparation of the wiring process, it is necessary to reasonably determine the wiring size and stripping head size of the wire according to the requirements of the drawing.

The second station after opening the wire is the crimping process. Determine the crimping parameters according to the terminal type required by the drawing, make the crimping operation manual, and indicate on the process file and train the operator if there are special requirements. For example: some wires need to pass through the sheath before crimping, it needs to preassemble the wire and then return from the preassembly station to crimping; There are also puncture type crimping tools used for special crimping, which has good electrical contact performance.

Then is the pre-assembly process, first of all to prepare the pre-assembly process operating instructions, in order to improve the assembly efficiency, complex wiring harness to set the pre-assembly station, the preassembly process is reasonable or not directly affects the efficiency of the total assembly also reflects the technical level of a process personnel. If the pre-assembled part of the assembly is less or the assembly wire path is inappropriate, the workload of the total assembly personnel will be increased and the speed of the assembly line will be slowed down, so the process personnel will often stay on the site and constantly summarize.

The final step is the final assembly process. Be able to design tooling equipment, material box specifications and dimensions according to the assembly table designed by product development department, and attach the numbers of all assembly jackets and accessories to the material box to improve assembly efficiency. Prepare the assembly content and requirements of each station, balance the entire assembly station to prevent a bit of excessive workload and pull down the speed of the entire assembly line.

The composition of the harness

Automotive wiring harness consists of wires, terminals, cladding, connectors and other parts.

1.Wire wire is the main part of the harness, usually called wire, is the main part of the harness, its role is mainly to carry the load required current. The important parameter of the conductor is the current carrying capacity, which is affected by the wire diameter (cross-sectional area of the conductor), the wire length, the conductor resistivity and the ambient temperature.

2. Connectors Connectors are also called connectors, connectors, or connectors. Connector is an indispensable component for wiring harness to connect with other electrical equipment, which is divided into wiring harness end connector and electrical appliance end connector. We often hear the male connector (referred to as male) and the female connector (referred to as female), of which the connector where the male terminal is called the male connector, the connector where the female terminal is called the female connector, and the end of our wiring harness is usually the female connector.

The connector can be divided into two categories: waterproof type and non-waterproof type. At the beginning of the design, PIN pins of different widths are selected according to the current carried by each PIN PIN, and then chambers containing different PIN pins are formed on the connector, thus forming a Housing containing multiple pins.

(1) the CPA - molded case ConnectorPositionAssurance secondary locking institutions: Its function is to ensure that the buckle of the locking mechanism will not easily exit after the plastic case and the electrical interface are assembled in place. Because of its special function, the CPA must ensure the operability and identifiability of workers when designing, which requires that the CPA must be an independent institution on the plastic case and must also have a special color identifier. (2) Waterproof sealing ring: There are two kinds of waterproof sealing mechanism, one is used for the seal between the plastic shell and the plastic shell, and the other is used for the seal of the terminal lead line. (3) TPA - terminal TerminalPositionAssurance second locking structure: Not all terminals need a secondary locking structure. VW requires that TPA should be used if the terminal width is less than 2.8mm (including 2.8). In order to ensure the installation convenience of the wiring harness factory workers, the color of TPA should also be recognizable, and the assembly should have a clear feel. An anti-locking mechanism is a must in TPA.

3. Wire harness bandages The main function of wire harness bandages is to protect the wire harness, according to the different materials of the bandages, the types of bandages are mainly corrugated pipe, PVC tape, duct tape, flannelette tape, sponge tape and aluminum foil tape.

Due to different materials, the material characteristics of different bandages are not consistent, corresponding, its application conditions and methods on the harness assembly are not consistent, the specific selection should be based on the harness specific use environment and its wear resistance, heat resistance.

4. Wire harness fixings are different from other parts on other cars, wire harness is flexible parts, wire harness can not be sent according to the established shape, so in order to constrain the layout path of the wire harness on the vehicle, additional parts need to be added to fix the wire harness, these additional parts are wire harness fixings, it plays a role in fixing the wire harness and constraining the layout path of the wire harness.

Harness fixings are: cable tie, buckle, rubber sheath, harness bracket, etc., according to the different installation environment of the harness, such as harness installation space, temperature requirements, waterproof requirements, the shape and material of each harness fixings are not consistent, even so, harness fixings also show a trend of standardization, and harness platform selection is one of the easier parts to achieve.

5. Wiring harness accessories Wiring harness accessories refer to other smaller products on the wiring harness assembly, such as the product label fuse clip on the wiring harness assembly.