basic knowledge automotive wiring harness

As we all know, the automotive wiring harness is the main body of the circuit of the automobile, which is equivalent to the blood vessels and nervous system of the automobile. Without the wiring harness, there is no automobile circuit and it is a very important automobile component. At present, whether it is a premium luxury car or an economical ordinary car The form of the harness is basically the same. It is composed of wires, connectors, connectors, and fasteners, which are composed of cardin, plastic, and tape. This paper combines design, production technology, quality, and cost control. Work and everyone do a preliminary discussion, aiming at inspiring the jade, if you have any comments, please do not hesitate to enlighten me

1. The main body of the wire harness is the electric wire, and the car wire, also known as the low voltage wire, is different from the ordinary household electric wire. Ordinary domestic wires are copper single-core wires that have a certain hardness. The automotive wires are all copper multi-core cords, and some cords are as thin as hairs (such as ABS wires that have recently experienced welding problems, and several or even dozens of soft copper wires are wrapped in plastic insulated tubes (PVC)). Soft and not easy to break

HOOHA generally uses UL series of American standard electric wires and Japanese standard AVS, AVSS lines, which are characterized by thin insulation and better flexibility. The following table is the relationship between the cross-section of common electric wires used in the wire harness industry and the current and voltage drop. [ Note: According to industry experience and standards, specific data vary depending on the actual situation

Regarding the colors of the wires, HOOHA has its own standards, which are consistent with the needs of customers. We don't go into details here. From the point of view of the car functions, the following conditions are generally suitable: Take the whole vehicle wiring harness as an example, the 0.5 specification line applies to the instrument lights, Indicators, door lights, ceiling lights, etc.; 0.75 specification line applies to license plate lights, front and rear lights, brake lights, etc.; 1.0 specification line applies to turn signals, fog lamps, etc.; 1.5 specification lines apply to headlights, speakers, etc.; Main power lines such as generator armature lines, ground lines, etc. require 2.5 to 4 square millimeters of wire.

This just refers to the general car, the key depends on the load of the maximum current value, such as the battery's ground wire, the positive power cord is a dedicated car wire alone, their wire diameter is relatively large, at least a dozen square millimeters Above, these relatively large wires will not be incorporated into the backbone, such as the Audi A3 E_BOX three cross-sections are more than 10mm2 wire

The above data is the basic reference standard for selecting wires when the harness is designed, and can also be used when the client checks for maintenance errors.

2. The route of the wiring harness should be carefully considered during design. It is necessary to fully consider the specific conditions of the body, such as the platinum hole and the frame, etc., to comprehensively and comprehensively consider the electrical parts of the vehicle.

The automotive wiring harness assembly aspect mainly considers two aspects: the wiring harness itself is easy to assemble; the wiring harness fixing structure is easy to assemble.

The harness itself is easy to assemble

The layout of the automotive wiring harness should be considered as far as possible without adding too many processes to the assembly process of the vehicle. Separate assembly methods can be used for different areas of the vehicle, such as instrument panels, doors, ceilings, and left and right bodywork. In the design process, the characteristics of different areas are taken into account in a targeted manner, and the designed beam direction must not affect the assembly of other vehicle components [to reduce interference as much as possible] Wire harness fixing structure Easy assembly

In the design of the wiring harness fixing method and the fixed structure must be considered assembly, cannot be in the pursuit of fixed and reliable while adding too many processes to the assembly process, according to the actual design experience summed up the following precautions

1 Try to adopt a simple fixing method, especially for the narrow space areas, such as the wiring inside the door, try to use plastic snaps or tapes. The two models that HOOHA is currently developing with customers are using a large number of karts fixed in the platinum hole, usually with a barbed design to make it firmly fixed.

2 The strength of the assembly operation process, through-hole rubber sheath [ABS wire in the G7SV project should be designed to be <=100 N; for fasteners that require finger press-fitting [Kaddin, operating force <=45 N Hand-pressed fixtures [such as ceiling lights, operating force <= 75N.

3 The fixing hole position of the harness should be as far as possible in the plane area of the structural member. When fixing on the curved surface, it is better to make a small plane on the structural member so as to ensure the fixing in place.

4 Taking into account the convenience of maintenance, harness connectors are placed as close as possible within reach, such as the G7SV E-BOX.

Under the steering wheel, if it is relatively difficult to replace the fuse, it is difficult to disassemble the instrument panel; the entire instrument must be disassembled; the wiring harness at the end of the connector should be set to a certain length to facilitate the insertion and removal of the connector, especially for E-BOX. Fuse box, this should be taken into account when doing wire optimization

5 If the diameter of the wire harness is too large, sufficient space must be reserved when bending a certain angle. Generally, the bending radius of the wire harness is larger than twice the diameter of the wire harness. This problem must be considered in the root of the straight connector to prevent the bending space from being too small. Harness and connector damage; Harness bend, before and after the bending point should be set to a fixed point; for example, G7SV used fiber optic cable and ABS outsourcing line, when the roll is placed there are job instructions to specify the circular radius

6 The distance between the adjacent fixed points of the general long-line harness cannot be greater than 300 mm. If the distance exceeds 300 mm, there is a risk of instability and falling.

7 According to different harness positions and working conditions, different types of harness protection are designed; door harnesses and left and right body harnesses inside the interior trim panel are generally considered to be tape-protected due to narrow space; the chassis is in contact with the vehicle body and exposed Outdoor, the general use of closed bellows with waterproof performance protection

In the vicinity of high-temperature components (such as engines, etc.), wiring must be insulated.

3. How to reduce the weight of the wire harness for cost control

1. Minimize loops during design, use CAN assembly design ideas [is to use as much as possible

A loop controls all functional circuits. Reducing the loop means that the number of wires will be reduced, the weight will naturally be reduced, and the reduction of the loop can effectively increase the signal transmission strength, which can also improve the functionality of the harness while reducing the cost.

2. As far as possible in the design, consider reducing the segmented design and adopting the through trend;

Segmentation has the following disadvantages

a. The total voltage drop on the wire harness increases and the signal strength on the electrical device decays.

b. The increase in connectors will inevitably result in an increase in the number of unreliable connections for electrical connections.

c. In order to fix the additional connectors, it is necessary to add brackets or other fixing methods.

d. Increase wire harness assembly time and material costs

3. Minimize the number of fixing elements such as karts/protective shells as much as possible

4. While ensuring the performance of the harness, try to use lighter tape

5. Others

As the weight of the vehicle harness is reduced, the weight of the entire vehicle will also be reduced, thereby increasing the utilization rate of the engine, reducing the fuel consumption and emissions, achieving multiple purposes and improving the competitiveness of harness products!

4. The future development trend of automobiles is the Internet and new energy sources, which all place higher demands on wiring harnesses; perhaps more and more special wires will be used in future wire harness products, such as power lines with an extra large cross-section larger than 50 mm2. Need to carry larger currents (pure electric vehicles); such as fiber-optic transmission and coaxial shielding impurities that are highly demanding on the signal technology; and for example, some functions will also have the requirement of wireless transmission, which is for wire material/harness design/production. Process quality is a test;

In addition, in addition to the wiring harness, other parts will also make changes and progress in the change, which requires that the wiring harness must also adapt to the other parts of its matching work and its derived new features; opportunities and challenges coexist, which is worth our Go deeper into the study.

Finally, as mentioned at the beginning of this article, the wiring harness is the blood vessel of the car. In the case where the external trend demands an update, the wiring harness will play the role of hematopoietic stem cells, and in order to improve the performance of the car, it will make an internal-to-outer transition to achieve more advanced technologies. The function of the wire harness manufacturer shoulders and bears more responsibilities and missions. This paper is an introductory one. I hope everyone will work hard together and work together to make it a leader in the wire harness industry. It will take a firm position in the upcoming changes. There is a place.