Analysis of Heavy Truck Connecting cable Layout Design

This article takes the wiring harness layout of commercial vehicles as the core and clarifies the three-dimensional layout design principles of the wiring harness of the whole vehicle. Propose the wiring harness layout method of the whole vehicle, analyze the issues that should be paid attention to in the wiring harness layout of the whole vehicle, and improve the rationality and scientificity of the wiring harness layout of the whole vehicle.

1 – Introduction
The automobile wiring harness is an indispensable part of the automobile, and it is also the “nervous system”. It is the wiring component that connects various electrical equipment in the automobile circuit. In order to ensure the safe operation of the vehicle, the vehicle wiring harness system must be scientifically designed to improve the reliability of the vehicle wiring harness and improve the safety and durability of the vehicle wiring harness system. This article mainly introduces the three-dimensional layout principles of the vehicle wiring harness and elaborates on the wiring harness fixing method. It is mainly based on the design experience of three-dimensional wire harness layout personnel, and provides certain reference and help for three-dimensional layout and design ideas of low-voltage wire harnesses.

Car wiring harness clip fixing instructions

2 – Principles of wiring harness layout
The three-dimensional design of the wiring harness needs to be simple in structure, easy to disassemble and assemble, beautiful in layout, and well fixed and protected. At the same time, the wiring harness layout needs to consider the wiring harness principle to make the wiring harness path the shortest possible. Try to use modular design in the wiring harness to reduce loops. The main layout principles include wire harness reliability, wire harness aesthetics, assembly and maintenance, electromagnetic interference protection, etc.
2.1 Reliability
Vehicle wiring harness reliability requirements:
(1) When laying out the wiring harness, the routing should be as concealed as possible and should not exceed the rigid outer contour of the components. Generally arranged along the inner edges and corners of the body and frame;
(2) The diameter of the wire harness in the digital analog must be consistent with the actual wire harness. On the one hand, it is necessary to consider the specific outer diameter of the outer wrapping layer, and on the other hand, it is calculated based on the wire diameter in the highest configuration. When the main trunk cannot be evaluated in detail, the maximum diameter calculated in principle or based on the actual vehicle model will be evaluated;
(3) In areas where there is a risk of water intrusion, the outlet direction of the connector tail cannot be upward. When the outlet direction is horizontal, the tail harness must be directed downward first, and the water guide bend must be designed to prevent the connector from becoming the lowest point of the branch;
(4) When the cab wiring harness passes through the through hole, it needs to be protected by a rubber sleeve. When passing through parts with sharp corners and relatively sharp surfaces, the surface of the parts should be wrapped with protective pads or rubber protection added to avoid damage to the surface of the wire harness;
(5) The wiring harness layout should avoid parts that may cause damage to the surface of the wiring harness, such as frames, brackets, bolt heads, and edges of components, and ensure that the distance between the wiring harness and the wiring harness is ≥ 10 mm. The wiring harness should be kept away from high-temperature components such as engine exhaust pipes, superchargers, and air compressors. Set up a heat insulation board between high-temperature components with a temperature of ≥200°C (such as engine exhaust pipes), and ensure that the distance between the wiring harness and the heat insulation board is ≥50mm. The distance from the air compressor pipeline is ≥50mm. The wiring harness should avoid rotating parts (such as fans, pulleys, drive shafts, generator external fan blades, etc.), and the distance from relatively rotating parts should be ≥50mm.
(6) The connector tail harness needs to be fixed within ≤120mm, but special parts such as MP5, cigarette lighter and other rear-mounted parts need special treatment.

Schematic diagram of sheet metal fixation of automobile wiring harness

2.2 Aesthetics
Vehicle wiring harness aesthetic requirements:
(1) The direction of the wiring harness should be consistent with the direction of the accessories. In the projection direction, arrange it horizontally and vertically, and try to avoid oblique arrangement;
(2) The color of the vehicle wiring harness design needs to be coordinated. Generally, it is recommended to use dark-colored connectors on the exterior of the car body; the wiring harness cannot be entangled or crossed;
(3) The wiring harness should be as consistent as possible with surrounding wiring harnesses, water pipes, air pipes, oil pipes, etc. overall beauty;
(4) The selection of wire harness wrapping materials must consider aesthetics, and the colors should not be messy.

2.3 Assembly and serviceability
Vehicle wiring harness assembly and maintenance requirements:
(1) It is recommended that the connectors of the wiring harness be arranged in a position that can be reached by hand, or the connector can be accessed after simply disassembling some parts;
(2) It is not recommended to arrange connectors of the same model in adjacent locations to avoid misinsertion during assembly and damage to wiring harnesses and electrical appliances;
(3) Wire harness accessories such as ties and buckles on the wire harness should be placed on the wire harness as much as possible to avoid on-site assembly affecting the production rhythm;
(4) When the chassis wire harness passes through the first crossbeam, a guide bracket needs to be designed near the crossbeam to protect the wire harness from passing through;
(5) Marking points need to be added to the chassis wire harness at the first crossbeam, wire harness threading hole, front axle centerline, and flywheel housing to facilitate wire harness installation;
(6) Check the assembly tool space of the bolts on the wiring harness, and use electric tools to check;
(7) It is necessary to understand the assembly process, tooling, etc. of the wire harness, and consider the impact of tooling on the wire harness design.

Bolt fixation of automobile wiring harness

3 – How to fix the wiring harness
3.1 Connector fixing solution
The connectors on the wire harness are mainly fixed by staples, sheet metal, bolt connections, etc.
(1) Clamp fixation is shown in Figure 1. Generally, the sheet metal holes suitable for staples are Φ6mm, Φ7mm, and 7mm×12mm. For larger spaces, connectors generally use Φ6mm or 7mm staples. For those who need to strictly limit the direction of the wire harness, Φ7mm×12mm clamps can be used for the connector. After installation, it can prevent the wire harness from twisting, and the use effect is better. After installation is completed, it has strong fixation stability.
Figure 1 Schematic diagram of nail fixation
(2) After the connector is fixed through the sheet metal, use the fixing clip to fix it, see Figure 2. The connector is firmly fixed in this way, and if you have high reliability requirements, you can choose this fixing method.

The sheet metal bracket of the automobile wiring harness is fixed with a tie

Figure 2, Schematic diagram of sheet metal fixation
(3) The connector is clamped by the fixing plate and matched with the sheet metal bracket through bolt connection, see Figure 3. This fixing method is suitable for fixing connectors with many connector holes, and the fixing method is reliable.
Figure 3, Bolt fixing diagram

3.2 Wire harness fixing solution
3.2.1 The sheet metal bracket is fixed with cable ties
The wiring harness fixing bracket is connected to the frame or engine through bolts, and then the wiring harness and bracket are bundled with a tie, see Figure 4. Generally, the tie hole is a 5mm×10mm slot hole. To ensure the mechanical strength of the bracket, add reinforcement ribs if necessary.
Figure 4 Schematic diagram of sheet metal bracket and tie tie fixation

3.2.2 Fastening with cable ties
Wire harness fixing ties come in various forms. When it is necessary to maintain a set distance between the fixed point and the wire harness assembly or to avoid the wire harness from naturally sagging too much, these products can be preferred because the fixing method is simple. Cable ties mainly include sheet metal cards, fir tree-shaped cable ties, T-shaped cards, etc., see Figure 5.

Figure 5 Fixed cable tie style
Sheet metal card: This type of tie is suitable for fixing on materials that are difficult to drill holes or panels with large thickness, because it will damage the car body paint. Choose carefully for locations with high appearance requirements. If it must be used, it is recommended to use plastic type so as not to damage the paint surface of the car body.
Fir tree type cable ties: mainly used with round holes with diameters of 7mm, 9mm, 11mm, and 13mm.
T-type card: Mainly used in places where the wiring harness wiring space is small due to the installation of exterior decoration or where it is difficult to drill holes for the wiring harness itself.
3.2.3 Plastic trunking fixation
Sometimes due to the limitation of the wiring harness layout space, a separate plastic bracket needs to be specially developed to protect and fix the wiring harness. Generally made of PA66 material, this solution will greatly reduce the wear of the wire harness and avoid after-sales wear of the wire harness due to wear.

Figure 6 Schematic diagram of plastic trunking fixation

4 – Summary
The layout of automotive wiring harnesses is of great significance to the stable operation of automotive electronic and electrical systems. The principles of easy assembly, easy maintenance, safety and stability should be followed in the layout of automobile wiring harnesses. Combined with the characteristics of the car itself, rationally plan the wiring harness layout to continuously improve its scientificity and rationality. By discussing wire harness layout principles and fixing methods and providing application examples, wire harness wear can be avoided in advance and serve as a reference for wire harness design.