Golden Navigation: How much do you know about the waterproof design of automobile wiring harnesses?

    Shenzhen Jinhangbiao Electronics Co., Ltd.(SHENZHENKING HELMELECTRON CO., LTD.) was established in 2007. It is a national high-tech and dual-software certified enterprise, a senior member of the "China Satellite Navigation Association", an enterprise that has obtained the ISO9001 (04617Q13625ROS) quality management certification system, and is improving the IATF16949 automotive quality management system. The main business is the R&D, production and sales of Beidou satellite navigation and Internet of Things terminal application hardware, and the provision of www.BDS666.com logistics information intelligent system solutions.

The electrical safety of the entire vehicle has always been the most concerned issue for automobile manufacturers. The working environment in each area may have an impact on the wiring harness. Waterproofness is an element that cannot be ignored in the wiring harness design. So, the editor of Jinhangbiao will talk to you:Automotive wiring harnessDo you know about the waterproof design?

1. Wire harness winding method

There are four winding methods for vehicle wiring harnesses: semi-encapsulated winding, thick winding, double winding and 2/3 encapsulated winding. Among them, the whole vehicle wiring harness mostly adopts the semi-encapsulated winding method or the rough winding method. The so-called semi-encapsulated winding method involves bundling the wires into a bundle. The width of the insulating tape is about 1/2 times the width of the insulating tape. It is required that the middle wire cannot be seen and the adhesive surface of the insulating tape is not exposed. The rough winding method is to bundle the wires into a bundle. The spacing width of the insulating tape is 0 to 1.5 times the width of the tape. The width of the insulating tape is required not to be exposed.

The front cabin wiring harness and powertrain wiring harness are in direct contact with the outside world and require special waterproofing treatment. The wiring harness is required to use a semi-encapsulated winding method; under rain or car washing conditions, the door wiring harness has a high probability of contact with water, so the door wiring harness also needs special waterproofing treatment and requires a semi-encapsulated winding method to prevent water from entering the wiring harness and causing a short circuit that affects the safety of the entire vehicle. For wire harnesses that require special waterproofing treatment, the branches need to be cross-wound, and the wire harness must not be exposed; in the area where waterproof rubber rings and through-hole rubber sleeves are added, the wire harness is required to be semi-encapsulated and then double-wound on the rubber ring or rubber sleeve and wire harness.

Since wire harness winding is crucial to waterproofing, the wire harness manufacturer must be required to wind it as required to ensure the safety of electricity in the vehicle.

2. Selection of waterproof connectors

The main functions of the vehicle connector are twofold. One is to achieve docking with electrical devices to ensure the reliability of signal transmission, while ensuring insulation and preventing short circuits; the other is to use the positioning clips of the connector itself to prevent movement of the connector.

In principle, the connectors outside the cab must be waterproof. For example, the connectors in the engine compartment must be equipped with waterproof rubber sealing plugs. Due to the influence of sealing, waterproof connectors will generate heat at the contact points when working, resulting in temperature rise. It is generally believed that the working temperature of waterproof connectors is equal to the sum of the ambient temperature and the temperature rise of the contacts. Therefore, when choosing a waterproof connector, you must take into account its temperature resistance.

    3.密封

Sealing includes wire harness interconnection points, ground points and via protection. Due to the siphon phenomenon, the internal temperature of the electrical module will rise when it is working, and the temperature will gradually drop when it stops working, resulting in a reduction in the internal pressure. Water seeps into the wiring harness from loose seals, and penetrates into the electrical module along the gaps between the multiple strands of copper wires under the action of the pressure difference, causing electrical module failure. In order to deal with this phenomenon, in addition to using waterproof connectors, it is also necessary to seal the wiring harness internal points and ground points. The most common way is to use glued heat shrink tubing for sealing.

When the wire harness needs to pass through the body sheet metal hole, a rubber protective sleeve must be added for protection. It is recommended that the interference amount is within 40mm. For holes larger than 40mm, a flanging design is required, which mainly plays the role of protecting the wire harness, waterproofing and sealing.

Generally, there are two forms of via holes. One is a simple metal hole, which does not involve moving parts. At this time, attention should be paid to the relative position of the wire harness before and after the via hole, and the height of the outdoor part of the wire harness is required to be lower than the indoor wire harness. When moving parts are involved, the design of the rubber parts and interfaces must be fully considered to ensure that there is no interference and friction during the movement. The sealing of the rubber parts and the relative position of the hole should be considered to try to make the outdoor hole lower than the sheet metal hole connecting the indoor part.

4. Wiring harness layout protection

The most important thing about water entering the electrical system is that water penetrates into the electrical system by its own gravity. In addition to using conventional waterproof materials for protection, the waterproof function can also be achieved through reasonable three-dimensional layout. First of all, the grounding of the vehicle is a weak link in waterproofing, and it is easy for water to penetrate into the electrical system. Therefore, the layout of the vehicle's electrical appliances must be fully considered from the early stage of design. The installation point of the electrical appliances must be higher than the grounding point, and the installation direction of the grounding wire harness is downward. In this way, the optimization of the installation position can be used to effectively solve the problem of water's own gravity. Secondly, the wiring harness arrangement that is close to the vehicle drainage point, such as the door wiring harness and the rear protection wiring harness, will have rainwater dripping on the wiring harness, so the direction of this part of the wiring harness needs to be fixed and set to the lowest point, so that the water dripping on the wiring harness will flow out of the vehicle based on the wiring harness, thereby achieving the purpose of protecting the electrical system.

With the rapid development of automotive electronics, the number of electrical components in the vehicle is increasing day by day, and the safety and stability of the vehicle are becoming more and more important. As the safety design of the vehicle nervous system wiring harness, we must not only rely on traditional technology, but also constantly explore and learn new technologies. The above is the information brought to you by the editor of Shenzhen Jinhangbiao Electronics Co., Ltd.