Wire harness waterproofing is something that cannot be ignored in wire harness design.

1. Distribution of dry and wet areas of the vehicle

The car wading depth refers to the deep water that the car can pass through, which is also the safe depth. The area below the wading line and the engine compartment is called the wet area, and the area where the wiring harness installed in the cab, passenger compartment, luggage compartment, etc. does not require special waterproof protection is called the dry area. In order to improve the wading passability and safety of the whole vehicle, when designing the electrical system, the wading depth of the whole vehicle should be fully considered, and the key electrical equipment of the whole vehicle should be arranged in a dry area.

2. Wire harness layout

According to the distribution of dry and wet areas of the vehicle, we divide the vehicle wiring harness into the following parts: front cabin wiring harness, power component wiring harness, instrument wiring harness, interior wiring harness, ceiling wiring harness, four-door wiring harness and rear door wiring harness. According to the distribution of dry and wet areas of the vehicle, the front cabin wiring harness, power assembly wiring harness and four-door wiring harness are located in the wet area. This part of the money bundle needs to be protected against water, and the part connecting the interior should be sealed with rubber parts. Other wiring harnesses are located in dry areas, and the connectors do not need to be waterproof, but in order to prevent water from entering the room, corresponding waterproof treatment should also be done.

3. Waterproof design of wiring harness

3.1 Wire harness winding method

There are four types of winding methods for the vehicle wiring harness: semi-encapsulation winding method, coarse winding method, double winding method and 2/3 encapsulation winding method. Among them, the whole vehicle wiring harness mostly adopts the semi-encapsulation winding method or the coarse winding method. The so-called semi-encapsulation winding method, the wires are bundled into a bundle, the width of the insulating tape is about 1/2 times, and the bonding between the intermediate wires and the insulating tape is required to be invisible. The surface is not exposed; the coarse winding method is to bundle the wires into a bundle, the spacing width of the insulating tape is 0-1.5 times the width of the tape, and the bonding surface of the insulating tape is required not to be exposed.

The front cabin wiring harness and the power component wiring harness are in direct contact with the outside world, and require special waterproofing treatment. The wiring harness needs to be wrapped in semi-encapsulation; in the case of rain or car washing, the door wiring harness is likely to come into contact with water, so the door wiring harness also needs special waterproofing treatment , It is necessary to adopt the semi-encapsulation winding method to prevent water from entering the human wiring harness and cause a short circuit, which affects the safety of the whole vehicle. For wire harnesses that require special waterproof treatment, the branches need to be cross-wound, and the wire harness cannot be exposed; in the area where the waterproof rubber ring and the through-hole rubber sleeve are added, the wire harness is required to be half-wrapped first, and then double-wound the rubber ring or the rubber sleeve and the wire harness.

Because the wiring harness winding is very important for waterproofing, the wiring harness manufacturer must be required to wind it as required to ensure the safety of the entire vehicle.

3.2 Choose waterproof connector

There are two main functions of the vehicle connection plug-in. One is to realize the docking with electrical equipment to ensure the reliability of signal transmission, insulation and short circuit, and the other is to use the positioning card of the connection plug itself to prevent the movement of the connection plug.

In principle, the connectors outside the cab must be waterproof. For example, connectors in the engine compartment must choose connectors with waterproof rubber seals. Due to the effect of sealing, the waterproof connector generates heat at the contact point during operation, causing the temperature to rise. It is generally believed that the working temperature of the waterproof connector is equal to the sum of the ambient temperature and the temperature of the contact point. Therefore, when choosing a waterproof connector, temperature resistance must be considered. For example, the single-core waterproof connector of Electronic Valley has strong waterproof ability and the temperature rise is less than 30 degrees.

3.3 Sealing

Sealing includes wiring harness internal connection points, lap points and via protection. Due to the siphon phenomenon, the internal temperature of the electrical module rises when it is working, and the temperature gradually drops after it stops working, and the internal pressure decreases. The gap penetrates into the electrical module, causing the failure of the electrical module. In order to deal with this phenomenon, in addition to using waterproof connectors, it is also necessary to seal the connection points and overlapping points in the wiring harness. The more common method is to use tape heat shrinkable tube to seal.

When the wire harness needs to pass through the body sheet metal hole, a rubber protective cover must be added for protection. It is recommended that for holes larger than 40 mm, flanging design should be carried out, which mainly plays the role of protecting the wiring harness, waterproofing and sealing.

There are usually two types of vias, one is a simple treason hole, which does not involve moving parts. At this time, pay attention to the relative position of the wiring harness before and after the via, and the height of the outdoor part of the wiring harness is required to be lower than the indoor wiring harness; for the moving parts, it is necessary to fully Consider the design of the rubber parts and the interface to ensure that there will be no interference and friction during the movement. Consider the sealing of the rubber parts and the relative position of the hole, and try to make the outdoor hole lower than the sheet metal hole in the connection room.

3.4 Wire Harness Arrangement Protection

The main point of water inflow in the electrical system is that water penetrates into the electrical system by its own gravity. In addition to using traditional waterproof materials for protection, it can also achieve waterproof function through a reasonable three-dimensional arrangement. First, the grounding of the whole vehicle is a weak link, which is easy to allow water to penetrate into the electrical system. Therefore, the layout of the vehicle's electrical appliances should be fully considered from the early stage of the design. The installation point of the electrical appliance should be higher than the grounding point, and the grounding wire harness should be The installation direction is downward, so that the optimization of the installation position can effectively solve the problem of water seepage caused by the gravity of the water; second, the wiring harness is arranged close to the drainage point of the whole vehicle, such as the door wiring harness and the rear protection wiring harness, because there will be rainwater dripping To the wiring harness, so some wiring harnesses need to be fixed and set to a lower point, so that the water dripping on the wiring harness flows out of the vehicle by the wiring harness, so as to achieve the purpose of protecting the electrical system.

With the rapid development of automotive electronics, the number of vehicle electrics is increasing, 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, it is necessary not only to rely on traditional technologies, but also to constantly explore and learn new technologies. Technology.