Waterproof Design of Wiring Harness

The Wiring Harness is the nervous system of the vehicle's electrical appliances, and plays a vital role in the realization of the vehicle's electrical functions. The power safety of the whole vehicle has always been the most concerned issue of various automobile manufacturers. The working environment of each area may have an impact on the wiring harness. Waterproofness is a content that cannot be ignored in the design of the wiring harness. Design a brief analysis.
1. Wire Harness winding method
There are four types of winding methods for the vehicle wiring harness: semi-encapsulated winding, coarse winding, double winding and 2/3 encapsulated winding. 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 and the wires are bundled into a bundle, and the width of the insulating tape is about 1/2 times. Exposed; and the rough winding rule is to bundle the wires into a bundle, and the spacing width of the insulating tape is 0 to 1.5 times the width of the tape.
The front cabin wiring harness and powertrain wiring harness are in direct contact with the outside world, and special waterproofing treatment is required. The wiring harness requires a semi-encapsulated winding method; under the condition of rain or car washing, the door wiring harness has a high probability of coming into contact with water, so the door wiring harness also needs to be To do special waterproof treatment, it is required to adopt a semi-encapsulated winding method to prevent water from entering the wiring harness and cause a short circuit to affect the safety of the whole vehicle. For the wire harness that needs special waterproof treatment, its branches need to be cross-wrapped, and the wire harness should not be exposed; for the area where the waterproof rubber ring and the through-hole rubber sleeve are added, the wire harness is required to be semi-packaged and wound, and then the rubber ring or rubber sleeve is required. Double-wound with the wiring harness.
Since 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 vehicle's electrical use.
2. Selection of waterproof connectors
There are two main functions of the vehicle Connector. One is to realize the docking with electrical devices, to ensure the reliability of signal transmission, and to ensure insulation and prevent short circuits; the other is to use the connector itself with positioning clips to prevent the connector sports.
In principle, the connectors outside the cab should be waterproof. For example, the connectors in the engine compartment should be equipped with waterproof rubber sealing plugs. Due to the influence of sealing, the waterproof connector will generate heat at the contact point during operation, resulting in a temperature 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 rise of the contact. Therefore, when choosing a waterproof connector, it is necessary to take into account its temperature resistance characteristics.
3. Sealing
Sealing includes wiring harness interconnection points, grounding points and via protection. Due to the siphon phenomenon, when the electrical module is working, the internal temperature will rise, and when it stops working, the temperature will gradually drop, resulting in a decrease in the internal pressure. The gap between the multi-strand copper wires penetrates into the electrical module, causing the electrical module to fail. To deal with this phenomenon, in addition to using waterproof connectors, it is also necessary to seal the inline points and grounding points of the wire harness. The most common way is to use glued heat-shrinkable tubes to seal.
When the wire harness needs to pass through the body sheet metal hole, it must be protected by a rubber protective cover. It is recommended that the interference should be flanged for holes larger than 40mm, mainly to protect the wire harness, waterproof and seal.
In general, there are 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 that of the indoor wiring harness; for the moving parts involved The design of the rubber parts and the interface should be fully considered during the movement, so as to ensure that there is no interference and friction during the movement process, consider the sealing of the rubber parts and the relative position of the holes, and try to make the outdoor holes lower than the sheet metal holes in the connecting room.
4. Wire harness layout protection
The most important point of water inflow into electrical system is that water penetrates into electrical system by its own gravity. In addition to using conventional waterproof materials for protection, waterproof function can also be achieved through reasonable three-dimensional arrangement. First of all, the grounding of the whole vehicle is a weak link in waterproofing, and it is easy for water to penetrate into the electrical system. Therefore, the layout of the electrical appliances in the vehicle must be fully considered from the early stage of design. The installation point of the electrical appliance must be higher than the grounding point, and the grounding wire harness must be The installation direction is downward, so that the optimization of the installation position can be used to effectively solve the problem of water seepage caused by the gravity of the water itself; the second is the wiring harness arrangement that is closer to the drainage point of the whole vehicle, such as the door wiring harness and the rear protection wiring harness, because there will be raindrops. It falls on the wiring harness, so this part of the wiring harness needs to fix its direction and set the lowest point, so that the water dripping on the wiring harness flows to the outside of the car relying on the wiring harness, so as to achieve the purpose of protecting the electrical system.