Full vehicle wiring harness seals (rubber parts), wrapping and fixing design

13/07/2021

Xiamen Kehan ​​Electronics is the first choice for wire harness and cable assembly processing.
Full vehicle wiring harness seals (rubber parts), wrapping and fixing design

(1) Design of harness seals (rubber parts)

Generally, rubber parts are used for transition when the automobile wiring harness passes through holes to play a role in wear resistance, waterproof, and sealing. It is mainly distributed in the following parts: the interface between the engine and the cab, the interface between the front cabin and the cab (2 places on the left and right), the interface between the four doors (or a rear door) and the compartment, and the inlet of the fuel tank.

Commonly used materials are generally natural rubber, neoprene, silicone rubber, EPDM and so on.

The characteristics of natural rubber: good elasticity and mechanical strength, excellent flexural resistance, high tear strength and good cold resistance. Disadvantages: poor aging resistance, not resistant to oil and ozone, and flammable.

The characteristics of neoprene: ozone resistance, heat aging resistance, oil resistance, etc. are good, with flame retardancy and self-extinguishing; but low temperature resistance is not good.

The characteristics of silicone rubber: good heat resistance, cold resistance and weather resistance; the disadvantage is that it is not resistant to oil. The characteristics of EPDM: weather resistance, ozone resistance, heat resistance, corrosion resistance, acid and alkali resistance and other properties are good, and it has high strength and high expansion rate; disadvantages: poor adhesion, and no natural elasticity Good rubber, poor oil resistance.

Comparatively speaking, the comprehensive performance of EPDM is better, so now the rubber parts for automobile wiring harnesses generally use EPDM materials.

(2) Harness wrapping design

The outer wrapping of the wire harness plays the role of abrasion resistance, flame retardancy, corrosion resistance, interference prevention, noise reduction, and appearance beautification. Generally, the following wrapping design schemes are formulated according to the working environment and space.

The engine wiring harness has a harsh working environment, so it is all wrapped up with corrugated pipes with high flame retardancy, waterproof, and high mechanical strength.

The working environment of the front cabin line is also relatively poor. Most branches and trunks are also wrapped with corrugated pipes with good flame retardancy, and some branches are wrapped with PVC pipes.

The instrument cable has a small working space and a relatively good environment. It can be wrapped with tape or patterned.

The door line and the roof line have a small working space and can be completely wrapped with tape, and some branches can be wrapped with industrial plastic cloth; the thinner roof line can be directly glued to the car body with sponge tape.

The chassis wire has many parts in contact with the car body, so it is wrapped with a corrugated tube to prevent the wire harness from wearing.

(3) Performance analysis of raw materials for dressing

1. Bellows

Corrugated pipes generally account for about 60% of wire harness wrapping, or even more. The main feature is good wear resistance, high temperature resistance, flame retardancy, and heat resistance in high temperature areas. The temperature resistance of the bellows is between -40-150℃. Its material is generally divided into two kinds of PP and PA. PA material is superior to PP material in terms of flame retardancy and wear resistance; but PP material is stronger than PA material in terms of bending fatigue resistance.

2. PVC pipe

The function of PVC pipe is similar to that of corrugated pipe. PVC pipe has good flexibility and resistance to bending deformation, and PVC pipe is generally closed. Therefore, PVC pipe is mainly used at the branch of the wire harness to make the transition of the wire smooth. The heat-resistant temperature of PVC pipes is not high, generally below 80°C.

3. tape

Adhesive tape plays a role in binding, wear resistance, insulation, flame retardancy, noise reduction, and marking in the wire harness, and it generally accounts for about 30% of the wrapping materials. Wire harness tapes are generally divided into three types: PVC tape, air flannel tape and cloth tape. PVC tape has good abrasion resistance and flame retardancy; temperature resistance is about 80℃, noise reduction is not good, and the price is cheaper. The material of flannel tape and cloth tape is PET. The flannel tape has the best wrapping and noise reduction properties, with a temperature resistance of around 105°C; the cloth tape has the best abrasion resistance, with a temperature resistance of up to 150°C. The common disadvantage of flannel tape and cloth tape is that it has poor flame retardancy and is expensive.

(4) Wiring harness fixing design

The central electrical box is generally fixed with steel strips, bolts, etc., or directly installed on the vehicle body with a fixed structure designed by the electrical box itself.

Each wire harness is generally fixed in the body hole with plastic ties, clasps, etc. Most of the body holes are round or elliptical holes, generally ranging in diameter from 5mm, 6mm, and 7mm.

The sheaths that are connected between the various wire harnesses are generally fixed collectively with sheath brackets and installed on the vehicle body.

Larger models such as Hiace and MPV have long and thick body lines, and are generally fixed on the body with guard plates to reduce vibration and noise