The automobile wire harness for car

2022-01-24

Basic knowledge of automotive wiring harness design

Design of automobile wiring harness
The role of wire harness in the vehicle is to transfer or exchange power signals or data signals of the electrical system to achieve the functions and requirements of the electrical system.

1. Wiring harness design process

1. The electrical layout engineer shall provide the functions, electrical loads and related special requirements of the vehicle electrical system. The state, installation position of the electrical parts, and the form of wiring harness docking with the electrical parts.
2. According to the electrical functions and requirements, draw the electrical schematic diagram and circuit diagram of the whole vehicle.
3. Distribute energy to each electrical subsystem and loop according to the electrical principle circle, including power supply lap wire and ground point distribution.
4. According to the distribution of electrical components in each subsystem, determine the wiring form of the wiring harness, the electrical components connected by each wire harness and the direction of the vehicle; Determine the outer protection form of wire harness and through hole protection; Determine fuses or circuit breakers according to electrical load; Then determine the wire diameter according to the amount of fuse or circuit breaker; According to the function of electrical parts, according to the relevant standards to determine wire color; Determine the type of terminal and sheath connected to the wiring harness according to the connector of the electrical part itself.
5. Draw the 2D and 3D wiring harness diagrams.
6. According to the approved 3D wiring harness layout drawing, check the 2D wiring harness drawing, the 2d wiring harness drawing can be issued if it is accurate, and trial-produce and produce after being approved.
1.1: Key points of two-dimensional wiring harness diagram design

1.1.1 distribution box

Distribution box (insurance and relay) is the core of the electric vehicle, which plays a role in load distribution, centralized power supply, space saving, simplifying wiring harness, reducing cost and convenient maintenance. Generally according to the need can be designed into 2~3.

1.1.2 Selection of wire

1. Selection of wire color shall be carried out according to "Color of low-voltage Wire for Automobile".
2. The ambient temperature of the engine is high, and there are many corrosive gases and liquids. Therefore, high temperature resistance, oil resistance, vibration resistance, friction resistance wire must be used.
3. The conductor on the trunk cover should keep its elasticity at low temperature, so cold elastic conductor should be selected to ensure its normal operation.
(4) The wire on the automatic transmission must be resistant to high temperature and hydraulic oil, and its temperature stability is better.

1. Weak signal sensor should use shielded wire, such as the sensor in efI system, CAN loop and wheel speed sensor in ABS; SPEAKER loop of radio, relevant sensors in airbag (such as collision sensor), etc.
2. High bending resistance of the door inner line is required.
1.1.3 Selection of connectors

1. The connector should be selected to ensure good contact with the electrical component, so as to minimize the contact resistance and improve reliability.
2. Select a connector based on the cross-sectional area of the wire and the current.
3. The jacket for docking in the engine cabin must choose waterproof jacket because of the large temperature and humidity in the cabin and the existence of a lot of corrosive gases and liquids. If same kind of sheath is used in same wire harness, its color must have distinction.
4. In order to reduce the type and quantity of sheath used for wiring harness butt, the mixed parts should be preferred to make assembly and fixation convenient. For airbag, ABS, ECU and other terminals with high performance requirements, it is best to choose gold-plated parts to ensure safety and reliability.
1.1.4 Wire harness wrapping method

External wrapping of wire harness plays the role of wear resistance, flame retardant, corrosion prevention, interference prevention, noise reduction and beautification. Generally, the following wrapping design scheme is formulated according to the working environment and space size. The selection principles are as follows:

Engine wiring harness working environment is bad, so all with high flame retardant, waterproof, high mechanical strength of the bellows wrapped.
Engine room line working environment is relatively poor, most branches are also wrapped with flame retardant, high temperature resistant bellows, part of the branch wrapped with PVC pipe.
Instrument line working space is small, the environment is relatively good, available tape or flower wrapped.
Door line and roof line work space is small, can be fully wrapped with tape; The thinner roof line can be attached directly to the body with sponge tape.
The chassis wire is wrapped with bellows to prevent the wire harness from wearing because there are many parts in contact with the car body.
1.2: Main points of 3d wiring diagram
According to the position of each electrical piece is different, determine the form of 3 d wiring, the wiring form of general on international at present is E and H model commonly.
The diameter of wire harness in different areas is simulated.
Consider the sealing and protection of wire harness through hole.
The fixed hole position and fixed form of wire harness are determined.
Theoretically speaking, a wire harness to connect all electrical parts is the most reasonable, but the actual loading is simply not done, so the wire harness should be reasonably divided into blocks, in the case of convenient assembly, as far as possible, systematic design.
Lap point design is very important in wire harness design, otherwise it will cause signal interference, affect the function of some electrical appliances;
Others: In addition to the above process, wiring harness design should be carried out. There are many more principles involved that must be considered.

All wiring harnesses placed near the moving parts shall have a minimum clearance of 50mm. The gap between the harness mounted on the driveline and the part not mounted on the driveline shall be at least 19mm under the maximum assembly tolerance of the harness and under other operating conditions to ensure the full range of motion of the moving part/assembly.
The wire harness between two relative moving parts must be fixed to each part, and the connecting length of the wire harness should be at least 25mm larger than the maximum replacement distance of the two parts.
The minimum clearance between the harness and adjacent parts that are not associated with the harness is 6mm, unless the harness is already fixed to the part or there is already a shield between the harness and nearby moving parts.
The noise generated by wire harness to the headrest of the driver's seat should not be greater than 50dB, and the frequency should be 50-15000Hz.
To ensure that the rubber plugs on the cable harness function normally, the plug mounting holes must meet relevant requirements.
The rubber plug shall be designed to fit fully into the sheet metal hole with less than 100N mounting force.
Harness fasteners that require manual assembly to be pressed into the seat, as well as holes and slots for cable clips to be inserted, should be designed for the following maximum mounting forces; For fixed parts pressed with fingers, the operating force is 45N; For fixed parts pressed by hand, the operating force is 75N.
The harness branches must be sufficiently relaxed (greater than 25mm under the minimum length of the harness) so that they do not have to add load to the connected sensors or anything else.
In order to prevent the ground lug from damaging any wiring harness on the trunk, the minimum clearance between the ground lug on the trunk and the trunk should be maintained at 25mm during loading.