Electrical wiring harness ground distribution and layout principles

1. Remove the load power (generally called ACC power supply) when starting the engine.

This part of the electric device generally has a large load and does not have to work when the car starts. Generally a bit of smoke power, air conditioning power, radio and television power supplies, and wiper power supplies.

2. Insurance calculation and selection principle Insurance is used to protect electrical equipment.

According to the power of electrical appliances, suitable insurance is selected. Wire harness wires are selected according to the insurance specifications to meet the appropriate wire gauges and wire diameters. Insurance is for electrical appliances. When the power is exceeded, the protective electrical device is blown and the harness is ensured to work properly before the fuse is blown. The overheating of the harness or the ignition of the fire cannot occur.

Slow-melting insurance is generally used for primary protection. It mainly protects mainline electrical equipment and is also used to protect motor headlights and other electrical appliances with large instantaneous power, etc., slow-melting insurance specifications, melting time, rated current, and general arrangement of insurance. The insurance is installed in the fuse box. There are usually two or three fuse boxes on the car. Therefore, it is necessary to select an appropriate fuse box according to the arrangement position of the electric appliance in order to reduce the number of wiring loops. When installing fuses or relays in the fuse box, the heat distribution must be balanced.

The fuses and relays have different currents in different load cycles. Concentrating fuses or relays used with high currents and/or high loads will cause hot spots. To avoid this situation, stagger different types of loads. Do not focus too much on relays that work continuously, interspersed with intermittently working fuses or relays. Do not over-concentrate the high-current insurance (such as 30A insurance), interspersed with low-current insurance among them.

3. Selection principle of wire diameter calculation for wire harness wire.

The voltage drop and heat generation should be taken into consideration when determining the cross-sectional area of the wire.

The current intensity of the power equipment is: I=P/U; the allowable voltage drop of the insulated wire, the cross-sectional area of the wire AA=IρL / UVL UVL is the voltage drop, the specific resistance of copper ρ = 0.0185Ωmm2 / m, L is the length of the wire

In selecting the ground point, we must separate the electronic ground from the power and separate the analog ground from the digital ground to avoid interference between the signals because their impact on the ground is different. This impact on the ground will affect the work of more sensitive electronic components.

But for the same controller, it can't separate the two too far, because if the distance between the two is too far, the potential difference between the two is greater, so there is a comparison of the ground potential for the same controller. Big differences, will also affect the use of electrical work.

Ground distribution and layout principles:

1) Take the nearest iron;

2) The grounding wires of the motor type (wiper motor, wash pump motor, warm air motor, solenoid valve, etc.) are individually grounded (distributed in the cab or on the frame);

3) The radio ground of the radio receiver is separately grounded (in the cab);

4) The weak signal sensor ground wire (instrument ground wire) should be grounded separately (connected to the negative pole of the battery) to ensure normal signal transmission;

5) ECU (airbag ECU, engine ECU) ground wire susceptible to interference when other parts work, respectively, to the negative battery cathode;

6) The ground wires between the grounding points on the frame are connected with each other. The grounding point is directly attached to the frame through the bolts and toothed washers.

7) The negative pole of the battery is separately connected to the engine and the body;

8) As far as possible, the crowbar points should be arranged in a place that is easy to maintain, so as to facilitate maintenance of the traction point;

9) The position of the grounding point should be given priority on the main beams. Unless special circumstances are allowed, it is not allowed to use brackets for grounding and to avoid bad grounding.

10) Do not place the grounding device in a serious splash area;

11) Do not arrange electrical components or grounding screws in the vicinity of fuel tanks and tubing.

12) The electronic fan needs to be grounded separately, and the high-power equipment is grounded separately. Fourth, the three-dimensional layout of the automotive wiring harness This process mainly simulates the direction and diameter of the harness of the entire vehicle, considering the sealing and protection of the through-hole of the harness, and the fixed hole position of the simulated harness. And fixed methods, etc., as shown. The main software for three-dimensional wiring is CATIA, UG, and PRO-E.

The general international wire harnesses are generally E-type and H-type. We can determine the form of three-dimensional wiring according to the position of each electrical device.

Then you can simulate the diameter of the wire harness in different areas, consider the sealing and protection of the through-hole of the wire harness, and determine the fixed hole position and the fixed form of the wire harness.

In the cab, it is usually wound with tape, and the wiring harness of the chassis and the engine room is generally added with corrugated pipe protection. Strengthen the anti-abrasion and heat-resistance capabilities. The connectors of this part must also be made of waterproof connectors.

In theory, it is fine that one wire harness connects all electronic components, but it is basically impossible in the automotive wiring harness design process. Therefore, the wiring harness should be divided into blocks, generally divided into engine wiring harness, engine compartment wiring harness, instrument panel wiring harness, floor wiring harness, door wiring harness, ceiling wiring harness, etc.

In the case of convenient assembly, system design should be adopted as much as possible.