As people's requirements for the safety, comfort and economy of electronic appliances are getting higher and higher, and the electrical appliances and functions on electronic appliances are more and more, the wiring harness connecting various electrical devices is becoming more and more complicated. The multiple links of modern electronic and electrical faults have received more and more attention in the design and manufacture of electronic appliances. The following briefly describes the design process of the electrical and electronic harness.

1 schematic design and calculation

1.1 Draw electrical schematics according to the electrical configuration and technical requirements required by the Electrical Design Task Book.

1.2 Determine the insurance capacity and wire diameter according to the power of each electrical appliance. At the same time, load distribution is performed for each electrical subsystem to determine the total insurance capacity.

1.3 Calculate the wire diameter: according to the formula

Where: I———current, A; P———electric device power, W; U———voltage, V;

A———wire diameter, mm2; ρ———copper resistivity (about 0.0185 Ωmm2/m); L=wire length, m; Ud—allow maximum voltage drop loss.

Also consider the following:

a. The wire is too long to properly enlarge the wire diameter;

b. When the wire is connected to the electrical appliance after being transferred by a plurality of connectors, considering the voltage drop of the terminal is large, the wire diameter can be appropriately enlarged.

1.4 Different forms of wires have different allowable current and line voltage drops.

2 draw a three-dimensional wiring diagram

2.1 According to the position of each electrical device, determine the form of three-dimensional wiring, the current international common wiring form is generally E-type and H-type;

2.2 Simulate simulation of harness diameters in different areas;

2.3 Consider the sealing and protection of the wiring harness.

2.4 The fixing hole position of the wire harness is determined by the fixed form.

2.5 Theoretically, it is most reasonable to connect all the electrical components with one wire harness, but it can't be done at the time of actual loading. Therefore, the wire harness should be divided into blocks reasonably. In the case of convenient assembly, systematic design should be adopted as much as possible.

2.6 The design of the grounding point is very important in the design of the wire harness. Otherwise, it will cause signal interference and affect the function realization of some electrical appliances. According to the different models, multiple grounding points should be designed. The design of the grounding should meet the following points:

a. The weak signal sensor should be grounded separately and close to ensure the normal transmission of the signal;

b. Each ECU should be grounded separately to prevent interference;

c. Battery negative ground and engine, gearbox grounding should be carefully considered.

3 design two-dimensional wire harness diagram

3.1 Power distribution box (insurance and relay) is the core of the whole vehicle electrical, which plays the role of distributing load, centralizing power supply, saving space, simplifying wiring harness, reducing cost and facilitating maintenance. Generally, it can be designed to be 2 to 3 as needed. Some newly developed models of power distribution boxes have both electronic control functions; and the non-contact, non-fusible central control box will also have more and more market, and Jiejie is at the forefront.

3.2 The choice of wire color is based on ZBT35002 "Color of low voltage wire for electronic appliances".

3.3 selection of connectors

a. According to the wire diameter and the current through the selection of the connector;

b. The engine compartment is made of sealed connectors;

c. It is preferred to use the connector of the double spring type compression structure to reduce the contact resistance.

3.4 harness bundle method

a. The cab is generally wrapped with tape at intervals;

b. The instrument panel is generally tightly wrapped with tape;

c. on the floor or far from the engine, generally wrapped with flame-retardant bellows;

e. The inside of the door and the inside of the trunk door are generally wrapped with adhesive tape or industrial plastic cloth;

f. Some areas closer to the engine are insulated with a glass fiber sleeving or wire harness to wrap the glass ribbon.

In addition to the above, it should also be noted that the distance between the anti-theft ECU and the read-write coil prevents signal transmission attenuation; the electrical components of each transmission signal such as "oxygen sensor", "knock sensor", "read-write coil", etc. Use LE-SE signal lines or shielded lines.