Automotive Wiring Harness Design

Basics of Automotive Wiring Harness Design

The automotive wiring harness is the main body of the network of automotive circuits, and there is no automotive circuitry without the wiring harness. At present, no matter whether it is a high-level

luxury car or an economical ordinary car, the wiring harness is basically the same form of braiding, are composed of wires, connecting plug-ins and wrapping

wrapping tape.

Automotive wiring, also known as low-voltage wiring, is different from ordinary household wiring. Ordinary household wires are copper single-piston wires,

which have a certain degree of hardness. And car wires are copper multi-pistil wire, some soft wire as thin as a hair, a few or even dozens of soft copper wire wrapped

wrapped in a plastic insulating tube (PVC), soft and not easy to break.

Common specifications for wires in automotive wiring harnesses have a nominal cross-sectional area of 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 4.0, 6.0 and other

square millimeter wires, each of which has a permissible load current value, with wires used for different power equipment.

Take the wiring harness of the whole car as an example, 0.5 specification wire is suitable for instrument lamps, indicator lamps, door lamps, roof lamps, etc.; 0.75 specification wire is suitable for license lamps, front and rear lamps, brake lamps, etc.; 1.0 specification wire is suitable for turn signal lamps, fog lamps, etc.; 1.5 specification wire is suitable for the front headlamps, horn, etc.; the main power supply line, such as generator armature line, hitch line, etc. require Main power wires such as generator armature, hitch wires, etc. require 2.5 to 4 square millimeters of wire. This just means

general car, the key to look at the maximum current value of the load, such as the battery's hitch wire, positive power line is a special

car wires used separately, their wire diameter is relatively large, at least more than a dozen square millimeters, these "giant" wires

will not be programmed into the main wiring harness.

Before arranging the wiring harness to draw a wiring harness diagram in advance, wiring harness diagram and circuit schematic is not the same. An electrical schematic is a picture of the relationship between the

electrical parts, it does not reflect how the electrical parts are connected to each other, and is not affected by the size

shape of the electrical components and the distance between them. The harness diagram must take into account the size and shape of the electrical components and the

distance between them, but also to reflect how the electrical parts are connected to each other.

Wiring harness factory technicians according to the wiring harness diagram made of wiring harness wiring board, the workers in accordance with the provisions of the wiring board to cut the line wiring.

The main wiring harness of the whole car is generally divided into the engine (ignition, EFI, power generation, starting), instrumentation, lighting, air conditioning, auxiliary appliances, etc.

Part of the main wiring harness and branch harness. A whole vehicle main harness has a number of branch harnesses, just like the tree pole and tree branches.

The main wiring harness of the whole car is often centered on the instrument panel and extends from front to back. Due to the length of the relationship or ease of assembly and other reasons, some cars

the wiring harness is divided into the front harness (including instrumentation, engine, front light assembly, air conditioning, battery), the rear harness (taillight

assembly, license plate lamps, luggage compartment lamps), the roof harness (door, roof lamps, stereo speakers) and so on. Each end of the wiring harness will play

on the marking numbers and letters to indicate the connection object of the wire, the operator can see the marking can be correctly connected to the corresponding wires and electrical

pneumatic devices, which is particularly useful in the repair or replacement of the wiring harness.

At the same time, the color of the wire is divided into single-color wire and two-color wire, and the purpose of the color is also specified, usually by the car manufacturer's own standard.

China's industry standards only specify the main color, for example, the provisions of the single black dedicated to the hitch wire, red monochrome for the power cord, not to be confused.

The wiring harness is wrapped with woven wire or plastic sticky tape, for safety, processing and maintenance convenience, woven wire package has been eliminated, and now

is wrapped with sticky plastic tape. The connection between the harness and the harness, between the harness and the electrical parts, using the plug-in or wire lugs.

Connectors are made of plastic and are divided into plugs and sockets. The wiring harness is connected to the wiring harness with the plug, and the connection between the wiring harness and the electrical parts

connection with the plug or lugs.

With the increased functionality of the car and the widespread use of electronic control technology, there are more and more electrical parts, and more and more wires,

and the wiring harness becomes thicker and heavier. Therefore, advanced automobiles have introduced the CAN bus configuration, which utilizes a multiplexed transmission system.

Compared with the traditional wiring harness, the multiplexing device greatly reduces the number of wires and plug-ins, making the wiring easier

As people's requirements for automotive safety, comfort, and economy are getting higher and higher, the configuration of electrical appliances on the car, the function is also

more and more, so the wiring harness connecting the various electrical devices is also getting more and more complex, and has become a frequent cause of failure in the contemporary automobile.

Therefore, wiring harnesses are more and more complex, and have become the most common cause of automobile failures in modern times.

The following is a brief description of the automotive wiring harness design flow

program.

1 Schematic design and calculation

1.1 According to the "electrical design task book" required electrical configuration and technical requirements to draw the electrical schematic.

1.2 Determine the insurance capacity and wire diameter size according to the power of each electrical appliance, and at the same time, load distribution

allocation of each electrical subsystem to determine the total insurance capacity.

1.3 Calculate the wire diameter: according to the formula (see chart)

Where: I --- current, A; P --- power of electrical appliances, W; U --- voltage, V;

A --- wire diameter, mm2; ρ - copper resistivity (about 0.0185Ωmm2/m); L = wire length,

m; Ud - maximum permissible voltage drop loss.

Also consider the following cases:

a. The wire is too long can be appropriate to enlarge the wire diameter;

b. The wire is connected to the electrical appliances through a number of plugs transfer, consider the terminal voltage drop is larger, it can be appropriate to enlarge the wire

diameter.

1.4 Different forms of conductors have different allowable currents and line voltage drops.

2 Drawing three-dimensional wiring diagram

2.1 According to the location of the various electrical components, to determine the form of three-dimensional wiring, the current international common wiring form

Generally for the E-type and H-type;

2.2 simulation simulation of different areas of the wire harness diameter;

2.3 Consider the sealing of the wiring harness over the holes and protection.

2.4 Determine the fixing holes and fixing form of the wire harness.

2.5 Theoretically speaking, a harness to connect all the electrical components is the most reasonable, but the actual installation is simply can not do

, so the harness should be reasonably divided into pieces, in order to facilitate the assembly of the case, try to adopt a systematic design.

2.6 Hitch design is very important in the design of the wiring harness, otherwise it will cause signal interference, affecting the function of some appliances

function realization; according to the different models of the design into a number of grounding points, the design of the hitch should meet the following points:

a. Weak signal sensors should be a separate and nearby hitch, to ensure that the signal is normally transmitted;

b. The ECU should be a separate hitch, to prevent the normal transmission of the signal;

b. The ECU should be a separate hitch, to prevent the normal transmission of the signal, to ensure that the normal transmission of the signal. ECU should be a separate iron to prevent interference;

c. Battery negative iron and engine, transmission iron should be carefully considered.

3 Design of two-dimensional wiring harness diagram

3.1 Distribution box (fuse and relay) is the core of the whole vehicle electrical, play: distribution of loads, centralized power supply, saving

space, simplify the wiring harness, reduce costs and facilitate maintenance. Generally according to the need can be designed into 2 to 3. Some of the new

development models of the distribution box has been combined with the function of electronic control; and no contact, no fuse central control box will be more and more

more and more market, TJ is at the forefront.

3.2 The choice of wire color is based on ZBT35002 "the color of low-voltage wires for automotive use".

3.3 Selection of plugs

a. Selection of plugs based on the wire diameter and the size of the passing current;

b. Selection of sealed plugs in the engine compartment;

c. Priority is given to the selection of double-spring compression structure of the plugs to reduce the contact resistance.

3.4 Wiring harness wrapping

a. Inside the cab is generally wrapped with tape at regular intervals;

b. Inside the dashboard is generally tightly wrapped with tape;

c. On the floor or far away from the engine parts, generally use flame-retardant corrugated pipe wrapping;

e. Inside the door, inside the luggage compartment door is generally used in the form of adhesive tape or industrial plastic cloth wrapping;

f. Inside the door, inside the luggage compartment door is generally used in the form of adhesive tape or industrial plastic cloth wrapping;

f. Some of the areas closer to the engine are wrapped with heat-insulating fiberglass casing or wire harnesses wrapped with fiberglass tape.

In addition to the above, attention should also be paid to: anti-theft ECU and read-write the distance between the coils, to prevent signal transmission attenuation;

The electrical components of the signal transmission, such as "oxygen sensors", "shock sensor", "Read/write coils", etc. should be used LE-SE signal wire

or shielded wire and other wire types

Although the wiring diagram reflects the actual installation of electrical equipment in the car, but the wires on the map crisscross, increasing the difficulty of reading the map

In order to make the wiring diagram more close to the actual, often need to draw the wiring harness installation diagram, wiring harness installation diagram, the wiring harness installation diagram, the wiring harness installation diagram, the wiring harness installation diagram, the wiring harness installation diagram, the wiring harness installation diagram, the wiring harness installation diagram. Drawing the wiring harness installation diagram, wiring harness installation diagram to lay the wiring diagram in the same way

the relative concentration of wires, the formation of a wiring harness.

In the car, in order to install convenient and protect the wires, will be the same way many wires with cotton gauze compilation or polyvinyl chloride plastic tape package

Zip wire harness, known as the wiring harness.

The wiring harness diagram is a diagram of the entire vehicle circuitry based on the actual installation parts of the electrical equipment in the vehicle. On the map, the wires between the parts and components

appear in the form of wire harnesses, wiring harness diagrams and wiring diagrams are similar, but the map surface double wiring diagrams are simple and clear, close to the actual, the use of

, the applicability of the maintenance personnel is strong.

The wiring harness installation diagram does not describe in detail the wires inside the wiring harness, only the wires exposed on the outside of the wiring harness and connector numbered in detail,

and calibrated with letters. The wiring notation is highlighted for ease of wiring, and each terminal is accurately and precisely

marked with a serial number and color. Wiring harness diagrams are used in conjunction with circuit diagrams and wiring laying diagrams, which have great reference value. Therefore, modern automobile

repair manuals generally give circuit diagrams and wiring harness installation diagrams.

2, wiring harness installation drawing

As the wiring harness installation diagram is mainly to the formation of the wiring harness appears, fewer lines on the surface, the expression of the connection between the components has become

for its main content, in order to express the color of the wires, connectors, the terminal code, often supplemented by the wiring harness grouping and terminal number

table and wiring harness terminal wiring table.

(1) the content of the wiring harness

① the composition of the harness

The automotive wiring harness diagram consists of a number of wiring harnesses, there are main harnesses, sub-harnesses. On the diagram should show the composition of each harness, each harness

on how many branches, how many wires on each branch, the color of the wires and what is the stripe.

② wiring code and wiring signs

The number of electrical appliances on the car is large and complex, in order to make the correct connection, the connection points should be marked with wiring code and wiring signs, in order to

facilitate the connection.

③ Length of the harness

The length of the harness includes the total length of the harness, the length of each branch and the length of the interval between the two wire ends.

④ Splice

Since there are several wiring harnesses, the wiring harness and the wiring harness, the branch and the wiring harness, or the branch and the electrical appliance are connected through the socket,

it should be indicated how many wires on each socket, where each wire is located in the socket terminal hole, what kind of socket shape

is the shape of sockets, and whether the neighboring several sockets are The shape of the plug

and whether the neighboring plugs can be easily confused.

(2) wire color

① Terminology

Single-color wire: insulation surface for a color of the wire.

Bicolor wire: insulation surface for the two colors of the wire.

Main color: two-color wire in the area of the proportion of large color.

Auxiliary color: two-color wire in the proportion of the area of the small color.

② wire color and code

Wire color and code should be symbols of the provisions of Table 1-2-1.

Table 1-2-1 Color of the conductor

Line color Common abbreviation Chinese Line color Common abbreviation Chinese

Black BLK/B Black Light Green LT GRN Light Green

Blue BLU/BL Blue Orange ORG/ O Orange

Brown BRN/BR Brown Pink PNK/P Pink

Clear CLR/CL Clear Purple PPL/PP Purple

Dark Blue DK BLU Dark Blue Red RED/R Red

Dark Green DK GRN Dark Green Tan TAN/T Brown

Green GRN/G Green Violet VIO/ V Pink Violet

Gray GRY/ GR Gray White WHT//W White

Light Blue LT BLU Light Blue Yellow YEL/Y Yellow

③ Composition of wire colors

The color of a monochrome wire consists of one of the colors specified in Table 1-2-1.

The color of the two-color wire is composed of two colors in conjunction with Table 1-2-1.

The choice of wire color should be given priority to the selection of single-color, and then select the two-color.

④ Hitch wire

All kinds of automotive electrical hitch wire should be selected black wire, black wire in addition to the hitch, there is no other use.

⑤ wire color labeling

The labeling of the wire color using the color code, such as monochrome wire, the color is red, marked as "R";

dual-color wire, the first color is the main color, the second color is the auxiliary color, the main color is red, the auxiliary color is white, marked as "RW".

(3) wire cross-sectional area

The cross-sectional area of the wire according to the size of the working current to select, for some of the current is particularly small appliances, such as indicator circuits, in order to

to ensure that the mechanical strength should be, the cross-sectional area of the wire shall not be less than 0.5mm2.

The cross-sectional area of the wire is marked in the color code in front of the unit of millimeters is not labeled. Such as: 1.25R means that the cross-sectional area of the wire is

1.25mm2 of red wire; 1.0G/Y means that the cross-sectional area of the wire is 1.0 mm2 of the two-color wire, the main color is green, auxiliary

auxiliary color yellow