Product Design and Supplier Selection

Car wire harness is the main body of the network of car circuits. There is no car circuit without wire harness. At present, whether it is a high-end luxury car or an economical ordinary car, the form of wire bundling is the same on the base wood and consists of wires, connected plug-ins and parcel tape. Car wires, also known as low-voltage wires, "have been dissimilar to ordinary household wires. Ordinary household wires are copper single core wires with a certain hardness. The car wires are copper multi-core soft lines. Some soft lines are as fine as hair. Several or even dozens of soft copper wires are wrapped in plastic insulated pipes(polyvinyl chloride) and are soft and not easily broken.
1, car wire beam design process
The main process in the pre-design stage: the principle of the first-line beam for the calculation of the entire vehicle's electric load: the design of the fuse specification: the specification of the relay; the specification of the conductor; the design of the first-line beam structure for the specification of the plug.
After the end of the pre-design phase of the online beam, it enters the later stage of determination: the line beam trial production one adjustment design parameter one completes the product drawing one production inspection rule one sends the drawing and the inspection regulation one time.
1.1 Calculation of vehicle power load
Formula for calculating actual current consumption:
I = K1. K2. P / ve(ampere)
The rated operating voltage of a K1 appliance(vet is not its actual operating voltage. The actual operating voltage is assumed to be 14. 4, the actual current consumed by the appliance should be the rated current multiplied by the coefficient kI(K1 = 14. 4/ve)
K2 Working time of electrical appliances relative to engine working time coefficient
P1 Appliance Power Rating
Ve An electric appliance rated voltage(ve = 12 volts)
The purpose of calculating the entire vehicle's electric load: to determine the engine power, determine the battery specification(capacity), determine the total insurance and the road division insurance, and determine the cross-sectional area of the wire. The rated current value of all electrical equipment can not be superimposed here, but is calculated based on a certain proportional coefficient.
1. The 2 wire beam principle design is a connection method that connects all the electric equipment in the car through wires, fuses, relays, switches, and control devices, correctly connects to the power supply of the car, and ensures that each electrical equipment can work properly. Design. The essence of the principle design is the design of rational distribution, which is the design of how the electric energy of a car battery or generator is distributed to electric equipment in what way. There are mainly the following typical controls;
(1) Ignition switch control
Acc: The electrical equipment used to connect a car that has nothing to do with the running of the engine. Such as cigarette lighter, electronic clock, transceiver, rearview mirror and so on.
An: It is used to connect the electrical equipment related to the operation of the engine and the walking of the car. Such as ignition systems, generators, meters, wipers, scrubbers, warm air, air conditioning, post-defrosting, electric Windows, ahs systems, airbags, various controllers, etc..
(2) Dedicated switch control
The ground control is better than the fire control: In general, the switch control ground does not control the fire.
(3) Relay control
Control principle: small current control large current, timing control.
(4) Controller control
Power supply according to the principle of various controller wiring: clarify the definition of each pin of the controller, clarify the type of power supply required, and strictly adhere to the schematic wiring provided by the supplier.
1. 3 Finishing fuse specifications
(1) Characteristics of fuses
Temperature characteristics:
Fracture characteristics:
(2) Type of fuse
Slow melting fuse: used for motor circuits or large current circuits;
Fusible fuse: For general loop, wide range of application, low mature wood;
Bimetallic fuse: used for motor circuit, can be restored to use;
Fusible wire: between power circuit battery and total insurance:
Thermistor fuse: Used for motor circuits, especially for heating and plugging Motors, which can be restored to use and become wood high.
(3) The fuse selection principle
Total Insurance: The fuse current of the fuse is 1. 2-1. 5 times;
General load: The fuse current of the fuse is about 3 times that of the load rating current;
Motor Load: The fuse current of the fuse is about 4 times the rated current of the motor.
1. Establishment of relay specifications
By function: constant open type, constant closed type, conversion type
By structure: bullet type, inhalation type
Normal Relay(No Inhibitor)
New Relay(with Inhibitor)
Relay selection principle: determine the type according to the needs; The current value is four times that of electrical equipment.
Left and right; Consider the problem of anti-interference.
With more and more automotive electronic products, resistance to electromagnetic interference has become a must in electrical design.
The choice of a new type of relay can be released due to the relay's absorption and disconnection.
The raw reverse voltage minimizes interference with other electrical circuits.
Motor circuit: especially the motor circuit that is easy to produce a plug is preferred to the diode parallel type,
For drive circuit with LED lighting, electronic component control circuit, etc.. Preferred diode in parallel
Type. The relay's ability to release antivoltage is better than the resistor parallel type.
General circuit: minimal motor circuit selected resistance parallel type can be. Large parallel resistance value
Small pairs of suppression interference have different effects.
1.5 Determination of conductor specifications
(1} Type of wire
(2) Traverse characteristics
According to different specifications, conductors are allowed to have a maximum temperature of 80 °C or 120 °C.
The commonly used specifications of the wires in the car wire beam are wires with 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 millimeters. Each of them has a allowable load current value. Wire for different power electrical equipment. Take the vehicle line beam as an example, 0. 5 Specification line is suitable for instrument lights, indicator lights, door lights, top lights, etc.. 0.75 specification line is suitable for brand light, front and rear light, brake light, etc.. 1. The standard line is suitable for turning signals, fog lamps, etc.. I. 5 Specification lines are suitable for headlights, horns, etc.: The main power lines such as power generation electromechanical pivot lines, rail lines, etc. require 2.5 to 4 square mm wires. This is only for cars. The key is to look at the maximum current value of the load. For example, the battery's iron wire and the positive power cord are used alone by specialized car wires. Their wire diameters are relatively large, at least ten square millimeters or more. These "Big Mac" wires will not be incorporated into the main line.
(3) Traverse load flow
In Japan, Germany, and the United States, the current carrying meters are commonly used at 40 °C for different diameter wires(table 1).
(4) Matching of wires with insurance teaching
Take Hua Chen Zhonghua and Hai Shi models as an example:
According to the fuse diameter; The fuse value is less than the maximum current value sustained by the wire beam;
Large fuses do not protect small lines.
(5) Color of wires
Composition of the color of the wire: The color of the monochrome wire consists of one of the colors specified in the above table; The color of the two-color wire consists of the two colors specified in the above table; The selection of lead color should be preferred to a monochrome, repeated choice of double color.
2 Take the iron wire: The iron wire of various automobile electrical appliances should use the black wire. The black wire has no other use except for the iron.
3 Mark the color of the wire: The color of the wire is indicated by the color code, such as the monochrome wire, the color is red, marked as "R"; Two-color wire, the second 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.
4 Lead color selection base wood requirements
The wire meets the National color standard;
Line color uniqueness: There is no same color in the nearby socket: if the line color is only difficult, the line diameter distinguishes the large available color;
Limitations: that is, the same function(on the same socket) is best conducted with the same base color and different auxiliary colors, using two-color lines(two-thirds of base color and one-third of auxiliary color).
1.6 Determination of insert specifications
1) Specifications for pick-up parts(Table 2)
Plug-in for wire and parts: determined by electrical equipment.
The connection between the line and the line needs to be selected.
2) Plug-in Selection Process
According to the current and wire diameter of the connection terminal model, according to the number of wires to determine plug-in model.
1 There are reserved holes
2 Same function terminal: similar position of pin
3 arranged order: first outside and then inside
Reserve holes to disperse: conducive to heat dissipation
The principle of inserting feet: the separation between size and current
Design of Wire Beam Structure
1, determine fuse box and relay installation location(a premise for easy maintenance)
2, wire distribution design(according to the general layout requirements and reasonable segmentation)
3, wire size design
Main body size: short and short to reduce wire resistance(limited by the body);
Branch size: long is not short, considering assemblability;
Motion part: the head size should be sufficiently shaken