Automotive wiring harness's Design
The function of the wire harness in the whole vehicle is to transmit or exchange the power signal or data signal of the electrical system, and realize the functions and requirements of the electrical system.
Design process and manufacturing process of wire harness
(1) The electrical layout engineer shall provide the functions, electrical loads and related special requirements of the vehicle electrical system. The state of electrical equipment, installation position, and the docking form of wire harness and electrical equipment.
(2) According to the electrical function and requirements, draw the electrical schematic diagram and circuit diagram of the whole vehicle.
(3) According to the electrical principle circle, the energy of each electrical subsystem and loop is distributed, including the distribution of power grounding wire and grounding point.
(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 wiring harness and the direction in the vehicle; Determine the external protection form of wire harness and the protection of via hole; Determine the fuse or circuit breaker according to the power load; Then determine the wire diameter according to the number of fuses or circuit breakers; According to the function of electrical equipment, determine the line color of electric wire according to relevant standards; According to the connector of the electrical equipment itself, determine the types of terminals and sheaths butted on the wiring harness.
(5) Draw two-dimensional wiring diagram and three-dimensional wiring diagram.
(6) According to the approved 3D wiring harness layout, check the 2D wiring harness diagram. Two-dimensional wiring diagram can only be drawn after it is accurate, and trial production can be carried out after it is approved.
Key points of two-dimensional harness diagram design
Junction box
Distribution box (fuse and relay) is the core of vehicle electricity, which plays the role of distributing load, centralized power supply, saving space, simplifying wiring harness, reducing cost and facilitating maintenance. Generally, it can be designed into 2~3 according to needs. The distribution box of some newly developed models has electronic control function; Moreover, there will be more and more markets for non-contact and fuse-free central control boxes.
Selection of conductor
(1) The selection of conductor color should be based on the color of low-voltage wires for automobiles.
(2) The ambient temperature around the engine is high, and there are many corrosive gases and liquids. Therefore, wires with high temperature resistance, oil resistance, vibration resistance and friction resistance must be used.
(3) The conductor on the luggage compartment cover should keep its elasticity at low temperature, so the 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 good.
(5) Weak signal sensors should use shielded wires, such as sensors in EFI system, CAN loop in ABS and wheel speed sensors; Speaker loop of radio, related sensors in airbag (such as collision sensor), etc.
(6) The requirements for the bending of doors are high.
Selection of connectors
(1) connectors should be selected to ensure good contact with electrical equipment, minimize contact resistance and improve reliability.
(2) According to the cross-sectional area and current of the conductor, select the joint reasonably.
(3) Due to the high temperature and humidity in the engine compartment, and the existence of various corrosive gases and liquids, waterproof sheaths must be selected. If the same sheath is used in the same harness, the colors must be different.
(4) In order to reduce the types and quantities of sheaths used for wire harness docking, mixed parts are preferred to facilitate assembly and fixation. Terminal connectors for airbags, ABS, ECU, etc. For those with high performance requirements, it is best to choose gold-plated connectors to ensure safety and reliability.
Bundling method of wire harness
The outer packaging of the wire harness has the functions of wear resistance, flame retardancy, corrosion resistance, anti-interference, noise reduction and beautification. Generally, according to the working environment and space size, the following package design scheme is formulated. The selection principles are as follows:
(1) The working environment of the engine harness is harsh, so it is completely wrapped with corrugated pipes with high flame retardancy, water resistance and high mechanical strength.
(2) The working environment of the engine cabin line is also poor. Most branch pipes are also wrapped with corrugated pipes with good flame retardancy and high temperature resistance, and some branch pipes are wrapped with PVC pipes.
(3) The instrument line has a small working space and a relatively good environment, so it can be wrapped with tape or flowers.
(4) The working space of the door line and the ceiling line is small, so it can be fully covered with adhesive tape; The thinner roof line can be directly adhered to the car body with sponge tape.
(5) Because there are many contact parts between the chassis line and the car body, it should be wrapped with bellows to prevent the harness from being worn.