Precautions for Automotive Wiring Harness Arrangement

With the continuous improvement of safety, comfort and environmental protection requirements of modern automobiles, the number of circuits and electricity consumption on automobiles have increased significantly, so how to arrange many wiring harnesses more usefully and reasonably in limited automobile space has become a problem faced by automobile manufacturing industry. This paper focuses on the settlement of automobile wiring harness, and gives a brief introduction to the layout matters needing attention.

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1. The fixing points of the wiring harness are reasonably arranged and reliably fixed. (1) According to the actual equipment orientation of the wiring harness on the whole vehicle, in order to avoid the drooping and displacement of the wiring harness, considering the components of the wiring harness, the fixing method and the convenience of the fixing orientation, the wiring harness It is necessary to have satisfactory and reasonable fixing points and fixing methods for fixing. (2) setting fixed points according to the direction of the wiring harness and the specific shape of the vehicle body, and the distance between the two fixed points is generally not greater than 300mm in a straight line distance without fulcrum; A fixed point can be arranged at the orientation of the obtuse angle inflection point; Two fixed points need to be settled at the right-angle inflection point; Acute angle inflection points are avoided in wire harnesses. (3) Select the type and size of the fixing buckle according to the shape and outer diameter of the wire harness, and meet the requirements of bearing the components of the wire harness. (4) Consider setting a fixed point in the position of the plug connector connected with other wiring harnesses and electrical devices at a suitable position not greater than 120mm in front of the plug connector. (5) Consider setting a fixed point on the trunk line in the fulcrum azimuth, and the distance between the fixed point and the fulcrum is not more than 100mm. (6) In the direction of fixing the buckled equipment, it is necessary to have a satisfactory space for disassembling the buckled equipment. 2. Neat appearance and bundled configuration (1) The wiring harness should be arranged along the edges and grooves (wiring grooves planned on the car body) to avoid the wiring harness bearing direct pressure. No wire harness shall be exposed in the cab; In the direction where the wiring harness can be observed, such as the engine room, set eye-catching attraction points or eye-catching colors, where the wiring harness of the equipment is not prominent or conspicuous. (2) Placement method: Place it horizontally and vertically on a checkerboard in the projection direction to avoid diagonal settlement. (3) It is uniform with the open space of the pipeline and reasonable with the open space of the surrounding parts. 3. The wiring harness should avoid dry contact with surrounding components. (1) It should not directly contact with the sharp edges of the vehicle body. First, there should be open space. Second, maintenance should be increased to avoid the sharp edges of the vehicle body damaging the external insulation layer of the wiring harness, resulting in short circuit accidents; (2) When the equipment is on vibrating or moving parts, the length should be reserved according to the practical situation. This reserved length is confirmed according to the vibration rugged of the component and the maximum movement stroke of the moving part. Ensure that the reserved length can prevent vibration from transmitting on the wire harness and prevent the wire harness from bearing tension. If the wiring harness is subjected to vibration transmission or tension for a long time, it may lead to virtual connection between the internal contacts/connector terminals of the wiring harness. Such as: the connection of engine wiring harness and engine compartment wiring harness. (3) The open space between the moving parts and the moving parts should be greater than 25mm, such as the open space between the wires and connecting rods of the wiper motor. (4) The distance from the exhaust manifold should be greater than 50mm. (5) The distance from the parts whose temperature is greater than 150 ℃ at the engine is greater than 50mm. (6) Do not use the same fixed point as the fuel pipeline and the brake pipeline. (7) Do not intersperse or contact with fuel lines and brake lines. Especially the wire harness connection part and the oil circuit connection part, so as to avoid fire caused by line surface damage, short circuit and oil transpiration density when conditions such as reach certain conditions.

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4. Anti-electromagnetic annoyance (1) It is necessary for the audio wiring harness to have an anti-electromagnetic annoyance method to ensure the signal-to-noise ratio of the signals collected by the audio system so that it can operate normally. (2) The engine control module signal line, surface signal line, ABS signal line and airbag signal line must have anti-electromagnetic disturbance methods (such as selecting twisted pair wire, shielded wire, etc.) to ensure the normal operation of each system. (3) Avoid the electromagnetic disturbance sources of parts, such as setting the orientation of some signal lines as far away from the disturbance sources as possible: electric horns, combustion coils, electrical appliances such as motors, etc. (4) The sensor signal power line should avoid the power line of high-current parts, and its distance should be greater than 300mm to avoid the signal being disturbed. (5) Reasonably arrange electrical appliances and shorten the length of signal lines. (6) The grounding wires of some key systems and important systems are arranged separately in one position to avoid being disturbed by other grounding wires. For example, airbag system, ABS, ECU engine control system and sound system are all two-wire system in the system, and the whole system selects one connection address. (7) Add shielding grounding to the shell of electrical appliances in the direction that is simply disturbed. 5. Consider the equipment processability and repair processability (1) Do not pull the wiring harness too tightly when using the equipment (especially when setting the wiring harness laterally), so as to avoid the moving vehicle in the fluctuating state, causing the orientation of the fixed point of the wiring harness to move wrong, resulting in the instant increase of the distance between the two fixed points, thus stretching the wiring harness to form the internal contact pull-off/virtual connection of the wiring harness, change of the wire parameters, or even break the wire. (2) After the wiring harness equipment is installed, there should be a satisfactory open space around it to ensure that it is not pressed by other components or squeezed by other components and their fasteners. Avoid grounding and other problems caused by the insulation layer of the wire harness being pinched, worn or broken. (3) Do not install connectors of the same type and color in close proximity. Avoid erroneous insertion and damage to wiring harness and electrical appliances during the equipment process. (4) The connector is arranged in the position where it is simply found, in the hand and in the position where things are simply operated. In order to facilitate inspection and repair, it is necessary to consider the length of wires carried by electrical devices according to the actual equipment conditions. If the electrical device equipment is in an easy-to-operate position on the surface, the wires can be omitted to directly couple the plug-in piece to the component; If the position of the electrical device is relatively shaded, and it is difficult to repair and disassemble in the later stage, the length of the wire carried by the electrical device can be appropriately increased according to the needs, so that the connector can be arranged in a position convenient for inspection and repair. (5) The rear connector of the engine equipment should be easily connected, which mainly refers to the connection between the engine wiring harness, the engine compartment wiring harness and the engine controller ECU. Because the engine is vibrating in the working state, in order to reliably connect the engine wiring harness, the cabin wiring harness and the ECU, it is not only necessary to appropriately increase the length of the engine wiring harness (generally the length is not less than 50mm), but also need to add a fixing point about 100mm in front of the connector at the end of the engine wiring harness, and fix it on the car body to avoid the transmission of engine vibration, resulting in loose connector and virtual connection of terminals. (6) The connector and the wiring harness can simply pass through the wiring hole of the vehicle body, which is convenient for the equipment and saves the time of the equipment. (7) If the wiring harness passes through the sheet metal hole from the inside of the cab to the outside, the external wiring harness must be lower than the passing hole to avoid the possibility of dripping or sprinkling liquid on the wiring harness and entering the room. (8) When the four-door wiring harness and the cockpit wiring harness are connected, the wire passing hole on the door is lower than the wire passing hole on the side wall of the body. If there is liquid on the rubber sleeve of the door wiring harness, it can only enter the door but not the cab. (9) Electrical equipment installed at the surface panel: the plug connectors connected to the surface panel wiring harness, such as the combination surface, switch panel, air conditioning panel, sound system and display screen, should reserve a satisfactory length according to practical requirements. According to the equipment depth of the electrical equipment, the orientation of the socket, the opening direction of the socket and the rear space behind the electrical equipment, and according to the convenience of operation, appropriately increase the reserved length of the connector on the wiring harness. Take the orientation of the connector in the middle orientation of the electrical equipment as an example: the reserved length L = the depth of the electrical equipment h + the width of the electrical equipment panel 0.7 B+100 (mm), where: the depth of the electrical equipment h-refers to the distance from the external decoration surface to the connecting socket of the internal electrical equipment after the completion of the electrical equipment; The width of the electrical equipment panel 0.7 B--refers to 0.7 times the height of the front decoration surface of the electrical equipment. (10) The reserved length of the four-door switch wiring harness, the ceiling light on the indoor ceiling and the reserved length of the switch wiring harness connector shall also be calculated with reference to the accounting method of the electrical equipment of the equipment at the surface plate. (11) Confirm the length of the acoustic antenna wiring harness. Reserve a satisfactory length when considering the equipment for the same requirements. (12) For other plugged-in wiring harness connectors, reserve the length considering the requirement of disassembling the wiring harness. Regarding the surface orientation of electrical devices and equipment, the equipment is under the seat (it can be operated by opening the seat), under the surface plate (it can be operated by removing the surface plate), or the insertion of the two wiring harness assemblies, the length is not reserved. Just refer to the practical measurement results and plug-in parameter planning. (13) It is necessary to leave space greater than twice the length of the plug in the insertion direction in the insertion direction of the plug. 6. Other precautions (1) The plug-in connected to the vibrating or moving parts must be fixed to avoid the transmission of vibration on the wire harness, resulting in virtual connection of the connection points in the wire harness and the terminals in the plug-in parts. (2) When considering automobile collision, the wiring harness cannot be kneaded. If the wiring harness is kneaded and broken, the internal short circuit will instantly cause a fire, causing further harm to drivers and passengers. (3) The plug-in should not be in direct contact with the external environment such as rainwater, oil, and should not be installed in the rainwater mobilization area or outside the car. When it is necessary to install it in the above areas, protective methods should be selected. Choose waterproof plug-in, use rubber stopper or rubber sleeve, add petroleum jelly to the plug-in, etc., to avoid water entering the plug-in and oxidizing the terminal surface. (4) It is necessary to ensure the reliability of rubber parts on the wiring harness. It is necessary for the wiring harness via rubber sleeve to be reliable. Under normal operation conditions, the rubber sleeve cannot be separated from the orientation of the equipment. (5) When using metal buckles, it is necessary to set plastic or rubber maintenance on the buckles. (6) The wiring harness at the wheels and under the floor needs to be protected accordingly. Avoid traveling on off-road, gravel roads or snow and ice roads in winter, and splash hard stones, ice and snow blocks to break the wiring harness. (7) Convenience of replacement of fuses and relays. When electrical appliances with high frequency are used, the positions of fuses and relays in the fuse box are arranged in positions that are easy to find and operate. VII. Maintenance of positive and negative electrodes of the battery (1) It is necessary to leave an open space of not less than 20mm between the positive electrode of the battery and the battery cover or engine cover to avoid short circuit, which will cause instantaneous high current discharge of the battery and constitute battery explosion. (2) It is necessary to set an insulating plastic maintenance cover or other maintenance methods that are not easy to deform on the positive terminal of the battery, so as to ensure that the maintenance methods are not easy to break away. (3) The open space of the positive cable and moving parts of the battery must be more than 25mm. (4) The positive cable of the battery should be planned shorter if possible. (5) It is necessary to use a plastic maintenance cover for the positive pole of the starter. (6) It is necessary to fix the negative electrode of the battery to the car body, and it is necessary to use bolts or nuts to fix the negative electrode, and then the engine and gearbox body are separately grounded to the car body. 8. Grounding wire installation (1) The connection address is installed on the chassis or body structural parts, that is, it is installed on a larger component, so that the component is large, the conductive cross section is large, the voltage drop is small, and there will be no large and significant connection address voltage difference, which affects the normal operation of electrical appliances in the circuit. (2) Do not install the connection address in the rainwater mobilization area or outside the car to avoid poor contact after the connection address is corroded. (3) the storage battery is grounded on the sheet metal component nearest to the storage battery; (4) Avoid setting the ground point of the grounding wire on the door (because the connection between the door and the car shell is a hinge connection, in order to avoid the increase of contact resistance and voltage drop). (5) Do not paint at the address location to avoid poor contact. 9. Heat dissipation of wiring harness and fuse box (1) For electrical appliances with high frequency of use, long working time, and large load current, the power wires should not be arranged together as much as possible, and the external bandaging method should be considered. When the internal temperature of the wire harness rises to a certain temperature, the external insulation layer of the wire will produce plastic deformation, bonding and other phenomena, and even cause short circuit. (2) When using electrical appliances with high frequency, long working time and large load current, the fuses and relays should be installed appropriately to increase the distance between them, or settle the distance from the fuses and relays with low frequency, short-term operation and small load current. Avoid heat mobilization, temperature rise of component parts, and reduce function and life.

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