As a key component of new energy vehicles, the three-dimensional layout of high-voltage wiring harnesses directly affects the performance, safety and reliability of vehicles. Reasonable three-dimensional layout can ensure the stability of the wiring harness, easy assembly and maintenance, while improving the overall efficiency of the vehicle.
1 Classification of high voltage wiring harness
1.1 Charging wiring harness
1. Fast charging harness: The fast charging wiring harness is specially connected to the fast charging port and high voltage battery, and its mission is to achieve the rapid supplement of electric energy.
2. Slow charging harness: Slow charging harness is used to connect AC charging ports and high-voltage batteries. In home charging piles or some low-power AC charging scenarios, slow charging harness plays an important role.
1.2 Power cable harness
The power cable harness connects the battery and the motor, which can be called the "highway" for the power output of new energy vehicles.
Among them, the motor controller cable is an important part of the power harness, which connects the high voltage box and the motor controller, the motor controller is responsible for adjusting the speed and torque of the motor, and the motor controller cable bears the high voltage transmission of the battery to the motor controller, and then the motor controller is assigned to the motor.
1.3 High voltage accessory wiring harness
The high voltage accessories cable harness connects the high voltage PDB to other high voltage components.
For example, to provide high voltage for the air conditioning compressor, so that the air conditioning system can normal cooling or heating, in the hot summer to bring cooling to the car, in the cold winter to create a warm environment;
Power accessories such as PTC heaters (positive temperature coefficient thermistor heaters) for functions such as window defrosting and seat heating.
2 High-voltage wiring harness three-dimensional layout design process
2.1 High voltage harness development process
Before introducing the 3D design process of high voltage wiring harness, it is necessary to talk about the overall development process of high voltage wiring harness, as shown in the following figure. The key is to understand what needs to be done before three-dimensional wiring.
2.2 High voltage wiring harness 3D design process
The 3D design process of high voltage wiring harness requires the help of professional software, such as CATIA, Proe, UG, solidwork, etc. Overall, the 3D design process for high voltage wiring harnesses is as follows:
1. Electrical equipment layout
The first step in the three-dimensional layout of high-voltage wiring harnesses is the layout of high-voltage electrical equipment, which requires the chief layout engineer to take the lead and complete with the engineers of each system.
The whole vehicle electrical system is divided into different modules according to the position, such as chassis, instrument panel, engine, transmission and other modules. In the layout process, it is necessary to consider the actual location of each electrical equipment, such as drive motor, power battery, PTC heater, compressor, DC/DC, battery, etc., but also to identify the DC/DC, power battery, distribution box control components concentrated location.
2. Wiring direction design
Determine the wiring direction according to the electrical equipment layout plan.
When determining the direction of wiring harness, it is necessary to design according to the principle of automotive electrical wiring harness layout, and check the direction scheme to ensure its rationality. For example, the high-voltage wiring harness is directed inside the vehicle skeleton, which helps to protect the harness and improve the safety and reliability of the harness.
3. Fixed mode and structure design
The fixing method is determined according to the direction of the wire harness, and the strength and interference are checked.
When designing the fixed method and structure, assembly should be considered, and too many processes should not be added to the assembly process while pursuing fixed reliability. In the design process of wire harness fixed structure, common standard parts are used as far as possible, and the types of standard parts are as few as possible to reduce the use of special tools in assembly and maintenance.
4 Principles of three-dimensional layout of high-voltage wiring harnesses
4.1 Proximity principle
The principle of proximity of wiring harnesses means that the path of high voltage wiring harnesses of new energy vehicles should be reduced as much as possible when arranging high voltage wiring harnesses. This not only avoids the pressure drop caused by too long path, but also conforms to the design concept of reducing cost and weight.
4.2 Easy Assembly
The overall design and fixing method of automobile wiring harness should adhere to the principle of easy assembly to ensure simple installation and operation.
Fixed connector installation: Reserve the length of the fixed connector installation to ensure sufficient installation space for easy operation.
Fixing of wiring harness and its components: Leave a safe space for fastening tools, with a gap of at least 50mm from the center of the nut.
Installation and fixing of wire harness fasteners: The installation and fixing of wire harness fasteners should be selected in a suitable position and the number should be as small as possible.
4.3 Good maintainability
The principle of good maintainability means that the convenience of late maintenance management should be fully considered in the arrangement of the automotive wiring harness, to ensure that once the wiring harness fails, it can be repaired in the shortest time, and effectively avoid the impact of maintenance on other components.
Joint layout and fixing: The joint should be arranged in a place within reach, and the other end of the connector inserted and removed by one hand should be fixed.
Avoid misinsertion and reserved length: The connectors on the same part should be avoided, and the end wiring harness should be reserved length. For example, the high-voltage wire near the tail of the connector should not be bent or rotated, and should be fixed within 120mm or less.
Fuse box harness allowance: The harness of the fuse box should have enough margin so that it can have enough operating space during maintenance.
4.4 Safe and Reliable
Ensuring the safety and stability of the electrical system and ensuring the normal use of automotive electrical equipment is the ultimate purpose of automotive wiring harness layout.
The selection of the fixed position of the cable harness: Generally, the cable is fixed in the area that is not easy to touch, such as edges and grooves, to avoid damage to the cable harness caused by external forces.
Avoid cable bending: Leave enough space when it is necessary to bend, and special fixing must be done to the bending zone, and pay special attention not to damage.
Avoid cable damage: Take special protection on cables that need to pass through holes, such as protective covers or wrapping tapes, to prevent cable wear. In the event of a collision, ensure that the wiring harness is not squeezed to prevent the wiring harness from breaking and causing a short circuit.
Reserve a good design margin: for the main branch, the bending radius of the wiring harness should be large enough to avoid too small bending space affecting the wiring harness assembly. When assembling the wiring harness, do not pull it too tight to avoid mispositioning the fixed point of the wiring harness when the driving vehicle is in a bumpy state.
Avoid vibration area: When the high-voltage wiring harness is arranged and fixed, it should avoid violent vibration areas, such as air compressors, water pumps and other vibration sources. When it is impossible to avoid due to structural arrangement and other factors, a high-voltage wire with sufficient margin should be left according to the vibration amplitude of the wiring harness arrangement and the maximum motion envelope of the moving part, so as to avoid the tension or tension of the wiring harness.
Avoid high temperature areas: In the layout of wiring harness should avoid the high temperature parts on the vehicle, such as air compressor, brake pipe, steering oil pump, oil pipe, etc., to avoid high temperature to melt the wire or accelerate aging, resulting in the risk of exposing the core wire and the frame short connection.
Pay attention to the bending radius of the high-voltage wire: pay attention to the bending radius of the high-voltage wire harness when it is arranged. If the high-voltage wire harness is bent too much, the resistance of the bent part of the wire harness will increase, resulting in an increase in line voltage drop. At the same time, excessive bending time for a long time will cause aging and cracking of wire harness insulation rubber. Generally, the minimum inner bending radius of a high-voltage wire should not be less than four times the outer diameter of the wire. The high-voltage cable harness at the tail of the high-voltage connector must be kept straight. The high-voltage cable near the tail of the connector must not be bent or rotated.
Sealing and waterproof design of high voltage cables: To improve the mechanical protection and dustproof and waterproof performance of high voltage wiring harnesses, protective measures such as sealing rings are adopted between the inserted connectors and the positions where the connectors are connected to the cables to prevent water vapor and dust from entering, so as to ensure the sealing environment of the connectors and avoid safety problems such as short circuit, spark, and leakage between the contacts.
4.5 Beautiful Layout
Hidden or horizontal vertical: the wiring harness layout should be beautiful, you can choose to hide or horizontal vertical layout. The direction of the wiring harness should be consistent with the direction of the attachment, in the projection direction, according to the horizontal horizontal vertical arrangement, try to avoid the oblique direction arrangement, avoid cross arrangement, and the surrounding wiring harness, water pipe, gas pipe, oil pipe and other directions as unified as possible, the overall appearance.
5 Precautions for three-dimensional layout of high-voltage wiring harnesses
The three-dimensional layout of high-voltage wire harnesses is a complex and critical process, which requires comprehensive consideration of many factors. In addition to following the basic layout principles, there are the following precautions:
1. The HV wiring harness should be avoided from the passenger compartment as far as possible. If the HV wiring harness needs to be connected to the front compartment and trunk due to design requirements, the HV wiring harness can be routed from under the vehicle chassis through the body sheet metal hole, which is conducive to the EMC design of the HV wiring harness.
2. Avoid wiring with low-voltage wiring harnesses to prevent interference with low-voltage wiring harnesses. Try to avoid cross-wiring with high-low-voltage wiring harnesses 100mm apart from parallel wiring harnesses (unless EMC is not affected);
3. The high pressure wiring harness is separated from the fuel pipe by at least 100mm;
4. The distance between the associated positive and negative wires should be maintained 20mm (measured by the distance from the outer edge of the shield layer);
5. The associated wire length difference is not allowed to exceed 35mm;
6. The gap between the high voltage wiring harness and the stationary parts is at least 10mm;
7. The gap between the high voltage wiring harness and the moving parts is at least 25mm;
8. The distance between the outlet end of the high voltage connector and the first fixed point is not more than 100mm, and the distance between the adjacent fixed points is generally not more than 150 ~ 200mm;
9. The wiring harness should be more than 200mm away from the heat source (such as engine exhaust pipe, pump copper pipe, etc.). If the requirements cannot be met, the wiring harness should be wrapped with flame retardant thermal insulation cotton, or the heat insulation board should be added near the wiring harness.
10. Try to avoid the area with large deformation after the collision of the body to prevent the high voltage of the body from being cut by the sheet metal or the insulation layer from being damaged after an accidental collision. For example, try not to line the front and rear anti-collision beams, side sheet metal and door.
11. The associated high-voltage wiring harnesses (such as the motor three-phase line or the main power battery pack line) must be unified and symmetrically arranged.
12. In the event of a collision, the vehicle must ensure that the high-voltage wiring harness will not be squeezed to prevent the wiring harness from breaking and causing short circuit.
13. The bending radius of the wiring harness should not be too small, which should cause the sealing of the connector to fail and the insulation of the conductor to be damaged. The appropriate bending radius of the wire is shown in the following table.
Note: Outer diameter refers to the diameter of the outermost insulating skin; Some manufacturers of high voltage large square wire bending radius can be less than the above table requirements, need to determine the bending radius and test requirements and methods with the supplier.
6 Summary
In order to do a good job in the 3D design of high voltage wiring harnesses, it is necessary to be familiar with the parts related to the high voltage system, familiar with the development process of high voltage wiring harnesses, master the layout principles related to high voltage wiring harnesses, precautions and 3D design software.