With the continuous progress of electric vehicle technology, automobile manufacturers have launched a series of new energy vehicle products in recent years, such as pure electric vehicles, hybrid electric vehicles and hydrogen fuel vehicles.
At the same time, the technology of electric vehicle is gradually improving, and electricity has become the main power source to replace traditional fuels.
In the electric vehicle, as one of the main connection and transmission systems for vehicle power supply and function realization, the high-voltage wiring harness is facing challenges in design and layout.
- High-voltage wiring harness design
Harness dual-rail design/High-voltage connector selection design/High-voltage harness shielding design
01
Harness dual rail design
In the design of high voltage wiring harness of electric vehicle, the double rail system design is adopted.
Because the output voltage of the power battery is high voltage, which is beyond the safe voltage range of the human body, the vehicle body can not be used as the grounding point of the high-voltage wiring harness. On the high-voltage wiring harness system, the DC high-voltage circuit must be designed in strict accordance with the dual-track system.
Common high-voltage wiring harness can be divided into high-voltage wiring of driving system, high-voltage wiring of power battery, high-voltage wiring of charging seat, high-voltage wiring of air conditioning compressor and high-voltage wiring of steering oil pump.
02
Selection and Design of High Voltage Connector
The selection of high voltage connectors is also an important consideration in the design process. High-voltage connector is mainly responsible for the connection and transmission of high voltage and high current, which plays an important role in ensuring human safety. Functions such as high voltage resistance, protection grade, loop interlock and shielding shall be considered during selection.
03
Hield design of high voltage wire harn
The high voltage wiring harness also needs to consider the shielding design. Because the high voltage wiring harness will produce strong electromagnetic interference when transmitting high voltage electricity, it is necessary to use wires with braided shielding mesh, and when selecting high voltage connectors, try to select connectors with shielding design to suppress the electromagnetic interference produced by high voltage wiring harness.
2 Layout design of high voltage wiring harness
Harness dual-rail design/HV connector selection design/HV harness shielding design
Layout principle of high voltage harness
Principle of nearby arrangement:
When arranging the high-voltage wiring harness of new energy vehicles, the path of the high-voltage wiring harness should be reduced as much as possible, which not only avoids the pressure drop caused by the long path, but also conforms to the design of cost reduction and weight reduction.
Safety principle layout:
In addition to the principle of proximity, the layout of high-voltage wiring harness should also meet the principles of concealment, safety collision regulations, maintenance convenience and so on, and also need to effectively protect the high-voltage wiring harness. The unreasonable arrangement of high-voltage wiring harness may lead to electric leakage, fire and endanger the safety of drivers and passengers.
Layout type of high-voltage wiring harness
Layered arrangement and parallel arrangement are widely used in the arrangement of high-voltage wiring harness. These two methods are based on the high voltage wiring harness and low voltage wiring harness separately to reduce the electromagnetic interference of high voltage to low voltage communication.
(1) Layered layout design
Layered arrangement, as its name implies, is to arrange the high-voltage wiring harness and the low-voltage wiring harness at a certain distance, so as to avoid the electromagnetic interference generated by high voltage on the power supply and signal transmission of the low-voltage control unit. Layered layout design diagram of high and low voltage harness is as follows:
(2) Parallel arrangement design
Parallel arrangement means that the harness runs in the same direction but is arranged in parallel attached to the frame or body. The parallel arrangement is adopted to ensure that the high and low voltage harnesses are parallel and not crossed. As shown in the figure below, the left frame is arranged with high-voltage harness, and the right frame is arranged with low-voltage harness:
Due to the difference of vehicle structure and electrical device layout and the limitation of layout space, the above two layout forms will be reflected in the daily wiring harness layout design of new energy vehicles, and different layout forms will be combined to minimize or avoid the interference of high voltage on low voltage wiring harness communication.
Design of safety layout principle for high voltage wiring harn
On the basis of the above two high-voltage wiring harness layout, we should also consider the principles of safety, maintainability and convenience of high-voltage wiring harness layout.
(1) Design of vibration avoidance area
When arranging and fixing the high voltage harness, avoid the severe vibration area (such as air compressor, water pump and other vibration sources), and the high voltage harness shall be connected with the high voltage equipment without relative vibration. When it is impossible to avoid due to structural layout and other factors, enough high-voltage wires shall be reserved according to the vibration amplitude of the harness layout and the maximum motion envelope of the moving parts, so as to avoid the tension or tension of the harness.
When the vehicle runs on bumpy road conditions for a long time, it is easy to cause the position of the fixed point of the high-voltage wiring harness to stagger and fall off, which leads to the instantaneous increase of the distance between the two fixed points, and the pulling of the wiring harness causes the internal nodes to pull off or virtually connect, resulting in the open circuit. It is also necessary to avoid the distortion of the harness caused by excessive length.
(2) Design of avoiding high temperature area
When arranging the wiring harness, avoid the high-temperature parts on the whole vehicle, so as to avoid the risk of short circuit between the exposed core wire and the frame caused by the melting or accelerated aging of the wire due to high temperature. Common high-temperature components of new energy vehicles include air compressor, brake pipe, steering pump, oil pipe, etc.
(3) Design of bending radius of HV conductor
Whether it is to avoid extrusion or to avoid areas with excessive vibration amplitude, attention should be paid to the bending radius of the high-voltage harness when it is arranged. This is because the bending radius of the high-voltage wiring harness has a great influence on the resistance of the high-voltage wiring harness. If the high-voltage wiring harness is excessively bent, the resistance of the bending part of the wiring harness will increase, which will increase the line voltage drop. At the same time, excessive bending for a long time will also cause aging and cracking of the insulating rubber of the wiring harness.
Therefore, we need to avoid excessive bending of wires in the joint both in the early design and in the assembly process, otherwise the seal at the rear of the joint may have a leakage path. The high voltage wire harness at the tail of the high voltage connector shall be kept straight, and the high voltage wire near the tail of the connector shall not be bent and stressed, and shall not be rotated.
Sealing and Waterproof Design of High Voltage Line
In order to improve the mechanical protection and dustproof and waterproof performance of the high-voltage wiring harness, sealing rings and other protective measures are adopted between connectors and at the position where the connector connects the cable to prevent water vapor and dust from entering, so as to ensure the sealed environment of the connector and avoid safety problems such as short circuit, spark and leakage between contacts.
At present, most high-voltage wire harnesses are protected by using a covering material, and the covering material mainly has the functions of preventing abrasion, reducing noise, insulating a radiation heat source, beautifying, and the like, and is generally completely covered by an orange high temperature resistant flame retardant corrugated pipe or an orange high temperature resistant flame retardant cuff.
3 Sealing measures
Harness dual-rail design/HV connector selection design/HV harness shielding design
Strengthen food safety supervision of aquatic products
The high-voltage conductor and the high-voltage connector are sealed by means of conductor seals, heat-shrinkable tubes, rubber parts, etc., so as to meet the waterproof and dustproof requirements of IP67 grade.
Generally speaking, the design and layout of high-voltage wiring harness for new energy vehicles need to consider many factors, such as wiring harness type, connector selection, shielding design, safety layout principles and waterproof and dustproof design. The rational use of these measures can improve the safety and reliability of the high-voltage wiring harness and ensure the normal operation of the vehicle.
