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2023
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High voltage wiring harness connection process for new energy vehicles
The overall wiring harness of automobiles can be divided into two types: low-voltage wiring harness and high-voltage wiring harness. Traditional fuel vehicles mainly use low-voltage wiring harness, while new energy vehicles mainly use high-voltage wiring harness. High voltage wiring harness is the neural network of the high-voltage system of new energy vehicles, which can be configured to connect the internal and external wiring harnesses of electric vehicles according to different voltage levels. Mainly used for internal wiring harness signal distribution in distribution boxes, efficient and high-quality transmission of electrical energy, shielding external signal interference, etc.
The high-voltage wiring harness of new energy vehicles is mainly composed of connectors, terminals, wires, covers and other parts. Currently, the connection methods with terminals are mainly divided into three types: welding, crimping, and mechanical connection. Ultrasonic welding can achieve lower resistance and higher bonding force, which has advantages over traditional welding modes. In recent years, it has been widely used in the automotive industry. Therefore, the development of ultrasonic welding technology for high-voltage wire harnesses is of great significance for new energy vehicles.
The content of this article is for reference only:
Main performance requirements for high-voltage wire harnesses
1. Voltage drop: When using crimping connections for high-voltage harnesses, the voltage drop at the conductor crimping point should meet the requirements of the following chart.
2. Connection strength: The connection between the terminal and the wire harness cable should be firm, and its minimum tension value should comply with the provisions of the chart below.
2、 Connection method of high-voltage wire harness
1. Crimp connection
Crimping connection is the use of tools or equipment to deform the connector joint and press it onto the wire through pressure, forming a mechanical connection between the connector terminals and the wire, making it have good mechanical and electrical performance. At present, there are three known connection methods for automotive wire harnesses, but most foreign wire harness cables and plug-in terminals are connected by crimping. This process technology is already very mature and stable, suitable for large-scale practical production.
The advantages of crimping connection:
① reliable connection, high production efficiency, and adaptability to automated production;
② The connection process does not require solder and flux, overcoming the disadvantages of difficult welding cleaning and easy oxidation of the welding surface;
③ At the same time, the crimping process has low environmental requirements, simple operation, and is not easy to cause artificial failure. But its drawbacks are also quite obvious. After crimping, there is still a situation of incomplete contact between the wires, and there is an increase in contact resistance during long-term operation, which ultimately leads to the joint being prone to heating and increasing electrical energy loss, affecting circuit safety.
Among them, the crimping height plays a crucial role in crimping connections. The mechanical performance of crimped terminals will increase with the decrease of crimping height, but after exceeding a certain critical value, the mechanical performance will rapidly decline; The electrical performance of crimped terminals will first increase and then tend to level with the decrease of crimping height, and finally gradually decrease. Therefore, it is necessary to determine an appropriate crimping height to ensure good mechanical and electrical performance as much as possible.
2. Welding connection
Due to the difficulty of traditional welding processes in meeting development needs, ultrasonic welding technology is gradually being applied to the welding of high-voltage wiring harnesses for new energy vehicles.
The advantages of ultrasonic welding technology include:
① The welding range is wider, not only suitable for the same material, but also can achieve the effect of rapid prototyping for welding between different materials with different properties;
② The welding strength is higher, and ultrasonic welding does not require external heating of the welded specimen, so residual stress will not be generated due to the specimen being heated. At the same time, higher welding strength will be obtained, with better stability and fatigue resistance;
③ Higher welding efficiency, ultrasonic welding does not require welding rods or cooling operations, can quickly complete spot welding, continuous welding and other operations, and save more electricity consumption;
④ More safe and environmentally friendly, ultrasonic welding does not require additional flux, does not pollute the structure of the welded parts, and maximizes the integrity of the welded parts.
Disadvantages:
① As the thickness and hardness of the welded workpiece increase, the difficulty of welding increases sharply, requiring higher welding power, indirectly increasing the manufacturing difficulty and cost of high-power ultrasonic welding machines;
② The unfolded surface of the workpiece welded by ultrasonic waves will be wider, making it difficult to install in narrower positions.
There are many process parameters for ultrasonic welding, mainly including welding duration, welding pressure, and welding amplitude. Usually, with the increase of welding parameter values, the mechanical properties of the welded part show a trend of first increasing and then decreasing.
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