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Code for design of high-voltage wire harness bracket for electric vehicles
Time:2021-11-18 Read: 513

In recent years, with the strong support and promotion of China, the development of new energy vehicles in China has made considerable progress, and various new energy vehicles have gradually entered our daily life. In brief, new energy vehicles mainly refer to vehicles that use unconventional vehicle fuel as power source (or use conventional vehicle fuel and new vehicle power unit), integrate advanced technologies such as vehicle power control and drive, and have advanced technical principles, new technology and new structure. Including pure electric vehicles, incremental electric vehicles, hybrid electric vehicles, fuel cell electric vehicles, hydrogen engine vehicles, other new energy vehicles, etc.

However, regardless of the form of new energy vehicles, their common characteristics are the use of voltage platforms up to 300V~600V or higher, involving wiring, and all have the same basic requirements, namely, the safe transmission of large current and large voltage under the electromagnetic interference protection system. High-voltage cables are used to connect high-voltage batteries, inverters, air-conditioning compressors, three-phase generators and motors to realize the transmission of power energy. However, in order to avoid the abrasion and ablation of the high voltage harness, the corresponding support is usually designed for the connector and direction of the high voltage harness to effectively protect the harness and ensure its reliability, thus improving the safety of the harness and the quality of the whole vehicle.

Code for design of high-voltage wire harness bracket for electric vehicles

1、 Scope

This specification specifies that the design process of high-voltage harness support for electric vehicles involves symbols, codes, terms and their definitions, design standards, layout requirements, structural design requirements, material selection requirements, performance design requirements, design calculation methods, safety use requirements, etc.

This specification is applicable to the support design that is currently being developed and applied in the design process of all high-voltage harnesses for subsequent electric vehicles.

2、 Functional requirements and performance requirements to be met

2.1 Functional requirements

The main functions of the high voltage harness bracket are to fix and limit the direction of the high voltage harness, avoid the abrasion and erosion of the harness, and effectively protect the reliability of the harness; At the vibration position of the vehicle, a harness fixing bracket is added at the end of the connector to absorb the vibration of the middle section of the high-voltage harness, improving the safety, reliability and vehicle quality of the high-voltage harness.

2.2 Performance requirements

2.2.1 Material strength requirements

The wire diameter and layout position of the high voltage harness determine the design strength of the fixed bracket, especially for the DC bus of the power battery and the link harness of the motor control and drive motor. Due to the large wire diameter of the harness and the large number of harness groups, in the process of designing the fixed bracket of the high voltage harness, it is necessary to add corresponding stiffeners and flanging to improve the strength and stiffness requirements of its structure. Therefore, according to its requirements, DC01 cold-rolled low-carbon steel strip is mainly used for the material selection of high-voltage wire harness support, the material thickness is basically 1.5mm, cold stamping forming or mold forming. Its tensile strength is 270~400Mpa, and its yield strength is 130~260Mpa.

However, in the empty position of the front engine room, for example, there are no other parts around it that can be fixed by the bracket: because of the special length and wire diameter of its wire harness, it is difficult to form with steel strip or other metal materials, and the cost and quality cannot be well controlled; PA6 PP material is usually used. Due to its particularity, it can be customized according to the outer diameter, direction and surrounding environment of the high-voltage harness. This material has high tensile strength (tensile strength:>75Mpa), toughness resistance and impact resistance, and can meet the use requirements.

2.2.2 Ambient temperature requirements

According to the position in the vehicle, the vehicle temperature can be divided into three gears.

(1) 1st gear, temperature range (- 40 ℃, 125 ℃); Location: except for engine compartment and exhaust pipe.

(2) Second gear, temperature range (- 40 ℃, 180 ℃); Location: engine compartment.

(3) Third gear, temperature range (- 40 ℃, 250 ℃); Location: near the exhaust pipe of the engine and the copper pipe of the air pump.

DC01 is a material for cold rolling low-carbon steel strip, which can meet the temperature requirements.

The high polymer polypropylene has a good processing temperature of about 200-300 ℃ and good thermal stability (decomposition temperature of 310 ℃). The forming temperature of PA66 is 260-300 ℃, and the melting temperature is 260-290 ℃ according to the different grades of PA66.

2.2.3 Process cost requirements

Cold continuous rolling low carbon steel strip made of DC01 material is mostly formed by cold stamping; If the material cost is low, the use cost is low, and the output is small, bending forming can also be used.

Because PP/PA66 is a plastic part, most of them adopt injection molding. However, due to its environment and installation and fixation requirements, the plastic support of high-voltage wire harness and the fixing feet of trunking are usually embedded with metal nuts; In order to meet the strength requirements of the fixed point, the particularity of installing the fixed support will also be formed by the combined mold.

2.2.4 Flame retardant requirements

PP/PA66 flame retardant: refers to that after adding enough flame retardant, the flame will spread slowly in the combustion process or stop burning soon after the fire source is removed; UL94 V0 level is required.

2.2.5 Self-lubrication and friction resistance

D01, as the support of high voltage harness, mostly uses screw connection and welding process with the body to reduce the friction and abnormal noise between the support and the body or parts.

PP/PA66 material high voltage harness bracket has good self-lubrication performance and friction resistance. It has good self-lubrication performance, low friction coefficient and long service life as a transmission component.

3、 Design input and output requirements

3.1 Structural requirements of high-voltage harness support

At present, the harness bracket and trunking must be customized according to the outer diameter of the high-voltage harness, the direction of the harness and the environment of the bracket in the vehicle; In addition, it is required that the harness bracket has its specific fixation and limit mode.

3.2 Material input

According to the requirements of vehicle design quality and cost, corresponding materials are selected, mainly DC01 steel belt and PP/PA66 plastic materials.

3.3 Strength requirements

Determine whether the strength of the support meets the requirements according to the wire diameter, turning radius and the environment (vibration, friction) of the high-voltage harness of the whole vehicle.

4、 Assembly requirements

Under the condition of mechanical and electrical safety, use special tools to match the harness support with the connection part. Appropriate length shall be reserved for the plug-in or connecting part of the high-voltage harness, and the recommended length is<150mm, which is convenient for vehicle assembly and regular maintenance of components.

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