High voltage wiring harness design scheme for new energy vehicles

With the rapid development of new energy vehicle technology, various Oems have launched a series of new energy vehicle products in recent years, including pure electric vehicles, hybrid electric vehicles, hydrogen fuel vehicles and so on. The technology of new energy vehicles is also gradually improving, and it is the general trend for electricity to replace traditional fuel as the power source of vehicles. High-voltage wiring harness is the main connection and transmission system for vehicle power supply and vehicle function realization. Due to the existence of high-voltage voltage in new energy vehicles, it faces the test of design scheme and layout in the process of designing high-voltage wiring harness.

First, high voltage wiring harness design scheme

1, Wire Harness Double Track Design

The high-voltage wiring harness design of new energy vehicles adopts dual-track design, because the output voltage of the power battery is high voltage, which exceeds the safety voltage of the human body, so the body can not be used as a high-voltage wiring harness vehicle iron point, on the high-voltage wiring harness system, the DC high-voltage piezoelectric circuit must be strictly designed in accordance with the dual-track system. Commonly used high voltage wiring harness can be divided into drive system high voltage wire, power battery high voltage wire, charging base high voltage wire, air conditioning compressor high voltage wire, steering oil pump high voltage wiring harness.

2, high-voltage connector selection design

The high voltage connector is mainly responsible for the connection and transmission of high voltage and high current, and is an important part of the vehicle to ensure human safety. Therefore, the high-voltage connector needs to be fully considered in the selection of high-voltage resistance, protection level, loop interlock, shielding and other functions. At present, the selection of high-voltage connectors is the first to use the industry's more front-end, mature and reliable suppliers, such as: AVIC Optoelectronics, Tyco, Yonggui, Amphenol and Rekeda.

3, high voltage wire harness shielding design

The high voltage wire harness will produce strong electromagnetic interference when transmitting the changing high voltage electricity, so it is necessary to use the wire with braided shielding net. The connector is also designed with a shield as far as possible in the selection, and the connection closed loop with the high-voltage wire harness shield can be realized when crimped, and the electromagnetic interference generated by the high-voltage wire harness can be suppressed.

Second, high-voltage wiring harness layout design

1, high voltage wiring harness layout principle

The principle of nearby layout: When arranging high-voltage wiring harnesses of new energy vehicles, the path of high-voltage wiring harnesses should be reduced as much as possible, so as to avoid the pressure drop caused by too long a path, and also meet the design of cost reduction and weight reduction.

Safety principle layout: In addition to meeting the principle of proximity, the layout of high voltage wiring harness should also meet the principles of concealment, safety collision regulations, and maintenance convenience, and it is also necessary to effectively protect the high voltage wiring harness. Unreasonable arrangement of high voltage wiring harness may lead to leakage, fire and endanger the safety of drivers and passengers.

2, high-voltage wiring harness layout type

At present, the layout type of high voltage wiring harness generally adopts two ways: layered layout and parallel layout. Both methods are based on the separation of high-voltage and low-voltage wiring harnesses to reduce the electromagnetic interference of high-voltage to low-voltage communications.

(1) Layered layout design

As the name suggests, the layered arrangement is to separate the high-voltage and low-voltage wiring harnesses from a certain distance for arrangement, so as to avoid the electromagnetic interference generated by high-voltage to the low-voltage control unit power supply and signal transmission. The layered layout design of high and low voltage wiring harnesses is shown as follows:

(2) Parallel layout design

Parallel arrangement is that the wiring harness goes towards the same direction but adopts the attached frame or body parallel arrangement. Parallel arrangement is adopted to ensure that high and low voltage wiring harnesses are juxtaposed without crossing. As shown below, the design arrangement is side-by-side. The left frame is arranged with high voltage wiring harness, and the right frame is arranged with low voltage wiring harness:

Due to the differences in the structure of the vehicle, the layout of electrical appliances and the limitations of the layout space, the above two layout forms will be reflected in the daily wiring harness layout design of new energy vehicles, and the combination of different layout forms will minimize or avoid the interference of high voltage to low voltage wiring harness communication.

3, high voltage wiring harness safety layout principle design

On the basis of the above two high-voltage wiring harnesses, we should also consider the principles of safety, maintainability and convenience of high-voltage wiring harnesses.

(1) Vibration avoidance area design

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), and the high-voltage wiring harness should be connected to the high-voltage equipment without relative vibration. 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.

When the vehicle is driving on the bumpy road for a long time, it is easy to cause the positioning of the fixed point of the high voltage wire harness to mismove and fall off, which leads to the instant increase of the distance between the two fixed points, and the pulling of the wire harness causes the internal node to pull off or virtual connection, resulting in a break. Therefore, the length of the high voltage wire should be controlled reasonably, and the length should be left surplus to offset the stress caused by the motion drag. And to avoid too long to cause the wiring harness distortion.

(2) High temperature avoidance area design

When arranging the wiring harness, the high-temperature parts on the vehicle should be avoided to avoid the risk of melting or accelerating the aging of the wire due to high temperature, resulting in the exposure of the core wire and the short connection of the frame. Common high-temperature components of new energy vehicles are: air compressor, brake gas pipe, steering oil pump, oil pipe, etc.

(3) High voltage wire bending radius design

Whether it is to avoid extrusion, or to avoid areas with excessive vibration amplitude, the bending radius of the high-voltage wire harness needs to be paid attention to when it is arranged. This is because the bending radius of the high-voltage wire harness has a great influence on the resistance of the high-voltage wire harness. If the high-voltage wire harness is excessively bent, the resistance of the bent part of the wire harness will increase, resulting in an increase in the voltage drop of the line. At the same time, excessive bending time for a long time will cause aging and cracking of wire harness insulation rubber; The following is the wrong design diagram (Note: the minimum inner bending radius of the general high voltage wire should not be less than four times the outer diameter of the wire) :

Example diagram of correct arrangement of joints (left) Example diagram of incorrect arrangement of joints (right)

Therefore, whether we are in the early design or in the assembly process, we need to avoid the phenomenon of excessive bending of the wire in the joint, otherwise the leakage path may appear in the rear seal of the joint. 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.

4, high voltage wire sealing waterproof design

To improve the mechanical protection and dustproof and waterproof performance of the high-voltage wiring harness, protective measures such as sealing rings are used between the connectors and the positions where the connectors are connected to the cables to prevent water vapor and dust from entering the sealing environment of the connectors and prevent short circuits, sparks, and electrical leakage between the contacts.

At present, most of the high-voltage wire harnesses are protected by covering materials. The main functions of the covering materials are anti-wear, noise reduction, radiation heat source insulation, beauty, etc. Generally, orange high-temperature-resistant flame retardant bellows or orange high-temperature-resistant flame retardant cloth sleeves are completely covered. As shown in the picture below:

Third, sealing measures

The high voltage wire and the high voltage connector are sealed by wire seals, heat shrink tubes, rubber parts and other ways to meet the waterproof and dust requirements of IP67.

Examples of various sealing and preventive measures:

Seal protection with adhesive heat shrink tube (left) Plug-in seal protection with blind plug (right)

Connector tail with rubber sleeve seal protection (left) Wiring harness U-shaped arrangement prevention (right)

Four, one for the new energy vehicle wiring harness

At present, the production line has the ability to complete the manufacturing process from the decomposition of drawings to the production line - peeling - crimping - sub-assembly - assembly - testing, which can not only meet the self-made wiring harness of its own products but also meet the needs of different customers for new energy wiring harness.

1. High voltage wiring harness

As the main artery of the power transmission of new energy vehicles, the material and technical requirements of the high-voltage wire harness are more stringent than the traditional wire. In order to meet the functional requirements of new energy vehicles, we purchased 2.5 square to 70 square shielded high voltage wires with different wire diameters and core numbers.

2, special production equipment

The production process of new energy high-voltage wiring harness is relatively strict, in order to improve product quality and meet the production process requirements. One for the introduction of a large number of special production equipment:

Pneumatic downline (left) Barker (right)

Terminal tension machine (left) Insulation testing instrument (right)

Insulation testing instrument

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