The changes of the new four modernizations have also put forward more stringent requirements for developing automotive wiring harness technology. High voltage and lightweight are the irreversible development trend of the automotive wiring harness industry. High-voltage electrical equipment, but to reduce the rated current, you can use thinner high-voltage wires to reduce the weight of the wire harness. For every 100kg reduction of the vehicle, the fuel consumption per 100 kilometers can be decreased by 0.3-0.6L, or the cruising range can be increased by 10%-11%. If the car harness can reduce the weight by 20kg, it can increase the mileage by 2%. Let's talk about the development trend of an automotive wiring harness.
1. Lightweight
A) Lightweight wiring harness system design
The use of reasonable electrical architecture and electrical system layout and wiring and affordable insurance and wire selection and matching within the safety range is the key to lightweight design. The picture above is the old Mercedes-Benz GL platform, and the image below is the Tesla Model 3 platform. The previous generation architecture of BenzGL adopts a distributed functional architecture; that is, each function is integrated into each ECU module. There are 70-80 modules, with hundreds of modules. Although the modules are all network communication, the whole vehicle wiring harness weight is as high as 40- 50kg; the single-body wiring harness has weighed 25-30kg. Tesla uses a domain controller that integrates and distributes, including three domain controllers: Central Computing Module (CCM), Left Body Control Module (BCM_LH), and Right Body Control Module (BCM_RH). Many functions are integrated into the domain controller, leaving only the ECUs responsible for peripherals to be distributed. The domain controller is bridged through the CAN or Ethernet bus. Coupled with the optimized layout design, the entire vehicle wiring harness weight is only 20kg, and the total length is 1.5km. It has a better power-saving effect.
Mercedes-Benz also considers weight reduction in the layout. For example, the front SAM is placed on the right A-pillar side. The front cabin, ceiling, instrument, and body lines can be connected and connected to the corresponding plug-in position on the SAM, reducing inline It can also have some weight loss effect when used.
B) Lightweight wiring harness material:
Lightweight wire
The conductor selection is more reasonable, such as 0.13 mm2 wire or flexible cable, which can reduce weight and save space. Ultra-thin-walled wires replace conventional thin-walled cables, such as 0.13mm2 ultra-thin-walled PVC wires that can reduce weight by 13% and size by 24%. Compared with copper, the application of aluminum wire can reduce the total weight of the car body harness by more than 30%. The high-voltage aluminum conductor adopts an aluminum alloy conductor to reduce the weight by 46-49% compared with the copper conductor.
Connector lightweight
One of the effective ways to reduce the weight of the wire harness is to reduce the size and weight of the connector. At present, the weight of small connectors developed by Sumitomo Corporation of Japan will be reduced by 20% to 40% under the same functional requirements. Taking Rosenberg HFM as an example, Rosenberg changed the traditional FAKRA to the HFM (high-speed FAKRA mini) series with a compact structure, smaller size, and faster transmission speed.
Foaming technology is used in products such as guard plate brackets.
Polyurethane foaming technology can also reduce the weight of the wire harness, and it also facilitates the spatial arrangement of the wire harness. It has the characteristics of lightweight, short molding cycle, reduced warpage, improved accuracy, strong oil and dust resistance, and no noise after installation.
2. The wiring harness system is modularized and integrated
When the wiring harness is designed in a modular manner, the wiring harness is divided into small modular wiring harnesses according to their functions. During production, different functional modules can be selected for assembly according to the functional requirements of the configuration. For example, Benz divides the automotive wiring harness into each small module wiring harness according to the function, and then selects different modules to assemble together according to different configuration requirements, but will not produce a large part number, and all selected wiring harness modules will be printed on the product label number. The whole vehicle wiring harness adopts the KSK modular production mode, which can meet the different needs of customers to the greatest extent.
The wiring harness system will also be integrated and assembled with other modules, such as door modules, ceiling modules, front and rear protection modules, etc., to reduce the assembly time of the vehicle in the production process and improve work efficiency.
The combination number and complexity of the wiring harness parts are determined by the number of options on the vehicle configuration table. Taking a specific C-class car as an example, there are more than 100 optional combinations that can be realized in the whole series. As a result, the wiring harness BOM has become more complex, and the number of varieties has exploded. Although the use of modular production methods has eased, it still increases a lot of management costs.
A new development trend for wiring harnesses in this form, as Tesla has begun to design separate hardware and software for its facilities, and the mass-produced cars are unified hardware. Then the hardware is given actual functions, upgrades, expansions, and optimizations through OTA. As a part of software requirements, the wiring harness can cover the most extensive range of electrical components for design under this trend of separation of software and hardware and break free from more than 100 configuration combinations.
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3. Redundant design of wiring harness system
With the rapid development of L3\L4 automated driving technology, the automatic driving function puts forward functional safety design requirements for some key components (ESP, EPS, etc.), that is, redundant design. The redundant design puts forward new needs for creating vehicle power systems, power distribution systems, and circuit systems. At present, some schemes add a set of power supply and power distribution systems and intelligent circuit breakers to meet the functional safety level D requirements. Some projects need to choose a reasonable scheme based on the actual state of the vehicle by adding an intelligent power distribution system.
4. High-speed communication
With the development of intelligence and networking, the fields of V2X, ADAS, and automatic driving have developed, and the data collection and processing speed requirements have become higher and higher. The vehicle network system has also grown from the original CAN\LIN to CANFD and Fast Ethernet. (100M), Gigabit Ethernet (1000M). The wiring harness system must also be upgraded. Although the twisted pair of CAN and Fast Ethernet has no difference in appearance, they are different, but the 100base-T1 Ethernet wiring harness has a characteristic impedance and insertion loss. Typical parameters such as return loss have been defined in detail, and the number of inlines in the middle has also been stipulated.