1.2.2High voltage interlock (HVIL)
In terms of the entire high-voltage interconnection system, in order to ensure the safety of the high-voltage system when it is powered on and off, the concept of high-voltage interlock is introduced in the connection design. The simple description is that when the connector is plugged and turned on, the high-voltage circuit is first contacted and turned on, and then the high-voltage interlock signal circuit is turned on; when disconnected, the high-voltage interlock signal is disconnected first, and then the high-voltage circuit is disconnected. Most connector manufacturers put the high-voltage interlock design inside the connector, and some manufacturers put the high-voltage interlock outside the mating cavity through the auxiliary structure design. It is very important to ensure the stability of the high-voltage interlock circuit. If the high-voltage interlock is not continuous, the possible impact will be very bad. For example, when the car is driving, the signal of the high-voltage interlock circuit is abnormal, causing the whole car to suddenly lose power and fail to operate normally, which may cause a traffic accident.
1.2.3 High-voltage interlocking locking structure
Understand that the real secondary lock does not have a secondary protection function, but more effectively protects it. The real meaning is that after the primary lock, if the primary lock fails or no operation is verified in place, the secondary lock is It is a very important function to ensure that the first lock is protected after the first lock is locked. The most commonly used mechanism in the secondary locking structure combined with the primary lock is the moment arm mechanism. Because the primary locking is related to the insertion and extraction force, a form similar to the moment arm mechanism is required according to the mechanical design concept, so as to achieve both labor saving and The connector can be easily inserted in place.
For the requirements of the force arm, USCAR talks about a lot of ergonomic operability of the force arm. The USCAR also stipulates the force requirements of the related primary and secondary locks in the case of mating and mismatching. In fact, most of us would think that USCAR is the standard for connectors, but I think that the USCAR standard is not only a technical standard, but also guides designers to make the structure reliable in the design process, and how to make the structure and performance reliable under the premise of reliable structure and performance. , Can also provide customers with a better product experience. The picture below is a picture of a more common locking structure product.
1.2.4 High-voltage connector protection level
The protection of the connector is mainly divided into three arrangements:
The first is the board end seal: the board end is the connector socket end using four screws to install mechanically. This is a more commonly used structure, but there are also some special structures
high-voltage cable、high-voltage connectors、HVIL
The second is the plug-to-head seal: the plug-to-head plug means that the male end contains the female end or the female end contains the male end with rubber parts for protection between the radial and axial directions
high-voltage cable、high-voltage connectors、HVIL
The third is the wire end seal, the protective seal between the wire end connector and the cable
With the development of the market for high-voltage connectors for electric vehicles, the performance requirements of OEMs for product protection are also constantly improving. In the early stage of industry development, the protection requirements of IPI67 can already satisfy most customers. However, in the later period, as the protection failure of connector products appeared on the market, there were more and more cases of product leakage, insulation failure, and even ablation.
he gradual improvement of protection requirements has become the development trend of electric vehicles. The current IP67 requirements cannot meet the normal use requirements. Of course, this is not absolute, and it depends on the location of the connector on the vehicle. According to the layout of the high-voltage circuit in the whole vehicle, it will be suspended under the chassis of the car. It is a principle that high-voltage must not enter the cabin. Therefore, most high-voltage connectors are located on the chassis close to the ground or close to the wheel hub. When the weather is bad, such as severe weather, heavy rain, or some severe cold weather, the water carried by your tires will actually impact these connectors. If you are familiar with the test, the domestic standard does not have IP6K9K. It is found that if IP67 is used, the impact pressure of the high-pressure water gun is actually not as great as 6k9k. When the car is running at high speed and suddenly wading into the water, the instantaneous water pressure rushing to the connector will be very large, so sometimes it is difficult to meet the actual use requirements of IP67. In response to this, the current domestic standard QC/T1067 and the foreign standard USCAR divide the connector seal into two levels S1 and S2. For the S2 level, it is clearly stipulated that the applicable occasion is the lower position of the chassis, and 6K and 9K are recommended, so if the protection is connected in the future, it must be 6K and 9K. If the connector is not arranged in the above position, the IP67 design can actually meet the requirements of the entire vehicle.
1.2.5 Electromagnetic shielding
Electric vehicles have many electronic devices, and electric current will generate magnetic fields, and the whole vehicle parts must have the ability to resist interference. Especially as electric vehicles are now a carrier, unmanned driving will be developed more on this basis, so this technical issue is very important. For high-voltage systems, shielded connectors and cables are very important, but we have to give priority to system-level layout. This is a prerequisite. If your OBC, the location of your layout, including the system DCDC itself may have some congenital problems, no matter how good the connector is, there will be various signal interference problems, so we must first consider the system type, and then consider the component level. Regarding the shielding effectiveness of the connector, two methods are generally adopted.
In the first way, we have a metal shield on some plastic connectors, and the cable shield will be connected to the shield of the metal shell to form an effective 360° shield. In the second way, most high-voltage and low-current connections will not have a secondary connection, and will be connected to the shielding layer of the cable. This method is also commonly used by existing manufacturers, including some of the more well-known domestic ones. OEMs are also considering this approach. We call it spring contact (English), which is actually a spring connection. The benefits of this structure are also many, because the size and space will be smaller, and its contact points will be more; there are many manufacturers of this structure, mainly represented by companies such as BMW Spring in Switzerland and Basel in the United States. They There are many practical and mature application cases in this area.
In most cases, the connection between the wire and the shielding layer will be crimped in the form of metal inner and outer rings. The shielding layer is placed between the two metal rings, and the shielding layer and the metal ring are deformed by cold pressing. Tightly fix. In addition, we also have a shielding method, which uses a structure similar to a watchband spring to replace the spring connection. This structure is often used in military products and has mature technology; we have done relevant tests and can meet the design requirements . The structure is applied to the shielding of new energy electric vehicles, which can not only meet the performance requirements, but also is a punched part, suitable for mass production and high cost performance.
The material of the connector insulation is generally PA66, PBT, ABS, PC, etc. The contact material is generally made of brass, phosphor bronze, beryllium copper, etc., but the most commonly used materials abroad are copper-nickel-silicon materials. The connector shell material is generally divided into two kinds of materials: plastic and metal.
Due to the demand for lightweight vehicles, especially passenger car manufacturers, under the premise of meeting product performance, they will try their best to choose plastic connectors to control the weight of the vehicle.
2.Product use environment
Because the mechanical strength of metal materials is better than plastic. Therefore, in some harsh environments, metal connectors are more suitable. For example, special vehicles, muck trucks, and electrical connection parts that are not protected during the layout of the entire vehicle. At this time, metal connectors are slightly better than plastic connectors in terms of environmental impact and mechanical strength.
Regarding the shielded connector, since the shell of the metal connector itself is used for conducting the shielding, it forms a carrier for shielding protection. Under normal circumstances, metal connectors are easier to achieve better shielding effectiveness than plastic connectors, and the appearance structure is more compact.