In the field of new energy vehicles, the requirements for the cleanliness of parts have reached a very high standard, and there are many important reasons behind this.
There are mainly the following standards for the cleanliness of automotive parts:
International standards
· ISO16232: In December 2018, the part1–part10 documents released in 2007 were reorganized. This standard specifies the cleanliness technology of road vehicle parts and systems, including the definition of cleanliness, detection methods, and result representation. For example, particle size classification is specified, and letters are used to represent different size segments, such as b for 5≤x<15μm, c for 15≤x<25μm, etc. Cleanliness levels are also specified, expressed as the total mass of particles per 1000cm² surface area, such as level 0 for 0mg, level 1 for 0.0005mg, etc.
· ISO4406: This standard is based on ISO4021 and refers to the NAS1638 standard. It specifies the particle size and quantity classification system and is still used today. It is mainly used for hydraulic oil cleanliness standards and can also be used as one of the reference standards for automotive parts cleanliness testing.
Industry standards
·VDA19: The German Association of the Automotive Industry released VDA19-2015 “Automotive Parts Cleanliness Test Method” in March 2015. The standard mainly includes weighing method, optical microscope method, high-precision dimensional measurement technology, industrial CT scanning detection, SEM scanning electron microscope-energy spectrum analysis method, FTIR infrared spectrum analysis and Raman spectroscopy technology for particle testing and evaluation methods.
·GMW16037: General Motors Global Automotive Engineering Standard Powertrain Parts Cleanliness Quantitative Test Method, which specifies the test methods and requirements for the cleanliness of powertrain parts.
Corporate standards
·Volkswagen series: Standards such as VWPV3370 put forward specific requirements for the cleanliness of Volkswagen parts, including cleanliness test methods, limits, etc.
·BMW series: Standards such as QV11111 specify the cleanliness specifications of BMW auto parts, covering the cleanliness requirements and test processes of different parts.
·ZF series: Standards such as ZF0000701604 have detailed regulations for the cleanliness of ZF automotive parts to ensure that the cleanliness of parts meets the requirements during production, assembly and use.
1.｜Ensure the performance of the electrical system
The core of new energy vehicles lies in the high-voltage electrical system, which covers battery packs, motors and electronic control units. Taking the battery pack as an example, it is usually composed of a large number of single cells connected in series or parallel to form a complex circuit network. Once there are conductive impurities on the surface of the parts, such as metal shavings, it is very likely to cause a short circuit between the positive and negative poles of the battery. The consequences of a short circuit are disastrous, and the battery may overheat or even catch fire. Looking at the motor again, its internal winding is composed of a large number of copper wires and the insulation layer is very thin. If impurities, especially conductive particles, enter the motor, they will destroy the insulation layer, causing the motor winding to short-circuit, affecting the normal operation of the motor, reducing efficiency, and directly damaging the motor in severe cases. The electronic control unit (ECU) of the car relies on various sensors and wiring harnesses to receive and send signals to control the driving status of the vehicle. However, parts with poor cleanliness will interfere with signal transmission. For example, when the surface of a sensor is covered with dirt or impurities, the accuracy of its sensing signal will be greatly reduced. For example, if a temperature sensor is covered with oil, the monitoring of the battery or motor temperature will be deviated, making it impossible for the ECU to accurately adjust the battery charging and discharging strategy or motor power output according to the temperature, thereby affecting the vehicle performance and safety.
2.｜Maintaining battery life and performance
The cleanliness of the battery interior has a significant impact on the self-discharge rate. When impurities, especially conductive impurities, are mixed into the battery, a tiny conductive circuit will be formed inside the battery. For example, for lithium-ion batteries, if metal impurities are mixed into the electrolyte, these impurities are like additional “power consumption channels”, causing the battery to discharge slowly when not in use, reducing the battery storage performance and range. The work of the battery is based on internal chemical reactions. Taking lithium batteries as an example, the reaction between the positive electrode material, the negative electrode material and the electrolyte needs to be carried out in a relatively pure environment. If the cleanliness of the components is not enough, the impurities will react with the chemical substances inside the battery. Some impurities may react with the electrolyte to produce gas or sediment. Gas may increase the internal pressure of the battery and cause the battery to bulge; sediment will affect the internal ion transmission of the battery and reduce the battery charging and discharging efficiency.
3.｜Improve the reliability and durability of mechanical parts
Although new energy vehicles are mainly powered by electricity, there are still many mechanical parts, such as transmissions and drive shafts. When these parts work in an environment with more impurities, impurities will increase the wear between parts like abrasives. For example, if impurities such as sand enter the gears in the transmission, the wear rate of the gear surface will be accelerated, the service life of the gears will be shortened, and the transmission shifting will not be smooth, abnormal noises will occur, and other problems may occur. Good lubrication is the key to the normal operation of mechanical parts. Parts with poor cleanliness will contaminate the lubricating oil. For example, if there are impurities such as metal chips in the oil channel inside the engine, they will be mixed into the lubricating oil and reduce the quality of the lubricating oil. When the impurity content in the lubricating oil is too high, a good oil film cannot be formed on the surface of the mechanical parts, resulting in increased friction between parts, excessive heat generation, and affecting the reliability and durability of the mechanical parts.
To sum up, new energy vehicles have high requirements for component cleanliness in order to ensure the performance of the vehicle’s electrical system, maintain battery life and performance, and improve the reliability and durability of mechanical components. Each aspect is closely related to the safety, performance and service life of the vehicle.
Leave a Reply