Status of foreign standards and regulations
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The United States is the first and only country in the world to develop and enforce TPMS regulations. The US Highway Traffic Safety Administration (NTHTSA) has established FMVSS 138 regulations, requiring all tires and commercial vehicles sold in the United States with a total gross mass not exceeding 4,536 kg to be fitted with a tire pressure monitoring system after September 2007. . Driven by US federal legislation and market opportunities, major auto electronics companies have invested a great deal of research and development enthusiasm, while many well-known chip manufacturers have joined, and continue to introduce smaller, lighter weight, more reliable performance and longevity. A new generation of products. At present, TPMS equipment in the United States has become very popular.
The International Standards Organization (ISO) established the international standard ISO 21750:2006 on tire pressure monitoring systems in March 2006. The American Society of Automotive Engineers also developed the SAE J 2657 standard for light vehicle tire pressure monitoring systems in December 2004. Currently available international automotive regulations and standards include FMVSS 138 tire pressure monitoring system; SAE J 2657:2004 light vehicle tire pressure monitoring system; ISO 21750:2006 road vehicle tire pressure monitoring system for improving vehicle safety.
In addition, the Japan Automotive Standards Organization (JASO) has also developed a technical document for the TPMS real vehicle test method, the technical content of which is basically the refinement of the US FMVSS 138 regulations. The Braking and Moving Mechanism Working Group (GRRF) under the World Vehicle Technical Regulations Coordination Forum (UN/WP29), which is responsible for the development of European and global automotive technology regulations, decided to establish a 62nd meeting in September 2007. The TPMS informal working group, which is chaired by Germany, promotes the development of this regulation. In November 2007, February and September 2008, an informal working group meeting was held to discuss the feasibility of developing ECE regulations for TPMS. Judging from the contents of several meetings, the difficulty of this work is much greater than expected, and the progress is not fast.
Advantages and disadvantages of each standard
US Federal Regulation FMVSS 138. This regulation is an enforced safety standard. Only the most basic functional requirements are specified in the performance requirements. When the tire pressure is lower than the specified air pressure, the TPMS should issue an undervoltage visual alarm signal within 20 minutes. The FMVSS 138 regulations specify requirements for visual alarm signals, as well as test conditions, test procedures, and detailed implementation transition periods. The specific requirements of the US FMVSS 138 regulations for TPMS system performance are:
a) The TPMS system must start running when the car is ignited and alert when the tire pressure is reduced by 25%.
b) The driver must be alerted when the TPMS system fails.
c) The TPMS warning light must remain on until the tire is inflated to normal air pressure or system troubleshooting.
d) A self-test must be performed on the warning light on the instrument panel when the car is ignited.
e) The owner's manual must state a warning that the replacement tire may not match.
f) Automobile manufacturers must gradually increase the proportion of assembled TPMS. The assembly rate of four-wheel passenger vehicles and commercial vehicles with a maximum design total mass of 4,536 kg sold in the United States after September 2007 is 100%.
g) It is specified that the TPMS performs air pressure monitoring at a speed of 50 to 100 km/h.
Due to the technical level of the time, the US regulations only specified the most basic undervoltage alarm function, and also considered the indirect (that is, the way to calculate the tire low pressure through the wheel speed sensor) TPMS system. However, due to the defects of the indirect TPMS system, if the vehicle is stationary, it cannot be monitored, it is judged whether the period of low air pressure is too long (about 20 minutes), it is easy to false alarm, some special states cannot detect low air pressure, and the air pressure value cannot be displayed. Therefore, the products that meet the regulations are not necessarily safe and reliable products, and in the specific application process, users complain about frequent false alarms of some products.
SAE J 2657: 2004 standard. This standard specifies the test methods and performance requirements for tire pressure monitoring systems (TPMS) installed in tubeless tires. Mainly for temperature resistance, thermal cycle, thermal shock, extreme temperature resistance, moisture resistance, frosting, pressure resistance, rapid air leakage, altitude resistance, stain resistance, salt spray corrosion resistance, drop resistance The specific test methods are prescribed for mechanical shock resistance and electromagnetic compatibility. The performance requirements are given on the display mode of the alarm signal, the working conditions of the system, and the most basic performance. The standard stipulates that the system should monitor tire pressure between a speed of 24km/h and a maximum speed.
This standard does not require measurement accuracy, does not limit product life, and the response time of undervoltage alarm is also long (within 10 minutes). It is basically similar in function to FMVSS 138.
ISO 21750:2006 standard. This standard applies to tire pressure monitoring systems for tubeless tires and requires monitoring of all used tires and providing information to the driver. The standard specifies comprehensive performance requirements for systems and components. The standard stipulates that the system should monitor the tire pressure after the vehicle speed exceeds 25km/h. The system is divided into the following levels, and qualitative requirements are given for the performance of each system:
Tire Pressure Alarm System (TPAS). Refers to the measurement of tire inflation pressure and internal temperature or parameters corresponding to the pressure, and sends a message to remind the driver that the inflation pressure limit of the tire has reached the system that needs to be taken.
Tire Pressure Warning System (TPWS). It can provide useful information to the driver, including at least the actual pressure state of each tire. The purpose is to issue a warning when the tire needs to take corrective action.
Tire Leak Alarm System (TLAS). A system is detected that detects a certain tire pressure in use and other tire pressures and a significant change from its own initial air pressure.
The standard specifies some performance limits for tire modules:
a) Service life: use at least 6 years or 100,000 km on the vehicle.
b) Measurement accuracy: The absolute accuracy of the absolute pressure measurement value shall be: ±2% of full scale in the temperature range of 0 °C~70 °C, the maximum shall not exceed ±10 kPa; ±5% of full scale under other conditions, the maximum Not more than ±25kPa; the tire pressure monitoring module installed inside the wheel also specifies environmental resistance and specific test methods. Detailed human machine interface requirements are specified for the display module.
This standard is wider than FMVSS 138 and SAE J 2657, but it does not require TPMS to work when the vehicle is stationary. It only requires an undervoltage alarm within 3 minutes and a fault alarm within 10 minutes when the vehicle speed is greater than 25km/h.
The above three standards have requirements for TPMS from different sides, but for an electronic product that is extremely demanding in terms of both safety and reliability, there are still some shortcomings in the requirements of these standards and regulations. For example, how to reflect and guarantee the reliability and stability of system signal transmission, how to reflect and ensure the system can reach the service life of more than 6 years, how to avoid false alarms and leak alarms, etc. These are the difficulties in the design of TPMS system and Key technologies are also the difficulty in setting standards.
China's upcoming TPMS standard
The research and development of TPMS products in China is later than in the United States, Europe and other countries. Since 2002, there have been early TPMS products in China, which have generally appeared in foreign product agents or imitation development forms, with small scale and low technical content. At the beginning of 2003, Shanghai Volkswagen started the TPMS research and development program, and the domestic TPMS research and development entered the stage of cooperation with the OEM. After a period of independent research and development and innovation, a group of self-developed TPMS products in China have achieved comparable performance and cost to international counterparts. It can be said that the development of China's TPMS industry has entered the stage of independent research and development with independent intellectual property rights.
At present, domestic TPMS product manufacturers are gradually increasing, but the product variety, type, technical level and quality are uneven. The industry urgently needs to develop TPMS national standards to regulate and guide the sound development of the TPMS industry. Considering that this product is a relatively new technology, it is first recommended to encourage the application of advanced technology, and it is recommended as a national standard. After the technology and products are further matured, the feasibility of developing a mandatory national standard for TPMS can be considered. To improve the safety of the vehicle.
On July 31, 2007, led by China Automotive Technology and Research Center, a standard drafting working group composed of more than ten units including vehicle manufacturers, testing and research institutions, TPMS system manufacturing enterprises, sensors and chip manufacturing enterprises was held. The TPMS Standards Research Working Group was established and the first working meeting, and the standard setting work began. A standard consultation draft was formed in May 2008, and a standard review draft was formed in December of that year.
China's "Automobile Tire Pressure Monitoring System (TPMS)" standard highlights include:
Scope of application: Applicable to all types of cars and tires, including passenger cars and commercial vehicles (Class M and N), as well as inner and tubeless tires, and other types of vehicles can also be used for reference (eg two rounds) Motorcycles and construction machinery).
A shorter undervoltage alarm time is required: the TPMS should be issued with an undervoltage alarm signal within 6s. 20mins specified by FMVSS138, 10min specified by SAE J2657:2004, and 3min specified by ISO21750:2006 are greatly shortened, showing better safety.
It is required to have an undervoltage alarm when it is at rest: In actual use, the tire may be in a serious air loss or no air state during the parking of the vehicle overnight (or for a long time), then the alarm should be issued before the vehicle moves. At this time, even if it only rolls a few laps, the tire will be greatly damaged. If the car is about 24km/h or more and then alarmed for more than 10min, the gas-deficient tire has been seriously damaged and has great safety. Hidden dangers.
Under- or over-air tire indication is required. Ask for the location of the under- or leaking tire. This function is not specified in other foreign standards. A TPMS that only alerts and cannot indicate which tire has a problem is not limited and is not easily accepted by the user.
A quick leak alarm is required. When the tire pressure is detected to decrease at a rate greater than 30 kPa/min (not a puncture), the alarm should be reported within 1 min and the position of the leaking tire should be indicated.
The system should be able to display the current tire pressure values. There is a 25% difference between the normal value of the tire air pressure and the undervoltage alarm value (50 to 70 kPa for a normal car). Although there is no alarm, the fuel consumption and tire wear have increased. This standard stipulates that TPMS should be able to query the pressure information of each tire in real time. In this way, if the driver can inquire about the pressure information of each tire at any time, it can timely qi and take maintenance measures to reduce fuel consumption, extend tire life and eliminate safety hazards.
Signal acceptance performance and test methods are specified. When the wheel to be tested is required to be at different positions (tested every 10 °C on the circumference of 360 °C of the wheel under test), the signal from the tire pressure monitoring module should be stably received.
From the perspective of protecting the electromagnetic environment and reducing mutual interference, this standard specifies the transmission characteristics of the system wireless communication, in which the emission intensity and frequency of low-frequency and high-frequency signals are clearly defined.
Electromagnetic compatibility requirements. Requirements for electromagnetic interference performance, electromagnetic immunity, electrical transient immunity, and antistatic discharge performance are specified.
The service life of the tire pressure monitoring module. Use at least 6 years or 100,000 km.
Although the standard is a recommended national standard, compared with foreign TPMS standards, it has specific and detailed regulations on various aspects such as safety and reliability, and the technical indicators are also higher. At present, the "Car Tire Pressure Monitoring System (TPMS)" standard has been reviewed by the National Automobile Standardization Committee and reported to the AQSIQ. It will be introduced and implemented this year.
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