Status of Domestic and Foreign Automotive TPMS Standards and Regulations

The United States is the first and only country in the world that has enacted and enforced TPMS regulations. The United States Highway Traffic Safety Administration (NTHTSA) has established FMVSS 138 regulations requiring that after September 2007, all four-passenger passenger cars and commercial vehicles sold in the United States with a maximum total design mass of 4,536 kg must be equipped with a tire pressure monitoring system. . Driven by federal legislation and market opportunities in the United States, major automotive electronics companies have invested a great deal of R&D enthusiasm. At the same time, many well-known chip manufacturing companies have joined in the process, and they have continuously introduced smaller size, lighter weight, more reliable performance, and longevity. Longer generation of products. At present, TPMS equipment in the United States has become very popular.

In March 2006, the International Organization for Standardization (ISO) developed the international standard ISO 21750:2006 on tire pressure monitoring systems. The American Society of Automotive Engineers also established the SAE J 2657 standard for lightweight vehicle tire pressure monitoring systems in December 2004. Currently referenced international automobile regulations and standards include: FMVSS 138 tire pressure monitoring system; SAE J 2657:2004 light vehicle tire pressure monitoring system; and ISO 21750:2006 road vehicle tire pressure monitoring system for improving vehicle safety.

In addition, Japan's Automotive Standardization Organization (JASO) has also developed a technical document for the TPMS real vehicle testing method. Its technical content is basically a refinement of the US FMVSS 138 regulation. The GRRF, which is responsible for the development of European and global automotive technology regulations, and the "UN/WP29", a vehicle coordination forum for the world's automotive technology, decided to establish a GRRF at the 62nd meeting in September 2007. TPMS Informal Working Group, led by Germany to promote the formulation of the regulations, and held informal working group meetings in November 2007, February and September 2008 to discuss the feasibility of formulating ECE regulations concerning TPMS From the contents of several meetings, the difficulty of this task is much greater than expected, and the pace of progress is not fast.

The advantages and disadvantages of each standard

US Federal Regulations FMVSS 138. This regulation is an enforced safety standard. Only the most basic functional requirements are stipulated in the performance requirements. That is, when the tire pressure is lower than the specified pressure value, the TPMS shall send an undervoltage visual alarm signal within 20 minutes. FMVSS 138 regulations stipulate the relevant requirements of the visual alarm signal, and also stipulate the test conditions, test procedures and detailed implementation transition period. The specific requirements for the performance of the TPMS system in the US FMVSS 138 regulations are:

a) The TPMS system must start running when the car is ignited and give an alarm when the tire pressure drops 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) When the car is ignited, a self-test of the warning light on the instrument panel must be performed.

e) The owner's manual must state the warning that the replacement tire may not be matched.

f) Automobile manufacturers must gradually increase the proportion of TPMS installed. After September 2007, four-wheel passenger vehicles and commercial vehicles with the maximum design mass not exceeding 4,536 kg sold in the United States will require 100% assembly rate.

g) specifies that TPMS conducts pressure monitoring at speeds of 50 to 100 km/h.

U.S. regulations were restricted by the technical level at the time when they were formulated. They only specified the most basic under-voltage alarm functions and took into account the indirect type (ie, the method of indirectly calculating the tire low pressure through a wheel speed sensor) TPMS system. However, due to the inadequacy of the indirect TPMS system, such as when the vehicle is stationary, it cannot be monitored and judged whether the period of the low pressure is too long (about 20 minutes), false alarms are easily generated, low pressure cannot be detected in certain special conditions, and the pressure value cannot be displayed. Therefore, products that meet the regulations are not necessarily safe and reliable products. 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 the Tyre Pressure Monitoring System (TPMS) installed in tubeless tyres. Mainly to the tire pressure monitoring sensor module temperature resistance, thermal cycle, thermal shock, extreme temperature resistance, moisture resistance, frost, pressure, rapid leak, resistance to altitude, dirt, salt spray corrosion resistance, drop resistance , mechanical shock resistance, electromagnetic compatibility, etc. specify the specific test methods, the performance of the alarm signal display method, the system's working conditions, the most basic performance gives specific requirements. The standard stipulates that the system should monitor the tire pressure between 24km/h and maximum speed.

The standard does not require measurement accuracy, there is no product life limit, and the response time for undervoltage alarms is longer (within 10 minutes). The function is basically similar to FMVSS 138.

ISO 21750:2006 standard. This standard applies to tire pressure monitoring systems for tubeless tires, requires monitoring of all used tires, and provides drivers with information. The standard specifies comprehensive performance requirements for systems and components. The standard specifies 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). Means to measure the tire inflation pressure and the internal temperature or the parameters corresponding to the pressure, and send out a message to alert the driver that the inflation pressure limit of the tire has reached a system that requires action.

Tyre Pressure Warning System (TPWS). The driver can be provided with useful information, including at least the actual state of pressure of each tire. The purpose is to warn when the tire needs to take corrective action.

Tyre Leakage Alarm System (TLAS). A system that detects significant changes in the tire pressure in use and other tire pressures and relative to its own initial air pressure requires action.

The standard defines part of the performance limits for the tire module as:

a) Service life: Use at least 6 years or 100,000 km on an accessory vehicle.

b) Measurement accuracy: The minimum accuracy of the absolute pressure measurement value shall satisfy: ±2% of the full scale in the temperature range of 0°C~70°C, the maximum not exceeding ±10kPa; ±5% of the full scale under other conditions, the maximum Not more than ±25 kPa; The tire pressure monitoring module installed inside the wheel also provides environmental performance and specific test methods. Detailed man-machine interface requirements are specified for the display module.

This standard is wider than FMVSS 138 and SAE J 2657, but does not require TPMS to work when the vehicle is stationary. It only requires the vehicle to be under the pressure within 3 minutes when the vehicle speed is greater than 25km/h, and to alarm within 10 minutes.

The above three standards put forward requirements for TPMS from different aspects, but for a highly demanding electronic product in terms of safety and reliability, these standards and regulations still have some defects in requirements. For example, how to embody and ensure the reliability and stability of system signal transmission, how to realize and ensure that the system can reach the service life of more than six years, how to avoid false alarms and missed alarms, etc. These are the difficulties in the design of TPMS systems and The key technology is also the difficulty in setting standards.

China's forthcoming TPMS standard

The research and development of TPMS products in China was later than that in the United States, Europe and other countries. Since 2002, early TPMS products have emerged in the country and generally appear in the form of foreign product agents or imitation development, and are small in scale and low in technical content. In early 2003, Shanghai Volkswagen started the TPMS R&D program, and domestic TPMS R&D entered the stage of cooperation with the OEM. After a period of independent research and development and innovation, a batch of TPMS products developed by our country have reached the level of performance and cost comparable to that of international counterparts. It can be said that China's TPMS industry has entered an independent research and development stage with independent intellectual property rights.

At present, domestic TPMS product manufacturers have gradually increased, but the product variety, type, technical level and quality are uneven. The industry urgently needs to formulate TPMS national standards to regulate and guide the sound development of the TPMS industry. Considering that the product is a relatively new technology, it is first formulated as a recommended national standard for the purpose of encouraging the application of advanced technology, and after the technology and product are further matured, it may be considered to study the feasibility of formulating a TPMS mandatory national standard. To improve the safety of the vehicle.

On July 31, 2007, the China Automotive Technology and Research Center took the lead and formed a standards drafting working group including more than ten companies including vehicle manufacturers, testing and scientific research institutions, TPMS system manufacturing companies, sensors and chip manufacturing companies. The TPMS Standards Research Working Group was established and the first working meeting" and the standard setting work was started. In May 2008, a standard draft for consultation was formed. In December of that year, a standard draft was formed.

China's "TPMS" standard content includes:

Scope of application: Applicable to all types of vehicles and tires, including passenger cars and commercial vehicles (M and N), as well as inner tubes and tubeless tires, and TPMS for other types of vehicles can also refer to the implementation (such as two rounds Motorcycles and construction machinery).

Requires a shorter undervoltage alarm time: The TPMS should be given an undervoltage alarm signal within 6 seconds. Compared with the 20 minutes specified by FMVSS138, 10 minutes specified by SAE J2657:2004 and 3 minutes specified by ISO21750:2006, the safety is improved.

Requires an undervoltage alarm at rest: In actual use, when the vehicle is parked overnight (or over a long period of time), the tire may have been in a state of serious lack of air or air. At this time, the vehicle should be alerted before the vehicle is moved. At this time, even if it is only rolling a few laps, the tires will be greatly damaged. If waiting until the car reaches 24km/h or more than 10min, then the tires have already been seriously damaged, and there is a great safety Hidden danger.

Requires under-pressure or leaky tire indication. It is required to specify the location of the underpressure or leaky tire. This function is not specified in other foreign standards. A TPMS that only alerts you but cannot indicate which tire is in question is flawed and not easily accepted by the user.

Fast leak alarm is required. When the tire pressure is monitored to decrease at a rate greater than 30 kPa/min (not a puncture), an alarm should be made within 1 min and the leaky tire location indicated.

The system should be able to display the current tire pressure value. There is a difference of 25% between the normal value of the tire pressure and the underpressure alarm value (50~70kPa for an ordinary car). Although there is no alarm at this time, the fuel consumption and tire wear have increased. This standard stipulates that the 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, he can promptly supplement the air and adopt maintenance measures to reduce fuel consumption, extend tire life, and eliminate potential safety hazards.

The signal acceptance performance and test methods are specified. When the measured wheel is at a different position at rest (tested every 10 °C on the circumference of the tested wheel at 360 °C), the signal from the tire pressure monitoring module should be received steadily.

From the point of view of protecting the electromagnetic environment and reducing the interference between them, this standard specifies the system's wireless communication emission characteristics, and it makes clear requirements for the emission intensity and frequency of low-frequency and high-frequency signals.

Electromagnetic compatibility requirements. Requires electromagnetic interference performance, electromagnetic immunity performance, electrical transient conduction immunity, anti-static discharge performance requirements.

Tire pressure monitoring module service life. At least 6 years or 100,000 km is required.

Although this standard is a recommended national standard, compared with foreign TPMS standards, there are specific and detailed provisions in terms of safety and reliability, and the technical indicators are also higher. At present, the “TPMS” standard has been reviewed by the National Automobile Standardization Committee and reported to the AQSIQ. It will be introduced and implemented this year.