Application of the hottest tire pressure sensor

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Application of tire pressure sensor at the beginning of the new century, because the two sides of firetone also said that they would give full play to the strong basic research advantages of colleges and universities and the engineering advantages of enterprises in R & D and production, a large number of tire blowout and rollover accidents caused more than 100 deaths and 400 injuries, which attracted the attention of the automotive industry and the U.S. government. The company had to recall 6.5 million tires in August the following year. According to statistics, 260000 traffic accidents in the United States are caused by low tire pressure or leakage every year, accounting for 75% of traffic accidents. 70% of traffic accidents on highways in China are caused by flat tires

tire quality experts believe that "maintaining standard tire pressure and finding tire leakage in time are the key to prevent tire blowout." At present, the popular low-cost hand-held digital tire pressure gauge can not ensure the timely detection of tire leakage. The indirect measurement technology currently used in more than 2 million GM and Ford vehicles - using the anti seize brake tire speed sensor to measure and compare the speed of each tire, so as to infer whether the tire pressure is insufficient is troublesome and inaccurate

the smart tire with tire pressure monitoring sensor and RF transmitter installed in each tire is attracting great attention. The smart tire cooperates with a receiver and display on the vehicle dashboard to form a tire pressure monitoring system, namely TPMS (tire pressure monitoring system), which can also be directly called tire pressure monitoring sensor

the mandatory federal act of the National Highway Safety Administration in the mid-1970s has contributed to the popularity of automatic fuel injection systems and the first climax of automotive sensor applications. Another federal act of NHTSA in 2002 stipulates that American cars will be equipped with TPMS system at the proportion of 15%, 35%, 65% and 100% each year from 2003 to 2006, which will set off a new upsurge in the application of automotive pressure sensors

tire pressure sensor

the unique working environment conditions of the tire determine the high requirements of the pressure sensor for real-time tire pressure monitoring, which requires wide temperature range, wide power supply voltage range, high practical overall accuracy, low power consumption, wireless signal transmission, bad environment resistance and low cost

Motorola is an active developer of TPMS system. It adopts silicon integrated capacitive pressure sensor mpxy8020a based on MEMS technology as the tire pressure detection unit, which has the characteristics of low power trapezoidal screw loss and full integration. MC68HC908RF2 in 32-pin package is used as the signal control processing and transmitting unit. It is a device integrated with 8-bit MCU and UHF Transmitter, and mc33594 is used as the receiving unit

Ge novasensor, a famous sensor manufacturer acquired by General Electric in recent years, is another active developer. It uses a silicon piezoresistive pressure sensor based on MEMS technology as the tire pressure monitoring unit, equipped with a special CMOS large-scale integrated circuit that can complete control, measurement, signal compensation and adjustment, and transmission. The two chips are packaged in a standard 14 pin SOIC package, which constitutes its TPMS. The model is npxc01746. Due to the wake-up transient working mode, its power consumption is only 9.7 μ A/s during measurement, which can meet the working life of the battery for ten years. Due to the digital compensation function, the pressure measurement accuracy is better than 1.5% FS in the range of -40 ℃ ~+125 ℃, battery voltage 2.1v~3.0v, The greater significance of Nova mode is that it can adopt the existing ASIC and any integrated Wheatstone full bridge piezoresistive pressure sensor to produce more models of TPMS products

Norway's sensornor company specializes in manufacturing special integrated sensors based on piezoresistive pressure, which are made into TPMS by tire pressure monitoring system suppliers such as TRW Automotive and smartire. The TPMS formed by the combination of sensornor's piezoresistive tire sensor and smartire's RF generator has been adopted by Siemens VDO auto parts company and Goodyear Tire Company of the United States

design and development of tire pressure sensor force sensitive chip

in order to develop tire pressure sensor, we have designed and developed a suitable absolute pressure sensor, which is a micro Piezoresistive Absolute Pressure Sensor Based on MEMS silicon micromachining technology. The sensitive element is the integrated Wheatstone full bridge. Figure 1 is the top view of its sensitive element, figure 2 is the cut surface diagram, and the size of its force film is 620 × 620um, 40um thick. According to the conventional design, the force sensitive resistors are distributed at the center points of the four edges of the square silicon film, arranged in the crystal direction of < 110 >, one pair is in the longitudinal layout, and the other pair is in the tangential layout, so as to form the full Wheatstone strain bridge. The resistance bar is 8um wide and 60um long. The average effective stress of the first plane can ensure the output sensitivity of 20mV/v. The resistance is formed by ion implantation doping, which has excellent uniformity and doping accuracy to ensure the stability of zero position and sensitivity. The impedance of the resistance design is 5K Ω. The vacuum reference cavity of the absolute pressure sensor is formed by silicon silicon bonding technology. Compared with the absolute pressure reference cavity formed by silicon Pyrex glass anodic bonding, it has a better matching of thermal expansion system, so it is more conducive to the thermal stability and time stability of products. Another major advantage of using this design technology is that the size of the unit chip can be greatly reduced. The size of the unit chip in this design is 1mm × 1mm, more than 7000 force sensing element units can be fabricated on a four inch silicon wafer, while the unit chip size of silicon glass bonding design is generally 1.5 × 1.5mm to 2.2 × 2.2mm, so 3400 and 1600 pressure sensor units can be made on a four inch silicon wafer. Obviously, our design is conducive to reducing the production cost of units. Of course, the premise of adopting this design is to master silicon silicon bonding technology and thin silicon diaphragm manufacturing technology. In view of the large range of the tire pressure sensor and the thick silicon film, it is not difficult to meet the design requirements by using precision mechanical thinning or isotropic corrosion technology. Even if the designed range is extended to the range of map and AAP absolute pressure sensors for automobiles, it is not difficult to obtain 15~20um thick silicon film by using smart cut technology or epitaxial electrochemical selective corrosion technology

the main manufacturing process of this pressure sensitive chip is as follows: (omitted)

the development of this pressure chip has been completed. The basic performance of the pressure sensor packaged with this chip is as follows: (omitted)

nonlinearity: 0.05~0.1

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