Tire pressure monitoring system

from Wikipedia, the free encyclopedia

Tire pressure monitoring systems (abbreviated to TPMS, TPMS or RDC; English T ire p ressure m onitoring s ystems (TPMS) ) are used to monitor tire pressure in motor vehicles in order to prevent accidents caused by incorrect tire pressure. Butt fractures z. B. when driving on curbs, are not recognized. In addition, with the optimal tire pressure you can save fuel and avoid unnecessary tire wear. As an extension to pure monitoring, off-road vehicles and trucks in South America occasionally have a tire pressure control system .

In direct systems, measurements are actively carried out with an electronic sensor in the tire; in indirect systems, the wheel speed fluctuations are recorded passively .

Indirect systems

Indirect systems passively deduce a pressure loss from the speed of the wheels. In order to obtain the necessary data, the sensors already present in vehicles are used. The wheel speeds for ABS , ESP and ASR are scanned with a toothed disk and a Hall sensor . Indirect systems are therefore usually integrated in the ABS / ESP control unit, and in isolated cases there are also solutions in their own control units.

Indirect systems use two physical effects for pressure monitoring:

  • Rolling circumference: In the event of a pressure drop in a tire, its outer diameter decreases, which increases the speed of this wheel in relation to the others. It is thus determined when a wheel rotates faster than the other three wheels due to air loss in the tire. This increase in speed is interpreted as a pressure drop and the driver is warned. Since this effect is only based on the comparison of the wheel speeds with each other, a simultaneous loss of pressure in all tires (e.g. due to neglected tire pressure control by the user) is not recognized.
  • Frequency effect: The wheels have a characteristic oscillation mode that can be interpreted as an oscillation between the tire belt and the rim. Since this oscillation is pressure-dependent, a shift in this oscillation indicates a loss of pressure. Since this effect is specific to each wheel, pressure losses in all four tires can also be detected at the same time ( diffusion ). The vibrations are recorded by the Hall sensor, which has to be queried at a significantly higher frequency than the tire speed.

With all indirect systems, a reset must be carried out by the driver when the air pressure is adjusted or other tires are fitted. The system then learns the current system behavior as a reference. During the first phase after a reset, the system monitors the wheel speeds and frequencies and saves them. In further driving operation, the occurring values ​​are compared with the learned values. As soon as a certain change occurs, the driver is warned. Thus, changes to the target are considered for both effects (rolling circumference, frequency effect) - a measurement of the pressure is not possible.

The legal requirements according to ECE R64 and FMVSS 138 are met by the systems that use both effects. Well-known vehicle manufacturers have homologated these systems and equip their vehicles with them as standard.

Many suppliers are working on indirect tire pressure monitoring systems, the best known are NIRA Dynamics AB, Sumitomo Rubber Industries and DUNLOP TECH.

As an extension of the tire pressure control, a loose wheel can also be detected with a similar software . Loose wheel indicator .

Direct systems

VDO tire pressure sensor for cars
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TPMS back side.jpg
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The active sensor is connected to the valve - which also serves as an antenna. Pressure measuring system, electronics and voltage source are hermetically sealed by a potting compound in the housing, so that when the voltage source is used up (approx. After ten years or 225,000 km) the sensor must be completely replaced.

In direct measurement systems, a pressure sensor actively records the internal pressure and the air temperature of a tire. This information is transmitted to a control unit in the vehicle by radio at certain intervals together with an identifier . These systems can detect pressure losses on all tires as they directly monitor the pressure. Depending on the display concept, the driver receives information about the current pressure value in plain text, which he either sees constantly in the display, or can query by pressing a button, or just a warning if the tire pressure is too low.

The following systems are currently available for attaching the sensors:

  • In the OEM market:
  • As retrofit solutions:
    • Attachment to the rim using a steel or plastic tape
    • Fixing on the valve instead of the valve cap
    • Replacement of the existing valve by a valve with an integrated sensor

For fastening on the inside of the valve, the radio sensors are screwed onto the base of specially designed metal valves; the tire must be removed for this; The easiest way to do this is to mount new tires. The imbalance that (about 40 grams) produced by the sensor weight is the balancing compensates the wheel. The TPMS modules can be triggered with a low-frequency signal in order to ensure pressure monitoring even when the vehicle is stationary or automatic assignment of the module positions . For this purpose, low-frequency antennas are built into the wheel arches. The sensor batteries have a service life of around seven to ten years; then the sensor has to be replaced, as the batteries cannot be changed. Lithium cells are used.

When fastening by means of a tape, it should be noted that this type of attachment only works reliably if there is a thinner point on the rim and the retaining tape is professionally attached, as otherwise the sensor will "slip" or the Band can come. This can destroy the tire from the inside within a short time. For this reason, the fastening concept using tape is rarely used.

Valve cap radio sensors are screwed onto rubber valves instead of the normal valve caps. They weigh only 10 grams (including the battery) and the battery can be easily replaced. When screwing on it must be ensured that the sensors must not protrude from the rim contour; often a shorter rubber valve simply has to be fitted. Here, too, the wheels should be balanced with the sensors. The valve cap sensors can easily be changed from summer to winter bikes and vice versa. The advantages of these systems are their ease of use. The disadvantage is that at higher speeds the valve is heavily loaded by the centrifugal acceleration that occurs. Therefore, these systems are only recommended for slower vehicles.

For future systems, various manufacturers are developing modules that are glued directly into the tire. This avoids difficulties that can occur during the assembly of rim modules (e.g. leaks on the valve or destruction during assembly). Furthermore, with a module position on the tire, it is possible to transfer tire data to the vehicle (e.g. DOT number or speed index ). With the help of this tire information, on the one hand control systems such as vehicle dynamics control or anti-lock braking systems can be adapted, and on the other hand the driver receives convenient information about his tires. In principle, these tire modules can also be supplied with voltage via batteries like conventional modules. However, work is also being carried out on piezo-based generators that provide the necessary operating voltage in the tire to operate the modules.

Pros and cons, costs

The advantages and disadvantages between direct and indirect systems are essentially the costs and the range of functions. In contrast to indirect systems, systems measuring directly require their own hardware in the form of a control unit and a sensor module with a battery in each tire. For an additional set of (winter) tires, the sensors cost 250 to 300 €, also if the batteries are empty after a few years. This also creates additional electronic waste . Each time a tire is changed, the sensors have to be taught in using a TPMS programming device, which is why a tire change costs 50 to 100 € more.

Direct systems are therefore more expensive, but work more accurately. Indirect systems use hardware that is already available in the vehicle; only the software is expanded. This cost advantage continues in operation, since no modules with empty batteries have to be replaced.

A field study found that cars with a tire pressure monitoring system are somewhat less likely to have insufficient pressure than those without. There was no significant difference between the systems.

The radio transmission (in Europe around 433 MHz) in direct systems is largely unencrypted and unsigned. It can be intercepted and evaluated with relatively little effort from a distance of up to 40 m.

car brands

With an indirect system

  • Seat, Škoda, Mazda, Honda have only installed indirect systems so far.
  • Audi and VW have an indirect system in almost all models, with the exception of a few S and R models at Audi, as well as some A8 (D4) and VW the Touareg II and Crafter
  • Fiat has almost only indirect systems.

With an exclusively direct system

Peugeot and Citroen have installed indirect systems in cheap vehicles and direct systems in more expensive vehicles.

Legal situation

United States

In the United States , tire pressure monitoring systems have been required for all new vehicles (cars, trucks, buses) with a gross vehicle weight of up to 10,000 lbs (4,536 kg) since 2007  . The National Highway Traffic Safety Administration (NHTSA) FMVSS 138 also describes the precise requirements that must be met by direct and, to a certain extent, indirect systems.

EU

In Europe, the European Union introduced similar legislation through EU Regulation No. 661/2009. With ECE regulation No. 64, which came into force on August 19, 2010 , all newly homologated vehicle models must be equipped with a tire pressure monitoring system since November 1, 2012 . Such a system has been mandatory for all new vehicles since November 1, 2014.

In Austria, the BMVIT wants to grant a three-year transition period: Before November 1, 2017, a missing or defective control system will still be assessed as a minor defect in the § 57a inspection, so the vehicle (passenger car or light commercial vehicle) receives the "sticker" and is allowed to continue, then as a serious defect that needs to be remedied. A spare or spare wheel does not require a pressure control system.

Web links

Individual evidence

  1. ↑ Tire Pressure Control (RDC). BMW Motorrad Germany , accessed March 14, 2018 .
  2. ↑ Car champion John Wiesinger: tire pressure monitoring systems TPMS / TPMS. In: kfztech.de. April 29, 2019 .;
  3. ↑ Patent EP1272365 : tire pressure estimation . ( PDF ). ‌
  4. ↑ Robert Sünder: Development of an optimized process for tire protection for indirect tire pressure monitoring systems . Ed .: Prof. Dr.-Ing. Günther Prokop . Cuvillier, 2018, ISBN 978-3-7369-9712-7 ( cuvillier.de [PDF]): “Both the direct and the indirect systems of the 2nd generation discussed in the present work meet the legal requirements in the USA and in of the EU. "
  5. ↑ Patent DE102015000998 : Detection of a loose wheel. ‌
  6. ↑ Johannes Wiesinger: TPMS tire pressure monitoring systems. In: www.kfztech.de. Retrieved April 25, 2016 .
  7. ↑ Winter tires: expensive fun thanks to tire pressure sensors. In: Deutsche Handwerks Zeitung. November 13, 2017, accessed November 3, 2019 .
  8. ↑ a b c Lena Trautermann: TPMS compulsory: Tire change with tire pressure monitoring system. In: Autobild. September 11, 2018, accessed October 31, 2019 .
  9. ↑ TPMS and Tire Inflation Pressure Field Study 2016/2017. In: itpmsadvantage.com. September 19, 2017, accessed November 3, 2019 .
  10. ↑ Read out TPMS sensors. Chaos Computer Club Aachen, accessed on October 29, 2014 . .
  11. ↑ a b Currently offered car model series with directly and indirectly measuring tire pressure control systems. ADAC, November 1, 2016, accessed October 31, 2019 .
  12. ^ Office of Regulatory Analysis and Evaluation Plans and Policy: Tire pressure monitoring system. FMVSS No. 138. ( Memento of March 2, 2013 in the Internet Archive ) (July 2001; PDF, 330 kB).
  13. ↑ Regulation (EC) No. 661/2009 of the European Parliament and of the Council of July 13, 2009 on the type approval of motor vehicles, motor vehicle trailers and of systems, components and independent technical units for these vehicles with regard to their general safety , accessed on March 14 2018
  14. ↑ Regulation No. 64 of the Economic Commission for Europe of the United Nations (UN / ECE) - Uniform conditions for the approval of vehicles with regard to their equipment with a complete spare wheel, run-flat tires and / or a run-flat system and / or a tire pressure monitoring system , accessed on March 14, 2018
  15. ↑ http://www.oeamtc.at/portal/reifdruck-kontrollsysteme+2500+1607190 tire pressure control systems, ÖAMTC, June 23, 2014, accessed on October 27, 2014.
  16. ↑ Archived copy ( Memento of October 27, 2014 in the Internet Archive ) Technical innovations, For typing from November 1, 2012, ÖAMTC, October 30, 2012, accessed on October 27, 2014.
  17. ↑ http://ooe.orf.at/news/stories/2675885/ Tire pressure control system compulsory for new cars, ORF.at, October 27, 2014, March 14, 2018 available.