WWW Entwicklungen Reifendruck - BorgWarner BERU Systems ...

More documents

Recommendations

Info

DEVELOPMENT Tires and Wheels 2.2 Direct Measurement <strong>Systems</strong> Byte 1 Synchronisation 1111 1111 Byte 2 Synchronization 1111 1110 Byte 3 Identifier MSB Byte 4 Identifier Byte 5 Identifier Byte 6 Identifier LSB Byte 7 Druck / Pressure Byte 8 Temperatur / temperature Byte 9 Batterie-Restlebensdauer / Battery power indicator Byte 10 Status Byte 11 CRC MSB Byte 12 CRC LSB Termination-Bit „0˝ Within this context, the measurement cycles are defined depending on of the vehicle movement. Longer measurement cycles are possible if the vehicle is station- Table 1: Data telegram of the wheel electronics Table 2: Comparison of indirect measuring TPMS with the three Beru versions Functional features ABS supported TSS generation 2 TSS generation 2 TSS generation 3 series systems without trigger with trigger without trigger Pressure measurement in four wheels – + + + Temperature measurement in four wheels – + + + Alarm for tire defect Soft alarm (low sub- + + + + standard pressure) Hard warning (sub- – + + + standard pressure 25 %) Alarm for even loss of – + + + pressure in all wheels – + + + Alarm issued with position Automatic learning of new wheels – – + + (e. g. winter wheels) Automatic learning – +* + + of new wheel positions Rapid diagnosis of – +* + + the components Target pressure transfer for changes in pressure + + + + due to driver actions Pressure display menu with measurement + + + + values and position Immediate availability of the pressure values – – + + before start of driving Satidfies NHTSA minimum alarm thresholds and – +** + +** response time – + + + *With user invention; **when parked, the control unit must be powered via terminal 30 ary; the cycles are then cut appropriately if the vehicle is in motion and may even be measured in seconds if significant changes in the pressure are identified over time – i.e. if there is a tire defect or the tire is being inflated. The tire electronics autonomously recognizes vehicle movement using a roll switch. An alternative is a needs-based triggering of the measurement via the reverse channel to the wheel electronics. The trigger transmitters required for this are installed in the wheel arches. In addition to the clocking of measurement procedures, the trigger transmitters enable the wheel positions to be learned in a simple manner. The frequency band of around 125 kHz used for the trigger channel ensures that the range of the transmitted trigger signal remains low due to the small antenna structure in a ratio to the wavelength, which permits reliable control of the individual wheel electronics. Neighbouring wheels remain unaffected, thus enabling clear identification. Therefore, in a comparison of the direct and indirect measurement systems, Table 2, Beru recognizes the clear advantages of the direct measurement system. This was also the basis for the decision in 1995 to develop a TPMS on this technological basis. 3 Functional Components The functional components in the solution that Beru developed as an example of a modern tire pressure monitoring system include the wheel electronics, (digital) antenna, trigger transmitter and control unit. Depending on the application, user interfaces and displays are also necessary. The summary of the individual elements is presented in the schematic diagram shown in Figure 1. 3.1 The Wheel Electronics The wheel electronics unit represents the core component. This unit, which is fitted to the valve on the inside of the wheel, Figure 2, must be able to cope with extreme ambient conditions. It must be capable of withstanding temperatures of between –40°C and + 120 °C – in bursts even as high as + 150 °C – with acceleration values of up to 2,000 g. The form of the housing in contact with the valve connection is by means of a moulded spherical surface and, as such, it can be fitted to nearly all known rim types with only one design, Figure 3. The unit is encapsulated to protect it against the penetration of water and to provide resistance to chemical residue in the tires. A Teflon filter, patented by Beru, beneath a “chimney”, Figure 4, guarantees the required permeability for the interior pressure to the sensor element. The wheel electronics consist of three in- 4 ATZ 2/2005 Jahrgang 107
3 Functional Components TSS generation 2 without trigger TSS generation 2 with trigger TSS generation 3 without trigger, with compact control unit Figure 1: System description The components: wheel electronics (1), (digital) antenna (2), central control unit (3), trigger transmitter (4), compact control unit - control unit with integrated digital antenna (5) tegrated circuits. The first circuit draws on micro-mechanical structures in order to measure and digitise the values for pressure, temperature and acceleration. The value for acceleration is used as an ancillary factor. It recognizes whether the wheel is moving, so that the system can respond by switching to an aligned transmission mode. The second circuit contains a 433 MHz (or 315 MHz) transmission power stage to control the process. The transmission power is selected in such a way that the system is on the one hand suitable for certification ATZ 2/2005 Jahrgang 107 under radio regulations, while on the other hand guaranteeing the greatest possible system reserves for operations. Another module wakes up the system when it receives a trigger signal of 125 kHz, thus setting it to an active mode. 3.2 The Digital Antenna The digital antenna contains a 433 MHz (or 315 MHz) RF receiver with corresponding demodulator and data decoder. The received measurement values are transmitted to the control unit via a LIN bus interface. The ad- vantage of this concept compared to previous systems is that no RF wiring is required in the vehicle to control the tire pressure, which considerably improves the impact of electro-mechanical interference. The receiver initially transforms the 433 MHz (or 315 MHz) signal to an intermediate frequency of 10.7 MHz after preliminary filtering. This is then followed by demodulation, decoding and reformatting to the LIN protocol. The concept is designed in such a way that an adjustment of the RF circuits in series production is not necessary. 5
Page 1 and 2: www.beru.com Tire Pressure Monitori
Page 3: 1 Introduction Tire pressure monito
Page 7 and 8: place using the driver information

WWW Entwicklungen Reifendruck - BorgWarner BERU Systems ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?