Starting in 2003, a NHSTA regulation will require tire inflation monitoring on all light duty vehicles sold in the U.S. Direct tire pressure monitoring (TPM) using in-tire pressure sensors with an RF data link have proven to be the best approach to measuring tire pressure over the widest range of operating conditions. However, these systems need a battery power source requiring an overall life exceeding 10 years. Power management is therefore critical for providing a low cost, small size, and lightweight wheel sensor. These sensors are fabricated by silicon with the physical sensing mechanism being either a variable resistance or capacitance; and the fabrication technique is either 'bulk' or 'surface' micro-machined. The variable resistance type uses the piezo-resistive nature of silicon to convert stress in a small diaphragm into a very small resistance change. Bulk micro-machining methods are used where the backside of a silicon wafer is etched to form a thin diaphragm on the top surface. The range of pressures measured within the tire is usually from 150 to 300 kPa for passenger cars and from 300 to 800 kPa for light duty trucks. Data taken on tires and wheels in various mission profiles has indicated that the majority of TPM operation occurs in the temperature range of -10 to +60 deg. C, but there are common excursions as low as -40 deg. C and as high as 125 deg. C. The time varying temperature profile over a 10-year period would be quite difficult to simulate for the most common battery type being a lithium 'coin' cell mounted either directly to a printed circuit board or encapsulated separately. Therefore, a simpler approach by determining the temperature range expected in each functional mode, by determining the temperature with highest impact on battery capacity within this temperature range, and by assuming this worst case temperature for the complete time spent in each functional mode gives a worst-case analysis with some margin for operation at less severe temperatures. The modelling of the battery life is summing up sequences of events over time including all variations for temperature and supply voltage and accounting for the total time spent in all of the functional modes. Experience to date suggests that the main users of battery capacity are the RF transmissions and any source of long term stand-by current. In this respect, stand-by currents must not consume more than 50% of the capacity over the 10-year lifetime and RF pulse currents causing batteries reach end-of-life sooner than a lower level steady-state current must be minimised in that data processing speed is being optimised to match concurrent task times. Also the battery technology is critical, i.e. when operating at temperatures over 85 deg. C, the lithium BR chemistry should be employed.


    Zugriff

    Zugriff über TIB

    Verfügbarkeit in meiner Bibliothek prüfen

    Bestellung bei Subito €


    Exportieren, teilen und zitieren



    Titel :

    Considerations to improve battery life in direct tire pressure monitoring


    Weitere Titelangaben:

    Betrachtungen zur Verbesserung der Batterielebensdauer bei der direkten Reifendrucküberwachung


    Beteiligte:
    Shaw, M.L. (Autor:in)


    Erscheinungsdatum :

    2002


    Format / Umfang :

    10 Seiten, 9 Bilder, 1 Tabelle, 1 Quelle




    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch






    2002-01-1078. Considerations to Improve Battery Life in Direct Tire Pressure Monitoring

    Shaw, M. L. / Society of Automotive Engineers | British Library Conference Proceedings | 2002


    DIRECT TIRE PRESSURE MONITORING

    BARRILADO ANDRES | Europäisches Patentamt | 2016

    Freier Zugriff

    Direct tire pressure monitoring

    BARRILADO ANDRES | Europäisches Patentamt | 2018

    Freier Zugriff