| 摘要 |
The rotation of a pneumatic tire (304) is monitored by a self powered tire revolution counter (400). A piezoelectric ("piezo") element (200, 220, 340, 340', 440) is mounted in the tire in a manner so as to be subjected to periodic mechanical stresses as the tire rotates and to provide periodic pulses in response thereto. The output of the piezo element is utilized by revolution counting circuitry (460/470/480/490) to count rotations of the tire, as well as by power circuitry (450) which provides power to the revolution counting circuitry. The piezo element contains one or more piezoelectric crystals (204, 208, 224, 324) suitably made of lead zirconate-titanate ("PZT"), and is preferably in the form of a circular unimorph (disc) (340'). Output pulses from the piezo element are rectified (452), filtered (454) and regulated (456) to supply power to the counting circuitry. Prior to counting the pulses, they are passed through a low pass filter (462) for attenuating high frequency signal noise in the pulses, then through a voltage limiter (464) to limit the voltage of the pulses, then through a Schmitt trigger (466) for interfacing the pulses with a counting circuit (470), then through a one shot circuit (480) for interfacing an output of the counting circuit with a microprocessor (490). The counting circuit can be set to output a signal only upon every "n" revolutions. Nonvolatile storage, preferably in the form of an EEPROM is provided to store instructions for operating the circuitry, as well as a measured count indicative of tire rotation for transmission by optional separate telemetry apparatus (406).
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