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Passive pick-up device for monitoring the state of the tire of a vehicle wheel and measuring the rotation characteristics of the wheel

  • US 5,231,391 A
  • Filed: 11/19/1991
  • Issued: 07/27/1993
  • Est. Priority Date: 11/30/1990
  • Status: Expired due to Fees
First Claim
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1. A device for monitoring a state of a tire of a vehicle wheel and for measuring rotation characteristics of the wheel, comprising:

  • an encoder assembly securely attached to a rotating part of a hub of a wheel, the encoder assembly including a multipolar magnetic ring provided with magnetized segments of different polarity distributed circumferentially in a regular and alternating manner, and a transmitter coil mounted coaxially with the multipolar magnetic ring on the rotating part of the wheel hub;

    a fixed pick-up means cooperating with the encoder assembly to deliver a signal representing the rotation characteristics of the wheel and a state of the tire;

    monitoring means for monitoring the state of the tire of the wheel in rotation adapted to modify characteristics of the encoder assembly depending on a value of a predetermined parameter of the state of the tire;

    wherein the transmitter coil is energized with an alternating electric current either only when the value of the parameter monitored is considered to be abnormal with respect to a critical threshold, or continuously, the transmitter coil generating a magnetic field superimposing itself on a magnetic field created by the multipolar ring, whereby the frequency of the alternating current is situated outside a range of frequencies relating to variations in the magnetic field generated by the multipolar ring in rotation with the wheel, the amplitude of the magnetic field created by the transmitter coil being proportional to the value of the parameter monitored.

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