Monitoring of a tire by acceleration measurement

Abstract

The invention relates to the in-service monitoring of the condition of a tire of a wheel of a vehicle. To this end it proposes a process and, in particular, a device comprising: a sensor ( 4 ) mounted on the wheel, coupling means (BVF 2 , BRF 2 ) for transmitting to the vehicle indications derived from this sensor ( 4 ), and electrical energizing means (BVF 1 , BRF 1 ). According to the invention, the sensor ( 4 ) is a miniature acceleration-sensitive sensor implanted in the tread of the tire or in the vicinity of the tread. The coupling means, mounted on the wheel, then transmit indications relating to the measurements made at the moment at which the tread is in contact with the ground.

1 . Process for the in-service monitoring of the condition of a tire ( 1 ) of a wheel, characterized by the steps consisting in: 
 providing in the tire ( 1 ), near the tread ( 10 ), a miniature sensor ( 4 ), sensitive to the acceleration (γ), and    monitoring the variations in the measurement from this sensor ( 4 ), the measurements made in the zone (BC) where the tread is in contact with the ground being related to the size of this zone (BC) and, thereby, to the condition of the tire ( 1 ).    
     
     
         2 . Process according to  claim 1 , characterized in that the sensor ( 4 ) is disposed so as to be sensitive to the radial acceleration (γ).  
     
     
         3 . Process according to one of claims  1  and  2 , characterized in that the moment (TL) at which the tread ( 10 ) is in contact with the ground is registered via a sensible variation in the acceleration (γ).  
     
     
         4 . Process according to one of  claims 1  to  3 , characterized in that the period (Tp) of the moments at which the tread ( 10 ) is in contact with the ground is also detected, this period being related to the speed of rotation (V) of the wheel.  
     
     
         5 . Process according to one of the preceding claims, characterized in that a part at least of the measurements (TL, Tp) is transmitted to the vehicle by electrical, magnetic or electro-magnetic coupling.  
     
     
         6 . Process according to one of the preceding claims, characterized in that the measurements (TL, Tp) pertain at least to the period of the phases of low acceleration, and to the fraction of this period which they occupy.  
     
     
         7 . Process according to one of the preceding claims, characterized in that the sensor ( 4 ) is energized by a battery also housed in the tire ( 1 ).  
     
     
         8 . Process according to one of the preceding claims, characterized in that the sensor is energized by electrical, magnetic or electromagnetic coupling (BVF 1 , BRF 1 ).  
     
     
         9 . Process according to one of the preceding claims, characterized in that a miniature pressure sensor ( 180 ) is furthermore provided in the tire ( 1 ).  
     
     
         10 . Process according to one of the preceding claims, characterized in that a test bench is furthermore provided which is capable of reading inscriptions placed in memory in the tire ( 1 ) after the latter is dismantled.  
     
     
         11 . Device for the in-service monitoring of the condition of a tire ( 1 ) of a wheel of a vehicle, of the type comprising: 
 a sensor ( 4 ) mounted on the wheel,    coupling means (BVF 2 , BRF 2 ) for transmitting to the vehicle indications derived from this sensor ( 4 ), and    electrical energizing means (SVF 1 , BVF 1 , BRF 1 ), characterized in that the sensor ( 4 ) is a miniature sensor sensitive to the acceleration (γ), implanted in the tread ( 10 ) of the tire ( 1 ) or in the vicinity of the tread, and in that the coupling means, mounted on the wheel, transmit indications (TL, Tp) relating to the measurements made at the moment at which the tread ( 10 ) is in contact with the ground.    
     
     
         12 . Device according to  claim 11 , characterized in that the sensor ( 4 ) is disposed so as to be sensitive to the radial acceleration (γ).  
     
     
         13 . Device according to  claim 12 , characterized in that the sensor ( 4 ) is arranged so as to clip the radial accelerations (γ 1 , γ 2 , γ 3 ) toward the outside.  
     
     
         14 . Device according to one of  claims 11  to  13 , characterized in that the sensor ( 4 ) comprises pressure-sensitive means on which a metallized flexible member (r) bears, as well as a mass (m) secured to this member (r).  
     
     
         15 . Device according to  claim 14 , characterized in that the said pressure-sensitive means comprise an evacuated closed box ( 180 ) carrying the said flexible member ( 181 ).  
     
     
         16 . Device according to one of claims  14  and  15 , characterized in that the said pressure-sensitive means comprise a piezoelectric element (PC).  
     
     
         17 . Device according to one of  claims 11  to  16 , characterized in that the coupling means comprise an electronic microcircuit ( 5 ) connected to the sensor, and able to shape a part at least of the measurements therefrom, and means (RVF 2 , BVF 2 , BRF 2 ) for transmitting the measurements shaped by this electronic circuit ( 5 ).  
     
     
         18 . Device according to  claim 17 , characterized in that the transmission means (RVF 2 , BVF 2 , BRF 2 ) comprise a tuned open loop (BRF 2 ) incorporated in the tire ( 1 ), coupled to a counterpart tuned loop (BVF 2 ) mounted on the vehicle.  
     
     
         19 . Device according to one of  claims 11  to  18 , characterized in that the energizing means comprise a tuned open loop (BRF 1 ) incorporated in the tire ( 1 ), coupled to a counterpart tuned loop (BVF 1 ) mounted on the vehicle.  
     
     
         20 . Device according to one of  claims 11  to  19 , characterized in that it comprises at least one other miniature sensor ( 180 ), in particular one which is pressure sensitive, also mounted in the tire ( 1 ).  
     
     
         21 . Device according to one of  claims 11  to  20 , characterized in that the tire ( 1 ) furthermore comprises a nonvolatile memory ( 121 ), and in that the electronic circuit ( 5 ) comprises means able to write into this memory ( 121 ) historical data relating to the circumstances experienced by the tire ( 1 ).  
     
     
         22 . Device according to  claim 21 , taken in combination with  claim 17 , characterized in that the transmission means (BVF 2 , BRF 2 , RVF 2 ) are reciprocal, and in that the said historical data are written after processing on board the vehicle.  
     
     
         23 . Device according to  claim 22 , characterized in that the power delivered by the energizing means (SVF 1 ) is temporarily increased when writing the historical data.  
     
     
         24 . Tire equipped with at least one sensor ( 4 ) and with electronic circuits, according to one of  claims 11  to  23 .