Method and apparatus for tire pressure monitoring

Abstract

The relative speed of each of the tires of a vehicle is monitored as an indication of the operating state of the vehicle, wherein if the vehicle is not operating in one of a number of predetermined states, the relative speed is monitored as an indication of relative pressure of the vehicle tires, and further wherein differences in relative speed not related to the predetermined states, and not related to differences in relative pressure, are accounted for. In addition, a single tire pressure sensor is employed to account for over or under inflation of substantially equal proportion in the tires.

1 . A method for indicating a pressure loss condition in tires of a vehicle, each tire having a speed related to vehicle speed and to vehicle operating condition, the method comprising: 
 storing a predetermined number of tire speed patterns, each tire speed pattern representing relative tire speed conditions corresponding to a respective normal vehicle operating condition which results in tire speed variations;    storing a predetermined tire pressure for the tires;    storing a respective tire speed pressure loss pattern for each tire representing a relative tire speed condition when said tire is experiencing a pressure loss condition:    sensing the speed of each of the tires;    sensing the pressure of a single tire of the tires;    sensing if the vehicle is turning:    determining an actual tire speed pattern from the sensed speeds of the tires representing an actual relative tire speed condition; and    determining if the actual tire speed pattern corresponds to any one of the stored tire speed patterns based on whether or not the vehicle is turning, and 
 (A) if not, determining whether there is a pressure loss condition in the tires by comparing the actual tire speed pattern with the stored tire speed pressure loss patterns and indicating a pressure loss condition when the actual pattern corresponds to at least one of the stored tire speed pressure loss patterns, and  
 (B) if so, bypassing the step of determining whether there is a pressure loss condition.  
   
     
     
         2 . The method of  claim 1 , further comprising storing a respective tire speed pressure loss pattern for each tire representing a relative tire speed condition when said tire is experiencing a pressure loss condition, and wherein the determining a pressure loss condition includes comparing the actual tire speed pattern with the stored tire speed pressure loss patterns and indicating a pressure loss condition when the actual pattern corresponds to at least one of the stored tire speed pressure loss patterns.  
     
     
         3 . The method of  claim 1 , further comprising comparing the sensed tire pressure of the single tire with the predetermined tire pressure for the tires and indicating a pressure loss condition when a difference therebetween exceeds a predetermined threshold value.  
     
     
         4 . The method of  claim 1 , wherein the determining if the actual tire speed pattern corresponds to any one of the stored tire speed patterns includes employing a steering sensor configured to determine whether the vehicle is turning.  
     
     
         5 . The method of  claim 1 , wherein the determining if the actual tire speed pattern corresponds to any one of the stored tire speed patterns is bypassed when a steering sensor indicates a straight vehicle heading and 
 (A) determining whether there is a pressure loss condition in the tires in accord with the actual tire speed pattern and the sensed tire pressure, and    (B) if so, bypassing the step of determining whether there is a pressure loss condition.    
     
     
         6 . An apparatus for indicating a pressure loss condition in tires of a vehicle, each tire having a speed related to vehicle speed and to vehicle operating condition comprising: 
 a first memory storage configured to store a predetermined number of tire speed patterns, each tire speed pattern representing relative tire speed conditions corresponding to a respective normal vehicle operating condition which results in tire speed variations;    a second memory storage configured to store a predetermined tire pressure for the tires;    a steering sensor configured to determine whether the vehicle is turning;    a wheel speed sensor comprising at least one of a wheel speed sensor a wheel rotation sensor, a wheel position sensor, a rotary encoder, a temperature sensor, a steering wheel, a differential, and a wheel slip sensor, in operable communication with each tire, each of the corresponding wheel speed sensor configured to sense the speed of each respective tire and generate a corresponding signal indicative thereof;    a single tire pressure sensor in operable communication with a single tire, said tire pressure sensor configured to generate a signal indicative of a tire pressure of the single tire; and    a controller configured to receive the signals indicative of wheel speed and single tire pressure, the controller being configured to determine an actual tire speed pattern from the sensed speeds of the tires representing an actual relative tire speed condition, the controller being configured to compare the actual tire speed pattern to the stored tire speed patterns, and configured to compare the sensed tire pressure to the stored predetermined tire pressure,    wherein the controller determines whether there is a pressure loss condition of the tires in accord with the actual tire speed pattern and sensed tire pressure, the pressure loss condition being operative upon occurrence of at least one of the actual tire speed pattern not corresponding to any one of the stored tire speed patterns and the steering sensor indicating the vehicle is not turning.    
     
     
         7 . The apparatus of  claim 6 , further including a steering sensor configured to determine whether the vehicle is turning, wherein the pressure loss condition is operative when the steering sensor indicates the vehicle is not turning.  
     
     
         8 . The apparatus of  claim 6 , further comprising a third memory storage configured to store a respective tire speed pressure loss pattern for each tire representing a relative tire speed condition when said tire is experiencing a pressure loss condition, and wherein the pressure loss condition is configured to compare the actual tire speed pattern to the stored tire speed pressure loss patterns, and configured to indicate a pressure loss condition if at least one of the actual tire speed pattern corresponds to at least one of the stored tire speed pressure loss patterns and the difference between the sensed tire pressure of the single tire and the predetermined tire pressure for the tires exceeds a predetermined threshold value.  
     
     
         9 . The apparatus of  claim 6 , wherein each of the corresponding wheel sensors comprises at least one of a wheel speed sensor, a wheel rotation sensor, a wheel position sensor, a rotary encoder, a temperature sensor, a steering wheel, a differential and a wheel slip sensor.  
     
     
         10 . The apparatus of  claim 6 , wherein said single tire pressure sensor is operable to provide a measured pressure output to said controller via a wireless communication link.  
     
     
         11 . The apparatus of  claim 6 , wherein said controller includes a microprocessor.  
     
     
         12 . The apparatus of  claim 6 , wherein said single pressure sensor includes a pressure transducer, and a transmitter.  
     
     
         13 . The apparatus of  claim 12 , wherein said transmitter of said pressure sensor comprises a radio frequency transmitter.  
     
     
         14 . The apparatus of  claim 13 , wherein said controller includes a radio frequency antenna and receiver circuitry.  
     
     
         15 . The apparatus of  claim 6 , wherein said set of tires includes four tires of a vehicle and said self training tire pressure monitoring system comprises a single pressure sensor and first, second, third and fourth wheel sensors.  
     
     
         16 . The apparatus of  claim 15 , wherein each of said first, second, third and fourth wheel speed sensors is positioned at a corresponding one of said at least four tires of the vehicle and said single tire pressure is mounted with respect to one of the tires of the vehicle.  
     
     
         17 . The apparatus of  claim 6 , wherein said controller is positioned at, within or on an interior rearview mirror assembly of the vehicle.