Abstract:
A tire monitoring device includes a sensor adapted to detect airborne molecules generated when tire components are overheated. The sensor may be positioned in a reader that is proximate the exterior of the tire. The sensor may also be exposed to the air inside the pressurized tire chamber. The sensor may be tuned to detect any of a variety of molecules or components that are generated when tire materials are overheated.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims priority from U.S. provisional patent application Ser. No. 60/390,592 filed Jun. 20, 2002; the disclosures of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention generally relates to monitoring devices and, more particularly, to a tire monitoring device adapted to create an indication signal in response to an overheated tire condition. Specifically, the invention relates to a tire monitoring device having a sensor that is adapted to identify airborne molecules that are created when tire rubber becomes overheated. 
   2. Background Information 
   Various different tire monitoring devices are known in the art. The various monitoring devices are configured to sense different tire conditions such as tire pressure, temperature, revolutions, and footprint shape. One type of monitoring device is attached to the tire valve and is disposed outside the wheel. Another type of monitoring device is carried inside the wheel and may be attached to the tire or the rim. Another type of known tire monitoring device is loosely disposed within the wheel. A drawback to these devices is that it is difficult to configure them to create an early warning signal in response to the beginning of an overheated tire condition. 
   In some situations, a tire that is beginning to fail includes components that are frictionally moving with respect to each other. The friction generates heat that will raise the internal temperature of the tire. Overheated tire components break down and weaken the tire. Although monitoring devices configured to sense temperature will create a warning signal when the overheated tire condition has warmed the tire or the tire chamber to a certain level, they generally do not create a signal at the beginning of an overheated tire condition. Known tire monitoring devices will not create the warning signal at the beginning of an overheated tire condition when the temperature sensor of the monitoring device is not positioned close to the components that are creating the friction. With some prior art tire monitoring devices, the monitor will not generate an alarm signal until the overheated condition has warmed the area of the tire adjacent the temperature sensor or the internal chamber of the tire. Such warming takes time which allows the condition causing the overheating to worsen before it is detected. The art thus desires a monitoring device that is configured to sense the beginning of the overheated tire condition. 
   A current trend in the mining industry is a move towards unmanned trucks. With the precise level of control available through the current GPS systems and remote monitoring, it is possible to send equipment on hauls without the need for a human operator. Under this arrangement, the vehicle monitors various operating parameters of the on-board systems and periodically communicates the condition of on-board systems via radio to a central dispatch location. The monitored systems can include various temperatures, fluid levels, and pressures. Whenever any of these monitored parameters reach an out-of-limit level, corrective action can be taken immediately, for instance, directing the vehicle to an appropriate maintenance facility. 
   The performance of the tires must be closely monitored because the movement of the vehicle is dependent upon the tires. Typical mining applications involve operating the vehicles at the limits of designed load and operational capacity. Such conditions place the tires under continual stress. Tires not adequately inflated to the pressures required for these conditions may overheat and ultimately suffer a heat-related injury and early removal from service. 
   Tires that overheat generally begin to suffer damage as the polymer breaks down and loses structural integrity. As the polymer degrades, micro-fractures in the polymer chain begin to grow, resulting in larger cracks. These cracks then create friction that produces more heat and more damage. This process will continue and accelerate, resulting ultimately in the loss of structural integrity of the tire if the tire is not removed from service or placed in a less-severe operating environment. 
   These small pockets of micro fractures generate heat and can reach damaging levels of temperature causing breakdown of the polymer and other chemicals and additives in the rubber compound. Airborne chemicals are released and result in an odor often termed “burning rubber smell.” Many times, an overheated tire is identified first by this distinctive odor. Because these pockets of micro fractures are relatively small initially, the heat generated is insufficient to significantly raise the overall tire temperature or temperature of the contained air within the tire chamber. Therefore simple temperature detectors will not identify an overheated tire until the tire damage is relatively extreme. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention provides a tire monitoring device that is configured to generate a signal at the beginning of an overheated tire condition. The monitoring device is adapted to sense airborne molecules generated from overheated tire rubber. 
   The invention provides one embodiment of a monitoring device mounted to a reader that is brought into proximity with the subject tires. The reader may be a hand-held reader, a gate-style reader, or an on-board reader. While the tire is proximate the reader, the air immediately adjacent the tires is analyzed to allow molecules generated from overheated tire rubber to be sensed. The monitoring device generates a warning signal when the concentration of the target molecules in the air being sensed exceeds a minimum level. The invention provides another embodiment of the invention wherein a monitoring device is mounted within the tire and rim combination so that the monitoring device monitors the air within the pressurized chamber of the tire. 
   The invention further provides a method for detecting an overheated tire including the steps of sensing the air adjacent or inside the tire and creating an indication signal when the sensor detects molecules generated by overheated tire rubber. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a front view of a vehicle with a person holding a hand held reader adjacent one of the tires of the vehicle. 
       FIG. 2  is a front view of a gate-style reader with a vehicle passing through the reader. 
       FIG. 3  is a front view of a vehicle having an on-board reader positioned adjacent each of the tires of the vehicle. 
       FIG. 4  is a section of another embodiment of the invention wherein the sensor is exposed to the air in the pressurized chamber of the tire. 
   

   Similar numbers refer to similar elements throughout the specification. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The first embodiment of the monitoring device of the invention is indicated generally by the numeral  10  in FIG.  1 . In this embodiment of the invention, monitoring device  10  is in the form of a hand-held reader that may be passed adjacent tires  12  of a vehicle  14  to determine if tire  12  has overheated tire components. 
   Monitoring device  10  includes a sensor  20  that is tuned to detect the molecules generated by an overheated tire component. Monitoring device  10  may thus include a body having an opening that allows the air surrounding the body to come into contact with sensor  20 . In one embodiment, the opening passes entirely through the body so that air will be readily passed across sensor  20 . Suitable mechanisms such as fans may be used to draw air or push air across sensor  20 . In another embodiment, sensor  20  is disposed on the outside of the body of monitoring device  10 . 
   Sensor  20  is tuned to create an indication signal upon a predetermined criteria. The predetermined criteria may be a predetermined concentration of target molecules disposed adjacent the sensor. The predetermined concentration is set to be high enough to avoid false signals while being low enough to allow tire  12  to be inspected to determine if catastrophic tire damage can be avoided. The exact levels will depend on the type of tire being used with sensor  20  and the environment in which tire  12  is being used. The construction of the tire may also influence the exact settings for sensor  20 . The predetermined concentration is also set based on the distance that sensor  20  will be positioned from the tire. In the first embodiment, the user is instructed to bring monitoring device  10  within a given distance of tire  12  to obtain an accurate reading. The distance may be a half meter or within two meters depending on the calibration of sensor  20 . In other embodiments, sensor  20  may be calibrated to function within 5 meters. In the embodiments described below, the distance is fixed and sensor  20  may be calibrated to the known distance. In another embodiment of the invention, the predetermined criteria may simply be the presence of a certain molecule that is present in the air during an overheated tire condition. 
   Sensor  20  may be designed to sense any of a variety of components that are known to be created when a tire is overheated. These components may include various sulfur compounds, monomers of the polymers that are present in the tire rubber, or other compounds that are generated when tire rubber is overheated. Sensor  20  is tuned to sense only molecules generated by hot tire components so that false signals are avoided. Sensor  20  may be any of a variety of sensor types that create a signal when exposed to a gas with selected components from heated rubber. Examples of known sensors that may be used with this invention include those which use LED sensors, catalytic (hot wire), electrochemical, and Metallic Oxide Semiconductor (MOS). Other types of sensors may also be used without departing from the concepts of the present invention. 
   Sensor  20  will thus create a warning signal long before the overheated tire condition generates enough heat to trigger a temperature sensor. The early warning nature of the invention allows the tire to be saved before catastrophic damage occurs. The indication signal created by sensor  20  may be in the form of a visual light, an audible signal, or a scaled number. 
   A second embodiment of the invention is indicated generally by the numeral  110  in FIG.  2 . In this embodiment, monitoring device  110  is in the form of a gate-style reader that has one or a pair of sensors  112  disposed at tire  114  level. When the vehicle  116  passes through monitoring device  110 , tires  114  are passed adjacent sensors  112 . If one of tires  114  is overheated, the molecules generated by overheated tire rubber will be sensed by one of sensors  112  and a warning signal is created. A gate-style reader may be positioned at strategic positions in at a work site where vehicles  116  are required to pass at a known frequency. 
   A third embodiment of the invention is indicated generally by the numeral  150  in FIG.  3 . In this embodiment, monitoring device  152  is in the form of an onboard reader that is carried on vehicle  156  adjacent tire  154 . Vehicle  156  may be an automated vehicle that is operated without a driver of a vehicle similar to vehicle  116  described above. In the embodiment of the invention depicted in  FIG. 3 , a monitoring device  152  is disposed adjacent each tire  154  of vehicle  156 . In one embodiment, each tire  154  may have a monitoring device  152  on the inboard and outboard sides of the tire. In another embodiment, monitoring device  152  may be positioned directly above tire  154 . If one of tires  154  is overheated, the molecules generated by overheated tire rubber will be sensed by one of the sensors on one of monitoring devices  152  and a warning signal is created. 
   A fourth embodiment of the invention is indicated generally by the numeral  210  in FIG.  4 . In this embodiment, monitoring device  210  is positioned inside the tire  212  such that the chemical sensor is exposed to the gas disposed in the tire chamber  214 . In one embodiment, monitoring device  210  is connected to the rim  216 . In another embodiment, monitoring device  210  is connected to the tire sidewall. 
   In this embodiment, an overheated tire element will generate molecules that are dispersed into the air in chamber  214 . The chemical sensor is configured to sense these molecules and creates a warning signal that is sent outside of tire  212  by appropriate transmission devices. 
   In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
   Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described. In all of the embodiments described above, a temperature sensor and pressure sensor may be used together or in combination with sensor  20 ,  112 ,  152 ,  210 . Furthermore, various types of protective and/or supportive bodies may be used with the monitoring devices.