Abstract:
A method and system for determining the performance characteristics of at least one selected vehicle component utilizes a plurality of variables and takes into account the interrelationship of those vehicles. Specifically, a detected temperature, load and road grade condition are utilized to determine a rate of change in a performance characteristic of a selected component relative to time. The rate of change information is provided to a vehicle operator on a real-time basis and stored in memory for later use by a service technician. Determining a performance characteristic based on a plurality of variables and storing information regarding that characteristic over time provides additional useful information to a service technician enabling the technician to more quickly and effectively diagnose potential problems with the vehicle components.

Description:
BACKGROUND OF THE INVENTION 
     This invention generally relates to diagnostic systems for motor vehicles. More particularly, this invention relates to a method and system for determining a performance characteristic of a selected vehicle component based upon temperature, load, road grade and time. 
     There are a variety of commercially available diagnostic tools available to assist technicians in servicing vehicles. A variety of sensors and mechanisms have been developed to assist in monitoring the performance of vehicle components. Such sensors include speed sensors, for example, which assist in monitoring the rotational speed of a wheel axle and temperature sensors that provide indication of temperatures within vehicle fluids and lubrications. 
     Although a variety of such sensors are available, there use has not been exploited to the fullest possible extent. For example, rotational speed sensors and oil pressure sensors typically only provide information while the vehicle is in motion. When a vehicle is brought into a service establishment, a service technician does not have the benefit of the information obtained by those sensors since the last time that the vehicle has been in for service. Moreover, there are situations where combinations of sensor information can be useful but this feature has not been implemented in any useful way. 
     This invention provides an improved system and method for monitoring performance characteristics of vehicles utilizing a plurality of detected variables. Additionally, this invention provides the ability to record such information over time and later provide that information to a service technician to enhance the ability to efficiently and effectively diagnose potential vehicle problems and appropriately service the vehicle. 
     SUMMARY OF THE INVENTION 
     In general terms, this invention is a system for monitoring the performance of a selected vehicle component taking into account a plurality of variables. The system includes a first sensor supported on the vehicle that detects a temperature of the selected vehicle component. A second sensor is supported on the vehicle and detects a load supported by the vehicle. This second sensor is especially useful in heavy duty vehicles such as trucks, which carry loads of widely varying amounts. A third sensor detects the grade of the road surface along which the vehicle is traveling. An electronic controller communicates with each of the sensors and utilizes the three different variables to determine a performance characteristic of the selected vehicle component. The electronic controller also determines a rate of change of the performance characteristic relative to time and provides an output indicating that rate of change. 
     In the preferred embodiment, a display is provided within the vehicle for the driver to visibly observe the monitored performance characteristic and the rate of change of that characteristic relative to time. Additionally, the preferred embodiment includes a memory module within the electronic controller that stores data regarding the performance characteristic, the detected variables and the rate of change of the performance characteristic relative to time. When the vehicle is brought in for service, the electronic controller preferably communicates with an external computer device through a communication port supported on the vehicle so that a service technician has access to all of the data within the memory module of the electronic controller. 
     A system designed according to this invention provides improved diagnostic capabilities for a service technician and gives better performance information that otherwise is not available by utilizing information from single sensors alone. Taking into account the combined effects of temperature, load and road grade, for example, provides more realistic and useful data for a service technician to quickly diagnose a potential problem on a vehicle. 
     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiments. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic illustration of a heavy duty vehicle incorporating a system designed according to this invention. 
     FIG. 2 is a schematic illustration of a system designed according to this invention. 
     FIG. 3 is a graphical illustration demonstrating the results obtained by a system designed according to this invention implementing the method of this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 diagrammatically illustrates a heavy duty vehicle  10  including a cab portion  12  and a tailer portion  14 . As is typical, the heavy duty vehicle  10  includes a plurality of wheel axles  16  on the cab portion and trailer axles  18 . An electronic controller  20  is supported on the vehicle and communicates with a plurality of sensor arrangements  22 , which are respectively associated with each of the wheel axles. Communication lines  24  are schematically illustrated to demonstrate the communication between the electronic controller  20  and the sensor arrangements  22 . Another sensor  26  detects a road grade (i.e., incline) at a current location of the vehicle. Additionally, a display  28  preferably is provided within the cab portion  12  so that a vehicle operator can observe information provided by the electronic controller  20 . 
     FIG. 2 schematically illustrates a system  30  designed according to this invention. Each of the sensor arrangements  22  preferably includes a first sensor  32  that detects a temperature of a selected vehicle component. For purposes of discussion, the wheel axles  16  and  18  will be considered as the selected vehicle component. Those skilled in the art, however, will realize that this invention is applicable to other vehicle components such as transmission components or other portions of the drive train of a heavy duty vehicle, for example. The sensors  32  can be realized through a variety of commercially available sensors such as a thermistor supported in the oil sump of one of the axles. 
     A second sensor  34  detects a load supported by the vehicle  10 . A plurality of second sensors  34  preferably are provided so that the load can be detected at each of the wheel axles of the vehicle. A variety of commercially available sensors can be implemented such as axle load sensors that detect an amount of air pressure within the air suspension system at a given axle. 
     The third sensor  26  that detects the road grade conditions at a current vehicle location may take a variety of forms. In one example, an analog tilt sensor is supported on the vehicle and detects the road grade based upon the position of the vehicle caused by the incline in the road surface. In another example, the vehicle  10  includes a global positioning device that permits access to a global positioning database that includes topographical or altitude information regarding particular locations. In this second example, the system  30  utilizes the information from the global positioning database to determine changes in altitude between multiple locations or road grade conditions at the current vehicle location. 
     The electronic controller  20  is schematically illustrated having a central processing unit module  36 , a memory module  38  and a clock portion  40 . Those skilled in the art will realize that the “divisions” of the electronic controller  20  are for schematic, discussion purposes only and do not necessarily represent separate physical portions of a microprocessor. The clock portion  40  preferably is a real-time clock function incorporated into the electronic controller  20 . Alternatively, a time reference can be obtained from a global positioning device on vehicles where such devices are provided. 
     The electronic controller  20  communicates with the first, second and third sensors  32 ,  34  and  26 . The information gathered by the sensors is utilized by the electronic controller  20  to determine a performance characteristic of a selected vehicle component (i.e., a wheel axle). The performance characteristic takes into account combined information gathered from the individual sensors. The electronic controller  20  preferably is programmed to determine the performance characteristic and to determine a rate of change of the performance characteristic relative to time. 
     The electronic controller  20  preferably is programmed to determined whether the rate of change of the performance characteristic is outside of an expected range. The expected range of the rate of change preferably is dependent upon the variables detected through the sensors  26 ,  32 , and  34 . This invention takes into account the recognition that heavier vehicle loads and greater road inclines typically result in greater increases in wheel axle temperature, for example. Therefore, the electronic controller  20  preferably is programmed to take into account the currently detected variables from the sensors and to utilize that information to determine the current performance characteristic, the rate of change relative to time and whether the rate of change is within an expected range. 
     The electronic controller  20  preferably provides a real-time display on the display  28  for the operator of the vehicle. The display  28  preferably is a reconfigurable display that allows a vehicle operator to observe any individual detected variable or the performance characteristic determined by the electronic controller  20 . 
     Additionally, the system  30  preferably includes a communication port  42  that permits a service technician to utilize an external computer device (not illustrated) to access data from the memory portion  38  of the electronic controller  20 . This feature enables a service technician to obtain information regarding the performance characteristic and the rate of change relative to time as if the service technician were in the vehicle during operation since the last visit to the service establishment. Having such ready access to the information determined by the electronic controller  20  provides the service technician with the ability to more quickly diagnose potential problems and to address specific portions of the vehicle that may require service. Without such information, it is impractical for a service technician to manually inspect the large number of vehicle components that potentially could require service. With this invention, the service technician is able to quickly discern the portions of the vehicle that need to be addressed and serviced at a given time. Moreover, a vehicle operator is provided with a real time display of the performance characteristic and, therefore, is given the ability to determine when a vehicle may need immediate service. 
     Given this description, those skilled in the art will be able to choose from among commercially available devices to realize the sensors and the electronic controller  20 , which preferably is realized through a conventional microprocessor. Additionally, given this description, those skilled in the art will be able to develop the specific software to enable the electronic controller to perform the desired functions described in this specification. 
     FIG. 3 graphically illustrates the performance of the system  30 . A graph  50  includes a first plot  52  showing a two-dimensional map of the change in temperature relative to time of a selected vehicle component (i.e., one of the wheel axles). The plot  52  shows the rate of change of the performance characteristic for a first vehicle that is relatively heavily loaded (i.e. carrying a load of 38,000 lbs. on the drive axle tandem) and traveling along a relatively flat road surface. A second plot  54  illustrates the same vehicle driving along a road having a three percent change in grade. As can be appreciated from the illustration, the rate of change of the performance characteristic relative to time is somewhat greater in the plot  54  than in the plot  52 . Additionally, the overall temperature of the selected vehicle component is somewhat greater in the plot  54  than in the plot  52 . 
     A third plot  56  illustrates the rate of change of a vehicle having a much smaller load (i.e., total load of 1,000 lbs.) traveling along a road surface having a three percent grade change. The rate of change of the temperature relative to time and the plot  56  is much higher than shown in the plots  52  and  54 . This illustrates a potential problem in the drive axle because this is an abnormal rate of temperature increase. With this invention, the driver and a service technician will be alerted to this condition, which otherwise would not have been possible even if the temperature of the selected vehicle component were monitored. If one were to consider the temperature in isolation, the difference between the plots  54  and  56  would not be discernable because the peak temperature is approximately the same in both instances. The rate of change in the performance characteristic determined by the system  30  of this invention, therefore, provides additional diagnostic information to a service technician to realize that a portion of the vehicle drivetrain such as a lubrication line may need immediate attention and service. 
     The description just given provides an example implementation of this invention. Variations and modifications may become apparent to those skilled in the art that do not depart from the purview and spirit of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.