Abstract:
Methods and apparatus are provided for relearning associations between tire pressure detectors and tire locations on an automobile. An apparatus comprises tire pressure detectors installed on each wheel having a tire, each configured to transmit a unique identification code in response to a tire pressure change greater than a predetermined magnitude in a predetermined time. The apparatus also includes a monitor having a receiver for receiving and a memory for storing the transmitted identification codes and a processor for associating the identification codes with predetermined locations. A method comprises exciting the tire pressure detectors in a predetermined sequence while monitoring transmitted identification codes. The method may further include storing the received unique identification codes in a predetermined order corresponding to the predetermined sequence.

Description:
TECHNICAL FIELD 
     The present invention generally relates to monitoring tire pressure in a vehicle such as an automobile. The present invention more particularly relates to re-learning associations between tires and tire locations in response to a change, such as rotating the tires on a vehicle. 
     BACKGROUND 
     To improve safety, reduce tire wear, and increase fuel economy, certain classes of motor vehicles are required or soon will be required by statute to have tire pressure monitoring systems. Each tire at each location on the motor vehicle has a pressure which is communicated as pressure data to the driver. A pressure sensor and other associated circuitry may be specific to each wheel and the tire mounted thereon. It is generally necessary to be able to identify which sensor reading is coming from which location on the motor vehicle. The problem of associating tires and tire pressure sensors with tire locations is complicated by the fact that tires may be moved from one location to another, such as in tire rotation, and the original associations made meaningless. Most conventional methods of relearning associations between tires and tire locations require special tools or addition of interrogation devices at each tire location, thereby increasing the cost of the tire monitor. 
     Accordingly, it is desirable to provide a tire pressure monitoring system adapted to relearn associations between tire pressure sensors and tire locations. In addition, it is desirable to reduce the amount of hardware that is added to the motor vehicle to achieve relearning and to eliminate the need for specialized tools in the relearning process. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
     BRIEF SUMMARY 
     According to various exemplary embodiments, a tire pressure monitor (TPM) receiver is provided. The electronic automotive tire pressure monitor receiver is configurable for relearning associations between tire pressure transmitter identification codes and locations for vehicle tires, where the relearning is based at least partially upon user-supplied tire pressure changes to each tire in a predetermined order. 
     According to further embodiments, a method is provided for relearning associations between a plurality of tire pressure transmitters and a plurality of locations for tires, the method comprising the step of sequentially interrogating by an operator, in a predetermined order, tire pressure detectors at each location of the plurality of locations for tires to induce transmission of tire-specific identification codes to a monitor configured to store the identification codes in association with the locations for tires. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements; 
         FIG. 1  is a diagram of an exemplary embodiment of a tire pressure monitoring system; 
         FIG. 2  is a diagram of an exemplary embodiment of a tire pressure detector; 
         FIG. 3  is a block diagram of an exemplary embodiment of a tire pressure monitoring system; and 
         FIG. 4  is a flowchart of an exemplary embodiment of a method of relearning associations between tire pressure sensors and tire locations on a vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
       FIG. 1  shows a side elevation of exemplary motor vehicle  100  having wheel  104  with tire  106  mounted in the right front location  112  and wheel  124  with tire  126  mounted in the right rear location  114 . Each wheel  104 ,  124  has a tire pressure detector  102  and  122 , respectively, communicating with a tire pressure monitor receiver  130 . Tire pressure detectors  102  and  122  may be electronic, electromechanical, or other devices coupled to a valve stem or which may replace a valve stem of wheels  104 ,  124 . Tire pressure detectors  102 ,  122  suitably include one or more pressure sensors, which are any devices capable of sensing pressure in tires  106 ,  126  in conjunction with a transmitter, such as an RF transmitter. In embodiments adaptable to legacy tire designs, the tire pressure detectors  102  and  122  in the wheels  104  and  124  may be coupled to a tire valve stem in the conventional way. Alternatively, other configurations for tire pressure detectors  102  and  122  are also contemplated within the present invention. For example, in particular embodiments, a tire pressure detector  102  may be installed through the tire wall or bead or may be manufactured into the tire wall or bead of tire  106 . Tire  126  similarly has tire pressure detector  122  which may also be mounted in the same manner as tire pressure detector  102 . Tires on the opposite side of the motor vehicle, not shown, are similarly configured. It will be appreciated that tires are normally filled with air, but that other gases or fluids, such as dry nitrogen or water, may be used. The type of gas or gases used to pressurize the tire is not a limitation of the present invention. 
       FIG. 2  shows tire pressure detector  122  in more detail. Tire pressure detector  122  suitably includes a valve stem  158  and a housing  150  coupled to the valve stem. The valve stem  158  transfers air into and out of the tire in any conventional manner as shown by the double arrow in  FIG. 2 , and also may serve as an antenna. Valve stems  158  which serve as antennas are typically made of metal. In an alternate embodiment, the valve stem may be an antenna support for a discrete antenna. The housing  150  contains, at least in part, the pressure sensor  152  coupled to a processor  154  coupled to a transmitter  156  coupled to the antenna/valve stem  158 . 
     Pressure sensor  152  senses the pressure in the tire and makes pressure measurement data available to processor  154 . The pressure sensor  152  may be of any conventional type appropriate for the pressure range of the tire. The tire pressure detector  122  also includes a processor  154  which controls the transmitter  156 . The processor  154  normally controls the transmitter  156 , as appropriate, to transmit the sensed tire pressure periodically. For example, the processor  154  may control the transmitter  156  to transmit tire pressure data once every minute. The processor  154  also determines if a rapid change in tire pressure has occurred and controls the transmitter  156  to responsively transmit the unique ID number, pressure change identifier and, optionally, the tire pressure data to the monitor receiver  130 . A rapid change in tire pressure could occur as a result of pumping air into the tire  106 ,  126  from an air hose at a filling station, releasing air from the tire  106 ,  126  by depressing the valve pintle in the conventional manner, or from a leak or a sudden temperature change. For example, a tire pressure change of 1.6 psi or so over a period of twenty seconds may initiate a responsive data transmission. Tire pressure change magnitudes over periods of time may be adapted for particular sizes and types of tires and tire pressures. 
     Transmitter  156  transmits tire pressure data and unique tire pressure detector identification codes to the tire pressure monitor receiver  130  over links  108  and  128 , respectively. Each tire pressure detector, including detectors  102  and  122 , has a unique tire pressure detector identification code, or ID number. The code may be stored in transmitter  156 , processor  154 , or a memory (not shown) associated with the processor  154 . Association of the ID number with a particular tire location  112 ,  114  enables the monitor receiver  130  to know from which tire location  112 ,  114  the data is being received. 
       FIG. 3  shows a block diagram of an exemplary embodiment of a tire pressure monitoring system. Tire pressure detectors  202 ,  102 ,  122 , and  222  correspond to the left-front tire location  110 , the right-front tire location  112 , the right-rear tire location  114 , and the left-rear tire location  116 , respectively. Other configurations are possible for vehicles having different numbers of tires. For example, a spare tire for vehicle  100  may also have a tire pressure detector, or a tire pressure detector could be installed in each tire of a two-wheeled or 18-wheeled vehicle. Each tire pressure detector  202 ,  102 ,  122 , and  222  includes a tire pressure sensor  212 ,  222 ,  232 , and  242 , respectively; a processor  214 ,  224 ,  234 , and  244 , respectively; and a transmitter  216 ,  226 ,  236 , and  246 , respectively. Each tire pressure sensor  212 ,  222 ,  232 , and  242  senses the air pressure in its respective tire and provides data relating to the tire pressure to the respective processor  214 ,  224 ,  234 , and  244 . Each processor  214 ,  224 ,  234 , and  244  is configured to detect rapid changes in tire pressure and to control the respective transmitter  216 ,  226 ,  236 , and  246  to responsively transmit data and the unique identification code to receiver  250  in monitor receiver  130 . The data and the unique identification code are contents of a pressure change message transmitted to the monitor receiver  130 . In an alternate embodiment, the transmitter may transmit only the unique identification code as a pressure change message in response to a rapid change in tire pressure. Absent a rapid change in tire pressure, processors  214 ,  224 ,  234 , and  244  control respective transmitters  216 ,  226 ,  236 , and  246  to periodically transmit the unique identification code to receiver  250  in monitor receiver  130 . In a particular embodiment, each tire pressure detector  202 ,  102 ,  122 , and  222  also transmits a function code that differentiates between normal periodic transmissions and transmissions caused by tire pressure changes. The rate of pressure change created by releasing air from or pumping air into the tire  126  through the valve stem  158  is sufficiently rapid to initiate transmission of a pressure change message. 
     Monitor receiver  130  includes receiver  250 , processor  260 , and memory  270 . The receiver  250  receives data from each tire pressure transmitter  216 ,  226 ,  236 , and  246  over wireless links  208 ,  108 ,  128  and  228 , respectively. The processor  260  associates the unique identification codes of the tire pressure detectors  202 ,  102 ,  122 , and  222  with their respective tire locations, as will be discussed more fully below. Memory  270  stores the associations between the unique identification codes and the tire locations, enabling the processor  260  to immediately associate pressure data received from a particular transmitter  216 ,  226 ,  236 , or  246  with a tire location  110 ,  112 ,  114 , or  116 , respectively. The unique identification codes may be numbers or bit patterns or any other identifiers. For example, a unique pulse repetition frequency, a transmission frequency, or a unique modulation scheme may be used as a unique identification code. Monitor  130  further includes one or more I/O devices  280  coupled to said processor  260  for interaction with a user or other automotive subsystems. 
       FIG. 4  shows a flowchart of an exemplary method  300  of relearning associations between tires and tire locations which may be implemented in software in processor  260  as shown in  FIG. 2 . In some alternate embodiments, types of logic other than software, such as firmware or hardware, may be used. The process  300  begins in step  302  when the processor is commanded by a user through an input device  280  to enter a relearn mode. Any type of input device may be used, including existing input devices presently found in vehicle  100  ( FIG. 2 ). For example, turning the headlights or other accessories on and off several times in sequence may initiate relearning mode. 
     Once relearn mode has been entered at step  302 , processor  260  suspends tire pressure monitor (TPM) variables and diagnostics in step  304  to prevent normal operation of the monitor receiver  130  during relearn mode. Suspending the TPM variables and diagnostics prevents the inputs received during the relearn process from being interpreted as operational tire pressure information. The suspended variables and diagnostics are saved for reactivation in step  330  after relearn mode is complete. Optional step  306  provides feedback to the operator to the effect that relearn mode has been entered. For example, the processor  260  may control a horn of the automobile through an output device  280  to cause one or more horn chirps to signal the operator in step  306  that relearning mode has been entered. For a further example, the processor  260  may control a light, or telltale, on the instrument panel cluster or elsewhere of an automobile to begin flashing after relearning mode has been entered, and to remain flashing until relearning mode is complete. Step  308  sets a relearn timer so that the process  300  may later time out in case no inputs, as discussed below, are received. In step  310 , processor  260  determines if the relearn timer has expired. If the processor  260  determines that the relearn timer has expired, process  300  continues at step  330 , where the TPM variables and diagnostics are reactivated from suspension and step  332  exits from relearn mode and terminates the relearn process. 
     If processor  260  determines in step  310  that the relearn timer has not expired, step  316  determines if a pressure change message has been received. Step  316  will determine that a pressure change message has been received if steps  312  and  314 , which take place in a tire pressure detector  102 ,  122 ,  202 , or  222 , have been completed. Note that steps which take place in processor  260  are shown in the flowchart of  FIG. 4  as polygons made of solid lines, and steps to be taken in the tire pressure detector are shown as polygons made of broken lines. In step  312 , sensor  212 ,  222 ,  232 , or  242  senses a change in tire pressure induced by the operator. In one embodiment, the operator will sequentially cause a tire pressure change in each tire in a predetermined order. For example, the operator may cause tire pressure changes in the left front, right front, right rear, and left rear tire in that order by releasing air pressure through the valve. Other sequences may be alternatively be used. When a user-supplied increase or decrease in pressure is sensed in step  312 , the tire pressure transmitter  216 ,  226 ,  236 , or  246  transmits, in step  314 , a pressure change message to the receiver  250  in monitor  130 . 
     Step  312  occurs as a result of sequential interrogation of the tire pressure detectors  202 ,  102 ,  122 , and  222  by an operator increasing or reducing the tire pressure in each tire in a predetermined order. Changing the tire pressure excites the tire pressure detector to transmit at least the unique identification code and pressure change identifier. In a particular embodiment of the method, step  312  occurs once for each tire. If step  316  determines that no pressure change message has been received, step  336  decrements the relearn timer and loops back to step  310 . The loop  310 – 316 – 336 – 310  waits for steps  312  and  314  to take place. If the relearn timer expires while waiting for steps  312  and  314  to take place, steps  330  and  332  terminate relearn mode as previously described. 
     If the processor  260  determines in step  316  that a tire pressure change message has been received, process  300  resets the relearn timer in step  318 . If step  320  then determines that the tire pressure change message contains the first unique identification code received during the current relearn mode, step  334  erases from memory  270  the unique identification codes previously learned. In an exemplary embodiment, memory  270  has a register, or slot, in memory for each unique identification code, wherein each memory slot has a one-to-one correspondence with a tire location  110 ,  112 ,  114 , and  116 . The presence of a unique identification code in a particular memory slot creates the association between the unique identification code and the tire location  110 ,  112 ,  114 , or  116 . By erasing the unique identification codes from these memory slots in step  334 , the previous associations between unique identification codes and tire locations  110 ,  112 ,  114 , and  116  are also erased. After the previous unique identification codes are erased in step  334 , the first unique identification code is stored in a memory slot for the first predetermined tire location in step  324 . 
     If processor  260  determines in step  320  that the unique identification code received is not the first unique identification code received, the processor  260  determines in step  322  if the received unique identification code is unique compared to those already stored. For example, if an operator incorrectly changes the tire pressure in a particular tire twice, the second transmission of the unique identification code in the tire pressure change message will cause step  322  to determine that the received unique identification code is not unique as compared to those already stored. If the received unique identification code is not unique compared to those already stored, the relearn timer is decremented in step  336  and the loop  310 – 316 – 336 – 310  is reentered to wait for steps  312  and  314  to complete in the tire pressure detector  202 ,  102 ,  122 , or  222 . 
     If processor  260  determines in step  322  that the received unique identification code is unique compared to those already stored, the received unique identification code is stored in the next open memory slot in memory  270 . Step  326  then determines if the unique identification code just stored in step  324  was the last unique identification code expected. For example, step  326  may check to see if the last memory register has a unique identification code stored in it. If the last unique identification code has been stored, then step  328  provides feedback to the operator that the relearn mode is ending. For example, the processor  260  may control the horn to emit a double chirp and may turn off the flashing telltale on the instrument panel cluster or otherwise provide appropriate feedback to the user. Step  330  reactivates the TPM variables and diagnostics to put the TPM into normal operating mode and step  332  exits the relearn mode. For example, step  332  may deconstruct any software objects unique to relearn mode. 
     If processor  260  determines in step  326  that the last unique identification code has not been received, operator feedback is provided in step  306 . For example, a single horn chirp may be produced as previously described to indicate to the operator that another unique identification code is expected. The relearn timer is reset for the next unique identification code in step  308  and the wait loop  310 – 316 – 336  is reentered to wait for the next user-supplied pressure change in steps  312  and  314 . 
     The described exemplary embodiment of a tire pressure monitoring system reduces the amount of hardware and software needed compared to systems with hardware in each wheel well to communicate with the tire in that wheel well. Further, a monitor receiver  130  may be used with the tire pressure transmitters  102 ,  122  of various manufacturers. Some existing monitor receivers used with other systems may be reprogrammed to become monitor receivers  130 . 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.