Abstract:
An apparatus and method is provided for detecting when a spare wheel has been placed onto a rolling wheel location and for taking appropriate action such as providing a driver alert, limiting vehicle speed or alerting the driver when vehicle speed exceeds the maximum safe speed for operation with a spare wheel. The spare wheel transmits a signal with a protocol compatible marker. The vehicle receives the protocol compatible marker. The marker is compared to a predetermined value to determine that the protocol compatible marker signal is indicative of a spare wheel.

Description:
TECHNICAL FIELD 
     The present invention relates to the field of monitoring the condition of tires and wheels on motor vehicles and more particularly to detecting when a spare wheel is in use as a rolling wheel of a vehicle. 
     BACKGROUND 
     Wheels for motor vehicles are equipped with transmitters that broadcast information about the status of the wheels, including the tire identity and location, whether the wheel is rolling or stationary, temperature and tire pressure. Vehicles on which such wheels are mounted include tire monitoring systems that receive and process the information transmitted by the wheels. Information is exchanged between wheels and vehicles by means of wireless transmissions in accordance with communication protocols. 
     It has been proposed to use tire monitoring systems to detect when a spare wheel has been mounted as an active or rolling wheel. See, for example, U.S. Pat. No. 7,030,745. Such systems rely on the use of a unique wheel identification number. When a spare wheel is removed from a storage location and installed as a rolling wheel (such as to fix a flat tire), the system detects rolling movement in the spare wheel (which is uniquely identified by its ID number). Thus it is determined that the spare wheel has been placed onto a rolling wheel location. 
     A drawback to these proposed systems is that they rely on an association of a unique ID number with a specific wheel and wheel position. This association of unique ID numbers with wheel positions takes place during a learning mode, which may require manual intervention or additional electronics. 
     SUMMARY 
     It would be desirable to detect the use of a spare wheel on a rolling wheel without requiring that spare wheel have a unique ID number that is known in advance by the tire monitoring system. 
     In accordance with one aspect of the invention, a method is provided for determining when a spare wheel equipped with a transmitter is in use on a rolling wheel location of a vehicle. The method includes transmitting from the spare wheel a protocol compatible marker signal; receiving on the vehicle the protocol compatible marker signal; and comparing the protocol compatible marker signal to a predetermined data to determine that the protocol compatible marker signal is indicative of a spare wheel. The predetermined data is not previously associated with the spare wheel. 
     In accordance with another aspect of the invention, an apparatus is provided for determining when a spare wheel equipped with a transmitter is in use on a vehicle having a plurality of rolling wheel locations. The apparatus includes a receiver mounted to vehicle and adapted to receive a signal from the transmitter on the spare wheel; a memory storing at least one predetermined protocol compatible marker value indicative of a spare wheel; and a controller coupled to the receiver and the memory. The controller is programmed to generate a spare-tire-in-use-signal if the signal received from the transmitter corresponds to the predetermined protocol compatible marker value stored in memory. The value stored in memory is not previously associated with the spare wheel. 
     In accordance with yet another aspect of the invention, an apparatus is provided for determining when a spare wheel equipped with a transmitter is in use on a rolling wheel location of a vehicle. The apparatus includes a spare wheel having a first memory that contains a protocol compatible marker, and a transmitter that transmits the protocol compatible marker stored in the first memory. The apparatus also includes a receiver mounted to vehicle and adapted to receive the protocol compatible marker transmitted from the spare wheel; a second memory storing at least one predetermined value not previously associated with the spare wheel; and a controller coupled to the receiver and the memory and configured to generate a spare-tire-in-use-signal if the protocol compatible marker transmitted from the spare wheel corresponds to the predetermined data stored in the second memory. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  is a block diagram of a system for remotely operating a vehicle in accordance with a first embodiment of the invention; 
         FIG. 2  is a block diagram of the spare wheel shown in  FIG. 1 ; 
         FIG. 3  is a flow chart illustrating the operation of the spare wheel shown in  FIG. 1 . 
         FIG. 4  is a flow chart illustrating the operation of the vehicle shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to  FIG. 1 , a tire monitoring system  10  is illustrated to detect the use of a spare wheel  12  on one of rolling wheel locations  14   a - 14   d  of a vehicle  16 . Normally spare wheel  12  is stowed on vehicle  16  in a suitable location, such as the vehicle&#39;s trunk (not shown). However, should one of the regular wheels (such as wheels  17   b - 17   d ) on rolling wheel locations  14   a - 14   d  become disabled (e.g., a flat tire), then the operator of vehicle  16  can replace the disabled wheel at one of rolling wheel locations  14   a - 14   d  with spare wheel  12 . It would be useful to detect the use of spare wheel  12  on one of rolling wheel locations  14   a - 14   d.    
     As explained below, system  10  allows detection of the use of spare wheel  12  as rolling wheel without requiring that spare wheel have a unique ID number that is known in advance by system  10 . 
     Referring to  FIGS. 1 and 2 , system  10  includes components on both spare wheel  12  and vehicle  16 . Spare wheel  12  includes a wheel portion  18  and a tire  20 . As shown schematically in  FIG. 2 , mounted to wheel portion  18  are a motion sensor  22 , a transmitter  24 , a memory  26 , a controller  28  coupled to memory  26 , motion sensor  22  and transmitter  24 , and a battery  30  to provide power to the electronic components. Transmitter  24  can be a transceiver if two-way communication is desired between spare wheel  12  and vehicle  16 . Controller  28  can be a programmed microcontroller or an application-specific integrated circuit (ASIC) and can be integrated with memory  26  one or more of the other components of system  10 . Spare wheel  12  is also equipped with a pressure sensor  32  operatively coupled to the interior of tire  20 , and a transponder activation coil  34 . 
     Controller  28  receives input from motion sensor  22  and pressure sensor  32  and formats this input for wireless transmission by transmitter  24  to vehicle  16  as a signal in accordance with a predetermined communications protocol. Communication by controller  28  can be at predetermined intervals or can be initiated in response to stimulation of transponder activation coil  34  by a signal emanating from vehicle  16 . As explained below, controller  28  also formats a protocol compatible marker signal for transmission by transmitter  24 . 
     Referring to  FIG. 1 , vehicle  16  includes receivers  36   a - 36   d  mounted thereon. Receivers  36   a - 36   d  are adapted to receive signals transmitted by transmitter  24 . Receivers  36   a - 36   d  can be transceivers if two-way communication is desired between spare wheel  12  and vehicle  16 . Alternatively, a single receiver such as receiver  36   a,  for example, can be used to cover all rolling wheel locations  14   a - 14   d.  Vehicle  16  also includes a memory  38  and a controller  40 . Using memory  38 , controller  40  processes information contained in the signals received by receiver  36   a,  for example, to determine if spare wheel  12  is in use at one of rolling location  14   a,  for example. Vehicle can be equipped with one receiver such as receiver  36   a  or it can have multiple receivers or antennae located near each rolling wheel position, such receivers  36   b - 36   d.  Receiver  36  and controller  40  can be part of an existing tire pressure management system (“TPMS”) programmed in accordance with the disclosed embodiments to recognize use of spare wheel  12  in one of moving wheel locations  14   a - 14   d.    
     Controller  40  is also coupled to an indicator  41  located on or near the vehicle dashboard (not shown). When controller  40  determines that spare wheel  12  is in use at a one of rolling wheel locations, it generates a spare-wheel-in-use signal that causes indicator  41  to provide visual indication to the operator of vehicle  16 . Alternatively, indicator  41  can provide audio or tactile indications to the operator. 
     System  10  can also take appropriate safety actions when spare wheel  12  is in use at one of rolling locations  14   a - 14   d . For example, system  10  can provide, as discussed previously, a driver alert such as indicator  41 . System  10  can also limit the speed of vehicle  16  when it exceeds the maximum safe speed for operation with spare wheel  12 . Alternatively, system  10  can alert the driver when the speed of vehicle  16  exceeds the maximum safe speed for operation with spare wheel  12 . 
     The operation of spare wheel  12  and vehicle  16  is illustrated by the flow charts of  FIG. 3  and  FIG. 4 , respectively. Referring to  FIG. 3 , beginning at block  42 , controller  28  reads motion sensor  22  to acquire data indicating whether spare wheel  12  is in motion. At block  44 , controller  28  reads memory  26  to acquire data used to generate a signal that includes a marker indicative of a spare wheel. At block  46 , processor formats a signal or sequence of signals for transmission using the data acquired from motion sensor  22  and memory  26  to include a protocol compatible or generic marker indicative of a spare tire. At block  48 , controller  28  transmits the formatted signal to vehicle  16  via transmitter  24 . 
     Signals or messages transmitted by wheel  12  to vehicle  16  are formatted in accordance with a predetermined communications protocol. The protocol can be a recognized standard or a proprietary or application specific protocol. Under such protocols, signals generated by wheel  12  will have a predetermined syntax, format and/or structure and will include predetermined types of content. The applicable protocol can also specify the sequence with which certain types of signals are sent. For example, the protocol could include signals with the following format:
 
[Function code {3 Bits}] [ID {24 Bits}] [Press Data {8 Bits}] [Check Sum {2 Bits}]
 
     A signal can be created to include a marker that is generically indicative of a spare wheel but that is not uniquely associated with a specific wheel such as wheel  12 . This signal can be formatted in a manner that can deviate from but is still compatible with the applicable protocol or other protocol used to send and receive messages between wheel  12  and vehicle  16 . In stating that the signal is compatible with a protocol, it is meant that the signal can be processed by equipment programmed to communicate in accordance with the protocol. By maintaining compatibility with the applicable protocol, for example, the marker signal can be used without having to reprogram or replace existing TPMS hardware. Within a protocol-compatible signal, a marker indicative of a spare wheel may take many forms. For example, function codes can be drawn from a predetermined list and tire ID numbers can be drawn from a predetermined range. The protocol compatible marker indicative of a spare wheel can be use of a special function code (e.g. “000”) that is not already assigned under the applicable protocol. Alternatively, the marker can be a tire ID number outside of the predetermined range (e.g. “999999”). Alternatively, the marker can be the transmission of signals in a predetermined sequence not otherwise used under the protocol. Alternatively, the marker could use a value for pressure outside of the recognized ranges. 
     The marker can be transmitted using the data structure normally used or using a data structure that included an additional field to indicate whether the wheel was a spare wheel or a regular wheel, such as:
 
[Position Code {&gt;=1 Bit}] +“[Function code {3 Bits}] [ID {24 Bits}] [Press Data {8 Bits}][Check Sum {2 Bits}]”
 
     In the foregoing example, the gods for wheels could be selected as shown in Table 1 below: 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 One bit coding 
                 Two bit coding 
               
               
                   
                   
               
             
             
               
                   
                 0 = Road tire 
                 00 = Road 1 
               
               
                   
                 1 = spare tire 
                 01 = Road 2 
               
               
                   
                   
                 10 = Spare Full Service 
               
               
                   
                   
                 11 = Spare Temp Service 
               
               
                   
                   
               
             
          
         
       
     
     Note that by using a two bit coding scheme, information pertaining to a spare wheel can indicate whether it is a full service or temporary spare. 
     Referring to  FIG. 4 , the operation of vehicle  16  is illustrated. At block  50 , controller  40  checks receivers  36   a - 36   d  for a signal from wheels associated with vehicle, such as spare wheel  12  or wheels  17   b -  17   d.  This can be implemented by having controller  40  wait for a signal to be received by receiver  36   a - d.  Alternatively, controller can periodically transmit a request to wheels such as spare wheel  12  or wheels  17   b - 17   d  as explained above. Such a request causes transponder coil  34  to activate transmission of data by wheel  12 , for example. When a signal is received, controller  40  determines at block  52  whether the signal contains a protocol-compatible marker indicative of a spare wheel such as spare wheel  12 . Controller  40  can accomplish this step by comparing the contents of the signal received with information in memory  38 . 
     The implementation of this step depends on the type of marker used to indicate a spare wheel. For example, if the marker is a special function code (e.g. “000”) stored in memory  38 , then controller  40  would compare the function code in the signal received by receivers  36   a - 36   d  to the special function code stored in memory  38  to determine if the function code in the signal corresponded to the special function code in memory  38 . Alternatively, if the marker is a specific sequence of function codes stored in memory  38 , then controller  40  would record in memory  38  the sequence of functions in the signals received by receiver  36   a - d.  Controller  40  would then compare the sequence of function codes in the signals to the specific sequence of function codes stored in memory  38  to determine if the sequence of function codes in the signals received by receivers  36   a - 36   d  corresponded to the marker. Alternatively, if the marker is a predetermined tire ID number (e.g. “999999”) stored in memory  38 , then controller  40  would compare the function code in the signal received by receivers  36   a - 36   d  to the predetermined tire ID number stored in memory  38  to determine if the tire ID number in the signal corresponds to the predetermined tire ID code in memory. 
     It should be noted that to detect the presence of spare wheel  12  in accordance with the disclosed embodiment, vehicle  16  need not store in memory  38  data specific to spare wheel  12  (such as a unique tire ID number corresponding to spare wheel  12 ). Rather, vehicle  16  need only store data about a marker that generically indicates a spare wheel such as spare wheel  12 . Thus, any spare wheel installed in one of running wheel locations  14   a - 14   d  can be identified as a spare wheel, even if no information about that particular spare wheel is recorded in vehicle  16 . 
     If at decision block  52 , controller  40  determines that a marker is present in the signal received by receivers  36   a - d,  then it is judged that the sender of the signal is a spare wheel such as spare wheel  12 . Control then moves to block  54 , where controller  40  checks the signal to determine if it contains data indicating that the wheel sending the signal is in motion. To avoid false positives (that is false indications of a spare wheel in use), controller  54  can postpone determination that spare wheel  12  is in motion until signals indicating motion have been received for a minimum period of time and/or controller  16  determines that vehicle  16  is also moving. 
     At decision block  56 , if controller  40  determines that spare wheel  12  is in motion, then it is judged that spare wheel  12  is in use on one of moving wheel locations  14   a - 14   d.  In that case, control moves to block  58  where controller  40  generates a spare-wheel-in-use signal. Control then moves to block  60 , where indicator  42  is activated in response to the spare-wheel-in-use signal. 
     At decision block  56 , if controller  40  determines that spare wheel  12  is not in motion, then it is judged that spare wheel  12  is not in use and control moves block  62  where controller continues with its normal TPMS processing, and then returns to block  50  to continue monitoring for incoming signals from wheels such as spare wheel  12  and wheels  17   b - 17   d.    
     The above-described embodiments have been described in order to allow easy understanding of the present invention, and do not limit the present invention. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.