Abstract:
A method of providing improved control and response to an electronic transmission range selection system comprehends providing a virtual null position for the electronic transmission range selection device including the steps of determining the current position of the shift lever, confirming the position of the shift lever, virtual Null and physical Reverse to Neutral confirmation timer thresholds are selected, the timers are incremented, a determination is made that the timers have started, a determination is made that the virtual Null timer has expired, whereupon a virtual Null request is generated. Subsequent steps determine if the physical Neutral timer has expired and command the transmission to Neutral. In related method steps, a current range of the transmission is determined, the state of a shift interlock button is determined, and certain shift changes are accepted or rejected.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/300,490, filed Feb. 26, 2016, which is hereby incorporated in its entirety herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to methods of controlling automatic transmissions with electronic shift levers and more particularly to a method of controlling an automatic transmission with an electronic shift lever having a virtual null position. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0004]    As the internal control systems of passenger cars and light trucks increasingly move from full mechanical systems such as throttle connections and gear selection to full electronic systems in which such mechanical connections are replaced by electrical sensors, microprocessors and servo devices, a constant goal is to provide not only the same performance, response and operator feel but also improved performance, reliability and safety. 
         [0005]    One of the current features of such ongoing development is the electronic transmission range select (ETRS). In this device, a transmission shift lever having an orthogonal range of motion such as longitudinal, i.e., front to rear with one or more lateral, i.e., side to side, paths, essentially mimics a conventional shift lever which is linked mechanically to the transmission. However, in its modern configuration, the mechanical linkage is eliminated and replaced with, for example, position sensors at the shift lever, a transmission control module (TCM) and one or more solenoids or servo devices that effect range and/or gear selection of the transmission. For example, the shift lever may comprehend four physical positions: R (reverse), N (neutral), Null and D (drive) and it is spring biased to return to the Null position. In order for the operator to select certain active gear ranges, an interlock button, typically located on the side of the shift lever, must first be depressed and the shift lever must remain in the newly selected position for a certain minimum time in order for the system to validate and act upon a shift request. 
         [0006]    As stated above, the goal of this and other electronic systems is to safely provide improved operator feel, response and performance. This goal may represent a significant challenge as safety considerations such as requiring a delay between gear selections and the activation of the interlock button may interfere with acting upon rapid operator inputs. 
         [0007]    The present invention is directed to improving the driving experience with transmissions equipped with electronic transmission range select systems and ensuring that all operator commands are acted upon. 
       SUMMARY 
       [0008]    The present invention provides improved operator control and transmission response to operator commands entered by an electronic transmission range shifter. The method of providing such improved control and response comprehends providing a virtual null position for the electronic transmission range selection device including the steps of determining the current position of the shift lever, confirming the position of the shift lever, virtual Null and physical Reverse to Neutral confirmation timer thresholds are selected, the timers are incremented, a determination is made that the timers have started, a determination is made that the virtual Null timer has expired, whereupon a virtual Null pulse is generated. Subsequent steps determine if the physical Neutral timer has expired and command the transmission to Neutral. In related method steps, a current range of the transmission is determined, the state of a shift interlock button is determined, and certain shift changes are accepted or rejected. 
         [0009]    It is thus an aspect of the present invention to provide a method of controlling an automatic transmission with an electronic transmission range lever shifter having a virtual null position. 
         [0010]    It is a further aspect of the present invention to provide a method of controlling an automatic transmission with an electronic transmission range lever shifter which accurately responds to operator requested shifts. 
         [0011]    It is a still further aspect of the present invention to provide a method of controlling an automatic transmission with an electronic transmission range lever shifter which determines and confirms the present position of the shift lever. 
         [0012]    It is a still further aspect of the present invention to provide a method of controlling an automatic transmission with an electronic transmission range lever shifter which establishes virtual Null and physical Reverse to Neutral timer thresholds. 
         [0013]    It is a still further aspect of the present invention to provide a method of controlling an automatic transmission with an electronic transmission range lever shifter which establishes virtual Null and physical Reverse to Neutral timer thresholds and increments such timers. 
         [0014]    It is a still further aspect of the present invention to provide a method of controlling an automatic transmission with an electronic transmission range lever shifter which establishes virtual Null and physical Reverse to Neutral timer thresholds and determines when such timers have expired. 
         [0015]    It is a still further aspect of the present invention to provide a method of controlling an automatic transmission with an electronic transmission range lever shifter which determines a position of a shift interlock button. 
         [0016]    Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0017]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0018]      FIG. 1  is a schematic view of an electronic transmission range selector, control module and transmission incorporating the present invention; 
           [0019]      FIGS. 2A and 2B  are time line graphs illustrating the sequence of operation during shift commands of an electronic transmission range selector of the prior art and with the present invention, respectively; 
           [0020]      FIG. 3  is a flow chart of the method of the present invention illustrating the generation of a virtual null signal when moving an electronic transmission range lever shifter from Reverse range to Neutral; 
           [0021]      FIG. 4  is a flow chart of the method of the present invention illustrating a shift request for Neutral or Reverse range while in Drive range; 
           [0022]      FIG. 5  is a flow chart of the method of the present invention illustrating a shift request for Reverse or Drive range while in Neutral; and 
           [0023]      FIG. 6  is a flow chart of the method of the present invention illustrating a shift request for Drive or Neutral while in Reverse range. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0025]    With reference to  FIG. 1 , an electronic transmission range selection system associated with the present method is illustrated and generally designated by the reference number  10 . The electronic transmission range selection system  10  includes a shift lever  12  disposed in and constrained to translate along an inverted “L” shaped track  14 . The shift lever  12  is illustrated in a Null position  16  and has a “D” or Drive selecting position  18  to the rear (or down) and an “N” or Neutral selecting position  22  to the front (or up). To the left of the Neutral selecting position  22  is an “R” or Reverse selecting position  24 . The shift lever  12  includes an interlock button or switch  26 . The shift lever  12  further includes a “P” or Park button or switch  28 . Both the interlock button or switch  26  and the Park button or switch  28  are two position, momentary contact devices that may be depressed or activated by the vehicle operator. 
         [0026]    The shift lever  12  is biased into the Null position  16  by a plurality of springs  30 , typically compression springs. A plurality of sensors  32  provide data or signals regarding the current position of the shift lever  12  (Null, N, D and R) to a transmission control module  34 . The states of the interlock button or switch  26  and the Park button or switch  28 , i.e., depressed or released, are also provided to the transmission ETRS control module (TRSCM)  34  which, in turn, provides outputs or control signals commanding the currently selected gear state to actuators, operators or servos (not illustrated) in an automatic transmission  40 . The automatic transmission  40  is driven by a prime mover  42  such as an internal combustion, gasoline, Diesel or flex-fuel engine or hybrid power plant. The automatic transmission  40  includes an output or prop shaft  44  which is coupled to and drives a final drive assembly (not illustrated). 
         [0027]    Referring now to  FIGS. 1 and 2A and 2B , two time line graphs having four lines or tracks illustrate the sequence of operation during a shift command to an electronic transmission range select system.  FIG. 2A  illustrates a sequence of shift commands to a prior art system which misses or ignores a request to shift into reverse.  FIG. 2B  illustrates the same sequence of shift commands provided to the system  10  according to the present invention which accurately interprets same and commands a shift into Reverse. The four tracks or lines  52 A,  54 A,  56 A and  58 A represent the positions of the interlock switch  26  and the shift lever  12  in a prior art control system as well as the range request from the transmission control module to the automatic transmission and the actual state (gear or range) of the automatic transmission, respectively. The four tracks or lines  52 B,  54 B,  56 B and  58 B represent the positions of the interlock switch  26  and the shift lever  12  in an electronic transmission range selection system  10  according to the present invention, the range request from the transmission control module  34  to the automatic transmission  40  and the actual state (gear or range) of the automatic transmission  40 , respectively. 
         [0028]    As illustrated the track or line  54 A of  FIG. 2A , the vehicle operator initially has moved the shift lever  12  from the Null position  16 , to the Reverse selecting position  24 , to the Neutral selecting positon  22  for less than a selection separation interval, then back to the Reverse selecting position  24 . Finally, the vehicle operator releases the shift lever  12  and it returns to the Null position  16 . As shown in the line or track  52 A, when the shift lever  12  is in the Reverse selecting position  24 , the vehicle operator depresses the interlock switch or button  26  and does not release it until the shift lever  12  is moved to the Reverse selecting position  24  for the second time. The line or track  56 A presents the range request provided by a transmission control module to an automatic transmission. It will be appreciated that the request for Reverse gear is ignored because although the interlock switch or button  26  was depressed, the one second selection separation interval overrode the Reverse request since the shift lever  12  was in the Neutral position  22  for less than the selection separation interval. As the line or track  58 A illustrates, the transmission thus shifts from Drive to Neutral and remains there, ignoring the operator shift request for Reverse range. 
         [0029]    As illustrated in track or line  54 B of  FIG. 2B , again the vehicle operator has moved the shift lever  12  from the Null position  16 , to the Reverse selecting position  24 , to the Neutral selecting positon  22  for less than a selection separation interval of one second as imposed by the transmission control module  34 , then back to the Reverse selecting position  24 . Finally, the vehicle operator releases the shift lever  12  and it returns to the Null position  16 . As shown in the line or track  52 B, when the shift lever  12  is in the Reverse selecting position  24  for the first time, the vehicle operator depresses the interlock switch or button  26  and does not release it until the shift lever  12  is moved to the Reverse selecting position  24  for the second time. The line or track  56 B presents the range request provided by the transmission control module  34  to the automatic transmission  40 . As illustrated, the first request for Reverse gear is ignored because the interlock switch  26  was not depressed. However, the virtual Null provided by the present invention satisfies the selection separation interval, typically about one second, and residence of the shift lever  12  in the Neutral position  22 . Thus sufficient null or Neutral time has been provided such that that the transmission control module  34  accepts the second request from the Reverse selecting position  24  and commands Reverse gear. As the line or track  58 B illustrates, the transmission  40  first shifts from Drive range to Neutral and thence to Reverse range, fully complying with the shift request of the vehicle operator. 
         [0030]    Referring now to  FIG. 3 , a flowchart illustrating the steps of the present method provides an algorithm for insertion of a virtual Null position between the physical Reverse position of the shift lever  12  and the physical Neutral position of the shift lever  12 , which may be embodied and performed in electronic memory and software residing within a microprocessor in the transmission control module  34 , is illustrated and generally designated by the reference number  100 . The method  100  begins with a conventional start or initializing step  102  which, for example, resets and clears registers and reads the current values of the switches  26  and  28  and the sensors  32 . The method  100  then moves to a first decision point  104  which confirms that the position of the shift lever  12  is in the Reverse selecting position  24 . By use of the word “confirmed,” it is meant that, given a typical algorithm or program looping or iteration time of, for example, 100 milliseconds for the method  100 , several loops or iterations have been completed such that the reliability of this decision is high. If it is not confirmed, the first decision point  104  is exited at NO. If the position of the shift lever  12  is confirmed as in the Reverse selecting position  24 , the first decision point  104  is exited at YES and the method  100  moves to a second decision point  106  that inquires whether the sampled, i.e., current, position of the shift lever  12  is in the Neutral position  22 . If it is not, the second decision point  106  is exited at NO. If either the first decision point  104  or the second decision point  106  is exited at NO, the method  100  moves to a first process step  108  which stops and resets both the virtual Null and the physical Neutral confirmation timers, which will be described in more detail subsequently, and the method  100  terminates in a stop or end instruction  110 . 
         [0031]    If the second decision point  106  determines that the sampled position of the shift lever  12  is in the Neutral position  22 , the second decision point  106  is exited at YES and the method  100  moves to a third decision point  114  which inquires or determines whether the virtual Null and the physical Neutral confirmation timers have started. If they have not, the third decision point  114  is exited at NO and the method  100  moves to a second process step  116  which selects and sets the virtual Null and physical Reverse gear to Neutral confirmation timer thresholds. It should be understood that an assumption is here made that the virtual Null timer threshold is less than the physical Reverse range to Neutral confirmation timer threshold. After setting these timer thresholds in the second process step  116 , a third process step  118  starts the virtual Null and the physical Neutral confirmation timers. Upon completion of the third process step  118 , the method  100  moves to the stop instruction or end point  110 . 
         [0032]    If it is determined that the virtual Null and the physical Neutral confirmation timers have started, the decision point  114  is exited at YES and the method  100  moves to a fourth decision point  122  which determines whether the virtual Null confirmation timer started in the third process step  118  has expired, i.e., has timed out. If it has not, the fourth decision point  122  is exited at NO and the method  100  moves to a fourth process step  124  which increments the virtual Null and the physical Neutral confirmation timers with every loop execution. The method  100  then terminates in the stop instruction or end point  110 . 
         [0033]    If it is determined that the virtual Null confirmation timer started in the third process step  118  has expired, the fourth decision point  122  is exited at YES and the method  100  moves to a fifth process step  126  which sets the confirmed position of the shift lever  12  as the Null position and inserts or generates the rising edge of a virtual Null pulse or signal. This signal or pulse is utilized in and by the additional methods and algorithms set forth in  FIGS. 4, 5 , and  6  and the accompanying text. The method  100  then moves to a fifth decision point  130  which determines whether the physical Neutral confirmation timer has expired, i.e., timed out. If it has not, the fifth decision point  130  is exited at NO and a sixth process step  132  is encountered. The sixth process step  132  also increments the Neutral confirmation timer with every execution loop and the method  100  then terminates at the stop instruction or termination point  110 . If, at the fifth decision point  130 , it is determined that the physical Neutral confirmation timer has expired, the fifth decision point  130  is exited at YES and a seventh process step  134  is encountered which commands a Neutral request to the transmission  40 . The method  100  then terminates at the stop instruction or step  110 . 
         [0034]    Referring now to  FIG. 4 , an associated portion of the method  100  illustrates how the virtual Null pulse or signal generated in  FIG. 3  is utilized by the electronic transmission range selection system  10  to process an operator Reverse or Neutral shift request when the transmission  40  is in the Drive range and is generally designated by the reference number  150 . Once again, the method  150  begins with an initializing or start step  152  and moves to a first decision point  154  which confirms that the shift lever  12  is in the Null position. Again, the word “confirms” is utilized here as described above. If the Null position of the shift lever  12  is confirmed, the first decision point  154  is exited at YES and the method  150  moves to a first process step  156  which resets any previously confirmed and set position of the shift lever  12  to Null. An associated second process step  158  then reports the new state of the shift lever  12  as the Null position. This portion of the method  150  then terminates at an end or termination step  160 . 
         [0035]    Returning to the first decision point  154 , if it is not confirmed that the shift lever  12  is in the Null position, the first decision point  154  is exited at NO and the method  150  enters a second decision point  162  which determines whether the current confirmed position of the shift lever  12  is the same as the previously confirmed position of the shift lever  12 . If it is, the second decision point  162  is exited at YES and the method  150  moves to a third process step  164  which commands the transmission  40  to operate in the Drive range. If the current confirmed position of the shift lever  12  is not the same as the previously confirmed position of the shift lever  12 , the second decision point  162  is exited at NO and the method  150  moves to a third decision point  166  which inquires whether the confirmed position of the shift lever is Reverse range. If it is not, the third decision point  166  is exited at NO and a fourth decision point  168  is encountered which inquires whether the confirmed position of the shift lever  12  is Neutral. If it is not, the method  150  exits the fourth decision point  168  at NO and returns to the third process step  164  which commands the transmission  40  to operate in the Drive range. If the fourth decision point  168  determines that the confirmed position of the shift lever  12  is Neutral, it is exited at YES and the method  150  moves to a fourth process step  172  which commands the transmission  40  to Neutral. From the fourth process step  172 , the method  150  moves to a fifth process step  174  which resets the previously confirmed position of the shift lever  12  to Neutral. The method  150  then terminates at the end point or termination step  160 . 
         [0036]    Returning to the third decision point  166 , if the current confirmed position of the shift lever  12  is Reverse range, the third decision point  166  is exited at YES and the method  150  moves to a fifth decision point  176  which determines whether the interlock switch or button  26  is depressed. If it is not, the method  150  moves to a sixth process step  178  which rejects the operator&#39;s Reverse range request and, optionally, sends a signal to a Driver Information Center (DIC)  180 , illustrated in  FIG. 1 , which provides, for example, a visual indication that the operator must first depress the interlock button ( 26 ) before moving the shift lever ( 12 ) or that the request for Reverse range will not be acted upon unless this is done. From the sixth process step  178 , the method  150  moves to a seventh process step  182  which commands the transmission  40  to Neutral. The method  150  then returns to the fifth process step  174  which resets the previously confirmed position of the shift lever  12  to Neutral. 
         [0037]    Returning to the fifth decision point  176 , if the interlock button or switch  26  is depressed, the fifth decision point  176  is exited at YES and the method  150  then encounters an eighth process step  184  which commands the transmission  40  into the Reverse range as requested by the vehicle operator. A final, ninth process step  186  resets the previously confirmed position of the shift lever  12  to Reverse range. The method  150  then terminates at the end point or termination step  160 . 
         [0038]    Referring now to  FIG. 5 , an associated portion of the method  100  illustrates how the virtual null pulse or signal generated in  FIG. 3  is utilized by the electronic transmission range selection system  10  to process an operator shift request for Reverse range or Drive range while the transmission  40  is in Neutral and is generally designated by the reference number  200 . Once again, the method  200  begins with an initializing or start step  202  and moves to a first decision point  204  which confirms that the shift lever  12  is in the Null position. Again, the word “confirms” is utilized here as described above. If the Null position of the shift lever  12  is confirmed, the first decision point  204  is exited at YES and the method  200  moves to a first process step  206  which resets any previously confirmed and set position of the shift lever  12  to Null. An associated second process step  208  then reports the new position of the shift lever  12  as the Null position. This portion of the method  200  then terminates at an end or termination step  210 . 
         [0039]    Returning to the first decision point  204 , if it is not confirmed that the shift lever  12  is in the Null position, the first decision point  204  is exited at NO and the method  200  enters a second decision point  212  which determines whether the current confirmed position of the shift lever  12  is the same as the previously confirmed position of the shift lever  12 . If it is, the second decision point  212  is exited at YES and the method moves to a third process step  214  which commands the transmission  40  to Neutral. If the current confirmed position of the shift lever  12  is not the same as the previously confirmed position of the shift lever  12 , the second decision point  212  is exited at NO and the method  200  moves to a third decision point  216  which inquires whether the confirmed position of the shift lever is Reverse range. If it is not, the third decision point  216  is exited at NO and a fourth decision point  218  is encountered which inquires whether the confirmed position of the shift lever  12  is the Drive range. If it is not, the method  200  exits the fourth decision point  218  at NO and returns to the third process step  214  which commands the transmission  40  to Neutral. If the fourth decision point  218  determines that the confirmed position of the shift lever  12  is the Drive range, it is exited at YES and the method  200  moves to a fourth process step  222  which commands the transmission  40  to the Drive range. From the fourth process step  222 , the method  200  moves to a fifth process step  214  which resets the previously confirmed position of the shift lever  12  to the Drive range. The method  200  then terminates at the end point or termination step  210 . 
         [0040]    Returning to the third decision point  216 , if the current confirmed position of the shift lever  12  is Reverse range, the third decision point  216  is exited at YES and the method  200  moves to a fifth decision point  226  which determines whether the interlock switch or button  26  is depressed. If it is not, the method  200  exits the fifth decision point  226  at NO and moves to a sixth process step  228  which rejects the operator&#39;s Reverse range request and, optionally, sends a signal to the Driver Information Center (DIC)  180  indicating, for example, that the operator must first depress the interlock button ( 26 ) before moving the shift lever ( 12 ) or that the request for Reverse range will not be acted upon. From the sixth process step  228 , the method  200  moves to a seventh process step  232  which commands the transmission  40  to Neutral. The method  200  then enters an eighth process step  234  which resets the previously confirmed position of the shift lever  12  to Neutral. The method  200  terminates at the end point  210 . 
         [0041]    Returning to the fifth decision point  226 , if the interlock button or switch  26  is depressed, the fifth decision point  226  is exited at YES and the method  200  then encounters a ninth process step  236  which commands the transmission  40  into the Reverse range as requested by the vehicle operator. A final, tenth process step  238  resets the previously confirmed position of the shift lever  12  to Reverse range. The method  200  then terminates at the end point or termination step  210 . 
         [0042]    Referring now to  FIG. 6 , an associated portion of the method  100  illustrates how the virtual null pulse or signal generated in  FIG. 3  is utilized by the electronic transmission range selection system  10  to process an operator shift request for Drive range or Neutral while the transmission  40  is in the Reverse range and is generally designated by the number  250 . Once again, the method  250  begins with an initializing or start step  252  and moves to a first decision point  254  which confirms that the shift lever  12  is in the Null position. Again, the word “confirms” is utilized here as described and utilized above. If the Null position of the shift lever  12  is confirmed, the first decision point  254  is exited at YES and the method  250  moves to a first process step  256  which resets any previously confirmed and set position of the shift lever  12  to Null. An associated second process step  258  then reports the new state or position of the shift lever  12  as the Null position. This portion of the method  250  then terminates at an end or termination step  260 . 
         [0043]    Returning to the first decision point  254 , if it is not confirmed that the shift lever  12  is in the Null position, the first decision point  254  is exited at NO and the method  250  enters a second decision point  262  which determines whether the current confirmed position of the shift lever  12  is the same as the previously confirmed position of the shift lever  12 . If it is, the second decision point  262  is exited at YES and the method  250  moves to a third process step  264  which commands the transmission  40  to the operator requested Reverse range. If the current confirmed position of the shift lever  12  is not the same as the previously confirmed position of the shift lever  12 , the second decision point  262  is exited at NO and the method  250  moves to a third decision point  266  which inquires whether the confirmed position of the shift lever  12  is the Drive range. If it is not, the third decision point  266  is exited at NO and a fourth decision point  268  is encountered which inquires whether the confirmed position of the shift lever  12  is Neutral. If it is not, the method  250  exits the fourth decision point  268  at NO and returns to the third process step  264  which commands the transmission  40  to the operator requested Reverse range. If the fourth decision point  268  determines that the confirmed position of the shift lever  12  is Neutral, it is exited at YES and the method  250  moves to a fourth process step  272  which commands the transmission  40  to Neutral. From the fourth process step  272 , the method  250  moves to a fifth process step  274  which resets the previously confirmed position of the shift lever  12  to Neutral. The method  250  then terminates at the end point or termination step  260 . 
         [0044]    Returning to the third decision point  266 , if the current confirmed position of the shift lever  12  is the Drive range, the third decision point  266  is exited at YES and the method  250  moves to a sixth process step  276  which commands the transmission  40  to the operator requested Drive range. The method  250  then moves to the seventh process step  278  which resets the previously confirmed position of the shift lever  12  to Drive. The method  250  then terminates at the end point or termination step  260 . 
         [0045]    It will be appreciated that the methods  150 ,  200  and  250  described directly above in connection with  FIGS. 4, 5 and 6  are utilized in conjunction with the virtual Null generating method  100  of  FIG. 3  to accept operator shift commands entered by the vehicle operator through the shift lever  12  to change from one operating range or state to another. For example, the method  150  of  FIG. 4  operates in conjunction with the method  100  of  FIG. 3  when a Reverse or Neutral request is received from the operator when the transmission is in Drive; the method  200  of  FIG. 5  operates in conjunction with the method  100  of  FIG. 3  when a Reverse or Drive request is received from the operator when the transmission  40  is in Neutral and the method  250  of  FIG. 6  operates in conjunction with the method  100  of  FIG. 3  when a Drive or Neutral request is received from the operator when the transmission  40  is in Reverse. 
         [0046]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.