Abstract:
A transmission includes a controller that uses force feedback from a detent mechanism to determine appropriate actuator output for achieving a desired transmission range, which facilitates the implementation of “shift by wire” systems on pre-existing transmission designs.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional patent application No. 61/320,851, filed Apr. 5, 2010, and which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to transmission range control modules. 
     BACKGROUND 
     Automatic, dual clutch and hybrid transmissions include an input member to receive torque from an engine or electric machines, an output member to transfer torque to a final drive system, and a geartrain with a plurality of clutches that are engageable in various combinations to provide a plurality of speed ratios between the input member and the output member. Automatic transmissions, dual clutch and hybrid transmissions have a plurality of driving ranges, which generally include Park, Reverse, Neutral, Drive, and Low, as understood by those skilled in the art. Some transmissions have a selectively rotatable shaft; the rotational position of the shaft determines which of the driving ranges is selected. 
     SUMMARY 
     A transmission is characterized by a plurality of driving ranges. The transmission includes a selectively movable range selection member characterized by a plurality of predetermined range selection member positions. Each of the predetermined range selection member positions corresponds to a respective one of the ranges. An actuator has a selectively movable output member, and is configured to selectively apply torque or force to the output member. A linkage operatively connects the output member to the range selection member such that movement of the output member causes movement of the range selection member, and such that the output member is characterized by a plurality of output member range positions. Each of the output member range positions corresponds to a respective one of the predetermined range selection member positions and a respective one of the ranges. 
     A detent mechanism is operatively connected to the range selection member and is configured to resist movement of the range selection member from each of the predetermined range selection member positions. A controller is operatively connected to the actuator, and is configured to use the resistance of the detent mechanism to determine the plurality of output member range positions. 
     The transmission provided faciliates the implementation of “shift by wire” systems on pre-existing transmission designs by using feedback from the detent mechanism to provide the controller with data regarding how to manipulate the actuator in order to achieve a desired transmission range. 
     A corresponding method is also provided. The method includes providing a transmission characterized by a plurality of driving ranges. The transmission includes a selectively movable range selection member characterized by a plurality of predetermined range selection member positions. Each of the predetermined range selection member positions corresponds to a respective one of the ranges. 
     The transmission also includes an actuator, a linkage, and a detent mechanism. The actuator has a selectively movable output member and is configured to selectively apply torque or force to the output member. The linkage operatively connects the output member to the range selection member such that movement of the output member causes movement of the range selection member, and such that the output member is characterized by a plurality of output member range positions. Each of the output member range positions corresponds to a respective one of the predetermined range selection member positions and a respective one of the ranges. The detent mechanism is operatively connected to the range selection member and is configured to resist movement of the range selection member from each of the predetermined range selection member positions. The method further includes determining the plurality of output member range positions by using the resistance of the detent mechanism. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a transmission system having a range control module; 
         FIG. 2  is a schematic view of the range control module of  FIG. 1 ; 
         FIG. 3  is a schematic view of a detent mechanism operatively connected to the range control shaft of the transmission of  FIG. 1 ; 
         FIG. 4  is another schematic view of a detent mechanism operatively connected to the range control shaft of the transmission of  FIG. 1 ; and 
         FIG. 5  is a schematic view of a detent mechanism operatively connected to the range control shaft of the transmission of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a transmission  10  includes an input member  14  and an output member  18 . A plurality of planetary gear sets (not shown) and a plurality of selectively engageable clutches (not shown) are disposed within the housing  22  of the transmission  10 . The planetary gear sets and the clutches are operable to provide a plurality of different speed ratios between the input member  14  and the output member  18 , as understood by those skilled in the art. The input member  14  is operatively connectable to an engine to receive torque therefrom. The output member  18  is operatively connectable to the drive wheels (not shown) of a vehicle to deliver torque thereto. Hybrid transmissions may not include an input member  14  from an engine but will contain electric machines attached to the transmission or housed inside of the transmission to produce driving torque. 
     The transmission  10  is characterized by a plurality of transmission driving ranges, or modes. In the embodiment depicted, the transmission driving ranges include “Park,” “Reverse,” “Neutral,” “Drive,” and “Low.” The transmission  10  is configured such that the position of a selectively movable range selection member (with respect to the housing  22 ) determines which of the driving ranges is selected. In the embodiment depicted, the transmission range selection member is a selectively rotatable shaft  26 . More specifically, the shaft  26  is characterized by a plurality of predetermined range selection member positions; each of the predetermined range selection member positions corresponds to a respective one of the ranges. That is, each of the predetermined range selection member positions causes the transmission  10  to operate in a respective one of the driving ranges. 
     Accordingly, when the shaft  26  is in a first predetermined range selection member position, the transmission  10  is in the “Park” range; when the shaft  26  is in a second predetermined range selection member position, the transmission  10  in the “Reverse” range; when the shaft  26  is in a third predetermined range selection member position, the transmission  10  is in the “Neutral” range; when the shaft  26  is in a fourth predetermined range selection member position, the transmission  10  is in the “Drive” range; and when the shaft  26  is in a fifth predetermined range selection member position, the transmission  10  is in the “Low” range. In the embodiment depicted, the predetermined range selection member positions are rotary positions. 
     A shift-by-wire system  30  includes a range control module (RCM)  34  mounted with respect to the housing  22 . The RCM  34  is configured to cause the transmission  10  to enter the transmission driving range desired by a driver of the vehicle by moving the shaft  26  to the predetermined range selection member position that corresponds to the desired range. More specifically, and with reference to  FIG. 2 , the RCM  34  includes an electronic controller  38 , an actuator  42 , and a resolver  46 . The actuator  42  has a selectively movable output member, and is configured to selectively apply force or torque to the output member. In the embodiment depicted, the actuator  42  is an electric motor having a stator  50  and a rotor  54 . The rotor  54  is the output member. The resolver  46  is a sensor that is configured to measure the rotational position of the rotor  54  and the rotational velocity of the rotor  54  with respect to the stator  50 . 
     The motor  42  is operatively connected to the shaft  26  and is configured to selectively rotate the shaft  26 , thereby to change the selected transmission range. More specifically, and with reference to  FIGS. 1 and 2 , a linkage  56  operatively connects the rotor  54  to the shaft  26  such that movement of the rotor  54  causes movement of the shaft  26 , and such that the rotor  54  is characterized by a plurality of output member range positions. Each of the output member range positions corresponds to a respective one of the predetermined range selection member positions and a respective one of the ranges. 
     That is, the linkage operatively connects the rotor  54  to the shaft  26  such that the position of the rotor  54  determines the transmission range selected. Thus, each of the output member range positions of the rotor  54  causes the transmission  10  to operate in a respective one of the driving ranges. The linkage  56  in the embodiment depicted includes a shift cable  58  and an arm  62 . The rotor  54  of the motor  42  is operatively connected to the shift cable  58 , which in turn is connected to the shaft  26  by the arm  62 . Rotation of the rotor  54  thereby causes rotation of the shaft  26 . It should be noted that output member range positions may be measured from a reference position of the rotor  54  with respect to the stator  50 , and may cover a range that is greater than 360 degrees. 
     It should be noted that the transmission  10 , RCM  34 , and linkage  56  are shown schematically, and thus the relative sizes and positions of the transmission, cable  58 , and RCM  30  may or may not vary considerably from what is shown in  FIG. 1 . For example, it may be desirable in some circumstances to position the RCM  34  farther from the shaft  26  than what is shown, depending upon packaging considerations, etc. Furthermore, it should be noted that, although the linkage  56  between the RCM  34  and the shaft  26  includes a flexible cable  58  in the embodiment depicted, other linkages may also be employed within the scope of the claimed invention. For example, cable  58  may be replaced by one or more rigid linkages pivotably connected to one another. 
     The controller  38  is operatively connected to controls (not shown) in the passenger compartment (not shown) of the vehicle. The controls are configured to generate electronic signals in response to manipulation by a driver of the vehicle. The electronic signals generated by the controls are indicative of the driver&#39;s desired transmission range. The controls transmit the electronic signals indicative of the driver&#39;s desired transmission range to the controller  38 . The controller  38  is operatively connected to the actuator  42  and is configured to cause the actuator  42  to move the shaft  26  to the position corresponding to the desired transmission range in response to the signals indicative of the driver&#39;s desired transmission range. 
     Referring to  FIG. 3 , a detent mechanism  66  is operatively connected to the shaft  26  and is configured to resist movement of the shaft  26  from each of the predetermined range selection member positions. More specifically, the detent mechanism  66  includes a first detent member  70  operatively connected to the shaft  26  for rotation therewith. The first detent member  70  defines surface  74 , which is characterized by peaks  78 ,  178 ,  278 ,  378 ,  478 ,  578 ; valleys  82 ,  182 ,  282 ,  382 ,  482 ; and ramps  86 ,  186 ,  286 ,  386 ,  486 ,  586 ,  686 ,  786 ,  886 ,  986 . Ramp  86  interconnects peak  78  and valley  82 . Ramp  186  interconnects valley  82  and peak  178 . Ramp  286  interconnects peak  178  and valley  182 . Ramp  386  interconnects valley  182  and peak  278 . Ramp  486  interconnects peak  278  and valley  282 . Ramp  586  interconnects valley  282  and peak  378 . Ramp  686  interconnects peak  378  and valley  382 . Ramp  786  interconnects valley  382  and peak  478 . Ramp  886  interconnects peak  478  and valley  482 . Ramp  986  interconnects valley  482  and peak  578 . 
     The detent mechanism  66  also includes a second detent member  90  that contacts surface  74 . A spring  94  is mounted with respect to the transmission housing  22  and biases the second detent member  90  against surface  74 . In the embodiment depicted, member  90  is part of the spring  94 . Accordingly, as the shaft  26  and the first detent member  70  rotate, the second detent member  90  traverses the peaks, valleys, and ramps of surface  74 . The detent mechanism  66  and the transmission  10  are configured such that the second detent member  90  contacts one of the valleys  82 ,  182 ,  282 ,  382 ,  482  when the shaft  26  is in one of the predetermined range selection member positions. More specifically, the transmission is in the “Park” range when the member  90  contacts valley  82 , the transmission is in the “Reverse” range when the member  90  contacts valley  182 , the transmission is in the “Neutral” range when the member  90  contacts valley  282 , the transmission is in the “Drive” range when the member  90  contacts valley  382 , and the transmission is in the “Low” range when the member  90  contacts valley  482 . 
     When the second member  90  contacts any of the valleys  82 ,  182 ,  282 ,  382 ,  482 , rotation of the shaft  26  causes the second member  90  to ascend one of the ramps  86 ,  186 ,  286 ,  386 ,  486 ,  586 ,  686 ,  786 ,  886 ,  986 , which causes elastic deformation of the spring  94 ; accordingly, the spring  94  resists rotation of the shaft  26  from each of the predetermined range selection member positions. 
     Since the rotor  54  of the motor  42  is operatively connected to the shaft  26  via the shift cable  58  and arm  62 , the rotational position of the rotor  54  determines the rotational position of the shaft  26 . Accordingly, each of the transmission ranges corresponds to a respective rotational position of the rotor  54  (i.e., the output member range positions). The controller  38  is configured to use the resistance of the detent mechanism  66  to determine the plurality of output member range positions. 
     More specifically, the controller  38  is configured to perform a method whereby the controller  38  determines and/or confirms which positions of the rotor  54  correspond to the transmission ranges based on the resistance to movement of the rotor  54  applied by the detent mechanism  66 . As used herein, “determining” the plurality of output member range positions includes confirming that a prerecorded set of output member range positions are accurate. 
     In a first embodiment, the method performed by the controller  38  includes causing the output member, i.e., the rotor  54 , to move. In the embodiment depicted, the controller  38  causes the rotor  54  to move by controlling the actuator  42  such that the actuator  42  applies torque to the rotor  54 . Causing the rotor  54  to move results in movement of the cable  58 , which in turn causes the shaft  26  and the first detent member  70  to rotate. As the shaft  26  rotates through all of the possible transmission range locations, i.e., the predetermined range selection member positions, the second member  90  traverses surface  74 , including all of the valleys  82 ,  182 ,  282 ,  382 ,  482 . The method also includes monitoring the rotational position of the rotor  54  (using the resolver  46 ) and the force or torque applied by the actuator  42  (using, for example, back electromotive force) while causing the rotor  54  to move. 
     The method performed by the controller also includes recording the positions of the output member, i.e., the rotor  54 , at which the amount of torque or force applied by the actuator  42  increases or changes direction. The torque that must be supplied by the motor  42  to rotate the shaft  26  varies with the rotational position of the shaft  26  due to the detent spring  94 . More specifically, when the second detent member  90  is in any one of the valleys  82 ,  182 ,  282 ,  382 ,  482 , rotation of the shaft  26  in either direction causes elastic strain of the spring  94 , and thus more torque is required from the motor  42  to rotate the shaft  26 . When the member  90  is on any one of the peaks, rotation of the shaft in either direction results in energy stored by the spring  94  assisting the rotation of the shaft  26 , thereby requiring less torque from the motor  42 . 
     Thus, and with reference to  FIG. 4 , the shaft  26  is between the “Park” position and the “Reverse” position, with the member  90  on ramp  286  adjacent peak  178 . The detent spring  94  exerts a force on the ramp  286  that urges the shaft  26  toward the Reverse position. Accordingly, movement of the shaft  26  from the position indicated in  FIG. 4  to the position indicated in  FIG. 5  requires less torque from the motor  42  than movement of the shaft  26  from the position indicated in  FIG. 5  to the position indicated in  FIG. 4 . The shaft  26  is in the Reverse position when the detent member  70  is in the position shown in  FIG. 5 . 
     Similarly, and with reference to  FIG. 3 , the shaft  26  is between the “Reverse” position and the “Neutral” position, with the member  90  on ramp  386  adjacent peak  278 . The detent spring  94  exerts a force on the ramp  386  that urges the shaft  26  toward the Reverse position. Accordingly, movement of the shaft  26  from the position indicated in  FIG. 3  to the position indicated in  FIG. 5  requires less torque from the motor  42  than movement of the shaft from the position indicated in  FIG. 5  to the position indicated in  FIG. 3 . 
     Thus, the controller  38  can determine which rotational position of the rotor  54  corresponds to the “Reverse” position of the shaft  26  (when member  90  is at valley  182 ) by determining the position of the rotor  54  when the applied torque changes. The controller  38  may cause the shaft  26  to rotate so that the member  90  traverses ramps  286  and  386  several times, taking average values to calculate the “Reverse” position. The controller  38  then repeats these steps for each of the other transmission range positions to determine the rotor  54  positions that correspond to “Park,” “Neutral,” “Drive,’ and “Low.” The controller  38  records the rotor positions that correspond to each of the transmission ranges for future use, i.e., when the controller  38  receives a signal to move the transmission to one of the ranges. 
     That is, the predetermined range selection member positions will be approximately where the force or torque applied by the actuator  42  changes direction, i.e. where the actuator goes from holding the detent back to pushing against the detent. In order to account for hysteresis in the park system, the method may also include rotating the shaft  26  in a first direction and then rotating the shaft  26  in a second direction, and for each range, monitoring the two shaft positions at which a torque or force reversal occurs. The method would then further include interpolating between the two shaft positions at which a torque or force reversal occurs to determine the nominal predetermined range selection member position. Recording positions of the output member at which the amount of torque or force applied by the actuator increases or changes direction may include recording average positions or interpolated positions within the scope of the claimed invention. 
     The controller  38  may instead be configured to perform an alternative method whereby the controller  38  determines and/or confirms which positions of the rotor  54  correspond to the transmission ranges. The alternative method includes causing the output member, i.e., the rotor  54 , to move to preselected output member positions, and subsequently allowing the output member to move freely from each of the preselected output member positions to a respective one of the output member range positions. In other words, the controller causes the motor  42  to move the cable  58  a specified amount so that the shaft  26  moves to a predicted range location, and then lets the motor  42  go into a “torque free” mode in which the force of the detent spring  94  will move the shaft  26  any remaining distance to the proper shaft location, i.e., one of the predetermined range selection member positions. The detent spring  94  will “back” drive the free-wheeling rotor  54  to the correct position. Once this happens, the controller  38  will record the rotor  54  location as the correct location for that requested range. The process is repeated for each range location. 
     Thus, for example, the controller  38  has a stored rotor position that corresponds to the “Reverse” range. To determine the accuracy of the stored rotor position, the controller  38  commands the motor  42  to move the rotor  54  to the stored rotor position that corresponds to the “Reverse” range, i.e., the position that is predicted to result in the shaft  26  being in the “Reverse” position. If the commanded position of the rotor  54  is inaccurate and results in the shaft  26  being in either of the positions indicated in  FIGS. 3 and 4 , then the spring  94  will move the shaft  26  to the “Reverse” position shown in  FIG. 5  once the controller  38  permits the rotor  54  to “free-wheel.” The controller  38  then records the position of the rotor  54  when the shaft  26  is in the position indicated by  FIG. 5  as a corrected “Reverse” position. The controller  38  repeats these steps for each of the other transmission ranges (Park, Neutral, Drive, and Low), and stores the rotor  54  positions that result in those ranges. Accordingly, when a vehicle driver transmits a signal to the controller  38  that a particular range is desired, the controller  38  causes the rotor  54  to move to the corrected position corresponding to the desired transmission range. 
     The methods employed by the controller  38  may be performed during transmission assembly and/or at various times during the service life of the automobile. The methods allow implementation of shift by wire technology on automatic, dual clutch and hybrid transmissions without extensive transmission hardware and software redesign to existing transmission systems and related shifter cables. The methods also eliminate manual adjustment of shifter cables in vehicle assembly plant and provide end of line testing capability to verify operation. 
     The actuator in the embodiment depicted is a motor  42 , and the output member of the actuator is the rotor  54 . However, other actuators may be employed within the scope of the claimed invention. For example, the actuator may be a solenoid or other actuator having an output member with linear movement. In such an embodiment, a sensor configured to monitor the linear displacement of the output member would replace the resolver, and the controller  38  would monitor force applied by the actuator instead of torque. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.