Abstract:
A gear shifter performs an abutment learning, having a reference value learner that sets a reference value of a position signal when abutting a drive object to a stopper, and reduces warpage by (i) an all phase power supply supplying to the electric current to all of the plural phase coils of the direct current motor, and (ii) by reducing an amount of the electric current supplied to the coils, and by decreasing a pressing force of the drive object pressing the drive object against the stopper. The reference value determined at a warpage diminish time enables a reduction of variation of the reference value due to an influence of the warpage, thereby setting a robust reference value to account for an environmental condition such as a temperature change, for an accurate shift operation of the gear shifter.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2015-076274, filed on Apr. 2, 2015, the disclosure of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure generally relates to a shift range switch device, or a gear shifter, disposed in a vehicle, and more specifically, relates to a reference value check for checking a reference value of a signal indicative of a shift range, or a gear. 
       BACKGROUND INFORMATION 
       [0003]    Conventionally, the shift range switch device, or the gear shifter, performs the reference value check by performing an “abutment learning” in a technical phrase in the art. For example, a patent document, JP 2013-59162 A (patent document 1) in the following discloses such a learning. 
         [0004]    The gear shifter includes a drive object driven by a motor torque from a direct current motor to shift from one position to the other, for enabling a gear shifting of an automatic transmission, a stopper regulating a move range of the drive object on one end of the move range, a position detector outputting a position signal indicative of a position of a rotor of the motor, and a controller controlling an operation of the motor based on the position signal. 
         [0005]    In the gear shifter of the patent document 1, the drive object is provided as a one-body combination of a detent plate and a control rod together with other parts, and the stopper is a detent spring. The position detector is an encoder included in an electric actuator. 
         [0006]    Further, a microcomputer in an Steer By Wire-Electronic Control Unit (SBW-ECU) serving as the controller uses the position signal from the encoder as a signal indicative of a shift range, or a gear position, for determining to which the shift range, or the gear position, the gear shifter is currently set. 
         [0007]    Then, upon receiving a shift range switch instruction, the controller controls the electric actuator based on the position signal, and shifts the drive object so that the instructed shift range is set. 
         [0008]    In such control scheme of the gear shifter, the position signal from the encoder is a count value with reference to a certain reference value that is set after a start-up of an Electronic Control Unit (ECU). Therefore, once a reset of such reference value is performed, the reference value must be set again. 
         [0009]    For example, in case a memory of the reference value is lost during a sudden power interruption during a travel of a vehicle, the reference value must be set again during an initialization of the shift range switch device. 
         [0010]    The setting of the reference value is performed based on an abutment learning. That is, in the abutment learning, the drive object is abutted to a certain stopper, and the position signal indicative of such a position of the drive object is set and used as the reference value. 
         [0011]    However, the abutment of the drive object to the stopper causes a warpage on both of the drive object and the stopper. Further, the amount of warpage may change depending on the temperature or the like, thereby possibly causing a variation of the reference value. 
       SUMMARY 
       [0012]    It is an object of the present disclosure to provide a gear shifter, or a shift range switch device, capable of removing an influence of a warpage in the abutment learning for setting a reference value. 
         [0013]    In an aspect of the present disclosure, the shift range switch device of the present disclosure includes a direct current motor having plural phase coils for a rotation of a rotor in the direct current motor by a power supply of a direct electric current orderly to each of the plural phase coils, a drive object driven by a motor torque from the direct current motor, a shift of the drive object enabling a gear shifting of an automatic transmission, a stopper regulating a move range of the drive object on one end of the move range, a position detector outputting a position signal indicative of a position of the rotor, and a controller controlling an operation of the direct current motor based on the position signal. 
         [0014]    The controller has a reference value learner that sets a reference value of the position signal by abutting the drive object to the stopper when a preset condition is satisfied. Also, the reference value learner is configured to abut the drive object to the stopper, reduce warpage caused by the abutting, determine the reference value by detecting that the warpage is diminished, and setting a value of the position signal as the reference value upon detecting that the warpage has diminished. Further, the warpage is reduced by (i) an all phase power supply supplying the electric current to all of the plural phase coils of the direct current motor, and (ii) reducing an amount of the electric current supplied to the coils, and by decreasing a pressing force of the drive object pressing the drive object against the stopper while performing the all phase power supply. 
         [0015]    According to an embodiment of the present disclosure, the reference value is determined when the warpage is diminished. Thereby the variation of the reference value under the influence of the warpage is resolved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Objects, features, and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings, in which: 
           [0017]      FIG. 1  is a block diagram of a shift range transfer device in a first embodiment of the present disclosure; 
           [0018]      FIG. 2  is a perspective view of the shift range switch device in the first embodiment of the present disclosure; 
           [0019]      FIG. 3  is an illustration diagram of warpage of components in the shift range switch device in the first embodiment of the present disclosure; 
           [0020]      FIG. 4  is an illustration diagram of a no warpage state of the shift range switch device in the first embodiment of the present disclosure; 
           [0021]      FIG. 5  is a graph of a relationship between an amount of an electric current in a coil and a pressing force in the first embodiment of the present disclosure; 
           [0022]      FIG. 6  is a flowchart of control in a reference value learner in the first embodiment of the present disclosure; 
           [0023]      FIG. 7  is a block diagram of the shift range transfer device in a second embodiment of the present disclosure; and 
           [0024]      FIG. 8  is a time diagram of a relationship between the amount of the electric current in the coil, a detent plate position (i.e., a detection value), and a detent plate position (i.e., a computed value) in the second embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The embodiments of the present disclosure are described in detail as follows. 
       EMBODIMENT 
     Configuration of the First Embodiment 
       [0026]    A shift range switch device  1  in the first embodiment is described with reference to  FIGS. 1 to 6 . 
         [0027]    The shift range switch device  1  is a device that changes the shift range of an automatic transmission  2 , and is provided with a direct-current motor  3 , a drive object  4 , a stopper  5 , a position detector  6 , and a controller  7 . 
         [0028]    The direct-current motor  3  has plural phase coils  10  for each of a U phase, a V phase, and a W phase in the present embodiment, and a rotor  11  of the motor  3  is rotated by an orderly supply of a direct electric current to each of those coils  10  (see  FIG. 3 ). 
         [0029]    In the present embodiment, a speed reduction mechanism  12  is provided in the direct-current motor  3 , and a rotation speed of an output shaft of the motor  3  is determined in consideration of a speed reduction ratio of the speed reduction mechanism  12  based on a rotation speed of the rotor  11 . 
         [0030]    The drive object  4  switches the shift range of the automatic transmission  2  by shifting its own position, and the shift of the drive object  4  is caused by a drive of a torque from the motor  3 . 
         [0031]    The drive object  4  has a control rod  13  that is connected with the output shaft of the direct-current motor  3  for rotation, and a detent plate  15  that is attached to the control rod  13  for its back-and-forth move according to the rotation of the control rod  13 . 
         [0032]    The detent plate  15  has a fan shape, and has plural concave portions  16  arranged along its rotation direction. 
         [0033]    The detent plate  15  is connected with a spool (not illustrated) for switching an oil passage of an oil pressure valve body  18  inside the automatic transmission  12 , which makes it possible to switch the transmission  2  to a P range, an R range, an N range, a D range or the like according to a shift of the position of the spool when the position of the spool is shifted by the rotation of the detent plate  15 . 
         [0034]    A detent spring  20  is attached to the oil pressure valve body  18 , for holding the detent plate  15  at rotation positions, each corresponding to each of those ranges (i.e., P/R/N/D range). 
         [0035]    The detent plate  15  is held at the shift positions when one of the concave portions  16  catches an engager  20   a  at the tip of the detent spring  20 . Thereby, the spool is held in the position of the instructed shift range. 
         [0036]    The detent spring  20  abuts to the detent plate  15  within the concave portion  16  on one end along the rotation direction of the detent plate  15 , substantially serving as the stopper  5  that regulates the move range of the detent plate  15  on one end in the rotation direction. 
         [0037]    The detent plate  15  has a parking rod  22  in L shape connected to the detent plate  15 . A cone  23  provided at the tip of the parking rod  22  is in contact with a lock lever  24 . The lock lever  24  can move up and down about its own rotation axis. That is, the lock lever  24  moves up and down according to the rotation/shift of the detent plate  15 . 
         [0038]    When a convex portion  24   a  of the lock lever  24  fits into a parking gear  25 , a vehicle is held in a parking state. 
         [0039]    That is, the shift range is in the P (i.e., parking) range when the convex portion  24   a  of the lock lever  24  fits into the parking gear  25 . 
         [0040]    The position detector  6  is an encoder (i.e., hereafter designated as an encoder  6 ) built in the direct-current motor  3 . 
         [0041]    The encoder  6  is a rotary encoder of magnetic type, for example, and outputs, as a position signal, a count value of a pulse outputted according to the rotation of the rotor  11 . 
         [0042]    The controller  7  may be an Electronic Control Unit (ECU) that has a microcomputer of well-known type, in which a Central Processing Unit (CPU) is provided for a control process, a calculation process, a memory (e.g., Read-Only Memory (ROM), Random Access Memory (RAM), Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), etc.) is provided for storing programs and data, beside an input circuit, an output circuit, a power supply circuit and the like. 
         [0043]    The controller  7  controls the drive of the direct-current motor  3  based on the position signal that is computed based on the output from the encoder  6 . The controller  7  has a reference value learner  7   a.    
         [0044]    When the predetermined conditions are satisfied, the reference value learner  7   a  abuts the detent plate  15  against the detent spring  20 , and sets up a reference value of the position signal. 
         [0045]    The predetermined conditions may, for example, be described as a situation in which, after a memory of the reference value is lost due to a sudden power interruption during a travel of a vehicle, a start switch  27  of the shift range switch device  1  is turned ON. 
       Feature of the First Embodiment 
       [0046]    The reference value learner  7   a  performs an abutment process, a warpage reduction process, and a reference value determination process respectively described below. 
         [0047]    In the abutment process, the drive object  4  is abutted against the stopper  5 , which causes warpage on one or both of the drive object  4  and the stopper  5 . 
         [0048]    Warpage of the drive object  4  may be bending, deflection or the like of the detent plate  15  and/or twist/contortion of the control rod  13 . 
         [0049]    Warpage of the stopper  5  may be bending, deflection or the like of the detent spring  20 . 
         [0050]    When the direct-current motor  3  is rotated in one direction, the detent plate  15  and the detent spring  20 , which are separate from each other in the first place, abut to each other. That is, the detent plate  15  abuts to the detent spring  20 . When the motor  3  (i.e., the rotor  11 ) is further rotated after a no-reaction force state in which the detent plate  15  receives no reaction force from the detent spring  20 , the warpage of the detent plate  15  as well as the twist of the control rod  13  and the warpage of the detent spring  20  are forcefully caused. 
         [0051]    In  FIG. 3 , such a situation is illustrated. Note that a position of the detent plate  15  shown in a dashed line is a no warpage position of the detent spring  15 . 
         [0052]    In a warped state (i.e., when the warpage is caused), the detent spring  15  exerts a pressing force F that pressed the detent plate  15  against the detent spring  20 . 
         [0053]    In the warpage reduction process, the warpage caused in the abutment process is decreased. 
         [0054]    More practically, an all phase power supply is performed for supplying the electric current to all of the plural phase coils  10  of the direct current motor  3 , and, while performing the all phase power supply, a supply amount of the electric current to the coils  10  is gradually reduced. 
         [0055]    In such manner, the pressing force of the drive object  4  pressing the stopper  5  gradually decreases, thereby allowing a reverse rotation of the detent plate  15  and the rotor  11  according to the reaction force which is caused to cancel the warpage of those components. That is, the detent plate  15  and the rotor  11  rotate in a direction that reduces the warpage of the detent plate  15  and the rotor  11  (see a two-dot chain line arrow in  FIG. 3 ). 
         [0056]    In the reference value determination process, when detecting that the warpage is diminished, the value of the position signal at a time of detecting that warpage is diminished is determined as the reference value. 
         [0057]    The shift range switch device  1  in the present embodiment is provided with a force detector  30  that outputs a force signal that shows the pressing force F. The force detector  30  is a load sensor or the like disposed either on the engager  20   a,  or on a surface of the detent plate  15  with which the engager  20   a  contacts, for example. 
         [0058]    The reference value determination process detects that the warpage is diminished based on the force signal. 
         [0059]    That is, as shown in  FIG. 5 , as the amount of the electric current decreases, the pressing force also decreases, finally down to zero. That is, in such zero pressing force state, the drive object  4  does not press the stopper  5  eventually. The state that the drive object  4  does not press the stopper  5  is, in other words, the state that the warpage is diminished. See  FIG. 4  about the warpage diminished state. 
         [0060]    Then, the position signal from the encoder  6  in such warpage diminished state is used as the reference value. 
         [0061]      FIG. 6  shows a flowchart of control in the reference value learner  7   a.    
         [0062]    First, in Step S 1 , the abutment process is performed. 
         [0063]    Then, in Step S 2 , the all phase power supply is started. 
         [0064]    Then, in Step S 3 , the supply amount of the electric current is decreased in a state in which the all phase power supply is performed (i.e., the warpage reduction process). 
         [0065]    Then, in Step S 4 , whether the warpage is diminished or not is determined (i.e., whether the pressing force F is equal to zero or not is determined in the present embodiment). When it is determined that the warpage is diminished (i.e., the position is determined as a reference position in Step S 5 ), the position signal from the encoder  6  at such timing is determined as the reference value, and the reference value is stored in the memory of the microcomputer (i.e., the reference value determination process). 
       Effects of the First Embodiment 
       [0066]    According to the present embodiment, the reference value is determined in the warpage diminished state, the variation of the reference value due to an influence of the warpage will not be caused. 
         [0067]    In other words, since the reference value does not vary, even when the environmental conditions such as temperature, etc. change, and the shift range switch device is enabled to accurately switch the shift range. 
         [0068]    Further, the warpage is diminished by performing the all phase power supply that supplies the electric current to all of the phase coils  10  of the direct-current motor  3  (i.e., a simple method of gradually decreasing the electric current while performing the all phase power supply). 
       SECOND EMBODIMENT 
       [0069]    The second embodiment is described with reference to  FIGS. 7 to 8 , which focuses on a difference from the first embodiment. 
         [0070]    In the following description, like numbers indicate like parts, that is, pointing to the description of the like parts in the previous embodiments. 
         [0071]    The shift range switch device  1  of the present embodiment does not have the force detector  30 . 
         [0072]    However, the shift range switch device  1  has a drive object position detector  31  that outputs a drive object position signal that shows the position of the drive object  4 . More specifically, the drive object position detector  31  is a position sensing device (i.e., hereafter designated as a position sensor  31 ) that outputs a detent position signal that shows the position of the detent plate  15 . The position sensor  31  is attached to a stationary object that does not move/rotate together with the detent plate  15  (i.e., is a sensor that monitors the move of the detent plate  15 ). 
         [0073]    In the present embodiment, the reference value determination process detects that the warpage is diminished, based on the position signal and the detent position signal from the encoder  6 . 
         [0074]    That is, when the detent plate  15  and the rotor  11  reversely rotate in the warpage reduction process, the rotation of the detent plate  15  and the rotation of the rotor  11  do not match (i.e., do not in synchronization with each other) just after a start of the reverse rotation. This is because the warpage of the detent spring  20  and the twist of the control rod  13  may be reduced, and because of the diminished independent rotations of the spring  20  and the rod  13 . 
         [0075]    However, once the warpage is entirely diminished, the move/rotation of the detent plate  15  and the move/rotation of the rotor  11  start to match (i.e., start to synchronize with each other). The position signal at such a synchronization timing (i.e., in a synchronization state) is used as the reference value. 
         [0076]    More practically, as shown in  FIG. 8 , when a per-unit-time change of the position of the detent plate  15  that is computed based on an actual measurement from the position sensor  31  is compared with a per-unit-time change of the position of the detent plate  15 , which is computed by using the position signal from the encoder  6 , two values (i.e., a speed of change, a slope of the per-unit-time change of the position) match with each other at a certain timing. The reference value is determined at such timing of the matching of the two values. The per-unit-time change of the position may be rephrased as the position change rate. 
         [0077]    The position change rate of the detent plate  15  computed by using the position signal from the encoder  6  is the position change rate of the rotor  11  taking the speed reduction rate of the speed reduction mechanism  12  into consideration. This is because the position change rate of the detent plate  15  is equal to the position change rate of the rotor  11  after such a position change (i.e., rotation) is “reduced” by the speed reduction mechanism  12 , when the rotor  11  and the detent plate  15  are in the synchronization state (i.e., when rotating in synchronization with each other). 
         [0078]    In the present embodiment, instead of performing a zero pressing force determination in Step S 4  of  FIG. 6  for determining whether the pressing force F is equal to zero, whether the move of the detent plate  15  and the move of the rotor  11  start to synchronize with each other is determined. That is, whether the position change rate of the detent plate  15  based on the actual measurement from the position sensor  31  matches (i.e., is equal to) the position change rate of the detent plate  15  computed by using the position signal from the encoder  6  is determined. 
         [0079]    According to the present embodiment, the same effects as the first embodiment are achievable. 
         [0080]    Although the present disclosure has been described in connection with preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art, and such changes, modifications, and summarized schemes are to be understood as being within the scope of the present disclosure as defined by appended claims.