Abstract:
A shifting apparatus includes an actuator to direct a travel range setting of a vehicle transmission, a selector to indicate a desired travel range setting, a transmission controller to move the actuator into the travel range setting in response to the desired travel range setting of the selector, and a restrictor to restrict an output of a drive motor if the vehicle transmission is in a travel range setting other than the desired travel range setting. A method to control a vehicle transmission includes detecting a travel range setting of the vehicle transmission, detecting a desired travel range setting of a selector, and entering a limp-home mode if the detected travel range setting is different from the desired travel range setting and a detected vehicle travel direction corresponding to the detected travel range setting is the same as a desired travel direction corresponding to the desired travel range setting.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from Japanese Patent Application No. 2008-043809, filed Feb. 26, 2008, the contents of which are hereby incorporated by reference in their entirety. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    1. Field of the Disclosure 
         [0003]    Embodiments of the present disclosure relate to a sift-by-wire fail control device for a vehicle with an automatic transmission (e.g., a continuously variable or “stepless” transmission, a step automatic transmission, or an automated manual transmission capable of automatically shifting gears of a manual transmission). 
         [0004]    2. Description of the Related Art 
         [0005]    An typical automatic transmission has a park (P) range, a reverse travel (R) range, a neutral (N) range, a forward automatic transmission (D) range, and the like, determining respective gear-shift modes, in that order. A driver may perform a manual selection operation among these ranges. A manual valve is moved in accordance with the selection operation. When the manual valve is located at a position corresponding to the selected range, gear-shift corresponding to the selected range is obtained. 
         [0006]    Thus, a shift lever operated by a driver has been typically mechanically coupled with a manual valve by a link mechanism, a wire, or the like, and hence, the manual valve has been moved in accordance with a selection operation using the mechanical system. 
         [0007]    Because the link mechanism, the wire, or the like, is provided, the mechanical system may require a relatively large amount of (volumetric) space. In addition, the use of electronic control and the reduction in size of vehicles are becoming more commonplace in recent years. Thus, a so-called “shift-by-wire” automatic transmission has been suggested, in which a manual valve is moved in accordance with a selection operation by a driver under electronic control. 
         [0008]    In the former shift-by-wire system, the selection operation with the shift lever is electronically detected, an actuator is moved in accordance with a detection signal, and the manual valve is shifted to a range position corresponding to the selection operation. 
         [0009]    The system meets the requirements for electronic control reduction in size of vehicles because the large arrangement space for the mechanical system, such as the link mechanism or the wire, is not necessary. 
         [0010]    In the shift-by-wire system, because the manual valve is moved in accordance with the selection operation under the electronic control, it is important to take a measure for fail-safe, to prepare for an unexpected situation, such as that the manual valve is not moved in accordance with the selection operation due to a failure in the actuator or a failure in an electronic control system. 
         [0011]    Formerly, for example, Japanese Unexamined Patent Application Publication No. 06-213025 suggested a mechanism for fail-safe. In the mechanism, the output of an engine was reduced when a failure occurs in a traveling condition, the failure in which a manual valve is not moved in accordance with a selection operation; and the operation of the engine was stopped when the failure occurs in a stop condition. 
         [0012]    Unfortunately, with such a mechanism for fail-safe, the operation of the engine is unconditionally stopped in any situation when a vehicle is stopped and if the failure, in which the manual valve is not moved in accordance with the selection operation, occurs. Hence, the vehicle is inhibited from traveling. 
         [0013]    Therefore, even when a driver intends to drive the vehicle to a repair shop, to the driver&#39;s home, or to a safe parking location, the vehicle may not travel from a stopped position under its own power, and hence, the vehicle must be moved by a wrecker or tow truck. 
       SUMMARY OF THE CLAIMED SUBJECT MATTER 
       [0014]    In one aspect, embodiments disclosed herein relate to a shifting apparatus of a vehicle transmission including an actuator to direct the vehicle transmission into a travel range setting, a selector to select a desired travel range setting, an actuator detector to output the travel range setting of the actuator to a transmission controller, a selector detector to output the desired travel range setting of the selector to the transmission controller, the transmission controller to move the actuator into the travel range setting in response to the desired travel range setting of the selector, and a restrictor device to restrict an output of a drive motor if the transmission controller determines the actuator to be in a travel range setting other than the desired travel range setting determined by the selector detector. 
         [0015]    In another aspect, embodiments disclosed herein relate to a method to control a vehicle transmission including detecting a travel range setting of the vehicle transmission, detecting a desired travel range setting of a selector, entering a limp-home mode if the detected travel range setting is different from the desired travel range setting, and a detected vehicle travel direction corresponding to the detected travel range setting is the same as a desired travel direction corresponding to the desired travel range setting. 
         [0016]    In another aspect, embodiments disclosed herein relate to a shifting apparatus of a vehicle transmission including an actuator to direct a travel range setting of the vehicle transmission, a selector to indicate a desired travel range setting, a shift unit to move the actuator into the travel range setting in response to the desired travel range setting of the selector, and a restrictor to restrict an output of a drive motor if the vehicle transmission is in a travel range setting other than the desired travel range setting. 
         [0017]    In another aspect, embodiments disclosed herein relate to a vehicle including a drive motor and a vehicle transmission including a means for indicating a desired travel range setting, a means for directing a travel range setting of the vehicle transmission in response to the indicated desired travel range setting, and a means for restricting an output of a drive motor if the directed travel range setting is other than the desired travel range setting. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]    Features of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings. 
           [0019]      FIG. 1  is a schematic system diagram showing a powertrain and its control system of a vehicle with a V-belt type continuously variable transmission including a shift-by-wire fail control device according to an embodiment of the present disclosure. 
           [0020]      FIG. 2  depicts a hydraulic circuit diagram showing a hydraulic control system and a manual valve and its actuator, the hydraulic control system relating to a forward/reverse change mechanism of the V-belt continuously variable transmission in  FIG. 1 . 
           [0021]      FIG. 3  is an action diagram showing a detent mechanism of the manual valve in  FIG. 2  when the manual valve is located at an intermediate position between range positions. 
           [0022]      FIG. 4  is a block diagram showing a portion relating to shift-by-wire fail control and a portion for shift-by-wire control of a transmission controller in  FIG. 1 . 
           [0023]      FIG. 5  is a flowchart showing a shift-by-wire fail control program executed by the transmission controller in  FIG. 1 . 
           [0024]      FIG. 6  is a table showing control contents of the shift-by-wire fail control shown in  FIG. 5  respectively for failure conditions of a shift-by-wire system. 
           [0025]      FIG. 7  is a table showing control contents of the shift-by-wire fail control shown in  FIG. 5  respectively for other failure conditions of the shift-by-wire system. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    An implementation of an exemplary embodiment of the present disclosure is described below in detail according to the Figures. 
         [0027]      FIG. 1  illustrates a powertrain and its control system of a vehicle with a V-belt continuously variable transmission including a shift-by-wire fail control device according to the embodiment of the present disclosure. 
         [0028]    An engine  1  serving as a motor, and an automatic transmission  2  define a powertrain for a vehicle with an automatic transmission. 
         [0029]    The automatic transmission  2  converts the speed of rotation of the engine  1  in accordance with a selected gear ratio and to an output rotation speed. In select embodiments, the automatic transmission  2  may be a V-belt continuously variable transmission. As such, the automatic transmission  2  may include an input shaft  3 , a forward/reverse change mechanism  4 , a V-belt transmission mechanism  5 , and an output shaft  6 . The rotation from the engine  1  may be input to the input shaft  3  through a lockup torque converter T/C. 
         [0030]    The forward/reverse change mechanism  4  may have a double pinion planet gear set  7 . When a forward clutch  8  is engaged, the rotation of the input shaft  3  can be directly transmitted to the V-belt transmission mechanism  5 . When a reverse brake  9  is engaged, the rotation of the input shaft  3  is reversely transmitted to the V-belt transmission mechanism  5 . When both the forward clutch  8  and the reverse brake  9  are disengaged, the rotation of the input shaft  3  is not transmitted to the V-belt transmission mechanism  5 . 
         [0031]    The V-belt transmission mechanism  5  may include a primary pulley  10  at a driving side, a secondary pulley  11  at a driven side, and a V-belt  12 . The primary pulley  10  receives the rotation from the forward/reverse change mechanism  4 . The secondary pulley  11  is coupled to be located on the output shaft  6 . The V-belt  12  is wound around or displaced about the pulleys  10  and  11 . 
         [0032]    The primary and secondary pulleys  10  and  11  include flanges  10   a  and  11   a  which may rotate with respect to other flanges. The flanges  10   a  and  11   a  may be movable flanges that may be shifted in an axial direction. The positions of the movable flanges  10   a  and  11   a  may be controlled using a difference between a pressure in a cylinder chamber  10   b  and a pressure in a cylinder chamber  11   b.    
         [0033]    The V-belt transmission mechanism  5  transmits the rotation of the primary pulley  10  to the secondary pulley  11  via the V-belt  12 , and then to the output shaft  6 . 
         [0034]    During the transmission of the rotation, a line pressure, which may be a gear-shift control original pressure in accordance with a transmission input torque, may be supplied to the secondary-pulley cylinder chamber  11   b . A gear-shift control pressure, which may be determined by a gear-shift control valve using the line pressure as an original pressure, may be supplied to the primary-pulley cylinder chamber  10   b . The position of the movable flanges  10   a  and  11   a  in the axial direction may be controlled on the basis of the ratio of the gear-shift control pressure of the primary-pulley cylinder chamber  10   b  to the line pressure of the secondary-pulley cylinder chamber  11   b . Thus, an arc diameter of the V-belt  12  wound around the pulleys  10  and  11 , that is, an inter-pulley transmission ratio (i.e., a gear ratio) may be controlled. 
         [0035]    The V-belt transmission mechanism  5  may change the gear ratio continuously from a lowermost-speed gear ratio toward a high-speed gear ratio (upshift) in a stepless (or continuous) manner by increasing the gear-shift control pressure (primary pulley pressure), and the V-belt transmission mechanism  5  may change the gear ratio continuously reversely toward the lowermost-speed gear ratio (downshift) in a stepless manner by reducing the gear-shift control pressure (primary pulley pressure). 
         [0036]    The rotation from the V-belt transmission mechanism  5  to the output shaft  6  is input to a differential gear device (not shown). The differential gear device drives left and right driving wheels of the vehicle (not shown), so that the vehicle travels. 
         [0037]    The engine  1  may be a gasoline engine. A throttle valve  13  for output determination may not be mechanically coupled with an accelerator pedal  14  operable by the driver. The throttle valve  13  is separated from the accelerator pedal  14 , and a throttle actuator  15  changes the opening of the throttle valve  13  instead under the electronic control. Therefore, the engine  1  may be a throttle-by-wire gasoline engine in which the opening (throttle valve opening TVO) of the throttle valve  13  is electronically controllable. 
         [0038]    The throttle actuator  15  is moved in accordance with a throttle valve opening (TVO) instruction from an engine controller  16 . 
         [0039]    The engine controller  16  may determine the throttle valve opening (TVO) to a value corresponding to the degree of depression (accelerator pedal opening APO) of the accelerator pedal  14 . Thus, an accelerator pedal opening sensor  17  is provided to detect the accelerator pedal opening APO. 
         [0040]    The engine controller  16  may obtain the throttle valve opening (TVO) instruction using the accelerator pedal opening APO detected by the sensor  17  with reference to a predetermined map. The engine controller  16  may give the instruction to the throttle actuator  15 , and electronically controls the opening of the throttle valve  13  (throttle valve opening TVO) so as to basically correspond to the accelerator pedal opening APO. The throttle valve opening (TVO) instruction, that is, the opening of the throttle valve  13  (throttle valve opening TVO) may be optionally controlled by a factor other than the accelerator pedal operation, for shift-by-wire fail control (described layer) which is a feature of the present disclosure. 
         [0041]    The V-belt continuously variable transmission  2  may include a selector lever  21   a , which is illustrated in  FIG. 1  independently from the V-belt continuously variable transmission  2  for convenience. The driver may use the selector lever  21   a  to select a gear-shift mode by a manual operation (selection operation) and to give the instruction of the selected gear-shift mode. 
         [0042]    The selector lever  21   a  may penetrates through a transmission tunnel in a vehicle floor (not shown) and may be located near a driver&#39;s seat. The driver may manually operate the selector lever  21   a  according to an operation pattern  21 , to select and to give the instruction of the selected gear-shift mode. 
         [0043]    The operation pattern  21  of the selector lever  21   a  may include a P range position at which the V-belt continuously variable transmission  2  is set to a park (P) range, an R range position at which the V-belt continuously variable transmission  2  is set to a reverse travel (R) range, an N range position at which the V-belt continuously variable transmission  2  is set to a neutral (N) range, and a D range position at which the V-belt continuously variable transmission  2  is set to a forward automatic transmission (D) range. The P range position, R range position, N range position, and D range position may be linearly arranged in that logical order but those having ordinary skill in the art will appreciate that other orders may be used. 
         [0044]    In addition, a P range switch  22   p  that outputs a P range signal when the selector lever  21   a  may be located at the P range position. Similarly, an R range switch  22   r  that outputs an R range signal when the selector lever  21   a  is located at the R range position, an N range switch  22   n  that outputs an N range signal when the selector lever  21   a  is located at the N range position, and a D range switch  22   d  that outputs a D range signal when the selector lever  21   a  is located at the D range position, may be arranged at the selector-lever operation pattern  21 . 
         [0045]    A hydraulic circuit for engagement/disengagement control of the forward clutch  8  and the reverse brake  9  in the V-belt continuously variable transmission  2  in  FIG. 1  may be described below with reference to  FIG. 2 . 
         [0046]    In  FIG. 2 , a manual valve  41  may be moved in accordance with a range change operation (selection operation) with the selector lever  21   a . However, the manual valve  41  may not be mechanically coupled with the selector lever  21   a . Though described later in detail, the manual valve  41  may be a shift-by-wire type in which the manual valve  41  is moved in accordance with a selection operation with the selector lever  21   a  under electronic control. 
         [0047]    Hence, at the manual valve  41 , the park (P) range position, the reverse travel (R) range position, the neutral (N) range position, and the forward automatic transmission (D) range position may be arranged adjacently to each other in that order. A selection actuator  42  may cause a spool  41   a  of the manual valve  41  to be shifted to one of the range positions under the electronic control. 
         [0048]    The manual valve  41  may be connected to a line pressure circuit  43 , to which a line pressure PL (gear-shift control original pressure of the V-belt continuously variable transmission  2 ) is supplied; a forward pressure circuit  44  toward the forward clutch  8 ; and a reverse pressure circuit  45  toward the reverse brake  9 . A connection portion of the forward pressure circuit  44  and a connection portion of the reverse pressure circuit  45  may be arranged on both sides of a connection portion of the line pressure circuit  43  in a manual-valve axial direction. 
         [0049]    The manual valve  41  at the neutral (N) range position in the figure causes the line pressure circuit  43  to be connected to an enclosed space between lands at both ends of the spool  41   a , so that the line pressure circuit  43  is fully closed (i.e., isolated from forward and reverse pressure circuits  44  an  45 ). In addition, in this neutral (N) position, the manual valve  41  allows the forward pressure circuit  44  and the reverse pressure circuit  45  to be in communication with drain ports  41   b  and  41   c , so that any forward clutch pressure Pf (the engagement pressure of the forward clutch  8 ) and any reverse brake pressure Pr (the engagement pressure of the reverse brake  9 ) may be removed respectively through the drain ports  41   b  and  41   c . Both the forward clutch  8  and the reverse brake  9  may be disengaged, and hence, the V-belt continuously variable transmission  2  becomes a neutral condition in which power transmission is inhibited. 
         [0050]    In the forward (D) position, the manual valve  41  allows the forward pressure circuit  44  to be disconnected from the drain port  41   b  and to be connected to the line pressure circuit  43 , so that the line pressure PL is directed to the forward clutch  8 . Accordingly, the forward clutch pressure Pf, which is the engagement pressure of the forward clutch  8 , may be generated, and the forward clutch  8  is engaged. Meanwhile, the manual valve  41  causes the reverse pressure circuit  45  to be continuously connected to the drain port  41   c . The reverse brake pressure Pr, which is the engagement pressure of the reverse brake  9 , is removed through the drain port  41   c , so that the reverse brake  9  is disengaged. Accordingly, the V-belt continuously variable transmission  2  is in a condition capable of transmitting forward rotational power. 
         [0051]    Further, in the reverse (R) position, the manual valve  41  allows the reverse pressure circuit  45  to be disconnected from the drain port  41   c . In addition, the manual valve  41  causes the reverse pressure circuit  45  to be connected to the line pressure circuit  43 , so that the line pressure PL is directed to the reverse brake  9 . Accordingly, the reverse brake pressure Pr, which is the engagement pressure of the reverse brake  9 , is generated, and the reverse brake  9  is engaged. Meanwhile, the manual valve  41  causes the forward pressure circuit  44  to be continuously connected to the drain port  41   b . The forward clutch pressure Pf, which is the engagement pressure of the forward clutch  8 , is removed through the drain port  41   b , so that the forward clutch  8  is disengaged. Accordingly, the V-belt continuously variable transmission  2  is in a condition capable of transmitting reverse rotational power. 
         [0052]    When the spool  41   a  of the manual valve  41  is shifted rightward of the reverse travel (R) range position and into to the park (P) range position, the land at the left side of the spool  41   a  ( FIG. 2 ) closes the line pressure circuit  43 . In addition, the forward pressure circuit  44  and the reverse pressure circuit  45  are connected to the drain ports  41   b  and  41   c , so that the forward clutch pressure Pf, which is the engagement pressure of the forward clutch  8 , and the reverse brake pressure Pr, which is the engagement pressure of the reverse brake  9 , are removed through the drain ports  41   b  and  41   c . Accordingly, both the forward clutch  8  and the reverse brake  9  are disengaged, and hence, the V-belt continuously variable transmission  2  becomes the neutral condition in which power transmission is inhibited. 
         [0053]    A detent mechanism  46  may be provided to position the spool  41   a  of the manual valve  41  to one of the P, R, N, and D positions when the spool  41   a  is moved by the selection actuator  42 . 
         [0054]    The detent mechanism  46  may include a detent ball  48  and triangular cut portions  41   p ,  41   r ,  41   n , and  41   d . The detent ball  48  is pressed by a spring  47  toward the spool  41   a  in a direction orthogonal to a moving direction of the spool  41   a . The triangular cut portions  41   p ,  41   r ,  41   n , and  41   d  may be provided at the spool  41   a  so as to position the spool  41   a  to one of the P, R, N, and D positions in cooperation with the detent ball  48 . 
         [0055]    Thus, the arrangement order of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d  corresponds to the arrangement order of the P, R, N, and D range positions at the spool  41   a . Also, the arrangement pitch of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d  corresponds to the arrangement pitch of the P, R, N, and D range positions at the spool  41   a.    
         [0056]    When the detent ball  48  is completely fitted into one of valleys of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d , for example, as shown in  FIG. 2 , the manual valve  41  (spool  41   a ) is correctly positioned at the corresponding range position, and the predetermined gear-shift mode may be achieved. 
         [0057]    When the detent ball  48  is not completely fitted into one of the valleys of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d , and is located on one of inclined surfaces between the valleys of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d , for example, as shown in  FIG. 3 , the manual valve  41  (spool  41   a ) is not located at the corresponding range position, and the predetermined gear-shift mode is not achieved. 
         [0058]    Although the detent ball  48  is located on one of the inclined surfaces between the valleys of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d , if the selection actuator  42  is in an inactive condition (including failure), the detent ball  48  may receive a spring force of the spring  47 , and may be completely fitted into one of the valleys of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d  as indicated by an arrow in  FIG. 3 . At this time, it is expected that the detent ball  48  applies a component force to the spool  41   a  by a cam action in the corresponding moving direction in cooperation with the inclined surface of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d , and the spool  41   a  is correctly positioned at the corresponding range position. 
         [0059]    However, in some cases, it may also be expected that the cam action is not obtained because of, for example, a large frictional coefficient present between the detent ball  48  and the inclined surface of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d , the detent ball  48  is left on the inclined surface between the valleys of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d , and thus the spool  41   a  is not located correctly at the corresponding range position. In this case, the manual valve  41  does not achieve the predetermined gear-shift mode. 
         [0060]    Referring to  FIG. 2 , shut-off valves  51  and  52  may be respectively inserted into the forward pressure circuit  44  and the reverse pressure circuit  45 , in order to perform shift-by-wire fail control according to the embodiment of the present disclosure. 
         [0061]    In a normal condition, the shut-off valves  51  and  52  cause the forward pressure circuit  44  and the reverse pressure circuit  45  to be connected by springs  51   a  and  52   a  as shown in  FIG. 2 . In this state, engagement/disengagement of the forward clutch  8  and the reverse brake  9  by the manual valve  41  are available. When solenoids  51   b  and  52   b  are turned ON, the forward pressure circuit  44  and the reverse pressure circuit  45  are disconnected, and the forward clutch pressure Pf and the reverse brake pressure Pr are removed. The forward clutch  8  and the reverse brake  9  are disengaged regardless of the selected range position of the manual valve  41 , and hence, the V-belt continuously variable transmission  2  becomes the neutral condition in which power transmission is inhibited. 
         [0062]    The hydraulic circuits for the engagement/disengagement of the forward clutch  8  and the reverse brake  9  shown in  FIG. 2  are contained in a control valve body  2   b  shown in  FIG. 1 , together with another gear-shift control hydraulic circuit and a lock-up control hydraulic circuit relating to the V-belt continuously variable transmission  2 . 
         [0063]      FIG. 1 , for its convenience, merely illustrates that the control valve body  2   b  may include the selection actuator  42  for the manual valve  41 , the shut-off valve  51  (solenoid  51   b ) for the forward pressure circuit  44 , the shut-off valve  52  (solenoid  52   b ) for the reverse pressure circuit  45 , and a shift solenoid  53  for a gear-shift control valve (not shown) for the gear-shift control by determining the gear-shift control pressure in the primary-pulley cylinder chamber  10   b  (see  FIG. 1 ). 
         [0064]    A transmission controller  23  in  FIG. 1  performs the engagement/disengagement control of the forward clutch  8  and the reverse brake  9  using the selection actuator  42 , the forward-pressure-circuit shut-off-valve solenoid  51   b , and the reverse-pressure-circuit shut-off-valve solenoid  52   b , in addition to the gear-shift control of the V-belt continuously variable transmission  2  using the shift solenoid  53 . 
         [0065]    The transmission controller  23  may receive a selector lever position (selection operation) signal Dr from a selector-lever position sensor  21   b  of the selector-lever operation pattern  21 , a signal from a vehicle speed sensor  24  that detects a vehicle speed VSP, information relating to a throttle valve opening TVO determined by a throttle valve opening instruction transmitted from the engine controller  16  to the throttle actuator  15 , and a signal from a manual valve range position sensor  25  that detects a range position Tm of the manual valve  41 . 
         [0066]    The transmission controller  23  performs the gear-shift control of the V-belt continuously variable transmission  2  including the engagement/disengagement control of the forward clutch  8  and the reverse brake  9 , and the shift-by-wire fail control which is a feature of the present disclosure, as follows, on the basis of the received information via the control valve body  2   b.    
         [0067]    The gear-shift control may briefly be described first. The transmission controller  23  may drive the selection actuator  42  on the basis of the selector lever position signal Dr from the corresponding one of the range switches  22   p ,  22   r ,  22   n , and  22   d , so that the spool  41   a  of the manual valve  41  is shifted to the corresponding one of the park (P) range position, the reverse travel (R) range position, the neutral (N) range position, and the forward automatic transmission (D) range position. 
         [0068]    Referring to  FIG. 4 , the transmission controller  23  may include a shift-by-wire control section  23   a  for the shift-by-wire control. An actuator control unit  23   b  in the shift-by-wire control section  23   a  may compare a selector lever position Dr (range instructed by the driver) with a current range position Tm of the manual valve  41  detected by the sensor  25 . 
         [0069]    If the selector lever position Dr (instruction range) matches the current range position Tm of the manual valve  41 , the actuator control unit  23   b  turns OFF a solenoid switch  23   c  by not applying current to a solenoid  23   d , and hence an actuator drive circuit  23   e  is inactivated. Accordingly, the selection actuator  42  is inactivated, so that the manual valve  41  is held at the current range position Tm. 
         [0070]    When the selection operation (range change) is made with the selector lever  21   a  and the selector lever position Dr (instruction range) mismatches the current range position Tm of the manual valve  41 , the actuator control unit  23   b  turns ON the solenoid switch  23   c  by applying current to the solenoid  23   d , and hence the actuator drive circuit  23   e  is activated. Accordingly, the selection actuator  42  is driven. 
         [0071]    At this time, the actuator drive circuit  23   e  may be activated and controlled such that a rotation direction and a rotation amount of the selection actuator  42  become a rotation direction and a rotation amount which cause the manual valve  41  to be moved from the current range position Tm to a position corresponding to the selector lever position Dr (instruction range). 
         [0072]    As described above, the manual valve  41  may be moved in accordance with the selection operation (range change) with the selector lever  21   a  under the electronic control, and the manual valve  41  may be moved to the range position instructed by the driver. 
         [0073]    While the manual valve  41  is located at the neutral (N) range position as shown in  FIG. 2 , the line pressure circuit  43  may be connected to the enclosed space between the lands at both ends of the spool  41   a  to prevent the line pressure PL from being removed. Also, the forward pressure circuit  44  and the reverse pressure circuit  45  are respectively connected to the drain ports  41   b  and  41   c  to remove the engagement pressure (forward clutch pressure) Pf of the forward clutch  8  and the engagement pressure (reverse brake pressure) Pr of the reverse brake  9  through the drain ports  41   b  and  41   c . Both the forward clutch  8  and the reverse brake  9  are disengaged, and hence, the V-belt continuously variable transmission  2  becomes the neutral condition in which power transmission is inhibited. 
         [0074]    Also, while the manual valve  41  is located at the forward automatic transmission (D) range position, the forward pressure circuit  44  is disconnected from the drain port  41   b  and connected to the line pressure circuit  43 , so that the line pressure PL is directed to the forward clutch  8 . Accordingly, the engagement pressure Pf of the forward clutch  8  is generated, and the forward clutch  8  is engaged. 
         [0075]    Meanwhile, the reverse pressure circuit  45  is continuously connected to the drain port  41   c . The engagement pressure Pr of the reverse brake  9  is removed through the drain port  41   c , and hence, the reverse brake  9  is held disengaged. Because the reverse brake  9  is disengaged and the forward clutch  8  is engaged, the V-belt continuously variable transmission  2  may transmit forward rotational power. 
         [0076]    While the manual valve  41  may be located at the reverse travel (R) range position, the reverse pressure circuit  45  may be disconnected from the drain port  41   c  and connected to the line pressure circuit  43 , so that the line pressure PL is directed to the reverse brake  9 . Accordingly, the engagement pressure Pr of the reverse brake  9  may be generated, and the reverse brake  9  is engaged. 
         [0077]    Meanwhile, the forward pressure circuit  44  is continuously connected to the drain port  41   b . The engagement pressure Pf of the forward clutch  8  is removed through the drain port  41   b , and hence, the forward clutch  8  is held disengaged. Because the forward clutch  8  may be disengaged and the reverse brake  9  is engaged, the V-belt continuously variable transmission  2  may transmit reverse rotational power. 
         [0078]    After the manual-valve spool  41   a  is shifted rightward of the reverse travel (R) range position ( FIG. 2 ) to the park (P) range position, and while the manual valve  41  is located at the park (P) range position, the land at the left side of the spool  41   a  ( FIG. 2 ) closes the line pressure circuit  43 . Also, the forward pressure circuit  44  and the reverse pressure circuit  45  may be connected to the drain ports  41   b  and  41   c , and the engagement pressure Pf of the forward clutch  8  and the engagement pressure Pr of the reverse brake  9  are removed through the drain ports  41   b  and  41   c . Accordingly, both the forward clutch  8  and the reverse brake  9  may be disengaged, and hence, the V-belt continuously variable transmission  2  becomes the neutral condition in which power transmission is inhibited. 
         [0079]    Because the selector lever  21   a  is located at the D range position, while the transmission controller  23  causes the manual valve  41  to be located at the corresponding D range position under the electronic control, i.e., while the V-belt continuously variable transmission  2  is in the forward-rotational-power transmitting condition as a result of the engagement of the forward clutch  8  and the disengagement of the reverse brake  9 , the transmission controller  23  uses the vehicle speed VSP detected by the sensor  24  and the throttle valve opening TVO obtained by the engine controller  16 , and further obtains a target input rotational speed (target gear ratio) with reference to a predetermined gear-shift map. The target input rotational speed is desirable for a current operation condition. Then, a gear-shift instruction to achieve the target input rotational speed is supplied to the shift solenoid  53 , so as to continuously shift the current transmission input rotational speed to the target input rotational speed. 
         [0080]    Because the selector lever  21   a  is located at the R range position, while the transmission controller  23  causes the manual valve  41  to be located at the corresponding R range position under the electronic control, i.e., while the V-belt continuously variable transmission  2  is in the reverse-rotational-power transmitting condition as a result of the disengagement of the forward clutch  8  and the engagement of the reverse brake  9 , the transmission controller  23  supplies a gear-shift instruction to the shift solenoid  53 , so as to achieve a reverse input rotational speed corresponding to the lowermost (low) gear ratio. Accordingly, the V-belt continuously variable transmission  2  transmits reverse rotation with a constant rotation ratio. 
         [0081]    When the shift-by-wire system is in a failure in which the manual valve  41  is not moved in accordance with the selection operation with the selector lever  21   a  because of, for example, a failure in the selection actuator  42 , or a failure in the shift-by-wire control section  23   a  in  FIG. 4 , the transmission controller  23  detects the failure through a known self-diagnosis, and executes a control program shown in  FIG. 5 . That is, shift-by-wire fail control is performed as follows. 
         [0082]    For the control, as shown in  FIG. 4 , a shift-by-wire fail control section  23   f  may be arranged in the transmission controller  23 . The shift-by-wire fail control section  23   f  performs the self-diagnosis for the failure in the shift-by-wire system, and performs the shift-by-wire fail control in  FIG. 5  when the failure occurs. 
         [0083]    In step S 11  in  FIG. 5 , the transmission controller  23  (shift-by-wire fail control section  23   f ) reads a position signal (selection operation position signal) Dr of the selector lever  21   a , and a current range position signal Tm of the manual valve  41 . 
         [0084]    In step S 12  serving as shift-by-wire fail detecting means, the transmission controller  23  (shift-by-wire fail control section  23   f ) may acquire information from the shift-by-wire control section  23   a  as shown in  FIG. 4 , may perform a self-diagnosis for a failure in the shift-by-wire system (SBW) using the information, and checks whether or not the shift-by-wire system (SBW) has failed. 
         [0085]    If the shift-by-wire system (SBW) has not failed, the shift-by-wire fail control in  FIG. 5  will not be necessary. Thus, the control is ended, and exited from the control program in  FIG. 5 . 
         [0086]    While it is determined that the shift-by-wire system (SBW) is failed in step S 12 , the shift-by-wire fail control in  FIG. 5  is necessary. In step S 13 , it is checked whether or not the manual valve  41  is located correctly at one of range (P, R, N, D) allocation positions on the basis of the current range position signal Tin of the manual valve  41 . 
         [0087]    Here, range (P, R, N, D) allocation positions of the manual valve  41  represent the positions of the manual valve  41  (spool  41   a ), each of which is provided when the detent ball  48  is completely fitted into the valley of corresponding one of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d . If the manual valve  41  is correctly located at one of the range (P, R, N, D) allocation positions, the manual valve  41  achieves the predetermined gear-shift mode for the range position. 
         [0088]    However, if the manual valve  41  is not correctly located at one of the range (P, R, N, D) allocation positions, the detent ball  48  is not completely fitted into one of the valleys of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d , and is located on one of inclined surfaces between the valleys of the triangular cut portions  41   p ,  41   r ,  41   n , and  41   d  as shown in  FIG. 3 . The manual valve  41  does not achieve the predetermined gear-shift mode for the range position. 
         [0089]    Thus, if it is determined that the manual valve  41  is not correctly located at one of the range (P, R, N, D) allocation positions on the basis of the manual valve range position signal Tm in step S 13 , the manual valve  41  may not achieve the predetermined gear-shift mode for the range position. Hence, if the shift-by-wire fail control is performed in this state, an adverse effect is exerted rather than a case in which the control is not performed. Also, the shift-by-wire fail control may be ineffective. In order to prevent these, the control may be ended and exited from the control program in  FIG. 5 . 
         [0090]    If it is determined that the manual valve  41  is correctly located at one of the range (P, R, N, D) allocation positions in step S 13 , the above-mentioned adverse effect is not exerted even when the shift-by-wire fail control is performed, and the shift-by-wire fail control is effective. The control progresses to step S 14 , in which it is checked whether or not the travel range (D, R range) is instructed, on the basis of the selector lever position (selection operation) signal Dr. 
         [0091]    If it is determined that the travel range (D, R range) is not instructed in step S 14 , on the basis of the selector lever position (selection operation) signal Dr, it means that the driver does not want to travel. Thus, the shift-by-wire fail control in  FIG. 5  should not be performed. The control is ended and exited from the control program in  FIG. 5 . 
         [0092]    If it is determined that the travel range (D, R range) is instructed in step S 14 , on the basis of the selector lever position (selection operation) signal Dr, it means that the driver wants to travel. Thus, the control progresses to step S 15 , in which it is checked whether or not the vehicle travel position obtained from the current range position Tm of the manual valve  41  inhibited from being moved due to the failure in the shift-by-wire system mismatches the vehicle travel direction intended by the driver through the selector lever position (selection operation) signal Dr. 
         [0093]    If the vehicle travel direction obtained from the manual-valve range position Tm mismatches the vehicle travel direction intended by the driver through the selector lever position (selection operation) signal Dr in step S 15 , when the vehicle makes the retreat travel for a failure in the shift-by-wire system regardless of the mismatch, the vehicle moves in a direction opposite to the vehicle travel direction intended by the driver, resulting in the driver feeling uncomfortable. Thus, the control progresses to step S 16  serving as transmission output reducing means, in which a fail-safe (FS) process for inhibiting the vehicle from traveling is performed. 
         [0094]    In an exemplary fail-safe (FS) process for inhibiting the vehicle from traveling, the transmission controller  23  (shift-by-wire fail control section  23   f ) transmits ON signals to the forward-pressure-circuit shut-off valve  51  (solenoid  51   b ) and the reverse-pressure-circuit shut-off valve  52  (solenoid  52   b ) through signal paths as shown in  FIGS. 1 and 4 . With these ON signals, the forward clutch pressure Pf and the reverse brake pressure Pr are removed as described with reference to  FIG. 2 . Accordingly, the forward clutch  8  and the reverse brake  9  are disengaged regardless of the range position of the manual valve  41 , and hence, the V-belt continuously variable transmission  2  is in the neutral condition in which power transmission is inhibited. 
         [0095]    In another exemplary fail-safe (FS) process for inhibiting the vehicle from traveling, the transmission controller  23  (shift-by-wire fail control section  23   f ) may transmit signals, which cause the throttle valve opening (TVO) to be fully closed, to the engine controller  16 . With these signals, the output of the engine  1  is set to a lowermost value. 
         [0096]    With any of these fail-safe (FS) processes, the vehicle may be inhibited from traveling. Priority is given to the elimination of the uncomfortable feeling of the driver because the vehicle moves in the direction opposite to the vehicle travel direction intended by the driver, rather than the achievement of the retreat travel for the failure in the shift-by-wire system. 
         [0097]    If the vehicle travel direction obtained from the manual-valve range position Tm matches the vehicle travel direction intended by the driver through the selector lever position (selection operation) signal Dr in step S 15 , even when the vehicle makes the retreat travel for the failure in the shift-by-wire system, the vehicle moves in the same direction as the vehicle travel direction intended by the driver, the control progresses to step S 17  serving as motor output limiting means, in which a limp-home (LH) process is performed for limiting the output of the engine  1  while engine output permitting the vehicle to make the retreat travel by its own power is remained. 
         [0098]    In the limp-home (LH) process for limiting the output of the engine  1  so as to permit the vehicle to make the retreat travel, the transmission controller  23  (shift-by-wire fail control section  23   f ) transmits instructions, which limit a maximum opening of the throttle valve opening (TVO) to an opening capable of achieving the above-mentioned limitation of the engine output (for example, ⅛ opening), to the engine controller  16 . With these instructions, the output of the engine  1  is limited. 
         [0099]    In the limp-home (LH) process, the forward-pressure-circuit shut-off valve  51  (solenoid  51   b ) and the reverse-pressure-circuit shut-off valve  52  (solenoid  52   b ) are held in OFF states. The forward clutch  8  or the reverse brake  9  is engaged depending on the range position of the manual valve  41 , and hence, the V-belt continuously variable transmission  2  is in the condition capable of transmitting the forward rotational power or the condition capable of transmitting the reverse rotational power. 
         [0100]    With the limp-home (LH) process, the vehicle with its shift-by-wire system failed may make the retreat travel from the stop position to a repair shop, driver&#39;s home, or a safe parking lot by its own power. Thus, the problem of the conventional device, in which the vehicle is inhibited from traveling from the stop position, may be solved. 
         [0101]    Because the vehicle travel direction of the retreat travel matches the vehicle travel direction intended by the driver, and because the retreat travel is a low-speed travel under the limitation of the engine output, the driver does not feel uncomfortable, and may make the retreat travel safely. 
         [0102]    With the above-described shift-by-wire fail control of this embodiment, in failure conditions of the shift-by-wire system illustrated as shaded regions in  FIGS. 6 and 7 , although the vehicle is inhibited from traveling due to the fail-safe (FS) process in the prior art, the vehicle may make the retreat travel from the stop position to a repair shop, driver&#39;s home, or a safe parking lot by its own power by the limp-home (LH) process. 
         [0103]    The failure conditions of the shift-by-wire system in cases  1  to  6  shown in  FIGS. 6 and 7  are described as typical examples. 
         [0104]    Case  1  in  FIG. 6  is shift-by-wire fail control performed in a situation that when the driver makes a D-to-R selection operation from the D range to the R range, the manual valve  41  (M/V) is correctly moved from the D range position to the R range position and the V-belt continuously variable transmission  2  (T/M) is shifted from the D range condition to the R range condition, however, after the shift, the manual valve (MN) cannot be moved from the R range position due to a failure in the shift-by-wire system. In the prior art, the vehicle was inhibited from traveling by the fail-safe (FS) process although a vehicle travel direction intended by the D-to-R selection operation by the driver matches a vehicle travel direction caused by setting of the manual valve (MN) at the R range position and the driver does not feel uncomfortable when the vehicle makes the retreat travel. However, in this embodiment, because the limp-home (LH) process is performed, the vehicle may make the retreat travel from the stop position to the safe parking lot by its own power without uncomfortable feeling. 
         [0105]    Case  2  in  FIG. 6  is shift-by-wire fail control performed in a situation that although the driver makes the D-to-R selection operation from the D range to the R range, the manual valve  41  (MN) is not correctly moved from the D range position to the R range position and the V-belt continuously variable transmission  2  (T/M) is held in the D range condition. In this embodiment, with regard to the mismatch between a vehicle travel direction intended by the driver through the D-to-R selection operation and a vehicle travel direction caused by setting of the manual valve (MN) at the D range position, the vehicle is inhibited from traveling by the fail-safe (FS) process. Accordingly, the shift-by-wire fail control may be provided such that priority is given to the elimination of the uncomfortable feeling of the driver resulted from that the vehicle moves in the direction opposite to the vehicle travel direction intended by the driver. 
         [0106]    Case  3  in  FIG. 7  is shift-by-wire fail control performed in a situation that when the driver makes an R-to-D selection operation from the R range to the D range, the manual valve  41  (MN) is correctly moved from the R range position to the D range position and the V-belt continuously variable transmission  2  (T/M) is shifted from the R range condition to the D range condition, however, after the shift, the manual valve (M/V) cannot be moved from the D range position due to a failure in the shift-by-wire system. In the prior art, the vehicle would have been inhibited from traveling by the fail-safe (FS) process although a vehicle travel direction intended by the driver through the R-to-D selection operation matches a vehicle travel direction caused by setting of the manual valve (M/V) at the D range position and the driver does not feel uncomfortable when the vehicle makes the retreat travel. However, in this embodiment, because the limp-home (LH) process is performed, the vehicle may make the retreat travel from the stop position to the safe parking lot by its own power without uncomfortable feeling. 
         [0107]    Case  4  in  FIG. 7  is shift-by-wire fail control performed in a situation that although the driver makes the R-to-D selection operation from the R range to the D range, the manual valve  41  (M/V) is not correctly moved from the R range position to the D range position and the V-belt continuously variable transmission  2  (T/M) is held in the R range condition. In this embodiment, with regard to the mismatch between a vehicle travel direction intended by the driver through the R-to-D selection operation and a vehicle travel direction caused by setting of the manual valve (M/V) at the R range position, the vehicle is inhibited from traveling by the fail-safe (FS) process. Accordingly, the shift-by-wire fail control may be provided such that priority is given to the elimination of the uncomfortable feeling of the driver resulted from that the vehicle moves in the direction opposite to the vehicle travel direction intended by the driver. 
         [0108]    Case  5  in  FIG. 7  is shift-by-wire fail control performed in a situation that when the driver makes an N-to-D selection operation from the N range to the D range, the manual valve  41  (MN) is correctly moved from the N range position to the D range position and the V-belt continuously variable transmission  2  (T/M) is shifted from the N range condition to the D range condition, however, after the shift, the manual valve (MN) cannot be moved from the D range position due to a failure in the shift-by-wire system. In the prior art, the vehicle would have been inhibited from traveling by the fail-safe (FS) process although a vehicle travel direction intended by the driver through the N-to-D selection operation matches a vehicle travel direction caused by setting of the manual valve (MN) at the D range position and the driver does not feel uncomfortable when the vehicle makes the retreat travel. However, in this embodiment, because the limp-home (LH) process is performed, the vehicle may make the retreat travel from the stop position to the safe parking lot by its own power without uncomfortable feeling. 
         [0109]    Case  6  in  FIG. 7  is shift-by-wire fail control performed in a situation that although the driver makes the N-to-D selection operation from the N range to the D range, the manual valve  41  (M/V) is not correctly moved from the N range position to the D range position but is moved to the R range position in a reverse direction and the V-belt continuously variable transmission  2  (T/M) is shifted to the R range condition. In this embodiment, with regard to the mismatch between a vehicle travel direction intended by the driver through the N-to-D selection operation and a vehicle travel direction caused by setting of the manual valve (M/V) at the R range position, the vehicle is inhibited from traveling by the fail-safe (FS) process. Accordingly, the shift-by-wire fail control may be provided such that priority is given to the elimination of the uncomfortable feeling of the driver resulted from that the vehicle moves in the direction opposite to the vehicle travel direction intended by the driver. 
         [0110]    In the illustrated examples, it is described that the automatic transmission is the V-belt continuously variable transmission  2 . However, the concept of the present disclosure may attain similar action and advantage when the automatic transmission is a planetary-gear-set step automatic transmission, an automated manual transmission, or any other transmission mechanism known to those having ordinary skill. 
         [0111]    In the case of the planetary-gear-set step automatic transmission, friction elements for start may include a friction element for selection of a forward first speed and a friction element for selection of a reverse gear position. In the case of the automated manual transmission, friction elements for start include an automatic clutch for selection of a forward first speed and an automatic clutch for selection of a reverse gear position. Thus, in the case of the planetary-gear-set step automatic transmission, shut-off valves  51  and  52  in  FIG. 2  may be inserted into engagement pressure circuits of the friction element for selection of the forward first speed and the friction element for selection of the reverse gear position. In the case of the automated manual transmission, shut-off valves  51  and  52  in  FIG. 2  may be inserted into engagement pressure circuits of the automatic clutch for selection of the forward first speed and the automatic clutch for selection of the reverse gear position. 
         [0112]    Advantageously, embodiments disclosed herein include a shift-by-wire fail control device for a vehicle with an automatic transmission which permits the vehicle to make retreat travel from a stop position by its own power. The shift-by-wire automatic transmission may comprise a vehicle including a manual valve, the manual valve achieving a predetermined gear-shift mode when the manual valve is moved in accordance with a selection operation by a driver under electronic control to a corresponding range position among ranges defining gear-shift modes of the automatic transmission. Also, the vehicle may be capable of traveling by power output from a motor via the automatic transmission. The shift-by-wire control device may include shift-by-wire fail detecting means for detecting a failure in a shift-by-wire system, the failure in which the manual valve is not moved in accordance with the selection operation; and motor output limiting means for limiting the output of the motor within a range permitting retreat travel of the vehicle when the shift-by-wire fail detecting means detects the failure in the shift-by-wire system and if a vehicle travel direction intended by the driver through the selection operation matches a vehicle travel direction obtained from a current range position of the manual valve. 
         [0113]    With this configuration, the vehicle may make the retreat travel from the stop position to a repair shop, driver&#39;s home, or a safe parking lot, by its own power. Thus, the problem of the conventional device, which is the inhibition of the vehicle from traveling from the stop position, may be solved. 
         [0114]    In addition, because the retreat travel may be made when the vehicle travel direction obtained from the current range position of the manual valve inactivated due to the failure matches the vehicle travel direction intended by the driver through the selection operation, the driver does not feel uncomfortable because the vehicle travel direction of the retreat travel matches the intention (vehicle travel direction) by the driver through the selection operation. 
         [0115]    While the disclosure has been presented with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope of the disclosure should be limited only by the attached claims.