Abstract:
A method for allowing a controller of a transmission to learn a reference position of the transmission and a vehicle for which this method can be executed. By the method, when the shift lever is subjected to a predetermined input operation, the controller starts learning a reference position (for example, the gear end, the synchronization end, or the clutch engagement position) of the transmission.

Description:
TECHNICAL FIELD 
     The present invention relates to a method of learning reference positions for a transmission in order to cause a control device of the transmission to learn reference positions for the transmission. The present invention also relates to a vehicle in which such a learning method is carried out. 
     BACKGROUND ART 
     When vehicles are manufactured, it has been the usual practice to produce a plurality of units, which will make up the vehicles, separately in a unit factory, and to assemble the completed units integrally into vehicles in a vehicle assembly factory. Among such units, an automatic transmission is completed when an automatic transmission main body and an electronic control device, which are separately manufactured, are assembled together into a vehicle body. 
     The automatic transmission main body is made up of mechanical components and electric components such as sensors. Since the mechanical components suffer shape variations and the electric components suffer from characteristic variations, it is customary to acquire characteristic values of units to be controlled in an inspection process, and to enter the characteristic values into the control device for achieving a prescribed transmission performance (see U.S. Patent Application Publication No. 2005/0267618). According to U.S. Patent Application Publication No. 2005/0267618, a control facility in the unit factory is electrically connected to an automatic transmission main body, and the control facility controls the automatic transmission main body in order to acquire the characteristic values (see paragraph [0051] of U.S. Patent Application Publication No. 2005/0267618). 
     An automated manual transmission (AMT: Automated Manual Transmission) is made up of units, which operate in a ganged relation in order to automatically change gear positions. With such an automated manual transmission, it is necessary to learn characteristic values (reference positions including a gear end, a synchronous position, a clutch-engaged position, etc.) for the transmission with the units thereof being assembled together in a vehicle (for AMTs, reference should be made to U.S. Patent Application Publication No. 2005/0110449, U.S. Patent Application Publication No. 2005/0230216, and Japanese Laid-Open Patent Publication No. 2005-201394). 
     SUMMARY OF INVENTION 
     For learning characteristic values of a transmission, such as an AMT after units thereof have been assembled in a vehicle body, when the control facility in the unit factory is electrically connected to the transmission, as disclosed in U.S. Patent Application Publication No. 2005/0267618, it is troublesome to install and dismount the transmission, and the control facility suffers locational limitations because the transmission is assembled in the vehicle body. Furthermore, it is necessary to provide the transmission with a connector, which can be connected to the control facility while the transmission is assembled in the vehicle body. Even if a portable tester were connected to the transmission, problems that arise out of installing and dismounting the transmission, and the need to provide the transmission with the connector, still will not be solved. 
     The present invention has been made in view of the aforementioned problems. It is an object of the present invention to provide a method of learning reference positions for a transmission through a simple process, as well as to provide a vehicle that makes use of such a method. 
     According to the present invention, there is provided a method of learning a reference position for a transmission with a control unit of the transmission, comprising the steps of carrying out a process of learning the reference position after the transmission has been assembled in a vehicle body, and starting to learn the reference position in the control unit when an operator makes a prescribed input action on a gear shift command input unit through which a gear shift command is manually entered, in the process of learning the reference position. 
     According to the present invention, when the operator makes a prescribed input action on the gear shift command input unit (e.g., a shift lever) through which a gear shift command is manually entered, the reference position starts to be learned in the control unit. Generally, the gear shift command input unit is positioned so as to be capable of being easily operated by the driver. Therefore, the operator can have the reference position learned through a simple process. As a result, compared with the process of learning a reference position using a control facility in a factory or with a portable tester connected to the vehicle, the man-hours required for the learning process can be reduced, since the transmission does not need to be installed and dismounted. Further, the degree of freedom in design is improved, because it is not necessary for the transmission to have a connector. 
     The gear shift command input unit may comprise a shift lever, wherein the reference position starts to be learned when the shift lever is moved along a prescribed path. Since the shift lever can stop at a plurality of positions, a comparatively large number of paths can be established along which the shift lever is capable of moving. Therefore, when a plurality of reference positions are learned, it is possible to have paths that correspond to the respective learning processes, with the result that the operator can easily distinguish between respective details of the learning processes. 
     The reference position may be prohibited from being learned again when learning of the reference position has ended. Consequently, even though operations of the gear shift command input unit that are used in driving the vehicle are used as the prescribed input action, there is no possibility that the reference position will be rewritten while the driver drives the vehicle. 
     The reference position may be prohibited from being learned again by rewriting a program for learning the reference position after learning of the reference position has ended. Accordingly, the reference position is prevented from being rewritten in error after the reference position has been learned. 
     A display unit for indicating the position of the shift lever may be blinked while the process of learning the reference position is being prepared, the display unit may be turned on when preparation of the process of learning the reference position has ended, the display unit may be blinked while the process of learning the reference position is being performed, and the display unit may be turned on when the process of learning the reference position has ended. Therefore, the progress of the learning processes is indicated to the operator in a simple manner. Since the display unit, which indicates the position of the shift lever, is used to indicate to the operator the progress of the learning processes, the progress of the learning processes can be indicated to the operator without causing the operator to feel any sense of discomfort. 
     At least a first reference position and a second reference position may be learned in the process of learning the reference position, in which case a hand brake may be required to be applied and an ignition switch may be required to be turned on while the shift lever is in a neutral position, as conditions for starting a process of learning the first reference position, and the hand brake and a foot brake may be required to be applied and the ignition switch may be required to be turned on while the shift lever is in the neutral position, as conditions for starting a process of learning the second reference position after the process of learning the first reference position. Therefore, the conditions for starting the process of learning the second reference position are the same as the conditions for starting the process of learning the first reference position, with the additional condition that the foot brake must be applied. Consequently, the operational procedure is not unduly complex, and management of the process is easy to carry out. 
     In the process of learning the first reference position, a gear end may be learned at which gears of the transmission are completely in mesh with each other while an engine is not in operation. In the process of learning the second reference position, a synchronous position may be learned at which the engine and the gears start rotating in synchronism with each other while the engine is in operation. Accordingly, a gear end can be learned while the hand brake is applied to make the vehicle stable, and a synchronous position can be learned while the hand brake and the foot brake are applied, thus making the vehicle more stable. 
     A display unit for indicating the position of the shift lever may be blinked while the process of learning the first reference position and the process of learning the second reference position are being prepared, the display unit may be turned on when preparation of the process of learning the first reference position and the process of learning the second reference position have ended, the display unit may be blinked while the process of learning the first reference position and the process of learning the second reference position are being performed, and the display unit may be turned on when the process of learning the first reference position and the process of learning the second reference position have ended. Further, in the process of learning the second reference position, segments of the display unit that are not used in the process of learning the first reference position may be used. Therefore, the progress of the learning processes is indicated to the operator in a simple manner. Since the display unit, which indicates the position of the shift lever, is used to indicate to the operator the progress of the learning processes, the progress of the learning processes can be indicated to the operator without causing the operator to feel any sense of discomfort. Further, inasmuch as the segments of the display unit, which are not used in the process of learning the first reference position, are used in the process of learning the second reference position, the operator can recognize easily that the process of learning the first reference position has ended. 
     The reference position may start to be learned when the shift lever is moved in order from a neutral position, to a reverse gear position, and to the neutral position. Generally, the operator finds it more difficult to move the shift lever into the reverse gear position than into ordinary drive gear positions, such as a first gear position, a second gear position, etc. For this purpose, the condition of moving the shift lever into the reverse gear position can require the operator to have a higher level of recognition when making the operation. 
     A plurality of reference positions may be learned in the process of learning the reference position. After learning of a first reference position has ended, the first reference position may be prohibited from being learned. Further, an indication may be given that a second reference position should be learned if conditions for starting a process of learning the first reference position are satisfied, even though learning of the first reference position has ended. Consequently, once learning of the first reference position has ended, the first reference position is prohibited from being learned again, so that the first reference position is prevented from being rewritten unintentionally. If a learning process that has already ended is requested, then a next learning process to be performed is indicated to the operator, thereby prompting the operator to carry out the indicated learning process. 
     A vehicle according to the present invention incorporates a program for carrying out the above method of learning the reference position for a transmission. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram of a vehicle according to an embodiment of the present invention; 
         FIG. 2  is a view showing an appearance of a shift lever according to the embodiment; 
         FIG. 3  is a view showing an appearance of a control panel according to the embodiment; 
         FIG. 4  is a flowchart of a process for learning reference positions for a transmission; 
         FIG. 5  is a detailed flowchart of a first portion of a gear end learning process; 
         FIG. 6  is a detailed flowchart of a second portion of the gear end learning process; 
         FIG. 7  is a detailed flowchart of a first portion of a synchronous position learning process; 
         FIG. 8  is a detailed flowchart of a second portion of the synchronous position learning process; 
         FIG. 9  is a detailed flowchart of a third portion of the synchronous position learning process; 
         FIG. 10  is a detailed flowchart of a first portion of a clutch-engaged position learning process; 
         FIG. 11  is a detailed flowchart of a second portion of the clutch-engaged position learning process; 
         FIG. 12  is a detailed flowchart of a third portion of the clutch-engaged position learning process; and 
         FIG. 13  is a flowchart of a process for inhibiting each reference position from being rewritten. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a diagram showing a general arrangement of a vehicle  10  according to an embodiment of the present invention. The vehicle  10  includes a transmission  12 , which principally comprises a clutch  14 , a clutch actuator  16 , a gear mechanism  18 , a gear switching actuator  20  comprising a shift actuator  22  and a select actuator  24 , and a transmission control unit  26  {hereinafter referred to as a “TCU  26 ” (TCU: Transmission Control Unit)}. 
     According to the present embodiment, the above components of the transmission  12  are manufactured as units in a unit factory, and then are assembled into a vehicle body (not shown) of the vehicle  10  in an assembly factory.  FIG. 1  shows the assembled vehicle  10 . 
     The transmission  12  comprises an automated manual transmission (AMT: Automated Manual Transmission). The transmission  12  automatically operates the clutch (engages and disengages the clutch), and shifts gears depending on operations of a shift lever  30  by the driver (manual gear shifting mode). The transmission  12  according to the present embodiment also is capable of automatically operating the clutch and shifting gears without the driver having to operate the shift lever  30  (automatic gear shifting mode). 
     On the vehicle  10 , a drive force Fdr from an engine E is transmitted through the clutch  14  to the gear mechanism  18 . The drive force Fdr, which is transmitted to the gear mechanism  18 , is transmitted through a transmission system  32  to drive wheels  34 . 
     The clutch actuator  16  is connected to the clutch  14  through a hydraulic pressure pipe  36 . The clutch actuator  16  controls clutch operations of the clutch  14  in response to commands (clutch operation signal Scl) from the TCU  26 . The clutch  14  sends a clutch position signal Scp, which is indicative of the position of a pressure plate (not shown) with respect to a flywheel (not shown) of the engine E, to the TCU  26 . 
     The gear mechanism  18  has a plurality of gears, not shown, and is capable of shifting the gears. The gear mechanism  18  also has a plurality of shift forks  40 , to which a shift arm  42  of the gear switching actuator  20  is connected, depending on a selected gear position. The shift arm  42  is caused by the shift actuator  22  to carry out a shifting action (a horizontal movement in  FIG. 1 ), and also is caused by the select actuator  24  to carry out a selecting action (a rotation about the axis of the shift arm  42 ). Based on a command (shifting action signal Ssft) from the TCU  26 , the shift actuator  22  causes the shift arm  42  to carry out the shifting action. The shift actuator  22  detects a distance (shifting distance Asft) [mm] that the shift arm  42  has moved in a shifting direction by means a position sensor (not shown) disposed in the shift actuator  22 , and the shift actuator  22  sends a shifting distance signal Sasft indicative of the shifting distance Asft to the TCU  26 . Based on a command (selecting action signal Ssel) from the TCU  26 , the select actuator  24  causes the shift arm  42  to carry out the selecting action. The select actuator  24  detects a distance (selecting distance Asel) [θ] that the shift arm  42  has moved in a selecting direction by means a position sensor (not shown) disposed in the select actuator  24 , and the select actuator  24  sends a selecting distance signal Sasel indicative of the shifting distance Asel to the TCU  26 . 
     The TCU  26  controls the clutch actuator  16 , the shift actuator  22 , and the select actuator  24  (as described in detail later). A memory  28  is connected to the TCU  26 . The memory  28  stores therein in a rewritable manner a gear end learning program, a synchronous position learning program, and a clutch-engaged position learning program. 
     The transmission  12  is basically constructed and operates as disclosed in U.S. Patent Application Publication No. 2005/0110449, U.S. Patent Application Publication No. 2005/0230216, and Japanese Laid-Open Patent Publication No. 2005-201394, for example. 
     According to the present embodiment, the vehicle  10  also includes an engine rotational speed sensor  50 , an engine torque sensor  52 , and a clutch torque sensor  54 . The engine rotational speed sensor  50  detects a rotational speed [rpm] of the engine E (engine rotational speed NE), and sends an engine rotational speed signal Sne, which is indicative the engine rotational speed NE, to the TCU  26 . The engine torque sensor  52  detects a torque [N] of the engine E (engine torque TQe), and sends an engine torque signal Stqe, which is indicative of the engine torque TQe, to the TCU  26 . The clutch torque sensor  54  detects a torque [N] applied to the clutch  14  (clutch torque TQc), and sends a clutch torque signal Stqc, which is indicative of the clutch torque TQc, to the TCU  26 . 
     According to the present embodiment, the TCU  26  is electrically connected to the shift lever  30 , an ignition switch  60  (hereinafter referred to as an “IGSW  60 ”), a hand brake  62 , a foot brake  64 , a door  66 , a control panel  68 , and a speaker  70 . The shift lever  30  sends a shift lever signal Ssl, which is indicative of a selected gear position, to the TCU  26 . The IGSW  60  sends an ignition signal Sig, which is indicative of an off position, an accessory position, or an on position selected thereby, to the TCU  26 . The hand brake  62  sends a hand brake signal Shd, which is indicative of whether or not the hand brake  62  has been operated, to the TCU  26 . The foot brake  64  sends a foot brake signal Sfb, which is indicative of whether or not the foot brake  64  has been operated, to the TCU  26 . The door  66  sends a door signal Sdo, which is indicative of whether or not the door  66  is open, to the TCU  26 . The control panel  68  displays information depending on a command (display command signal Srd) from the TCU  26 . The speaker  70  outputs a sound (buzzer sound, voice, etc.) depending on a command (sound output command signal Sbz) from the TCU  26 . 
       FIG. 2  shows an appearance of the shift lever  30  according to the present embodiment. As shown in  FIG. 2 , the shift lever  30  is in a position P 1  when the vehicle  10  is driven. Each time that the shift lever  30  is moved toward “+”, the gear mechanism  18  is shifted into a higher gear position. Conversely, each time that the shift lever  30  is moved toward “−”, the gear mechanism  18  is shifted into a lower gear position. Each time the shift lever  30  is moved toward “A/M”, the gear mechanism  18  switches between a manual gear shifting mode and an automatic gear shifting mode. The shift lever  30  can be fixed in the position P 1 , a neutral position P 2 , and a reverse gear position P 3 . However, the shift lever  30  automatically returns to the position P 1  when the shift lever  30  has been moved to “+”, “−”, or “A/M”. 
       FIG. 3  shows an appearance of the control panel  68  according to the present embodiment. As shown in  FIG. 3 , the control panel  68  includes a speed display unit  80 , an engine rotational speed display unit  82 , and a remaining fuel display unit  84 . The control panel  68  also includes, in a region below the remaining fuel display unit  84 , a gear position display unit  86  for displaying a selected gear position, and an automatic gear shifting mode display unit  88  for displaying whether the automatic gear shifting mode has been selected. The automatic gear shifting mode display unit  88  is turned on when the automatic gear shifting mode is selected, and is turned off when the automatic gear shifting mode is not selected. According to the present embodiment, when the TCU  26  learns reference positions for the transmission  12 , the gear position display unit  86  and the automatic gear shifting mode display unit  88  also are used to indicate the progress of the learning process (to be described in detail later). 
       FIG. 4  is a flowchart of a process for learning reference positions for the transmission  12 , components of which are assembled in the vehicle body of the vehicle  10 . 
     In step S 1 , the TCU  26  performs a gear end learning process for learning a gear end for each gear position. The gear end refers to a position in which the shift forks  40  are completely connected to the shift arm  42  and the gears in the gear mechanism  18  are connected (a position in which the shift arm  42  will not move further toward the shift forks  40 , even if the shift actuator  22  and the select actuator  24  are operated under the same conditions). 
     In step S 2 , the TCU  26  performs a synchronous position learning process in order to learn a synchronous position for each gear position. The synchronous position refers to a position in which the shift forks  40  and the shift arm  42  start to come into contact with each other. 
     In step S 3 , the TCU  26  performs a clutch-engaged position learning process in order to learn a clutch-engaged position. The clutch-engaged position refers to a position in which the clutch  14  is connected to the engine E. 
       FIGS. 5 and 6  are detailed flowcharts of the gear end learning process. In step S 11  in  FIG. 5 , the TCU  26  determines whether or not the IGSW  60  is turned on based on an ignition signal Sig from the IGSW  60 . If the IGSW  60  is not turned on (S 11 : No), then the TCU  26  repeats step S 11 . 
     If the IGSW  60  is turned on (S 11 : Yes), then the TCU  26  determines whether or not the TCU  26  is in a power-hold mode. The power-hold mode refers to a mode in which the TCU  26  is continuously turned on for a certain time in order to stop the vehicle  10  after the IGSW  60  has been turned off. The power-hold mode continues if the IGSW  60  is turned off and then immediately turned on. Although not shown in  FIG. 5 , a time period for judging that time-out has occurred for the entire gear end learning process begins to be measured. If, before the process shown in  FIGS. 5 and 6  has ended, the time period becomes equal to or greater than a prescribed threshold value for judging that time-out has occurred, then an error is displayed. If the IGSW  60  is turned off, then control returns to step S 11 . 
     If the TCU  26  is in the power-hold mode in step S 12  (S 12 : Yes), then in step S 13 , the TCU  26  displays on the control panel  68  an error indicating that the TCU  26  is in the power-hold mode, thus prompting the operator to turn off the IGSW  60 . In step S 14 , the TCU  26  determines whether or not the IGSW  60  is turned off based on the ignition signal Sig. If the IGSW  60  remains turned on (S 14 : No), then control returns to step S 13  and the error continues to be displayed. If the IGSW  60  is turned off (S 14 : Yes), then control returns to step S 11 . 
     In step S 12 , if the TCU  26  is not in the power-hold mode (S 12 : No), then in step S 15 , the TCU  26  determines whether or not the hand brake  62  is on and the shift lever  30  is in the neutral position P 2 , based on the hand brake signal Shd from the hand brake  62  and the shift lever signal Ssl from the shift lever  30 . 
     If the hand brake  62  is not on or the shift lever  30  is not in the neutral position P 2  (S 15 : No), then the TCU  26  repeats step S 15 . If the hand brake  62  is on and the shift lever  30  is in the neutral position P 2  (S 15 : Yes), then in step S 16 , the TCU  26  activates the gear end learning program, which is stored in the memory  28 . At this time, the TCU  26  blinks all of the segments of the gear position display unit  86  in order to show that the gear end learning program has been activated. 
     In step S 17  shown in  FIG. 6 , when activation of the gear end learning program is finished, the TCU  26  turns on all of the segments of the gear position display unit  86 . At this time, the TCU  26  starts to measure a time T 1  for judging whether time-out has been reached. 
     In step S 18 , the TCU  26  determines whether or not the shift lever  30  has been moved in order from the neutral position P 2 , to the reverse position P 3 , and to the neutral position P 2 . If the shift lever  30  has not been moved in this order (S 18 : No), then in step S 19 , the TCU  26  determines whether time-out has been reached, i.e., whether the time T 1  is equal to or greater than a threshold value TH_t 1  for judging that time-out has occurred. If time-out has not been reached (S 19 : No), then control returns to step S 18 . If time-out has been reached (S 19 : Yes), then the TCU  26  forcibly ends the gear end learning process, and in step S 20 , displays an error on the control panel  68 , so as to prompt the operator to turn off the IGSW  60 . Then, in step S 21 , the TCU  26  determines whether or not the IGSW  60  has been turned on. If the IGSW  60  remains turned on (S 21 : No), then control returns to step S 20 . If the IGSW  60  has been turned off (S 21 : Yes), then control returns to step S 11 , thus restarting the gear end learning process. 
     In step S 18 , if the shift lever  30  has been moved in order from the neutral position P 2 , to the reverse position P 3 , and to the neutral position P 2  (S 18 : Yes), then in step S 22 , the TCU  26  learns a gear end in each gear position. The TCU  26  learns a gear end by monitoring the shifting distance Asft, which is indicated by the shifting distance signal Sasft from the shift actuator  22 , and the selecting distance Asel, which is indicated by the selecting distance signal Sasel from the select actuator  24 , and by judging as the gear end a point where changes per unit time in the shifting distance Asft and the selecting distance Asel are equal to or smaller than prescribed threshold values. While learning of the gear end is carried out, the TCU  26  blinks all of the segments of the gear position display unit  86 , and also outputs a buzzer sound from the speaker  70 . Alternatively, instead of blinking all of the segments, the TCU  26  may blink a gear position in question. 
     In step S 23 , the TCU  26  determines whether or not learning of a gear end has finished normally. If learning of the gear end has not finished yet (S 23 : No), then in step S 24 , the TCU  26  determines whether or not an error has occurred in learning of the gear end. If an error has not occurred in learning of the gear end (S 24 : No), then control returns to step S 22  and learning of the gear end is continued. If an error has occurred in learning of the gear end (S 24 : Yes), then in step S 25 , the TCU  26  displays the gear position that has suffered an error on the gear position display unit  86 . For example, if a first gear position has suffered an error, then the TCU  26  displays a “1” on the gear position display unit  86 . In step S 26 , the TCU  26  determines whether or not the IGSW  60  has been turned off. If the IGSW  60  remains turned on (S 26 : No), then control returns to step S 25  so that the error continues to be displayed. If the IGSW  60  has been turned off (S 26 : Yes), then control returns to step S 11 . 
     In step S 23 , if learning of the gear end is completed normally (S 23 : Yes), then in step S 27 , the TCU  26  displays that learning of the gear end has been completed on the gear position display unit  86 . More specifically, the TCU  26  displays an “N” on the gear position display unit  86 , and also writes the learned gear end in the memory  28 . In step S 28 , the TCU  26  changes a flag Flg 1 , which is stored in the memory  28  and indicates whether learning of the gear end has been completed, from “0” (indicating that gear end learning is possible) to “1” (indicating that gear end learning is not possible). The flag Flg 1  is included in the gear end learning program. Therefore, the gear end learning program is partially rewritten by changing the value of the flag Flg 1 . In step S 29 , the TCU  26  determines whether or not the IGSW  60  has been turned off. If the IGSW  60  remains turned on (S 29 : No), then control returns to step S 29 . If the IGSW  60  has been turned off (S 29 : Yes), then the gear end learning process is brought to an end, after which control proceeds to step S 2  shown in  FIG. 4 . 
       FIGS. 7 through 9  are detailed flowcharts of the synchronous position learning process. Steps S 31  through S 34  shown in  FIG. 7  are essentially the same as steps S 11  through S 14  shown in  FIG. 5 . Although not shown in  FIG. 7 , if the IGSW  60  has been turned on (S 31 : Yes), then a time period for judging whether time-out has been reached for the entire synchronous position learning process starts to be measured. If, before the process shown in  FIGS. 7 through 9  comes to an end, this time period becomes equal to or greater than a prescribed threshold value for judging that time-out has occurred, then an error is displayed. If the IGSW  60  is turned off, then control returns to step S 31 . 
     If the TCU  26  is not in the power-hold mode in step S 32  (S 32 : No), then the TCU  26  determines, in step S 35 , whether or not the hand brake  62  and the foot brake  64  are both on and the shift lever  30  is in the neutral position P 2 , based on the hand brake signal Shd from the hand brake  62 , the shift lever signal Ssl from the shift lever  30 , and the foot brake signal Sft from the foot brake  64 . If the hand brake  62  or the foot brake  64  is not on, or if the shift lever  30  is not in the neutral position P 2  (S 35 : No), then the TCU  26  repeats step S 35 . 
     If the hand brake  62  and the foot brake  64  are both on and the shift lever  30  is in the neutral position P 2  (S 35 : Yes), then in step S 36 , the TCU  26  activates the synchronous position learning program, which is stored in the memory  28 . At this time, the TCU  26  blinks all of the segments of the gear position display unit  86  as well as the automatic gear shifting mode display unit  88 , in order to show that the synchronous position learning program is currently activated. In step S 37  shown in  FIG. 8 , when activation of the synchronous position learning program is finished, the TCU  26  turns on all of the segments of the gear position display unit  86  and the automatic gear shifting mode display unit  88 . At this time, the TCU  26  starts to measure a time T 2  for judging whether time-out has been reached. 
     Steps S 38  through S 41  are essentially the same as steps S 18  through S 21  shown in  FIG. 6 . For judging that time-out has occurred in step S 39 , the TCU  26  uses a threshold value Th_t 2 . 
     In step S 38 , if the shift lever  30  has been moved in order from the neutral position P 2 , to the reverse position P 3 , and to the neutral position P 2  (S 38 : Yes), then in step S 42 , the TCU  26  learns a neutral position with respect to the shift arm  42 . The TCU  26  learns the neutral position, for example, by moving the shift arm  42  to a minimum value in the shifting direction (i.e., to a position most widely spaced from the shift forks  40 ) and to a minimum value or a maximum value in the selecting direction (i.e., to a position at which the shift arm  42  is moved as far as possible in the selecting direction), and by defining as the neutral position the position to which the shift arm  42  has been moved from the above position by prescribed distances in the shifting direction and the selecting direction. While learning the neutral position is carried out, the TCU  26  blinks all of the segments of the gear position display unit  86 , and also outputs a buzzer sound from the speaker  70 . When learning of the neutral position is finished in step S 43 , the TCU  26  stops outputting the buzzer sound, and turns on all of the segments of the gear position display unit  86 . At this time, the TCU  26  starts to measure a time T 3  for judging whether time-out has been reached. 
     In step S 44 , the TCU  26  determines whether or not the engine E has been started (by the operator operating the IGSW  60 ), based on an output signal from the engine rotational speed sensor  50  or the engine torque sensor  52 . If the engine E has not been started (S 44 : No), then control proceeds step S 45 . Step S 45  as well as steps S 46  and S 47  is the same as steps S 39  through S 41  shown in  FIG. 8 . For judging that time-out has occurred in step S 45 , the TCU  26  uses a threshold value Th_t 3 . 
     In step S 44 , if the engine E has been started (S 44 : Yes), then control proceeds step S 48 . Also, if the engine E has been started in step S 44 , the TCU  26  starts measuring a time T 4  for judging whether time-out has been reached. Step S 48  and steps S 49  through S 51  are the same as steps S 38  through S 41  shown in  FIG. 8 . For judging whether time-out has been reached in step S 49 , the TCU  26  uses a threshold value Th_t 4 . 
     In step S 48 , if the shift lever  30  has been moved in order from the neutral position P 2 , to the reverse position P 3 , and to the neutral position P 2  (S 48 : Yes), then in step S 52  shown in  FIG. 9 , the TCU  26  learns a synchronous position for each gear position. The TCU  26  learns a synchronous position, for example, by moving the shift arm  42  in the shifting direction and the selecting direction for each gear position, and judging as a synchronous position a position determined from the shifting distance signal Sasft, at a time that the engine torque TQe detected by the engine torque sensor  52  undergoes a prescribed change (reduction). While learning the synchronous position, the TCU  26  blinks all of the segments of the gear position display unit  86 , and also outputs a buzzer sound from the speaker  70 . 
     In step S 53 , the TCU  26  determines whether or not learning of a synchronous position has finished normally. If learning of the synchronous position is not finished yet (S 53 : No), then in step S 54 , the TCU  26  determines whether or not an error has occurred during learning of the synchronous position. If an error has not occurred during learning of the synchronous position (S 54 : No), then control returns to step S 52 , and learning of the synchronous position is continued. If an error has occurred during learning of the synchronous position (S 54 : Yes), then in step S 55 , the TCU  26  displays the gear position that has suffered an error on the gear position display unit  86 . For example, if a second gear position has suffered an error, then the TCU  26  displays a “2” on the gear position display unit  86 . In step S 56 , the TCU  26  determines whether or not the IGSW  60  has been turned off. If the IGSW  60  remains turned on (S 56 : No), then control returns to step S 55  in order to keep displaying the error. If the IGSW  60  has been turned off (S 56 : Yes), then control returns to step S 31 . 
     In step S 53 , if learning of the synchronous position is finished normally (S 53 : Yes), then in step S 57 , the TCU  26  displays that learning of the synchronous position has been completed on the gear position display unit  86 . More specifically, the TCU  26  displays an “N” on the gear position display unit  86 , and also writes the learned synchronous position in the memory  28 . In step S 58 , the TCU  26  changes a flag Flg 2 , which is stored in the memory  28  and which indicates whether learning of the synchronous position is finished, from “0” (indicating that synchronous position learning is possible) to “1” (indicating that synchronous position learning is not possible). The flag Flg 2  is included in the synchronous position learning program. Therefore, the synchronous position learning program is partially rewritten by changing the value of the flag Flg 2 . In step S 59 , the TCU  26  determines whether or not the IGSW  60  has been turned off. If the IGSW  60  remains turned on (S 59 : No), then the TCU  26  repeats step S 59 . If the IGSW  60  has been turned off (S 59 : Yes), then the synchronous position learning process is brought to an end, after which control proceeds to step S 3  shown in  FIG. 4 . 
       FIGS. 10 through 12  are detailed flowcharts of the clutch-engaged position learning process. Steps S 61  through S 64  shown in  FIG. 10  are essentially the same as steps S 11  through S 14  shown in  FIG. 5 . Although not shown in  FIG. 10 , if the IGSW  60  is turned on (S 61 : Yes), then a time period for judging whether time-out has been reached for the entire clutch-engaged position learning process starts to be measured. If, before the process shown in  FIGS. 10 through 12  is brought to an end, this time period becomes equal to or greater than a prescribed threshold value for judging that time-out has occurred, then an error is displayed. If the IGSW  60  is turned off, then control returns to step S 61 . 
     If the TCU  26  is not in the power-hold mode in step S 62  (S 62 : No), then the TCU  26  determines, in step S 65 , whether or not the hand brake  62  and the foot brake  64  are both on, the shift lever  30  is in the neutral position P 2 , and the door  66  is open, based on the hand brake signal Shd from the hand brake  62 , the shift lever signal Ssl from the shift lever  30 , the foot brake signal Sft from the foot brake  64 , and the door signal Sdo from the door  66 . If the hand brake  62  or the foot brake  64  is not on, if the shift lever  30  is not in the neutral position P 2 , or if the door  66  is closed (S 65 : No), then the TCU  26  repeats step S 65 . 
     If the hand brake  62  and the foot brake  64  are both on, the shift lever  30  is in the neutral position P 2 , and the door  66  is open (S 65 : Yes), then in step S 66 , the TCU  26  activates the clutch-engaged position learning program, which is stored in the memory  28 . At this time, the TCU  26  blinks all of the segments of the gear position display unit  86 , in order to show that the clutch-engaged position learning program is currently activated. In step S 67  shown in  FIG. 11 , when activation of the clutch-engaged position learning program is finished, the TCU  26  turns on all of the segments of the gear position display unit  86 . At this time, the TCU  26  starts to measure a time T 5  for judging whether time-out has been reached. 
     Steps S 68  through S 71  are essentially the same as steps S 18  through S 21  shown in  FIG. 6 . For judging that time-out has occurred in step S 69 , the TCU  26  uses a threshold value Th_t 5 . 
     In step S 68 , if the shift lever  30  has been moved in order from the neutral position P 2 , to the reverse position P 3 , and to the neutral position P 2  (S 68 : Yes), then in step S 72 , the TCU  26  performs a refilling process. The refilling process refers to a process for opening the piston of a hydraulic cylinder in order to cancel the hydraulic pressure (remaining pressure) therein. During the refilling process, the TCU  26  blinks all of the segments of the gear position display unit  86 , and also outputs a buzzer sound from the speaker  70 . When the refilling process is finished in step S 73 , the TCU  26  stops outputting the buzzer sound and displays an “N” on the gear position display unit  86 . At this time, the TCU  26  starts to measure a time T 6  for judging whether time-out has been reached. 
     In step S 74 , the TCU  26  determines whether or not the engine E has been started (by the operator operating the IGSW  60 ), based on an output signal from the engine rotational speed sensor  50  or the engine torque sensor  52 . 
     If the engine E has not been started (S 74 : No), then control proceeds to step S 75 . Step S 75  as well as steps S 76  and S 77  is the same as steps S 45  through S 47  shown in  FIG. 8 . For judging whether time-out has occurred in step S 75 , the TCU  26  uses a threshold value Th_t 6 . 
     In step S 74 , if the engine E has been started (S 74 : Yes), then in step S 78 , the TCU  26  blinks all of the segments of the gear position display unit  86  for a prescribed startup time after the engine E has been started and until rotation of the engine E is stabilized. Upon elapse of the prescribed startup time, the TCU  26  turns on all of the segments of the gear position display unit  86  in step S 79 . At this time, the TCU  26  starts to measure a time T 7  for judging whether time-out has been reached. 
     In step S 80 , the TCU  26  determines whether the shift lever  30  has been moved from the neutral position P 2  to the position A/M. If the TCU  26  judges that the shift lever  30  has not been so moved (S 80 : No), then control proceeds to step S 81 . Step S 81  as well as steps S 82  and S 83  is the same as steps S 69  through S 71  shown in  FIG. 11 . For judging whether time-out has occurred in step S 81 , the TCU  26  uses a threshold value Th_t 7 . 
     In step S 80 , if the shift lever  30  has been moved from the neutral position P 2  to the position A/M (S 80 : Yes), then in step S 84  shown in  FIG. 12 , the TCU  26  learns a clutch-engaged position. The TCU  26  learns the clutch-engaged position, for example, by judging as a clutch-engaged position a position that is indicated by the clutch position signal Scp at a time when the clutch torque TQc detected by the clutch torque sensor  54  undergoes a prescribed change (increase). While learning the clutch-engaged position, the TCU  26  blinks all of the segments of the gear position display unit  86 , and also outputs a buzzer sound from the speaker  70 . 
     In step S 85 , the TCU  26  determines whether or not learning of a clutch-engaged position has finished normally. If learning of the clutch-engaged position is not finished yet (S 85 : No), then in step S 86 , the TCU  26  determines whether or not an error has occurred during learning of the clutch-engaged position. If an error has not occurred during learning of the clutch-engaged position (S 86 : No), then control returns to step S 84 , and learning of the clutch-engaged position is continued. If an error has occurred during learning of the clutch-engaged position (S 86 : Yes), then in step S 87 , the TCU  26  turns on the automatic gear shifting mode display unit  88  and displays a “5” on the gear position display unit  86 . In step S 88 , the TCU  26  determines whether or not the IGSW  60  has been turned off. If the IGSW  60  remains turned on (S 88 : No), then control returns to step S 87  in order to keep displaying the error. If the IGSW  60  has been turned off (S 88 : Yes), then control returns to step S 61 . 
     In step S 85 , if learning of the clutch-engaged position is finished normally (S 85 : Yes), then in step S 89 , the TCU  26  displays that learning of the clutch-engaged position has been completed on the gear position display unit  86 . More specifically, the TCU  26  turns on the automatic gear shifting mode display unit  88  and displays a “1” on the gear position display unit  86 . The TCU  26  also writes the learned clutch-engaged position in the memory  28 . In step S 90 , the TCU  26  determines whether or not the shift lever  30  has been changed from the position A/M to the neutral position P 2 . If the shift lever  30  remains in the position A/M (S 90 : No), then control returns to step S 89 . If the shift lever  30  has been changed from the position A/M to the neutral position P 2  (S 90 : Yes), then the TCU  26  changes a flag Flg 3 , which is stored in the memory  28  and which indicates whether learning of the clutch-engaged position is finished, from “0” (indicating that clutch-engaged position learning is possible) to “1” (indicating that clutch-engaged position learning is not possible). The flag Flg 3  is included in the clutch-engaged position learning program. Therefore, the clutch-engaged position learning program is partially rewritten by changing the value of the flag Flg 3 . In step S 92 , the TCU  26  determines whether or not the IGSW  60  has been turned off. If the IGSW  60  remains turned on (S 92 : No), then the TCU  26  repeats step S 92 . If the IGSW  60  has been turned off (S 92 : Yes), then the clutch-engaged position learning process is brought to an end, and hence the process shown in  FIG. 4  also is brought to an end. 
       FIG. 13  is a flowchart of a process for inhibiting a gear end, a synchronous position, and a clutch-engaged position from being rewritten. 
     In step S 101 , the TCU  26  determines whether or not conditions (S 11 , S 12 , S 15  in  FIG. 5 ) for starting the gear end learning process are satisfied. If the starting conditions are not satisfied (S 101 : No), then the process is terminated. If the starting conditions are satisfied (S 101 : Yes), then control proceeds to step S 102 . 
     In step S 102 , the TCU  26  determines whether or not the gear end learning process has ended (whether the flag Flg 1 =1). If the gear end learning process has not ended (S 102 : No), then the TCU  26  continues to perform the gear end learning process in step S 103 . If the gear end learning process has ended (S 102 : Yes), then the TCU  26  does not perform a new gear end learning process, and control proceeds to step S 104 . 
     In step S 104 , the TCU  26  determines whether or not conditions (S 31 , S 32 , S 35  in  FIG. 7 ) for starting the synchronous position learning process are satisfied. If the starting conditions are not satisfied (S 104 : No), then in step S 105 , the TCU  26  indicates that the synchronous position learning process is not yet completed via the control panel  68  and the speaker  70 . If the starting conditions are satisfied (S 104 : Yes), then control proceeds to step S 106 . 
     In step S 106 , the TCU  26  determines whether or not the synchronous position learning process has ended (whether the flag Flg 2 =1). If the synchronous position learning process has not ended (S 106 : No), then in step S 107 , the TCU  26  continues to perform the synchronous position learning process. If the synchronous position learning process has ended (S 106 : Yes), then the TCU  26  does not perform a new synchronous position learning process, and control proceeds to step S 108 . 
     In step S 108 , the TCU  26  determines whether or not conditions (S 61 , S 62 , S 65  in  FIG. 10 ) for starting the clutch-engaged position learning process are satisfied. If the starting conditions are not satisfied (S 108 : No), then in step S 109 , the TCU  26  indicates that the clutch-engaged position learning process is not yet completed via the control panel  68  and the speaker  70 . If the starting conditions are satisfied (S 108 : Yes), then control proceeds to step S 110 . 
     In step S 110 , the TCU  26  determines whether or not the clutch-engaged position learning process has ended (whether the flag Flg 3 =1). If the clutch-engaged position learning process is not ended (S 110 : No), then in step S 110 , the TCU  26  continues to perform the clutch-engaged position learning process. If the clutch-engaged position learning process has ended (S 110 : Yes), then the TCU  26  does not perform a new clutch-engaged position learning process, and the process shown in  FIG. 13  is brought to an end. 
     According to the present embodiment, as described above, when the operator performs a prescribed input action on the shift lever  30 , the TCU  26  starts learning a gear end, a synchronous position, and a clutch-engaged position, respectively. Generally, the shift lever  30  is positioned where the driver can easily operate the shift lever  30 . Therefore, the operator can enable the gear end, the synchronous position, and the clutch-engaged position to be learned through a simple process. As a result, compared with the process of learning a gear end, etc., with a control facility in a factory, or by means of a portable tester connected to the vehicle  10 , the man-hours required for the learning process can be reduced since the transmission does not need to be installed and dismounted. Further, the degree of freedom in design is improved, because it unnecessary for the transmission  12  to have a connector. 
     According to the present embodiment, when the shift lever  30  is moved along a prescribed path (S 18 : Yes in  FIG. 6 , S 48 : Yes in  FIG. 8 , S 80 : Yes in  FIG. 11 ), the TCU  26  starts learning a gear end, a synchronous position, and a clutch-engaged position (S 22  in  FIG. 6 , S 52  in  FIG. 9 , S 84  in  FIG. 12 ). Since the shift lever can stop at a plurality of positions, a relatively large number of paths along which the shift lever  30  may move can be established. Therefore, when a plurality of reference positions (a gear end, a synchronous position, and a clutch-engaged position) are to be learned, it is possible to have paths corresponding to the respective learning processes, with the result that the operator can easily distinguish between respective details of the learning processes. 
     According to the present embodiment, after a gear end, etc., has been learned, i.e. when learning thereof has ended, the gear end is prohibited from being learned again. Consequently, even though operations of the shift lever  30 , which are used during driving the vehicle, are used as conditions for starting the learning processes, there is no possibility that the gear end, etc., will be rewritten while the driver is actually driving the vehicle. 
     According to the present embodiment, a gear end, etc., is prohibited from being learned again by rewriting the gear end learning program, the synchronous position learning program, and the clutch-engaged position learning program, after the learning processes thereof have come to an end. Accordingly, after having been learned, the gear end, the synchronous position, and the clutch-engaged position are prevented from being rewritten in error. 
     According to the present embodiment, the gear end learning process is started based on the condition that the hand brake  62  is on, and that the IGSW  60  is turned on while the shift lever  30  is in the neutral position P 2  (S 11 : Yes and S 15 : Yes in  FIG. 5 ). The synchronous position learning process is started based on the condition that the hand brake  62  and the foot brake  64  are on, and that the IGSW  60  is turned on while the shift lever  30  is in the neutral position P 2  (S 31 : Yes and S 35 : Yes in  FIG. 7 ). Therefore, conditions for starting the synchronous position learning process are the same as the conditions for starting the gear end learning process, with the additional condition that the foot brake  64  must be applied. Consequently, the operational procedure is not unduly complex, and management of the process is easy. 
     In the gear end learning process according to the present embodiment, a gear end is learned while the engine E is not in operation. In the synchronous position learning process, a synchronous position is learned while the engine E is in operation. Accordingly, a gear end can be learned while the hand brake  62  is applied to maintain the vehicle  10  in a stable condition, and a synchronous position can be learned while the hand brake  62  and the foot brake  64  are applied, thus making the vehicle  10  more stable. 
     While the gear end learning process, the synchronous position learning process, and the clutch-engaged position learning process according to the present embodiment are being prepared, the gear position display unit  86  is blinked. When preparations for the learning processes are brought to an end, the gear position display unit  86  is turned on. While the learning processes are being performed, the gear position display unit  86  is blinked. When the learning processes are brought to an end, the gear position display unit  86  is turned on. In the synchronous position learning process, the automatic gear shifting mode display unit  88  as well as the gear position display unit  86  is blinked and turned on. In the synchronous position learning process, the automatic gear shifting mode display unit  88  as well as the gear position display unit  86  is blinked and turned on. Therefore, the progress of each of the learning processes is indicated to the operator in a simple manner. Since the gear position display unit  86  and the automatic gear shifting mode display unit  88  are used to indicate the progress of the learning processes to the operator, the progress of the learning processes is indicated to the operator without causing the operator to feel any sense of discomfort. In the synchronous position learning process, since the automatic gear shifting mode display unit  88  as well as the gear position display unit  86  is blinked and turned on, the operator can recognize that the gear end learning process has ended. 
     According to the present embodiment, a gear end or a synchronous position starts to be learned (S 22  in  FIG. 6  and S 52  in  FIG. 9 ) when the shift lever  30  is moved in order from the neutral position P 2 , to the reverse position P 3 , and to the neutral position P 2  (S 18 : Yes in  FIG. 6  and S 48 : Yes in  FIG. 8 ). Generally, the operator finds it more difficult to move the shift lever  30  into the reverse gear position P 3  than into ordinary drive gear positions, such as the first gear position, the second gear position, etc. Accordingly, the condition of moving the shift lever  30  into the reverse gear position P 3  requires the operator to perform the operation with a higher level of recognition. 
     According to the present embodiment, after learning of the gear end has ended, the gear end is prohibited from being relearned, and if the conditions for starting the gear end learning process are satisfied, even though learning of the gear end has ended, then it is indicated that a synchronous position should be learned (S 105  in  FIG. 13 ). After the learning of the synchronous position has ended, a synchronous position is prohibited from being relearned, and if the conditions for starting the synchronous position learning process are satisfied, even though learning of the synchronous position has ended, then it is indicated that a clutch-engaged position should be learned (S 109  in  FIG. 13 ). Consequently, once learning of the gear end or the synchronous position has ended, the gear end or the synchronous position is prohibited from being learned again, so that the gear end or the synchronous position, which has already been learned, is prevented from being rewritten unintentionally. If a learning process, which has already ended, is requested, then a next learning process to be performed is indicated to the operator, thereby prompting the operator to carry out the learning process. 
     The present invention is not limited to the above embodiment, but may employ various other arrangements based on the content of the present description. For example, the present invention may employ the following arrangements. 
     In the above embodiment, a gear end, a synchronous position, and a clutch-engaged position are used as reference positions for the transmission  12 . However, either one or two of the above positions may be used. Other reference positions may be used as well. 
     In the above embodiment, the shift lever  30  is used as a device for manually entering a gear shift command. Instead, a paddle shift, for example, may be used. The number of times that the paddle shift is pushed may be used as a condition for starting the learning process. 
     In the above embodiment, the shift lever  30  is moved in order from the neutral position P 2 , to the reverse position P 3 , and to the neutral position P 2 , so as to satisfy the conditions for starting the gear end learning process. However, the present invention is not limited to these conditions. Similarly, the present invention is not limited to the conditions described above for starting the other reference position learning processes.