Abstract:
A shift control apparatus for an automatic transmission includes a pre-shift device that operates a predetermined synchromesh, based on a prediction by a predicting device. It thereby couples together a transmission input shaft (with a friction transfer mechanism that has not been used to effect a current gear position) and a transmission output shaft, through a predetermined gear train, and brings them into a standby state. The time when it is determined that the friction transfer mechanism that has not been used to effect of the current gear position has been disengaged is taken as the timing with which the synchromesh coupling operation by the standby control is started, regardless of the completion of the achievement of the current gear position.

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese patent application serial no. 2007-204867 filed on Aug. 7, 2007, the contents of which are hereby incorporated by reference into this application. 
     FIELD OF THE INVENTION 
     The present invention relates to an apparatus and control method for controlling an automatic transmission particularly a gear type automatic transmission used in an automobile. 
     BACKGROUND OF THE INVENTION 
     In recent years, an automated manual transmission (hereafter, abbreviated as “automated MT”) has been developed in an automobile technical field. This is a system used for automating operation of a clutch configured with a friction mechanism and operation of a synchromesh as a gear change mechanism in a gear type transmission which originally used to be used as a manual transmission. In the automated MT, when shifting is started, a clutch for transferring/interrupting torque of an engine as a driving force source is disengaged and a synchromesh is switched, and then the clutch is engaged again. 
     In JP-A-2000-234654 and JP-A-2001-295898, twin-clutch automated MTs are disclosed; the twin-clutch automated MT has two clutches for transferring input torque to a transmission and drive torque is alternately transferred by the two clutches. In the twin-clutch automated MT, when shifting is started, a first clutch that has been transferring torque before the shifting, is gradually disengaged, and a second clutch for the next gear position is gradually engaged; and drive torque is changed from the one equivalent to the current gear ratio to the one equivalent to the next gear ratio. As a result, interruption of the drive torque is avoided and smooth shifting can be achieved. 
     With respect to the above-mentioned twin-clutch automated MT, a so-called pre-shift control is disclosed in JP-A-10-318361 and JP-A-2003-269592. The pre-shift control is carried out to shorten a time required for shifting to the next gear position. That is, the pre-shift control is done such that, when a gear position is in some position, a next gear position is predicted; a transmission input shaft whose clutch has not been used for a current gear position is selectively coupled to a transmission output shaft by a synchromesh and they are thereby allowed to stand by in the next gear position. 
     The pre-shift control where the gear position is pre-shifted to the next position makes it possible to enhance a response for gear shifting when the prediction comes true. However, provided that a driver&#39;s request shift operation is done by the driver during the pre-shift control for the next shifting, an operation of the synchromesh according to the driver&#39;s request shift must be started after the pre-shift control is achieved. And then, when the operation of the synchromesh is completed, the clutch to clutch shift in engagement is started. As a result, the response is degraded. 
     The invention is to provide a control apparatus for twin-clutch automatic transmissions possible to advance start timing of pre-shift control and enhance the response when a shifting request continuously occurs. 
     SUMMARY OF THE INVENTION 
     The invention to achieve the above object is configured as follows. A shift control apparatus for automatic transmissions is comprised of: plural friction transfer mechanisms (for example, clutches) for transferring power of a driving force source and interrupting this transfer; plural transmission input shafts respectively coupled with the friction transfer mechanisms; and plural gear trains for selectively coupling together the transmission input shafts and a transmission output shaft by the selecting operation of plural synchromeshes. 
     Furthermore, the shift control apparatus is configured such that: a desired gear position is achieved by coupling together the transmission input shaft with which one friction transfer mechanism is coupled and the transmission output shaft through a gear train and engaging the one friction transfer mechanism and disengaging the other friction transfer mechanism; and 
     standby control is carried out by predicting a next gear position and operating a predetermined synchromesh based on a result of the prediction to couple together the transmission input shaft with which the friction transfer mechanism having not been used for the achievement of the desired gear position is coupled and the transmission output shaft through a predetermined gear train and bring the transmission input shaft and the transmission output shaft into standby state. 
     Furthermore, the shift control device apparatus is configured so as to carry out timing with which operation for synchromesh coupling by the standby control is started, under condition of determining that the friction transfer mechanism having not been used for achievement of the desired gear position has been disengaged regardless of completion of the achievement of the desired gear position. 
     According to the invention, pre-shift operation is started when it is determined that the disengagement of the clutch on standby has been completed even during shifting. 
     Therefore, the timing of start of pre-shift control can be advanced, and thus the response can be enhanced when a shifting request continuously occurs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a skeleton diagram illustrating the configuration of an automatic transmission in an embodiment of the invention; 
         FIG. 2  is a block diagram illustrating a relation of input/output signals of a transmission control unit  100  and an engine control unit  101  used in a control apparatus for automatic transmissions in an embodiment of the invention; 
         FIG. 3  is a flowchart illustrating an outline of the details of control by the control apparatus for automatic transmissions in an embodiment of the invention; 
         FIG. 4  is a flowchart illustrating the details of the engagement permission determination processing for a standby gear illustrated in  FIG. 3 ; 
         FIG. 5  is a time diagram illustrating an example of first pre-shift control by the control apparatus for automatic transmissions in an embodiment of the invention; 
         FIG. 6  is a time diagram illustrating an example of second pre-shift control by the control apparatus for automatic transmissions in an embodiment of the invention; and 
         FIG. 7  is a time diagram illustrating an example of third pre-shift control by the control apparatus for automatic transmissions in an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereafter, detailed description will be given to embodiments of the invention with reference to  FIG. 1  to  FIG. 6 . 
     First, description will be given to an example of the configuration of a control apparatus for automobiles of the invention having an automatic transmission with reference to  FIG. 1 . 
       FIG. 1  is a skeleton diagram of an example of the configuration of a system, illustrating a control apparatus for automobiles of the invention having an automatic transmission in an embodiment. 
     An automobile is provided with an engine  7  as a driving force source, an engine speed sensor (not shown) for measuring a speed of the engine  7 , an electronic throttle (not shown) for controlling engine torque, and a fuel injection system (not shown) for injecting a quantity of fuel appropriate to an intake air flow rate. The intake air flow rate, fuel quantity, ignition timing, and the like are controlled by an engine control unit  101 , and the torque of the engine  7  can be thereby accurately controlled. There are different types of the fuel injection system, for example, an inlet port injection type in which fuel is injected toward an inlet port and a direct injection type in which fuel is directly injected into a cylinder. It is advantageous to use an engine of such a type that fuel consumption can be reduced and favorable exhaust performance can be obtained by comparing the operating ranges (range determined by engine torque and engine speed) required of both types-engine. The driving force source need not be a gasoline engine and any of a diesel engine, a natural gas engine, an electric motor, and the like can be used for this purpose. 
     An automatic transmission  50  is provided with a first clutch  8 , a second clutch  9 , a first input shaft  41 , a second input shaft  42 , an output shaft  43 , a first drive gear  1 , a second drive gear  2 , a third drive gear  3 , a fourth drive gear  4 , a fifth drive gear  5 , a reverse drive gear (not shown), a first driven gear  11 , a second driven gear  12 , a third driven gear  13 , a fourth driven gear  14 , a fifth driven gear  15 , a reverse driven gear (not shown), a first synchromesh  21 , a second synchromesh  22 , a third synchromesh  23 , a rotation sensor  31 , a rotation sensor  32 , and a rotation sensor  33 . Torque of the engine  7  can be transferred to the first input shaft  41  and this transfer can be interrupted, by engaging or disengaging the first clutch  8 . The torque of the engine  7  can be transferred to the second input shaft  42  and this transfer can be interrupted, by engaging or disengaging the second clutch  9 . In the example, a multiple wet clutch is used for the first clutch  8  and the second clutch  9 . Instead, a single dry clutch may be used, and any types of friction transfer mechanism can be used. They can also be constructed of electromagnetic powder clutches. 
     The second input shaft  42  is comprised of a hollow-shaft. The first input shaft  41  is inserted through the second input shaft  42  and can be moved freely relative to the second input shaft  42  in a direction of rotation. 
     The first drive gear  1 , third drive gear  3 , fifth drive gear  5  and reverse drive gear (not shown) are fixed on the second input shaft  42 , and can be freely rotated relative to the first input shaft  41 . The second drive gear  2  and fourth drive gear  4  are fixed on the first input shaft  41 , and can be moved freely relative to the second input shaft  42  in the direction of rotation. 
     The sensor  31  is to sense a rotational speed of the first input shaft  41 , and the sensor  32  is to sense a rotational speed of the second input shaft  42 . 
     The output shaft  43  is provided with the first driven gear  11 , second driven gear  12 , third driven gear  13 , fourth driven gear  14 , fifth driven gear  15 , and reverse driven gear (not shown). The first driven gear  11 , second driven gear  12 , third driven gear  13 , fourth driven gear  14 , fifth driven gear  15 , and reverse driven gear (not shown) are provided such that they can be freely rotated relative to the output shaft  43 . 
     The sensor  33  is to sense a rotational speed of the output shaft  43 . 
     Of these gears, the first drive gear  1  is meshed with the first driven gear  11  and the second drive gear  2  is meshed with the second driven gear  12 . Further, the third drive gear  3  is meshed with the third driven gear  13  and the fourth drive gear  4  is meshed with the fourth driven gear  14 . Furthermore, the fifth drive gear  5  is meshed with the fifth driven gear  15 . The reverse drive gear (not shown), an idler gear (not shown), and the reverse driven gear (not shown) are engaged with each other. 
     The first synchromesh  21  is provided between the first driven gear  11  and the third driven gear  13  to selectively allow the first driven gear  11  to engage with the output shaft  43  or allow the third driven gear  13  to engage with the output shaft  43 . 
     The third synchromesh  23  is provided between the second driven gear  12  and the fourth driven gear  14  to selectively allow the second drive gear  12  to engage with the output shaft  43  and allow the fourth driven gear  14  to engage with the output shaft  43 . 
     The second synchromesh  22  is provided to allow the fifth driven gear  15  to engage with the output shaft  43 . 
     Currents of an electromagnetic valve  105   c  and an electromagnetic valve  105   d  provided in hydraulic equipment  105  are controlled by a transmission control unit  100 . A position or load of the first synchromesh  21  is thereby controlled through a hydraulic piston (not shown) and a shift fork (not shown) provided in a shift actuator  61 . The first driven gear  11  or the third driven gear  13  is thereby allowed to engage with the output shaft  43 . As a result, torque of the second input shaft  42  can be transferred to the output shaft  43  through the first drive gear  1 , the first driven gear  11  and the first synchromesh  21  or through the second drive gear  3 , the second driven gear  13  and the first synchromesh gear  21 . For example, provided that the current of the electromagnetic valve  105   d  is increased, a load is applied in such a direction that the first synchromesh  21  is moved toward the first driven gear  11 ; and provided that the current of the electromagnetic valve  105   c  is increased, a load is applied in such a direction that the first synchromesh  21  is moved toward the third driven gear  13 . The shift actuator  61  is provided with a position sensor  61   a  (not shown) for measuring the position of the first synchromesh  21 . 
     Currents of an electromagnetic valve  105   e  and an electromagnetic valve  105   f  provided in the hydraulic equipment  105  are controlled by the transmission control unit  100 . A position or load of the second synchromesh  22  is thereby controlled through a hydraulic piston (not shown) and a shift fork (not shown) provided in a shift actuator  62 . The fifth driven gear  15  is thereby allowed to engage with the output shaft  43 . As a result, torque of the second input shaft  42  can be transferred to the output shaft  43  through the fifth drive gear  5 , the fifth driven gear, and the second synchromesh  22 . The shift actuator  62  is provided with a position sensor  62   a  (not shown) for measuring the position of the second synchromesh  22 . 
     Currents of an electromagnetic valve  105   g  and an electromagnetic valve  105   h  provided in the hydraulic equipment  105  are controlled by the transmission control unit  100 . A position or load of the third synchromesh  23  is thereby controlled through a hydraulic piston (not shown) and a shift fork (not shown) provided in a shift actuator  63 . The second driven gear  12  or the fourth driven gear  14  is thereby allowed to engage with the output shaft  43 . As a result, torque of the first input shaft  41  can be transferred to the output shaft  43  through the second drive gear  2 , the second driven gear  12  and the third synchromesh  23  or the fourth drive gear  4 , the fourth driven gear  14  and the third synchromesh  23 . The shift actuator  63  is provided with a position sensor  63   a  (not shown) for measuring the position of the third synchromesh  23 . 
     As mentioned above, the torque of the transmission input shaft  41  is transferred from the first drive gear  1 , second drive gear  2 , third drive gear  3 , fourth drive gear  4 , or fifth drive gear  5  to the transmission output shaft  43  through the first driven gear  11 , second driven gear  12 , third driven gear  13 , fourth driven gear  14 , and fifth driven gear  15 . Then, the torque is transferred to an axle (not shown) through a differential gear (not shown) coupled with the transmission output shaft  43 . 
     Further, a current of an electromagnetic valve  105   a  provided in the hydraulic equipment  105  is controlled by the transmission control unit  100 . A pressure plate (not shown) provided in the first clutch  8  is thereby controlled to control the transfer torque of the first clutch  8 . 
     Furthermore, a current of an electromagnetic valve  105   b  provided in the hydraulic equipment  105  is controlled by the transmission control unit  100 . A pressure plate (not shown) provided in the second clutch  9  is thereby controlled to control the transfer torque of the second clutch  9 . 
     A range position signal indicating the shift lever position, P range, R range, N range, D range, or the like, is inputted from a lever device  301  to the transmission control unit  100 . 
     The transmission control unit  100  and the engine control unit  101  transmit and receive information to and from each other through a communication means  103 . 
     The shift actuator  61  is controlled by the electromagnetic valve  105   c  and the electromagnetic valve  105   d  to mesh the first synchromesh  21  with the first driven gear  11 . In this state, when the second clutch  9  is engaged, 1st gear running is carried out. 
     The shift actuator  63  is controlled by the electromagnetic valve  105   g  and the electromagnetic valve  105   h  to mesh the third synchromesh  23  with the second driven gear  12 . In this state, when the first clutch  8  is engaged, 2nd gear running is carried out. 
     Furthermore the shift actuator  61  is controlled by the electromagnetic valve  105   c  and the electromagnetic valve  105   d  to mesh the first synchromesh  21  with the third driven gear  13 . In this state, when the second clutch  9  is engaged, 3rd gear running is carried out. 
     The shift actuator  63  is also controlled by the electromagnetic valve  105   g  and the electromagnetic valve  105   h  to mesh the third synchromesh  23  with the fourth driven gear  14 . In this state, when the first clutch  8  is engaged, 4th gear running is carried out. 
     The shift actuator  62  is controlled by the electromagnetic valve  105   e  and the electromagnetic valve  105   f  to mesh the second synchromesh  22  with the fifth driven gear  15 . In this state, when the second clutch  9  is engaged, 5th gear running is carried out. 
     The shift actuator  62  is controlled by the electromagnetic valve  105   e  and the electromagnetic valve  105   f  to mesh the second synchromesh  22  with the reverse driven gear (not shown). In this state, when the second clutch  9  is engaged, reverse gear running is carried out. 
     In this example, up shift from the 1st gear to the 2nd gear is carried out as follows. In the 1st gear running before the up shift, the first synchromesh  21  is meshed with the first driven gear  11  by controlling the shift actuator  61  by the electromagnetic valve  105   c  and the electromagnetic valve  105   d  and engaging the second clutch  9  by the electromagnetic valve  105   b . In this state, the shift actuator  63  is controlled by the electromagnetic valve  105   g  and the electromagnetic valve  105   h  to mesh the third synchromesh  23  with the second driven gear  12 . Furthermore, the first clutch  8  is gradually engaged and the second clutch  9  is gradually disengaged. 
     In this example, the hydraulic equipment with the electromagnetic valve and hydraulic piston is used as a mechanism for operating the first synchromesh  21 , second synchromesh  22 , and third synchromesh  23 . An electric motor and a reduction gear may be used as the mechanism in place of the electromagnetic valve and the hydraulic piston or an electric motor and a drum may be used as the mechanism. Further, any other mechanism may be used for controlling the synchromesh  21 ,  22 , and  23 . Provided that an electric motor is used as the mechanism, various motor scan be applied. For example, the motor may be a so-called direct-current motor in which a magnet is used as stator and a motor winding is used as rotor or may be a so-called permanent-magnet synchronous motor in which a motor winding is used as stator and a magnet is used as rotor. 
     In this example, the hydraulic equipment with the electromagnetic valve is used as a mechanism for operating the first clutch  8  and the second clutch  9 . Instead of it, the clutches may be operated by using an electric motor and a reduction gear or using pressure plates of the clutches. The pressure plates may be controlled by an electromagnetic coil. Any other mechanism may be used for controlling the first clutch  8  and the second clutch  9 . 
       FIG. 2  illustrates relations of input/output signals between the transmission control unit  100  and the engine control unit  101 . The transmission control unit  100  is configured by a control unit having an input unit  100   i , an output unit  100   o , and a computer  100   c . Similarly, the engine control unit  101  is also configured by a control unit having an input unit  101   i , an output unit  101   o , and a computer  101   c . An engine torque command value TTe is transmitted from the transmission control unit  100  to the engine control unit  101  using the communication means  103 . The engine control unit  101  controls intake air flow rate, fuel quantity, ignition timing, and the like (not shown) of the engine  7  so that TTe is attained. The engine control unit  101  is provided therein with a determination means (not shown) for determining engine torque that becomes input torque to the transmission. The speed Ne of the engine  7  and the engine torque Te produced by the engine  7  are determines by the engine control unit  101  and are transmitted to the transmission control unit  100  by using the communication means  103 . As the engine torque determination means, a torque sensor may be used or an estimating means using a parameter of the engine, such as the injection pulse width of injectors, the pressure in an intake pipe, engine speed, or the like, may be used. 
     The transmission control unit  100  performs the following operation to obtain a desired first clutch transfer torque: it controls the voltage V_cla applied to the electromagnetic valve  105   a  and thereby controls the current of the electromagnetic valve  105   a  to engage or disengage the first clutch  8 . 
     Furthermore the transmission control unit  100  performs the following operation to obtain a desired second clutch transfer torque: it controls the voltage V_clb applied to the electromagnetic valve  105   b  and thereby controls the current of the electromagnetic valve  105   b  to engage or disengage the second clutch  9 . 
     Furthermore the transmission control unit  100  performs the following operation to achieve a desired position of the first synchromesh  21 : it controls the voltages V 1 _slv 1 , V 2 _slv 1  applied to the electromagnetic valves  105   c ,  105   d  and thereby controls the current of the electromagnetic valves  105   c ,  105   d  to mesh or disengage the first synchromesh  21 . 
     Furthermore the transmission control unit  100  performs the following operation to achieve a desired position of the second synchromesh  22 : it controls the voltages V 1 _slv 2 , V 2 _slv 2  applied to the electromagnetic valves  105   e ,  105   f  and thereby controls the current of the electromagnetic valves  105   e ,  105   f  to mesh or disengage the second synchromesh  22 . 
     The transmission control unit  100  adjusts the voltages V 1 _slv 3 , V 2 _slv 3  applied to the electromagnetic valves  105   g ,  105   h  to achieve a desired position of the third synchromesh  23 . It thereby controls the current of the electromagnetic valves  105   g ,  105   h  to mesh or disengage the third synchromesh  23 . 
     The transmission control unit  100  is provided with a current sensing circuit (not shown). It controls the current of each electromagnetic valve by varying voltage output such that the current of each electromagnetic valve becomes equal to a target current. 
     The transmission control unit  100  takes in first input shaft speed signal NiA, second input shaft speed signal NiB, and output shaft speed signal No from the rotation sensor  31 , rotation sensor  32 , and rotation sensor  33 , respectively. Further, it takes in the following signals: a range position signal RngPos indicating the shift lever position, P range, R range, N range, D range, or the like, from the lever device  301 ; an accelerator pedal position signal Aps from an accelerator pedal position sensor  302 ; and an on/off signal Brk from a brake switch  304  for detecting whether or not a brake pedal has been depressed. 
     In this example, a so-called manual mode function is also provided in addition to automatic mode function and a driver manually instructs up shift/down shift. Consequently, the transmission control unit  100  takes in on/off signals UpSw, DnSw from an up-switch  306  and a down-switch  307 , respectively. 
     Further, the transmission control unit  100  takes in the following signals from a sleeve # 1  position sensor  61   a , a sleeve # 2  position sensor  62   a , and a sleeve # 3  position sensor  63   a : a sleeve # 1  position signal RPslv 1 , a sleeve # 2  position signal RPslv 2 , and a sleeve # 3  position signal RPslv 3  respectively indicating the stroke positions of the first synchromesh  21 , second synchromesh  22 , and third synchromesh  23 . 
     For example, when a driver sets the shift range to D range or the like and depresses the accelerator pedal, the transmission control unit  100  determines that the driver is willing to start up or accelerate his/her automobile. When the driver depresses the brake pedal, it determines that the driver is willing to decelerate or stop his/her automobile. Then, it sets an engine torque command value TTe, a first clutch target transfer torque TTs 1 , and a second clutch target transfer torque TTs 2  so as to carry out the driver&#39;s intention. 
     Further, it sets a gear position as a target from a vehicle speed Vsp computed from an output shaft speed No and an accelerator pedal position Aps. Then, it sets the following so as to perform the operation of shifting to the set gear position: an engine torque command value TTe; a first clutch target transfer torque TTs 1 ; a second clutch target transfer torque TTs 2 ; a target sleeve # 1  (a sleeve # 1  corresponds to the first syncromesh  21 ) position TPslv 1 ; a target sleeve # 2  (a sleeve # 2  corresponds to the second syncromesh  22 ) position TPslv 2 ; and a target sleeve # 3  (a sleeve # 3  corresponds to the third syncromesh  23 ) position TPslv 3 . 
     The transmission control unit  100  outputs the following so as to achieve the set first clutch target transfer torque TTs 1 , second clutch target transfer torque TTs 2 , target sleeve # 1  position TPslv 1 , target sleeve # 2  position TPslv 2 , and target sleeve # 3  position TPslv 3 : voltages V_cla, V_clb, V 1 _slv 1 , V 2 _slv 1 , V 1 _slv 2 , V 2 _slv 2 , V 1 _slv 3 , V 2 _slv 3  applied to the electromagnetic valves  105   a ,  105   b ,  105   c ,  105   d ,  105   e ,  105   f ,  105   g ,  105   h.    
     Description will be given to the concrete details of pre-shift control by a control apparatus for automatic transmissions in this embodiment with reference to  FIG. 3  to  FIG. 7 . 
       FIG. 3  is a flowchart illustrating the outline of the details of entire pre-shift control by a control apparatus for automatic transmissions in an embodiment of the invention. 
     The flow of the pre-shift control is comprised of Step  301  (target standby position computation), Step  302  (target standby gear engagement in completion determination), Step  303  (standby-side clutch disengagement completion determination), and Step  304  (standby gear engagement control). 
     Contents of the processing in  FIG. 3  are programmed in the computer  100   c  of the transmission control unit  100 , and this processing is repeatedly carried out at predetermined intervals. That is, the following processing of Steps  301  to  304  is carried out by the transmission control unit  100 . 
     At Step  301  (target standby position computation), a target standby gear position tGP_stb as a target value of the gear position in which a gear should be kept on standby in preparation for the next shifting operation is set. It is set based on a range position signal RngPos, an up switch Up signal Sw, a down switch signal DnSw, an accelerator pedal position signal Aps, a vehicle speed signal Vsp, a brake on/off signal Brk, and the like. 
     At Step  302  (target standby gear engagement incompletion determination), the following processing is carried out: when a sleeve position as a synchromesh position pertaining to the target standby gear position tGP_stb set at Step  301  is in a mesh position, it is determined that standby gear engagement has been completed and the pre-shift control is terminated; and when the sleeve position is not in a mesh position, the flow proceeds to Step  303 . 
     At Step  303  (standby gear engagement permission determination), it is determined whether or not the engagement of a standby gear has been permitted. When the engagement of the standby gear has been permitted, the flow proceeds to Step  304 . When the engagement of the standby gear is not permitted, the pre-shift control in the relevant cycle of execution is terminated. 
     At Step  304  (standby gear engagement control), an engagement load is set by a function using a sleeve position as input. With respect to this function, it is desirable to take the following measure: when a distance from the neutral position to a sleeve position is small (in proximity to the neutral; hereinafter the distance is called in abbreviated form as sleeve position), it takes a relatively small value; when the sleeve position is in an intermediate range (in proximity to the synchronization position), it takes a relatively large value; and when the sleeve position is large (in proximity to the mesh position), it takes a relatively small value again. In consideration of the durability of the synchromeshes, it is desirable that the function should be set so that it takes as small a value as possible with which a standby gear can be engaged. 
     Detailed description will be given to Step  303  (standby gear engagement permission determination) in  FIG. 3  with reference to  FIG. 4 . 
     At Step  401 , it is determined whether or not the current mode is automatic shift mode. When the current mode is automatic shift mode, the flow proceeds to Step  402 . When the current mode is not automatic shift mode, for example, when the current mode is manual shift mode, the flow proceeds to Step  405 . 
     At Step  402 , it is determined whether or not shifting has been completed. That is, it is determined whether or not the clutch to clutch shift in engagement was completed and a desired gear position has been achieved. When shifting has been completed, the flow proceeds to Step  403 . When shifting has not been completed, the flow proceeds to Step  404 . 
     At Step  403 , the engagement of the stand by gear is permitted. At Step  404 , the engagement of the standby gear is not permitted. 
     At Step  405 , it is determined whether or not the disengagement of the clutch on standby coupled with the transmission input shaft having the target standby gear position tGP_stb set at Step  301  has been completed. When it is determined that the disengagement of the clutch on standby has been completed, the flow proceeds to Step  406 . When the disengagement of the clutch on standby has not been completed, the flow proceeds to Step  407 . 
     At Step  406 , the engagement of the stand by gear is permitted. At Step  407 , the engagement of the standby gear is not permitted. 
     The example in  FIG. 4  is constructed such that the timing of permission for the engagement of a standby gear is varied according to whether the current mode is automatic shift mode or any other mode. Instead, the timing of permission for the engagement of a standby gear may be varied according to any other condition, for example, oil temperature. 
     Description will be given to an example of first pre-shift control carried out when it is constructed as illustrated in  FIG. 3  and  FIG. 4  with reference to  FIG. 5 . 
       FIG. 5  is a time diagram illustrating an example of the first pre-shift control in an automobile equipped with a control apparatus for automatic transmissions in an embodiment of the invention. This example of the first pre-shift control illustrates the following: the details of pre-shift control carried out when the vehicle is running in the 1st gear and the target standby gear position, which is a target value of the gear position in which a gear should be kept on standby in preparation for the next shifting operation, is changed from N to 2nd gear; and the details of control carried out when the gear position is shifted from 1st gear to 2nd gear based on a shifting request that subsequently occurs. 
     In  FIG. 5 ,  FIG. 5(A)  indicates a target gear position tGP_nxt;  FIG. 5(B)  indicates a target standby gear position tGP_stb; and  FIG. 5(C)  indicates a sleeve  1  position RPslv 1 . 3rd indicates the engagement position on the 3rd gear side; N is the neutral position; and 1st indicates the mesh position on the 1st gear side.  FIG. 5(D)  indicates a sleeve # 3  position RPslv 3 . 4th indicates the engagement position on the 4th gear side; N indicates the neutral position; and 2nd indicates the mesh position on the 2nd gear side.  FIG. 5(E)  indicates first clutch torque and second clutch torque. 
     Before time t 1 , the various positions are set as follows and the vehicle is running in the 1st gear: the target gear position tGP_nxt is 1st for “1st gear” as indicted in  FIG. 5(A) ; the target standby gear position tGP_stb is N for “neutral” as indicated in  FIG. 5(B) ; the sleeve # 1  position RPslv 1  is 1st for the engagement position on the 1st gear side as indicated in  FIG. 5(C) ; and the sleeve # 3  position RPslv 3  is N for the neutral position as indicated in  FIG. 5(D) . 
     At time t 1 , the target standby gear position tGP_stb in  FIG. 5(B)  is shifted from N for “neutral” to 2nd for “2nd gear” by the processing of Step  301  (target gear position computation) in  FIG. 3 . Then, the determination of Step  402  or Step  405  is carried out according to whether or not the result processing of Step  401  in  FIG. 4  is automatic shift mode. In the processing of either step, the positive determination is made at time t 1 . Therefore, it is determined at Step  303  (standby gear engagement permission determination) that the engagement of the standby gear has been permitted. Then, shifting of the sleeve  3  position RPslv 3  in  FIG. 5(D)  from N for the neutral position to 2nd for the engagement position on the 2nd gear side is started by the processing of Step  304  (standby gear engagement control). 
     When the shifting of the sleeve # 3  position RPslv 3  to 2nd is completed at time t 2 , the pre-shift control in  FIG. 3  is terminated. 
     When the target gear position tGP_nxt in  FIG. 5(A)  is shifted from 1st for “1st gear” to 2nd for “2nd gear” at time t 3 , shifting is started. When the preparation for clutch operation is completed at time t 4 , the second clutch torque is reduced to start disengagement and further the first clutch torque is gradually increased to start engagement. When the clutch to clutch shift in engagement is completed at time t 5 , so-called inertia phase control is carried out to control speed of rotation. At time t 6 , the shifting is completed. 
     Description will be given to an example of second pre-shift control carried out when it is constructed as illustrated in  FIG. 3  and  FIG. 4  with reference to  FIG. 6 . 
       FIG. 6  is a time diagram illustrating an example of the second pre-shift control in an automobile equipped with a control apparatus for automatic transmissions in an embodiment of the invention. This example of the second pre-shift control illustrates the following: the details of pre-shift control carried out when the vehicle is running in the 1st gear in automatic shift mode and the target standby gear position, which is a target value of the gear position in which a gear should be kept on standby in preparation for the next shifting operation, is changed from N to 2nd gear; and the details of pre-shift control carried out when, immediately after the shifting from 1st gear to 2nd gear is started based on a shifting request that subsequently occurs, a request to shift the target standby gear position from 2nd gear to 3rd gear occurs. 
     In  FIG. 6 , the time on the horizontal axis is the same as that in  FIG. 5 . 
       FIG. 6(A) ,  FIG. 6(B) ,  FIG. 6(C) ,  FIG. 6(D) , and  FIG. 6(E)  respectively indicate the same signals as in  FIG. 5(A) ,  FIG. 5(B) ,  FIG. 5(C) ,  FIG. 5(D) , and  FIG. 5(E) . 
     The contents before time t 4  are the same as those illustrated in  FIG. 5 . 
     At time t 5 , the target standby gear position tGP_stb in  FIG. 6(B)  is shifted from 2nd for “2nd gear” to 3rd for “3rd gear.” Since it is determined at Step  401  in  FIG. 4  that the current mode is automatic shift mode, the determination of Step  402  is carried out. At time t 5 , the determination of Step  402  becomes negative, namely the determination is that the shifting is being done at present. Therefore, it is determined at Step  303  (standby gear engagement permission determination) that the engagement of the standby gear has not been permitted. When the shifting is completed at time t 7 , the positive determination is made at Step  402 . Therefore, it is determined at Step  303  (standby gear engagement permission determination) that the engagement of the standby gear has been permitted. Then, shifting of the sleeve # 1  position RPslv 1  in  FIG. 5(C)  from 1st for the engagement position on the 1st gear side to 3rd for the engagement position on the 3rd gear side is started by the processing of Step  304  (standby gear engagement control). 
     When the shifting of sleeve # 1  position RPslv 1  to 3rd is completed at time t 8 , the pre-shift control in  FIG. 3  is terminated. At time t 7 , the target gear position tGP_nxt in  FIG. 6(A)  is shifted from 2nd for “2nd gear” to 3rd for “3rd gear.” However, the shifting of the sleeve # 1  position RPslv 1  to 3rd has not been completed at time t 7 -t 8 , and shifting is not started. When the shifting of the sleeve  1  position RPslv 1  to 3rd is thereafter completed at time t 8 , shifting is started. 
     Description will be given to an example of third pre-shift control carried out when it is constructed as illustrated in  FIG. 3  and  FIG. 4  with reference to  FIG. 7 . 
       FIG. 7  is a time diagram illustrating an example of the third pre-shift control in an automobile equipped with a control apparatus for automatic transmissions in an embodiment of the invention. This example of the third pre-shift control illustrates the following: the details of pre-shift control carried out when the vehicle is running in the first gear in manual shift mode and the target standby gear position, which is a target value of the gear position in which a gear should be kept on standby in preparation for the next shifting operation, is changed from N to 2nd gear; and the details of pre-shift control carried out when immediately after the shifting from 1st gear to 2nd gear is started based on a shifting request that subsequently occurs, a request to shift the target standby gear position from 2nd gear to 3rd gear occurs. 
     In  FIG. 7 , the time on the horizontal axis is the same as that in  FIG. 5 . 
       FIG. 7(A) ,  FIG. 7(B) ,  FIG. 7(C) ,  FIG. 7(D) , and  FIG. 7(E)  respectively indicate the same signals as in  FIG. 5(A) ,  FIG. 5(B) ,  FIG. 5(C) ,  FIG. 5(D) , and  FIG. 5(E) . 
     The contents before time t 6  are the same as those illustrated in  FIG. 5 .  FIG. 7  is different from  FIG. 6  in that the following operation is performed. At time t 6 , it is determined at Step  401  in  FIG. 4  that the current mode is manual shift mode. Therefore, the determination of Step  405  is carried out. Because of the disengagement of second clutch torque, the positive determination is made at step  405 . Consequently, it is determined at Step  303  (standby gear engagement permission determination) that the engagement of the standby gear has been permitted. Then, shifting of the sleeve  1  position RPSlv 1  in  FIG. 7(C)  from 1st for the engagement position on the 1st gear side to 3rd for the engagement position on the 3rd gear side is started by the processing of Step  304  (standby gear engagement control). 
     When the shifting of the sleeve  1  position RPslv 1  to 3rd is completed at time t 7 , the pre-shift control in  FIG. 3  is terminated. At time t 7 , the target gear position tGP_nxt in  FIG. 6(A)  shifted from 2nd for “2nd gear” to 3rd for “3rd gear.” Since the shifting of the sleeve  1  position RPslv 1  to 3rd has been completed, shifting is immediately started. 
     When a control apparatus for automatic transmissions is constructed as mentioned above, it is possible to advance the timing of start of pre-shift control and enhance the response when a shifting request continuously occurs.