Shift control method for automatic transmission and system therefor

A method and system for controlling shift in an automatic transmission that can establish a plurality of gear ratios by selectively supplying a hydraulic pressure for a plurality of frictional engaging elements. The shift control system for the automatic transmission includes a device for selecting either an automatic shifting mode, in which predetermined gear ratios are established depending upon a vehicle driving condition, or a manual shifting mode, in which predetermined gear ratios are established by manual operation; a learning control unit for optimizing hydraulic pressure for the frictional engaging elements on the basis of an actual shifting condition; a learning control inhibiting unit for inhibiting learning control by the learning control unit when the manual shifting mode is selected; and a learning control inhibiting release unit that enables learning control by the learning control unit and disables inhibition of learning control by the learning control inhibiting unit when a shifting operation in the manual shifting mode is taken place under a vehicle driving condition falling within a predetermined zone. The invention prevents increasing of shift shock in the manual shifting mode without using RAM having large capacity.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention relates to a shift controlling method for an 
automatic transmission and a system therefor. 
In an automatic transmission which can establish a plurality of gear ratios 
by selectively supply hydraulic pressure to a plurality of friction 
engagement elements, there has been known the automatic transmission, in 
which either an automatic shifting mode to automatically establish a 
predetermined gear ratio from a preliminarily set map of shifting range on 
the basis of a vehicle driving condition, such as an engine load 
represented by a throttle opening, and a vehicle speed, or a manual 
shifting mode, in which the driver establishes a desired gear ratio by 
manual operation, can be selected. 
In order to prevent shift shock from increasing due to fluctuation of 
shifting performance of respective individual automatic transmissions due 
to tolerance in spool valves, springs and so on, for selectively supplying 
a hydraulic pressure to the friction engagement elements, or secular 
change of the friction engagement elements, Japanese Patent Application 
Laid-open No. 63-92863 (1988) and Japanese Patent Application Laid-open 
No. 1-169164 (1989) disclose system which performs learning control so 
that an actual shifting period converges to a targeted shifting period to 
from initiation of shifting to completion of shifting. In the learning 
control of the shifting period, the target sifting period and the actual 
shifting period are compared to correct a hydraulic pressure value 
preliminarily stored in a map or the like to output the corrected 
hydraulic pressure upon next shifting so as to converge the actual 
shifting period to the target shifting period. 
When the learning control of the shifting period is performed in the 
automatic shifting mode, since the vehicle driving conditions to cause 
shifting operation are determined univocally, required storage capacity of 
RAM to be used for storing the content of learning is relatively small. 
However, when learning control of the shifting period is attempted during 
manual shifting mode, huge amount of storage capacity is required for RAM 
to be used since shifting operation tends to be performed in arbitrary 
vehicle driving condition and all vehicle driving conditions where the 
manual shifting operation is taken place. Furthermore, control logic 
becomes too complicate. 
In order to avoid such problem, in the conventional shift control system 
for an automatic transmission, as disclosed in Japanese Patent Application 
Laid-open No. 5-332437 (1993), learning control of the shifting period is 
inhibited while manual shifting mode is selected to simplify control logic 
to permit use of RAM having small storage capacity. 
In case of the conventional shift control system of the automatic 
transmission disclosed in Japanese Patent Application Laid-open No. 
5-332437, if automatic shifting mode is rarely selected and manual 
shifting mode is continuously used for a long period, learning control of 
the shifting period is substantially not performed. As a result, it 
becomes impossible to prevent increasing of shift shock or degradation of 
durability of the frictional engaging elements. 
The foregoing problem will not be happened when a proportion of driving of 
the vehicle in the automatic shifting mode is sufficiently large and when 
manual shifting mode is selected for a short period. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a shift control for an 
automatic transmission and a system therefor, which can reduce shift shock 
even in manual shifting mode without using RAM having large storage 
capacity. 
According to the first aspect of the present invention, a shift control 
method for an automatic transmission which can establish a plurality of 
gear ratios by selectively supplying hydraulic pressure to a plurality of 
frictional engaging elements, comprising: 
step of selecting either an automatic shifting mode, in which predetermined 
gear ratios are established depending upon a vehicle driving condition, or 
a manual shifting mode, in which predetermined gear ratios are established 
by manual operation; 
learning control step of optimizing hydraulic pressure for the frictional 
engaging elements on the basis of an actual shifting condition; 
learning control inhibiting step of inhibiting the learning control step 
when the manual shifting mode is selected; and 
learning control inhibiting release step of enabling the learning control 
step and disabling the learning control inhibiting step when a shifting 
operation in the manual shifting mode is taken place under a vehicle 
driving condition falling with a predetermined zone. 
According to the present invention, either the automatic shifting mode, in 
which predetermined gear ratios are established depending upon a vehicle 
driving condition, or a manual shifting mode, in which predetermined gear 
ratios are established by manual operation, is selected. 
When the automatic shifting mode is selected, the predetermined gear ratios 
are established by selectively supplying hydraulic pressure for a 
plurality of frictional engaging elements depending upon the vehicle 
driving condition. At this time, the learning control step is executed for 
optimizing the hydraulic pressure to the frictional engaging elements on 
the basis of the actual shifting condition. 
When the manual shifting mode is selected, the hydraulic pressure is 
selectively supplied to a plurality of frictional engaging elements to 
establish predetermined gear ratios by manual operation. At this time, the 
learning control step is inhibited. However, when the shifting operation 
in the manual shifting mode is taken place in the vehicle driving 
condition falling within a predetermined zone, the learning control 
inhibiting step is not performed and learning control step is performed 
for optimizing the hydraulic pressure to the frictional engaging elements 
on the basis of the actual shifting condition. 
In the shift control method for an automatic transmission according to the 
first aspect of the present invention, the vehicle driving condition may 
be represented by a vehicle speed and a throttle opening. 
The learning control step may optimize hydraulic pressure to the frictional 
engaging elements for converging an actual shifting period from initiation 
of shifting to completion of shifting to a target shifting period. 
The learning control inhibiting step may inhibit learning control step when 
a fluid temperature of an automatic transmission fluid is lower than or 
equal to a predetermined temperature or a throttle opening is less than or 
equal to a predetermined opening. 
The learning control inhibiting release step may enable the learning 
control step and disable the learning control inhibiting step when an 
up-shifting operation in the manual shifting mode is taken place under a 
vehicle driving condition falling with a predetermined zone. 
The predetermined zone may be a range substantially corresponding to a 
range where shifting operation is to be performed in the automatic 
shifting mode. 
According to the second aspect of the present invention, a shift control 
system for an automatic transmission which can establish a plurality of 
gear ratios by selectively supplying hydraulic pressure to a plurality of 
frictional engaging elements, comprising: 
means for selecting either an automatic shifting mode, in which 
predetermined gear ratios are established depending upon a vehicle driving 
condition, or a manual shifting mode, in which predetermined gear ratios 
are established by manual operation; 
learning control means for optimizing hydraulic pressure for the frictional 
engaging elements on the basis of an actual shifting condition; 
learning control inhibiting means for inhibiting learning control by the 
learning control means when the manual shifting mode is selected; and 
learning control inhibiting release means for enabling learning control by 
the learning control means and disabling inhibition of learning control by 
the learning control inhibiting means when a shifting operation in the 
manual shifting mode is taken place under a vehicle driving condition 
falling with a predetermined zone. 
According to the present invention, either the automatic shifting mode, in 
which predetermined gear ratios are established depending upon a vehicle 
driving condition, or a manual shifting mode, in which predetermined gear 
ratios are established by manual operation, is selected by the selecting 
means. 
When the automatic shifting mode is selected, the predetermined gear ratios 
are established by selectively supplying hydraulic pressure for a 
plurality of frictional engaging elements depending upon the vehicle 
driving condition. At this time, the learning control means is executed 
for optimizing the hydraulic pressure to the frictional engaging elements 
on the basis of the actual shifting condition. 
When the manual shifting mode is selected, the hydraulic pressure is 
selectively supplied to a plurality of frictional engaging elements to 
establish predetermined gear ratios by manual operation. At this time, the 
learning control inhibiting means inhibits learning control by the 
learning control means. However, when the shifting operation in the manual 
shifting mode is taken place in the vehicle driving condition falling 
within a predetermined range, the learning control inhibiting means is not 
inhibited learning control by the learning control inhibiting lerease 
means, and learning control means is learning control for optimizing the 
hydraulic pressure to the frictional engaging elements on the basis of the 
actual shifting condition. 
In the shift control system for an automatic transmission according to the 
second aspect of the present invention, the vehicle driving condition may 
be represented by a vehicle speed and a throttle opening. 
The learning control means may optimize hydraulic pressure to the 
frictional engaging elements for converging an actual shifting period from 
initiation of shifting to completion of shifting to a target shifting 
period. 
The learning control inhibiting means may inhibit learning control by the 
learning control means when a fluid temperature of an automatic 
transmission fluid is lower than or equal to a predetermined temperature 
or a throttle opening is less than or equal to a predetermined opening. 
The learning control inhibiting release means may enable learning control 
by the learning control means and disable inhibition of learning control 
by the learning control inhibiting means when an upshifting operation in 
the manual shifting mode is taken place under a vehicle driving condition 
falling with a predetermined zone. 
The predetermined zone may be a range substantially corresponding to a 
range where shifting operation is to be performed in the automatic 
shifting mode. 
According to the present invention, when shifting operation in the manual 
mode is performed in the vehicle driving condition falling in the 
predetermined zone where automatic shifting operation is performed when 
the automatic shifting mode is selected, learning control of the shifting 
period is performed. Therefore, even when vehicle is driven in manual 
shifting mode for a long period, increasing of shift sock lowering of 
durability of the frictional engaging elements can be successfully 
restricted. 
In order to increase number of times of learning control of the shifting 
period, immediately returning from the manual shifting mode to the 
automatic shifting mode, where the hydraulic pressure to be supplied to 
the frictional engaging elements is out of the optimal value, it can be 
converged to the optimal value within a short period to make shift shock 
small.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
While the present invention will be explained in detail hereinafter in 
terms of one embodiment as applied to an automatic transmission with 
forward four speeds of gear ratios, with reference to FIGS. 1 to 3, the 
present invention is applicable for any automatic transmission which can 
establish a plurality of gear ratios by selectively supplying hydraulic 
pressure for a plurality of frictional engaging elements. 
General construction of the preferred embodiment is illustrated in FIG. 1. 
An automatic transmission 12 having a plurality of frictional engaging 
elements 11 is designed to establish a desired gear ratio via a hydraulic 
pressure control unit 14 on the basis of a command from CPU 13. The 
automatic transmission 12 has an automatic shifting mode to automatically 
establishing predetermined gear ratios on the basis of vehicle driving 
conditions and a manual shifting mode, in which desired gear ratios in 
response to manual shifting operation of a driver through a selector lever 
(see FIG. 2). 
A shifting mode pattern in the shown embodiment is illustrated in FIG. 2. 
The selector lever 15 can be shifted to an automatic shifting mode range 
Z.sub.A and a manual shifting mode range Z.sub.M connected to the 
automatic shifting mode range Z.sub.A. Whether the selector lever 15 is in 
the manual shifting mode range Z.sub.M or not is detected by a manual 
shifting mode switch 16. 
In the automatic shifting mode range Z.sub.A, select positions of P, R, N, 
D, 3, 2 and 1 are set. P range is a position where an output shaft of the 
automatic transmission is mechanically locked at neutral position. R range 
is the position to select for reverse drive position. N range is the 
position to select neutral position. D range is the position for automatic 
shifting between first to fourth gear ratios, 3 range is the position for 
automatic shifting between first to third speed ratios, 2 range is the 
position for automatic shifting between first and second speed ranges, and 
1 range is the position for holding the first speed ratio. The select 
position of the selector lever 15 in the automatic shifting mode range 
Z.sub.A, is detected by an inhibitor switch 17. 
In the manual shifting mode range Z.sub.M, the selector lever 15 is biased 
to the neutral position by a spring force as shown in FIG. 2. At the 
shifting end of the selector lever 15 in the manual shifting mode range 
Z.sub.M, an up-shifting switch 18 and a down-shifting switch 19 are 
combined. Every time of shifting the selector lever 15 toward higher (H) 
range side, namely up-shifting switch 18 is depressed, up-shifting 
operation is performed up to the fourth speed ratio. Conversely, every 
time of down-shifting toward lower (L) speed range side, namely down 
shifting switch 19 is depressed. down-shifting operation is performed up 
to the first speed ratio. 
In the shown embodiment, a shifting mode pattern is separated between the 
automatic shifting mode range Z.sub.A and the manual shifting mode range 
Z.sub.M. However, the select position of the selector lever 15 may be 
assumed to be P, R, N, D and T, and an up-shifting switch and a 
down-shifting switch for manual shifting operation are built-in a not 
shown steering wheel and so on. Thereby, when the selector lever is in T 
range, manual up-shifting and down-shifting operation can be performed by 
operating the up-shifting switch and the down-shifting switch for enabling 
shifting operation. 
To a shift commanding portion 20 included in CPU 13, ON/OFF signals of the 
manual mode switch 16, the up-shifting switch 18 and the down-shifting 
switch 19, detection signals from various sensors for detecting the 
driving condition of the vehicle, such as those from a vehicle speed 
sensor 21, a throttle opening sensor 22 as an engine load sensor, and a 
detection signal from the inhibitor switch 17 are input. When the driver 
shifts the selector lever 15 into the manual shifting mode range Z.sub.M, 
the manual mode switch 16 is turned ON. Thus, manual shifting mode is 
selected. Conversely, when the selector lever 15 is shifted to the 
automatic shifting mode range Z.sub.A, the manual mode switch 16 is turned 
OFF. Thus, automatic shifting mode is selected. 
In the shift commanding portion 20 of CPU 13, a shift map for automatic 
shifting mode, as shown in FIG. 3, setting predetermined shifting ranges 
depending upon a vehicle speed and a throttle opening, is stored. When the 
automatic shifting mode is selected, predetermined gear ratios are 
automatically established according to the shift map of FIG. 3 on the 
basis of the vehicle speed and the throttle opening. In FIG. 3, a solid 
line shows the case of up-shifting, and a broken line shows the case of 
down-shifting. A down-shifting line 1.sub.1 .rarw.1.sub.2 represents a 
shifting boundary to actually cause shifting from second gear ratio to 
first gear ratio when the shifting range before shifting operation is 
second or higher gear ratio and when the selector lever 15 is shifted into 
1 range. 
The hydraulic pressure control unit 14 includes a shifting actuator 23 for 
selectively supplying hydraulic pressure for a plurality of frictional 
engaging elements 11 on the basis of the command from the shift commanding 
portion 20 and a hydraulic pressure adjusting actuator 24 for controlling 
the hydraulic pressure to be supplied to predetermined frictional engaging 
elements 11 via the shifting actuator 23. The hydraulic pressure adjusting 
actuator 24 performs control for optimizing the hydraulic pressure to be 
supplied to the frictional engaging elements 11 on the basis of a command 
from a hydraulic pressure commanding portion 25 included in CPU 13. 
Specifically, the hydraulic pressure adjusting actuator 24 corrects a 
predetermined basic hydraulic pressure value with a hydraulic pressure 
correction value from a hydraulic pressure correction value setting 
portion 33 depending upon the throttle opening and type of shifting, 
namely relationship between the gear ratios before shifting and that to 
shifting. Thus, the optimal hydraulic pressure value to be supplied to the 
frictional engaging element 11 is set by the hydraulic pressure commanding 
portion 25. 
In CPU 13, a learning control portion 26 for optimizing the hydraulic 
pressure to be adjusted the hydraulic pressure adjusting actuator 24 on 
the basis of actual shifting condition, a learning inhibiting portion 27 
for inhibiting learning control by the learning control portion 26 when 
the manual shifting mode is select, a leaning control inhibiting release 
portion 28 for disabling inhibition of learning control by the leaning 
control inhibiting portion 27 only when the shifting operation in the 
manual shifting mode is taken place at the vehicle driving condition 
within a predetermined zone. Therefore, to the learning control inhibiting 
portion 27 and the learning control inhibiting release portion 28, the 
ON/OFF signal is output from the manual shifting mode switch 16. Also, to 
the learning control inhibiting release portion 28, the signals from the 
up-shifting switch 18, the down-shifting switch 19, the vehicle speed 
sensor 21, the throttle opening sensor 22 and the inhibitor switch 17 are 
input. 
The learning control portion 26 includes a shifting period detecting 
portion 29 for counting a time from initiation of shifting to completion 
of shifting, a shifting period storage portion 30 for temporarily storing 
an actual shifting period detected by the shifting period detecting 
portion 29, a target shifting period setting portion 31 for preliminarily 
setting a target shifting period on the basis of a predetermined driving 
condition of the vehicle, a comparator portion 32 for deriving a 
difference between the target shifting period and the actual shifting 
period by comparing the actual shifting period stored in the shifting 
period storage portion 30 and the target shifting period read out from the 
target shifting period setting portion 31, and s hydraulic pressure 
correction value setting portion 33 for correcting the hydraulic pressure 
value output from the hydraulic pressure commanding portion 25 depending 
upon the time difference derived by the comparator portion 32. The 
hydraulic pressure correction value from the hydraulic pressure correction 
value setting portion 33 is output to the hydraulic pressure commanding 
portion 25. 
In the shown embodiment, even when the automatic shifting mode is selected, 
if a fluid temperature of the automatic transmission fluid is lower than 
or equal to a predetermined temperature, e.g. 40.degree. C., or if the 
throttle opening is less than or equal to a predetermined value, e.g. 10%, 
learning control is not performed in view of stability of control. 
Therefore, detected information from the fluid temperature sensor, the 
throttle opening sensor 22 and so on are also input to the learning 
control inhibiting release portion 28 and the learning control inhibiting 
portion 27. Irrespective of the automatic shifting mode and the manual 
shifting mode, if the fluid temperature of the automatic transmission 
fluid is lower than or equal to the predetermined temperature, or if the 
throttle opening is less than or equal to the predetermined opening, 
learning control by the learning control portion 26 is inhibited. 
When a signal for inhibiting learning control is output from the learning 
control inhibiting portion 27 to the learning control portion 26, the 
shifting period detecting portion 29 does not perform detection of the 
actual shifting period in the current shifting, the shifting period 
storage portion 30 maintains the actual shifting period stored in the 
preceding occurrence of shifting operation. In such condition, the 
comparator 31 does not perform comparison of the actual shifting period 
stored in the preceding occurrence of shifting operation and the target 
shifting period. Then, the hydraulic pressure correction value setting 
portion 30 outputs the hydraulic pressure correction value output at the 
preceding occurrence of shifting operation to the hydraulic pressure 
commanding portion 25, again. The foregoing predetermined zone in the 
learning control inhibiting release portion 28, in the shown embodiment, 
is the case where the driver performs up-shifting operation by shifting 
the selector lever 15 to the H range side in the hatching region in the 
vicinity of the up-shifting line shown in FIG. 3 while the manual shifting 
mode is selected. Namely, when the driver performed up-shifting operation 
in the hatching region, the learning control inhibiting release portion 28 
interrupts output for inhibiting learning control to the learning control 
portion 26 from the learning control inhibiting portion 27 to perform 
learning control by the learning control portion 26. 
A cross-hatching region formed along the up-shifting line in the automatic 
shifting mode as shown in FIG. 3, is the range to interrupting output for 
inhibiting learning to the learning control portion 26 by the learning 
control inhibiting release portion 28 and thus to perform learning 
control, in which the hydraulic pressure commanding portion 25 uses the 
hydraulic pressure correction value output from learning control portion 
26. This range is stored in the learning control inhibiting release 
portion 28 to have different values depending upon type of up-shifting, 
namely 1-2 shifting, 1-3 shifting, 1-4 shifting, 2-3 shifting, 2-4 
shifting and 3-4 shifting. In the shown embodiment, the minimum vehicle 
speed and the maximum vehicle speed corresponding to each type of 
up-shifting and the throttle opening are read out from the learning 
control inhibiting release portion 28 to make judgement whether the 
vehicle speed falls between the minimum vehicle speed and the maximum 
vehicle speed. Thus, the learning control inhibiting release portion 28 
makes judgement whether the current vehicle driving condition falls within 
the learning control enabling zone shown by cross-hatching in FIG. 3. 
Flow of process in the shown embodiment is shown in FIG. 4. At step S1, 
information from the vehicle speed sensor 21 and the throttle opening 
sensor 22 as vehicle driving condition is read out. At step S2, check is 
performed whether the selector lever 15 is in D range, 3 range, 2 range, 1 
range or the manual shifting mode range Z.sub.M, namely forward driving 
range is selected. 
At step S2, if judgment is made that selector lever 15 does not select the 
forward driving range, the process is returned to a not shown main 
process, and repeat the process of the step S1. When judgment that the 
selector lever 15 selects the forward driving range, the process is 
advanced to step S3 to check whether the manual shifting mode switch 16 is 
in the OFF condition. 
At step S3, if judgment is made that the manual shifting mode switch 15 is 
in OFF state, namely the automatic shifting mode is selected, the process 
is advanced to step S4 to make judgment whether shifting is necessary or 
not on the basis of the shift map of FIG. 3. At step S4, if judgment is 
made that shifting is not required under the current vehicle driving 
condition, the process returns to the not shown main process to repeat the 
process from the step S1. If necessity of shifting is judged at step S4, 
process is advanced to step S5 to check whether the current vehicle 
driving condition is in a range where the learning control permitted or 
not. 
If judgment is made that the current vehicle driving condition is not the 
range where the learning control is permitted at step S5, namely, if the 
fluid temperature of the automatic transmission fluid is lower than or 
equal to the predetermined temperature, or if the throttle opening is less 
than or equal to the predetermined opening and thus stable control cannot 
be expected, the process returns to the not shown main process, and repeat 
the process from the step S1. When judgment is made that the current 
vehicle driving condition is the range where the learning control is 
permitted at step S5, the process is advanced to step S6 to compare the 
last actual shifting period and the target shifting period to derive the 
hydraulic pressure correction value in the learning control portion 26. 
Then, at step S7, the hydraulic pressure correction value is output to the 
hydraulic pressure commanding portion 25. The hydraulic pressure 
commanding portion 25 derives an optimal hydraulic pressure value on the 
basis of the hydraulic pressure correction value and the basic hydraulic 
value to output the hydraulic pressure command signal to the hydraulic 
pressure adjusting actuator 24 for establishing the optimal hydraulic 
pressure value, at step S8, and then to output the shifting command 
signal, at step S9. At step S10, the current actual shifting period is 
measured. The actual shifting period measured at step S10 is stored at 
step S11. Then, process is returned to the not shown main process, and 
repeat the process again from step S1. 
When the manual shifting mode switch 16 is not in the OFF state as checked 
at step S3, namely the manual shifting mode is selected, the process is 
advanced to step S12 to check whether the up-shifting switch 18 or the 
down-shifting switch 19 is turned ON or not, namely whether the shifting 
signal is input to the shifting commanding portion 20 or not. If judgment 
is made that the up-shifting switch 18 and the down-shifting switch 19 are 
held OFF, namely the driver does not want to shift the current gear ratio, 
the process is returned to the not shown main process, and repeat the 
process again from step S1. If the up-shifting switch 18 or the 
down-shifting switch 19 is turned ON, namely when the driver wants to 
cause shifting of the gear ratio from the current gear ratio, check is 
performed at step S13 whether the current input is ON signal of the 
up-shifting switch 18 or not. 
If judgment is made that the current input is the ON signal of the 
up-shifting switch 18 at step S13, the process is advanced to step S14 to 
check whether the current vehicle driving condition falls within the 
learning control enabling zone of the manual shifting mode as indicated by 
cross-hatching region in FIG. 3. If judgment is made that the current 
vehicle driving condition falls within the learning control enabling zone, 
the process is advanced to step S6 to compare the last actual shifting 
period and the target shifting period to derive the hydraulic pressure 
correction value in the learning control portion 26. 
If judgment is made that the current vehicle driving condition does not 
fall within the learning control enabling zone at step S14, or when the 
current input is not ON signal of the up-shifting switch 18 at step S13, 
learning control is not performed. Then, the process is advanced to step 
S15 to read out the hydraulic pressure correction value used in the 
preceding occurrence of shifting. Then, the read out hydraulic pressure 
correction value is output to the hydraulic pressure commanding portion 25 
at step S16. The hydraulic pressure commanding portion 25 derives an 
optimal hydraulic pressure value on the basis of the hydraulic pressure 
correction value and the basic hydraulic value to output the hydraulic 
pressure command signal to the hydraulic pressure adjusting actuator 24 
for establishing the optimal hydraulic pressure value, at step S17, and 
then to output the shifting command signal, at step S18. Then, process is 
returned to the not shown main process, and repeat the process again from 
step S1. 
When the selector lever 15 is in the automatic shifting mode range Z.sub.A, 
when shifting operation by the selector lever 15 between 3, 2 and 1 
ranges, for example shifting from second gear ratio at 2 range to third 
gear ratio at 3 range, or from 1 range to second gear ratio at 2 range, is 
performed in the cross-hatching region formed along the up-shifting line 
in the manual shifting mode as shown in FIG. 3, learning of the shifting 
period is performed as a matter of course. 
In the shown embodiment, judgment whether the current vehicle driving 
condition falls within the learning control enabling zone shown by the 
cross-hatching region in FIG. 3, is made in the learning control 
inhibiting release portion 28 by reading out the minimum vehicle speed and 
the maximum vehicle speed corresponding to the type of up-shifting and the 
throttle opening by the learning control inhibiting release portion 28 and 
making judgment whether the vehicle speed falls between the minimum 
vehicle speed and the maximum vehicle speed. However, it is possible to 
make judgment whether the current vehicle driving condition falls within 
the learning control enabling zone shown by the cross-hatching region in 
FIG. 3 by reading out the minimum throttle opening and the maximum 
throttle opening corresponding to the type of up-shifting and the throttle 
opening by the learning control inhibiting release portion 28 and making 
judgment whether the current throttle opening falls between the minimum 
throttle opening and the maximum throttle opening.