Control apparatus for hydraulically operated vehicular transmission

A control apparatus for a hydraulically operated vehicular transmission has a plurality of transmission trains to be established by a selective operation of a plurality of hydraulic engaging elements. The apparatus has a selecting device for selecting a transmission train according to a running condition of a vehicle. The apparatus is provided with a detecting device for detecting a power transmission capability value of the hydraulic engaging elements, and a device for determining a transmission train to be established, based on a detected result of the detecting device and a selected result of the selecting device. The detecting device detects a hydraulic engaging element whose power transmission capability value is above a predetermined value and designates a transmission train that corresponds to the detected hydraulic engaging element. The device for determining the transmission train determines a transmission train to be established, based on the transmission train designated by the detecting device and the transmission train or trains selected by the selecting device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a control apparatus for a hydraulically 
operated vehicular transmission having a plurality of transmission trains 
to be established by a selective operation of a plurality of hydraulic 
engaging elements. 
2. Description of Related Art 
As a control apparatus for this kind of transmission, there is 
conventionally known the following. Namely, a control apparatus is 
provided with a hydraulic control circuit for controlling the supply and 
discharge of hydraulic oil to and from a plurality of hydraulic engaging 
elements, and an electronic control circuit in which there are stored 
mapped speed change characteristics to be defined by parameters of an 
engine load such as a throttle opening degree, and a vehicle speed. By 
means of the electronic control circuit a transmission train corresponding 
to the throttle opening degree and the vehicle speed at the present moment 
is selected, and an order signal is outputted to the hydraulic control 
circuit. The hydraulic oil is then supplied to the hydraulic engaging 
element that was selected so as to establish the selected transmission 
train, thereby effecting an automatic speed changing. 
The speed change characteristics define an upshift characteristic line 
(upshift line) and a downshift characteristic line (downshift line) 
between respective two transmission trains that are next to each other in 
the order of speed. In the hysteresis region between the upshift line and 
the downshift line it becomes possible to establish both transmission 
trains on the low-speed side and the high-speed side. Especially, there is 
recently a tendency of enlarging the region in which the high-speed 
transmission trains can be established in order to improve the specific 
fuel consumption. In this case, if the speed change characteristics as 
shown in FIG. 2 are employed, there will be a region in which three or 
more transmission trains can be established. It becomes therefore 
difficult to judge which transmission train should be established. 
In order to solve this problem, there is known, as in Japanese Published 
Unexamined Patent Application No. 190960/1988, an art in which the 
following procedure is followed. Namely, the speed change characteristics 
and the throttle opening degree as well as the vehicle speed at the 
present moment are compared, and the lowest speed transmission train SL 
that can be established and the highest speed transmission train SH that 
can be established from the viewpoint of speed change characteristics are 
picked up. When the speed of the presently established transmission train 
SO is in the relationship SL.ltoreq.SO.ltoreq.SH, the transmission train 
SO is continued to be established, and when SO&lt;SL, upshifting is effected 
from SO to SL, and when SO&gt;SH, downshifting is effected from SO to SH. 
In this prior art, when the running condition changes, while running at the 
fifth speed at point A in FIG. 2, sequentially to points B, C, D, E and F 
by increasing the depression of an accelerator pedal, the fifth speed will 
be maintained at point B because SL=the fourth speed, SH=the fifth speed 
and SL.ltoreq.SO.ltoreq.SH. The fifth speed will be maintained at point C 
because SL=the third speed, SH=the fifth speed and similarly 
SL.ltoreq.SO.ltoreq.SH. At point D, downshifting from the fifth speed to 
the third speed will be effected because SL=SH=the third speed and SO&gt;SH. 
At point E, the third speed will be maintained because SL=the second 
speed, SH=the third speed and SL.ltoreq.SO.ltoreq.SH. At point F, 
downshifting from the third speed to the second speed will be effected 
because SL=the first speed, SH=the second speed and SO&gt;SH. Then, when the 
running condition sequentially moves from point F to points E, D, C, B and 
A by releasing or decreasing the depression of the accelerator pedal, the 
second speed will be maintained at point E because SL.ltoreq.SO.ltoreq.SH. 
At point D, upshifting from the second speed to the third speed will be 
effected because SO&lt;SL. At point C, the third speed will be maintained 
because SL.ltoreq.SO.ltoreq.SH. At point B, upshifting from the third 
speed to the fourth speed will be effected because SO&lt;SL. At point A, 
upshifting to the fifth speed will be effected because SO&lt;SL=SH. 
Normally, there will exist a time lag from the time at which the supply of 
the hydraulic oil is started to the time at which the hydraulic engaging 
elements come into substantial engagement. Here, in case the running 
condition transfers from point A to point D in FIG. 2, thereby starting 
the downshifting to the third speed, and thereafter immediately transfers 
to point B, upshifting to the fourth speed will be effected before the 
hydraulic engaging element for the third speed comes into substantial 
engagement. It follows that the amount of transmission of the driving 
force decreases until the hydraulic engaging element for the fourth speed 
has come into substantial engagement. At this time, the hydraulic engaging 
element for the fifth speed still has some hydraulic pressure left therein 
because only a short time has lapsed from the point of time of 
downshifting to the third speed. Therefore, if an upshifting is made to 
the fifth speed that can be established at point B, the hydraulic engaging 
element for the fifth speed will quickly be brought into engagement, with 
the result that the interval from the time of downshifting to the third 
speed to the time at which the driving force is sufficiently transmitted 
becomes short. In the above-described prior art, however, there will be 
effected only the upshifting to the fourth speed when the running 
condition has transferred from point D to point B. Therefore, a relatively 
long time is required until the driving force is sufficiently transmitted, 
resulting in a poor drivability. 
SUMMARY OF THE INVENTION 
In view of the above points, the present invention has an object of 
providing a control apparatus in which a transmission train to be 
established is determined also taking into consideration the conditions of 
each of the hydraulic engaging elements so as to improve the drivability 
of a vehicle. 
In order to attain the above-described and other objects, the present 
invention is a control apparatus for a hydraulically operated vehicular 
transmission having a plurality of transmission trains to be established 
by a selective operation of a plurality of hydraulic engaging elements, 
the control apparatus having selecting means for selecting a transmission 
train according to a running condition of a vehicle. The control apparatus 
comprises detecting means for detecting a power transmission capability 
value of each of the hydraulic engaging elements, and transmission train 
determining means for determining a transmission train to be established, 
based on a detected result of the detecting means and a selected result of 
the selecting means. 
In this case, it is preferable to arrange such that the selecting means 
compares speed change characteristics to be defined with an engine load 
and a vehicle speed as parameters and a present engine load and a present 
vehicle speed and selects one or a plurality of transmission trains that 
can be established from a viewpoint of the speed change characteristics, 
that the detecting means detects a hydraulic engaging element whose power 
transmission capability value is above a predetermined value and 
designates a transmission train that corresponds to the detected hydraulic 
engaging element, and that the transmission train determining means 
determines a transmission train to be established based on the 
transmission train designated by the detecting means and the transmission 
train or trains selected by the selecting means. 
If an arrangement is made such that, at the time of speed change judgement 
in which a transmission train or trains which are different from a 
presently established transmission train have been selected by the 
selecting means, if there is a coinciding transmission train that 
coincides with the transmission train designated by the detecting means 
among the selected transmission trains, the transmission train determining 
means determines the coinciding transmission train as a transmission train 
to be established, there are the following advantages. Namely, for 
example, when the running condition transfers, while running at the fifth 
speed at point A in FIG. 2, to point D to downshift to the third speed and 
then immediately transfers to point B, the transmission trains to be 
selected by the selecting means at point B will be the fourth speed train 
and the fifth speed train. On the other hand, since the hydraulic engaging 
element of the fifth speed is still short in time from the point of time 
of downshifting to the third speed, the hydraulic engaging element thereof 
is still high in power transmission capability value and, consequently, 
the fifth-speed transmission train is designated by the detecting means. 
The fifth speed train is thus determined to be the transmission train to 
be established by the transmission train determining means. According to 
this arrangement, the hydraulic engaging element for the fifth speed is 
quickly engaged through the hydraulic oil supply thereto. The duration of 
time in which the amount of power transmission is decreased becomes 
shorter than the case in which upshifting to the fourth speed is made at 
point B. As a result, the drivability is improved. 
At the time of speed change judgement for upshifting, if there are a 
plurality of coinciding transmission trains, it is preferable to determine 
a lowest speed transmission train among the coinciding transmission trains 
as a transmission train to be established. Further, at the time of speed 
change judgement for downshifting, if there are a plurality of coinciding 
transmission trains, it is preferable to determine a highest speed 
transmission train among the coinciding transmission trains as a 
transmission train to be established. 
It is preferable that the following arrangement be made, namely, at the 
time of speed change judgement in which transmission trains which are 
different from a presently established transmission train have been 
selected by the selecting means, if there is no transmission train 
coinciding with the transmission train that has been designated by the 
detecting means among the selected transmission trains and if the 
presently established transmission train or an intermediate transmission 
train between the presently established transmission train and the 
selected transmission train has been designated by the detecting means, 
the transmission train that has been designated by the transmission train 
determining means is determined as a transmission train to be established. 
Then, for example, if the running condition transfers, while running at 
the third speed at point D, to point A to thereby start upshifting to the 
fifth speed, and thereafter immediately transfers to point F, the 
transmission trains to be selected by the selecting means become the first 
speed train and the second speed train, and the transmission train to be 
designated by the detecting means becomes the third speed train. The 
transmission train to be established by the transmission train determining 
means is thus determined as the third speed train. Therefore, the time at 
which the amount of power transmission decreases becomes shorter than the 
case in which the downshifting to the second speed is made at point F. As 
a result, the drivability is improved. 
In this case, in order for a transmission train that is as close as 
possible to the transmission train to be selected by the selecting means, 
if, at the time of speed change judgement for upshifting, the designated 
transmission train is present in a plurality of numbers, it is preferable 
to determine a highest speed transmission train among the designated 
transmission trains as a transmission train to be established. Also, if, 
at the time of speed change judgement for downshifting, the designated 
transmission train is present in a plurality of numbers, it is preferable 
to determine a lowest speed transmission train among the designated 
transmission trains as a transmission train to be established. 
Furthermore, in order to prevent the deterioration of specific fuel 
consumption and overrunning of the engine, it is preferable to prohibit 
the determination of a lowest speed transmission train by the transmission 
train determining means as long as the selecting means has not selected 
the lowest speed transmission train of the transmission. 
By the way, the transmission train may be decided as described above by 
taking into consideration, the detected result of the detecting means from 
the beginning when the speed change judgement by the selecting means is 
made. In such an arrangement, however, even if the accelerator pedal is 
depressed while running, for example, at the fifth speed at point A to 
transfer to point D, thereby downshifting to the third speed to accelerate 
the vehicle, the transmission train to be designated, at the time of 
transferring to point D, by the detecting means becomes the fifth speed 
train. As a result, the transmission train to be established is determined 
to be the fifth speed and, therefore, can no longer be downshifted to the 
third speed. In this case, if an arrangement is made such that a 
transmission train to be established is determined based on the selected 
result of the selecting means until a predetermined time has lapsed from 
the time of speed change judgement by the selecting means, the third speed 
train that is selected by the selecting means at the time of speed change 
judgement by transferring to point D is determined as the transmission 
train to be established. It follows that downshifting can be made to the 
third speed as intended by a driver of the vehicle. 
Further, in the determination of the transmission train by considering the 
detected result of the detecting means, if a transmission train not 
selected by the selecting means has been determined as the transmission 
train to be established, it will be against the driver's intention if this 
transmission train is kept established for an undue period of time. Here, 
it is for the purpose of shortening the period of decreased amount of 
power transmission that the determination is made of the transmission 
train taking into consideration the detected result of the detecting 
means. Accordingly, if a substantial power transmission can be made by the 
determined transmission train, the determination of the transmission train 
by considering the detected result of the detecting means may be stopped. 
Therefore, it is preferable to stop the determination of a transmission 
train based on the detected result of the detecting means and the selected 
result of the selecting means at a predetermined time point (or timing) 
after the speed change judgement by the selecting means, e.g., after a 
lapse of a predetermined time from the time of speed change judgement or 
at a time when slipping of the hydraulic engaging element for the 
presently established transmission train through the determination as 
described above has decreased below a predetermined value and, instead, to 
determine the transmission train based on the selected result of the 
selecting means. Further, when speed changing for downshifting has been 
made before the lapse of a predetermined set time from the time of the 
speed change judgement, a longer time will be required, due to the 
increase in the engine load, before the hydraulic engaging element is 
engaged. Therefore, it is preferable to delay the timing of stopping the 
determination of the transmission train based on the detected result of 
the detecting means and the selected result of the selecting means. 
The power transmission capability value of the hydraulic engaging elements, 
which serves as a parameter in judging in the detecting means, may be a 
value corresponding to a hydraulic oil pressure that operates on the 
hydraulic engaging element or a value corresponding to a response time for 
the hydraulic engaging element to transfer to an engaged condition in 
which the driving power can be transmitted thereby. 
In this case, the hydraulic oil pressure of the hydraulic engaging elements 
may be actually detected by means of a hydraulic oil pressure sensor. 
However, since the hydraulic pressure increases with the lapse of time 
when the hydraulic oil is supplied to the hydraulic engaging element and 
decreases with the lapse of time when it is discharged, it may be so 
arranged that the power transmission capability value of the hydraulic 
engaging element is a value that increases with the lapse of time at a 
predetermined rate with respect to a hydraulic engaging element for a 
presently established transmission train, i.e., the hydraulic engaging 
element that is being supplied with the hydraulic oil at the present 
moment and is consequently transferring to the engaged condition or has 
already been engaged, and a value that decreases with the lapse of time at 
a predetermined rate with respect to a hydraulic engaging element for a 
transmission train that is not presently established, i.e., the hydraulic 
engaging element from which the hydraulic oil is being discharged and is 
consequently transferring to the non-engaged condition or has already been 
disengaged. According to this arrangement, it is advantageous in that the 
hydraulic oil pressure sensor becomes needless. By the way, since the 
hydraulic oil pressure in the hydraulic engaging elements does not rise 
above a basic pressure (supply pressure) of the hydraulic oil to be 
supplied to the hydraulic engaging elements and since the hydraulic oil 
pressure does not fall below atmospheric pressure, it is preferable to set 
an upper limit value and a lower limit value of the power transmission 
capability value that increases or decreases with the lapse of time. 
Further, in case there is provided hydraulic control means which controls 
a supply pressure of the hydraulic oil to be supplied to the hydraulic 
engaging elements, it is preferable to variably set the upper limit value 
according to a control condition of the hydraulic control means.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring to FIG. 1, numeral 1 denotes a transmission for effecting the 
changing or shifting of a vehicle speed to five forward speeds and one 
reverse speed. The transmission 1 is provided with a first input shaft 1a 
which is connected to an engine 2 via a fluid torque converter 3 having a 
clutch 3a, a second input shaft 1b which rotates synchronously with the 
first input shaft 1a, and an output shaft 1c which is connected to driving 
wheels 4 of a vehicle via a differential gear 5. Between the second input 
shaft 1b and the output shaft 1c there are parallelly provided first-speed 
and second speed forward transmission trains G1, G2. Between the first 
input shaft 1a and the output shaft 1c there are parallelly provided 
third-speed through fifth-speed forward transmission trains G3, G4, G5 and 
a reverse transmission train GR. In each of these forward transmission 
trains there is interposed a hydraulic engaging element in the form of 
first-speed through fifth-speed hydraulic clutch C1, C2, C3, C4, C5 so 
that each of the forward transmission trains can be selectively 
established through the engagement of each of the hydraulic clutches. The 
reverse transmission train GR is arranged to use the fifth-speed hydraulic 
clutch C5 in common with the fifth-speed transmission train G5. The 
fifth-speed transmission train G5 and the reverse transmission train GR 
can selectively be established by changing over a selector gear 6 on the 
output shaft 1c to the forward position on the left-hand side in FIG. 1 
and to the reverse position on the right-hand side therein. The second 
input shaft 1b is connected, via a gear, to the gear train of the 
third-speed transmission train on the input side of the third-speed 
hydraulic clutch C3 which is provided on the output shaft 1c, and 
synchronously rotates with the first input shaft 1a. 
In the first-speed transmission train G1 there is provided a one-way clutch 
7 which allows for over-rotation of the output side and which is 
interposed between the first-speed hydraulic clutch C1 and the first-speed 
gear train on the output side thereof. Further, inside the first-speed 
hydraulic clutch C1 there is assembled a first-speed holding hydraulic 
clutch CH which directly connects the output side thereof to the 
first-speed gear train. It is thus so arranged that the first-speed 
transmission train G1 can be established in a condition in which, through 
the engagement of this first-speed holding hydraulic clutch CH, the 
overrotation of the output side is not allowed, i.e., in a condition in 
which the engine brake can be applied. 
There are provided an electronic control circuit 9 which is made up of a 
microcomputer for receiving input signals from an engine sensor 8.sub.1 
which detects a throttle opening degree, a revolution speed, a cooling 
water temperature, or the like of the engine 2, a vehicle speed sensor 
8.sub.2 which detects the vehicle speed based on the revolution speed of 
the differential gear 5, revolution speed sensors 8.sub.3, 8.sub.4 which 
detect the revolution speeds of the input shaft and the output shaft of 
the transmission 1, and a position sensor 8.sub.5 which detects the 
position of an unillustrated shift lever, as well as a hydraulic control 
circuit 10 for controlling the above-described hydraulic clutches. It is 
thus so arranged that unillustrated solenoid valves, which are assembled 
into the hydraulic control circuit 10, can be controlled by the electronic 
control circuit 9 to effect the speed changing. 
In the electronic control circuit 9 there are stored mapped speed change 
characteristics, as shown in FIG. 2, which are represented by parameters 
of the throttle opening degree which is the engine load, and the vehicle 
speed. When the shift lever is changed over to the "D" range which is for 
automatic speed changing , a comparison is made between the speed change 
characteristics and the throttle opening degree as well as the vehicle 
speed at the present moment to carry out the following two treatments, 
i.e., a selecting treatment in which the transmission trains that can be 
established from the viewpoint of the speed change characteristics are 
selected and a detecting treatment in which the power transmission 
capability value at the present moment (the present power transmission 
capability value) of each of the first-speed through the fifth-speed 
hydraulic engaging elements is detected and in which transmission trains 
that correspond to the hydraulic engaging elements whose power 
transmission capability values are above a predetermined value are 
designated. The transmission train to be established is thus determined 
based on the selected result of the selecting treatment and the detected 
result of the detecting treatment, so that an appropriate automatic speed 
changing can be made depending on the running condition of the vehicle. 
In the selecting treatment, transmission trains of the lowest speed SL and 
the highest speed SH that can presently be established from the viewpoint 
of the speed change characteristics are selected. A comparison is also 
made between the transmission train that is presently established, i.e., 
the transmission train SO for which an order of establishing is presently 
being issued, and SL and SH. A tentative transmission train to be 
established next is called Smap. When SL=SH, i.e., when there is only one 
transmission train that can be established, that particular transmission 
train is selected. When SL.ltoreq.SO.ltoreq. SH, SO is selected and, when 
SO&lt;SL, SL is selected and, when SO&gt;SH, SH is selected, respectively. For 
example, when the running condition has transferred to point C while 
running at the fifth speed at point A in FIG. 2, the following applies, 
i.e., SL=the third speed, SH=the fifth speed and the Smap=the fifth speed. 
The power transmission capability value of each of the hydraulic clutches 
C1 through C5 is defined to be the value which corresponds to a response 
time in which the hydraulic clutch concerned transfers to a condition in 
which it is capable of transmitting the driving force. If a hydraulic oil 
pressure operating on a hydraulic clutch (i.e., a clutch pressure) is 
high, the response time for the hydraulic clutch to transfer to the 
condition of engagement becomes short and the power transmission 
capability value becomes high. In this case, the clutch pressure of each 
hydraulic clutch may be detected by a hydraulic oil pressure sensor, but 
it will result in a higher cost. Therefore, in the present embodying 
example, the following arrangement has been employed by taking note of the 
change, with the lapse of time, of the clutch pressure through supply and 
discharge of the hydraulic oil to and from the hydraulic clutch. Namely, 
the above-described detecting treatment is made based on a value which 
increases with the lapse of time with respect to the hydraulic clutch for 
the presently established transmission train SO, i.e., the hydraulic 
clutch that is being supplied with the hydraulic oil at the present moment 
and is consequently transferring to the engaged condition or has already 
been engaged, and based on a value which decreases with the lapse of time 
with respect to the hydraulic clutch for the transmission train that has 
not been established yet, i.e., the hydraulic clutch from which the 
hydraulic oil is being discharged and is consequently transferring to the 
non-engaged condition or has already been disengaged (the above-described 
values are hereinafter referred to as clutch pressure timers TC). 
The setting program for the clutch pressure timer TC is as shown in FIG. 3. 
At step X1, a discrimination or distinction is made as to whether the 
shift lever is duly in one of the changeover positions of "R" range for 
reverse running, "N" range for neutral, "D" range for automatic speed 
changing, "2" range for the second speed holding and "1" range for the 
first speed holding. If the shift lever is duly in one of the 
above-described positions, a discrimination is made at steps X2, X3 and X4 
as to whether the range is in the "N" range or not, whether the range is 
in the "R" range or not, and whether the range is in the forward "D", "2" 
or "1" range or not, respectively. If the shift lever is in an 
intermediate indefinite position between the respective changeover 
positions or in the "N" range, the program proceeds to step X5 to thereby 
decrease, with the lapse of time, the clutch pressure timers TC1-TC5 for 
the first speed through the fifth speed at a predetermined rate of 
.DELTA.TCd. 
When the shift lever is in the "R" range, the reverse transmission train GR 
is established by supplying the hydraulic oil to the fifth-speed hydraulic 
clutch C5. Therefore, at step X6, the fifth-speed clutch pressure timer 
TC5 is increased with the lapse of time at a predetermined rate of 
.DELTA.TCu and, also, the first-speed through the fourth-speed clutch 
pressure timers TC1-TC4 are decreased with the lapse of time at the 
predetermined rate of .DELTA.TCd. 
When the shift lever is in the forward running "D", "2" or "1" range, the 
first-speed hydraulic clutch C1 is always supplied with the hydraulic oil. 
Therefore, at step X7, the first-speed clutch pressure timer TC1 is 
increased with the lapse of time at the predetermined rate of .DELTA.TCu. 
Thereafter, the program proceeds to step X8 to discriminate whether the 
presently established transmission train SO is the second speed or not. If 
SO=the second speed, the third-speed through the fifth-speed clutch 
pressure timers TC3-TC5 are decreased with the lapse of time at the 
predetermined rate of .DELTA.TCd at step X9. If SO.noteq.the second speed, 
the second-speed pressure timer TC2 is similarly decreased at step X10 
and., also, the program proceeds to step X11, where a discrimination is 
made as to whether SO is the third speed or not. If SO=the third speed, 
the program proceeds to step X12, where the fourth-speed and the 
fifth-speed clutch pressure timers TC4, TC5 are similarly decreased. If 
SO.noteq.the third speed, the third-speed clutch pressure timer TC3 is 
similarly decreased at step X13 and, also, the program proceeds to step 
X14, where a discrimination is made as to whether SO is the fourth speed 
or not. If SO=the fourth speed, the fifth-speed clutch pressure timer TC5 
is similarly decreased at step X15. If SO.noteq.the fourth speed, the 
fourth-speed clutch pressure timer TC4 is similarly decreased at step X16 
and, also, the program proceeds to step X17, where a discrimination is 
made as to whether SO is the fifth speed or not. If SO.noteq.the fifth 
speed, the fifth-speed clutch pressure timer TC5 is similarly decreased at 
step X18. 
In this manner, the clutch pressure timers for the transmission trains that 
have not presently been established are decreased with the lapse of time 
at the predetermined rate of .DELTA.TCd. Thereafter, the program proceeds 
to step X19, where a discrimination is made as to whether SO is the first 
speed or not. If SO.noteq.the first speed, a clutch pressure timer TCn 
which corresponds to the transmission train SO is selected at step X20 
and, at step X21, the clutch pressure timer Tcn is increased with the 
lapse of time at the predetermined rate of .DELTA.TCu. The clutch pressure 
does not rise above a basic pressure (supply pressure) of the hydraulic 
oil to be supplied to the hydraulic clutches. Therefore, an upper limit 
value TCmax corresponding to the supply pressure is defined, and a 
comparison is made at step X22 between TCn and. TCmax. If 
TCn.gtoreq.TCmax, TCn is re-written to TCmax at step X23. 
By the way, there is a case in which the hydraulic control circuit 10 is 
provided with a hydraulic control valve (not illustrated) which is 
controlled by the electronic control circuit 9 to variably change, by the 
control valve, the supply pressure of the hydraulic oil to the hydraulic 
clutches depending on the throttle valve opening degree or the like. In 
such a case, the above-described upper limit value TCmax is variably set 
by deriving the supply pressure from an order value to the hydraulic 
control valve. Further, there is a case in which, during the transient 
period of speed changing, pressure rise characteristics of the clutch 
pressure are feedback-controlled based on revolution speed parameters such 
as a ratio of revolution speeds of the input shaft and the output shaft of 
the transmission, a rate of change in revolution speed of the input shaft, 
or the like. At the time of this feedback control, the rate of increase 
.DELTA.TCu of TCn is made to be variable depending on the pressure 
increase characteristics of the clutch pressure. 
An upper limit value is also set against the increase in the fifth-speed 
clutch pressure timer TC5 at step X6 and the increase in the first-speed 
clutch pressure timer TC1 at step X7. On the other hand, against the 
decrease in the clutch pressure timer in each of the steps X5, X6, X9, 
X10, X12, X13, X15, X16 and X18, a value corresponding to atmospheric 
pressure, e.g., zero, is set as a lower limit value. 
As in the above-described manner, the clutch pressure timer TC1-TC5 for 
each of the hydraulic clutches C1-C5 is set. In the above-described 
detecting treatment, the hydraulic clutch or clutches whose clutch 
pressure timer or timers are above a predetermined value TCs are detected 
and transmission train or trains STC corresponding to those hydraulic 
clutches are designated. 
FIG. 4 shows a program for deciding a transmission train to be effected in 
the "D" range. First, at step Y1, reading is made of the above-described 
SL, SH, Smap that were selected in the selecting treatment and the 
above-described STC that was designated in the detecting treatment. Then, 
at step Y2, a discrimination is made as to whether or not a timer time TM 
of a speed change timer of subtraction type has become smaller than a 
predetermined first setting time TM1. If TM&gt;TM1, the transmission train S 
to be established next is determined at step Y3 to be the transmission 
train of Smap. If TM.ltoreq.TM1, a discrimination is made at step Y4 as to 
whether TM has become smaller than a second setting time TM2 which is set 
to a value smaller than the first setting time TM1. If TM.ltoreq.TM2, the 
transmission train S to be established next is determined at step Y5 to be 
the presently established transmission train SO. 
The timer time TM of the speed change timer is set to an initial value TMS 
(TMS&gt;TM1) at the time of speed change judgement when, at the time of TM=0, 
Smap has become a transmission train other than SO, and when the shift 
lever has been changed over from an indefinite position to any of the 
changeover positions. The timer time TM is reset to 0 when a condition of 
TM=TM2 has occurred, and it is further set again to TM1 when, at the time 
of TM1&gt;TM&gt;TM2, a speed changing of downshifting is effected. Furthermore, 
a slip ratio ECL of the hydraulic clutch for the present transmission 
train is obtained from the revolution speed Nin of the first input shaft, 
the revolution sped Nout of the output shaft of the transmission 1, and 
the gear ratio r of the present transmission train by the following 
formula (ECL=1 when the hydraulic clutch is completely engaged): 
EQU ECL=r.times.Nout.div.Nin 
If ECL falls within a predetermined region close to 1 for a certain period 
of time t at the time of TM1&gt;TM&gt; TM2, a judgement is made to be the 
completion of the speed changing, and TM is then reset to 0 even if 
TM&gt;TM2. 
If TM1&gt;TM&gt;TM2, a determination of the transmission train is made, as 
hereinbelow described, based on Smap, SL, SH and STC. In the "D" range, 
however, the first-speed clutch pressure timer TC1 always: exceeds the 
predetermined value TCs as described above, with the result that STC 
always includes the first speed. Consequently, the frequency at which the 
transmission train S to be established is determined to be the first speed 
becomes so high that a disadvantage occurs: in that the specific fuel 
consumption becomes poor. Therefore, at step Y6, a treatment is made first 
to remove the first speed from STC. Then, a discrimination is made at step 
Y7 as to whether the present transmission train SO and Smap coincides with 
each other. If SO=Smap, the transmission train S to be established next is 
determined to be the present transmission train SO at step Y5. If 
SO.noteq.Smap, a discrimination is made at step Y8 as to whether there is 
STC or not. If there is no STC, the program proceeds to step Y5 similarly 
as above to make S=SO. If there is or are STC, a discrimination is made at 
step S9 as to whether there is in STC a transmission train coinciding with 
Smap. If there is one, the program proceeds to step Y3 to make S=Smap and, 
if there is none, a discrimination is made at step Y10 as to whether there 
is in STC a transmission train within a range equal to or above SL and 
equal to or below SH. If there is one, a comparison is made at step Y11 
between SO and Smap to discriminate whether to upshift or to downshift. If 
a discrimination of upshifting has been made when SO&lt;Smap, the program 
proceeds to step Y12, and a treatment of S=STCmin is made, where STCmin is 
the lowest speed transmission train among STC which are equal to or above 
SL and equal to or below SH. If a discrimination of downshifting has been 
made at step Y11 when SO.gtoreq.Smap, the program proceeds to step Y13, 
and a treatment of S=STCmax is made, where STCmax is the highest speed 
transmission train among STC which are equal to or above SL and equal to 
or below SH. 
If there is no such transmission train among STC as is equal to or above SL 
and equal to or below SH, a comparison is made at step Y14 between SO and 
Smap. If a discrimination of upshifting has been made when SO&lt;Smap, the 
program proceeds to step Y15 to discriminate as to whether there is such a 
transmission train among STC as is equal to or above SO and equal to or 
below Smap. If there is none, a treatment is made to make S=SO at step Y5. 
If there is one, the program proceeds to step Y16 and a treatment is made 
to make S=STC max, where STCmax is the highest speed transmission train 
among STC which are equal to or above SO and equal to or below Smap. If a 
discrimination of downshifting has been made when SO.gtoreq. Smap, the 
program proceeds to step Y17 and a discrimination is made as to whether 
there is such a transmission train among STC as is equal to or above Smap 
and equal to or below SO. If there is none, a treatment is made at step Y5 
to make S=SO. If there is one, the program proceeds to step Y18 and a 
treatment is made to make S=STCmin, where STCmin is the lowest speed 
transmission train among STC which are equal to or above Smap and equal to 
or below SO. 
An explanation will now be made, with reference to FIG. 5, about the speed 
changing by the above-described discriminating treatment. When the running 
condition transfers to point D while running at the fifth speed at point A 
in FIG. 2, since SL=SH=Smap=the third speed at point D, a condition of 
SO.noteq.Smap occurs, as a result of which TM is set to TMS. While TM&gt;TM1, 
the program proceeds from step Y2 to step Y3 to make S=the third speed, 
thereby downshifting from the fifth speed to the third speed. When a 
condition of TM1.gtoreq.TM&gt;TM2 occurs, as long as the running continues at 
point D, the program proceeds from step Y7 to step Y5, thereby maintaining 
the vehicle speed to the third speed. However, when the running condition 
transfers from point D to point B and a condition occurs in which 
SL=Smap=the fourth speed and SH=the fifth speed, a discrimination is made 
at step Y7 that SO.noteq.Smap, and the program proceeds to step Y8 to make 
a discrimination as to whether there is STC or not. Since TC3 and TC5 
respectively exceed the predetermined value TCs in a condition shown in 
FIG. 5, the third speed and the fifth speed are designated as STC. The 
program proceeds from step Y8 to step Y10 via step Y9. In this case, since 
STC=SH=the fifth speed, the program proceeds to step Y11, where a 
discrimination is made that SO&lt;Smap and proceeds to step Y12. In this 
case, since the STC that satisfies the condition of 
SL.ltoreq.STC.ltoreq.SH is only the fifth speed, STCmin=the fifth speed. 
Therefore, as a result of S=the fifth speed, an upshifting is effected 
from the third speed to the fifth speed. Then, as a result of a 
discrimination in the above-described selecting treatment that SH=SO=the 
fifth speed, Smap becomes the fifth speed. At step Y7, a discrimination is 
made that SO=Smap, and the program proceeds to step Y5, where the vehicle 
speed is maintained to the fifth speed. 
If Smap changes in the order of the fifth speed, the third speed and the 
fourth speed as described above, a speed changing was conventionally made 
by downshifting from the fifth speed to the third speed and subsequently 
upshifting from the third speed to the fourth speed. In this arrangement, 
however, the amount of power transmission decreases until the hydraulic 
engaging element C4 for the fourth speed has come into substantial 
engagement after downshifting to the third speed, followed by upshifting 
to the fourth speed. The duration of time of decreased amount of power 
transmission thus becomes long and the drivability becomes poor. On the 
contrary, according to the above-described embodying example, even if Smap 
is the fourth speed, upshifting is effected to the fifth speed that is 
designated as STC and that can be established from the viewpoint of speed 
change characteristics. Here, since the hydraulic clutches for the 
transmission trains that are designated as STC come into engagement with a 
good response, the period of decreased power transmission can be shortened 
and the drivability is improved. 
The above-described discriminating treatments are repeated until a 
condition of TM=TM2 occurs. Even in case TM&gt;TM2, if ECL falls within a 
predetermined region near 1 continuously for a predetermined period of 
time t, TM is reset to 0 by judging that the speed changing has 
substantially been completed. Therefore, next time, a discrimination is 
made at step Y4 that TM.ltoreq.TM2 and the program proceeds to step Y5, so 
that the vehicle speed is maintained to the fifth speed as long as the 
vehicle runs at point B. 
Thereafter, when the running condition transfers from point B to point E, 
since SL=the second speed and SH=Smap=the third speed at point E, a 
condition of SO.noteq. Smap occurs and TM is set again to TMS. While 
TM&gt;TM1, the program will proceed from step Y2 to step Y3 so as to make 
S=Smap=the third speed, thereby downshifting from the fifth speed to the 
third speed. If the vehicle is kept running at point E, while 
TM1.gtoreq.TM&gt;TM2, the program will proceed from step Y7 to step Y5. When 
a condition of TM.ltoreq.TM2 has occurred, the program will proceed from 
step Y4 similarly to step Y5, thereby holding the vehicle speed to the 
third speed. 
Then, when the running condition transfers: from point E to point A to 
attain a condition of SL=SH=Smap=the fifth speed, TM is again set to TMS. 
While TM&gt;TM1, the program will proceed from step Y2 to step Y3 to attain a 
condition of S=Smap=the fifth speed, thereby upshifting from the third 
speed to the fifth speed. If the running condition transfers from point A 
to point F during the time of TM1.gtoreq.TM&gt;TM2 and while TC3 is above TCs 
to thereby attain a condition of SL=the first speed and SH=Smap=the second 
speed, a discrimination is made at step S7 that SO.noteq.Smap. The program 
then proceeds to step S8, where a discrimination is made that there is STC 
(STC=the third speed, the fifth speed). The program proceeds to Y18 via 
steps of Y9, Y10, Y14 and Y17 to become S=STCmin=the third speed, thereby 
downshifting from the fifth speed to the third speed. Next time, a 
condition of SO=the third speed occurs, but since Smap is the second 
speed, the program proceeds from step Y7 to step Y18 via steps Y8, Y9, 
Y10, Y14 and Y17, thereby holding the vehicle speed to the third speed. By 
the way, when a downshifting is effected, the engine is in a highload 
condition due to the depression of the accelerator pedal. It follows that, 
even if the downshifting has been made to a transmission train that is 
designated as STC, when the difference between TM and TM2 is short, a 
condition of TM=TM2 may occur before the hydraulic engaging element of 
this transmission train has obtained an engaging force. Therefore, when a 
speed changing of downshifting is made while TM1.gtoreq.TM&gt;TM2, TM is set 
again to TM1 as described above so that enough time can be secured for 
establishing the transmission train of STC. 
When ECL continuously falls within a predetermined range near 1 for a 
certain period of time t or a condition of TM=TM2 occurs with the result 
that TM is reset to 0, the program proceeds from step Y4 to step Y5 to 
become S=SO=the third speed. However, if the vehicle is kept running at 
point F, a condition of SO.noteq.Smap occurs because Smap=the second 
speed, with the result that TM is set again to TMS. Next time, the program 
proceeds from step Y2 to step Y3 to become S=Smap=the second speed, 
thereby downshifting from the third speed to the second speed. A strong 
acceleration by the second transmission train can therefore be obtained as 
according to the speed change characteristics. 
In the above-described embodying example, SL, SH and Smap have been 
arranged to be selected according to the speed change characteristics to 
be defined with the throttle opening degree and the vehicle speed as 
parameters. The present invention can also be applied to a case in which 
the speed change characteristics are corrected or Smap is changed based on 
an acceleration, the speed of depressing the accelerator pedal, running 
resistance or the like. 
As can be seen from the above description, according to the present 
invention, the conditions of the hydraulic engaging elements are detected 
and the transmission train is determined by taking into consideration the 
results of this detection. The speed changing is thus made to the 
transmission train that can be established with a good response. 
Therefore, the period of time of decreased amount of power transmission 
can be shortened to the smallest possible and the drivability can be 
improved. 
It is readily apparent that the above-described control apparatus for a 
hydraulically operated vehicular transmission meets all of the objects 
mentioned above and also has the advantage of wide commercial utility. It 
should be understood that the specific form of the invention hereinabove 
described is intended to be representative only, as certain modifications 
within the scope of these teachings will be apparent to those skilled in 
the art. 
Accordingly, reference should be made to the following claims in 
determining the full scope of the invention.