System and method for the control of shifting of vehicle automatic transmission

This invention relates to a shift control system and method for a vehicle automatic transmission, in which control of a downshift on a downhill road is performed by fuzzy inference. When a vehicle has been determined to be running on a downhill road by a driving state determining device, a speed range setting device sets as an optimal speed range a speed range lower than a current speed range. In the automatic transmission, the state of engagement of a desired engaging element is changed over to achieve the optimal speed range. When the vehicle has been determined to be running on the downhill road by the driving state determining device so that the speed range lower than the current speed range has been set as the optimal speed range and also when no change has been determined in engine load by an engine load detecting device, an engagement state control device reduces engaging force to be produced upon changing over the state of engagement of a desired engaging element for achieving the optimal speed range. This makes it possible to eliminate a sense of incogruity, which would otherwise occur upon shifting to a higher speed range, while assuring a good shifting response.

BACKGROUND OF THE INVENTION 
a) Field of the Invention 
This invention relates to a system and method for the control of shifting 
of a vehicle automatic transmission, in which upon setting, for example, a 
normal speed range corresponding to a vehicle speed and an engine load, 
the control of the shifting is performed incorporating setting of the 
speed range by fuzzy inference on the basis of information on running 
state of a vehicle, information on driving behavior intended by a driver 
for the vehicle, information on conditions of a road on which the vehicle 
is running, and the like. In particular, this invention is concerned with 
a system and method for the control of shifting of a vehicle automatic 
transmission, which are designed to perform most suitable control of a 
downshift on a downhill road. 
b) Description of the Related Art 
A conventional vehicle automatic transmission suitable for use on an 
automotive vehicle is designed to perform a change-over in speed range 
such as an upshift or a downshift on the basis of a preset shift pattern 
upon receipt of information on an engine load such a throttle opening, 
information on a vehicle speed and information on a current speed range. 
Such a conventional vehicle automatic transmission involves no particular 
serious problem in shifting the speed range on a flat road as in street 
running, whereby the shifting is smooth and gives no sense of incongruity. 
When running, for example, in a mountainous region, however, there are 
straight uphill roads and also frequently bent uphill roads as well as 
downhill slopes requiring a strong engine brake and gentle long downhill 
slopes. There are also drivers who abruptly accelerate their vehicles on a 
downhill slope and apply a strong brake immediately entering a corner. 
While running in such a mountainous region, it is rather difficult to 
choose a speed range optimal to the state of running of the vehicle, the 
driving behavior intended by the driver, road conditions and the like. 
There is accordingly a demand for permitting good control of motion of a 
vehicle by a simple running operation even during running in a mountainous 
region so that better drive feeling and run feeling can be obtained. 
For such a demand, it is known, for example, from Japanese Patent 
Application Laid-Open (Kokai) No. SHO 62-246546 or HEI 2-3738 to perform 
the so-called "fuzzy control" so that an optimal speed range corresponding 
to the above-described state of running of the vehicle can be selected. 
These conventional shift control methods are designed to set optimal speed 
ranges by inferring all gear positions for running in both urban and 
mountainous regions in accordance with fuzzy inference. These conventional 
shift control methods making use of "fuzzy control" are however 
accompanied by the problem that they require many rules and hence a 
membership function of an intricate profile. This has led to the problems 
that a large-capacity computer is needed to put such a method into 
practical application and tuning of the control is difficult, thereby 
making it difficult to apply the control method to other types of 
automotive vehicles. 
Further, additional incorporation of shift control by "fuzzy control" may 
result in the execution of shifting by such a small change in the running 
or driving state, e.g., running-over of a small bump or slight depression 
of an accelerator pedal that no shifting would take place according to the 
conventional art. This has led to the problem that the above shifting may 
give a sense of incongruity to drivers who are accustomed to running on 
flat roads such as street running under control by a conventional 
automatic transmission. 
With a view to overcoming these problems, a shift control method was 
proposed in Japanese Patent Application Laid-Open (Kokai) No. HEI 
2-212655. According to this shift control method, various parameters 
indicating the state of running of a vehicle are detected so that 
detection signals are produced. Based on the detection signals and a 
membership function set beforehand, fuzzy inference is conducted to 
determine the degree of running resistance. When this running resistance 
is greater than a predetermined value, a shift map for high-load running 
is selected in place of a shift map for normal running so that a speed 
range is determined by the shift map for high-load running. 
According to this proposal, the same shift map is used for both straight 
uphill roads and frequently bent uphill roads, leading to the problem that 
carefully thought-out shift control can be hardly conducted to sufficient 
extents in the light of the above-mentioned various road conditions in 
mountainous regions and also intended driving behaviors. If the shift map 
for normal running is changed over to the shift map for high-load running 
based solely upon the occurrence of running resistance greater than the 
predetermined value and a speed range is then set in accordance with the 
latter map, the speed range so selected in accordance with the shift map 
for high-load running may become higher than the speed range which has 
been selected by the shift map for normal running. There is hence the 
potential problem that a sense of incongruity may be given to the driver. 
A still further shift control method was hence proposed as disclosed in 
Japanese Patent Application Laid-Open (Kokai) No. HEI 4-337157. According 
to this shift control method, an optimal speed range is selected based on 
a normal shift pattern set beforehand and in addition, an optimal speed 
range is also selected by fuzzy inference on the basis of at least one of 
information on the state of operation of a vehicle, information on driving 
behavior intended by a driver and information on road conditions. The 
optimal speed range selected based on the normal shift pattern is usually 
set as a speed range for an automatic transmission but only when the 
optimal speed range selected by the fuzzy inference is lower than the 
optimal speed range selected based on the normal shift pattern, the 
optimal speed range selected by the fuzzy inference is set as a speed 
range for the automatic transmission. 
Among such shift control methods making use of "fuzzy control" as mentioned 
above, those designed to perform setting of a speed range by fuzzy 
inference instead of setting of a speed range according to shifting 
characteristics for normal running as needed--as disclosed, for example, 
in Japanese Patent Applications Laid-Open Nos. HEI 4-337157 and 
2-212655--may select by fuzzy inference a speed range lower than a speed 
range--which would otherwise be selected according to shifting 
characteristics for normal running--for example, on a downhill road to 
obtain a necessary engine brake, and may then set it as a speed range for 
an automatic transmission. 
In this case, the downshift operation for obtaining the engine brake may 
give a sense of incongruity to the driver. 
According to shift control by shifting characteristics for normal running, 
a downshift or an upshift is performed, for example, based on vehicle 
speed information and engine load (throttle opening) information while 
using such a map as shown in FIG. 20. In this shift map, the solid line a 
is an upshift line from 3rd speed to 4th speed while the alternate long 
and short dash line b is a downshift line from 4th speed to 3rd speed. 
If the driver operates a throttle valve (in other words, depresses an 
accelerator pedal) to point B when the vehicle speed and the throttle 
opening are as indicated by point A, a downshift operation is performed 
after passing across the downshift line b, that is, at point C. This 
downshift operation is generally accompanied by a shift shock, which 
becomes larger especially where importance is placed on its response 
characteristic. The driver however can expect the shift shock in this case 
so that he does not feel a sense of incongruity upon shifting. 
Further, the vehicle speed may increase from point A to point D in some 
instances even when the throttle opening is kept unchanged (in other 
words, even when the driver does not change the amount of depression of 
the accelerator pedal). If the vehicle is running on a flat road at this 
time, the vehicle speed increases passing across the upshift line a as 
illustrated in the diagram so that an upshift operation is performed. If 
the vehicle is running on a downhill road, however, a downshift from 3rd 
speed to 2nd speed may be commanded instead to obtain an engine brake as a 
result of selection of a speed range by fuzzy inference. As a consequence, 
a downshift operation is performed. 
The driver cannot foresee the downshift in the above case, so that a shift 
shock produced as a result of the downshift operation gives a surprise to 
the driver. The driver feels a sense of substantial incongruity at the 
time of the shifting especially in a shifting operation which places 
importance on the response characteristic and produces a large shock. This 
leads to the problem that the smoothness of a shifting operation which is 
an inherent characteristic feature to an automatic transmission will be 
lost. 
SUMMARY OF THE INVENTION 
The present invention has been completed in view of the above-described 
problems. An object of this invention is therefore to provide a system and 
method for the control of shifting of a vehicle automatic transmission, 
which while permitting a downshift by fuzzy inference to obtain an engine 
brake in the course of running on a downhill road, can assure smoothness 
of a shifting operation by reducing a shift shock at the time of the 
downshift. 
To achieve the above object, the present invention provides the following 
system and method for the control of shifting of a vehicle automatic 
transmission: 
(A) 
A shift control system for a vehicle automatic transmission in which 
desired one of plural speed ranges is achieved by selectively changing 
over the state of engagement of plural engaging elements, comprising: 
means for detecting a load on an engine which outputs drive power to the 
automatic transmission, thereby, determining the state of loading on the 
engine; 
means for determining the state of driving of a vehicle by fuzzy inference; 
means for setting an optimal speed range out of the plural speed ranges on 
the basis of the results of the determination by the driving state 
determining means; and 
means for selectively controlling the state of engagement of the plural 
engaging elements, wherein 
said speed range setting means is provided with means for setting as the 
optimal speed state a speed range lower than a current speed range when 
the vehicle has been determined to be running on a downhill road by said 
driving state determining means; and 
said engagement state control means is provided with means for reducing an 
engaging force to be produced upon changing over the state of engagement 
of a desired engaging element for achieving the optimal speed range when 
the vehicle has been determined to be running on the downhill road by said 
driving state determining means so that the speed range lower than the 
current speed range has been set as the optimal speed range and also when 
no change has been determined in the engine load by said engine load 
detecting means. 
The system (A) may include the following optional features: 
(A-1) 
The system (A) may further comprise means for detecting a speed of the 
vehicle, wherein said speed range setting means comprises: 
first speed range setting means for setting the optimal speed range on the 
basis of the engine load and vehicle speed detected by said engine load 
detecting means and said vehicle speed detecting means, respectively; 
second speed range setting means for setting, as the optimal speed range, 
the speed range lower than the current speed range when the vehicle has 
been determined to be running on the downhill road by said driving state 
determining means; and 
speed range determining means for comparing the optimal speed range set by 
said first speed range setting means with the optimal speed range set by 
said second speed range setting means and choosing the optimal speed range 
set by said second speed range setting means only when the optimal speed 
range set by said second speed range setting means is lower than the 
optimal speed range set by said first speed range setting means. 
(A-2) 
In the system (A), said engine load is indicated by an opening of a 
throttle valve or the rate of a change in the opening of the throttle 
valve or the amount of depression of an accelerator pedal or the rate of a 
change in the amount of depression of the accelerator pedal; and said 
engine load detecting means determines no change in the engine load when 
the opening of the throttle valve or the rate of the change in the opening 
of the throttle valve or the amount of depression of the accelerator pedal 
or the rate of the change in the amount of depression of the accelerator 
pedal is not greater than a predetermined value. 
(A-3) 
In the system (A), said engaging elements are hydraulic engaging elements 
selectively actuated by hydraulic pressure; and said engagement state 
control means controls the state of engagement of each of said hydraulic 
engaging elements by controlling hydraulic pressure to be fed to said 
hydraulic engaging element. 
(A-4) 
In the system (A) including the features (A-3), said engagement state 
control means is equipped with a first hydraulic pressure feeding pattern 
for feeding, during a change-over of the speed range, a hydraulic pressure 
of a predetermined value to the corresponding hydraulic engaging element 
and a second hydraulic pressure feeding pattern for feeding, during the 
change-over of the speed range, a hydraulic pressure of a value lower than 
the predetermined value to the corresponding hydraulic engaging element; 
and when the vehicle has been determined to be running on the downhill 
road by said driving state determining means and also when no change has 
been determined in the engine load by said engine load detecting means, 
said engagement state control means controls the engagement force of the 
desired hydraulic engaging element for achieving the optimal speed range 
on the basis of the second hydraulic pressure feeding pattern. 
(B) 
A method for controlling a shift of a vehicle automatic transmission in 
which desired one of plural speed ranges is achieved by selectively 
changing over the state of engagement of plural engaging elements, 
comprising the following steps: 
detecting a load on an engine which outputs drive power to the automatic 
transmission, thereby determining the state of loading on the engine; 
determining the state of driving of a vehicle by fuzzy inference; 
setting an optimal speed range out of the plural speed ranges on the basis 
of the results of the determination by the driving state determining 
means; and 
selectively controlling the state of engagement of the plural engaging 
elements, wherein 
said speed range setting step comprises setting as the optimal speed state 
a speed range lower than a current speed range when the vehicle has been 
determined to be running on a downhill road in said driving state 
determining step; and 
said engagement state control step comprises reducing an engaging force to 
be produced upon changing over the state of engagement of a desired 
engaging element for achieving the optimal speed range when the vehicle 
has been determined to be running on the downhill road in said driving 
state determining step so that the speed range lower than the current 
speed range has been set as the optimal speed range and also when no 
change has been determined in the engine load in said engine load 
detecting step. 
The above method (B) may include the following optional features: 
(B-1) 
The above method (B) may further comprises a step of detecting a speed of 
the vehicle, wherein said speed range setting step comprises: 
a first speed range setting step of setting the optimal speed range on the 
basis of the engine load and vehicle speed detected in said engine load 
detecting step and said vehicle speed detecting step, respectively; 
a second speed range setting step of setting, as the optimal speed range, 
the speed range lower than the current speed range when the vehicle has 
been determined to be running on the downhill road in said driving state 
determining step; and 
a speed range determining step for comparing the optimal speed range set in 
said first speed range setting step with the optimal speed range set in 
said second speed range setting step and choosing the optimal speed range 
set in said second speed range setting step only when the optimal speed 
range set in said second speed range setting step is lower than the 
optimal speed range set in said first speed range setting step. 
(B-2) 
In the method (B), said engine load is indicated by an opening of a 
throttle valve or the rate of a change in the opening of the throttle 
valve or the amount of depression of an accelerator pedal or the rate of a 
change in the amount of depression of the accelerator pedal; and said 
engine load detecting step determines no change in the engine load when 
the opening of the throttle valve or the rate of the change in the opening 
of the throttle valve or the amount of depression of the accelerator pedal 
or the rate of the change in the amount of depression of the accelerator 
pedal is not greater than a predetermined value. 
(B-3) 
In the method (B), said engaging elements are hydraulic engaging elements 
selectively actuated by hydraulic pressure; and said engagement state 
control step controls the state of engagement of each of said hydraulic 
engaging elements by controlling hydraulic pressure to be fed to said 
hydraulic engaging element. 
(B-4) 
In the method (B) including the feature (B-3), the control in said 
engagement state control step uses a first hydraulic pressure feeding 
pattern for feeding, during a change-over of the speed range, hydraulic 
pressure of a predetermined value to the corresponding hydraulic engaging 
element and a second hydraulic pressure feeding pattern for feeding, 
during the change-over of the speed range, a hydraulic pressure of a value 
lower than the predetermined value; and when the vehicle has been 
determined to be running on the downhill road in said driving state 
determining step and also when no change has been determined in the engine 
load in said engine load detecting step, said engagement state control 
step controls the engagement force of the desired hydraulic engaging 
element for achieving the optimal speed range on the basis of the second 
hydraulic pressure feeding pattern. 
Since the method (B) and its optional features (B-1 to B-4) are similar in 
operation and advantages to the system (A) and its optional features (A-1 
to A-4), the operation and advantages of the system and its optional 
features will hereinafter be described and those of the method will be 
omitted herein. 
System (A) and Method (B) 
When the vehicle has been found to be running on a downhill road by the 
driving state determining means, the speed range setting means sets as an 
optimal speed range a speed range lower than a current speed range and in 
the automatic transmission, the state of engagement of a desired engaging 
element is changed over to achieve this optimal speed range. Further, when 
the vehicle has been found to be running on a downhill road by the driving 
state determining means and the speed range lower than the current speed 
range has been set as the optimal speed range as described above and 
further when no change has been found to exist in the engine load by the 
engine load detecting means, the engagement state control means reduces an 
engaging force to be produced upon changing over the state of engagement 
of the desired engaging element for achieving the optimal speed range 
If the driver wishes acceleration by depressing the accelerator pedal while 
the vehicle is running on a downhill road, the engine load increases so 
that control to reduce an engaging force upon changing over the state of 
engagement of engaging elements is not performed. As a result, the speed 
range is shifted to a low speed range by an ordinary high engaging force, 
whereby the shifting is achieved promptly. 
Where the driver, for example, does not additionally depress the 
accelerator pedal while the vehicle is running on a downhill road, control 
is performed to reduce an engaging force to be produced upon changing over 
the state of engagements of engaging elements because the engine load 
remains unchanged. As a consequence, the speed range is changed over to a 
low speed range by a low engaging force. This downshift can therefore be 
achieved without developing a shift shock. 
It is therefore possible to eliminate a sense of incongruity at the time of 
shifting while assuring a good shift response. Further, the smoothness of 
a shifting operation, which is an inherent advantageous feature to an 
automatic transmission, can be retained. It is therefore possible to 
improve the drive feeling and further, the riding comfort. 
Optional features (A-1) and (B-1) 
According to the speed state setting means, the first speed range setting 
means sets an optimal speed range on the basis of an engine load and a 
vehicle speed detected by the engine load detecting means and the vehicle 
speed detecting means, respectively, and when the vehicle is determined to 
be running on a downhill road by the driving state determining means, the 
second speed range setting means sets the speed range at an optimal speed 
range lower than the current speed range. 
The optimal speed range set by the first speed range setting means and the 
optimal speed range set by the second speed range setting means are then 
compared by the speed range setting means, and only when the latter 
optimal speed range is lower than the former optimal speed range, the 
latter optimal speed range is selected. 
This has made it possible to simplify the shift control, thereby realizing 
stable shift control. 
Optional features (A-2) and (B-2) 
When the opening of the throttle valve or the rate of the change in the 
opening of the throttle valve or the amount of depression of the 
accelerator pedal or the rate of the change in the amount of depression of 
the accelerator pedal is not greater than a predetermined value, the 
engine load is determined to have remained unchanged. This makes it 
possible to easily and surely estimate the absence of any change in the 
engine load, in other words, the absence of an acceleration intended by 
the driver, so that the elimination of a sense of incongruity at the time 
of shifting can be adequately attained while retaining a good shift 
response. 
Optional features (A-3) and (B-3) 
The use of the hydraulic engaging elements as the engaging elements has 
made it possible to easily perform the control of the state of engagement 
(for example, an engaging force). 
Optional features (A-4) and (B-4) 
When the vehicle has been determined to be running on a downhill road by 
the driving state determining means and the engine load has been 
determined to have remained unchanged by the engine load detecting means, 
the engagement state control means controls an engaging force for each 
desired hydraulic engaging element, which is to be actuated to achieve the 
above optimal speed range, on the basis of the second hydraulic pressure 
feeding pattern which feeds a hydraulic pressure lower than a hydraulic 
pressure by the first hydraulic pressure feeding pattern. 
This has simplified the control of an engaging force upon change-over of 
the speed range, thereby realizing stable shift control.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENT 
With reference to the accompanying drawings, the shift control system and 
method according to one embodiment of the present invention will 
hereinafter be described. 
Outline construction of the shift control system and the automatic 
transmission to be controlled by the shift control system 
As is illustrated in FIG. 2, a gear transmission (T/M) 3 is connected via a 
torque converter 2 to an output side of an internal combustion engine 
(E/G) 1 which is to be mounted on a vehicle. The transmission 3 has, for 
example, 4-forward/1-reverse speed ranges and can establish desired one of 
the speed ranges by selectively engaging or disengaging (releasing) plural 
engaging elements 3A such as brakes and clutches (not shown). 
These engaging elements 3A are fed with an engaging force in the form of a 
hydraulic pressure. To per form a shifting operation of the speed range by 
changing over the state of engagement of these engaging elements 3A, a 
speed-range shifting mechanism 4 constructed of directional control valves 
equipped with a shifting solenoid is arranged. Further, to adjust the 
engaging force for the engaging elements 3A, engaging force regulating 
means 5 formed of a hydraulic pressure regulator valve is also arranged. 
These speed-range shifting mechanism 4 and engaging force regulating means 
5 are provided integrally as a single valve unit 15. 
An electronic control unit (ECU) 6 is also arranged as a shift control 
system (which may hereinafter be called the "control means") for 
controlling the speed-range shifting mechanism 4 and the engaging force 
regulating means 5. 
Construction of essential parts of the shift control system 
As is illustrated in FIG. 1, ECU 6 is internally provided with a 
functioning part (speed-range setting means) 7 for selecting optimal one 
of plural speed range and setting the optimal speed range, a functioning 
part (change-over command means) 8 for commanding a speed range 
change-over operation to the speed-range shifting mechanism 4, and a 
functioning part (engagement state control means) 9 for controlling 
operation of the engaging force regulating means 5. 
The speed-range setting means 7 is provided with two speed-range setting 
parts, that is, a first speed-range setting part (first speed-range 
setting means) 7A and a second speed-range setting part (second 
speed-range setting means) 7B and also with a speed-range determining part 
7C for selecting and determining one of values set at these speed-range 
setting parts 7A,7B, respectively. 
Of these, the first speed-range setting part 7A sets an optimal speed range 
on the basis of a preset normal shift pattern while using vehicle speed 
information and throttle opening information (engine load information), so 
that normal automatic shift control can be performed. Accordingly, a 
vehicle speed sensor 12 as vehicle speed detecting means and a throttle 
opening sensor 13 as throttle valve operation detecting means are 
connected to the first speed-range setting part 7A. 
The second speed-range setting part 7B, on the other hand, comprises a 
driving state determining part (driving state determination means) 7B-1 
for determining the state of driving of a vehicle by fuzzy inference on 
the basis of information on the state of operation of the vehicle, 
information on driving behavior intended by the driver and information of 
conditions of a road on which the vehicle is running and a speed-range 
setting means 7B-2 for selecting optimal one of plural speed ranges on the 
basis of the results of the determination by the driving state 
determination means 7B-1 and setting the optimal speed range. The 
second-speed-range setting part 7B therefore sets the optimal speed range 
on the basis of the fuzzy inference. In the present embodiment, 
information on the vehicle speed is fed as information on the state of 
operation of the vehicle, information on the throttle opening and 
information on brake manipulation are fed as information on driving 
behavior intended by the driver, and information on the grade and 
meandering degree of the road are fed as information on the conditions of 
the road, whereby the optimal speed range is set at the second speed-range 
setting part 7B. To the second speed range setting part 7B, are therefore 
connected the vehicle speed sensor 12, the throttle opening sensor 13 as 
the engine load detecting means, a brake switch 14 as the brake 
manipulation detecting means, grade detection means 10, and meandering 
degree detection means 11. As the engine load detection means, a sensor 
for detecting the amount of depression of an accelerator pedal can be 
used. As the engine load information, it is possible to use the opening of 
the throttle valve or the rate of the change in the opening of the 
throttle valve or the amount of depression of the accelerator pedal or the 
rate of the change in the amount of depression of the accelerator pedal. 
The speed-range determining part 7C usually selects the optimal speed range 
which has been set based on the normal shift pattern at the first 
speed-range setting part 7A, but when the speed range set by the fuzzy 
inference at the second speed range setting part 7B is lower than the 
speed range set at the first speed-range setting part 7A, selects as the 
optimal speed range the speed range set at the second speed range setting 
part 7B. 
When the optimal speed range selected by the speed-range setting means 7 is 
different form the current speed range, the change-over command means 8 
commands a speed-range shifting operation to the speed-range shifting 
mechanism 4. 
The engagement state control means 9 controls the level of a hydraulic 
pressure which causes the engaging element 3A to engage. In the present 
embodiment, two hydraulic control patterns (in other words, engaging force 
control patterns) are provided as indicated by characteristic lines A and 
B in FIG. 3(b). One of these patterns is chosen for use in the control. 
Incidentally, FIG. 3(a) illustrates the state of speed range, FIG. 3(b) the 
hydraulic control duty, FIG. 3(c) the control hydraulic pressure, FIG. 
3(d) the rotational speed of a turbine, and FIG. 3(e) the torque of drive 
shaft. The hydraulic control duty shows how much the control hydraulic 
pressure is reduced. The control hydraulic pressure becomes smaller as the 
hydraulic control duty becomes greater, and the control hydraulic pressure 
becomes greater as the hydraulic control duty becomes smaller. 
The hydraulic control pattern A places importance on the response of 
shifting. It is designed in such a way that the initial engaging pressure 
is high and the subsequent period during which the engaging pressure 
gradually increases is short to ensure rising of the engaging pressure to 
a line pressure in a short time. The hydraulic control pattern B as the 
second hydraulic pressure feeding pattern, on the other hand, places 
importance on the smoothness of shifting. It is designed in such a way 
that the initial engaging pressure is lower than that of the pattern A, 
the subsequent period during which the engaging pressure gradually 
increases is longer than that of the pattern A, and the timing of an 
increase to the line pressure becomes slower than that of the pattern A. 
The engagement state control means 9 normally sets the hydraulic pressure 
control pattern A which places importance on the response of shifting, but 
upon performance of a downshift on a downhill road (hereinafter called a 
"downhill downshift") which the driver can hardly predict, sets the 
hydraulic pressure control pattern B which places importance on the 
smoothness of shifting. 
For this purpose, the engagement state control means 9 is provided with a 
determination unit 9A for determining if a downhill downshift is about to 
be performed, and also with a hydraulic pressure control pattern setting 
unit (hydraulic pressure control pattern setting means) 9B for setting a 
hydraulic pressure control pattern (engaging force control pattern) on the 
basis of the determination by the determination unit 9A. 
A downhill downshift is a downshift for applying an engine brake on a 
downhill road. Such a downhill downshift is performed when the speed range 
set by the fuzzy inference at the second speed range setting means 7B is 
selected as an optimal speed range. 
Described specifically, the vehicle may be accelerated on a downhill road 
even if the driver does not manipulate the throttle valve, in other words, 
does not depress the accelerator pedal, and the vehicle speed may 
increase, for example, from point A to point D as viewed in FIG. 20. Here, 
an upshift from 3rd speed to 4th speed is commanded by the first speed 
range setting means 7A as the speed increases passing across the upshift 
line a as indicated in the diagram. If the vehicle is running on a 
downhill road, however, it is 2nd stage that is to be selected using the 
fuzzy inference. Therefore a downshift from 3rd speed to 2nd speed is 
conversely commanded to obtain an engine brake. This downshift is allowed 
to take precedence so that the downshift is commanded. 
As is appreciated from the foregoing, a downshift is performed on a 
downhill road even if the driver does not depress the accelerator pedal 
(i.e., does not manipulate the throttle valve). The driver cannot expect 
this downshift operation, and is rather surprised by a shift shock which 
takes place accompanying the downshift operation. 
The determination unit 9A performs determination on the basis of a 
change-over command signal (shift position control signal) outputted 
through the change-over command means 8, shift mode information available 
from the speed range determining means 7C via the change-over command 
means 8, and throttle opening information (accelerator pedal depression 
amount information) from the throttle opening sensor (or accelerator pedal 
depression amount sensor) 13. When the speed range shifting command is a 
downshift to the speed range selected according to the fuzzy inference by 
the second speed range setting means 7B and the throttle valve is not 
being manipulated (the accelerator pedal is not being depressed), it is 
determined whether a downhill downshift should be commanded or not. 
The hydraulic pressure control pattern setting unit 9B usually sets the 
hydraulic pressure control pattern A which places importance on the 
response of shifting, but when the shifting of the speed range is 
determined to be a downhill downshift at the determination unit 9A, sets 
the hydraulic pressure control pattern B which places importance on the 
smoothness of shifting. 
Basic concept of the shift control 
According to the shift control system of this embodiment, it is designed to 
perform control of a downhill downshift as a part of its shift control. 
Besides the downhill downshift control mode, various other shift control 
modes are included. By the speed-range setting means 7, especially by the 
second speed range setting means 7B, speed ranges can be set in various 
modes. 
The basic concept of control of shifting by the present shift control 
system will next be described with reference to FIG. 4. The shift control 
modes are divided, for example, into five modes. Provided ready for use 
are a normal mode (MODE 0) for flat roads such as streets in urban 
regions, an uphill cornering mode (MODE 1) for frequently bent uphill 
slopes in mountainous regions, a downhill weak engine brake mode (MODE 2) 
for gentle downhill slopes where a weak engine brake is needed, a downhill 
strong engine brake mode (MODE 3) for steep downhill slopes and downhill 
slopes of large meandering degrees where a strong engine brake is needed, 
and a straight uphill slope road (MODE 4) for long straight uphill slopes. 
The downhill weak engine brake mode (MODE 2) and the downhill strong 
engine brake mode (MODE 3) correspond to the downhill road downshift mode 
described above. 
A shift pattern for running on flat roads such as streets in urban regions 
is provided ready for use in the normal mode 0. Using this shift pattern 
for flat road running, an optimal speed range is set in accordance with an 
accelerator pedal position (i.e., throttle opening), which corresponds to 
an engine load, and a vehicle speed in the normal mode 0. This is not 
different at all from the conventional shift control. When this mode 0 is 
selected, a speed range is set according to a shift control program which 
is separately provided ready for use. 
A shift pattern, which is different from the shift pattern for flat road 
running, is provided ready for use in the uphill cornering mode 1. Details 
of this shift pattern will be described subsequently herein. This shift 
pattern is set so that even if the accelerator pedal is released partly or 
fully upon entering a corner, an upshift is hardly allowed to take place. 
Shift hunching is therefore prevented. 
In the downhill weak engine brake mode 2 and the downhill strong engine 
brake mode 3 which correspond in combination to the downhill road 
downshift mode, the speed range is forcedly set at 3rd speed range and 2nd 
speed range, respectively, so that an appropriate degree of engine brake 
is automatically applied to prevent the vehicle from entering a corner at 
an excessively high speed on a downhill slope and also to reduce the 
number of braking operations. 
In the straight uphill slope mode 4, the speed range is set at a position 
lower by one stage from the current shift position to make sure to provide 
a necessary drive force. As a downshift operation is automatically 
performed in this straight uphill slope mode 4, a necessary drive force 
can be retained to prevent shift hunching. Shift control in this mode 4 is 
effective especially for small-displacement vehicles. 
According to the shift control system of this embodiment, optimal one of 
these control modes is selected by conducting fuzzy inference on the basis 
of various fuzzy input variables, which indicate the state of operation of 
the vehicle, the driving behavior intended by the driver and the 
conditions of the road, and a membership function (in the form of a Cripps 
set). Based on the optimal control mode so selected, a fuzzy shift 
position is set. This setting method of a fuzzy shift position is 
different from the setting method that a speed range is set by directly 
inferring all shift positions for running in urban regions and mountainous 
regions according to fuzzy inference. The shift control system of this 
invention therefore requires fewer rules for the selection of an optimal 
control mode so that the membership function can be simplified. 
Incidentally, each of the arrows shown in FIG. 4, which are placed between 
the individual control modes, indicates the direction in which the control 
mode can be changed over from the current control mode. Assuming by way of 
example that the current mode is the uphill cornering mode (MODE 1), it is 
possible to return from MODE 1 to the normal mode 0 or to directly change 
over from MODE 1 to the downhill weak engine brake mode 2. MODE 1 however 
cannot be changed directly to the straight uphill road mode 4 or the 
downhill strong engine brake mode 3. To do this, the change must be 
performed by way of MODE 0 or MODE 2, respectively. 
Shift control programs 
As has been described above, the second speed-range setting means 7B 
computes a fuzzy shift position, and based on the results of the 
computation, fuzzy shift control is performed by ECU 6. Procedures of 
shift control by various means in ECU 6 are conducted in accordance with 
such a program as shown, for example, in the flow charts of FIGS. 5 
through 11 and FIGS. 14 through 18. Thus, the control procedures by the 
various means in ECU 6 will hereinafter be described by specifically 
referring to these flow charts. Where the normal mode 0 is selected by the 
fuzzy shift control, the shift control in the normal mode 0 is executed in 
accordance with a shift control program separately provided for the normal 
mode. 
Main routine 
Referring first to FIG. 5, a description will now be made of the main 
routine (general flow) of the fuzzy shift control program. This program is 
composed of an initial processing routine in which control variables and 
various stored values are set at initial values, a routine in which input 
variables from various sensors and the like are inputted and computed, a 
routine in which fuzzy input variables are computed from the input 
variables inputted or computed, a routine in which values of various fuzzy 
input switches are set based on the input variables, a routine in which 
establishment or non-establishment of a fuzzy rule is determined, a 
routine provided corresponding to a control mode, in which subtraction is 
being performed, so that a fuzzy shift position is set based on the fuzzy 
rule so established, a routine in which a shift position is outputted 
based on the fuzzy shift position so set, and a routine in which a shift 
control hydraulic pressure is commanded. 
The initial processing routine, executed at the beginning of execution of 
the main program, for example, is executed only once immediately after an 
ignition key switch (not shown) has been turned on. Upon completion of the 
execution of the initial processing routine, the subsequent routines are 
repeatedly executed at predetermined cycles (for example, 50 msec). 
Input and computation routine for input variables 
In this routine, input variables which are needed for the shift control are 
inputted from the above-described various sensors 10-14, a fuel control 
device, or the like. These input variables may be either those obtained by 
simply subjecting detection signals, which have been inputted from the 
sensors, to filtering and A/D conversion or those determined from such 
input variables by computation. Upper and lower limits may be provided for 
inputted values of such input variables as needed, so that values outside 
the corresponding upper or lower limits are limited to the values of the 
upper or lower limits. Input variables required for the shift control are 
presented in Table 1. 
TABLE 1 
______________________________________ 
Input variable Unit Label 
______________________________________ 
Vehicle speed km/hr V0 
Longitudinal acceleration 
g Gx 
Number of engine revolutions 
rpm Nc 
A/N % A/N 
Steering wheel angle deg .theta.w 
Accelerator pedal position 
% APS 
Speed ratio of torque converter 
% e 
Shift position SPOS 
OD switch OD 
Commanded speed range SHIFT0 
Mode 0 computation SHIFT1 
Lateral acceleration g Gy 
Engine torque kg .multidot. m 
ETRQ 
Brake switch BRK 
______________________________________ 
Among the above input variables, the vehicle speed V0 is computed from a 
wheel speed detected by a wheel speed sensor. The steering wheel angle 
.theta.w is set at its predetermined upper limit (for example, 
360.degree.) when its absolute value exceeds the upper limit or at its 
predetermined lower limit (for example, 10.degree.) when its absolute 
value is smaller than the lower limit. The lateral acceleration Gy is set 
at its upper limit when the vehicle speed V0 exceeds a predetermined value 
(for example, 10 km/hr), at 0 when the lateral acceleration is smaller 
than a predetermined value (for example, 10.degree.), and at a 
predetermined upper limit when the lateral acceleration exceeds the upper 
limit. The lateral acceleration Gy is computed based on the following 
formula (A1): 
EQU Gy=(.theta.wC.rho.)/[Lw.multidot.(A+V0.sup.2)].times.C1 (A1) 
Computation of fuzzy input variables 
Eleven fuzzy input variables FV(0) to FV(10) required for fuzzy inference, 
which are shown in Table 2, will be computed next. These fuzzy input 
variables FV(0) to FV(10) can be classified, as shown in Table 2, into 
information on driving behavior intended by the driver, information on the 
state of operation of the vehicle and information on roads. Although the 
steering wheel angle information classified under the road information 
also falls under the information on driving behavior intended by the 
driver, the degree of meandering of the road is determined from the 
steering wheel angle information so that the steering wheel angle 
information will be handled as road information. Likewise, the lateral 
acceleration information classified under the road information can also be 
classified to the vehicle operation information. The degree of meandering 
of the road can however be determined from the lateral acceleration 
information, so that the lateral acceleration information will be handled 
as road information. 
TABLE 2 
______________________________________ 
Input variable Class* Unit Label 
______________________________________ 
Vehicle speed VOI km/hr FV(0) 
Longitudinal acceleration 
VOI g FV(1) 
Steering wheel operation 
RI d .multidot. deg 
FV(2) 
amount 
Per-brake deceleration 
IDBI km/hr FV(3) 
Throttle opening 
IDBI % FV(4) 
Accelerator pedal depressing 
IDBI %/s FV(5) 
speed 
Weight-grade resistance 
RI kgf FV(6) 
Engine torque margin 
VOI kgm FV(7) 
2-second vehicle speed 
VOI km/hr FV(8) 
difference 
Absolute value of steering 
RI deg FV(9) 
wheel angle 
Absolute value of lateral 
RI g FV(10) 
acceleration 
______________________________________ 
*VOI: Vehicle operation information 
RI: Road information 
IDBI: Intended driving behavior information 
Among the fuzzy input variables shown in Table 2, the steering wheel 
operation amount FV(2) is an actual value of the product of the steering 
wheel angle .theta.w and the lateral acceleration Gy. The computation of 
this actual value is conducted at predetermined intervals (for example, 
every second), so that an average of actual values in a predetermined past 
period (for example, 20 seconds) is employed as a parameter indicating the 
busyness (frequency) of steering operations. For the computation of this 
steering wheel operation amount FV(2), the following formulas (A2),(A3) 
can be employed. 
##EQU1## 
As this steering wheel operation amount FV(2) reflects both the steering 
wheel angle and the lateral acceleration as factors, the steering wheel 
operation amount FV(2) takes a greater value at a higher vehicle speed 
when the vehicle turns the same corner and at the same vehicle speed, 
takes a greater value as the corner radius R becomes smaller. Where the 
steering wheel angle is the same, the lateral acceleration becomes greater 
with vehicle speed, resulting in a greater steering wheel operation amount 
FV(2). As is appreciated from the above, the steering wheel operation 
amount FV(2) can be regarded as an index including the frequency of 
steering operations and the driver's tension. 
With respect to the steering wheel operation amount FV(2) obtained from 20 
samples per second, values obtained upon running on a standard street, 
running at a medium speed on a meandering road and running on a meandering 
zigzag road will now be compared. These values are 3.0 (g.deg) or smaller 
upon running on the street, 10-30 (g.deg) upon running at the medium speed 
on a meandering road, and 40 (g.deg) or greater upon running on the 
meandering zigzag road. Marked differences are therefore observed in the 
steering wheel operation amount FV(2) when running on these roads, so that 
runnings on these roads can be distinguished. 
Even if a rule indicating an uphill road or a downhill road is established, 
for example, by running over a bump or as a result of input of other fuzzy 
input variables despite running on a street in an urban region, the 
running can still be determined accurately as running on an urban street 
insofar as the steering wheel operation amount FV(2) is equal to or 
smaller than the above-described value, i.e., 3.0 (g.deg). 
The per-brake deceleration FV(3), the fourth fuzzy input variable in Table 
2, indicates how many km/hr the vehicle speed V0 has been reduced by a 
single braking operation. In this embodiment, the per-brake deceleration 
FV(3) can be computed by the following formula (A4), from a vehicle speed 
VST stored immediately before the braking operation and a fuzzy input 
variable FV(0) of a vehicle speed computed this time: 
EQU FV(3)=VST-FV(0) (A4) 
The accelerator pedal depressing speed FV(5) is determined by converting a 
difference in the throttle opening FV(4), which is detected at 
predetermined intervals (for example, every 0.25 second), into a 
difference per second. 
Further, the value RK of the weight-grade resistance FV(6) is determined by 
subtracting aerodynamic resistance, rolling resistance and acceleration 
resistance from an engine drive force. This can be expressed by the 
following formula (A5): 
______________________________________ 
RK = engine drive force - 
aerodynamic resistance - 
rolling resistance - 
acceleration resistance 
. . . (A5) 
______________________________________ 
The engine drive force (hereinafter referred to as "TE") in the above 
formula (A5) can be computed by the following formula (A6): 
EQU TE=T.sub.E (.eta..sub.E).multidot.t(e).multidot..eta..multidot.i.sub.T 
.multidot.i.sub.F /r (A6) 
where 
T.sub.E (.eta..sub.E): engine torque (kg.m) after subtraction of an exhaust 
loss, 
t(e): torque ratio of the torque converter 2, 
.eta.: transmission efficiency of the gear transmission 3, 
i.sub.F : gear ratio of a differential, and 
r: dynamic load radius of a tire. 
The engine torque T.sub.E (.eta..sub.E) is calculated from an air/fuel 
ratio (A/N) of the engine 1 and the number (Ne) of engine revolutions, 
t(e) is read from a torque ratio table stored beforehand as a function of 
speed ratios (e) of the torque converter, and as .eta., i.sub.T, i.sub.F 
and r, predetermined values set as constants are used. 
The aerodynamic resistance in the above formula (A5) can be computed by the 
following formula (A7): 
##EQU2## 
where 
.rho.a: the density of air, which is given by a constant determined by the 
surrounding air temperature, 
S: the projected area of a front face of the vehicle, 
Cd: drag coefficient, which is given by a constant. 
C2 computed from these constants is also a constant. The aerodynamic 
resistance is therefore computed as a function of the vehicle speed (V). 
The rolling resistance in the above formula (A5) can be computed by the 
following formula (A8): 
EQU Rolling resistance=R0+(CF.sup.2 /CP) (A8) 
where 
R0: rolling resistance upon free rolling, 
CF: cornering force, and 
CP: cornering power. 
R0 can be computed by the following formula (A9): 
EQU R0=.mu.r.multidot.W (A9) 
where 
.mu.r: rolling resistance, and 
W: vehicle weight. 
The second member in the right-hand side of the above formula (A8) is a 
contributing member by cornering resistance where the side skid angle is 
small. Studying the cornering resistance by a two-wheel model under the 
assumption that the ratio of a load borne by a front wheel to that borne 
by a rear wheel is constant (for example, 0.6:0.4 in terms of the 
front-to-rear ratio) and the cornering powers of the front and rear wheels 
are CPf and CPr (constant values), the cornering resistance can be 
computed by the following formula (A10): 
##EQU3## 
where 
C3: constant, and 
GY: lateral acceleration. 
This lateral acceleration GY can be computed based on the steering wheel 
angle .theta..sub.H detected by a steering angle sensor (not shown) and 
the vehicle speed V detected by a vehicle speed sensor (detection means) 
12. 
By incorporating such cornering resistance in the computation of the 
rolling resistance, the weight-grade resistance upon significantly turning 
the steering wheel can be calculated accurately. If the cornering 
resistance were not incorporated, the grade of a meandering downhill road 
would be calculated smaller than its actual grade during cornering and a 
flat road would be estimated as an uphill slope. The incorporation of 
cornering resistance can avoid such potential problems. 
The acceleration resistance in the above formula (A5) can be computed by 
the following formula (A11): 
EQU Acceleration resistance=(W+.DELTA.W).multidot.GX (A11) 
where 
W: the vehicle weight described above, 
.DELTA.W: rotating part equivalent weight, and 
GX: lateral acceleration. 
The lateral acceleration GX can be computed based on the vehicle speed V 
detected by the vehicle speed sensor. The rotating part equivalent weight 
.DELTA.W, on the other hand, can be computed by the following formula 
(A12): 
EQU .DELTA.W=WO+{Ec+Fc(ir.multidot.i.sub.F).sup.2 } (A12) 
where 
W0: complete vehicle curb weight, 
Ec: tire rotating part equivalent weight percentage, 
Fc: engine rotating part equivalent weight percentage, 
ir: the gear ratio of the gear transmission 3, and 
i.sub.F : the gear ratio of the differential. 
At the grade detection means 10, the weight-grade resistance RK is 
calculated by the formula (A5) on the basis of the values calculated by 
the formulas (A6) to (A12) as described above. 
Computation of values of the fuzzy input switches 
Upon determination of fuzzy rules, the fuzzy input switches SW(0) to SW(8) 
compute the applicability of these fuzzy rules like the membership 
function of the fuzzy input variables. The values of the fuzzy input 
switches SW(0) to SW(8) are however expressed by digital values so that 
they are separated as switch inputs from the fuzzy input variables. Table 
3 illustrates these fuzzy input switches: 
TABLE 3 
______________________________________ 
Fuzzy input switch Label 
______________________________________ 
Control mode SW(0) 
Grade resistance, large state 
SW(1) 
Grade resistance, non-negative state 
SW(2) 
Grade resistance, non-negative, 
SW(3) 
large state 
Meandering flag SW(4) 
Throttle opening, large state 
SW(5) 
Throttle opening, medium state 
SW(6) 
2nd-speed engine brake time 
SW(7) 
high acceleration flag 
3rd-speed engine brake time 
SW(8) 
high acceleration flag 
______________________________________ 
The fuzzy input switch SW(0) indicates the selected control mode and its 
value is set by the below-described processing in that mode. 
When the weight-grade resistance continuously remains not smaller than a 
predetermined value CFV 61 for a predetermined time (for example, 2.5 
seconds) within a predetermined period (for example, 5 seconds), the 
vehicle is determined to be running on an uphill slope. Value 1 is 
therefore set at the fuzzy input switch SW(1) to store that the grade 
resistance is in a large stage. 
When the weight-grade resistance continuously remains greater than a 
predetermined negative value (-CFV 62) for a predetermined time (for 
example, 2.5 seconds), the vehicle is determined to have returned from 
running on a downhill slope to running on a flat road. Value 1 is 
therefore set at the fuzzy input switch SW(2) to store that the grade 
resistance is non-negative. 
When the weight-grade resistance continuously remains not greater than a 
predetermined value (CFV 63) for a predetermined time (for example, 5 
seconds), the vehicle is determined to have gone through with running on 
an uphill slope. Value 1 is therefore set at the fuzzy input switch SW(3) 
to store that the grade resistance is non-negative and large. 
When the steering wheel operation amount FV(2) continuously remains not 
smaller than a predetermined value (CFV 21) for a predetermined time (for 
example, 5 seconds), the vehicle is determined to be running on a 
meandering road. Value 1 is therefore set at the fuzzy input switch SW(4) 
to store this running state. Incidentally, determination of leaving of the 
vehicle from the meandering road is effected by using a predetermined 
value (CFV 22) smaller than the above-described predetermined value (CFV 
21) and determining that the steering wheel operation amount FV(2) has 
become smaller. 
When the throttle opening FV(4) continuously remains greater than a 
predetermined value CFV 41 (for example, 25%) for a predetermined time 
(for example, 0.6 seconds), the throttle opening is determined to be 
large. The fuzzy input switch SW(5) is therefore set at value 1 to store 
that the throttle opening is large. 
When the throttle opening FV(4) continuously remains greater than a 
predetermined value CFV 42 (for example 25%), which has been set at a 
value smaller than the above-described predetermined value CFV (25%), for 
a predetermined time (for example, 0.6 seconds), the throttle opening is 
determined to be intermediate. The fuzzy input switch SW(6) is therefore 
set at value 1 to store that the throttle opening is intermediate. 
The fuzzy input switch SW(7) is used to set a 3rd-speed engine brake time 
high acceleration flag. When the throttle opening FV(4) is equal to or 
greater than a predetermined opening CFV 43 (for example, 40%) immediately 
after the fuzzy input switch SW(5) has been set at 1, the fuzzy input 
switch SW(7) is set at 1 to store that the driver intends to make a high 
acceleration on a downhill slope. 
The fuzzy input switch SW(8) sets a 2nd-speed engine brake time high 
acceleration flag. When the throttle opening FV(4) is equal to or greater 
than the predetermined opening CFV 43 (for example, 40%) immediately after 
the fuzzy input switch SW(6) has been set at 1, the fuzzy input switch 
SW(8) is set at 1 to store that the driver intends to make a high 
acceleration on a downhill slope. 
Determination of rule establishment 
According to the shift control by the shift control system according to 
this invention for a vehicle automatic transmission, the establishment of 
one of fuzzy rules to be described below is determined and a control mode 
corresponding to the rule so established is selected. The establishment of 
each fuzzy rule requires that all the following conditions are met. 
(1) Values of fuzzy input switches relevant to the rule are all equal to 
the corresponding values for establishment. 
(2) Fuzzy input variables relevant to the rule all fall within the range of 
a designated membership function. 
(3) The rule is continuously found applicable at least a predetermined 
number of times. 
Table 4 to Table 6 will be presented below. Of these, Table 4 shows fuzzy 
input switches relevant to individual fuzzy rules and their values for 
establishment. Table 5 presents fuzzy input variables relevant to the 
individual fuzzy rules and an outline of the individual fuzzy rules. Each 
membership function is designed as a Cripps set in this embodiment, and 
fuzzy inference is performed depending upon whether each fuzzy input 
variable is within a predetermined range of the corresponding membership 
function. Control modes to be selected upon confirmation of the 
establishment of the individual fuzzy rules are shown in Table 6. 
TABLE 4 
______________________________________ 
Rule Fuzzy switch input 
______________________________________ 
0 SW(1) = 1 
1 SW(1) = 1 
2 -- 
3 -- 
4 -- 
5 -- 
6 SW(0) = 2 
7 SW(0) = 2 
8 SW(0) = 2 and SW(4) = 1 
9 SW(0) = 2 and SW(2) = 1 
______________________________________ 
TABLE 5 
______________________________________ 
Rule Fuzzy input variable 
______________________________________ 
0 [FV(0) small] [FV(4) &gt; 10] [FV(5) &gt; 5] [FV(8) small] 
[FV(9) large] 
1 [FV(0) small] [FV(4) &gt; 10] [FV(5) &gt; 5] [FV(8) small] 
[FV(10) large] 
2 [FV(0) medium] [FV(2) large] [FV(5) small] 
[FV(6) negative] [FV(8) large] 
3 [FV(0) medium] [FV(2) large] [FV(3) large] 
[FV(6) small] [FV(8) negative] 
4 [FV(0) medium] [FV(4) small] 
[FV(6) negative & large] [FV(8) large] 
5 [FV(0) medium] [FV(1)small] [FV(4) large] 
[FV(5) large] [FV(7) small] 
6 [FV(4) small] [FV(6) negative & very large] 
[FV(8) large] 
7 [FV(3) large] [FV(4) small] 
[FV(6) negative & very large] 
8 [FV(4) small] [FV(6) negative] [FV(10) large] 
9 [FV(4) &gt; 3] [FV(6) small] [FV(9) small] 
______________________________________ 
TABLE 6 
______________________________________ 
Mode to be entered after 
Rule establishment of rule 
______________________________________ 
0 Mode 1 
1 Mode 1 
2 Mode 2 
3 Mode 2 
4 Mode 2 
5 Mode 4 
6 Mode 3 
7 Mode 3 
8 Mode 3 
9 Mode 0 
______________________________________ 
Table 6 shows the procedures for the determination of establishment of the 
fuzzy rule described above. With respect to each of rules, it is first 
determined in the rule applicability determining routine whether the rule 
is applicable or not. It is then confirmed in the checking routine for the 
applicable rule if the routine found applicable in the rule applicability 
determining routine is applicable at least a predetermined number of times 
continuously. 
FIG. 7 illustrates more specific procedures of the rule applicability 
determination. When this routine is executed, the speed-range setting 
means 7 of ECU 6 first resets the program control variable n to value 0 in 
step S120. It is next determined whether the fuzzy input switches for the 
rule n are matching (step S121). In the case of the rule 0, for example, 
it is determined based on Table 4 whether the fuzzy input switch SW(1) is 
equal to value 1 for establishment or not. In the case of the rule 8, for 
example, it is determined whether or not the fuzzy input switch SW(0) and 
the fuzzy input switches SW(4) are equal to values 2 and 1 for 
establishment, respectively. It is hence determined whether or not each of 
these rules is established. 
If none of fuzzy input switches relevant to the rule n is determined to be 
matching in step S121, the routine advances to step S123 and value 0 is 
set as the control variable TEKI(n). If all the fuzzy input switches 
relevant to the rule n are determined to be matching in step S121, on the 
other hand, the routine advances to step S122. Here, it is determined 
whether or not all the fuzzy input variables relevant to the rule n are 
matching, in other words, fall within prescribed ranges of the membership 
functions designated by the fuzzy input variables. 
As is illustrated in Table 5, for example, the applicability of the five 
fuzzy input variables is determined under the rule 0 whereas the 
applicability of four fuzzy input variables is determined under the rule 
4. The proposition about whether the fuzzy input variable FV(0) is small, 
namely, the vehicle speed is low or not is inferred by determining, based 
on a 0th membership function provided corresponding to the fuzzy input 
variable, whether or not the fuzzy input variable FV(0) is a value within 
a range defined by predetermined upper and lower limits (for example, 
within a range of from 10 km/hr to 55 km/hr). Similarly, the proposition 
about whether the fuzzy input variable FV(0) is medium, namely, the 
vehicle speed is medium or not is inferred by determining, based on a 1st 
membership function provided corresponding to this fuzzy input variable, 
whether or not the fuzzy input variable FV(0) is a value within a range 
defined by predetermined upper and lower limits (for example, within a 
range of from 30 km/hr to 100 km/hr). The relationships between these 
propositions and membership functions are summarized in Table 7. 
TABLE 7 
__________________________________________________________________________ 
Membership 
Range of fuzzy 
Proposition function 
input variable Remarks 
__________________________________________________________________________ 
Is the vehicle speed low? 
0th P01L .ltoreq. FV(0) .ltoreq. P01U 
P01L &lt; P02L &lt; 
Is the vehicle speed high? 
1st P02L .ltoreq. FV(0) .ltoreq. P02U 
P01U &lt; P02U 
Is the longitudinal acceleration large? 
0th P1L .ltoreq. FV(1) .ltoreq. P1U 
Is the steering wheel operation amount 
0th P2L .ltoreq. FV(2) .ltoreq. P2U 
large? 
Is the brake deceleration degree large? 
0th P3L .ltoreq. FV(3) .ltoreq. P3U 
Is the throttle opening small? 
0th P41L .ltoreq. FV(4) .ltoreq. P41U 
P41L &lt; P42L &lt; 
Is the throttle opening 3% or greater? 
1th P42L .ltoreq. FV(4) .ltoreq. P42U 
P43L &lt; P44L; 
Is the throttle opening 10% or greater? 
2nd P43L .ltoreq. FV(4) .ltoreq. P43U 
P41U = P42L; 
Is the throttle opening large? 
3rd P44L .ltoreq. FV(4) .ltoreq. P44U 
P42U = P43U = 
P44U 
Is the accelerator pedal depressing 
0th P51L .ltoreq. FV(5) .ltoreq. P51U 
P51L &lt; P52L &lt; 
speed low? P53L &lt; P51L &lt; 
Is the accelerator pedal depressing 
1st P52L .ltoreq. FV(5) .ltoreq. P52U 
P52U = P53L 
speed faster than 5%/s? 
Is the accelerator pedal depressing 
2nd P53L .ltoreq. FV(5) .ltoreq. P53U 
speed high? 
Is the grade resistance negative and 
0th -MIN .ltoreq. FV(6) .ltoreq. -P61U 
-P61U 
very large? &lt; -P62U 
Is the grade resistance negative and 
1st -MIN .ltoreq. FV(6) .ltoreq. -P62U 
&lt; -P63U 
large? 
Is the grade resistance negative? 
2nd -MIN .ltoreq. FV(6) .ltoreq. -P63U 
Is the engine torque margin small? 
0th P7L .ltoreq. FV(7) .ltoreq. P7U 
Is the 2-second vehicle speed 
0th P81L .ltoreq. FV(8) .ltoreq. P81U 
P81L &lt; P82L = 
difference small? P82U &lt; P82U 
Is the 2-second vehicle speed 
1st P82L .ltoreq. FV(8) .ltoreq. P82U 
difference large? 
Is the absolute value of the steering 
0th P91L .ltoreq. FV(9) .ltoreq. P91U 
P91L &lt; P92L = 
wheel angle small? P92U &lt; P92U 
Is the absolute value of the steering 
1st P92L .ltoreq. FV(9) .ltoreq. P92U 
wheel angle large? 
Is the absolute value of the lateral 
0th P10L .ltoreq. FV(10) .ltoreq. P10U 
P10L &lt; P10U &lt; 
acceleration small? P11L &lt; P11U 
Is the absolute value of the lateral 
1st P11L .ltoreq. FV(10) .ltoreq. P11U 
acceleration large? 
__________________________________________________________________________ 
FIG. 8 is a routine for checking whether or not the rule determined to be 
applicable is determined to be matching at least a predetermined number of 
times continuously. ECU 6 first resets the program control variable n to 
value 0 in step S130. In step S131, it is next determined whether the 
control variable TEKI(n) corresponding to the rule n designated in Step 
S130 is value 0 or not. If the control variable TEKI(n) is determined to 
be value 0 in step S131, the rule n is not applicable and the routine then 
advances to step S132, where the counter CNT(n) for rule n is reset to 
value 0 and value 0 is set as the control variable SRT(n) to store 
non-establishment of the rule n. The routine then advances to step S136 
which will be described subsequently herein. 
If the results of the determination in step S131 is negative and the 
control variable TEKI(n) corresponding to the rule (n) is not value 0, the 
routine advances to step S133, where after the counter value CNT(n) is 
incremented by value 1, it is determined whether or not the counter value 
CNT(n) has reached a predetermined value XCMAX(n) set corresponding to the 
rule n (step S134). If the counter value CNT(n) has not reached the 
predetermined value XCMAX(n), the routine advances to step S136 without 
making any change to the variable value SRT(n). The predetermined value 
XCMAX(n) can be set at a suitable value in view of influence of the 
tension of execution of the control mode, noise, etc. to the determination 
of establishment of each rule. 
When the checking routine for one applicable rule has been completed, the 
program control variable n is incremented by value 1 in step S136, 
followed by the determination of whether the variable n is equal to a 
predetermined value CRUL (the value corresponding to the number of the 
rule) or not (step S138). Until the variable value n becomes equal to the 
predetermined value CRUL, the above-described step S131 onwards are 
executed repeatedly to perform the checking routine for applicable rule 
with respect to all the rules. When the checking routine for applicable 
rule has been completed with respect to all the rules and the 
determination in step S138 has given positive results, the routine is 
ended. 
When the above routine is repeated and the control variable TEKI(n) 
corresponding to the specific rule n is continuously set at value 1, the 
counter value CNT(n) is incremented whenever the routine is executed and 
eventually reaches the predetermined value XCMAX(n). When the 
determination in step S134 gives positive results, step S135 is executed 
so that the counter CNT(n) is reset at value 0 and value 1 is set as the 
control variable SRT(n) to store the establishment of the rule n. 
Processing routine in each mode 
When the established rule has been determined as described above, ECU 6 
next perform processing in each mode by the procedures shown in FIG. 9. 
Specifically, the value of the fuzzy input switch SW(0) is first set as 
the program variable X in step S140. In other words, the current control 
mode is specified. A processing routine corresponding to the current 
control mode X is executed (step S142). 
According to this shift control, five control modes are provided including 
mode 0 to mode 4. The program variable X, namely, the fuzzy input switch 
SW(0) is set at one of 0-4. The current control mode X in step S142 is 
therefore one of mode 0 to mode 4 and a processing routine is set for each 
control mode. Specifically, there are provided a processing routine for 
the current mode 0, a processing routine for the current mode 1, a 
processing routine for the current mode 2, a processing routine for the 
current mode 3, and a processing routine for the current mode 4. 
Processing in each of the current modes will hereinafter be described 
specifically. 
Processing routine in the current mode 0 
When the current shift control is performed in the control mode 0 (normal 
mode 0), a fuzzy shift position variable SHIFF is set in accordance with 
the flow chart of FIG. 10. Incidentally, the control mode 0 sets a speed 
range by using a shift pattern for ordinary flat road running as described 
above. As is illustrated in FIG. 4, it is possible to change from this 
control mode 0 to the mode 1, the mode 2 and the mode 4. 
According to this processing routine, it is determined in step S150 whether 
or not any of the control variables SRT(2), SRT(3) and SRT(4) is value 1 
to indicate the storage of establishment of the corresponding rule. These 
variables SRT(2), SRT(3) and SRT(4) are to store the establishment of the 
corresponding rules 2, 3 and 4. Establishment of any of these rules as 
shown in Table 6 indicates that the routine should advance to the mode 2. 
Where the results of the determination in step S150 are "YES", the routine 
therefore advances to step S151 so that the fuzzy input switch SW(0) is 
set at value 2 and the fuzzy shift position variable SHIFF is set at value 
3. The routine is then ended. The mode 2 is, as described above, a mode to 
make the vehicle run down at the 3rd speed range on a downhill slope while 
applying an engine brake. 
Where none of the control variables SRT(2), SRT(3) and SRT(4) is value 1 
and the determination in step S150 has resulted in "NO", step S152 is 
performed to determine whether any of the control variables SRT(0) and 
SRT(1) is value 1 or not. These variables are to store the establishment 
of the rules 0 and 1, respectively. As is illustrated in Table 6, 
establishment of any of these rules indicates that the routine should 
advance to the mode 1. Where the determination in step S152 has resulted 
in "YES", the routine advances to step S154 and the fuzzy input switch 
SW(0) is set at value 1. 
The routine then advances to step S155, where it is then determined whether 
the variable SHIF1, which indicates a shift position (a speed range 
computed in the mode 0) determined based on the shift pattern provided for 
use in the mode 0, is value 4 indicating the 4th speed range. Where this 
determination has resulted in "YES", value 3 is set as the fuzzy shift 
position variable SHIFF to forcedly downshift to the 3rd speed range, 
whereby this routine is ended. 
Where the determination is step S155 has resulted in "NO", on the other 
hand, the routine advances to step S156 to set a variable value SHIF1 as 
the fuzzy shift position variable SHIFF, whereby this routine is ended. 
Incidentally, the mode 1 is the uphill cornering mode as shown in FIG. 4, 
in which a speed range is determined using a shift pattern extending in to 
regions in which the vehicle is driven at the 2nd and 3rd speed ranges as 
will be described subsequently herein. 
Upon changing from the mode 0 to the mode 1, a forced downshift to the 3rd 
speed range is commanded when the vehicle is being driven at the 4th speed 
range. In the course of this downshift operation, the shift pattern is 
switched over from the shift pattern for the normal mode 0 to the shift 
pattern for the uphill cornering mode 1. When the vehicle is being driven 
at a speed range other than the 4th speed range, the shift pattern is 
changed over while maintaining the speed range. 
Where any of the control variables SRT(2), SRT(3) and SRT(4) is not value 1 
and the determination in step S152 has resulted in "NO", the routine 
advances to step S160 to determine whether the control variable SRT(5) is 
1 or not. This variable is to store the establishment of the rule 5 and as 
is shown in Table 6, the establishment of the rule 5 indicates that the 
mode 4 should be entered. When the determination in step S160 has resulted 
in "YES", the routine therefore advances to step S162, where it is then 
determined whether or not the shift position variable SHIF1 determined by 
the shift pattern provided for use in the mode 0 is value 4 indicating the 
4th speed range. Where the determination has resulted in "YES", the 
routine advances to step S164, where the fuzzy input switch SW(0) is set 
at value 4 and to perform a forced downshift to the 3rd speed range lower 
by one stage than the current speed range, value 3 is set as the fuzzy 
shift position variable SHIFF. The routine is hence ended. 
When the determination in step S162 has resulted in "NO", on the other 
hand, the routine advances to step S165, where it is then determined 
whether or not the shift position variable SHIF1 is value 3 indicating the 
3rd speed range. When the results of the determination are "YES", the 
routine advances to step S166, where the fuzzy input switch SW(O) is set 
at value 4 and to perform a forced downshift to the 2nd speed range lower 
by one stage than the current speed range, value 2 is set at the fuzzy 
shift position variable SHIFF. The routine is hence ended. 
In the mode 4, that is, the straight uphill slope mode, the speed range is 
forcedly downshifted to the 3rd speed range or 2nd speed range when the 
speed range set by the shift pattern provided for use in the normal mode 0 
is the 4th speed range or the 3rd speed range. respectively. 
Where the shift position variable SHIF1 is neither value 4 indicating the 
4th speed range nor value 3 indicating the 3rd speed range, the routine 
advances to step S168, where the fuzzy input switch SW(0) is retained at 
value 0 and the fuzzy shift position variable SHIFF is set at value 5. The 
routine is thus ended. Setting of the fuzzy shift position variable SHIFF 
at value 5 means to set the speed range at the 5th speed range. No 5th 
speed range however exists in this transmission as a matter of fact, so 
that the shift command by the fuzzy shift position variable SHIFF is 
ignored and the shift control in the normal mode 0 is continued. 
When the control variable SRT(5) is not 1 and the results of the 
determination in step S160 are "NO", the routine advances to step S168 
described above. Accordingly, the fuzzy input switch SW(0) is retained at 
value 0 and the fuzzy shift position variable SHIFF is set at value 5, so 
that the shift control in the normal mode 0 is continued. The routine is 
hence ended. 
Processing routine in the current mode 1 
When the current shift control is performed in the control mode 1, the 
fuzzy shift position variable SHIFF is set in accordance with the flow 
chart of FIG. 11. Incidentally, the control mode 1 sets a speed range by 
using the shift pattern for the uphill cornering mode as described above. 
From this control mode 1, it is possible to move to the mode 0 or the mode 
2 as shown in FIG. 4. 
According to this processing routine, it is first determined in step S170 
whether or not the vehicle speed FV(0) is smaller than a predetermined 
value CFV0 (for example, 10 km/hr). If the results of this determination 
are "YES", the routine advances to step S171, where the fuzzy input switch 
SW(0) is set at value 0 and value 5 is set at the fuzzy shift position 
variable SHIFF to move to the normal mode 0. When the vehicle speed is 
low, the normal mode 0 may be executed unconditionally. 
Where the vehicle speed FV(0) is higher than a the predetermined value CFV0 
(for example, 10 km/hr) and the results of the determination in step S170 
are "NO", the routine advances to step S172 and by using the shift pattern 
for the uphill cornering mode 1, the current shift position N is computed 
from the detected vehicle speed V0 and throttle opening APS. FIG. 12 
illustrates shift patterns for upshifts from the 2nd speed range to the 
3rd speed range and also from the 3rd speed range to the 4th speed range. 
When the control mode changes from the normal mode 0 to the uphill 
cornering mode 1, each upshift line is changed as indicated by an arrow in 
the diagram so that the driving region at the 2nd speed range or the 3rd 
speed range is expanded. 
Described specifically, the upshift line (indicated by a solid line) from 
the 2nd speed range to the 3rd speed range in the normal mode 0 divides 
two shift regions from each other as a constant vehicle speed line 
V.sub.230. With respect to the upshift line (indicated by a broken line) 
for the uphill cornering mode 1, this constant vehicle speed line moves to 
a line for a constant vehicle speed V.sub.231 higher than the vehicle 
speed V.sub.230 so that the 2nd speed range region is expanded. Similarly, 
the upshift line (indicated by a solid line) from the 3rd speed range to 
the 4th speed range in the normal mode 0 divides two shift regions from 
each other as a constant vehicle speed line V.sub.340. With respect to the 
upshift line (indicated by a broken line) for the uphill cornering mode 1, 
this constant vehicle speed line moves to a line for a constant vehicle 
speed V.sub.341 higher than the vehicle speed V.sub.340 so that the 3rd 
speed range region is expanded. 
The computation of the shift position N in step S172 is conducted using the 
shift pattern which is indicated by the upshift line in the form of the 
broken line in FIG. 13. Further, the expansion of the 2nd speed range or 
3rd speed range region as a result of the move from the normal mode 0 to 
the uphill cornering mode 1 is shown by a hatched area A in FIG. 13. 
After step S172, the routine next advances to step S173. By computing the 
shift position from the detected vehicle speed V0 and throttle opening APS 
while using the normal shift pattern for the normal mode 0, it is then 
determined whether or not an upshift from the 2nd speed range to the 3rd 
speed range or from the 3rd speed range to the 4th speed range takes 
place. Where such an upshift is determined to take place, value 1 is set 
as the shift number FLGYN. 
According to the shift control in the mode 1, the fuzzy input switch SW(0) 
is set at value 1 and using the fuzzy shift position variable SHIFF, a 
forced shift to the 3rd speed range or a speed range lower than the 3rd 
speed range is commanded, as described above. 
Setting of value 1 as the shift number FLGYN indicates the existence of a 
change in the shift position which would perform an upshift if no command 
were made by the variable SHIFF. This will be explained with reference to 
FIG. 13. This diagram indicates that by the change in the shift position, 
the new shift position has entered the area (the hatched area A) which is 
surrounded by the upshift line (solid line) for the normal mode 0 and the 
upshift line (broken line) for the mode 1. This entrance of the shift 
position into the area A may take place when in FIG. 13, the driver has 
removed his foot from the accelerator pedal and the throttle opening APS 
has become smaller as indicated by an arrow TR1 or the vehicle speed V has 
increased as indicated by an arrow TR2. 
It is to perform the change from the control mode 1 to another control mode 
by selecting as the timing for the change the time of crossing of the 
upshift line that as described above, the shift position N is computed in 
step S172 or the occurrence or non-occurrence of an upshift is stored in 
terms of the shift number FLGYN in step S173. By changing the control mode 
at such timing, it is prevented to give a sense of incongruity to the 
driver. 
Subsequent to step S173, the routine then advances to step S174. It is then 
determined whether the fuzzy input switch SW(3) is value 1 or not, the 
steering wheel angle FV(9) is smaller than a predetermined value CFV9 (for 
example, 50.degree.) or not and the lateral acceleration FV(10) is smaller 
than a predetermined value CFV10 or not. In other words, it is determined 
whether the upward grade has ended or not and the road is free of 
meandering or not. When this determination has resulted in "NO", the 
routine advances to step S180. If the results of the determination in step 
S174 are "YES", on the other hand, the routine advances to step S175, 
where it is then determined whether or not the shift position N determined 
based on the shift pattern for the uphill cornering mode is greater than 
the fuzzy shift position variable value SHIFF or whether or not the flag 
FLGYN indicating the occurrence of an upshift is value 1. If each of these 
determinations results in "NO", the routine advances to step S180. If one 
of these determinations results in "YES", the routine advances to step 
S176. 
In step S176, it is determined whether or not any of the control variables 
SRT(2), SRT(3) and SRT(4) for storing the establishment of the 
corresponding rules is value 1. These variables are to store the 
establishment of the rules 2, 3 and 4, respectively, as described above. 
As shown in Table 6, the establishment of any one of these rules indicates 
that the mode 2 should be entered. When the results of the determination 
in step S176 are "YES", the routine advances to step S177, where value 2 
is set to the fuzzy input switch SW(0) and value 3 is set as the fuzzy 
shift position variable SHIFF. The routine is hence ended. The mode 2 is, 
as described above, a mode for making the vehicle to run down at the 3rd 
speed range on a downhill slope. 
Where each of the control variables SRT(2), SRT(3) and SRT(4) is not value 
1 and the results of the determination in step S176 are "NO", the routine 
advances to step S178, where the fuzzy input switch SW(0) is set at value 
0 and the fuzzy shift position variable SHIFF is set at value 5. This 
routine is hence ended. In this case, the control mode is changed from the 
uphill cornering mode 1 to the normal mode 0. 
Upon advance to step S180, on the other hand, it is then determined whether 
or not the shift position N computed in step S172 is 3 or higher. When the 
results of the determination in step S180 are "NO", the routine advances 
to step S184 which will be described subsequently herein. When the 
determination in step S180 has resulted in "YES", the routine advances to 
step S181 which will also be described subsequently herein. 
In step S181, it is determined whether or not any of the above-described 
control variables SRT(2), SRT(3) and SRT(4) is value 1. When the results 
of the determination in step S181 are "YES", the routine advances to step 
S182 so that the fuzzy input switch SW(0) is set at value 2 and the fuzzy 
shift position variable SHIFF is set at value 3. This routine is hence 
ended. As a result, the mode 2 is executed. 
When the results of the determination in either step S180 or step S181 are 
"NO", it is meant that the uphill cornering mode 1 be continued. In this 
case, however, it is determined in step S184 and step S185 whether or not 
the above-described shift position N is equal to 4 and whether or not one 
of the variables SRT(0) and SRT(1) is value 1. The variables SRT(0) and 
SRT(1) are to store the establishment of the rules 0 and 1, respectively, 
as described above. Establishment of one of these rules indicates that the 
mode 1 should be executed. 
When the shift position computed by the shift pattern for the uphill 
cornering mode 1 is not the 4th speed range or neither the variable SRT(0) 
nor the SRT(1) is value 1, in other word, when the results of the 
determination in either step S184 or step S185 are "NO", the routine 
advances to step S186 and the fuzzy shift position variable SHIFF is then 
set at value N. This routine is hence ended. 
When the shift position N is 4 and either the variable SRT(0) or the SRT(1) 
is value 1, the shift control in the uphill cornering mode is performed 
again in the same mode 1, whereby value 3 is set as the fuzzy shift 
position variable SHIFF to achieve a downshift from the 4th speed range to 
the 3rd speed range. 
When the shift control in the uphill cornering mode is executed, the 
upshift line is moved so that upon entering a corner of an uphill road, an 
upshift operation is hardly performed even if the depression of the 
accelerator pedal is released partly or fully and the throttle opening is 
reduced. This will be described with reference to FIG. 13. When the shift 
control is changed from the mode 0 to the mode 1, the shift area indicated 
by hatching A is enlarged. On a frequently meandering uphill road, an 
operation line indicated by the throttle opening, which corresponds to the 
depression of the accelerator pedal operated by the driver, and the 
vehicle speed draws a circle, which often appears in the area of the 
hatching A shown in FIG. 13. As a result, even if a meandering uphill road 
continues, the number of upshifts to be performed is reduced so that the 
problem of shift hunching is reduced. 
Processing routine in the current mode 2 
When the current shift control is being performed in the control mode 2, 
the speed range is controlled in accordance with the flow chart of FIG. 
14. The control mode 2 is, as has been described above, the downhill weak 
engine brake mode in which the vehicle runs down on a downhill slope while 
maintaining the 3rd speed range. Depending on the degree of depression of 
the accelerator pedal, the speed range may however be shifted to one of 
the 1st to 4th speed ranges. From this control mode, it is possible to 
move to the mode 0 or the mode 3 as shown in FIG. 4. 
In the case of the control mode 2, it is determined in step S190 whether 
any one of the following conditions is established or not as shown in FIG. 
14: (a) the control variable SRT(9) is value 1, (b) the fuzzy input switch 
SW(5) is value 1 and (c) the vehicle speed FV(0) is smaller than the 
predetermined value CFV0 (for example, 10 km/hr). 
The control variable SRT(9) is to store the establishment of the rule 9. As 
shown in Table 6, the establishment of this rule indicates that the mode 
should be changed to the mode 0. The fuzzy input switch SW(5) is to store 
that the throttle opening is large. If even one of the conditions for the 
determination in step S190 is established, step S191 is executed, so that 
the fuzzy input switch SW(0) is set at value 0 and value 5 is set at the 
fuzzy shift position variable SHIFF. This routine is hence ended. In this 
case, the control mode is changed from the downhill weak engine brake mode 
2 to the normal mode 0. 
When the results of the determination in step S190 are "NO", the routine 
advances to step S192 so that it is determined whether all the following 
conditions are established or not: (a) the fuzzy input switch SW(5) is 
value 1, (b) the throttle opening FV(4) is smaller than a predetermined 
value CFV43 (for example 40%), and (c) the fuzzy input switch SW(7) is 
value 0. 
The fuzzy input switch SW(5) is to store that the throttle opening is large 
as described above. Further, the fuzzy input switch SW(7) is to set its 
value at 1 when the accelerator pedal is strongly depressed while an 
engine brake is being applied at the 3rd speed range, and is to store this 
state. Accordingly, the fuzzy input switch SW(7) of 0 means that the 
accelerator pedal was not strongly depressed during application of a 
3rd-speed engine brake. In other words, step S192 determines the driver's 
intention of a medium acceleration. When the results of this determination 
are "YES", the routine advances to step S191 so that the fuzzy input 
switch SW(0) is set at value 0 and value 5 is set as the fuzzy shift 
position variable SHIFF. The mode is therefore changed to the normal mode 
0. In this case, the speed range is determined using an upshift in the 
normal mode so selected, so that the speed range is held at the 3rd speed 
range or upshifted to the 4th speed range in accordance with the throttle 
opening and the vehicle speed. When upshifted to the 4th speed range, it 
is possible to reduce the amount of depression of the accelerator pedal 
and hence to obtain the feeling of an acceleration conforming with the 
driver's intended acceleration on the downhill slope. 
When the results of the determination in step S192 are "NO", the routine 
advances to step S193 Here, it is determined whether the fuzzy input 
switch SW(5) is value 1 or not and whether the throttle opening FV(4) is 
greater than the above-described predetermined value CFV43 (40%) or not. 
This step S193 is to determine the driver's intention for a high 
acceleration. When the results of this determination are "YES", step S194 
is executed to set value 1 at the fuzzy input SW(7) to complete this 
routine. In this case, the 3rd speed range is maintained and the shift 
control in the mode 2 is continued, whereby a high acceleration on a 
downhill slope is performed. Further, the mode 2 is a shift control mode 
in which the vehicles runs down on a gentle downhill road while applying 
an engine brake. If the driver highly accelerates the vehicle while 
driving it as described above, a strong brake is expected to become 
necessary at the next corner. The fuzzy input switch SW(7) is used as a 
flag for commanding a strong engine brake at the time of the strong brake 
which will be required subsequent to the high acceleration. Namely, by 
setting value 1 at the fuzzy input switch SW(7), the determination in the 
above-described step S192 results in "NO" even if the throttle opening is 
large by the fuzzy input switch SW(5) but is smaller than the 
predetermined value CFV43 (40%). As a result, the shift control is not 
performed in the normal mode 0 in step S191 but as will be described 
subsequently herein, the current control mode, that is, the downhill weak 
engine brake mode 2 or the downhill strong engine brake mode 3 is 
executed. This makes it possible to reduce the number of braking 
operations. 
When the results of the determination in step S193 are "NO", step S196 is 
executed to determine whether any one of the control variables SRT(6), 
SRT(7) and SRT(8) storing the establishment of the corresponding rules is 
value 1 or not. These variables are, as described above, to store the 
establishment of the rules 6, 7 and 8, respectively, and as illustrated in 
Table 6, the establishment of any one of these rules indicates that the 
mode 3 should be entered. Accordingly, when the results of the 
determination in step S196 are "YES", the routine advances to step S198, 
where the fuzzy input switch SW(0) is set at value 3 and value 2 is set as 
the fuzzy position variable SHIFF. Accordingly, the routine is ended. The 
mode 3 is, as described above, the mode in which the vehicle is forced to 
run down at the 2nd speed range on a downhill slope. 
When any of the control variables SRT(6), SRT(7) and SRT(8) is not value 1 
and the results of the determination in step S196 are "NO", the routine is 
then ended without any further performance. Namely, the shift control in 
the current control mode 2 is continuously performed to avoid unnecessary 
gear shifts. 
Processing routine in the current mode 3 
When the current shift control is being performed in the control mode 3, 
the speed range is set in accordance with the flow chart of FIG. 15. The 
control mode 3 is, as described above, the downhill strong engine brake 
mode in which the vehicle runs down on a downhill slope while holding the 
2nd speed range. As shown in FIG. 4, it is possible to move from this 
control mode 3 to the mode 0 or the mode 2. 
In the case of the control mode 3, reference is had to FIG. 15. When the 
results of the determination in step S200 are "NO", the routine advances 
to step S202. It is then determined whether or not the fuzzy input switch 
SW(2) is value 1 and whether or not the throttle opening FV(4) is equal to 
or greater than a predetermined value CFV44 (for example, 3%). The fuzzy 
input switch SW(2) is to store that as described above, the weight-grade 
resistance is non-negative. Namely, it is determined in step S202 whether 
or not the road has returned from a downhill road to a flat road and also 
whether the accelerator pedal is slightly depressed. When the results of 
the determination are "YES", the routine advances to step S205 so that the 
fuzzy input switch SW(0) is set at value 2, the value 0 is set to the 
fuzzy input switch SW(5) and the fuzzy shift position variable SHIFF is 
set at value 3 so that the mode is changed to the downhill weak engine 
brake mode 2. 
When the results of the determination in step S202 are "NO", the routine 
advances to step S204 Here, it is determined whether or not the fuzzy 
input switch SW(6) is value 1, whether or not the throttle opening FV(4) 
is smaller than a predetermined value CFV45 (for example, 40%) and whether 
or not the fuzzy input switch SW(8) is value 0. The fuzzy input switch 
SW(6) is, as described above, to store that the throttle opening is 
medium. The fuzzy input switch SW(8) is, as will be described subsequently 
herein, strong depression of the accelerator pedal upon an engine brake at 
the 2nd speed. Accordingly, the determination of these parameters is to 
determine the driver's intention of a medium acceleration. When the 
results of this determination are "YES", the routine advances to step S205 
as described above so that value 2 is set to the fuzzy input switch SW(0), 
value 0 is set to the fuzzy input switch SW(5) and value 3 is set as the 
fuzzy shift position variable SHIFF. Accordingly, the mode is changed to 
the downhill weak engine brake mode 2. In other words, the speed range is 
upshifted from the 2nd speed range to the 3rd speed range so that an 
amount of depression of the accelerator pedal is reflected more clearly 
than the case of the 2nd speed range. It is hence possible to obtain the 
feeling of an acceleration conforming with the driver's intention for an 
acceleration on a downhill slope. 
When the results of the determination in step S204 are "NO", the routine 
advances to step S206, where it is determined whether or not the fuzzy 
input switch SW(6) is value 1 and whether or not the throttle opening 
FV(4) is greater than the above-described predetermined value CFV45 (40%). 
This step is to determine the driver's intention for a high acceleration. 
When the results of this determination are "YES", step S208 is executed so 
that value 1 is set to the fuzzy input switch SW(8). This routine is hence 
ended. In this case, the 2nd speed range is maintained so that the shift 
control in the mode 3 is continued. As a result, a high output conforming 
with the driver's intention for a high acceleration on a downhill slope 
can be obtained. The mode 3 is a shift control mode in which the vehicle 
runs down on a steep downhill road while applying strong engine brakes. If 
the driver suddenly accelerates the vehicle during such driving and then 
enters a corner, a strong brake is expected to be needed. The fuzzy input 
switch SW(8) is also used as a flag for commanding a strong engine brake 
at the time of the strong brake which is applied subsequent to the high 
acceleration. By setting this fuzzy input switch SW(8) at value 1, the 
results of the determination in the above-described step S204 become "NO" 
even if the throttle opening is medium, i.e., smaller than the 
predetermined value CFV45 (40%). Accordingly the current control mode, 
that is, the downhill strong engine brake mode 3 is always executed 
continuously so that a strong engine brake is applied at the 2nd speed 
range. 
When the results of the determination in the above-described step S206 are 
"NO", this routine is ended without setting value 1 to the fuzzy input 
switch SW(8). In this case, the 2nd speed range is maintained to continue 
the shift control in the mode 3, whereby unnecessary gear shifts can be 
avoided. 
Processing routine in the current mode 4 
When the current shift control is performed in the control mode 4, the 
speed range is set in accordance with the flow chart of FIG. 16. The 
control mode 4 is, as described above, the straight uphill mode. Where the 
shift position set based on the shift pattern for the normal mode 0 is the 
4th speed range or the 3rd speed range, the speed range is downshifted to 
the 3rd speed range or the 2nd speed range, respectively, so that a 
necessary drive force can be obtained. From this control mode, it is only 
possible to move to the mode 0 as shown in FIG. 4. 
Namely, as shown in FIG. 16, it is determined in step S210 whether or not 
the throttle opening FV(4) is smaller than a predetermined value CFV45 
(for example, 10%). If the throttle opening FV(4) is smaller than the 
predetermined value CFV45, step S212 is executed so that the fuzzy input 
switch SW(0) is set at value 0 and value 5 is set as the fuzzy shift 
position variable SHIFF. This routine is hence ended. In this case, the 
control mode is moved from the straight uphill mode 4 to the normal mode 
0. 
When the results of the determination in step S210 are "NO", the routine 
advances from step S210 to step S214, where it is then determined whether 
or not the throttle opening FV(4) is smaller than a predetermined value 
CFV46 (for example, 25%) and whether or not the accelerator pedal 
depressing speed FV(5) is lower than a predetermined negative value 
(-CFV5). When both the conditions are met at the same time, the routine 
advances to step S212, where the fuzzy input switch SW(0) is set at value 
0 and value 5 is set as the fuzzy shift position variable SHIFF. As a 
result, the mode is changed to the normal mode 0. 
When the results of the determination in step S214 are "NO", this routine 
is ended without any execution. In this case, the current control mode is 
continued as is. 
Processing routine for the output of a shift position 
When the processing in each mode has been completed as described above, a 
control signal corresponding to a shift position set by the change-over 
command means 8 is outputted to the engagement state control means 9. The 
output procedure of this shift position control signal is designed to 
output the control signal only when it has become necessary to change the 
current shift position as a result of a fuzzy judgment. Further, as 
conditions for performing an actual shifting operation, it is necessary to 
satisfy all the following conditions: (a) a predetermined time (for 
example, 0.5 second) has elapsed since the last shift, (b) the absolute 
value of a steering wheel angle falls between predetermined values and (c) 
the absolute value of a lateral acceleration falls between predetermined 
values. If any one of these conditions is not met, the shift position will 
not be changed. 
This will be described specifically with reference to the flow chart of 
FIG. 17. First, it is determined in step S220 whether or not the 0.5 
second counter SFLG is greater than 0. The 0.5 second counter SFLG is a 
downcounter for determining whether a predetermined time (0.5 second) has 
elapsed from the time point of the last shifting operation, and when a 
shifting operation has been effected, is reset at an initial value. When 
the results of the determination in step S220 are "YES", the predetermined 
time (0.5 second) has not elapsed yet from the last shifting operation and 
in such a case, the counter value SFLG is decremented by value 1 in step 
S221 to end this routine. Even if a new shift position is set before the 
counter value SFLG has not been downcounted to 0, no shifting operation to 
the shift position is performed. 
When a predetermined time has elapsed from the last shifting operation and 
the results of the determination in step S220 are "NO", the routine 
advances to step S222, where it is then determined whether the fuzzy input 
switch SW(0) is a value other than value 0. When the fuzzy input switch 
SW(0) is not any value other than value 0, in other words, is value 0, 
shift control in the mode 0 is meant. In this case, the routine is ended 
without any performance. Since the normal mode 0 is an ordinary shift 
control, it is unnecessary to perform interrupt shift control by fuzzy 
control. As described above, a shift position control signal is outputted 
to the speed-range shifting mechanism 4 in accordance with an ordinary 
shift control program provided separately. 
When the fuzzy input switch SW(0) has been determined to be a value other 
than value 0 and the results of the determination in step S222 are "YES", 
the routine advances to step S224. The smaller one of the fuzzy position 
variable SHIFF and the shift stage SHIF1 set based on the shift pattern 
for the normal mode 0 is selected and is set as a shift position command 
value to the variable N. Where the speed range SHIF1 determined by the 
shift pattern provided for use in the normal mode 0 is smaller even during 
the fuzzy control, the speed range is preferentially chosen. Namely, the 
fuzzy shift position SHIFF is selected only when the fuzzy shift position 
SHIFF is a speed range lower than the shift stage SHIF1 set based on the 
shift pattern for the normal mode 0. 
It is next determined whether or not the thus-selected value of the shift 
position command variable N is equal to the currently-commanded speed 
range SHIF0 (step S226). When they are equal to each other, no shifting 
operation is needed so that the routine is ended. 
When the results of the determination in step S226 are "NO", on the other 
hand, it is determined in step S228 whether or not any one of the 
following conditions has been established: (a) the value of the shift 
position command variable N is greater than a currently-commanded speed 
range SHIF0, (b) the value of the steering wheel angle absolute value 
FV(9) is greater than a predetermined value CFV9 and (c)the lateral 
acceleration absolute value FV(10) is greater than a predetermined value 
CFV10. If any one of the conditions has been established, the 
determination in step S228 results in "YES". In this case, this routine is 
ended without changing the shift position, namely, without changing over 
the speed range. Accordingly, when an upshift is commanded by the shift 
position command variable N, the absolute value of the steering wheel 
angle is greater than the corresponding predetermined value or the 
absolute value of the lateral acceleration is greater than the 
corresponding predetermined value, a shifting operation is prohibited. 
When none of the conditions is determined to have established in step S228 
and the results of the determination in this step are hence "NO", step 
S230 is executed. In step S230, it is determined whether or not the value 
of the shift position command signal N is greater than a value higher by 
one stage than the currently-commanded speed range SHIF0, in other words, 
whether or not the speed range is upshifted by two stages or more at once 
by the current shift position command variable N. If the speed range is 
upshifted by two stages or more at once by the current shift position 
command variable N, the command variable N is set at value (SHIF0+1) in 
step S232 to limit the current upshifting operation to the speed range 
higher by only one stage than the currently-commanded speed range SHIF0, 
and the routine then advances to step S240 to be described subsequently 
herein. 
When the results of the determination in step S230 are "NO", on the other 
hand, the routine advances to step S234. It is now determined whether or 
not the value of the shift position command signal N is smaller than a 
value lower by one stage than the currently-commanded speed range SHIF0, 
in other words, whether or not the speed range is downshifted by two 
stages or more at once by the current shift position command variable N. 
If the speed range is downshifted by two stages or more at once by the 
current shift position command variable N, the command variable N is set 
at value (SHIF0-1) in step S236 to limit the current downshifting 
operation to the speed range lower by only one stage than the 
currently-commanded speed range SHIF0, and the routine then advances to 
step S240 to be described subsequently herein. 
When the results of the determination in step S234 are "NO", the value of 
the shift position command variable N is maintained unchanged and the 
routine then advances to step S240. 
After resetting the value of the 0.5 second counter SFLG to a predetermined 
value XT1 (a value corresponding to 0.5 second) in step S240, step S242 is 
executed to output a shift position control signal, which corresponds to 
the shift position command variable N, to the speed-range shifting 
mechanism 4. Accordingly, this routine is ended. 
The shift position control signal outputted in step S240 has been obtained 
by performing computation on the basis of fuzzy control. This signal has 
higher precedence than the shift position control signal outputted in the 
normal mode 0 and is executed interrupting the shift position control 
signal outputted in the normal mode 0. 
Shift controlling hydraulic pressure command routine 
The routine for commanding a shift controlling hydraulic pressure normally 
sets a hydraulic pressure control pattern A [see FIG. 3(b)], which places 
importance on the response of each change-over in speed range, by the 
engagement stage control means 9. However, in the case of a downshift on a 
downhill road, said downshift being performed without depression of the 
accelerator pedal by the driver and being hardly predictable by the 
driver, the hydraulic control pattern B which places importance on the 
smoothness of each change-over in speed range [see FIG. 3(b)] is set. 
As is illustrated, for example, in FIG. 18, it is first determined in step 
S260 if the shift position control signal has been outputted. If the 
output of the shift position control signal is determined, the routine 
advances to step S262, where it is then determined whether the fuzzy input 
switch SW(0) has been set at 2 or 3. If the fuzzy input switch SW(0) has 
been set at 2, it is meant that the control mode 2 has been selected. If 
the fuzzy input switch SW(0) has been set at 3, on the other hand, it is 
meant that the control mode 3 has been selected. The control mode 2 is the 
downhill weak engine brake mode whereas the control mode 3 is the downhill 
strong engine brake mode. Each of these modes corresponds to the downhill 
downshift mode. 
When the results of the determination in step S262 are "YES", the routine 
advances to step S264, where it is then determined whether the throttle 
opening is small or not and also whether the accelerator pedal depression 
speed (note: the absolute value of the speed is used here) is small or 
not. The determination of whether the throttle opening is small or not and 
also whether the accelerator pedal depression speed is small or not can be 
conducted, for example, by setting appropriate reference values for the 
determination of the throttle opening and the accelerator pedal depressing 
speed and comparing detected throttle opening and accelerator depressing 
speed with these reference values, respectively. 
This determination in step S264 is to determine whether or not a throttle 
operation (accelerator pedal operation) has not been performed. This is 
equivalent to the determination of whether or not the downshift on the 
downhill road to be performed at this time is hardly predictable by the 
driver. Upon conducting a downshift on a downhill road, the throttle 
opening is usually small. Even if the throttle opening is small, the 
driver may suddenly release the depression of the accelerator pedal in 
some instances. This release is reflected as a corresponding negative 
value in the accelerator depression speed. This sudden release of the 
depression of the accelerator pedal can be estimated as the driver's 
attempt or intention to reduce the vehicle speed. In this case, the 
downshift on the downhill road is considered to be predictable by the 
driver. 
When the results of the determination in step S264 are "YES", the routine 
advances to step S266, where a control signal is then outputted to the 
engaging force regulating means 5 to regulate the hydraulic pressure to 
the exclusive shift controlling hydraulic pressure, in other words, to 
perform the regulation of the hydraulic pressure in accordance with the 
hydraulic pressure control pattern B which places importance on the 
smoothness of each change-over in speed range [see FIG. 3(b)]. 
When the results of the determination in any one of steps S260, S262 and 
S264 are "NO", the routine advances to step S268, where a control signal 
is then outputted to the engaging force regulating means 5 to regulate the 
hydraulic pressure to the normal shift controlling hydraulic pressure, in 
other words, to perform the regulation of the hydraulic pressure in 
accordance with the hydraulic pressure control pattern A which places 
importance on the response of each change-over in speed range [see FIG. 
3(b)]. 
The shift control system and methods according to the one embodiment of the 
present invention, which are suited for use with a vehicle automatic 
transmission, are constructed as described above, so that when running, 
for example, on a downhill slope, an optimal speed range can always be set 
by taking into parallel consideration the driving behavior intended by the 
driver, the conditions of a road and the state of operation of the 
vehicle, for example, a speed range can be set in conformity with the 
driver's intended driving behavior such as an acceleration or deceleration 
of the vehicle. 
If the driver's manner of driving or the conditions of a road do not desire 
an acceleration but rather desires a deceleration, for example, upon 
running down on a downhill slope, the downhill weak engine brake mode 
(i.e., the control mode 2) or the downhill strong engine brake mode (i.e., 
the control mode 3) is selected to forcedly perform a downshift. This 
makes it possible to allow the vehicle to run down while applying engine 
brakes, thereby minimizing braking operations to be needed by the driver 
and hence facilitating the driving on the downhill slope. 
If the driver cannot predict a downshift on a downhill road, the hydraulic 
pressure to each corresponding engaging element 3A is controlled at the 
time of the downshift in accordance with the hydraulic pressure control 
pattern B [see FIG. 3(b)] which places importance on the smoothness of 
each change-over in speed range. 
As a result, as illustrated in FIG. 3(e), a sudden change in the torque of 
the drive torque, said change occurring upon full engagement of a clutch 
upon completion of a shifting operation, is reduced from T.sub.1 to 
T.sub.2, thereby reducing a shift shock and avoiding a sense of 
incongruity to the driver at the time of the shifting. 
If as illustrated by way of example in FIG. 20, the vehicle speed increases 
from point A to point D on a downhill slope although the driver does not 
operates the throttle valve, a downshifting operation is performed because 
of the control making use of the fuzzy inference and the driver is hence 
surprised, although an upshift would be performed if the vehicle were 
running on a flat road. The present invention can avoid such a surprise. 
As a consequence, the smoothness of shifting operations, which is an 
inherent characteristic feature of an automatic transmission, can be 
assured, so that the drivability and hence the riding comfort can be 
improved. 
In the case of such shifting as causing no troublesome shift shock or where 
the driver can predict a downshift even if the downshift is effected on a 
downhill road, the hydraulic pressure to each corresponding engaging 
element 3A is controlled at the time of the shifting in accordance with 
the ordinary hydraulic pressure control pattern A [see FIG. 3(b)] which 
places importance on each change-over in speed range. This makes it 
possible to promptly perform the shifting operation without giving a sense 
of incongruity to the driver, whereby the running performance of the 
vehicle can be improved. 
The shift control system and methods according to the present invention, 
which are suited for use with the vehicle automatic transmission, are 
intended to avoid by the use of the fuzzy inference a sense of incongruity 
of a shift shock to the driver upon conducting a downshift to apply an 
engine brake on a downhill road. It is to be noted that the shift control 
itself by the fuzzy inference, that is, the fuzzy control per se is not 
limited to that specifically employed in the above-described embodiment. 
In view of an application to other fuzzy controls, a shift control 
hydraulic pressure command routine having still broader general 
applicability will now be considered. For example, it is possible to 
contemplate of such a flow chart as shown in FIG. 19. As is illustrated in 
FIG. 19, data from individual detection means such as the grade detection 
means 10, the meandering degree detection means 11, the vehicle speed 
detection means 12, the throttle operation detection means (throttle 
opening sensor) 13 and the brake switch 14 are read (step S300). Based on 
these data, a target speed range S.sub.N is computed by the first 
speed-range setting means 7A in accordance with the normal shift pattern 
(step S302) and a target speed range S.sub.F is also computed by fuzzy 
inference at the second speed-range setting means 7B (step S304). 
It is next determined if the target speed range S.sub.F by the fuzzy 
inference is lower than the target speed range S.sub.N by the normal shift 
pattern (step S306). Also determined are if a current throttle opening 
(which corresponds to the amount of current depression of the accelerator 
pedal) is smaller than a predetermined reference value .theta..sub.0 for 
determination (step S308) and also if the rate of a change in throttle 
opening (which corresponds to an accelerator pedal depressing speed) is 
smaller than a predetermined reference value .theta..sub.0 ' for 
determination (step S310). 
When the determination in each of steps S306, S308 and S310 has resulted in 
"YES", the routine advances to S312, where a control signal is then 
outputted to the engaging force regulating means 5 to regulate the 
hydraulic pressure to an exclusive shift controlling hydraulic pressure, 
in other words, to perform the regulation of the hydraulic pressure in 
accordance with the hydraulic pressure control pattern B which places 
importance on the smoothness of each change-over in speed range [see FIG. 
3(b)]. 
When the results of the determination in any one of steps S306, S308 and 
S310 are "NO", the routine advances to step S314, where a control signal 
is then outputted to the engaging force regulating means 5 to regulate the 
hydraulic pressure to a normal shift controlling hydraulic pressure, in 
other words, to perform the regulation of the hydraulic pressure in 
accordance with the hydraulic pressure control pattern A which places 
importance on the response of each change-over in speed range [see FIG. 
3(b)].