Transmission control apparatus for nonstage transmission of vehicles

To provide the driver with a driving feeling which faithfully keeps up with various running states of the vehicle and running requirements of the driver by finding an accommodation coefficient indicating a running state by fuzzy inference. A target rotational speed of the engine is set on the basis of the accommodation coefficient found during the previous step. The change-gear ratio of the nonstage transmission is controlled so as to result in the target rotational speed of the engine set at the immediately previous step. A transmission control unit includes an accommodation coefficient fuzzy-inferring control, a target engine rotational speed setting control and a change-gear ratio controlling member. Inputting the change-gear ratio R, the throttle opening O, the speed v of the vehicle and the change in vehicle speed per unit time (or the acceleration) G, the accommodation coefficient fuzzy-inferring control finds a rate of change A in accommodation coefficient A by using fuzzy rules set in advance. The target engine rotational speed setting control sets a target rotational speed NE of an engine on the basis of at least the accommodation coefficient A and the speed V of the vehicle. The change-gear ratio controlling member controls the change-gear ratio R of the non-state transmission to provide a rotational speed N of the engine equal to the target engine rotational speed NE.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a transmission control apparatus of a 
nonstage transmission, wherein a target rotational speed of the engine or 
a range of rotational-speed values of the engine is set on the basis of 
the speed of the vehicle and an accommodation coefficient indicating the 
running state of the vehicle. The change-gear ratio of the nonstage 
transmission is controlled so as to achieve the target rotational speed of 
the engine or the range of rotational-speed values of the engine. In 
particular, the present invention relates to a transmission control 
apparatus of a nonstage transmission for vehicles wherein the 
accommodation coefficient is found by fuzzy inference based on demanded 
engine-output quantities such as the throttle opening and input quantities 
related to the running state such as the speed of the vehicle, the 
change-gear ratio and the rate of change in vehicle speed or the 
acceleration so as to provide smooth transmission control which can keep 
up with a variety of running states of the vehicle. 
2. Description of the Background Art 
A transmission control apparatus for a vehicle having a nonstage 
transmission, wherein a target rotational speed of the engine or a target 
speed ratio is set as a function of an induction-system throttle opening 
and vehicle speed, such as the one disclosed in Japanese Patent Laid Open 
No. Sho59-114850, is generally known. It should be noted that the speed 
ratio means a ratio of the rotational speed on the output side of the 
nonstage transmission to the rotational speed of the engine. 
SUMMARY AND OBJECTS OF THE INVENTION 
In the case of the conventional transmission apparatus wherein a target 
rotational speed of the engine or a target speed ratio is set as a 
function of an induction-system throttle opening and vehicle speed, when 
the engine is set on the assumption of an ordinary running mode such as 
the level-land running mode, feedback control is inevitably carried out in 
another mode such as the downhill-road mode or the uphill-road mode in 
order to make a transition from the ordinary running mode to the other 
mode. As a result, the conventional transmission apparatus has a problem 
that it is difficult to provide the driver with a driving feeling in 
accordance with what is desired by the driver. 
Addressing the problem described above, with the present invention, an 
attempt is made to provide the driver with a driving feeling adjusted to 
the running state of the vehicle by introducing a new conceptual quantity 
called an accommodation coefficient for indicating the running state 
wherein the driving feeling is obtained through the execution of the steps 
of: 
presetting a target rotational speed of the engine or a range of 
rotational-speed values of the engine on the basis of the speed of the 
vehicle and the accommodation coefficient; and 
changing the target rotational speed of the engine in accordance with the 
accommodation coefficient. 
To be more specific, it is an object of the present invention to provide 
the driver with a driving feeling faithfully keeping up with a variety of 
running states of the vehicle and running requirements of the driver by 
executing the steps of: 
directly computing the accommodation coefficient by fuzzy inference based 
on fuzzy rules set in advance with demanded engine-output quantities such 
as the throttle opening, the speed of the vehicle and the change-gear 
ratio as well as a variety of kinds of data related to the running state 
such as and the rate of change in vehicle speed or the acceleration used 
as input conditions or, as an alternative, computing the accommodation 
coefficient after finding rates of change in accommodation coefficient by 
fuzzy inference; and 
obtaining values of the accommodation coefficient faithfully keeping up 
with the various running states of the vehicle and the running 
requirements of the driver and executing transmission control to result in 
rotational speeds of the engine set on the basis of these accommodation 
coefficient values. 
In order to solve the problem described above, the present invention 
provides a transmission control apparatus for a nonstage transmission of a 
vehicle characterized in that the transmission control apparatus 
comprises: 
a target engine rotational-speed setting means for setting a target 
rotational speed of the engine or a range of rotational-speed values of 
the engine in accordance with at least the speed of the vehicle and an 
accommodation coefficient indicating the running state of the vehicle; 
an accommodation coefficient fuzzy-inferring means for inferring an 
accommodation coefficient from inputs including demanded engine-output 
quantities, the speed of the vehicle, the change-gear ratio and the rate 
of change in vehicle speed or the acceleration on the basis of fuzzy rules 
set in advance or, as an alternative, inferring with the rate of change in 
accommodation coefficient and then deriving an accommodation coefficient 
from the inferred rate of change; and 
a change-gear-ratio controlling means for controlling the change-gear ratio 
of the nonstage transmission on the basis of the accommodation coefficient 
derived by the accommodation coefficient fuzzy-inferring means so as to 
result in the target rotational speed of the engine or the range of 
rotational-speed values of the engine set by the target engine 
rotational-speed setting means. 
The transmission control apparatus for a nonstage transmission of a vehicle 
provided by the present invention executes the steps of: 
inferring an accommodation coefficient from inputs including demanded 
engine-output quantities, the speed of the vehicle, the change-gear ratio 
and the rate of change in vehicle speed or the acceleration on the basis 
of fuzzy rules set in advance or, as an alternative, inferring the rate of 
change in accommodation coefficient and then deriving an accommodation 
coefficient from the inferred rate of change; 
setting a target rotational speed of the engine or a range of 
rotational-speed values of the engine in accordance with at least the 
speed of the vehicle and the accommodation coefficient inferred or derived 
at the previous step; and 
controlling the change-gear ratio of the nonstage transmission so as to 
result in the target rotational speed of the engine or the range of 
rotational-speed values of the engine set at the immediately previous 
step. 
The transmission control apparatus provided by the present invention is 
configured so that a target rotational speed of the engine or a range of 
rotational-speed values of the engine is set in accordance with at least 
the speed of the vehicle and an accommodation coefficient which indicates 
the running state of the vehicle. Accordingly, values of the accommodation 
coefficient faithfully keeping up with the various running states of the 
vehicle and the running requirements of the driver can be obtained and 
transmission control can then be executed to result in rotational speeds 
of the engine set on the basis of these accommodation coefficient values. 
As a result, the driver is provided with a driving feeling which 
faithfully keeps up with various running states of the vehicle and the 
running requirements of the driver. 
Further scope of applicability of the present invention will become 
apparent from the detailed description given hereinafter. However, it 
should be understood that the detailed description and specific examples, 
while indicating preferred embodiments of the invention, are given by way 
of illustration only, since various changes and modifications within the 
spirit and scope of the invention will become apparent to those skilled in 
the art from this detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A diagram of an overall configuration of a transmission control apparatus 1 
provided by the present invention for nonstage transmissions of vehicles 
is shown in FIG. 1. 
As shown in FIG. 1, the transmission control apparatus 1 comprises, among 
other components, machinery 2 such as an engine, a nonstage transmission 3 
with a loop belt, a centrifugal clutch 4 and a transmission control unit 5 
adopting the fuzzy inference. 
An output axis 2a of the engine 2 is linked to an input axis 3a of the 
nonstage transmission 3 whereas an output axis 3b of the nonstage 
transmission 3 is joined to an input axis 4a of the centrifugal clutch 4. 
The output axis 4a of the centrifugal clutch 4 is so configured that 
rotative power is transmitted to a driving wheel, not shown in FIG. 1, 
through a gear mechanism and other parts which are also not shown in FIG. 
1. 
As described earlier, the nonstage transmission 3 has a loop belt 8 which 
rotates between a pair of driving pulleys 6 and a couple of passive 
(driven) pulleys 7. The loop belt 8 has a cross-sectional area that 
resembles an isosceles trapezoid. The nonstage transmission 3 drives an 
actuator 9, varying the pulley gap between the two driving pulleys 6. In 
the case of the transmission control apparatus 1 shown in FIG. 1, the 
driving pulley 6a on the right side is fixed and the driving pulley 6b on 
the left side can be moved in the axial direction to vary the gap between 
the two driving pulleys 6a and 6b. Much like the driving pulleys 6, one of 
the two passive pulleys 7 is fixed on the output axis 3b while the other 
one is installed in such a way that it can be moved in the axial 
direction. The surface of the driving pulley 6a in contact with the loop 
belt 8 is taper. Likewise, the surface of the driving pulley 6b in contact 
with the loop belt 8 is also taper. These contact surfaces each become 
gradually smaller toward the axis 3a so that the distance from one of the 
contact surfaces to the other increases in the centrifugal radial 
direction. Much like the driving pulley 6a, the surface of the passive 
pulley 7a in contact with the loop belt 8 is taper. 
Likewise, the surface of the passive pulley 7b in contact with the loop 
belt 8 is also taper. These contact surfaces each become gradually smaller 
toward the axis 3b so that the distance from one of the contact surfaces 
to the other increases in the centrifugal radial direction. The radius of 
the loop belt 8 in contact with the driving pulleys 6 thus decreases as 
the distance from one of the contact surfaces of the driving pulleys 6 to 
the other increases and vice versa. Similarly, the radius of the loop belt 
8 in contact with the passive pulleys 7 thus also decreases as the 
distance from one of the contact surfaces of the passive pulleys 7 to the 
other increases and vice versa. The changes in radii result in variations 
in change-gear ratio and transmission torque. 
The actuator 9 is equipped with a motor and a driving mechanism for 
shifting the driving pulley 6b by means of the rotational output of the 
motor. To be more specific, the actuator 9 controls the position of the 
driving pulley 6b in accordance with a transmission command 5a issued by a 
transmission control unit 5. 
A stroke sensor 10 is used for monitoring the position of the driving 
pulley 6b, supplying an electrical signal 10a representing the position to 
the transmission control unit 5. 
An engine rotational speed sensor 11 provides the transmission control unit 
5 with a pulse signal 11a, the period of which represents the rotational 
speed of the output axis 2a of the engine 2. Rotational speed means the 
number of rotations per unit time. 
A throttle-opening sensor 12 is used for monitoring the throttle opening of 
an induction system employed in the engine 2, providing the transmission 
control unit 5 with an electrical signal 12a which represents the throttle 
opening. In this embodiment, the throttle opening of the engine 2 is 
regarded as the quantity of a demanded output of the engine 2. 
It should be noted that the quantity of the demanded output of the engine 
can also be detected by means of an inflow-air-quantity detector or a 
negative pressure detector for monitoring the negative pressure of an 
induction pipe. 
The transmission control unit 5 comprises a change-gear ratio detecting 
means 13, a throttle-opening detecting means 14, an engine rotational 
speed detecting means 15, a vehicle-speed detecting means 16, a vehicle 
speed change detecting means 17, an accommodation coefficient 
fuzzy-inferring means 18, a target engine rotational speed setting means 
19 and a change-gear ratio controlling means 20. 
The change-gear ratio detecting means 13 is provided with a pulley position 
and change-gear ratio data table showing relations between the position of 
the driving pulley 6b and the change-gear ratio R. The pulley position and 
change-gear ratio data table is stored in advance in the change-gear ratio 
detecting means 13. Based on the electrical signal 10a output by the 
stroke sensor 10, the change-gear ratio detecting means 13 outputs digital 
information on the change-gear ratio R of the nonstage transmission 3. It 
should be noted that the digital information is referred to hereafter 
merely as the change-gear ratio R. 
It should be noted that the change-gear ratio detecting means 13 typically 
inputs the rotational speeds on the input and output sides of the nonstage 
transmission 3 and finds the change-gear ratio, a ratio of the former to 
the latter, by calculation. As described above, rotational speed means the 
number of rotations per unit time. In this case, an output rotation sensor 
is installed on the output axis 3b of the nonstage transmission 3 for 
monitoring the rotational speed of the output axis 3b. It should be noted 
that this output rotation sensor itself is not shown in FIG. 1. The 
change-gear ratio R is then found as a ratio of a detection output 
generated by the engine rotational speed sensor 11 to a detection output 
generated by this output rotation sensor. It should be noted that, in the 
case of the nonstage transmission wherein the change-gear ratio R is found 
as a ratio of the rotational speed on the input side to that on the output 
side thereof as described above, the stroke sensor 10 is not required. 
The throttle-opening detecting means 14 outputs digital information e on 
the throttle opening based on the electrical signal 12a output by the 
throttle-opening sensor 12. The digital information .THETA. is referred to 
hereafter merely as the throttle opening. It should be noted that, in this 
embodiment, the throttle opening is expressed in terms of percents with 0% 
and 100% used for representing the minimum and maximum throttle openings, 
respectively. 
Typically, the throttle-opening sensor 12 employs a potentiometer, a 
variable resistor interlocked with the opening of an induction throttle, 
outputting a voltage from the potentiometer which represents the throttle 
opening. In this case, the throttle-opening detecting sensor 14 is 
provided with an A/D converter for converting the voltage representing the 
throttle opening into a digital voltage signal, and a throttle-opening 
table for storing relations between the digital voltage signal output by 
the A/D converter and the throttle opening in advance. Receiving a digital 
voltage signal, the throttle-opening detecting sensor 14 searches the 
throttle-opening table for a value of the throttle opening corresponding 
to the digital voltage signal, and if necessary, the throttle opening 
.THETA. is found by interpolation of results of the search operation. 
The engine rotational speed detecting means outputs information N on the 
rotational speed of the engine 3 which is found from the pulse period of 
the pulse signal 11a received from the engine rotational speed sensor 11. 
By the rotational speed, the number of rotations per unit time is meant as 
described earlier. It should be noted that the information N is referred 
to hereafter merely as the number of engine rotations. 
The vehicle-speed detecting means 16 outputs digital information V on the 
speed of the vehicle which is found from a detection signal 21a generated 
by the vehicle-speed sensor 21. It should be noted that the digital 
information V is referred to hereafter merely as the speed of the vehicle. 
The vehicle-speed sensor 21 is typically a transducer which is used for 
generating a train of periodical pulses at time intervals each 
representing the rotational speed of the output axis 4b employed in the 
centrifugal clutch 4 or the rotational speed of the wheels employed by the 
vehicle equipped with the transmission control apparatus. 
As described above, the speed V of the vehicle is found from the detection 
signal 21a output by the vehicle-speed sensor 21 and, typically, the 
detection signal 21a is a train of pulses generated at intervals each 
representing the rotational speed, that is, a train of pulses with a 
period inversely proportional to the rotational speed. In this case, the 
speed V of the vehicle can be found by measuring the time gap between two 
consecutive pulses of the pulse train. With this technique, however, an 
average speed of the vehicle cannot necessarily be obtained. Therefore, 
the time gap between two consecutive pulses is measured N times and then 
an average speed of the vehicle is found by calculation including the 
division of a sum of the measured time gaps by N. 
As an alternative, the time gap between the first and the last of M 
consecutive pulses is measured and then an average speed of the vehicle is 
found by computation including the division of the measured time gap by 
(M-1). 
The vehicle-speed-change detecting means 17 computes a change in vehicle 
speed .DELTA.V from values of the vehicle speed V sequentially output by 
the vehicle-speed detecting means 16 and then finds the acceleration G, a 
change in vehicle speed per unit time. To be more specific, a current 
vehicle speed and a previous vehicle speed are obtained to give a 
difference or a change in vehicle speed .DELTA.V and, at the same time, a 
period between points of time at which the current and previous vehicle 
speeds are obtained is measured. The change in vehicle speed per unit time 
(or the acceleration) G is then calculated by dividing the change in 
vehicle speed .DELTA.V by the measured period between the two points of 
time. 
In this embodiment, the change in vehicle speed per unit time G (or the 
acceleration) is computed from variations in vehicle speed. It should be 
noted, however, that an acceleration sensor can also be employed as an 
alternative for monitoring the acceleration and the monitored acceleration 
can be used as the change in vehicle speed per unit time G. 
In addition, the change in vehicle speed .DELTA.V can be calculated as 
differences between vehicle speeds obtained at time intervals determined 
in advance. In this case, the calculated change in vehicle speed .DELTA.V 
can be treated as a quantity corresponding to the change in vehicle speed 
per unit time (or the acceleration) G. 
Inputting the change-gear ratio R, the throttle opening .THETA., the speed 
V of the vehicle and the change in vehicle speed per unit time (or the 
acceleration) G, the accommodation coefficient fuzzy-inferring means 18 
infers a rate of change .DELTA.A in accommodation coefficient A by using 
fuzzy rules set in advance. The inferred rate of change .DELTA.A in 
accommodation coefficient A is then used to calculate a most recent value 
of the accommodation coefficient A. 
A block diagram of the configuration of the accommodation coefficient 
fuzzy-inferring means is shown in FIG. 2. 
As shown in FIG. 2, the configuration of the accommodation coefficient 
fuzzy-inferring means includes an accommodation coefficient change-rate 
fuzzy-inferring unit 18a and an accommodation coefficient processing unit 
18b. 
The accommodation coefficient change-rate fuzzy-inferring unit 18a is 
further equipped with a plurality of fuzzy rules 18c, a plurality of 
membership functions 18d, a membership-value computing means 18e and an 
output-value inferring means 18f. 
An explanatory diagram showing actual examples of the fuzzy rules is shown 
in FIG. 3. 
In this embodiment, eight fuzzy rules are provided for inferring the rate 
of change .DELTA.A in accommodation coefficient A. 
Rules 1 and 2 focus on relations between the speed V of the vehicle and the 
change-gear ratio R. Rules 3 to 6 focus on relations between the throttle 
opening .THETA. and the speed V of the vehicle. Rules 7 and 8 focus on 
relations between the throttle opening .THETA. and the change-gear ratio 
R. As shown in FIG. 3, the rules are each described in an IF-THEN format. 
Explanatory diagrams showing actual examples of fuzzy variables and the 
membership functions are depicted in FIG. 4. 
In this embodiment, membership functions for the speed V of the vehicle, 
the change-gear ratio R, the throttle opening .THETA. and the rate of 
change in vehicle speed per unit time (or the acceleration) G are provided 
as antecedent membership functions while that for the rate of change 
.DELTA.A in accommodation coefficient A is provided as consequent 
membership functions. 
In the case of a membership function for the speed of the vehicle shown in 
FIG. 4(a), the horizontal and vertical axes represent the speed V of the 
vehicle and the grade (or the degree to which the speed of the vehicle 
belongs to a fuzzy set), respectively. The membership function defines the 
degree to which a value of the speed V of the vehicle belongs to grades 
`Low` and `High` fuzzy sets of small and large values of the speed V of 
the vehicle, respectively. The membership function for the change-gear 
ratio R shown in FIG. 4(b) defines the degree to which a value of the 
change-gear ratio R in the range 0 to 100% (or Low to Top) belongs to 
grades `Low`, `Not Very Low`, `Not Low` and `High`, the fuzzy sets for 
small, not very small, not small and large values of the change-gear ratio 
R, respectively. 
The membership function for the throttle opening .THETA. shown in FIG. 4(c) 
defines the degree to which a value of the throttle opening .THETA. 
belongs to grades `Close`, `Low` and `High`. The grade `Close` is a fuzzy 
set for the closed throttle opening .THETA. whereas the grades `Low` and 
`High` are fuzzy sets for small and large values of the throttle opening 
.THETA., respectively. 
The membership function for the rate of change in vehicle speed (the 
acceleration) G shown in FIG. 4(d) defines the degree to which a value of 
the rate of change in vehicle speed (the acceleration) G belongs to grades 
`Negative Big` and `Positive Big`, the fuzzy sets for large values in the 
negative and positive directions of the rate of change in vehicle speed 
(the acceleration) G, respectively. 
The membership function for the rate of change .DELTA.A in accommodation 
coefficient A shown in FIG. 4(e) defines the degree to which a value of 
the rate of change .DELTA.A in accommodation coefficient A of the 
horizontal axis belongs to grades `Fast Down`, `Slow Down`, `Slow Up`, 
`Middle Up` and `Fast Up`, the fuzzy sets for rapidly decreasing, slowly 
decreasing, slowly increasing, increasing and rapidly increasing values of 
the rate of change .DELTA.A in accommodation coefficient A, respectively. 
Inputting values of the speed V of the vehicle, the change-gear ratio R, 
the throttle opening .THETA. and the rate of change in vehicle speed (or 
the acceleration) G, the membership-value computing means 18e inside the 
accommodation coefficient change-rate fuzzy-inferring unit 18a shown in 
FIG. 2 finds their values of membership to the fuzzy sets for the speed V 
of the vehicle, the change-gear ratio R, the throttle opening .THETA. and 
the rate of change in vehicle speed (acceleration) G are shown in FIG. 
4(a) to FIG. 4(d). The membership values are used in conjunction with the 
fuzzy rules shown in FIG. 3 and the consequent conditions (or the fuzzy 
sets of the rate of change .DELTA.A in accommodation coefficient A shown 
in FIG. 4(e) as described earlier) for determining a membership function 
of the rate of change .DELTA.A in accommodation coefficient A for each of 
the fuzzy rules. 
From the membership functions of the rate of change .DELTA.A in 
accommodation coefficient A determined for the individual fuzzy rules, the 
output-value inferring means 18f infers a synthetic rate of change by 
means of the Min-Max method of elastic center. From the inferred synthetic 
rate of change, the output-value inferring means 18f outputs a value of 
the rate of change .DELTA.A in accommodation coefficient A. 
By using values of the rate of change .DELTA.A in accommodation coefficient 
A supplied sequentially one after another by the accommodation coefficient 
change rate fuzzy-inferring unit 18a, the accommodation coefficient 
processing unit 18b corrects the value of the accommodation coefficient A 
computed previously to find and output the most recent value of the 
accommodation coefficient A. 
In this embodiment, the rate of change .DELTA.A in accommodation 
coefficient A is found as a rate of change expressed in terms of percents. 
The accommodation coefficient processing unit 18b measures a period 
between points of time at which immediately previous and current values of 
the rate of change .DELTA.A in accommodation coefficient A are output. The 
accommodation coefficient processing unit 18b then computes the product of 
the period between the points of time and the current value of the rate of 
change .DELTA.A in the accommodation coefficient A to give a change in the 
accommodation coefficient A which is added to or subtracted from the value 
of the accommodation coefficient A computed previously to result in a most 
recent value of the accommodation coefficient A. It should be noted that 
the initial value of the accommodation coefficient A is set at 0%. 
It should be kept in mind that, in this embodiment, the accommodation 
coefficient A is treated by expressing the values thereof in terms of 
percents in a range between a minimum of 0% and a maximum of 100%. 
Accordingly, the accommodation coefficient processing unit 18b rounds up 
negative values of the accommodation coefficient A found by calculation to 
the minimum 0%. On the other hand, the accommodation coefficient 
processing unit 18b rounds down values of the accommodation coefficient A 
greater than 100% found by calculation to the maximum 100%. 
A block diagram of the configuration of the target engine rotational speed 
setting means 19 is shown in FIG. 5. 
As shown in FIG. 5, the target engine rotational speed setting means 19 
comprises a target engine rotational speed range setting unit 19a and a 
target engine rotational speed processing unit 19b. 
The target engine rotational speed range setting unit 19a is further 
equipped with a target engine rotational speed upper limit setting unit 
19c, a target engine rotational speed lower limit setting unit 19d, a 
target engine rotational speed upper limit data table 19e and a target 
engine rotational speed lower limit data table 19f. 
Graphs representing the contents of the target engine rotational speed 
upper limit data table 19e and the target engine rotational speed lower 
limit data table 19f are shown in FIGS. 6 and 7 respectively. 
The target engine rotational speed upper limit data table 19e is used for 
storing upper-limit data set in advance on the basis of three parameters 
(or input conditions): the speed V of the vehicle, the accommodation 
coefficient A and the throttle opening .THETA.. The data is set in such a 
way that, the higher the speed V of the vehicle and the greater the 
accommodation coefficient A, the greater the target engine rotational 
speed upper limit value NU. Furthermore, the data is also set so that, the 
greater the throttle opening .THETA., the greater the target engine 
rotational speed upper limit value NU for the same values of the speed V 
of the vehicle and the accommodation coefficient A. 
Likewise, the target engine rotational speed lower limit data table 19f is 
used for storing lower limit data set in advance on the basis of two 
parameters (or input conditions): the speed V of the vehicle and the 
accommodation coefficient A. The data is set in such a way that, the 
higher the speed V of the vehicle and the greater the accommodation 
coefficient A, the greater the target engine rotational speed lower limit 
value NL. 
FIG. 8 is an explanatory diagram used for describing an eight-point 
interpolation technique for finding a target engine rotational speed upper 
limit value NU. 
Receiving the speed V of the vehicle supplied by the vehicle-speed 
detecting means 16, the accommodation coefficient A supplied by the 
accommodation coefficient fuzzy-inferring means 18 and the throttle 
opening e supplied by the throttle-opening detecting means 14, the target 
engine rotational speed upper limit setting unit 19c shown in FIG. 5 picks 
up a couple of the closest points sandwiching the speed V of the vehicle, 
a couple of the closest points sandwiching the accommodation coefficient A 
and a couple of the closest points sandwiching the throttle opening 
.THETA.. The target engine rotational speed upper limit setting unit 19c 
then reads three pairs of engine rotational speed upper limit data from 
the target engine rotational speed upper limit data table 19e with each 
pair corresponding to each of the couples of closest points picked up as 
described above. The three pairs of engine rotational speed upper limit 
data read from the target engine rotational speed upper limit data table 
19e each serve as the limits of a range of values. The ranges of values 
are drawn in FIG. 8 as three adjacent sides of a cube with eight corner 
points P1 to P8. The eight points P1 to P8 are used as a base by the 
eight-point interpolation technique for finding the target engine 
rotational speed upper limit value NU. 
FIG. 9 is an explanatory diagram used for describing a four-point 
interpolation technique for finding a target engine rotational speed lower 
limit value NL. 
Receiving the speed V of the vehicle supplied by the vehicle-speed 
detecting means 16 and the accommodation coefficient A supplied by the 
accommodation coefficient fuzzy-inferring means 18, the target engine 
rotational speed lower limit setting unit 19d shown in FIG. 5 picks up a 
couple of the closest points sandwiching the speed V of the vehicle and a 
couple of closest points sandwiching the accommodation coefficient A. The 
target engine rotational speed lower limit setting unit 19d then reads two 
pairs of engine rotational speed lower limit data from the target engine 
rotational speed lower limit data table unit with each pair corresponding 
to each of the couples of closest points picked up as described above. The 
two pairs of engine rotational speed lower limit data read from the target 
engine rotational speed lower limit data table 19f each serve as the 
limits of a range of values. The ranges of values are drawn in FIG. 8 as 
two adjacent sides of a square with four corner points Q1 to Q4. The four 
points Q1 to Q4 are used as a base by the four-point interpolation 
technique for finding the target engine rotational speed lower limit value 
NL. 
The target engine rotational speed processing unit 19b shown in FIG. 5 is 
equipped with a target engine rotational speed processing means 19g and a 
target engine rotational speed change rate data table 19h. 
The target engine rotational speed change rate data table 19h is used for 
storing rates of change in target engine rotational speed N for values of 
the speed V of the vehicle in advance. 
A graph representing the contents of the target engine rotational speed 
change rate data table 19h is shown in FIG. 10. 
As shown in FIG. 10, data is set in the target engine rotational speed 
change rate data table 19h so that the rate of change in target engine 
rotational speed N is high for low values of the speed V of the vehicle. 
As the speed V of the vehicle is increased, however, the rate of change in 
target engine rotational speed N decreases. 
Receiving a value of the speed V of the vehicle monitored by the 
vehicle-speed detecting means 16, the target engine rotational speed 
processing means 19g searches the target engine rotational speed change 
rate data table 19h for a target engine rotational speed change rate for 
the speed V of the vehicle. The target engine rotational speed change rate 
is then multiplied by a change in vehicle speed .DELTA.V received from the 
vehicle speed change detecting means 17 to give a target change .DELTA.N 
in engine rotational speed N. 
A graph representing a relation between changes in vehicle speed .DELTA.V 
and changes in target engine rotational speed .DELTA.N is shown in FIG. 
11. 
FIG. 11 shows a relation for a rate of change in target engine rotational 
speed of 100 rotations per 1 kilometer/hour. For a change in vehicle speed 
.DELTA.V of +10 kilometer/hour, for example, the change in target engine 
rotational speed .DELTA.N is an increase of 1,000 rotations. For a change 
in vehicle speed .DELTA.V of -10 kilometer/hour, on the other hand, the 
change in target engine rotational speed .DELTA.N is a decrease of 1,000 
rotations. Then, the target engine rotational speed processing means 19g 
adds the change in target engine rotational speed .DELTA.N to or subtracts 
the change in target engine rotational speed .DELTA.N from a target engine 
rotational speed NE found previously to give a new target engine 
rotational speed NE. If the new target engine rotational speed NE is 
within a range between the upper-limit value NU and the lower-limit value 
NL, the new target engine rotational speed NE is then output as it is. If 
the new target engine rotational speed NE is greater than the upper-limit 
value NU, however, the upper-limit value NU is then output as a new target 
engine rotational speed NE. If the new target engine rotational speed NE 
is smaller than the lower limit value NL, on the other hand, the lower 
limit value NL is then output as a new target engine rotational speed NE. 
It should be noted that the target engine rotational speed processing 
means 19g is designed so that processing is carried out with the target 
engine rotational speed lower limit value NL for a vehicle speed of zero 
used as an initial value of the target engine rotational speed NE. 
The change-gear ratio controlling means 20 shown in FIG. 1 compares the 
target engine rotational speed NE output by the target engine rotational 
speed setting means 19 to the actual rotational speed N of the engine 
detected by the engine rotational speed detecting means 15, issuing a 
speed-change command 5a to make the actual rotational speed N of the 
engine equal to the target engine rotational speed NE. In this way, the 
change-gear ratio controlling means 20 carries out feedback control of the 
change-gear ratio R. When the change-gear ratio R goes beyond a range 
between a minimum change-gear ratio (Low) and a maximum change-gear ratio 
(Top) of the nonstage transmission 3, the change-gear ratio controlling 
means 20 discontinues the feedback control, outputting a speed-change 
command 5a for setting the change-gear ratio R to the minimum change-gear 
ratio (Low) or the maximum change-gear ratio (Top) instead. 
The change-gear ratio R is checked against the range between the minimum 
change-gear ratio (Low) or the maximum change-gear ratio (Top) because 
data tables for storing upper and lower limits of the target rotational 
speed of the engine shown in FIGS. 6 and 7, respectively, are created 
including limit values corresponding to the change-gear ratios R beyond 
the range which are shown in the Figures as characteristics represented by 
dotted lines. The limit values corresponding to the change-gear ratios R 
beyond the range are included in the data tables in order to simplify the 
process of creating the tables. If data tables for storing upper and lower 
limits of the target rotational speed of the engine are created within the 
range between the minimum change-gear ratio (Low) or the maximum 
change-gear ratio (Top) from the beginning, it will become unnecessary for 
the change-gear ratio controlling means 20 to check the change-gear ratio 
R against the range and for the change-gear ratio detecting means 13 to 
supply the change-gear ratio monitored thereby to the change-gear ratio 
controlling means 20. 
A block diagram of the configuration of a microcomputer system serving as a 
transmission control unit 50 is shown in FIG. 12. 
As shown in FIG. 12, the microcomputer system which serves as the 
transmission control unit 50 comprises a CPU 51, a ROM unit 52, a RAM unit 
53, an A/D converter 54 and a free-run timer 55. 
The ROM unit 52 is used for storing a transmission-control program written 
in advance as well as the fuzzy rules shown in FIG. 3, the membership 
functions shown in FIG. 4, the target engine rotational speed upper limit 
data table shown in FIG. 6, the target engine rotational speed lower limit 
data table shown in FIG. 7 and the target engine rotational speed change 
rate data table shown in FIG. 10. 
The detection signal 21a, a train of pulses output by the vehicle-speed 
sensor 21, and the detection signal 11a, a train of pulses output by the 
engine rotational speed sensor 11, are supplied to the CPU 51 as 
interrupts. In response to the interrupts, the CPU 51 carries out 
interrupt processing. In this way, the speed of the vehicle and the 
rotational speed of the engine that requires prompt processing can be 
detected. 
The voltage signal 10a from the stroke sensor 10 representing the 
change-gear ratio R and the voltage signal 12a from the throttle-opening 
sensor 12 representing the throttle opening .THETA. are each converted by 
the A/D converter 54 into a digital signal which is supplied to the CPU 
51. Strictly speaking, the CPU 51 activates the A/D converter 54 when the 
CPU 51 requires the values of the change-gear ratio R and the throttle 
opening .THETA. and then reads in the digital data therefrom. 
A flowchart showing principal processing carried out by the transmission 
control unit 50 is shown in FIG. 13. 
When power is supplied to the transmission control unit 50, the CPU 51 
receives an initialization signal which is typically generated by the 
operation of a power-on initialization circuit not shown in any of the 
Figures. Receiving the initialization signal at a step S1, the CPU 51 
initializes a variety of kinds of data stored in the RAM unit 53. At the 
same time, the CPU 51 is put in an interrupt-enabled state. 
Interrupted by the detection signals 11a and 21a, trains of pulses 
generated by the engine rotational speed sensor 11 and the vehicle-speed 
sensor 21 as described earlier, at a step S2, the CPU 51 carries out 
interrupt processing to compute the rotational speed N of the engine, the 
speed V of the vehicle and the change in vehicle speed per unit time (or 
the acceleration) G and, at the same time, processing to input the 
throttle opening .THETA. and the change-gear ratio R through the A/D 
converter 54. The data acquiring processing carried out at step S2 is 
repeated until a plurality of sets of data are collected. The sets of data 
each comprise the speed V of the vehicle, the change in vehicle speed per 
unit time (or the acceleration) G, the throttle opening .THETA. and the 
change-gear ratio R. Typically, ten sets of such data are collected. 
At a step S3, it is verified as to whether or not the required sets of such 
data have been collected. If the required sets of data are found at the 
step S3 to have been collected, the flow continues to a step S4 to find 
average values of the sets of data: an average engine rotational speed Na, 
an average speed Va of the vehicle, an average change in vehicle speed (or 
an average acceleration) Ga, an average throttle opening ea and an average 
change-gear ratio Ra. 
It should be noted that the detection signal 12a output by the 
throttle-opening sensor 12 can be supplied to the A/D converter 54 through 
a time-constant circuit, typically a low-pass filter circuit, having a 
predetermined time constant. In such a case, instead of acquiring a 
plurality of pieces of throttle-opening data and computing an average 
value for them, the A/D converter is activated only when it is necessary 
to read throttle-opening data. This technique is also applicable to the 
processing to read in data of the change-gear ratio R. 
At a step S5, fuzzy-inference based processing of the rate of change 
.DELTA.A in accommodation coefficient A is performed. This fuzzy-inference 
based processing is a process to compute membership values of the input 
values (or the average-value data) acquired in the step S4 which are found 
for each of the fuzzy sets: the speed of the vehicle, the change-gear 
ratio, the throttle opening and the change in vehicle speed per unit time 
(or the acceleration) shown in FIGS. 4(a) to (d). The membership values 
are used in conjunction with the fuzzy rules shown in FIG. 3 and the 
consequent conditions (or the fuzzy sets of the rate of change .DELTA.A in 
accommodation coefficient A shown in FIG. 4(e) as described earlier) for 
determining a membership function of the rate of change .DELTA.A in 
accommodation coefficient A for each of the fuzzy rules. Then, from the 
membership functions of the rate of change .DELTA.A in accommodation 
coefficient A determined for the individual fuzzy rules, a synthetic rate 
of change .DELTA.A is inferred by means of the Min-Max method of elastic 
center. 
At a step S6, a most recent value of the accommodation coefficient A is 
found from the synthetic rate of change .DELTA.A inferred in the step S5. 
In this embodiment, the rate of change .DELTA.A in accommodation 
coefficient A is found as a rate of change expressed in terms of percents. 
The rate of change is thus found by measuring a period between points of 
time at which immediately previous and current values of the rate of 
change .DELTA.A in accommodation coefficient A are output. The period 
between the two points of time is multiplied by the current value of the 
rate of change .DELTA.A in the accommodation coefficient A to give a 
change in the accommodation coefficient A which is added to or subtracted 
from the value of the accommodation coefficient A computed previously to 
result in a most recent value of the accommodation coefficient A. It 
should be noted that the initial value of the accommodation coefficient A 
is set at 0% when negative values of the accommodation coefficient A found 
by calculation are rounded up to the minimum 0%. On the other hand, the 
values of the accommodation coefficient A found by calculation to be 
greater than 100% are rounded down to the maximum 100%. 
At a step S7, the change in vehicle speed .DELTA.V is found as a difference 
between the current average speed Va of the vehicle and the previous 
average speed Va of the vehicle. It should be noted that, initially, zero 
is used as the previous average speed Va of the vehicle. 
At a step S8, the target engine rotational speed change rate data table 
shown in FIG. 10 is searched for a value of the target engine rotational 
speed change rate for the average speed Va of the vehicle. The value of 
the target engine rotational speed change rate for the average speed Va of 
the vehicle is then multiplied by the change in vehicle speed .DELTA.V 
found at the step S7 to provide a change in target engine rotational speed 
.DELTA.N. Refer to FIG. 11. 
At a step S9, the change in target engine rotational speed .DELTA.N is 
added to or subtracted from a target engine rotational speed NE found 
previously to give a new target engine rotational speed NE. Even though an 
idle rotational speed can be typically used as an initial value of the 
target engine rotational speed NE, in the case of the embodiment, a target 
engine rotational-speed lower limit NL for a vehicle speed of zero and an 
accommodation coefficient A found in the step S6 is used as the initial 
value. 
At a step S10, a value the target engine rotational speed NE found in the 
step S9 is corrected so as not to go beyond a predetermined range. 
First of all, the average speed Va of the vehicle and the average throttle 
opening .THETA.a found at the step S4 as well as the accommodation 
coefficient A found at the step S6 are utilized for searching the target 
engine rotational speed upper limit data table shown in FIG. 6 for data to 
be used in the eight-point interpolation technique shown in FIG. 8 which 
provides an upper-limit value NU of the target engine rotational speed NE. 
Next, the average speed Va of the vehicle at the step S4 and the 
accommodation coefficient A found at the step S6 are utilized for 
searching the target engine rotational speed lower limit data table shown 
in FIG. 7 for data to be used in the four-point interpolation technique 
shown in FIG. 9 which provides a lower-limit value NL of the target engine 
rotational speed NE. If the new target engine rotational speed NE found at 
a step S9 is within a range between the upper limit value NU and the lower 
limit value NL, the new target engine rotational speed NE is considered to 
be valid. If the new target engine rotational speed NE is greater than the 
upper-limit value NU, however, the upper-limit value NU is then output as 
a new target engine rotational speed NE. If the new target engine 
rotational speed NE is smaller than the lower-limit value NL, on the other 
hand, the lower-limit value NL is then output as a new target engine 
rotational speed NE. 
At a step S11, the target engine rotational speed NE found at the step S10 
is compared to the average engine rotational speed Na found at the step 4 
and a transmission signal 5a is issued to eliminate the difference between 
the target engine rotational speed NE and the average engine rotational 
speed Na. It should be noted that, when the change-gear ratio R goes 
beyond a range between the minimum change-gear ratio (Low) and the maximum 
change-gear ratio (Top) of the nonstage transmission 3, a speed-change 
command 5a for providing the minimum change-gear ratio (Low) or the 
maximum change-gear ratio (Top) is issued instead. 
As an alternative, while the processing at the steps S4 to S11 are being 
carried out, interrupts can be disabled so that the processing to compute 
the rotational speed N of the engine, the speed V of the vehicle and the 
change in vehicle speed per unit time (or the acceleration) G are not 
performed. After transmission control based on a new accommodation 
coefficient A has been carried out, the interrupts are again enabled to 
acquire as many pieces of data as required. 
A flowchart showing operations in the processing to monitor the speed V of 
the vehicle is shown in FIG. 14. 
The vehicle-speed detection processing shown as the flowchart of FIG. 14 is 
invoked by suspending the main control processing shown in FIG. 13 each 
time the vehicle-speed sensor 21 outputs a pulse of the detection signal 
21a. 
A pulse of the detection signal 21a generated by the vehicle-speed sensor 
21 makes a request for an interrupt to detect the value of the speed V of 
the vehicle. The interrupt, in turn, invokes the vehicle-speed detection 
processing wherein time data contained in free-run timer 55 is read in at 
a step S21. 
It is necessary to measure a time gap between two consecutive pulses of the 
detection signal 21a in order to compute the speed V of the vehicle. Thus, 
when the first time data is read in at a step S21, the flow goes to a step 
S26 through a step S22 in which case the time data is merely stored for 
later processing. When the second or subsequent time data is read in, a 
difference between the time data just read in and that read in previously 
is computed at a step S23. The speed V of the vehicle is then computed by 
typically dividing a constant proportional to the diameter of the tire by 
the time gap or the difference between the two pieces of time data. The 
speed V of the vehicle is then stored in a vehicle-speed storage area in 
the RAM unit 53. Typically, ten such vehicle-speed storage areas are 
prepared. Values of the speed V of the vehicle each computed in a 
processing loop are stored one after another in the vehicle-speed storage 
areas in a predetermined order. 
Two consecutive values of the speed V of the vehicle and the computed time 
gap between the two vehicle speeds are required for calculating the change 
in vehicle speed per unit time (or the acceleration) G. When two or more 
pieces of vehicle-speed data are found to exist at the step S24, the flow 
continues to a step S25 to calculate the change in vehicle speed per unit 
time (or the acceleration) G. The change in vehicle speed per unit time 
(or the acceleration) G is computed by dividing a difference between the 
current vehicle speed and the immediately previous vehicle speed stored in 
a vehicle-speed area in the RAM unit 53 by a difference between the 
current measurement time and the immediately previous measurement time. 
The change in vehicle speed per unit time (or the acceleration) G computed 
in this way is stored in an acceleration storage area in the RAM unit 53. 
Typically, there are ten such acceleration storage areas in the RAM unit 
53. At the step S25, values of the acceleration G each computed in a 
processing loop are stored one after another in the acceleration storage 
areas in a predetermined order. 
A flowchart showing operations in the processing to monitor the rotational 
speed N of the engine is shown in FIG. 15. 
Each time a pulse of the detection signal 11a generated by the 
engine-rotational-speed sensor 11 is input, interrupt processing for 
detecting the rotational speed N of the engine is invoked. 
When a pulse of the detection signal 11a is input, the contents of the 
free-run timer 55 are read in at a step S31, a step at the beginning of 
the interrupt processing. 
It is necessary to measure the time gap between two consecutive pulses of 
the detection signal 11a in order to compute the rotational speed N of the 
engine. Thus, when the first time data is read in at a step S31, the flow 
goes to a step S34 through a step S32 in which case the time data is 
merely stored for later processing. When the second or subsequent time 
data is read in, a difference between the time data just read in and that 
read in previously is computed at a step S33. The rotational speed N of 
the engine is then computed by typically dividing a constant by the time 
gap or the difference between the two pieces of time data. The rotational 
speed N of the engine is then stored in a storage area for the rotational 
speed N of the engine in the RAM unit 53. Typically, ten such storage 
areas are prepared. Values of the speed V of the vehicle each computed in 
a processing loop are stored one after another in the storage areas in a 
predetermined order at the step S33. 
By subsequently repeating the processing at the steps S2 to S11 shown in 
FIG. 13, the accommodation coefficient A indicating the running state is 
updated for each of the processing to keep up with changes in running 
conditions such as the speed V of the vehicle, the change in vehicle speed 
per unit time (or the acceleration) G and the throttle opening .THETA.. 
The change-gear ratio R of the nonstage transmission 3 is controlled in 
such a way that the value of the target engine rotational speed falls 
within a range set on the basis of the most recent accommodation 
coefficient A. Accordingly, a value of the rotational speed NE of the 
engine adapted to the running state can be obtained. As a result, the 
driver is provided with a driving feeling that faithfully keeps up with 
various running states of the vehicle and running requirements of the 
driver. 
This embodiment has a configuration comprising the steps of: 
calculating the accommodation coefficient after finding the rate of change 
in accommodation coefficient by fuzzy inference; 
setting upper and lower limits of a range for the target engine rotational 
speed on the basis of the accommodation coefficient calculated at the 
above step; and 
controlling the change-gear ratio R of the nonstage transmission so as to 
provide an actual rotational speed of the engine in the range. 
It should be noted, however, that the accommodation coefficient A can also 
be inferred directly from input data related to running states such as the 
speed V of the vehicle, the change in vehicle speed per unit time (or the 
acceleration) G, the throttle opening .THETA. and the change-gear ratio R 
by fuzzy inference. 
By the same token, an embodiment can also be configured wherein: 
a target engine rotational-speed data table is provided for directly 
specifying the target engine rotational speed NE from input data 
comprising the speed V of the vehicle, the throttle opening .THETA. and 
the accommodation coefficient A; 
the target engine rotational speed NE is directly set on the basis of a 
value of the accommodation coefficient A found by fuzzy inference; and 
the change-gear ratio R of the nonstage transmission is controlled to 
result in the target engine rotational speed NE directly set as described 
above. 
As described above, the transmission control apparatus for a nonstage 
transmission of a vehicle provided by the present invention executes the 
steps of: 
finding an accommodation coefficient indicating the running state of the 
vehicle from inputs comprising demanded engine-output quantities such as 
the throttle opening, the speed of the vehicle, the change-gear ratio and 
the rate of change in vehicle speed or the acceleration on the basis of 
fuzzy rules set in advance; and 
setting a target rotational speed of the engine or a range of 
rotational-speed values of the engine in accordance with the speed of the 
vehicle and the accommodation coefficient found at the previous step. 
Accordingly, values of the accommodation coefficient faithfully keeping up 
with the various running states of the vehicle and the running 
requirements of the driver can be obtained and transmission control can 
then be executed to result in target rotational speeds of the engine set 
on the basis of these accommodation coefficient values. As a result, the 
driver is provided with a driving feeling which faithfully keeps up with 
various running states of the vehicle and running requirements of the 
driver. 
It should be noted that a rate of change in accommodation coefficient is 
found by fuzzy inference and the rate of change is used for increasing or 
decreasing the accommodation coefficient. Accordingly, an abrupt change in 
accommodation coefficient can be eliminated. As a result, a vehicle that 
is easy to drive can be provided. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications as 
would be obvious to one skilled in the art are intended to be included 
within the scope of the following claims.