Drive-by-wire vehicle engine output control system

Described herein is a drive-by-wire vehicle engine output control system. The system permits good-response acceleration by a driver's simple and reasonable operation, i.e., by operating an accelerator pedal and also a prompt response even when a sudden load change occurs. Further, the system permits precise speed control by simple equipment even when the deviation of a vehicle speed from a target vehicle speed is large. Output changes of an engine can be controlled within a permissible output change range by (a) comparing a target autocruise engine output with an acceleration demanding ending output, choosing the larger engine output and then controlling the engine to give the larger engine output, (b) controlling the engine to achieve a target autocruise engine output obtained from a speed correction torque and a running load torque or (c) limiting an engine control quantity on the basis of a permissible output change value.

BACKGROUND OF THE INVENTION 
1) Field of Invention 
This invention relates to a drive-by-wire (DBW) vehicle engine output 
control system for setting the quantity of control of an engine in 
accordance with the degree of depression of an accelerator pedal by a 
driver and the mode of operation of a vehicle to electrically control the 
output of the engine on the basis of the control quantity or for 
controlling the output of the engine without relying upon operation of the 
accelerator pedal. 
2) Description of the Related Art 
Constant-speed control systems for making an automotive vehicle run at a 
constant speed (autocruise systems) have been provided to date. In those 
installed in automotive vehicles with a throttle valve mechanically 
connected to an accelerator pedal as an acceleration operating member, 
treadling of the accelerator pedal by a driver during autocruising is 
judged as the driver's need for more acceleration than the current level. 
In such a case, the driver can directly operate the throttle valve at 
opening rates greater than the maximum valve drive quantity by a cruise 
actuator in autocruising. 
The DBW system in which no mechanical connection is provided between an 
accelerator pedal and a throttle valve is, however, accompanied by the 
inconvenience that acceleration by the accelerator pedal is not feasible 
unless a brake pedal is treadled to cancel the autocruise mode. 
Such a system therefore requires the preposterous operation that, because 
the throttle valve returns to a fully-closed position by the cancellation 
of the autocruising and is then driven to open the same, the response 
becomes slower and the brake pedal has to be treadled once for 
acceleration. 
Further, the speed control system in a conventional constant-speed control 
system for making an automotive vehicle to run at a constant speed 
(autocruise system) is constructed, for example, in the following way. 
To obtain an intake air volume corresponding to a target vehicle speed, the 
position of a throttle valve (the position of a control rod of a governor 
in the case of a diesel engine) is adjustable. Owing to this adjustment, a 
vehicle speed achieved or realized on the side of an engine-body system is 
fed back to calculate the deviation .DELTA.V of the actual speed from the 
target vehicle speed. Feedback control corresponding to the deviation 
.DELTA.V is then applied to the position of the throttle valve, whereby 
the target vehicle speed can be realized. 
In an automotive vehicle equipped with such a conventional constant-speed 
control system, a relatively long time is, however, required to return to 
a target vehicle speed if a substantial deviation from the target vehicle 
speed takes place upon occurrence of a sudden change in load on a slope or 
the like. 
Where the deviation .DELTA.V from the target vehicle speed is large in the 
automotive vehicle equipped with the conventional speed control system, 
the opening rate of the throttle valve is significantly adjusted (in the 
case of a diesel engine, the position of the control rod of the governor 
is substantially adjusted) in order to correct or eliminate the deviation 
.DELTA.V. This may result in the potential problem that the drive torque 
of the engine would suddenly change to induce a certain acceleration or 
deceleration shock and the riding comfort would be deteriorated. 
To overcome this problem, it may be contemplated of lowering the open/close 
speed of the throttle valve upon control and hence limiting the change in 
the drive torque. There is, however, no linear relation between changes in 
the opening rate of the throttle valve and corresponding changes in the 
torque of a drive axle. If the open/close speed of the throttle valve is 
limited under conditions that the torque of the drive axle undergoes the 
largest change relative to the change in the opening rate of the throttle 
valve, the response of the speed control becomes slower under other 
driving conditions so that precise speed control cannot be performed. 
It is, therefore, necessary to vary the quantity of control of the 
open/close speed of the throttle valve in accordance with complex 
conditions. This, however, results in the need for a complex speed control 
system. 
SUMMARY OF THE INVENTION 
The present invention has been completed in view of such problems or 
inconvenience as described above. A first object of this invention is to 
permit good-response acceleration by a simple and reasonable operation, 
i.e., by controlling an accelerator pedal operating member where there is 
no mechanical connection between the accelerator pedal operating member 
and the throttle valve. 
A second object of this invention is to permit a prompt response by 
compensation of a running load even when a sudden load change has 
occurred. 
A third object of this invention is to permit precise speed control by a 
simple system, i.e., by limiting output torque changes even when a vehicle 
speed is substantially deviated from a target vehicle speed. 
To achieve the first object, the present invention provides a drive-by-wire 
vehicle engine output control system for setting the quantity of control 
of an engine in accordance with the degree of depression of an accelerator 
pedal by a driver and the mode of operation of a vehicle to electrically 
control the output of the engine on the basis of the control quantity or 
controlling the output of the engine without relying upon operation of the 
accelerator pedal, comprising: 
a vehicle speed detection means for detecting a running speed of the 
vehicle; 
a target engine output setting means for setting, based on the running 
speed detected by said vehicle speed detection means, a target autocruise 
engine output as a target output value to be outputted from the engine to 
execute autocruising in which the running speed of the vehicle is 
maintained at a predetermined value; 
an acceleration demand detection means for setting an acceleration 
demanding engine output as a target output value to be outputted from the 
engine in order to accelerate the vehicle in accordance with the degree of 
operation of the accelerator pedal; 
a selector means for comparing the target autocruise engine output set by 
said target engine output setting means with the acceleration demanding 
engine output set by said acceleration demand detection means and, when 
one of the engine outputs is greater than the other, selecting said 
greater engine output as a target engine output; and 
a target engine output realizing means for setting the engine control 
quantity at a level required to actually obtain an engine output equal to 
the target engine output selected by said selector means. 
Preferably, the selector means compares the target autocruise engine output 
set by said target engine output setting means with the acceleration 
demanding engine output set by said acceleration demand detection means 
and, when one of the engine outputs is greater than the other by a 
deviation of at least a predetermined value, selecting said greater engine 
output as a target engine output. 
The system may further comprises an output detection means for detecting an 
actual output of the engine in the course of the execution of the 
autocruising, wherein said selector means compares, instead of the target 
autocruise engine output, the actual engine output detected by said output 
detection means with the acceleration demanding engine output while the 
target autocruise engine output is selected as the target engine output. 
The acceleration demanding means preferably sets the acceleration demanding 
engine output on the basis of the running speed of the vehicle detected by 
said vehicle speed detection means and the degree of operation of the 
accelerator pedal. 
The target engine output setting means may preferably comprises a target 
vehicle speed setting means for setting a target vehicle speed upon the 
autocruising, a speed correction torque setting means for determining the 
deviation of the running speed of the vehicle detected by said vehicle 
speed detection means from the target vehicle speed set by the target 
vehicle speed setting means and, based on the deviation, setting a speed 
correction torque as a correction quantity for a torque of a drive axle of 
the vehicle, said correction quantity being required to eliminate the 
deviation, a drive axle torque detection means for detecting an actual 
drive torque of the drive axle, a running load torque detection means for 
detecting, based on the drive axle torque detected by said drive axle 
torque detection means, a running load torque corresponding to a running 
load during running of the vehicle, and a target engine setting means for 
setting the target autocruise engine output on the basis of the speed 
correction torque set by said speed correction torque setting means and 
the running load torque detected by said running load torque detection 
means. 
Preferably, the running load torque detection means further comprises an 
acceleration torque detection means for detecting an acceleration torque 
applied upon actual acceleration of the vehicle, whereby the running load 
torque is detected based on the drive axle torque detected by said drive 
axle torque detection means and the acceleration torque detected by said 
acceleration torque detection means. The running load torque detection 
means may detects the running load torque by subtracting the acceleration 
torque detected by said acceleration torque detection means from the drive 
axle torque detected by said drive axle torque detection means. Desirably, 
the acceleration torque detection means comprises an acceleration 
detection means for detecting a running acceleration of the vehicle, and 
an acceleration torque computing unit for computing the acceleration 
torque on the basis of the running acceleration detected by the 
acceleration detection means. 
The target autocruise output calculation means may preferably sum the speed 
correction torque set by said speed correction torque setting means and 
the running load torque detected by said running load torque detection 
means, converts the resulting sum to the target autocruise engine output 
and then outputs the target autocruise engine output. 
The speed correction torque setting means can comprise a PI control unit 
for determining the deviation of the running speed of the vehicle detected 
by said vehicle speed detection means from the target vehicle speed set by 
said vehicle speed setting means and setting a speed correction torque as 
a torque correction quantity for the drive axle of the vehicle, said 
torque correction quantity being required to eliminate the deviation, and 
a speed correction torque limiter for limiting, within a predetermined 
range, the speed correction torque set by said PI control unit. 
The system may further comprises a permissible torque change setting means 
for setting a permissible output change value for the engine, and a 
control quantity limiting means for limiting, on the basis of the 
permissible output change value set by the permissible torque change 
setting means, the engine control quantity set by the target engine output 
realizing means whereby changes in output of the engine are maintained not 
greater than the permissible output change value. Preferably, the 
permissible torque change setting means converts the preset permissible 
value of a torque change at the drive axle of the vehicle to the 
permissible output change value on the basis of a current gear shift 
position of a transmission. The target engine output realizing means 
converts the target engine output, which has been selected by said 
selector means, to a target air volume--which is the volume of intake air 
per revolution of the engine required to actually obtain an engine output 
equal to the target engine output selected by said selector means--and 
then outputs the target air volume as the engine control quantity. 
The system may further comprises a converter means for converting the 
permissible output change value, which has been set by said permissible 
torque change setting means, to a permissible air fuel volume change per 
revolution of the engine, whereby said control quantity limiting means 
controls the target air volume, which has been set by the target engine 
output realizing means, on the basis of the permissible air volume change 
obtained as a result of conversion by the converter means. The control 
quantity limiting means may comprises an intake air volume detection means 
for detecting the volume of intake air actually taken in the engine per 
revolution of the engine, and an air volume change limiter for limiting 
the deviation of the actual intake air volume detected by said intake air 
volume detection means from the target air volume set by the target engine 
output realizing means to a level not greater than the permissible air 
volume change obtained as a result of conversion by the converter means 
and then outputting the thus-limited deviation as a target air change 
quantity, whereby the engine control quantity required to make a change of 
the actual intake air volume per revolution of the engine equal to the 
target air change value is set based on the target air change value 
outputted from said air volume change limiter. The control quantity 
limiting means can output, as the engine control quantity, a final target 
air volume obtained by summing the target air change value outputted from 
said air volume change limiter and the actual intake air volume detected 
by said intake air volume detection means. 
Preferably, the system can control the output of the engine via a throttle 
valve of the engine and said target output realizing means sets, as the 
engine control quantity, a target opening rate of the throttle valve 
required to actually obtain an engine output equal to the target engine 
output selected by said selector means. The system may further comprises a 
converter means for converting the permissible output change value, which 
has been set by said permissible torque change setting means, to a 
permissible air volume change per revolution of the engine, wherein said 
control quantity limiting means comprises a throttle opening rate-air 
volume conversion unit for converting the target opening rate, which has 
been set by said target engine output realizing means, to a target air 
volume which is an intake air volume per revolution of the engine, an air 
volume change limiter for limiting the target air volume, which has been 
obtained as a result of conversion by said throttle opening rate-air 
volume conversion unit, on the basis of the permissible air volume change 
obtained as a result of conversion by said converter means, and an air 
volume-throttle opening rate conversion unit for setting, as a final 
target opening rate, an opening rate of the throttle valve required to 
make the actual intake air volume per revolution of engine equal to the 
target air volume limited by said air volume change limiter. 
The control quantity limiting means may further comprise an intake air 
volume detection means for detecting the volume of intake air actually 
taken in the engine per revolution of the engine, the air volume change 
limiter limits the deviation of the actual intake air volume detected by 
said intake air volume detection means from the target air volume obtained 
as a result of conversion by said throttle opening rate-air volume 
conversion unit to a value not greater than the permissible air volume 
change obtained as a result of conversion by said converter means, and 
said air volume-throttle opening rate conversion unit determines a final 
target air volume by summing the target air change value outputted from 
said air volume change limiter and the actual intake air volume detected 
by said intake air volume detection means, thereby setting, based on the 
final target air volume, the final opening rate of the throttle valve 
required to make the volume of intake air taken in the engine per 
revolution of the engine equal to the final target air volume. 
The system may further comprises a converter means for converting the 
permissible output change value, which has been set by said permissible 
torque change setting means, to a permissible air volume change per 
revolution of the engine, wherein said control quantity limiting means 
limits the target opening rate, which has been set by said target engine 
output realizing means, on the basis of the permissible fuel volume change 
obtained as a result of conversion by said converter means, whereby any 
change in the output of the engine is controlled equal to or smaller than 
the permissible output change value. 
To attain the second object, this invention also provides a drive-by-wire 
vehicle engine output control system for setting the quantity of control 
of an engine in accordance with the degree of depression of an accelerator 
pedal by a driver and the mode of operation of a vehicle to electrically 
control the output of the engine on the basis of the control quantity or 
for controlling the output of the engine without relying upon operation of 
the accelerator pedal, comprising: 
a vehicle speed detection means for detecting a running speed of the 
vehicle; 
a target vehicle speed setting means for setting a target vehicle speed 
upon autocruising in which the running speed of the vehicle is maintained 
constant; 
a speed correction torque setting means for determining the deviation of 
the running speed of the vehicle detected by said vehicle speed detection 
means from the target vehicle speed set by the target vehicle speed 
setting means and, based on the deviation, setting a speed correction 
torque as a correction quantity for a torque of a drive axle of the 
vehicle, said correction quantity being required to eliminate the 
deviation; 
a drive axle torque detection means for detecting an actual drive torque of 
the drive axle; 
a running load torque detection means for detecting, based on the drive 
axle torque detected by said drive axle torque detection means, a running 
load torque corresponding to a running load during running of the vehicle; 
a target autocruise output calculation means for setting the target 
autocruise engine output on the basis of the speed correction torque set 
by said speed correction torque setting means and the running load torque 
detected by said running load torque detection means; and 
a target engine output realizing means for setting the engine control 
quantity at a level required to actually obtain an engine output equal to 
the target autocruise engine output set by said target engine output 
setting means. 
The running load torque detection means may further comprise an 
acceleration torque detection means for detecting an acceleration torque 
applied upon actual acceleration of the vehicle, whereby the running load 
torque is detected based on the drive axle torque detected by said drive 
axle torque detection means and the acceleration torque detected by said 
acceleration torque detection means. Preferably, the running load torque 
detection means detects the running load torque by subtracting the 
acceleration torque detected by said acceleration torque detection means 
from the drive axle torque detected by said drive axle torque detection 
means. The acceleration torque detection means desirably comprises an 
acceleration detection means for detecting a running acceleration of the 
vehicle, and an acceleration torque computing unit for computing the 
acceleration torque on the basis of the running acceleration detected by 
the acceleration detection means. The target autocruise output calculation 
means may preferably sum the speed correction torque set by said speed 
correction torque setting means and the running load torque detected by 
said running load torque detection means, converts the resulting sum to 
the target autocruise engine output and then outputs the target autocruise 
engine output. The speed correction torque setting means may comprise a PI 
control unit for determining the deviation of the running speed of the 
vehicle detected by said vehicle speed detection means from the target 
vehicle speed set by said vehicle speed setting means and setting a speed 
correction torque as a torque correction quantity for the drive axle of 
the vehicle, said torque correction quantity being required to eliminate 
the deviation, and a speed correction torque limiter for limiting, within 
a predetermined range, the speed correction torque set by said PI control 
unit. 
To fulfill the third object, this invention also provides a drive-by-wire 
vehicle engine output control system for setting the quantity of control 
of an engine in accordance with the degree of depression of an accelerator 
pedal by a driver and the mode of operation of a vehicle to electrically 
control the output of the engine on the basis of the control quantity or 
for controlling the output of the engine without relying upon operation of 
the accelerator pedal, comprising: 
a vehicle speed detection means for detecting a running speed of the 
vehicle; 
a target engine output setting means for setting, based on the running 
speed detected by said vehicle speed detection means, a target autocruise 
engine output as a target output value to be outputted from the engine to 
execute autocruising in which the running speed of the vehicle is 
maintained at a predetermined value; 
a target engine output realizing means for setting the engine control 
quantity at a level required to actually obtain an engine output equal to 
the target autocruise engine output set by said target engine output 
setting means; 
a permissible torque change setting means for setting a permissible output 
change value for the engine; and 
a control quantity limiting means for limiting, on the basis of the 
permissible output change value set by the permissible torque change 
setting means, the engine control quantity set by the target engine output 
realizing means whereby changes in output of the engine are maintained not 
greater than the permissible output change value. 
Preferably, the permissible torque change setting means converts the preset 
permissible value of a torque change at the drive axle of the vehicle to 
the permissible output change value on the basis of a current gear shift 
position of a transmission. 
The target engine output realizing means may preferably convert the target 
engine output, which has been selected by said selector means, to a target 
air volume--which is the volume of intake air per revolution of the engine 
required to actually obtain an engine output equal to the target 
autocruise engine output set by said target engine output setting means 
and then outputs the target air volume as the engine control quantity. The 
system may further comprises a converter means for converting the 
permissible output change value, which has been set by said permissible 
torque change setting means, to a permissible air volume change per 
revolution of the engine, whereby said control quantity limiting means 
controls the target air volume, which has been set by the target engine 
output realizing means, on the basis of the permissible air volume change 
obtained as a result of conversion by the converter means. Desirably, the 
control quantity limiting means comprises an intake air volume detection 
means for detecting the volume of intake air actually taken in the engine 
per revolution of the engine, and an air volume change limiter for 
limiting the deviation of the actual intake air volume detected by said 
intake air volume detection means from the target air volume set by the 
target engine output realizing means to a level not greater than the 
permissible air volume change obtained as a result of conversion by the 
converter means and then outputting the thus-limited deviation as a target 
air change quantity, whereby the engine control quantity required to make 
a change of the actual intake air volume per revolution of the engine 
equal to the target air change value is set based on the target air change 
value outputted from said air volume change limiter. The control quantity 
limiting means may preferably output, as the engine control quantity, a 
final target air volume obtained by summing the target air change value 
outputted from said air volume change limiter and the actual intake air 
volume detected by said intake air volume detection means. 
The system may preferably control the output of the engine via a throttle 
valve of the engine and said target output realizing means sets, as the 
engine control quantity, a target opening rate of the throttle valve 
required to actually obtain an engine output equal to the target 
autocruise engine output set by said engine output setting means. 
Desirably, the system further comprises a converter means for converting 
the permissible output change value, which has been set by said 
permissible torque change setting means, to a permissible air volume 
change per revolution of the engine, wherein said control quantity 
limiting means comprises a throttle opening rate-air volume conversion 
unit for converting the target opening rate, which has been set by said 
target engine output realizing means, to a target air volume which is an 
intake air volume per revolution of the engine, an air volume change 
limiter for limiting the target air volume, which has been obtained as a 
result of conversion by said throttle opening rate-air volume conversion 
unit, on the basis of the permissible air volume change obtained as a 
result of conversion by said converter means, and an air volume-throttle 
opening rate conversion unit for setting, as a final target opening rate, 
an opening rate of the throttle valve required to make the actual intake 
air volume per revolution of engine equal to the target air volume limited 
by said air volume change limiter. Preferably, the control quantity 
limiting means further comprises an intake air volume detection means for 
detecting the volume of intake air actually taken in the engine per 
revolution of the engine, the air volume change limiter limits the 
deviation of the actual intake air volume detected by said intake air 
volume detection means from the target air volume obtained as a result of 
conversion by said throttle opening rate-air volume conversion unit to a 
value not greater than the permissible air volume change obtained as a 
result of conversion by said Converter means, and said air volume-throttle 
opening rate conversion unit determines a final target air volume by 
summing the target air change value outputted from said air volume change 
limiter and the actual intake air volume detected by said intake air 
volume detection means, thereby setting, based on the final target air 
volume, the final opening rate of the throttle valve required to make the 
volume of intake air taken in the engine per revolution of the engine 
equal to the final target air volume. 
The fulfillment of the first object by the present invention has brought 
about the following advantages: 
(1) Acceleration can be promptly effected responsive to the driver's 
intention without interruption of autocruising by treadling of the brake 
pedal, so that the response is fast. 
(2) No shock is produced upon returning to autocruising because the output 
of the engine changes in a continuous fashion. 
(3) It is no longer necessary to cancel the autocruise mode. The operation 
is therefore simplified, thereby reducing the chance of erroneous or 
accidental operation. 
The attainment of the second object by this invention has brought about the 
following advantage: 
(4) Upon changing the speed of the vehicle, it is possible to estimate the 
running load resistance of the vehicle and hence to adjust the output of 
the engine on the basis of the running load resistance so estimated. This 
has improved the response to load variations, thereby making it possible 
to perform speed control resistant to disturbances such as slopes and the 
like. 
The achievement of the third object by this invention has brought about the 
following advantage: 
(5) To avoid acceleration shock, changes in the intake air volume or the 
fuel volume (each per revolution of the engine) which is in a linear 
relation with the output torque of the engine are limited directly. It is 
hence possible to readily and surely prevent acceleration shock.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An automotive vehicle in which the system according to this embodiment can 
be suitably incorporated is a drive-by-wire vehicle (DBW vehicle) in which 
the quantity of control of an engine is set in accordance with the degree 
of depression of an accelerator pedal by a driver and the mode of 
operation of the vehicle to electrically control the output of the engine 
on the basis of the control quantity and the output of the engine can also 
be controlled without relying upon operation of the accelerator pedal. 
Therefore, as shown in FIG. 2(a), a motor (DC motor or stepper motor) 7 is 
connected to a throttle valve 6 disposed in an intake passage 5 through 
which combustion air is introduced into an engine main body 4 from an air 
cleaner 1. The throttle valve 6 is therefore driven by the motor 7 from a 
fully-closed position to a fully-opened position. 
In this embodiment, there are actually two intake passages which 
communicate to two banks of a V6 engine, respectively. Each of the intake 
passages is provided with such a throttle valve which is opened and closed 
by such a motor. Unless it is necessary to describe these intake passages 
and throttle valves individually, they will be referred to simply as the 
intake passage 5, throttle valve 6 and motor 7. The throttle valve 6 is 
also provided with a throttle opening rate sensor 8. This throttle opening 
rate sensor 8 is constructed, for example, of a potentiometer and can 
output a signal of a voltage level corresponding to each opening rate of 
the throttle valve 6. 
As is understood from the foregoing, the throttle valve 6 is not connected 
via a cable to an accelerator pedal as an accelerator operating member but 
is connected to the motor 7 controlled by a below-described engine control 
computer (ECU) 14. The output of the engine can therefore be controlled 
without relying upon operation of the accelerator by the driver. 
A pump of a torque converter 9 is connected to an output shaft of the 
engine body 4. Connected to a turbine of the torque converter 9 via a 
shaft 10 is a transmission unit 11, to which a wheel 13 is connected by 
way of a drive axle 12. The torque converter 9, shaft 10 and transmission 
unit 11 are assembled as an automatic transmission 20. The transmission 
unit 11 may be constructed as a manual transmission. The air cleaner 1 is 
equipped with an air flow sensor 3 on a side downstream of a cleaner 
element 2. This air flow sensor 3 is connected to ECU 14 so that an intake 
air volume A detected by the air flow sensor 3 is transmitted to ECU 14. 
Designated at symbol 5a is a surge tank. 
As has been described above, an output of ECU 14 is inputted to the motor 7 
so that the motor 7 is controlled. Namely, the output of ECU 14 is 
transmitted as a control quantity to a motor derive unit. The motor drive 
unit then outputs a predetermined operation quantity to the motor 7, 
whereby the throttle valve 6 is opened or closed to an extent as needed. 
ECU 14 is provided with such control units (see numerals 151-168 
(155-skipped) and the like as illustrated in FIG. 2(b). Pursuant to 
driver's mode setting and priority setting and automated systematic 
selection, these control units 151-168 and the like are selectively 
actuated to perform combined control. 
Of these control units 151-168 and the like, the running-load-compensating 
speed control unit (hereinafter referred to as the "RL-compensating speed 
control unit) 151 is constructed as will be described next. 
As is depicted in FIG. 1(b) and FIG. 4, a target autocruise output means 
(hereinafter referred to as the "TAO means") 151C is connected to a target 
engine output realizing means (hereinafter referred to as the "TAO 
realizing means"), whereby a target autocruise output to be realized is 
calculated by the means 151C and then inputted to the realizing means 
151D. 
The TAO calculation means 151C is inputted with a speed correction torque 
and also with an output from a running load torque detection means 
(hereinafter referred to as the "RLT detection means") 151G, whereby the 
TAO means 151C sums the speed correction torque and a running load torque 
to calculate a target drive axle torque. 
The speed correction torque is obtained as an output from a target vehicle 
speed setting means (hereinafter referred to as the "TVS setting means" 
151A and a speed correction torque setting means (hereinafter referred to 
as "SCT setting means") 151B. The speed correction torque is calculated 
through a PI control unit 101 and an acceleration limiting unit (speed 
correction torque limiter) 102. 
Namely, a deviation .DELTA.V (=V-Va) of an actual vehicle speed Va from a 
target vehicle speed V outputted from the TVS setting means 151A is 
inputted to the PI control unit 101, where a speed correction torque is 
calculated in accordance with the following formula: 
EQU K.sub.p .multidot..DELTA.V+K.sub.I .intg..DELTA.V 
The value so calculated is then determined as the speed correction torque 
by way of the unit 102. 
At the unit 102, by using an output torque change limiting speed control 
unit (hereinafter referred to as the "OTC-limiting speed control unit") 
152 and the like, the correction torque is determined and outputted in a 
state limited in speed correction torque change quantity in order to avoid 
shock which may otherwise be produced by an abrupt speed correction. 
On the other hand, the running load torque is detected by the RLT detection 
means 151G. Using an output from a drive axle torque detection means 151E 
and a detection signal from an acceleration torque detection means 107, 
the RLT detection means 151G detects the running load torque. Described 
specifically, the running load torque is calculated by subtracting an 
acceleration torque from a drive axle torque which has been calculated 
using an engine revolution number Ne. 
In other words, the running load torque is a torque for maintaining the 
vehicle speed and is calculated as follows: 
EQU Running load torque=drive shaft torque-acceleration torque 
This running load torque is detected and outputted as a torque to be 
compensated. 
Incidentally, the drive axle torque can be determined in accordance with 
the following formula: 
EQU .tau..multidot.C.multidot.Ne.sup.2 .multidot..rho. 
where 
C: capacity coefficient of torque converter; 
.tau.: torque ratio; 
Ne: revolution number of engine; and 
.rho.: overall gear ratio of transmission. 
On the other hand, the acceleration torque can be determined by the 
following formula: 
EQU W.multidot.(dV/dt).multidot.r 
where 
W: total vehicle weight; 
r: tire diameter; and 
V: vehicle body speed. 
Namely, dV/dt is determined at a differentiating unit (acceleration 
detection means) S1 and W.multidot.(dV/dt).multidot.r is calculated at a 
computing unit (acceleration torque computing unit) S2 with a multiplying 
circuit included therein. W and r have been stored beforehand in the 
computing unit S2. 
The TVS setting means 151A is constructed as shown in the block diagram of 
FIG. 3. 
Namely, a set switch 41 and a resume switch 49 are provided. By turning 
these switches on or off, setting of a target vehicle speed is performed 
based on the current vehicle speed via a time managing logic 42, a hold 
circuit 44, an integrating unit 46, a resume memory 47, switches 43,48 and 
a vehicle speed limiter 45. 
In addition to the elements described above, an unillustrated cruise switch 
is also provided as a main switch for conducting speed control 
(autocruise). 
The specifications of these switches are as follows: 
(1) Functions of the setting switches 
i) Set switch 41: 
Setting of a target vehicle speed and reduction of the target vehicle 
speed. 
ii) Resume switch 49: 
Resume of autocruising and increase of the target vehicle speed. 
iii) Brake switch: 
Discontinuation of autocruising. 
iv) Inhibitor switch: 
Suspension of autocruising. 
(2) Conditions for the actuation of the respective functions: 
i) Setting of a target vehicle speed: 
The cruise switch should be in the ON position and the current vehicle 
speed is supposed be in a predetermined range. With both the brake switch 
and the inhibitor switched turned off, the set switch 41 is turned 
off.fwdarw.on.fwdarw.off. The ON period is supposed to fall within a 
prescribed range. Simultaneous pressing of the set switch and the resume 
switch should be taken invalid. 
ii) Increase of the preset vehicle speed: 
The vehicle speed should be increased at the rate of 1 km/hr every 0.5 
second when the resume switch 49 is maintained in the ON position for 0.5 
second or longer in the course of speed control. 
iii) Reduction of the preset vehicle speed: 
The vehicle speed should be decreased at the rate of 1 km/hr every 0.5 
second when the set switch 41 is maintained in the ON position for 0.5 
second or longer in the course of speed control. 
iv) Resume function: 
When the conditions for the initiation of autocruising are satisfied and 
the resume switch 49 is in the ON position, autocruising is performed 
using as a target speed the speed at the time of end of the preceding 
autocruise. Even when the ignition switch is turned on, this turning-on 
actuation is invalidated as long as it is before the initiation of 
autocruising. 
v) Discontinuation of autocruising: 
Autocruising is discontinued when either the brake switch or the inhibitor 
switch is turned on, or the cruise switch is turned off. 
vi) Suspension of autocruising: 
When a torque instructed by the accelerator pedal is greater than the 
current autocruise demanding torque, autocruising is suspended and the 
vehicle runs at the torque instructed by the accelerator pedal. When the 
torque instructed by the accelerator pedal becomes equal to or smaller 
than the current autocruise demanding torque (90% or smaller including a 
hysteresis) or the accelerator pedal position becomes equal to or higher 
than the idling level, autocruising is performed at the speed before the 
suspension. 
Owing to the construction described above, the RL-compensating speed 
control unit 151 performs such operation as will be described next. 
To actuate the speed control unit (autocruise), the driver turns on the 
autocruise switch and also turns off, on and then off the set switch 41 
shown in the block diagram of FIG. 3. If, at this time, the vehicle speed 
V is in the range higher than 10 km/hr but lower than 100 km/hr (10 
km/hr&lt;V&lt;100 km/hr), the brake switch and inhibitor switch are both in 0N 
state and the period, t seconds, of the ON state of the set switch 41 is 
in the range longer than 0.1 second but shorter than 0.5 second 
(0.1&lt;t&lt;0.5), autocruise control is initiated. Namely, as is shown in FIG. 
3, an interlocking switch 43 is maintained in ON state while the period of 
this ON state is being measured at the time control logic 42. The current 
vehicle speed held by the hold circuit 44 and this vehicle speed is 
inputted to the vehicle speed limiter 45. 
An output of the vehicle speed limiter 45 is then inputted as a target 
vehicle speed V to an engine output control system depicted in FIGS. 1(b) 
and 4. If the operator turns on the resume switch 49 subsequent to the 
initiation of autocruising (ASC) and has the ON state continued for 0.5 
second or longer, the vehicle speed stored in the resume memory 47 is 
inputted to the vehicle speed limiter 45 via the switch 48 and the hold 
circuit 44 and the speed increased at the rate of 1 km/hr upon every 
continuation of 0.5 second is inputted to the vehicle speed limiter 45 via 
the integrating circuit 46. As a result, the target speed is increased by 
1 km/hr upon every 0.5 second continuation of the resume switch 49 in ON 
state. At the vehicle speed limiter 45, for a preset vehicle speed not 
lower than a desired speed, a preset maximum speed V.sub.max is outputted 
as a target vehicle speed. For a preset vehicle speed lower than a desired 
speed, the preset slowest vehicle speed V.sub.min will be outputted as a 
target. 
To reduce the target vehicle speed, on the other hand, the set switch 41 is 
maintained in ON state for 0.5 second or longer. As a consequence, a 
reduced speed so set is inputted into the integrating circuit 46 via the 
switch 43. The so-set reduced speed as an output from the integrating 
circuit 46 is subtracted from the set vehicle speed as an output from the 
hold circuit 44, and the difference is inputted into the vehicle speed 
limiter 45. A target vehicle speed V reduced by 1 km/hr upon every 0.5 
second continuation of ON state of the set switch 41 is, therefore, 
outputted from the vehicle limiter 45. 
The actuation of this autocruising (ASC) is discontinued when the brake 
switch or inhibitor switch is turned on or the cruise switch is turned 
off. When the resume switch 49 is turned on, autocruising is resumed. At 
this time, the speed at the time of discontinuation of the preceding 
autocruising is read from the resume memory 47 and autocruising is 
performed using that speed as a target speed. Even when the resume switch 
49 is brought into ON state after an ignition switch has been turned on, 
autocruising is not performed if there is no history of actuation of 
autocruising before the resume switch 49 was turned on. 
On the other hand, at the engine output control unit which performs 
autocruising by controlling the output of the engine, as is illustrated in 
the block diagram of FIG. 4 and the flow charts of FIGS. 5(a) to 5(c), a 
target vehicle speed V is inputted from a target vehicle speed setting 
means (hereinafter referred to as the "TVS setting means") 151A. A 
deviation .DELTA.V (=V-Va) of an actually-measured vehicle speed Va, which 
has been detected by a vehicle speed detection means 151F, from the target 
vehicle speed V is calculated (step b1), followed by the input of the 
deviation .DELTA.V into the PI control unit 101. At the PI control unit 
101, a speed correction torque is calculated in accordance with the 
formula K.sub.p .multidot..DELTA.V+K.sub.I .multidot..intg..DELTA.V 
(K.sub.p,K.sub.I : constants) (step b2). The value so calculated is 
inputted into the acceleration limiting unit 102. 
To avoid shock by a speed correction, a preset maximum correction torque 
T.sub.max in the range that no shock will be produced is outputted from 
the acceleration limiting unit 102 against any speed correction unit of a 
level greater than that needed. On the other hand, a preset minimum 
correction torque T.sub.min is outputted for any speed correction torque 
of a level smaller than needed (step b3). Upon receipt of the vehicle 
speed V detected by the vehicle speed detection means 151F, the 
acceleration torque detection means 107 detects (or estimates) the 
acceleration of the vehicle by differentiation (step a1). The acceleration 
detection means S1 in the acceleration torque detection means 107 can be 
constructed of an acceleration sensor. 
At the acceleration torque detection means 107, the acceleration torque 
corresponding to the current acceleration quantity is calculated in 
accordance with W.multidot.(dV/dt).multidot.r (step a2). In this equation, 
W: total vehicle weight, V: vehicle body speed, and r: tire diameter. 
Next, upon receipt of the engine revolution number Ne detected by the 
engine revolution number sensor 17a, the drive axle torque of the engine 
is detected (or estimated) by the drive axle torque calculation means 151E 
(step a3). 
Namely, the drive axle torque can be calculated in accordance with the 
following formula: 
EQU C.multidot..tau..multidot.Ne.sup.2 .multidot..rho. 
where 
C: capacity coefficient of torque converter (which is given by a separate 
map); 
.tau.: torque ratio (which is given by a separate map; 
Ne: engine revolution number (rpm); and 
.rho.: overall gear ratio. 
Measured values of the above acceleration and drive axle torque are 
subjected to a primary filter to eliminate noise, whereby the acceleration 
and drive axle torque are determined while placing priority on stability 
rather than momentary accuracy. Further, any error which may arise during 
the calculation can be corrected by PID control. 
Subsequent to the above-described detection of the drive axle torque, the 
calculation of the running resistance torque (running load torque) is 
conducted in accordance with the following formula: 
EQU Running resistance torque=drive axle torque 
(C.multidot..tau..multidot.Ne.sup.2 .multidot..rho.)-acceleration torque 
{W.multidot.(dV/dt).multidot.r} (step a4). 
At the TAO means 151C, the running load torque and the speed correction 
torque, both described above, are then summed to determined a target drive 
axle torque. This target drive axle torque is inputted to the TEO 
realizing means 151D (step c1). 
At the TAO means 151C, the target drive axle torque is converted to an 
intake air volume A/N per revolution of the engine via an engine torque. 
In other words, an engine output torque corresponding to the axle torque 
is calculated in view of the gear ratio (including the torque ratio of the 
torque converter). An air volume required for the output torque is then 
determined based on a substantially linear function which indicates the 
their relationship. The air volume is converted to an angle of rotation of 
the throttle valve 6 and is inputted to the TEO realizing means 151D. 
Instead of obtaining the intake air volume from the engine output torque, a 
fuel volume may be obtained from the engine output torque. In this manner, 
the control can be applied not only to a gasoline engine but also to a 
diesel engine. Namely, it is necessary to determine an intake air volume 
or fuel volume in the case of a gasoline engine or a fuel volume in the 
case of a diesel engine and then control the intake air volume or the fuel 
volume. 
By doing so, the throttle valve 6 is rotated under control to a position by 
the motor drive unit so that the engine can output the target drive axle 
torque (step c2). 
The individual operations in the flow charts shown in FIGS. 5(a), 5(b) and 
5(c), respectively, are performed in parallel and, as the detection values 
for the respective steps, those at the time of the processings are used. 
By such operations as described above, when the vehicle has come to a slope 
or the like and a change has occurred in load, the throttle valve 6 is 
controlled to compensate the running load torque such that the change in 
load can be eliminated, whereby a sure and prompt measure can also be 
taken against such a change in load. 
A description will next be made of the OTC-limiting speed control unit 152. 
The unit 152 is constructed as shown in FIGS. 1(c), 2(a), 2(b) and 6. 
By a permissible torque change setting means (hereinafter referred to as 
the "PTC setting means") 152A, upper and lower limits for changes in drive 
torque are set so that the driver does not feel shock during speed 
control. These upper and lower limits are inputted in a converter means 
152B. The converter means 152B is equipped with a map indicative of 
correlation between torque changes and A/N (air volumes per engine 
revolution) as shown in FIG. 8(a) and outputs the upper and lower limits 
of torque changes after converting them to an upper limit .DELTA.A/Nu and 
a lower limit .DELTA.A/Nl for A/N. 
A throttle valve open/close limiting means (hereinafter referred to as the 
"TV open/close limiting means) 152C is also provided. This limiting means 
152C is inputted with a target throttle opening rate .theta.o from the TEO 
realizing means 153C, which will be described later, and outputs a final 
target throttle valve opening rate .theta.t. Namely, the limiting means 
152C is, as shown in FIG. 6, a throttle opening rate-air volume converter 
unit 152D to convert the target throttle opening rate .theta.o to a target 
air volume A/No. A map indicative of air volumes A/N corresponding to 
throttle opening rates .theta., such as that illustrated in FIG. 8(b), is 
stored against the engine revolution number Ne as a parameter in the 
conversion unit 152D. From the target throttle opening rate .theta.o so 
inputted and also from an engine revolution number signal inputted from 
the engine revolution number sensor 17a, the target air volume A/No is 
calculated and outputted. 
An A/N value of the engine, which has been measured during the last control 
and has been stored in a memory 152F, is subtracted from the output of the 
throttle opening rate-air volume converter unit 152D. The difference is 
then inputted as an air change .DELTA.A/No to a limiter 152G. At the 
limiter 152G, to calculate the final target A/N, the air change 
.DELTA.A/No is limited to .DELTA.A/Nt which falls within the range defined 
by the upper and lower limits .DELTA.A/Nu and .DELTA.A/Nl, and is then 
outputted. The TV open/close limiting means 152C is provided with an air 
volume-throttle opening rate converter unit 152E. The air change 
.DELTA.A/Nt outputted from the limiter 152G is added to the measured A/N 
value from the memory 152F in which the last operation state is stored, 
and the sum so obtained is inputted to the converter unit 152E. 
In the air volume-throttle opening rate converter unit 152E, a map 
indicative of throttle opening rates .theta. corresponding to A/N, such as 
that illustrated in FIG. 8(c), is stored against the engine revolution 
number Ne as a parameter, so that the target A/Nt can be outputted 
subsequent to its conversion to the final target opening rate .theta.t. 
Where the RL-compensating speed control unit 151 is provided, the final 
target opening rate .theta.t is converted to a speed correction torque and 
then inputted to the TAO means 151C. Without the control unit 151, the 
final target opening rate .theta.i is outputted directly to the drive 
motor 7 for the throttle valve 6. 
Owing to the construction described above, at the OTC-limiting speed 
control unit 152, control is performed following the flow chart of FIG. 7 
as will be described next. 
Namely, an upper limit .DELTA.Ttu and a lower limit .DELTA.Ttl for a change 
in drive axle torque during every control cycle so that an occupant does 
not feel shock during speed control are set in advance at the PTC setting 
means 152A (step 52A). 
At the PTC setting means 152A, the upper and lower limits 
.DELTA.Ttu,.DELTA.Ttl are divided by a current gear ratio .rho. of the 
vehicle, respectively, and are hence converted to upper and lower limits 
.DELTA.Teu,.DELTA.Tel to changes in engine torque (step 52B). Next, at the 
converter means 152B, the upper and lower limits .DELTA.Teu, .DELTA.Tel of 
the engine torque change are converted to air volume changes (per engine 
revolution) .DELTA.A/Nu,.DELTA.A/Nl in accordance with the map shown in 
FIG. 8(a) (step 52C). 
On the other hand, at the TV open/closure limiting means 152C, the target 
throttle opening rate .theta.o is converted to the target air volume A/No 
by the throttle opening rate-air volume converter unit 152D. Here, the 
conversion is conducted by the map corresponding to the characteristics 
shown in FIG. 8(b) so that the target air volume A/No is determined by the 
throttle opening rate .theta.o and the engine revolution number Ne (step 
52D). 
Further, the A/N at the time of the last control, which has been measured 
beforehand and is stored in the memory (intake air volume detection means) 
152F, is subtracted from the target air volume A/No. The target air volume 
A/No is therefore inputted in the form of the difference .DELTA.A/No in 
the air volume change limiter 152G (step 52E). 
When the difference .DELTA.A/No falls between the upper and lower limits 
.DELTA.A/Nu and .DELTA.A/Nl, the difference .DELTA.A/No is outputted, as 
it is, as .DELTA.A/Nt from the limiter 152G. When the difference 
.DELTA.A/No is greater than the upper limit .DELTA.A/Nu, .DELTA.A/Nu is 
outputted. When the difference .DELTA.A/No is smaller than the lower limit 
.DELTA.A/Nl, .DELTA.A/Nl is outputted as .DELTA.A/Nt (step 52F). 
.DELTA.A/Nt outputted from the limiter 152G is added to the last A/N 
stored in the memory 152F and is then inputted as the target air volume 
A/Nt to the air volume-throttle opening rate converter unit 152E (step 
52G). 
At the air volume-throttle opening rate converter unit 152E, the target air 
volume A/Nt is converted to the final target opening rate .theta.t in 
accordance with the map of the characteristics depicted in FIG. 8(c) and 
is then outputted (step 52H). The throttle valve 6 is therefore driven 
toward the target opening rate .theta.t by means of the motor 7 (step 
52I). 
Where the OTC-limiting speed control unit 152 is connected to the 
RL-compensating speed control unit 151, the target opening rate .theta.t 
is converted further to a speed correction torque and is then inputted to 
the TAO means 151C. Accordingly, the OTC-limiting speed control unit 152 
operates as the acceleration limiting unit 102. 
As has been described above, changes in the intake air volume or fuel 
volume (each per engine revolution) which is in a linear relationship with 
the engine output torque are directly limited to avoid acceleration shock, 
thereby making it possible to easily and surely prevent acceleration 
shock. 
The OTC-limiting speed control unit 152 can be designed to directly control 
the speed in accordance with the air volume without using the throttle 
opening rate as a target. In this case, the throttle opening rate-air 
volume converter unit 152D (.theta..fwdarw.A/N) and the air 
volume-throttle opening rate converter unit 152E (A/N.fwdarw..theta.) 
become unnecessary. 
Since the air volume is substantially proportional to the fuel volume in a 
gasoline engine, the speed can be controlled based on the fuel volume 
instead of A/N. In the case of a diesel engine, the speed is controlled 
base on the fuel volume. When the speed is controlled in accordance with 
the fuel volume as described above, the control can also be conducted in a 
similar manner to the control performed relying upon the air volume. 
An accelerator-pedal-combined speed control unit (hereinafter referred to 
as the "AP-combined speed control unit") 153 will next be described. This 
AP-combined speed control unit 153 is constructed as shown in FIGS. 1(a) 
and 11. The AP-combined speed control unit 153 is provided with an 
acceleration demand detection means (hereinafter referred to as the "AD 
detection means") 153A which detects an acceleration output demanded by 
the driver through a stroke of an accelerator pedal 15. This AD detection 
means 153A is equipped with a map of characteristics such as those shown 
in FIG. 13(a), so that relations among preset speeds, drive axle torques 
and accelerator pedal strokes are set there. 
Also provided is a target engine output setting means (hereinafter referred 
to as the "TEO setting means") 153D, which receiver as input information 
an engine output demand corresponding to a speed set by the driver for 
controlling autocruising (ASC), an intake air volume detected by the air 
flow sensor 3 and a revolution number detected by the engine revolution 
number sensor 17a. 
In addition, a controller (selector means) 153B is also provided. Inputted 
to the controller 153B are the output demand from the AD detection means 
153A, the output demand having been set by the accelerator pedal 15, and a 
target autocruising engine output from a target engine output setting 
means (hereinafter referred to as the "TEO setting means") 153D. 
The controller 153B has a switching function (selection function). Either 
the output demand set by the accelerator pedal 15 or the target 
autocruising engine output is selected by the switching function and is 
outputted as a target engine output torque. The target engine output 
torque is then inputted to the TEO realizing means 153C. The TEO realizing 
means 153C is equipped with the characteristics, which are shown in 
FIG.13(b), as a map, whereby the target throttle opening .theta. is 
determined from the engine revolution number Ne and the target output 
torque (engine torque) T and is then outputted. 
Owing to the above construction, the AP-combined speed control unit 153 
operates following the charts depicted in FIGS. 12(a), 12(b) and 12(c), 
respectively. 
It is judged by interlocked switches 153D.sub.2,153D.sub.3 in the TEO 
setting means 153D if autocruising (ASC) is under execution (step 53A). 
When autocruising is under execution with the switch 153D.sub.2 being 
maintained in ON state, the present output is computed by the output 
detection means 153D.sub.1 on the basis of an intake air volume from the 
air flow sensor 3 and a revolution number from the revolution number 
sensor 17a and is outputted from the TEO setting means 153D (step 53C). 
When the switch 153D.sub.2 is in OFF state and switch 153D.sub.3 is in ON 
state (i.e., during ASC holding; step 53B), the autocruising output demand 
is outputted from TEO setting means 153D (step 53D). 
An acceleration demand by the driver, said demand having been made by 
treadling the accelerator pedal 15, is detected by the AD detection means 
153A. Namely, the stroke of the accelerator pedal 15 is detected by an 
accelerator position sensor 15A (step 53E) and, by the map shown in FIG. 
13(a), a vehicle speed plotted along the axis of abscissas is converted to 
an output (drive axle torque) while using the stroke as a parameter (step 
53F). 
The thus-determined output (drive axle torque) corresponding to the stroke 
of the accelerator pedal is inputted to a selector means 153B. At a 
subtraction means 153B.sub.1, the output demand by the accelerator pedal 
is subtracted from the autocruising output demand so that the deviation 
.DELTA.P of the former from the latter is calculated (step 53G). At the 
selector means 153B, the deviation .DELTA.P is then inputted to a switcher 
153B.sub.2 so that a target output is determined through steps 53H, 53I, 
53K, 53L and 53N. 
Namely, if the deviation .DELTA.P is greater than a preset upper deviation 
limit .DELTA.Pu (.DELTA.Pu&gt;0), the output from the TEO setting means 153D, 
said output having been set to corresponding to autocruising, is adopted 
as the target output because the output from the TEO setting means 153D is 
greater by at least a predetermined value than the output demanded by the 
accelerator pedal 15 (steps 53H,53I). As a result, an autocruise hold flag 
for bringing the switch 153D.sub.3 into OFF state is reset (step 53J), and 
an autocruise execution flag for bringing the switch 152D.sub.2 to ON 
state is set (step 53P). 
If the deviation .DELTA.P is smaller than a preset lower deviation limit 
.DELTA.Pl(.DELTA.Pl&lt;0&lt;.DELTA.Pu), the output demanded by the accelerator 
pedal 15 is adopted as the target output because it is greater by at least 
a predetermined value than the output from the TEO setting means 153D, 
said output having been set to correspond to autocruising step 53L). As a 
result, the autocruise execution flag is reset by the switch 152D.sub.2 
(step 53M) and the autocruise hold flag is set by the switch 153D.sub.3 
(step 53Q). 
If the deviation .DELTA.P is a value between .DELTA.Pu and .DELTA.Pl, the 
target output at the time of the last control is adopted again because the 
output demanded by the accelerator pedal 15 is not greater by at least a 
predetermined value than the output corresponding to the autocruise or 
vice versa (step 53N). Accordingly, the autocruise hold flag is neither 
set nor reset so that control conducted like the last control. Namely, if 
the last control is autocruising, the target engine output for the 
autocruising is selected. If the last control is a demand for 
acceleration, the acceleration demanding engine output is selected. This 
can prevent control chattering. 
The target output determined by the selector means 153B is then inputted to 
the TEO realizing means 153C and, in accordance with the map shown in FIG. 
13(b), a target throttle opening rate .theta. is outputted (step 53O). 
Namely, the target throttle opening rate .theta. is determined by the 
engine output number Ne and the target output (engine torque) in FIG. 
13(b). 
When the accelerator pedal 15 is treadled substantially while maintaining 
the autocruising speed controlled state by such an operation as described 
above, acceleration corresponding to the stroke of the accelerator pedal 
15 is effected. When the stroke of the accelerator pedal 15 is reduced to 
or beyond a predetermined level, the vehicle returns to the autocruising 
state. 
Acceleration pursuant to the driver's intention is therefore achieved 
promptly without any interruption of autocruising by treadling of the 
brake pedal as described above. The response is therefore faster and, as 
the output of the engine changes in a continuous manner upon returning to 
the autocruise mode, no shock is produced upon returning to the autocruise 
mode. 
In addition, it is no longer necessary to cancel the autocruise mode. This 
has eliminated the cumbersome operation, thereby lowering the danger of 
induction of erroneous operations. 
The output from the AL-combined speed control unit 153 is selectively 
adopted depending on the degree of its preference relative to other 
outputs parallelly outputted from other control units and the setting of a 
drive mode by the driver, whereby the running of the vehicle is 
controlled. 
From the foregoing, it is understood that the RL-compensating speed control 
unit 151, the OTC-limiting speed control unit 152 and the AP-combined 
speed control unit 153 are constructed as described below. 
A description will first be made centering on the AP-combined speed control 
unit 153. In the drive-by-wire vehicle engine output control system for 
setting the quantity of control of an engine in accordance with the state 
of operation of the accelerator pedal 15 by the driver and the state of 
driving of the vehicle to electrically control the output of the engine on 
the basis of the control quantity or for controlling the output of the 
engine without relying upon operation of the accelerator pedal, the 
AP-combined speed control unit 153 comprises the vehicle speed detection 
means 151F for detecting a running speed of the vehicle; the TEO setting 
means 153D for setting, based on the running speed detected by the vehicle 
speed detection means 151F, a target autocruise engine output as the 
target output value to be outputted from the engine to execute 
autocruising in which the running speed of the vehicle is maintained at 
the predetermined value; the AD detection means 153A for setting an 
acceleration demanding engine output as the target output value to be 
outputted from the engine in order to accelerate the vehicle in accordance 
with the degree of operation of the accelerator pedal; the selector means 
153B for comparing the target autocruise engine output set by the TEO 
setting means 153D with the acceleration demanding engine output set by 
the AD detection means 153A and, when one of the engine outputs is greater 
than the other, selecting the greater engine output as the target engine 
output; and the TEO realizing means 153C for setting the engine control 
quantity at the level required to actually obtain an engine output equal 
to the target engine output selected by the selector means 153B. 
In the above construction, the selector means 153B compares the target 
autocruise engine output set by the TEO setting means 153D with the 
acceleration demanding engine output set by the AD detection means 153A 
and, when one of the engine outputs is greater than the other by a 
deviation of at least a predetermined value, selecting the greater engine 
output as the target engine output. The TEO setting means 153D further 
comprises the output detection means 153D.sub.1 for detecting an actual 
output of the engine in the course of the execution of the autocruising, 
and the selector means compares, instead of the target autocruise engine 
output, the actual engine output detected by the output detection means 
153D.sub.1 with the acceleration demanding engine output while the target 
autocruise engine output is selected as the target engine output. The AD 
detection means 153A sets the acceleration demanding engine output on the 
basis of the running speed of the vehicle detected by the vehicle speed 
detection means 151F and the degree of operation of the accelerator pedal. 
The TEO setting means 153D comprises the TVS setting means 151A for 
setting a target vehicle speed upon the autocruising; the SCT setting 
means 151B for determining the deviation of the running speed of the 
vehicle detected by the vehicle speed detection means 151F from the target 
vehicle speed set by the TVS setting means 151A and, based on the 
deviation, setting the speed correction torque as a correction quantity 
for the torque of the drive axle of the vehicle, said correction quantity 
being required to eliminate the deviation; the drive axle torque detection 
means 151E for detecting an actual drive torque of the drive axle; the RLT 
detection means 151G for detecting, based on the drive axle torque 
detected by the drive axle torque detection means 151E, a running load 
torque corresponding to a running load during running of the vehicle; and 
the TAO means 151C for setting the target autocruise engine output on the 
basis of the speed correction torque set by the SCT setting means 151B and 
the running load torque detected by the RLT detection means 151G. 
In addition, the RLT detection means 151G further comprises the 
acceleration torque detection means 107 for detecting an acceleration 
torque applied upon actual acceleration of the vehicle, whereby the 
running load torque is detected based on the drive axle torque detected by 
the drive axle torque detection means 151E and the acceleration torque 
detected by the acceleration torque detection means 107. The RLT detection 
means may be designed to detect the running load torque by subtracting the 
acceleration torque detected by the acceleration torque detection means 
107 from the drive axle torque detected by the drive axle torque detection 
means 151E. The acceleration torque detection means 107 comprises the 
acceleration detection means S1 for detecting a running acceleration of 
the vehicle; and the acceleration torque computing unit S2 for computing 
the acceleration torque on the basis of the running acceleration detected 
by the acceleration detection means S1. 
The TAO means 151C sums the speed correction torque set by the SCT setting 
means 151B and the running load torque detected by the RLT detection means 
151G, converts the resulting sum to the target autocruise engine output 
and then outputs the target autocruise engine output. The SCT setting 
means 151B comprises the PI control unit 101 for determining the deviation 
of the running speed of the vehicle detected by the vehicle speed 
detection means 151F from the target vehicle speed set by the TVS setting 
means 151A and setting a speed correction torque as the torque correction 
quantity for the drive axle of the vehicle, said torque correction 
quantity being required to eliminate the deviation; and the acceleration 
limiting unit 102 for limiting, within the predetermined range, the speed 
correction torque set by the PI control unit 101. 
The AP-combined speed control unit 153 further comprises the PTC setting 
means 152A for setting a permissible output change value for the engine; 
and the TV open/close limiting means 152 for limiting, on the basis of the 
permissible output change value set by the PTC setting means 152A, the 
engine control quantity set by the TEO realizing means 153C whereby 
changes in output of the engine are maintained not greater than the 
permissible output change value. The PTC setting means 152A converts the 
preset permissible value of the torque change at the drive axle of the 
vehicle to the permissible output change value on the basis of the current 
gear shift position of the transmission. 
The TEO realizing means 153C converts the target engine output, which has 
been selected by the TEO realizing means 153C, to a target air 
volume--which is the volume of intake air per revolution of the engine 
required to actually obtain an engine output equal to the target engine 
output selected by the selector means 153B--and then outputs the target 
air volume as the engine control quantity. The TEO realizing means 153C 
further comprises the converter means 152B for converting the permissible 
output change value, which has been set by the PTC setting means 152A, to 
the permissible air volume change per revolution of the engine, whereby 
the TV open/close limiting means 152C controls the target air volume, 
which has been set by the TEO realizing means 153C, on the basis of the 
permissible air volume change obtained as a result of conversion by the 
converter means 152B. 
The TV open/close limiting means 152C comprises the intake air volume 
detection means 152F for detecting the volume of intake air actually taken 
in the engine per revolution of the engine; and the air volume change 
limiter 152G for limiting the deviation of the actual intake air volume 
detected by the intake air volume detection means 152F from the target air 
volume set by the TEO realizing means 153C to a level not greater than the 
permissible air volume change obtained as a result of conversion by the 
converter means 152B and then outputting the thus-limited deviation as a 
target air change quantity, whereby the engine control quantity required 
to make a change of the actual intake air volume per revolution of the 
engine equal to the target air change value is set based on the target air 
change value outputted from the air volume change limiter 152G. The TV 
open/close limiting means 152C outputs, as the engine control quantity, a 
final target air volume obtained by summing the target air change value 
outputted from the air volume change limiter 152G and the actual intake 
air volume detected by the intake air volume detection means 152F. 
The system controls the output of the engine via the throttle valve 6 of 
the engine and the TEO realizing means 153C sets, as the engine control 
quantity, a target opening rate of the throttle valve required to actually 
obtain an engine output equal to the target engine output selected by the 
selector means 153B. The system, in which the output of the engine is 
controlled by the throttle valve 6 as described above, further comprises 
the converter means 152B for converting the permissible output change 
value, which has been set by the PTC setting means 152A, to a permissible 
air volume change per revolution of the engine, wherein the TV open/close 
limiting means 152C comprises the throttle opening rate-air volume 
converter unit 152D for converting the target opening rate, which has been 
set by the TEO realizing means 153C, to a target air volume which is an 
intake air volume per revolution of the engine; the TV open/close limiting 
means 152G for limiting the target air volume, which has been obtained as 
a result of conversion by the throttle opening rate-air volume converter 
unit 152D, on the basis of the permissible air volume change obtained as a 
result of conversion by the converter means 152B; and the air 
volume-throttle opening rate conversion unit 152E for setting, as the 
final target opening rate, an opening rate of the throttle valve required 
to make the actual intake air volume per revolution of engine equal to the 
target air volume limited by the air volume change limiter 152G. 
In this case, the TV open/close limiting means 152C further comprises the 
intake air volume detection means 152F for detecting the volume of intake 
air actually taken in the engine per revolution of the engine, the air 
volume change limiter 152G limits the deviation of the actual intake air 
volume detected by the intake air volume detection means 152F from the 
target air volume obtained as a result of conversion by the throttle 
opening rate-air volume converter unit 152D to a value not greater than 
the permissible air volume change obtained as a result of conversion by 
the converter means 152B, and the air volume-throttle opening rate 
conversion unit 152E determines the final target air volume by summing the 
target air change value outputted from the air volume change limiter 152G 
and the actual intake air volume detected by the intake air volume 
detection means 152F, thereby setting, based on the final target air 
volume, the final opening rate of the throttle valve required to make the 
volume of intake air taken in the engine per revolution of the engine 
equal to the final target air volume. 
The above drive-by-wire vehicle engine output control system further 
comprises the converter means 152B for converting the permissible output 
change value, which has been set by the PTC setting means 152A, to a 
permissible air volume change per revolution of the engine, wherein the TV 
open/close limiting means 152C limits the target opening rate, which has 
been set by the TEO realizing means 153C, on the basis of the permissible 
fuel volume change obtained as a result of conversion by the converter 
means 152B. 
The construction has been described centering on the AP-combined speed 
control unit 153. The construction will hereinafter be discussed centering 
on the running-load-compensating speed control unit 151. In this case, the 
drive-by-wire vehicle engine output control system is for setting the 
quantity of control of the engine in accordance with the state of 
operation of the accelerator pedal by the driver and the state of driving 
of the vehicle to electrically control the output of the engine on the 
basis of the control quantity or for controlling the output of the engine 
without relying upon operation of the accelerator pedal. The system 
comprises the vehicle speed detection means 151F for detecting the running 
speed of the vehicle; the TVS setting means 151A for setting a target 
vehicle speed upon autocruising in which the running speed of the vehicle 
is maintained constant; the SCT setting means 151B for determining the 
deviation of the running speed of the vehicle detected by the vehicle 
speed detection means 151F from the target vehicle speed set by the TVS 
setting means 151A and, based on the deviation, setting a speed correction 
torque as the correction quantity for the torque of the drive axle of the 
vehicle, said correction quantity being required to eliminate the 
deviation; the drive axle torque detection means 151E for detecting an 
actual drive torque of the drive axle; the RLT detection means 151G for 
detecting, based on the drive axle torque detected by the drive axle 
torque detection means 151E, a running load torque corresponding to a 
running load during running of the vehicle; the TAO means 151C for setting 
the target autocruise engine output on the basis of the speed correction 
torque set by the SCT setting means 151B and the running load torque 
detected by the RLT detection means 151G; and the TEO realizing means 151D 
for setting the engine control quantity at a level required to actually 
obtain an engine output equal to the target autocruise engine output set 
by the TAO means 151C. 
In this case, the RLT detection means 151G further comprises an 
acceleration torque detection means 107 for detecting an acceleration 
torque applied upon actual acceleration of the vehicle, whereby the 
running load torque is detected based on the drive axle torque detected by 
the drive axle torque detection means 151E and the acceleration torque 
detected by the acceleration torque detection means 107. Further, the RLT 
detection means 151G detects the running load torque by subtracting the 
acceleration torque detected by the acceleration torque detection means 
107 from the drive axle torque detected by the drive axle torque detection 
means 151B. The acceleration torque detection means 107 comprises the 
acceleration detection means S1 for detecting a running acceleration of 
the vehicle; and an acceleration torque computing unit S2 for computing 
the acceleration torque on the basis of the running acceleration detected 
by the acceleration detection means S1. 
In addition, the TAO means 151C sums the speed correction torque set by the 
SCT setting means 151B and the running load torque detected by the RLT 
detection means 151G, converts the resulting sum to the target autocruise 
engine output and then outputs the target autocruise engine output. 
The SCT setting means 151B comprises the PI control unit 101 for 
determining the deviation of the running speed of the vehicle detected by 
the vehicle speed detection means 151F from the target vehicle speed set 
by the TVS setting means 151A and setting a speed correction torque as the 
torque correction quantity for the drive axle of the vehicle, said torque 
correction quantity being required to eliminate the deviation; and the 
speed correction torque limiter 102 for limiting, within the predetermined 
range, the speed correction torque set by the PI control unit 101. 
The construction has been described centering on the 
running-load-compensating speed control unit 151. The construction will 
next be described centering on the output-torque-change-limiting speed 
control unit 152. In this case, the drive-by-wire vehicle engine output 
control system is for setting the quantity of control of the engine in 
accordance with the degree of depression of the accelerator pedal by the 
driver and the mode of operation of the vehicle to electrically control 
the output of the engine on the basis of the control quantity or for 
controlling the output of the engine without relying upon operation of the 
accelerator pedal. The system comprises the vehicle speed detection means 
151F for detecting a running speed of the vehicle; the TEO setting means 
153D for setting, based on the running speed detected by the vehicle speed 
detection means 151F, a target autocruise engine output as the target 
output value to be outputted from the engine to execute autocruising in 
which the running speed of the vehicle is maintained at the predetermined 
value; the TEO realizing means 153C for setting the engine control 
quantity at a level required to actually obtain an engine output equal to 
the target autocruise engine output set by the TEO setting means 153D; the 
PTC setting means 152A for setting a permissible output change value for 
the engine; and the TV open/close limiting means 152C for limiting, on the 
basis of the permissible output change value set by the PTC setting means 
152A, the engine control quantity set by the TEO realizing means 153C 
whereby changes in output of the engine are maintained not greater than 
the permissible output change value. 
In this case, the PTC setting means 152A converts the preset permissible 
value of the torque change at the drive axle of the vehicle to the 
permissible output change value on the basis of the current gear shift 
position of the transmission. The TEO realizing means 153C converts the 
target engine output, which has been selected by the TEO realizing means 
153C, to the target air volume--which is the volume of intake air per 
revolution of the engine required to actually obtain an engine output 
equal to the target autocruise engine output set by the TEO setting means 
153D--and then outputs the target air volume as the engine control 
quantity. Here, the above system further comprises further comprises the 
converter means 152B for converting the permissible output change value, 
which has been set by the PTC setting means 152A, to a permissible air 
volume change per revolution of the engine, whereby the TV open/close 
limiting means 152C controls the target air volume, which has been set by 
the TEO realizing means 153C, on the basis of the permissible air volume 
change obtained as a result of conversion by the converter means 152B. The 
TV open/close limiting means 152C comprises an intake air volume detection 
means 152F for detecting the volume of intake air actually taken in the 
engine per revolution of the engine, and an air volume change limiter 152G 
for limiting the deviation of the actual intake air volume detected by the 
intake air volume detection means 152F from the target air volume set by 
the TEO realizing means 153C to a level not greater than the permissible 
air volume change obtained as a result of conversion by the converter 
means 152B and then outputting the thus-limited deviation as a target air 
change quantity, whereby the engine control quantity required to make a 
change of the actual intake air volume per revolution of the engine equal 
to the target air change value is set based on the target air change value 
outputted from the air volume change limiter 152G. 
Further, the TV open/close limiting means 152C sets, as the engine control 
quantity, the final target air volume obtained by summing the target air 
change value outputted from the air volume change limiter 152G and the 
actual intake air volume detected by the intake air volume detection means 
152F. 
In the above system which controls the output of the engine via the 
throttle valve 6 of the engine, the TV open/close limiting means 152C 
sets, as the engine control quantity, the target opening rate of the 
throttle valve required to actually obtain an engine output equal to the 
target autocruise engine output set by the engine output setting means 
153D. 
The system which controls the output of the engine via the throttle valve 6 
also comprises the converter means 152B for converting the permissible 
output change value, which has been set by the PTC setting means, to a 
permissible air volume change per revolution of the engine, and the TV 
open/close limiting means 152C comprises the throttle opening rate-air 
volume converter unit 152D for converting the target opening rate, which 
has been set by the TEO realizing means 153C, to a target air volume which 
is an intake air volume per revolution of the engine, the air volume 
change limiter 152G for limiting the target air volume, which has been 
obtained as a result of conversion by the throttle opening rate-air volume 
converter unit 152D, on the basis of the permissible air volume change 
obtained as a result of conversion by the converter means 152B, and the 
air volume-throttle opening rate converter unit 152E for setting, as the 
final target opening rate, an opening rate of the throttle valve required 
to make the actual intake air volume per revolution of engine equal to the 
target air volume limited by the air volume change limiter 152G. 
In this case, the TV open/close limiting means 152C further comprises the 
intake air volume detection means 152F for detecting the volume of intake 
air actually taken in the engine per revolution of the engine, the air 
volume change limiter 152G limits the deviation of the actual intake air 
volume detected by the intake air volume detection means 152F from the 
target air volume obtained as a result of conversion by the throttle 
opening rate-air volume converter unit 152D to a value not greater than 
the permissible air volume change obtained as a result of conversion by 
the converter means 152B, and the air volume-throttle opening rate 
converter unit 152E determines a final target air volume by summing the 
target air change value outputted from the air volume change limiter 152G 
and the actual intake air volume detected by the intake air volume 
detection means 152F, thereby setting, based on the final target air 
volume, the final opening rate of the throttle valve required to make the 
volume of intake air taken in the engine per revolution of the engine 
equal to the final target air volume. 
A description will next be made of a transmission control unit 154. As is 
depicted in FIG. 9(a), an output signal from the engine revolution number 
sensor 17a for detecting the revolution number of the engine and an output 
signal from an accelerator pedal position sensor 15A for detecting, as an 
accelerator operation state detection means, a stroke (operated state) of 
the accelerator pedal 15 are inputted to an output torque margin detection 
means 154A. In the output torque margin detection means 154A, a 
characteristic showing the relationship between the engine revolution 
number and the throttle valve position (throttle opening rate) are stored 
as a map as shown by a solid curve in FIG. 10(b), whereby an area defined 
using this characteristic as a standard and having no engine output torque 
margin is set. 
Further, another area for judging from the output of the accelerator 
position sensor 15A if the accelerator pedal 15 is in a stroke end area is 
also set as indicated by the hatched area in FIG. 10(a). 
A margin signal indicating if there is a margin in the output torque of the 
engine is inputted to a transmission control means 154B. When there is no 
margin, the transmission control means 154B outputs a shift-down signal to 
the automatic transmission 20. 
Owing to the construction described above, the transmission control unit 
154 operates following the flow chart shown in FIG. 9(b). 
Namely, the accelerator pedal 15 is treadled to the stroke end area out of 
the areas preset in FIG. 10(a) and, by the output torque margin detection 
means 154A, it is judged if the driver is demanding high acceleration 
(step 54A). 
If the accelerator pedal 15 is located in the stroke end area, it is judged 
if an engine operation state, which is determined from the engine 
revolution number Ne and the position of the throttle valve 6, is located 
within the area set in FIG. 10(b). 
Namely, in the hatched area of the map, a lower-limit throttle valve 
position corresponding to the engine revolution number Ne is read (step 
54B), whereby it is judged if the current throttle valve position detected 
by the throttle valve position sensor 8 is greater (i.e., is treadled 
more) than the lower-limit throttle valve position so read (step 54C). 
If the result of the above judgment is YES, the output torque margin 
detection means 154A is judged to show the state that there is no margin 
in the engine output although there is an acceleration demand of at least 
a predetermined level. Accordingly, a shift-down signal is outputted to 
the transmission 20 via the transmission control means 154B (step 54D). As 
a result, shift-down control (kick-down control) is performed by the 
transmission 20 so that acceleration of the vehicle is effected fully. 
As has been described above, kick-down control can also be carried out 
fully in a DBW vehicle. Namely, kick-down control can be conducted 
effectively even in control such that the stroke of the accelerator pedal 
and the open/closure of the throttle valve 6 do not correspond directly in 
a DBW vehicle in which there is no mechanical interconnection between the 
throttle valve 6 and the accelerator pedal 15. The shift-down is conducted 
automatically so that driving can be facilitated. 
The above-described margin of the engine output torque was judged from the 
throttle valve opening rate .theta. and the engine revolution number Ne. 
It is possible to use the air volume per revolution of engine (A/N) 
instead of the throttle valve opening rate .DELTA.. As a further 
alternative, the judgment can also be made using the fuel volume per 
revolution of the engine (A/N). As a still further alternative, the 
judgment can also be conducted using the fuel volume per revolution of the 
engine (F/N). In these cases, it is judged from a graph similar to the 
graph of FIG. 10(b) except for plotting of A/N or F/N along the axis of 
abscissas if there is a margin in the engine output upon kickdown. 
An acceleration shock prevention control unit (hereinafter referred to as 
the "AS prevention control unit) 158 will next be described. As is 
illustrated in FIG. 14, the state of treadling of the accelerator pedal 15 
is detected by an accelerator pedal position sensor (APS) 15A. A detection 
signal from the accelerator pedal position sensor 15A is then inputted to 
the AS prevention control unit 158. 
The AS prevention control unit 158 is provided with an acceleration demand 
detection means 158A which detects an acceleration demand of the driver 
upon receipt of the output signal from the accelerator pedal position 
sensor 15A. The AS prevention control unit 158 is also provided with a 
condition determining means 158D adapted to determine a limit operation 
condition for the engine. The condition determining means 158D serves to 
determine an engine operation range which does not cause acceleration 
shock, and the condition determining means 158D is equipped with a map 
corresponding to the characteristics depicted in FIGS. 16(a) and 16(b). 
An acceleration limiting unit 158B is also provided. The acceleration 
limiting unit 158 is inputted with a target acceleration demand signal 
from the acceleration demand detection means 158A and also with a limit 
operation condition for the engine from the condition determining means 
158D. The acceleration limiting unit 158B is designed to output a limit 
signal upon input of an acceleration demand exceeding the limit operation 
condition. 
The limit signal and target acceleration demand signal are inputted to a 
control means 158C, whereby the throttle valve 6 is controlled by the 
control means 158C by way of the motor 7. 
Owing to the construction described above, control is conducted by the AS 
prevention control unit 158, following the flow chart of FIG. 15. 
First, based on outputs from various sensors, the operation state of the 
engine is detected by the condition determining means 158D (step 58A). 
A limit to the throttle opening rate is then determined as a limit 
operation condition from the map of the characteristics shown in FIG. 
16(a) (step 58B). Namely, for example, using a characteristic curve on 
which crossing points of engine revolution numbers Nei detected by the 
revolution number sensor 17a and detected engine torques Ti exist, i.e., 
the characteristic curve indicated by the solid curve in this example, a 
limit throttle opening rate .theta.i is determined and is then outputted 
to the acceleration limiting unit 158B. 
As a result of the input of the state of treadling of the accelerator pedal 
15 detected by the accelerator pedal position sensor 15A to the 
acceleration demand detection means 158A, the target acceleration demand 
torque demanded by the driver is detected. The target acceleration demand 
torque is converted to a target throttle opening rate and is transmitted 
to the acceleration limiting unit 158B. 
By the acceleration limiting unit 158B, it is judged if the target throttle 
opening rate is greater than the limit throttle opening rate .theta.i as 
the opening rate limit (step 58C). If greater, the limit signal is 
transmitted to the control means 158C. 
The control means 158C outputs a control signal to the throttle valve 6 via 
the motor 7 so that the throttle valve 6 is driven at a usual drive speed 
to the opening rate limit .theta.i (step 58D). For a throttle valve 
opening rate (an opening rate greater than the limit .theta.i) 
corresponding to the limit signal so transmitted, a control signal is 
outputted to drive the throttle valve at a drive speed slower by a 
predetermined percentage than the usual drive speed (step 58E). 
Where the target throttle opening rate is smaller than or equal to the 
opening rate limit, the acceleration limiting unit 158B outputs a control 
signal to the control means 158C in order to have the throttle valve 
driven at the usual speed up to the target throttle opening rate (step 
58F). 
Incidentally, the above operation is represented by the relationship 
between throttle valve opening rate and time, said relationship being 
illustrated in FIG. 16(b). Up to the limit operation condition (opening 
rate: .theta.i), the opening of the throttle valve is carried out at a 
maximum drive speed owing to an unconditional opening rate increase. 
Accordingly, quick-response starting acceleration is conducted and, in the 
subsequent acceleration range where acceleration shock tends to occur, 
running is performed under shock-free limit acceleration conditions. 
The determination of the above-described limit operation condition for not 
causing acceleration shock relies upon a prescribed engine output torque 
for a given engine revolution number as shown in FIG. 16(a). This can also 
be done under the following conditions for determination: 
(1) Prescribed A/N for a given engine revolution number. 
(2) Prescribed negative pressure in an intake tube for a given engine 
revolution number. 
(3) Prescribed fuel injection rate for a given engine revolution number. 
(4) Prescribed throttle opening rate irrespective of the state of 
operation. 
The control output from the AS prevention control unit 158 follows a 
prescribed order of preference in relation to outputs by other controls 
performed in parallel with the present control and also a mode set by the 
driver, and is outputted to the throttle valve 6. 
As an alternative, the control output from the AC prevention control unit 
158 may be used as an effective output only when its application is 
limited to acceleration of the automotive vehicle from idling or to its 
acceleration from the first gear position. 
It is also possible to make the opening speed of the throttle valve under 
an operation condition not reaching the limit operation condition 
correspond to the operation speed of the accelerator pedal by the driver 
or to make it equal to the maximum drive speed. 
In this manner, uncomfortable shock can be prevented to ensure smooth 
acceleration even if the operation of the accelerator pedal by the driver 
is not suitable. 
Such advantageous effects as described above can be achieved only by 
modifications in the software, thereby making it possible to achieve 
improvements at a low cost. 
A description will next be made of a vehicle-running-state-associated mode 
change-over control unit (hereinafter referred to as the "VRS-associated 
mode change-over control unit") 156. As is shown in FIG. 17, the 
VRS-associated mode change-over control unit 156 is designed such that a 
throttle valve open/close control signal is outputted upon input of a 
stroke of the accelerator pedal 15 to the VRS-associated mode change-over 
control unit 156 via the accelerator pedal position sensor 15A. The 
VRS-associated mode change-over control unit 156 is provided with a mode 
change-over means 156A, a running state detection means 156B and a 
throttle valve control means 156C. 
The mode change-over means 156A has two setting modes, one being a normal 
mode and the other an economy mode. The mode change-over means 156A is 
designed to calculate throttle opening rates corresponding to the 
individual modes in relation to the stroke of the accelerator pedal 15. In 
the normal mode, for a stroke of the accelerator pedal 15, the throttle 
opening rate as demanded by the driver or a relatively large throttle 
opening rate placing importance on the output characteristics of the 
engine is set. 
In the economy mode on the other hand, for a stroke of the accelerator 
pedal 15, an opening rate smaller than that demanded by the driver or a 
relatively slow throttle opening speed is set so that the engine can be 
operated in a good fuel-consumption range. 
The throttle valve control means 156C is designed to output a control 
signal such that the target throttle valve opening rate so inputted can be 
realized. 
On the other hand, vehicle speed information detected by a still further 
control unit and an output signal from the engine revolution number sensor 
17a are inputted to the running state detection means 156B so that the 
running state of the vehicle can be detected. The running state detection 
means 156B is also designed to output a change-over signal to the mode 
change-over means 156A, depending on the running state. Namely, the 
characteristic map shown in FIG. 19(a) is stored, whereby it is determined 
by the vehicle speed V and the engine revolution number Ne whether the 
running state of the vehicle is in the normal mode range or in the economy 
mode range. 
In addition to the normal mode and economy mode, plural intermediate modes 
can be added as shown in FIG. 19(b). The running state detection means 
156B can then be designed to permit automated selection of the most 
suitable mode from these plural modes. 
Owing to the construction described above, the VRS-associated mode 
change-over control unit 156 operates following the flow chart shown in 
FIG. 18. 
Namely, the speeds of respective wheels are detected by their corresponding 
wheel speed sensors 13a,13b,13c,13c (step 56A). By the running state 
detection means 156B, an average moving vehicle speed V is calculated from 
the speeds of the respective wheels (step 56B). 
By the engine revolution sensor 17a, it is judged based on the detected 
revolution number Ne and the above-calculated vehicle speed V and using 
the map shown in FIG. 19(a) if the vehicle speed V is lower than a 
predetermined value for judgment (step 56C), whereby it is determined 
whether the running state of the vehicle is in the normal range or in the 
economy range. The change-over signal selected depending on whether the 
running state of the vehicle is in the normal range or in the economy 
range is outputted to the mode change-over means 156A. 
Upon receipt of the change-over signal described above, the mode 
change-over means 156A decides whether the economy mode should be set 
(step 56D) or the economy mode is canceled in favor of setting of the 
normal mode (step 56E). 
By the mode change-over means 156A, a correction is performed to the either 
one of the modes determined as described above and, in accordance with the 
correlation map between the state of treadling of the accelerator pedal 15 
and the opening rate of the throttle valve, a target throttle valve 
opening rate corresponding to the output signal from the accelerator pedal 
position sensor 15A is determined. This target throttle valve opening rate 
is then outputted to the throttle valve control means 156C. 
As a result, the throttle valve 6 is subjected to open/close control via 
the motor 7 in the mode automatically selected corresponding to the 
running state of the vehicle. 
In this manner, the failure of Change-over from the economy mode to the 
normal mode, said failure having occurred to date, can be eliminated, 
thereby making it possible to avoid such a problem that the vehicle is 
driven in a state not possible to obtain a desired output or under poor 
fuel consumption. The operational ease for the driver and the running 
performance of the vehicle can therefore be improved as advantages. 
If such intermediate modes as shown in FIG. 19(b) are provided, an economy 
correction coefficient K is determined in relation to the vehicle speed V 
and the engine revolution number Ne. This correction coefficient K ranges 
form 0 (inclusive) to 1 (inclusive) [0.ltoreq.K.ltoreq.1]. The normal mode 
is selected at K=0, whereas the economy mode is chosen at K=1. Using this 
K, computation of the target throttle opening rate is conducted in 
accordance with the following formula: 
EQU Throttle opening rate=f-K.multidot.g 
where 
f: function of the opening rate of the accelerator pedal in the normal 
mode; 
g: function of the opening rate of the accelerator pedal in the economy 
mode; and 
K: economy correction coefficient. 
By achieving this throttle opening rate, an intermediate mode corresponding 
to the running state can be realized. 
By the above-described running state detection means 156B, it is judged to 
perform a mode change-over or not depending on whether the state of 
operation at the average moving vehicle speed V of the vehicle is at least 
equal to the prescribed engine revolution number Ne as shown in FIGS. 
19(a) and 19(b). This can also be carried out in accordance with the 
following mode change-over judgment conditions: 
(1) Average vehicle speed during a predetermined time period as determined 
from wheel speed information. 
(2) Maximum vehicle speed during a predetermined time period as determined 
from wheel speed information. 
(3) Average vehicle body acceleration during a predetermined time period as 
determined from wheel speed information. 
(4) Maximum vehicle body acceleration during a predetermined time period as 
determined from wheel speed information. 
(5) Average engine revolution number during a predetermined time period as 
determined from engine revolution number information. 
(6) Maximum engine revolution number during a predetermined time period as 
determined from engine revolution number information. 
(7) Average increase rate of engine revolution number during a 
predetermined time period as determined from engine revolution number 
information. 
(8) Maximum increase rate of engine revolution number during a 
predetermined time period as determined from engine revolution number 
information. 
(9) Average vehicle body speed and average engine revolution number. 
The mode is switched to the economy mode when the vehicle speed, 
acceleration, engine revolution number or the like is low or small in the 
conditions (1)-(9). If high or great, the mode is switched to the normal 
mode. 
Automated change-over is conducted between the normal mode and the economy 
mode or vice versa in the present embodiment. As a modification, a mode 
change-over switch 156D can be provided to choose an auto mode in which 
automated mode change-over is performed or a manual mode in which mode 
change-over is performed by the driver. Automated mode change-over is 
therefore conducted only when the mode change-over switch 156D is in the 
auto mode. 
A description will next be made of an accelerator-pedal-associated mode 
change-over control unit (hereinafter referred to as the "AP-associated 
mode change-over control unit") 157. As is illustrated in FIG. 20, the 
AP-associated mode change-over control unit 157 is designed such that a 
stroke of the accelerator pedal 15 is inputted to the AP-associated mode 
change-over control unit 157 via the accelerator pedal position sensor 15A 
to output a throttle valve open/close signal. The AP-associated mode 
change-over control unit 157 is provided with a mode change-over means 
157B, an engine ability demand, detection means 157A and a throttle valve 
control means 157C. 
The mode change-over means 157B has two setting modes, one being a normal 
mode and the other an economy mode. The mode change-over means 157B is 
designed to calculate throttle opening rates corresponding to the 
individual modes in relation to the stroke of the accelerator pedal 15. 
In the normal mode, for a stroke of the accelerator pedal 15, the throttle 
opening rate as demanded by the driver or a relatively large throttle 
opening rate placing importance on the output characteristics of the 
engine is set. 
In the economy mode on the other hand, for a stroke of the accelerator 
pedal 15, an opening rate smaller than that demanded by the driver or a 
relatively slow throttle opening speed is set so that the engine can be 
operated in a good fuel-consumption range. 
The throttle valve control means 157C is designed to output a control 
signal such that the target throttle valve opening rate so inputted can be 
realized. 
On the other hand, an output signal from the accelerator pedal position 
sensor 15A is inputted to the engine ability demand detection means 157A 
so that the engine ability demand by the driver can be detected. The 
engine ability demand detection means 157A is also designed to output a 
change-over signal to the mode change-over means 157B, depending on the 
demand. 
Namely, the characteristic map shown in FIG. 21(a) is stored, whereby it is 
determined by the stroke and treadling speed of the accelerator pedal 15 
which one of the normal mode range and the economy mode range should be 
selected. 
In addition to the normal mode and economy mode, plural intermediate modes 
can be added as shown in FIG. 21(b). The engine ability demand detection 
means 157A can be designed to permit automated selection of the most 
suitable mode from these plural modes. 
Owing to the construction described above, the AP-associated mode 
change-over control unit 157 operates following the flow chart shown in 
FIG. 22. 
Namely, the position of the accelerator pedal 15 is detected by the 
accelerator pedal position sensor 15A (step 57A), and the stroke and 
treadling speed of the accelerator pedal 15 are computed by the engine 
ability demand detection means 157A (step 57B). 
Then, in accordance with the map of the characteristics shown in FIG. 
21(a), either a normal mode range or an economy mode rage is automatically 
selected corresponding to the stroke and treadling speed of the 
accelerator pedal 15. 
As a result, the mode corresponding to the engine ability demand by the 
driver is automatically selected and control is then performed under the 
mode so-selected. 
Namely, a change-over signal to the mode so selected is outputted to the 
mode change-over means 157B. Upon receipt of the change-over signal, the 
mode change-over means 157B sets the economy mode (step 57E) or cancels 
the economy mode in favor of setting of the normal mode (step 57F). 
At the mode change-over means 157B, by a correlation map between the state 
of treadling of the accelerator pedal 15 in the mode determined as 
described above and the opening rate of the throttle valve, a target 
throttle valve opening rate corresponding to the output signal from the 
accelerator pedal position sensor 15A is determined. This target throttle 
valve opening rate is then outputted to the throttle valve control means 
157C. 
As a result, the throttle valve 6 is subjected to open/close control via 
the motor 7 in the mode automatically selected corresponding to the demand 
of the driver. 
In this manner, the failure of change-over from the economy mode to the 
normal mode, said failure having occurred to date, can be eliminated, 
thereby making it possible to avoid such a problem that the vehicle is 
driven in a state not possible to obtain a desired output or under poor 
fuel consumption. The operational ease for the driver and the running 
performance of the vehicle can therefore be improved as advantages. 
By the engine ability demand detection means 157A, it is detected which one 
of the two mode is demanded, namely, whether the normal mode or the 
economy mode is demanded. If such intermediate modes as shown in FIG. 
21(b) are provided, an economy correction coefficient K' is determined in 
relation to the stroke and treadling speed of the accelerator pedal 15. 
This correction coefficient K' ranges form 0 (inclusive) to 1 (inclusive) 
[0.ltoreq.K'.ltoreq.1]. The normal mode is selected at K'=0, whereas the 
economy mode is chosen at K'=1. 
This correction coefficient K' is outputted to the mode change-over means 
157B and computation of the target throttle opening rate is conducted in 
accordance with the following formula: 
EQU Throttle opening rate=f'-K'.multidot.g' 
where 
K': correction coefficient; 
f',g': throttle opening rates determined in accordance with function of the 
stroke or treadling speed of the accelerator pedal, f' corresponds to the 
normal 
mode, and g' corresponds to the economy mode. 
By achieving this throttle opening rate, an intermediate mode demanded by 
the driver can be realized. 
By the above-described engine ability demand detection means 157A, judgment 
of mode change-over is performed depending on whether or not the treadling 
speed of the accelerator pedal 15 is at least equal to a predetermined 
value for a given stroke of the accelerator pedal 15. Judgment of a mode 
can also be carried out by detecting the driver's engine ability demand in 
accordance with the following mode change-over judgment conditions: 
(1) Treadling speed of the accelerator pedal 15 as determined from an 
output from the accelerator pedal position sensor 15A. 
(2) Average treadling speed of the accelerator pedal during a predetermined 
time period. 
(3) Stroke of the accelerator pedal 15 as determined from an output from 
the accelerator pedal position sensor 15A. 
(4) Average stroke of the accelerator pedal 15 as determined from an output 
from the accelerator position sensor 15. 
The mode is switched to the economy mode when the treadling speed, stroke 
or the like is low or small in the conditions (1)-(4). If high or great, 
the mode is switched to the normal mode. 
It is also possible to design such that the mode is switched to the normal 
mode when the treadling speed of the accelerator pedal 15 is equal to or 
greater than a predetermined value under predetermined engine operation 
conditions such as at a predetermined engine rotation number or the like 
or to the economy mode when the treadling speed is smaller. 
Automated change-over is conducted between the normal mode and the economy 
mode or vice versa in the present embodiment. As a modification, a mode 
change-over switch 157D can be provided to choose an auto mode in which 
automated mode change-over is performed or a manual mode in which mode 
change-over is performed by the driver. Automated mode change-over is 
therefore conducted only when the mode change-over switch 157D is in the 
auto mode. 
A description will next be made of a vehicle body speed detection 
compensation control unit 166. As is illustrated in FIG. 23, non-driven 
wheel speed sensors 13a,13b applied to left and right non-driven wheels 
13A,13B, respectively, are connected to the vehicle body speed detection 
compensating control unit 166 to transmit output signals of the speed 
sensors 13a,13b to the control unit 166. The control unit 166 is provided 
with a failure detection means 166A, a compensation control means 166B and 
a running control unit 166C. 
The failure detection means 166A is designed to always monitor the outputs 
of the non-driven wheel speed sensors 13a,13b so that they can detect 
failure, for example, by relying upon any output outside a normal range or 
absence of any change in the output for a predetermined time or longer. 
The failure detection means 166A therefore identifies any failed sensor 
and outputs a failure signal. 
The compensation control means 166B is designed such that it receives a 
failure signal from the failure detection means 166A and compensates 
information from the failed non-driven wheel speed sensor 13a or 13b in 
accordance with a correction by an output signal from another sensor. 
If either one of the non-driven wheel speed sensors 13a,13b should fail, a 
turning correction is applied by a steering operation angle detected by a 
steering angle sensor 121 to an output signal from the remaining 
non-driven wheel speed sensor 13a(13b) so that a vehicle speed V is 
obtained and outputted. 
If both the non-driven wheel speed sensors 13a,13b should fail, an output 
signal from an output shaft revolution number sensor 20A of an automatic 
transmission 20 is corrected depending on the gear shift position and is 
then outputted as a simulated vehicle body speed. 
The running control unit 166C is designed to perform automatic speed 
control (ASC). The control is conducted using the vehicle speed V which is 
obtained from the output signals of the wheel speed sensors 13a,13b. 
Further, the running control unit 166C also receives sensor failure 
information from the failure detection means 166A and a simulated vehicle 
body speed signal outputted from the compensation control means 166B 
besides the signals outputted from the wheel speed sensors 13a,13b, 
whereby the running control unit 166C is continuously allowed to operate 
even during failure of the wheel speed sensors 13a,13b. 
Owing to the construction described above, the vehicle speed detection 
compensation control unit 166 operates following the flow chart shown in 
FIG. 24. 
When the failure detection means 166A detects failure of the lift and right 
non-driven wheel speed sensors 13a,13b (steps 66A,66B), the compensation 
control means 116B outputs a suspension signal to the running control unit 
166C so that any control requiring a highly-accurate vehicle speed such as 
traction control is suspended (step 66D). 
By the compensation control means 166B, it is judged if only one of the 
non-driven wheel speeds sensors 13a,13b has failed (step 66E). If so, a 
non-driven wheel speed on the fail-free side is compensated by a detection 
signal from the steering angle sensor 121 which serves to detect the 
steering angle of the steering so that a vehicle speed is obtained (steps 
66F,66G). This vehicle speed is then outputted to the running control unit 
166C whereby various running controls are continued. 
If the non-driven wheel speed sensors 13a,13b on the both sides have 
failed, a detection signal is received from the output shaft revolution 
number sensor 20A of the automatic transmission 20 (step 66H) and 
information on the gear shift position of the automatic transmission 20 is 
also inputted in the form of an output signal from the shift position 
sensor 20B of the automatic transmission 20. A simulated vehicle speed is 
hence computed and then outputted to the running control unit 166C. 
As a result, even if the non-driven wheel speed sensors 13a,13b should 
fail, the automatic speed (cruise) control (ASC) by the running control 
unit 166C is continued. 
The above-described compensation of the non-driven wheel speed by the 
steering angle is conducted using a compensation coefficient Ks shown in 
FIG. 25. The compensation coefficient Ks increases in the form of a 
first-degree function relative to the steering angle change .DELTA..THETA. 
as shown in the drawing. However, Ks =0 in the steering angle change range 
of from .DELTA..THETA..sub.1 to .DELTA..THETA..sub.2. This range is taken 
as a dead zone so that no compensation is conducted there to ensure stable 
drivability. 
The vehicle speed can be accurately detected as described above even during 
failure of the non-driven wheel sensor(s), thereby bringing about the 
advantage that suspension of the control system can be avoided. 
A description will next be made of an accelerator pedal position sensor 
failure-time acceleration control unit (hereinafter referred to as the 
"APS-failure-time acceleration control unit) 162. As is illustrated in 
FIG. 26, the APS-failure-time acceleration control unit 162 is inputted 
via the accelerator pedal position sensor 15A with information on a stroke 
of the accelerator pedal 15 and via a brake switch 21A as a brake pedal 
sensor with information on a stroke of the brake pedal 21. 
The control unit 162 is provided with a failure detection means 162A and an 
acceleration control unit 162B. The acceleration control unit 162B is 
formed of a failure-time control unit 162C and a control means 162D. 
The failure detection means 162A always monitors the output of the 
accelerator pedal position sensor 15A and, when the output does not change 
for a predetermined time or longer or an abnormal output is detected, 
outputs a failure signal to the failure-time control unit 162C. 
The failure-time control unit 162C is designed to outputs a failure-time 
control opening rate for the throttle valve 6 when a failure signal is 
inputted. The control unit 162C uses a memory counter or the like. If the 
brake remains not operated, the failure-time control opening rate is 
gradually increased from an opening rate slightly greater than the opening 
rate during idling to an upper limit of the opening rate. 
The control means 162D is designed to control the throttle valve 6 by the 
DBW (drive-by-wire) method. A control means of the ASC (automatic speed 
control) type or the like is assembled in the control means 162D. 
Owing to the construction described above, the APS-failure-time 
acceleration control unit 162 operates following the flow chart shown in 
FIG. 27. 
When failure of the accelerator pedal position sensor 15A is detected by 
the failure detection means 162A, the operation of the flow chart is 
started. A predetermined throttle opening rate, which has been set in 
advance, is outputted as a target opening rate to the control means 162D 
(step 62A), so that the throttle valve 6 is operated to a prescribed 
throttle opening rate. 
The prescribed throttle opening rate described above is set to an opening 
rate such that an engine output a little greater than that during idling 
can be obtained. 
It is then judged based on an output signal from the brake switch 21A if 
the brake pedal 21 has been operated (step 62B). If not, step 62C is 
executed. 
Namely, it is judged if a predetermined time has elapsed since the throttle 
opening rate was renewed to the prescribed throttle opening rate. If not, 
the output is maintained at a level by a prescribed throttle opening rate, 
which is somewhat greater than the throttle opening rate during idling 
(step 62H). 
If the predetermined time has elapsed, the target opening rate of the 
throttle valve increases to a value added with a predetermined increment 
(step 62D) so that operation is performed at a throttle opening rate a 
little greater than the last throttle opening rate. 
The target opening rate is gradually increased by the increment described 
above. It is monitored if the target opening rate so increased does not 
exceed the prescribed upper limit of the opening rate (step 62E). If the 
target opening rate increases the prescribed upper limit of the opening 
rate, the prescribed upper limit of the opening rate is always chosen as a 
target opening rate (step 62F). 
The target opening rate so determined is outputted to the control means 
162D and, while being limited to a target output opening rate from another 
control means, medium- or low-speed operation is continued without 
substantial reduction in the running performance even at the time of 
failure of the accelerator pedal position sensor 15A. 
If, at the time of failure of the accelerator pedal position and during 
operation, the brake 21 is operated and the brake switch 21A is turned on, 
step 62G is executed. As a result, the target opening rate of the throttle 
valve 6 is changed to a prescribed initial opening rate or 0 and the 
throttle valve 6 returns to an opening rate corresponding to a lowest 
speed after the failure of the accelerator pedal position sensor or to the 
full close. This makes it possible to avoid an accident or the like. 
Upon limiting the opening rate of the throttle valve as described above, 
the limitation to the throttle opening rate may be corrected by the 
vehicle body speed or the steering angle of the steering. 
Instead of turning on the brake switch 21A in the manner described above, 
the above-described closure of the throttle valve 6 can be conducted in 
accordance with the following standards for judgment. 
(1) By the detection of deceleration of the vehicle body from the vehicle 
body speed obtained from the speed of each wheel. 
(2) By the detection of deceleration of the vehicle body based on a gravity 
(G) sensor. 
(3) By a brake hydraulic pressure. 
In this manner, even if failure takes place on the accelerator pedal 
position sensor 15A, the vehicle is still allowed to run at a medium or 
low speed without sudden stoppage so that the driver is allowed to safely 
stop the vehicle while avoiding danger to which the driver would be 
exposed if such sudden stoppage took place. 
In the state that the brake is not operated, the throttle opening rate can 
be increased gradually to the upper limit of the engine output that 
assures safety. The vehicle can therefore be driven without substantially 
reducing the running performance. 
A description will next be made of an accelerator pedal position sensor 
failure-time, brake-switch-associated control unit (hereinafter referred 
to as the "APS failure time, BS-associated control unit) 161. As is 
illustrated in FIG. 28(a), a stroke of the accelerator pedal 15 is 
inputted to the control unit 161 via the accelerator pedal position sensor 
15A and the state of operation of the brake 21 is also inputted to the 
control unit 161 via the brake switch 21A. 
The control unit 161 is provided with a deceleration demand detection means 
161A, a deceleration demand time control unit 161B and an acceleration 
control unit 161C. 
Upon reception of an ON signal from the brake switch 21A as a result of 
operation of the brake pedal, the deceleration demand detection means 161A 
detects the deceleration demand and then outputs a deceleration demand 
signal. 
Upon receipt of the deceleration demand signal, the deceleration demand 
time control unit 161B performs the operation of the flow chart of FIG. 
28(b) by an internal computation means and outputs a target throttle 
opening rate to the acceleration control unit 161C. 
The acceleration control unit 161C receives the target opening rate for the 
throttle valve 6 and performs open/close control of the throttle valve 6 
via the motor 7. The acceleration control unit 161C is equipped with 
function such as autocruise control of the DBW type. 
Owing to the construction described above, the APS failure time, 
BS-associated control unit 161 operates following the flow chart of FIG. 
28(b). 
During normal operation, an output signal from the accelerator position 
sensor 15A is read by the acceleration control unit 161C (step 61A). A 
target throttle opening rate is thus computed (step 61B) and is then 
outputted, whereby the throttle valve 6 is driven to achieve acceleration 
as desired. 
While such operation is carried out, the signal from the brake switch 15A 
is always read (step 61C) and is monitored (step 61D) by the deceleration 
demand detection means 161A. When the brake switch 15A is turned on, the 
deceleration demand detection means 161A outputs a deceleration demand 
signal to the deceleration demand time control unit 161B. 
At the deceleration demand time control unit 161B, the target throttle 
opening rate at that time and a prescribed throttle opening rate, which 
has been set in advance, are compared (step 61E). When the target throttle 
opening rate is greater than the prescribed throttle opening rate, a 
predetermined throttle opening rate is adopted as the target throttle 
opening rate (step 61F) and this opening rate is then transmitted to the 
acceleration control unit 161C. 
In this manner, the acceleration control unit 161C closes the throttle 
valve 6 to the predetermined throttle opening rate. 
Since the predetermined throttle opening rate is set at such an opening 
rate as permitting safe drive even at the time of failure of the 
accelerator position sensor, it is still possible to drive at a safe speed 
even when the accelerator position sensor 15A fails. 
Incidentally, the deceleration demand detection by the deceleration demand 
detection means 161A can be carried out in accordance with the following 
standards for judgment. 
(1) Vehicle body deceleration computed based on the speed of each wheel. 
(2) Vehicle body deceleration obtained from the G sensor. 
(3) Change in the brake hydraulic pressure. 
Instead of limiting the opening rate of the throttle valve 6 to the 
predetermined throttle opening rate, the deceleration demand time control 
unit 161B may be allowed to satisfy a deceleration demand in the following 
manner. 
(1) The intake negative pressure is limited to limit the state of operation 
of the engine. 
(2) A/N is limited to limit the state of operation of the engine. 
(3) The fuel injection rate is limited to limit the state of operation of 
the engine. 
In this manner, even at the time of failure of the accelerator pedal 
position sensor 15A or the like, the state of operation of the engine (the 
throttle valve opening rate) can be controlled in a safe state by the 
driver's intention of deceleration such as brake application whereby the 
driver can stop the vehicle after running at a safe speed. 
Even if failure takes place on the accelerator pedal position sensor 15A or 
the like on a highway or the like, it is still possible to avoid sudden 
stoppage and hence to safely stop the vehicle without danger. 
When the driver has made an acceleration demand during or after the 
movement to the predetermined throttle opening rate by a deceleration 
means such as a brake, the throttle valve is operated responsive to the 
acceleration demand from the predetermined opening rate. No substantial 
discomfort therefore takes place in the state of operation. 
Use of a conventional means such as a brake switch as the deceleration 
demand detection means can bring about the above-described advantageous 
effects without cost increase. 
An engine-associated initialization inhibiting control unit 165 will next 
be described. As is shown in FIG. 29, the control unit 165 is inputted 
with an operation signal from a starter 22, which is actuated in 
association with an ignition switch 22A, and with information indicative 
of the state of operation of the engine, for example, with information on 
the engine revolution number. 
The operation signal from the starter 22 is transmitted to a starter 
operation detection means 165A so that the state of operation of the 
starter 22 can be detected. 
A detection signal is inputted to an engine operation detection means 165B 
from the engine revolution number sensor 17a, whereby the state of 
operation of the engine can be detected. 
Further, a throttle valve control system 165D is also provided. The system 
165D is equipped with various functions to perform controls such as 
autocruise and s designed to control the drive of the throttle valve 6 and 
the motor 7. 
The throttle valve control system 165D is also provided with an 
initializing means 165E. This initializing means 165E outputs an 
initializing signal to the throttle valve control system 165D, whereby the 
throttle valve 6 is operated to the full close position or to the full 
open position to adjust its standard position or to confirm failure 
diagnosis of the throttle position sensor 8, the motor 7 and the like. 
The initializing means 165E is provided with an initialization inhibiting 
means 165C, which outputs an initialization inhibiting signal to the 
initializing means 165E when execution of initialization is not preferred 
from the standpoint of the running performance of the vehicle. 
Owing to the construction described above, the engine-associated 
initialization inhibiting control unit 165 operates following the flow 
chart of FIG. 30. 
Namely, a detection signal from the engine revolution number sensor 17a is 
inputted to the engine operation detection means 165B to read information 
on the revolution number of the engine (step 65A). 
Then, it is judged if the engine revolution number Ne is equal to or 
greater than a predetermined value which has been set in advance (step 
65B). If so, the engine is judged to be in operation so that an inhibition 
signal is transmitted from the initialization inhibiting means 165C to the 
initializing means 165E (step 65F). 
Where the engine revolution number is smaller than the predetermined value, 
it is judged by the starter operation detection means 165A if the starter 
22 is in operation (steps 65C,65D). If so, an inhibition signal is 
transmitted from the initialization inhibiting means 165C to the 
initializing means 165E (step 65F). 
If the engine 4 is not judged to be in operation on the other hand (the No 
route of step 65B) and the starter 22 is not judged to be in operation 
(the No route of step 65D), no initialization inhibiting signal is 
transmitted so that initialization of the throttle valve control system 
165D is executed by the initializing means 165E (step 65E). 
For the execution of initialization, it is possible to add another 
condition, for example, the condition that sitting of a driver in the 
driver's seat should be detected after the door on the side of the 
driver's seat has been opened. 
Initialization is therefore not executed while the engine or starter is in 
operation, thereby making it possible to avoid the phenomenon that the 
revolution number of the engine varies significantly although the driver 
is not operating the accelerator pedal 15. 
In the case of a vehicle in which the voltage drop due to operation of the 
starter 22 is controlled small and the motor 7 for driving the throttle 
valve 6 and the throttle valve sensor 7 and ECU 14 can be operated without 
problem, initialization may be executed while the starter is in operation. 
In this case, the starter operation detection means 165A becomes 
unnecessary. 
As has been described above, the initialization of the speed control unit 
is avoided when the engine or starter is in such a prescribed operation 
state, in other words, when the vehicle is driven. This has brought about 
the advantage that disturbance to various controls caused by the 
initialization can be prevented. 
A description will next be made of a transmission-associated initialization 
inhibiting control unit 164. As is shown in FIG. 31, the control unit 164 
is inputted with a stroke of the accelerator pedal 15 via the accelerator 
pedal position sensor (APS) 15A and also with a gear shift position of the 
transmission (A/T) 20 via the shift position detection sensor 20B. 
The control unit 164 is provided with a throttle valve control system 164C, 
an initializing means 164B and an initialization inhibiting means 164A. 
The throttle valve drive system 164C and initializing means 164B are 
constructed in substantially the same manner as the throttle valve control 
system 165D and initializing means 165E described above. 
The initialization inhibiting means 164A receives an output signal from the 
shift position detection sensor 20B of the automatic transmission 20. When 
the gear shift position is neither at the neutral position nor at the 
parking position which is such a gear shift position that the drive force 
of the engine is not transmitted to the wheels from the transmission, the 
initialization inhibiting means 164A outputs an inhibition signal to the 
initializing means 164B. 
Owing to the construction described above, the transmission-associated 
initialization inhibiting control unit 164 operates following the flow 
chart shown in FIG. 32. 
Namely, the gear shift position of the transmission 20 is detected by the 
shift position detection sensor 20B (step 64A) and is then transmitted to 
the initialization inhibiting means 164A. 
By the initialization inhibiting means 164A, it is judged if the shift 
position is at N (neutral position) or P (parking position) (step 64B). If 
the gear shift position is neither at N position nor at P position, an 
initialization inhibiting signal is outputted to the initializing means 
146B (step 64D). 
As a consequence, the initialization of the throttle valve control system 
164C is inhibited when the gear shift position is neither at N position 
nor at P position. 
When the gear shift position is at N position or at P position, no 
inhibition signal is outputted so that the initialization of the throttle 
valve control system 164C is performed by the initializing means 164B 
(step 64C). 
In the case of a manual transmission, the initialization of the throttle 
valve control system is inhibited when the gear shift position is not at 
the neutral position. The initialization is executed only at the neutral 
position. 
It is hence possible to avoid the initialization of the speed control unit 
in a running state which is not desirous due to momentary cut-off of the 
power supply or the like. This has made it possible to prevent 
initialization-induced disturbance of various controls. 
Next, a throttle valve sensor failure-time air control unit (hereinafter 
referred to as the "TV failure time, air control unit") 167 will be 
described. As is shown in FIG. 33, two intake passages 5A,5B provided in 
parallel to each other are provided with throttle valves 6A,6B, 
respectively. These throttle valves 6A,6B are driven, i.e., opened and 
closed by drive motors 7A,7B, respectively. The drive motors 7A,7B are in 
turn controlled by a throttle valve drive means 167B. 
Incidentally, the intake passages 5A,5B are connected at their downstream 
sides to respective banks of a V6 engine. A communication valve 61 is 
arranged between downstream portions of the intake passages 5A,5B so that 
the intake passages 5A and 5B are communicated with each other when the 
communication valve 61 is opened. 
The communication valve 61 is closed while the throttle valves 6A,6B are 
normal but is opened if any one of the throttle valves 6A,6B fails and 
closes up fully. 
The throttle valve drive means 167B is designed to output a drive signal so 
that the throttle valves 6A,6B can be opened or closed to a target opening 
rate outputted from a target opening rate setting means 167A. 
The target opening rate setting means 167A is formed by one of the other 
control units 151-168, said one control unit being capable of outputting a 
target throttle opening rate. 
A controller is also provided as a failure detection means 167C. Failure of 
the motor 7A(7B) or throttle position sensor 8A(SB) is detected in the 
form of an abnormal output or the absence of any change in output for a 
predetermined time or longer, and a failure signal is then outputted to a 
converter means 167E and also to a failure-time air control means 167D. 
The failure-time air control means 167D is provided with switches 23,24. 
Upon reception of a failure signal, these switches 23,24 are changed over 
so that the throttle valve 6A and motor 7A are switched from the target 
opening rate control to target air control. 
Namely, the converter means 167E is equipped with a map which can correlate 
each throttle opening rate to an air volume per revolution of the engine 
A/N. By the converter means 167E, a target throttle opening rate is 
therefore converted to a target air volume while using the engine 
revolution number as a parameter. 
The target air volume so converted is then inputted to the air control 
means 167D. To give the target air volume, the motor 7A is driven to open 
or close the throttle valve 6A. 
The opening or closure of the throttle valve 6A is feedback controlled by 
using an output signal from the intake air sensor 3. 
The air flow sensor 3 as an intake air sensor is arranged on an upstream 
side of the intake passage 5, which is before the intake passage 5 is 
bifurcated into the intake passage portion 5A and the intake passage 
portion 5B (for example, within an air cleaner), so that the intake air 
volume can still be measured even if any one of the intake passage 
portions 5A and 5B becomes no longer usable. 
Owing to the construction described above, the TV failure time, air control 
unit 167 operates following the flow chart shown in FIG. 34. 
If any one of the throttle valve sensors 8A,8B fails, control is conducted 
by the other unfailed sensor 8A(8B) so that both the throttle valves 6A,6B 
are driven over the same angle or only one 6A(6B) of the throttle valves 
is driven. 
If both the throttle valve sensors 8A, SB are found to have failed by the 
failure detection means 167C (step 67C), the current to the motor 7B which 
serves to drive the throttle valve 6B on one side is cut off and the 
throttle valve 6B is driven to the full close position by a return spring 
attached to the throttle valve 6B (step 67B). 
A failure signal is then outputted from the failure detection means 167C to 
the converter means 167E and also to the failure-time air control means 
167D. This changes over the switches 23,24 so that the control system for 
the throttle valve 6A is switched to the system which runs through the 
converter means 167E and the failure-time air control means 167D (step 
67C)&gt; 
By the converter means 167E, a target throttle opening rate is converted to 
a target air volume per revolution of the engine A/N while using as a 
parameter the engine revolution number Ne detected by the engine 
revolution number sensor 17a (step 67D). 
The air control means 167D performs feedback control corresponding to the 
deviation of an air quantity actually measured by the intake air sensor 
(air flow sensor) 3 from the target air volume, whereby the motor 7A is 
driven to a desired extent in order to drive the throttle valve 6A toward 
the target air volume (step 67E). 
In this case, the communication valve 61 should be kept open. owing to 
this, even if the throttle valve 6B is fully closed, intake air can still 
be fed to the other bank through the throttle valve 6A and the 
communication valve 61. 
In place of the control means described above, control can also be 
performed in the following manner. 
If both the throttle valve sensors 8A,8B have failed, the throttle valves 
6A,6B are first driven to full closed position. Similarly to the procedure 
described above, switching to the air control mans 167D is performed. To 
achieve a target air volume, the motors 7A,7B are then driven to the same 
extent so that the throttle valves 6A,6B are opened to the same rate. 
Then, using air volume information actually measured by the air flow sensor 
3, the throttle valves 6A,6B are feedback controlled based on the air 
volume. In this case, the communication valve 61 can be kept closed. 
By such a control means, compensation at the time of failure of the 
throttle valve sensor(s) can be effected in substantially the same manner 
as the means described above. 
Even when both the throttle valve sensors 8A and 8B have failed, control of 
the throttle valves 6A,6B can still be precisely continued as described 
above. 
A description will next be made of an output torque adjusting revolution 
number control unit (hereinafter referred to as the "OTA revolution number 
control unit) 159. As is illustrated in FIG. 39, a target revolution 
number setting means 159A which serves to set a target revolution number 
is provided in order to perform control of the revolution number of the 
engine (especially during idling). Also provided is the engine revolution 
number sensor 17a as a revolution number detection means for detection the 
revolution number Ne of the engine. 
An output from the engine revolution number sensor 17a and another output 
from the target revolution number setting means 159A are both inputted to 
a revolution number deviation detection means 159B formed of a subtractor. 
An output from the means 159B is inputted to an engine output torque 
computing unit 159C. 
The engine output torque computing unit 159C is designed to compute an 
output torque required to achieve a target revolution number. It is 
designed to add a correction torque for the elimination of the deviation 
.DELTA.Ne in revolution number, said correction torque having been 
determined by PID from the proportional, integral and differential 
elements of the deviation .DELTA.Ne in revolution number, with an air 
conditioner load, a headlight load, an AT (automatic transmission) load 
and other loads by power steering and the like. 
The air conditioner load, headlight load, AT load and other loads have been 
stored beforehand in ROM in terms of torques required therefor. When one 
or all of their actuation switches 25,26,27,28 are turned on, the torques 
required for the turned-on loads are read and added, and the overall 
torque of the required torques so turned on and the correction torque for 
the elimination of the deviation in revolution number are outputted 
together as a target engine output torque. 
An A/N converter unit 159D with a map of correlation map between engine 
torque and A/N is also provided. The target engine output torque is 
inputted to the converter unit 159D so that its corresponding target A/N 
is outputted. 
The target A/N is inputted to a feedback control unit 159E. This feedback 
control unit 159E feedbacks A/N actually measured and computed based on an 
output from the air flow sensor 3. The unit 159E eliminates the deviation 
of the measured A/N from the target A/N by PID control, whereby control is 
performed to achieve the target A/N. 
Owing to the construction described above, the OTA revolution number 
control unit 159 operates following the flow chart shown in FIG. 40. 
Namely, the deviation .DELTA.Ne of an engine revolution number Ne detected 
by the revolution number detection means 17a from a target revolution 
number set by the target revolution number setting means 159A is computed 
by the revolution number deviation detection means 159B (step 59A). Next, 
a correction torque .DELTA.Te is computed based on the revolution number 
deviation .DELTA.Ne (step 59B). 
At the engine output torque computing unit 159C, load drive torques such as 
those required for air conditioner, headlights, automatic transmission and 
the like are read from the ROM and are then added to the correction torque 
.DELTA.Te. As a result, a target torque has been computed (step 59C). 
This target torque is converted to a target A/N by the A/N converter unit 
159D and is then outputted (step 59D). 
Upon the above conversion, the target A/N is obtained from the map of A/N 
and engine output torque. It can also be obtained in accordance with a 
first-degree formula like: 
EQU A/N=ate+b 
The deviation .DELTA.A/N of the measured A/N from the target A/N is 
determined (step 59E), and the throttle valve drive motor 7 is then 
controlled pursuant to .DELTA.A/N (step 59F). 
As has been described above and is also shown in FIG. 38(a), the present 
structure is not a means for feeding a deviation from a target revolution 
number back to the opening rate of an idling control valve 123 provided in 
a bypass passage 123a but, as is shown in FIG. 38(b), uses the means for 
directly controlling the intake air volume. Accordingly, even in the case 
of the throttle valve 6 whose diameter is large, no influence is given by 
the non-linearity between the area of the opening in the air flow passage 
and the drive of the actuator for the throttle valve 6. This makes it 
possible to use the large-diameter throttle valve 6 as a means for 
controlling the revolution number. 
Further, the feedback control of the intake air volume can be incorporated 
in a minor loop, so that the response of the air intake system can be 
improved and the response and stability of the revolution number control 
can also be improved. 
Since the volume of intake air is measured, it is possible to easily 
discover failure in the actuator for the throttle valve 6. 
An ignition angle/throttle valve-combined revolution number control unit 
(hereinafter referred to as the "IA/TV-combined revolution number control 
unit") 160 will next be describe. As is illustrated in FIG. 35, the 
control unit 160 is provided with a target revolution number setting means 
160A, which is adapted to set a target engine revolution number in order 
to control the revolution number of the engine (especially during idling). 
In addition, the revolution number sensor 17a is also provided as the 
revolution number detection means for detecting the revolution number Ne 
of the engine. 
An output from the revolution number sensor 17a and another output from the 
target revolution number setting means 160A are inputted to the revolution 
number deviation detection means 160B constructed of a subtractor. An 
output from the means 160B is inputted to an engine output torque 
computing unit 160C. 
The engine output torque computing unit 160C is designed to compute an 
output torque required to achieve the target revolution number. A 
correction torque for the elimination of the deviation .DELTA.Ne in 
revolution number, said correction torque having been determined by PID 
from the proportional, integral and differential elements of the deviation 
.DELTA.Ne in revolution number. To the value so computed, an air 
conditioner load, a headlight load, an AT (automatic transmission) load, 
and other loads by power steering and the like are added. 
The air conditioner load, headlight load, AT load and other loads have been 
stored beforehand in ROM in terms of torques required therefor. When one 
or all of their actuation switches 25,26,27,28 are turned on, the torques 
required for the turned-on loads are read and added, and the overall 
torque of the required torques so turned on and the correction torque for 
the elimination of the deviation in revolution number are outputted 
together as a target engine output torque. 
A valve opening rate converter means 160D is also provided. This converter 
means 160D is equipped with a correlation map 160D.sub.1 between engine 
torque and throttle opening rate. The target engine output torque is 
inputted to the converter unit 160D so that its corresponding target 
opening throttle rate is computed. 
The target throttle opening rate is inputted to a realizable opening rate 
setting means 160D.sub.2. By the means 160D.sub.2, an opening rate 
realizable by the throttle valve 6 is determined corresponding to the 
target throttle opening rate and is outputted. 
Namely, the throttle valve 6 and the motor 7 for driving the throttle valve 
6 have a prescribed degree of resolution to permit efficient control over 
the wide range from full close to full open. 
As is indicated by a dashed line in FIG. 37, it is ideal for the resolution 
characteristic to have a smooth characteristic over the entire range of 
opening rates. Even if they are constructed to have substantially smooth 
characteristic with sufficient resolution at intermediate opening rates, 
they have a stepwise characteristic in the range of small opening rates as 
shown by a solid line in the same drawing so that a limitation is imposed 
on feasible throttle opening rates. 
Therefore, using the target throttle opening rate as a demand opening rate, 
throttle opening rates feasible for the demand opening rate are stored as 
a map. A realizable throttle opening rate determined by the map is 
outputted. 
Namely, on a more open side than the inputted target throttle opening rate, 
a realizable throttle opening rate of a characteristic which is indicated 
by a solid line and is closest to the target throttle opening rate is 
determined as a realizable throttle opening rate. 
This realizable throttle opening rate is then inputted to a throttle valve 
control unit 160E, whereby the throttle valve 6 is controlled to the 
realizable throttle opening by way of the drive motor 7. 
Incidentally, an adjustment means 160F is connected to the valve opening 
rate converter unit 160D. This adjustment means 160F is equipped with a 
map 160F.sub.1 for converting a throttle opening rate to A/N, a delay 
element 160F.sub.2 with delay or the like by a surge tank taken into 
consideration, and an ignition angle determination means 160F.sub.3 having 
a correlation map between engine torque and ignition angle. 
To the map 160F.sub.1, the realizable throttle opening rate and the engine 
revolution number Ne are inputted. The realizable throttle opening rate is 
converted to an A/N corresponding to the reliable opening rate while using 
the engine revolution number Ne as a parameter. 
The delay element 160F.sub.2 is equipped with function for delaying the 
output timing of the target output torque and the A/N, which corresponds 
to the realizable opening rate, so that they can be synchronized with the 
actual engine operation timing. 
The ignition angle determination means F.sub.3 is equipped with the 
correlation between target output torques and ignition angles in the form 
of a map in which A/N is used as a parameter. From the target output 
torque and the A/N corresponding to the realizable opening rate, a target 
ignition angle is determined and outputted. 
The target ignition angle is inputted to an ignition angle adjustment means 
160G so that desired ignition angle retard control can be performed. 
Owing to the construction described above, the IA/TV-combined revolution 
number control unit 160 operates following the chart shown in FIG. 36. 
Namely, at the revolution number deviation detection means 160B, the 
deviation of the actually-measured engine output number Ne outputted from 
the revolution number detection means 17a from the target revolution 
number set by the target revolution number setting means 160A is computed 
(step 60A). 
To eliminate the speed deviation so computed, a torque correction quantity 
as a control quantity in the PID control is computed by an engine output 
torque computing unit 160C.sub.1 (step 60B). 
Next, at the engine output torque computing unit 160C, the required torques 
corresponding to the turndown switches 25,26,27,28 out of air conditioner 
load torque, headlight load torque, AT (automatic transmission) load 
torque and other load torques are added further and a target output torque 
is computed (step 60C). 
The target output torque is converted to a target throttle opening rate in 
accordance with the map 160D.sub.1 by the valve opening rate converter 
160D (step 60D). 
Upon this conversion, one of the map characteristics each of which uses an 
engine revolution number as a parameter is chosen in the light of the 
engine revolution number Ne actually measured, and the conversion is then 
conducted. 
The target throttle opening rate so computed is converted by the realizable 
opening rate setting means 160D.sub.2 to a realizable throttle opening 
rate which is closest to the target throttle opening rate on a more open 
side than the target throttle opening rate (step 60E). 
The realizable throttle opening rate is inputted to the throttle valve 
control unit 160E, by which the throttle valve 6 is driven to the 
realizable throttle opening rate (step 60H). 
In addition, the realizable throttle opening rate is converted to an air 
volume per revolution of the engine (A/N) by the map 160F.sub.1 in the 
adjustment means 160F (step 60F). 
The ignition angle is then controlled by the air volume (A/N) and the 
target engine torque from the engine output torque computing unit 160C. To 
have it synchronized with the actual engine process, the delay in filling 
the surge tank with air is correlated to the delay in the intake stroke by 
the delay element 160F.sub.2, whereby the output of the target engine 
torque and A/N to the ignition angle determination means 160F.sub.3 is 
delayed (step 60G). 
Based on the target engine torque and A/N inputted with a delay to the 
ignition angle determination means 160F.sub.3 and the map incorporated in 
the means 160F.sub.3, said A/N corresponding to the realizable opening 
rate, a more delayed retard ignition angle is determined (step 60I). This 
retard ignition angle is inputted to the ignition angle adjustment means 
160G. 
At the ignition angle adjustment means 160G, the ignition angle of the 
engine 4 is controlled to have it regarded to the ignition angle so 
determined (step 60J), whereby a surplus engine output torque expected to 
be produced due to the control of the throttle opening rate to the 
feasible throttle opening rate on the more open side than the demanded 
throttle opening rate is eliminated by the ignition angle retard and the 
engine output torque is subjected to fine adjustment. 
Incidentally, an actually measured value may be used between the steps 1 
and 2 in FIG. 36. 
As the target throttle opening rate, the target throttle opening rate of 
the map 160D can be used as it is. No substantial influence is given to 
the effects of the control even if the control is conducted in this 
manner. 
Further, the surplus engine output torque may also be adjusted by adjusting 
the air/fuel ratio toward the lean side instead of adjusting it by 
retarding the ignition angle. In this case, the above ignition angle 
determination means is replaced by an air/fuel ratio determination means 
which has as a map the relation of air/fuel ratios (A/F) to target torques 
and receives the target torque, A/N and engine revolution number. Based on 
an output from the air/fuel ratio determination means, the air/fuel ratio 
is rendered leaner. 
In this manner, precise revolution number control can also be effected by 
using the throttle valve having coarse resolution instead of providing a 
small-diameter valve for the control of idling. As a result, parts such as 
an idle control valve are obviated, leading to a reduction in the number 
of parts and also to a reduction in cost. 
A description will next be made of a control mode change-over control unit 
163. As is depicted in FIGS. 41 and 42, the control unit 163 is first 
provided with a target first throttle opening rate calculation means 
(target opening rate setting means for first throttle) 163C-1 and a second 
target throttle opening rate calculation means (target opening rate 
setting means for second throttle) 163C-1. 
The target first throttle opening rate calculation means 163C-1 outputs a 
first target opening rate signal to a throttle valve control means 
(throttle motor drive means) 163D on the basis of an output signal from 
the accelerator pedal position sensor 15A and an output signal received 
(via a processor 122) from an operation state detection means which is 
composed of plural sensors (for example, the air flow sensor 3, the engine 
revolution number sensor 17a , the gear shift position detection sensor 
20B, etc.) in order to detect the state of operation of the engine 4 or 
transmission 20 mounted on the vehicle. The target second throttle opening 
rate calculation means 163C-2 outputs, based on an output signal from the 
accelerator pedal position sensor 15A, a second target opening signal (a 
signal for the direct mode) to the throttle valve control means (throttle 
motor derive means) 163D. Namely, in the control according to the first 
target opening rate signal from the target first throttle opening rate 
calculation means 163C-1, the throttle valve 6 does not move as operated 
through the accelerator pedal 15 but moves corresponding to the engine 
torque. In the control performed under the second target opening rate 
signal from the target second throttle opening rate signal, the throttle 
valve 6 moves as operated by the accelerator pedal 15. 
Accordingly, the first target opening rate signal is called an "engine 
torque mode target opening rate signal", and control pursuant to the 
engine torque mode target opening rate signal is called a "direct mode 
target opening rate signal". 
Also provided is a failure detection means (various sensor failure 
diagnosis means) 163A for detecting failure of at least one of the various 
sensors in the operation state detection means, for example, by detecting 
the absence of any change for a predetermined time or longer or any 
abnormal value in sensor detection signals. Also provided is a change-over 
control means (throttle control mode selector means) 163B which, upon 
receipt of a failure signal from the failure detection means 163A, outputs 
a second target opening rate signal from the target second throttle 
opening rate setting means 163C-2, said second target opening rate signal 
having been obtained based solely on detection signals from the 
accelerator pedal position sensor 15A, to the throttle valve control means 
163D. 
Owing to the construction described above, the control mode change-over 
control unit 163 operates following the flow chart shown in FIG. 43. 
Based on outputs from the various sensors, the failure detection means 163A 
detects failure (step 63A). It is next judged if designated sensors (for 
example, the air flow sensor 3, engine revolution number sensor 17a and 
gear shift position detection sensor 20B, etc. described above) have 
failed (step 63B). It is then judged if the control of the engine torque 
mode should be suspended. 
If the judgment is "No", a target opening rate for the engine torque mode 
is chosen is selected (step 63C) and the throttle valve is then performed 
by the engine torque control mode while using the target opening rate as a 
final target throttle opening rate. 
If the judgment is "Yes" in step 63B, the control by the engine torque mode 
should not be continued. Thus, a target throttle opening rate for the 
direct mode is chosen by the change-over control means 163B (step 63D) to 
perform control toward this opening rate as a target. As a result, the 
throttle valve 6 is opened or closed responsive to a stroke of the 
accelerator pedal 5 under situations not affected by output signals from 
the other sensors, whereby control substantially similar to the throttle 
open/close operation of the wire link type is performed. 
Incidentally, failures which require change-over by the above-mentioned 
change-over control means 163B may be limited to failures of any of the 
air flow sensor, engine revolution number detection sensor and A/T gear 
shift position detection sensor. As an alternative, they may include 
failures of all the sensors other than the accelerator pedal position 
sensor 15A. 
Even if any one of various sensors employed in the engine torque mode 
control has failed, running by the operation of the accelerator pedal 15 
can still be conducted surely so that the steerability of the vehicle is 
not deteriorated or sudden stop does not occur by suspension of control. 
The above system can be installed by simply modifying the software alone as 
needed, so that the advantageous effects described above can be obtained 
without substantial cost increase. 
A description will next be made of a throttle valve closure forcing means 
168A for a throttle closure forcing system 168. As is depicted in FIG. 
44-46, a sectorial member (a loose-fitted lever member) 6b is pivotally 
loose fitted on a throttle shaft 6a of the throttle valve 6. This 
sectorial member 6b is linked to the brake pedal 21 via a cable 6c which 
forms a link mechanism. 
The sectorial member 6b defines a slot 6b in an arcuate outer periphery 
thereof. The cable 6c extends along the slot 6d and is secured at a free 
end thereof in a hole 6e formed in an end portion of the sectorial member 
6b. 
Further, a stopper (fixing lever member) 6f is secured on the throttle 
shaft 6a so that the stopper 6f is turned together with the sectorial 
member 6b to a predetermined position (the full close position of the 
throttle valve) as the sectorial member 6b turns. 
The throttle valve 6 is constructed such that it is driven responsive to 
desired control by the motor provided additionally. 
Namely, the throttle valve closure forcing means 168A is constructed of the 
sectorial member 6b as a loose-fitted lever member--said sectorial member 
6b being loose-fitted on the throttle shaft 6a of the throttle valve 6 and 
being turnable in association with a braking action o the brake pedal 
21--and the stopper 6f secured as a fixed lever member on the throttle 
shaft 6a of the throttle valve 6. When the sectorial member 6b is turned, 
the stopper 6f engages the sectorial member 6b so that the throttle valve 
6 is forced to close. 
Owing to the above construction, the throttle valve 6 is generally closed 
or opened as desired by the motor 7. As a result, the stopper 6f is driven 
between the full close position shown in FIG. 46(a), which is a view taken 
in the direction indicated by arrow Z in FIG. 45, and the full open 
position shown in FIG. 46(b) as the throttle valve 6 is operated. 
When the brake pedal 21 is treadled over or beyond a predetermined stroke, 
the cable 6c is pulled in the direction indicated by arrow A in FIG. 46(c) 
so that the sectorial member 6b is also driven by way of the cable 6c and 
reaches the position depicted in FIG. 46(c). 
Since the stopper 6f is driven at the same time, the throttle valve 6 
assumes the full close position. 
As has been described above, when it is desired to close the throttle valve 
6, for example, at the time of failure of at least one of the control 
means, the throttle valve 6 can be brought into the full close position by 
treadling the brake pedal 21 over a predetermined stroke. 
The relationship between the sectorial member 6a and the stopper 6f should 
be set such that the throttle valve closure forcing means 168A is not 
actuated when the brake pedal is treadled lightly but is actuated for the 
first time to reduce the throttle opening rate to zero when the brake 
pedal is treadled strongly. 
When the throttle valve 6 is controlled in a right way, the opening and 
closure of the throttle valve can be effected without any problem in a 
state as shown in FIGS. 46(a) and 46(b). 
In the structure described above, the throttle valve 6 is forced to close 
or open by way of the cable 6c connected to the brake pedal 21. The 
throttle valve 6 can also be closed or opened by a drive means which, 
instead of the cable 6c, uses a change in the brake hydraulic pressure, 
said change taking place when the brake is applied, or a change in the 
intake negative pressure. 
Closure of the throttle valve is carried out by such a means as described 
above. Whichever means is employed, the closure is not closure by way of 
an electrical control means but mechanical drive is forcedly effected. The 
electrical control system can be surely supplemented. 
In this manner, the operation of the throttle valve 6 is not restrained 
usually so that the function of the DBW control is not limited. By 
treadling the brake pedal, the throttle valve is forcedly driven and 
closed whereby the automotive vehicle can be stopped safely. Further, the 
system is a simple mechanism not associated with electrical operation so 
that the reliability is improved and the system can be installed at a low 
cost. 
In the present embodiment, each of the intake passages communicating to the 
two banks of the V6 engine is provided with the throttle valve open/close 
driven by the motor. Needless to say, the present invention can also be 
applied to a straight engine in which a single motor-driven throttle valve 
is provided in a single intake passage. To arrange a single throttle valve 
in a single intake passage, it is unnecessary to provide the TV failure 
time, air control unit 167. If an embodiment with a single intake passage 
and a single throttle valve disposed therein is described with reference 
to drawings, the description will be similar to the description of the 
foregoing embodiment. Its description is therefore omitted herein.