Throttle valve control apparatus for internal combustion engine

A vehicle engine throttle valve control apparatus whereby the actuation position of an accelerator pedal, the degree of opening of the throttle valve, and the position of the vehicle gear shift are detected. One of a plurality of different throttle valve target opening degree characteristics is then selected which corresponds to the current gear shift position, and the selected characteristic is used to set a target degree of opening for the throttle valve in accordance with the accelerator pedal position. The throttle valve is driven so as to make the actual degree of throttle opening become equal to the target value. Appropriate throttle control is thereby automatically performed each time a gear shift operation is executed, without intervention by the vehicle driver.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a throttle valve control apparatus for an 
internal combustion engine, whereby the degree of opening of the engine 
throttle valve is controlled in accordance with the accelerator pedal's 
actuation. 
2. Description of Background Information 
A conventional throttle valve control apparatus for an internal combustion 
engine uses the detection of the actuation position of the engine 
accelerator pedal to drive and the throttle valve is driven to a degree of 
opening which is in accordance with the relationship between the detected 
pedal actuation position and a predetermined throttle valve opening degree 
characteristic. An example of this device is described Japanese Patent 
Laid-open No. 60-164630. 
When a shift-up operation of a vehicle's transmission driven by an internal 
combustion engine is executed, i.e., a shift from a low gear to a higher 
gear, it is necessary to close the throttle valve by an amount 
corresponding to a lowering of the engine's speed of rotation that results 
from the shift-up operation. If this is not done, then the throttle valve 
will be in an excessively open condition following the shift operation, 
whereby the amount of pollutants in the engine exhaust gas will be 
increased. Similarly, when a shift-down operation of the transmission is 
executed, it is necessary to open the throttle valve by an amount 
corresponding to the increase of engine speed that results from the shift 
operation. If this is not done, then the throttle valve will be in an 
excessively closed condition following the shift operation, which will 
result in poor engine response. 
SUMMARY OF THE INVENTION 
It is an objective of the present invention to provide a throttle valve 
control apparatus whereby when a gear shift operation of the vehicle 
transmission is performed, increased exhaust gas pollutant emission is 
prevented and enhanced engine response is achieved, without the necessity 
for driver of the vehicle to change the accelerator pedal actuation 
position. 
With a throttle valve control apparatus for a vehicle engine according to 
the present invention, a plurality of respectively different target 
opening degree characteristics are utilized, which are respectively 
selected for use in accordance with the corresponding shift position of 
the vehicle transmission, as detected by shift position detection means. 
Each of these target opening degree characteristics represents a 
relationship between the target degrees of opening of the engine throttle 
valve and the position of the accelerator pedal's actuation. An 
appropriate characteristic (selected in accordance with the current gear 
shift position) is used to establish a target degree of opening of the 
throttle valve in accordance with the accelerator pedal actuation 
position, and the throttle valve is driven to reduce the amount of 
deviation between the actual throttle valve degree of opening (detected by 
a throttle valve opening degree sensor) and the above-mentioned target 
degree of opening. In this way, the actual throttle degree of opening is 
made equal to the target value. 
More specifically, the present invention comprises a control apparatus for 
a throttle valve disposed in an intake system of an internal combustion 
engine mounted in a vehicle, for controlling a degree of opening of the 
throttle valve; accelerator actuation detection means for producing an 
output representative of an actuation position of an accelerator pedal; 
setting means for setting a target degree of opening of the throttle valve 
in accordance with the actuation position of the accelerator pedal 
detected by the accelerator actuation detection means; throttle valve 
opening degree detection means for producing an output representative of 
an actual degree of opening of the throttle valve; drive means for driving 
the throttle valve in a direction such as to reduce an amount of deviation 
between the actual degree of opening of the throttle valve and the target 
degree of opening; and shift position detection means for detecting a 
current shift position among a plurality of gear shift positions of a 
vehicle transmission which is coupled to the internal combustion engine, 
wherein the setting means selects from a plurality of respectively 
different throttle valve target opening degree characteristics one of 
which corresponds to the detected shift position, and utilizes the 
selected characteristic for setting a target degree of opening of the 
throttle valve in accordance with the current accelerator pedal actuation 
position.

DESCRIPTION OF EMBODIMENTS 
The present invention will be described referring to FIG. 1, which shows an 
embodiment of a throttle valve control apparatus according to the present 
invention for an internal combustion engine which drives a motor vehicle. 
An accelerator pedal 1 is coupled to one end of an angle bracket 2 which 
is rotatably mounted on the floor of a vehicle by a shaft 3. A return 
spring 4 is coupled to the other end of bracket 2 and pushes the 
accelerator pedal 1 upwards to an idling position. An accelerator 
actuation position sensor 7 consisting of a potentiometer 6 is coupled to 
the shaft 3, and produces an output voltage in accordance with the 
actuation position of the accelerator pedal 1, i.e. in accordance with the 
accelerator angle. This angle is defined as the angle through which its 
shaft 3 has rotated about the axis from the idling position of the 
accelerator pedal 1. 
A throttle valve opening degree sensor 14 consists of a potentiometer 13 
which is coupled to a shaft 12a of throttle valve 12, mounted in the 
engine intake pipe 11, and which generates an output voltage in accordance 
with the degree of opening of throttle valve 12. The shaft 12a is also 
coupled to the drive shaft of a pulse motor 15. 
The sensors 7 and 14 and the motor 15 are connected to a control circuit 
17. Also connected to the control circuit 17 are a crank angle sensor 18 
which produces pulses in accordance with rotation of the engine crankshaft 
(not shown in the drawings), and a vehicle speed sensor 19 which produces 
an output that varies in accordance with vehicle speed. 
As shown in FIG. 2, the control circuit 17 contains a level converter 
circuit 21 which performs level conversion of the outputs from the 
accelerator actuation position sensor 7, the throttle valve opening degree 
sensor 14, and the vehicle speed sensor 19. Control circuit 17 also 
includes a multiplexer 22 which receives the level-converted output 
voltages from level converter circuit 21 and selects one of these to be 
produced as output, an A/D converter 23 which performs analog-digital 
conversion of the selected output voltage from multiplexer 22, a waveform 
shaping circuit 24 which performs waveform shaping of the output signal 
from crank angle sensor 18, a counter 25 which counts a number of clock 
pulses that are produced from a clock pulse generating circuit (not shown 
in the drawings) during each interval between generation of successive TDC 
(Top Dead Center) signal pulses produced as output from waveform shaping 
circuit 24, a drive circuit 26 which drives the pulse motor 15, a CPU 
(Central Processing Unit) 27 which performs digital operations in 
accordance with a program, a ROM (Read-only Memory) 28 in which programs 
and data have stored, prior to operation of the throttle control 
apparatus, and a RAM (Random Access Memory) 29. The multiplexer 22, A/D 
converter 23, counter 25, drive circuit 26, CPU 27, ROM 28 and RAM 29 are 
mutually interconnected by a bus 30. CPU 27 also receives clock pulses 
from a clock pulse generating circuit (not shown in the drawings). 
The operation of the embodiment is as follows. Respective data for an 
accelerator angle .theta..sub.ACC, a throttle valve degree of opening 
.theta..sub.th, and a vehicle speed V supplied from A/D converter 23 are 
selectively transferred to the CPU 27 over the bus 30. In addition, data 
representing the engine speed of rotation N.sub.e from the counter 25 are 
supplied to CPU 27 over bus 30. CPU 27 reads the respective data in 
accordance with a processing program which is stiored in the ROM 28, with 
the reading being performed in synchronism with the clock pulses. CPU 27 
thereby performs processing as described below for generating commands 
which are supplied to the drive circuit 26 to drive the pulse motor 15. 
These commands consists of pulse motor valve-opening drive commands, pulse 
motor valve-closing drive commands, and pulse motor drive halt commands 
(whereby the driving of pulse motor 15 is halted). 
The operation of the throttle valve control apparatus according to the 
present invention will now be described with reference to the subroutine 
performed in the CPU 27 which is shown in FIG. 3. 
CPU 27 executes the following sequence of operations, at predetermined 
periodic intervals. First, the accelerator angle .theta..sub.ACC, the 
throttle valve degree of opening .theta..sub.th, the vehicle speed V, the 
engine speed of rotation N.sub.e, are respectively read. In this 
embodiment, a manually operated speed change gear (not shown in the 
drawings) having five forward speeds is utilized. Decisions are then made 
as to whether or not the speed change gear is set in each of the first 
through fifth speed positions respectively (steps 52 through 56). Each of 
these decisions as to the gear shift position is made by judging the ratio 
of vehicle speed V to the engine speed of rotation N.sub.e. The ROM 28 has 
a set of first speed to fifth speed .theta..sub.ref data maps stored in it 
beforehand, (where "data map" has the significance of a memory-mapped 
relationship between accelerator angle and degree of throttle valve 
opening). These data maps represent different accelerator angle 
.theta..sub.ACC -throttle valve target degree of opening characteristics, 
which are selected for use in accordance with the respective gear shift 
positions. For example, if the speed change gear is set to the first speed 
position, then the first speed data map is selected, and the target degree 
of opening .theta..sub.ref is determined from this data map in accordance 
with the accelerator angle .theta..sub.ACC (step 57). Similarly, the 
target degree of opening .theta..sub.ref of throttle valve 12 is 
determined for each of the first through the fifth speeds in accordance 
with the accelerator angle .theta..sub.ACC, from the corresponding 
.theta..sub.ref data map (steps 58 through 61). After obtaining the target 
degree of opening .theta..sub.ref in this way, a decision is made as to 
whether or not the throttle valve degree of opening .theta..sub.th which 
has been read is identical to the target degree of opening .theta..sub.ref 
(step 62). If .theta..sub.th =.theta..sub.ref, a pulse motor drive halt 
command is provided to the drive circuit 26 (step 63). If .theta..sub.th 
.noteq..theta..sub.ref, a decision is made as to whether or not the 
throttle valve degree of opening .theta..sub.th is greater than the target 
degree of opening .theta..sub.ref (step 64). If .theta..sub.th 
&gt;.theta..sub.ref, then a pulse motor throttle valve-closing drive command 
is provided to the drive circuit 26, to drive the throttle valve in the 
closing direction (step 65). If .theta..sub.th is not greater than 
.theta..sub.ref, i.e. .theta..sub.th &lt;.theta..sub.ref, a pulse motor 
throttle valve-opening drive command is provided to the drive circuit 26, 
to drive the throttle valve in the opening direction (step 66). 
If it is found that the speed change gear is not set to any of the five 
forward speed positions which normally indicates that the gear shift is in 
the neutral or reverse position, the target degree of opening 
.theta..sub.ref of throttle valve 12 is obtained in accordance with the 
accelerator angle .theta..sub.ACC from the first speed .theta..sub.ref 
data map, in the same way if the gear shift was found to be in the first 
speed position. 
The drive circuit 26 responds to a pulse motor valve-opening drive command 
to cause forward rotation of pulse motor 15, thereby driving the throttle 
valve 12 in the opening direction, and responds to a pulse motor 
valve-closing drive command to cause reverse rotation of pulse motor 15, 
thereby driving the throttle valve 12 in the closing direction. 
Furthermore, in response to a pulse motor drive halt command, drive 
circuit 26 acts to halt the rotation of pulse motor 15, thereby 
maintaining the current degree of throttle valve opening. 
In this way, different accelerator angle-throttle valve target degree of 
opening characteristics are selected in accordance with the position of 
the gear shift and utilized to obtain the target degree of opening 
.theta..sub.ref, and the throttle valve 12 is driven to a degree of 
opening which is identical to this target degree of opening 
.theta..sub.ref. When a shift-up operation of the gears is performed, as 
shown in FIG. 5 the engine speed of rotation N.sub.e will be lowered at a 
time t.sub.1, i.e. when clutch engagement occurs following the gear shift. 
The throttle valve is, therefore, closed by an amount which is in 
accordance with the predicted extent .DELTA.N.sub.e of this reduction of 
engine speed, by selecting a different one of the accelerator 
pedal-throttle valve target degree of opening characteristics from which a 
new target degree of opening is obtained. The appropriate amount of 
closing of the throttle valve is thereby executed without any change in 
the accelerator angle, i.e., without any change in the accelerator pedal 
actuation position. Similarly when a shift-down operation of the speed 
change gear is performed, the engine speed of rotation N.sub.e will be 
increased when the clutch is engaged after the gear shift is executed. The 
throttle valve is therefore open by an amount which corresponds to the 
predicted extent .DELTA.N.sub.e of the increase in the engine speed, again 
by selecting a different one of the accelerator pedal-throttle valve 
target degree of opening characteristics, corresponding to the new gear 
shift position, and obtaining a new value of throttle valve target degree 
of opening by utilizing that characteristic, without a change in the 
accelerator angle. The accelerator angle-throttle valve target degree of 
opening characteristic for the first speed position of the gears can be 
considered a reference characteristic, with other characteristics being 
respectively selected each time a gear shift is executed. 
In the embodiment of the present invention described above, the shift 
position of the gear is judged on the basis of the ratio between the 
vehicle speed V and engine speed of rotaion N.sub.e. However it would be 
equally possible to detect the shift positions by means such as switches 
coupled to the shift lever. 
Furthermore, with a throttle valve control apparatus according to the 
present invention as described above, a target degree of opening of the 
throttle valve is established in accordance with the accelerator pedal 
actuation position by using a target opening degree characteristic of the 
throttle valve. The target opening degree characteristic is selected in 
accordance with the current position of the vehicle transmission detected 
by shift position detection means from among a set of different target 
opening degree characteristics respectively corresponding to each of the 
gear shift positions. As a result, when a shift-down or shift-up operation 
of the transmission is executed, a target degree of opening of the 
throttle valve is immediately obtained from an appropriate target opening 
degree characteristic which corresponds to the new gear shift position. 
Thus, the throttle valve is thereby controlled to open or close by an 
amount which corresponds to the amount of change in the engine speed of 
rotation that is produced by the gear shift operation. In this way, 
increased emission of exhaust gas pollutants following a gear shift 
operation can be prevented, while improved driving response is attained. 
Furthermore in the case of an automatic transmission, the invention enables 
a reduction in the amount of impact that is produced when a shift-up 
operation is executed, by suitably controlling the throttle valve to close 
by an appropriate amount.