Note: Descriptions are shown in the official language in which they were submitted.
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INTAKE AIR FLOW CONTROL SYSTElt~I FOR INTERNAL
COMBUSTION ENGII\fE
FIELD OF THE INVENTION
The present invention relates to an intake air flow control system for an
internal combustion engine, particularly to an intake air flow control
system for an internal combustion engine with ~Nhich it is both possible to
prevent a rise in cost and to prevent adverse effects on starting
characteristics.
BACKGROUND OF THE INVENTION
As this type of intake air flow control system for an internal combustion
engine, there has generally been known one which comprises an auxiliary
intake passage bypassing a throttle valve and provided with an intake
control valve. According to the intake air flow control system, at the time
of idling, the opening of the intake control valve is controlled, to regulate
the flow rate of auxiliary intake air flowing through the auxiliary intake
passage, whereby the engine speed can be adjusted to a target idling engine
speed.
For driving for opening and closing the intake control valve, for example,
a stepping motor is used. The valve opening at the time when the
stepping motor is adjusted to a reference position is preliminarily stored
in a memory of an electronic control unit (ECIl), and a command value
for the reference position is regulated, whereby an arbitrary valve opening
can be obtained.
In the ECU, a target valve opening of the intake control valve (in other
words, a target auxiliary intake flow rate) is determined by detecting the
engine speed or the like, and a command value to be supplied to the
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stepping motor is calculated according to the target valve opening.
However, due to secular change of the stepping motor or the like causes,
the valve opening may drift.
In order to dissolve such a drift, it is necessary to periodically perform a
reference position adjustment, namely, an adjustment in which the valve
opening on an intake valve control basis recognized by the ECU and the
actual valve opening are forcibly made to coincide with each other.
For this purpose, Japanese Patent Publication No. Sho 63-42106 proposes a
method in which immediately after an ignition switch is turned OFF, an
electric current is passed to the stepping motor to thereby move the intake
control valve to a fully closed position or a fully open position, and this
valve position is made to be a reference position for use in valve control.
On the other hand, Japanese Patent Laid-open No. Hei 6-307267 proposes a
method in which after the engine is stopped, the intake control valve is
moved to a half-open position, and this valve position is made to be a
reference position for use in valve control.
In each of the above Patent References, however, it is necessary to operate
the stepping motor when the engine is stopped, and, therefore, it is
necessary to provide a driving circuit for backing up the power source for
operating the ECU, and to provide such functions as a timer circuit for
preventing the complete discharge of the battery, i.e., the so-called
battery's-up condition. This complicates the circuit configuration and
leads to an increase in cost.
In order to obviate this problem, it may be contemplated to perform the
reference position adjustment for the intake control valve immediately
after the engine is started. In that case, however, if the fully closed
position, for example, is made to be a reference position, a bad starting (a
Iong starting time, an engine stall after starting, etc.) would arise from an
insufficient intake flow rate. On the other hand, if the fully open position
is made to be a reference position, the intake flow rate would become
excessively large, causing a disordered operation of the engine.
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The present invention has been made in consideration of the foregoing.
Accordingly, it is an object of the present invention to provide an intake
air flow control system for an internal combustion engine with which it is
possible both to prevent a rise in cost and to prevent adverse effects on
starting characteristics of the internal combustion engine.
SUMMARY OF THE INVENTION
According to the present invention, the following means have been
adopted in order to solve the above problems.
An intake air flow control system for an internal combustion engine of
the present invention is characterized in that, in an intake air flow control
system comprising an auxiliary intake passage bypassing a throttle valve
provided in a main intake passage, and an auxiliary intake air flow control
valve driven by a stepping motor so as to control an auxiliary intake flow
rate of auxiliary intake air flowing through the auxiliary intake passage,
with a reference characteristic between the valve opening of the auxiliary
intake air flow control valve and the auxiliary intake flow rate being
preliminarily stored, at the time of idling, a first re-reading condition
where the absolute value of the difference between a target idling engine
speed and a current idling engine speed is smaller than a first threshold,
and a second re-reading condition where, in regard of the auxiliary intake
flow rate for obtaining the target idling engine speed, the absolute value of
the difference between a calculated intake flow rate obtained by calculation
and a reference intake flow rate obtained based on the reference
characteristic is greater than a second threshold, are obtained, and when
both of the first re-reading condition and the second re-reading condition
are established, a re-reading step is conducted in which a valve opening
corresponding to the reference intake flow rate based on the reference
characteristic is used in place of a valve opening corresponding to the
calculated intake flow rate.
According to the intake air flow control system for an internal combustion
engine as set forth above, when the first re-reading condition is
established, it is determined that the current idling engine speed has
approached the target idling engine speed. In addition, when the second
re-reading condition is established, it is determined that the auxiliary
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intake air flow control valve has undergone a positional drift and needs a
correction. When both the first re-reading condition and the second re
reading condition are established, the valve opening corresponding to the
reference intake flow rate is adopted as correct, rather than the valve
opening corresponding to the calculated intake flow rate.
An intake valve control system for an internal combustion engine
ascending to an aspect of the present invention is characterized in that, i n
an intake valve control system for ar. internal combustion engine
including an auxiliary intake passage provided in an intake system of the
internal combustion engine so as to bypass a throttle valve, and an
auxiliary intake air flow control valve connected to a stepping motor so as
to open and close the auxiliary intake passage, a reference position of the
stepping motor is re-read when a current idling engine speed has
approached a target idling engine speed.
According to the intake valve control system for an internal combustion
engine as set forth above, the reference position of the stepping motor is
re-read when the current idling engine speed has approached the target
idling engine speed.
An intake valve control system for an internal combustion engine
according to another aspect of the invention is characterized in that, in an
intake valve control system for an internal combustion engine including
an auxiliary intake passage provided in an intake system of the internal
combustion engine so as to bypass a throttle valve, and an auxiliary intake
air flow control valve connected to a stepping motor so as to open and
close the auxiliary intake passage, the intake valve control system includes
means for determining whether or not an idling operation is currently
performed, and means for performing re-reading of a reference position of
the stepping motor when it is determined that the idling operation is
currently performed.
According to the intake valve control system for an internal combustion
engine as set forth above, the reference position of the stepping motor is
re-read when it is determined that the idling operation is currently
performed.
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BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings,
wherein:
Fig. 1 is a side view showing one embodiment of a motorcycle comprising
an intake air flew control system for an internal combustion engine
according to the present invention.
Fig. 2 is an enlarged sectional view of part A of Fig. 1, showing an essential
part of the motorcycle.
Fig. 3 is an illustration of general constitution of the intake air flow
control system in the motorcycle.
Fig. 4 is an illustration of operations of the intake air flow control system.
Fig. 5 shows tables stored in an ECU in the intake air flow control system,
in which (a) shows water temperature tables showing an air flow rate for
obtaining a predetermined engine speed at a certain water temperature,
and (b) shows reference mass flow rate tables showing the correlation
between the opening of a bypass valve and the flow rate of auxiliary intake
air flowing through the bypass valve at the opening, wherein the solid
line indicates the valve characteristic at shipping from factory, and the
broken line indicates the valve characteristic as shifted in parallel i n
relation to that at the shipping from factory.
Fig. 6 is an illustration of the flow of control by the intake air flow
control
system.
Fig. 7 is a detailed illustration of parts of the flow of control by the
intake
air flow control system, in which (a) to (c) respectively show subroutines
of steps S1 to S3 of Fig. b.
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Fig. 8 is a detailed illustration of parts of the flow of control by the
intake
air flow control system, in which (a) to (c) respectively show subroutines
of steps S4 to S6 of Fig. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the intake air flow control system for an internal
combustion engine according to the present invention will be described
below referring to the drawings, but it should naturally be noted here that
the embodiment is not construed as limitative of the invention. While
the case of applying the present invention to a motorcycle will be described
by way of example in this embodiment, the invention is naturally
applicable also to other vehicles.
As shown in Figs. 1 and 2, the motorcycle 1 in this embodiment has a
I5 motor scooter type structure in which a power unit 4 is disposed directly
under a luggage box 3 which is elongate in the front-rear direction and for
which a tandem seat type seat 2 is used also as a lid. A power unit 4
comprises an engine (internal combustion engine) 5 having a cylinder
black 6 largely inclined toward the front side, and a non-stage
transmission 8 having a rearwardly extending transmission case 10
integrally connected in relation to one side of a crankcase 9 of the engine 5.
A rear wheel (drive wheel) 11 is shaft-supported on a rear end portion of
the transmission case 10.
As shown in Fig. 2, a cylinder head 7 joined to the front end of the cylinder
block 6 is provided with an intake port 7a having its upstream ~ end
opening toward the rear side of the vehicle body, and a fuel injection
valve 7b for injecting a fuel toward the downstream end of the intake port
7a. Further, an intake air flow control system 21 for controlling the flow
rate of intake air supplied to the engine 5 is connected to the upstream end
of the intake port 7a.
As shown in Fig. 3, the intake air flow control system 21 comprises a
throttle valve 31 having a main intake passage 32a communicated to the
intake port 7a, and an idle valve 41 comprising an auxiliary intake passage
42a bypassing the throttle valve 31.
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As shown in Figs. 2 and 3, the throttle valve 31 comprises a tubular
throttle body 32 provided therein with the main intake passage 32a, a
throttle valve element 33 provided inside the throttle body 32 so as to
open and close the main intake passage 32a, and a drive force transmission
mechanism (not shown) for transmitting a drive force to the throttle
valve element 33. An air cleaner 23 is connected to the upstream end of
the throttle body 32 through an intake duct 22. On the other hand, the
downstream end of the throttle body 32 is connected to the cylinder head 7
through a connecting tube 24. In addition, a side wall of the throttle body
32 is provided with a bypass inlet 32b communicated to the main intake
passage 32a on the upstream side of the throttle valve element 33, and a
bypass outlet 32c communicated with the main intake passage 32a on the
downstream side of the throttle valve element 33.
The idle valve 41 comprises a casing 46 integrally fixed to the throttle body
32, the auxiliary intake passage 42 formed inside the casing 46 and
bypassing the throttle valve element 33 by communicating the bypass inlet
32b and the bypass outlet 32c to each other in the exterior of the throttle
body 32, a bypass valve (auxiliary intake air flow control valve) 43 for
controlling the flow rate of auxiliary intake air flowing through the
auxiliary intake passage 42, a stepping motor 44 for driving the bypass
valve 43, a power transmission portion 45 fox converting a rotational
drive force of the stepping motor 44 into an advancing and retracting
drive force for the bypass valve 43, and an electronic control unit (not
shown; hereinafter referred to as ECU) for controlling the stepping motor
44.
The casing 46 is provided with an auxiliary intake air inlet 46a
communicated to the bypass inlet 32b, an auxiliary intake air outlet 46b
communicated to the bypass outlet 32c, and a valve hole 46c which
communicates the auxiliary intake air inlet 46a and the auxiliary intake air
outlet 46b to each other and into which the bypass valve 43 is inserted.
The bypass valve 43 is roughly hollow cylindrical in shape, and comprises
a first valve hole 43a formed of the tip end thereof, and a second valve
hole 43b and a fihird valve hole 43c formed in a side wall thereof and
communicated with the first valve hole 43a. When the bypass valve 43 is
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advanced and retracted inside the valve hole 4bc, the auxiliary intake flow
rate is controlled according to the largeness of the sectional area of a
communication passage formed by overlapping of the second valve hole
43b and the third valve hole 43c with the auxiliary intake air outlet 46b.
Therefore, the auxiliary intake flow rate supplied to the engine 5 can be
controlled according to the advanced/retracted position of the bypass
valve 43 inside the valve hole 46c.
To be more specific, as shown in the left lower illustration of Fig. 4, when
the engine 5 is in a starting condition, all the opening areas of the second
valve hole 43b and the third valve hole 43c overlap with the opening area
of the auxiliary intake air outlet 46b so as to maximize the flow rate of
intake air to the engine 5. This makes it possible to maximize the opening
of the idle valve 41 (IACV opening) and to raise the engine speed (ENG
speed), as shown in the graph above the illustration.
During a warm-up operation after the starting, as shown in the central
lower illustration of Fig. 4, the third valve hole 43c and a part of the
second valve hole 43b are communicated with the auxiliary intake air
outlet 46b. This makes it possible to adjust the opening of the idle valve
41 (IACV opening) to a valve opening at the time of the warm-up
operation, as shown in the graph above the illustration.
Further, during idling after the warm-up operation, as shown in the right
lower illustration of Fig. 4, the second valve hole 43b is completely closed
and only the third valve hole 43c is communicated with the auxiliary
intake air outlet 46b. This makes it possible to adjust the opening of the
idle valve 41 (IACV opening) to a valve opening at the time of idling, as
shown in the graph above the illustration.
As shown in Fig. 3, the stepping motor 44 is fixed inside the casing 41
coaxially with the valve hole 46c, and a rotary shaft 44a thereof is formed
with a male screw 44a1. Incidentally, symbol 47 denotes a seal member,
which prevents intake air in the auxiliary intake passage 42 from leaking
from the inside of the valve hole 46c toward the outside.
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The power transmission portion 45 comprises a drive member 45a
provided with a female screw hole 45a1 screwe-engaged with the rotary
shaft 44a, and a spring 45b for fixing the drive member 45a to the bypass
valve 43. An Oldham's coupling 45c is interposed between the drive
member 45a and the bypass valve 43, so that these membeis can be
relatively displaced in the radial direction with the axes thereof as a
center.
The spring 45b is a biasing member for biasing the bypass valve 43 against
a flange portion 45a2 formed in the drive member 45a, so that the bypass
valve 43 is chatterlessly fixed onto the drive member 45a.
The above-mentioned ECU is provided for controlling the number of
steps of the stepping motor 44, and stores therein an atmospheric pressure
table for obtaining an atmospheric pressure correction factor, water
temperature tables {see Fig. 5(a); provided respectively for each of a
starting
operation mode and a running operation mode) for determining an
auxiliary intake flow rate based on the temperature of cooling water for
cooling the engine 5, a reference mass flow rate table (see the thick line i n
Fig. 5(b); the "IACV opening" on the axis of abscissas indicates the valve
opening) designating the reference characteristic between the valve
opening of the bypass valve 43 and the auxiliary intake flow rate (in other
words, the characteristic between the step position and the mass flow rate
when the stepping motor 44 is adjusted to the reference position), and a
volume flow rate table indicating the step position of the stepping motor
44 which is required for obtaining a certain volume flow rate.
The ECU can be supplied with an atmospheric pressure value measured by
an atmospheric pressure sensor (not shown) and the water temperature of
cooling water.
The flow of control by the above-described intake air flow control system
21 (hereinafter referred to as IACV) will be described referring to Figs. 6 to
8. Fig. 6 shows an outline of the control flow, and Figs. 7 and 8 show
subroutines attendant on the control flow shown in Fig. 6. In the
following description, the idling engine speed will be referred to as INE,
and the target engine speed will be referred to as target NE. Of the idling
engine speeds, the idling engine speed to be obtained now will be referred
to as this-time INE, the idling engine speed obtained one step earlier than
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this time will be referred to as last-time INE, the current idling engine
speed obtained by actual measurement will be referred to as current NE,
and the idling engine speed actually measured one step earlier than this
time will be referred to as last-time NE.
(1) Flow of Step S1
When control of IACV is started by turning the ignition ON, an
atmospheric pressure correction factor is first obtained in step Sl.
Specifically, as shown in the subroutine of Fig. 7(a), in step S1-1, the
atmospheric pressure table recorded in the ECU is referred to, and an
atmospheric pressure correction factor corresponding to the atmospheric
pressure value measured by the atmospheric pressure sensor is calculated.
After the atmospheric pressure correction factor is thus obtained, if the
current engine operation is at starting or in running, step S2 in Fig. b is
entered. On the other hand, if the current engine operation is at idling,
step S3 in Fig_ 6 is entered.
(2) Flow of Step S2
When step S2 is entered, the mass flow rate of intake air at starting or i n
running is obtained. Specifically, as shown in Fig. 7(b), if the current
engine operation is at starting, step S2-1 is entered, in which the water
temperature table for use at starting, of the water temperature tables stored
in the ECU, is referred to and a starting mass flow rate corresponding the
water temperature measured by the water temperature sensor is
calculated. On the other hand, if the current engine operation is i n
running, step S2-2 is entered, in which the water temperature table for use
in running, of the water temperature tables in the ECU, is referred to and a
running mass flow rate corresponding to the water temperature measured
by the water temperature sensor is calculated. After the mass flow rate of
intake air at starting or in running is obtained, step S3 in Fig. 6 is skipped
and step S4 in Fig. 6 is entered.
(3) Flow of Step S3
When step S3 is entered, a mass flow rate required for idling is obtained.
Specifically, as shown in Fig. 7(c), in step S3-1, an error is calculated as
the
absolute value of the difference between a current NE measured and a
target NE. In the subsequent step S3-2, a difference ONE is calculated as the
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absolute value of the difference between the current NE and a last-time
NE. Further, in the subsequent step S3-3, a PID mass flow rate is calculated
based on the error and the difference ONE obtained respectively in steps
S3-1 and S3-2. Furthermore, in the subsequent step S3-4, the PID mass
flow rate calculated in step S3-3 is added to a mass flow rate corresponding
to a last-time INE, whereby an INE mass flow rate corresponding to a this-
time INE is calculated. After the current INE mass flow rate is thus
obtained, step S4 in Fig. 6 is entered.
(4) Flow of Step S4
In step S4, a step position of the motor corresponding to the mass flow rate
at starting or in running obtained in step S2 or to the mass flow rate at
idling (INE mass flow rate) obtained in step S3 is obtained. Specifically, as
shown in Fig. 8(a), first, it is determined in step S4-1 whether the current
engine operation is at starting or not. If the current engine operation is at
starting, step S4-2 is entered, in which the mass flow rate at starting is
subjected to atmospheric pressure correction by use of the atmospheric
pressure correction factor obtained in step SI-1, whereby a volume flow
rate at starting is calculated. In the subsequent step S4-3, the volume flow
rate table recorded in the ECU is referred to, and a target step position
corresponding to the volume flow rate at starting obtained in step S4-2 is
calculated. After the target step position is thus obtained, step S5 in Fig. 6
is skipped and step S6 in Fig. 6 is entered.
On the other hand, if it is determined in step S4-1 that the current engine
operation is not at starting, step S4-4 is entered to determine whether the
current engine operation is in running or not. Then, if the current engine
running is determined as in running, step S4-5 is entered; on the other
hand, if the current engine operation is determined as not in running,
step S4-7 is entered.
When step S4-5 is entered, the mass flow rate in running is subjected to
atmospheric pressure correction by use of the atmospheric pressure
correction factor obtained in step S1-1, whereby a volume flow rate l n
running is calculated. In the subsequent step S4-6, the volume flow rate
table recorded in the ECU is referred to, and a target step position
corresponding to the volume flow rate in running obtained in step S4-5 is
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calculated. After the target step position is thus obtained, step S5 in Fig. 6
is skipped and step S6 in Fig. 6 is entered.
On the other hand, when it is determined in step S4-4 that the current
engine operation is not in running, the current engine operation is
determined as in idling and step S4-7 is entered. In step S4-7, the idling
mass flow rate (INE mass flow rate) is subjected to atmospheric pressure
correction by use of the atmospheric pressure correction factor obtained in
step S1-1, whereby an idling volume flow rate LINE volume flow rate) is
calculated. In the subsequent step S4-8, the volume flow rate table
recorded in the ECU is referred to, and a target step position corresponding
to the idling volume flow rate obtained in step 54-7 is calculated. After the
target step position is thus obtained, step S5 in Fig. & is entered.
(5) Flow of Step S5
In step S5, when both of the following first and second re-reading
conditions axe satisfied, re-reading of the reference position of the stepping
motor 44 is performed. In other words, when the current idling engine
speed has approached the target idling engine speed, re-reading of the
reference position of the stepping motor 44 is performed. (When it is
determined by the ECU, which is means for determining whether or not
the current engine operation is in idling, that the current engine operation
is in idling, re-reading of the reference position of the stepping motor 44 is
performed.)
z5
To be more specific, as shown in Fig. 8(b), first, if it is determined in-
step
S5-1 that the error (the absolute value of the difference between the target
idling engine speed and the current idling engine speed detected by a pulse
sensor) obtained in step S3-1 is smaller than a predetermined threshold
(first threshold), a first re-reading condition is regarded as established and
step S5-2 is entered. If the first re-reading condition is not established, re-
reading is not performed but step S6 in Fig. 6 is entered.
When step S5-2 is entered, the reference mass flow rate table in the ECU is
subjected to atmospheric pressure correction by use of the atmospheric
pressure correction factor obtained in step S1-1, whereby a reference
volume flow rate is calculated. In the subsequent step S5-3, the volume
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flow rate table in the ECU is referred to, and a target step position a
corresponding to the reference volume flow rate obtained in step S5-2 is
calculated. In the subsequent step S5-3a, a target step position b
corresponding to an INE volume flow rate is calculated from the volume
flow rate table.
In the subsequent step S5-4, the absolute value of the difference between
the target step position a obtained in step S5-3 and the target step position
b
obtained in step S5-3a is calculated, and when this absolute value is
determined as greater than a predetermined threshold (second threshold),
step S5-5 is entered, whereas when the absolute value is determined as
smaller than the predetermined threshold (second threshold), step S6 l n
Fig. 6 is entered. That is, in step S5-4, in regard of the auxiliary intake
flow
rate for obtaining the target idling engine speed, when the absolute value
of the difference between the calculated intake flow rate obtained by
calculation and the reference intake flow rate obtained based on the
reference mass flow rate table (reference characteristic) is greater than the
second threshold value, the second re-reading condition is regarded as
established and step S6 is entered.
When step S5-5 is entered, the target step position obtained in step S5-3a is
re-read as the target step position obtained in step S5-3.
Specifically, the target step position b (the valve opening corresponding to
the calculated intake flow rate) obtained by calculation is re-read as the
reference step position a (the valve opening corresponding to~ the
reference intake flow rate on a reference characteristic basis) obtained based
on the reference mass flow rate table. To be more specific, as shown in Fig.
5(b), when the IACV opening is shifted in parallel from a valve
characteristic at shipping from factory indicated by the solid line to a valve
characteristic indicated by the broken line due to secular change or the like,
in regard of the IACV opening (step position) for obtaining the same air
flow rate, the IACV opening obtained from the valve characteristic at
shipping from factory is adopted in place of the IACV opening obtained by
calculation. For example, in the example shown, while the IACV opening
obtained by calculation is ST2, this IACV opening is replaced with ST1,
before being read. This makes it possible to correct a valve characteristic
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drift, if any, on a software basis. After the re-reading of the target step
position is thus performed, step S6 in Fig. 6 is entered.
(6) Flow of Step S6
In step S~6, the stepping motor 44 is driven to the step position according to
the target step position obtained. Specifically, as shown in Fig. 8(c), in
step
S6-1, the target step position obtained in any one of steps S4-3, S4-6, and S4
8 or the target step value re-read in step S5-5 is referred to, and the
stepping motor 44 is rotated accordingly, whereby a target valve opening is
obtained {namely, a target auxiliary intake flow rate is secured).
As has been described above, according to the intake air flow control
system 21 in this embodiment, when it is determined that the current
idling engine speed has approached the target idling engine speed and that
the bypass valve 43 has come to have a positional drift and needs a
reference position adjustment, the re-reading is performed in which the
valve opening corresponding to the reference intake flow rate is adopted
as correct, rather than the valve opening corresponding to the calculated
intake flow rate.
According to this configuration, since the reference position adjustment is
not conducted when the engine 5 is stopped, it is unnecessary to provide a
drive circuit for backing up the operating power source when the engine 5
is stopped and it is unnecessary to provide a timer circuit or the like for
preventing a battery's-up condition. This makes it possible to prevent a
complication of circuit configuration and, hence, a rise V in cost. In
addition, since it is unnecessary to forcibly bring the bypass valve 43 to a
fully closed condition or a fully open condition at the time of the reference
position adjustment, it is possible to prevent a bad starting or an abrupt
vehicle motion.
Therefore, it is possible both to prevent a rise in cost and to prevent
adverse effects on the starting characteristics.
According to the intake air flow control system for an internal combustion
engine of the present invention, at the time of performing a reference
position adjustment of the auxiliary intake air flow control valve, when
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the first re-reading condition where the absolute value of the difference
between the target idling engine speed and the current idling engine speed
is smaller than the first threshold and the second re-reading condition
where the absolute value of the difference between the calculated intake
flow rate and the reference intake flow rate is greater than fhe second
threshold are established, the re-reading step is performed in which the
valve opening position corresponding to the reference intake flow rate on
a reference characteristic basis is used in place of the valve opening
corresponding to the calculated intake flow rate.
According to this configuration, since the reference position adjustment is
not conducted when the internal combustion engine is stopped, it is
unnecessary to provide a drive circuit for backing up the operating power
source when the internal combustion engine is stopped, and it is
15 unnecessary to provide a timer circuit or the like for preventing a
battery's-up condition. This makes it possible to prevent a complication of
circuit configuration and, hence, a rise in cost. In addition, since it is
unnecessary to forcibly bring the auxiliary intake air flow control valve to
a fully closed condition or a fully open condition at the time of performing
20 the reference position adjustment, it is possible also to prevent a bad
starting.
Thus, according to the present invention, it is possible both to prevent a
rise in cost and to prevent adverse effects on the starting characteristics.
According to a preferred embodiment of the intake valve control system
for an internal combustion engine of the present invention, it is possible
to obtain the same effects as those of the intake air flow control system for
an internal combustion engine as set forth above.
Although various preferred embodiments of the present invention have
been described herein in detail, it will be appreciated by those skilled in
the
art, that variations rnay be made thereto without departing from the spirit
of the invention or the scope of the appended claims.
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