U.S. patent number RE32,030 [Application Number 06/416,162] was granted by the patent office on 1985-11-12 for closed loop controlled auxiliary air delivery system for internal combustion engine.
This patent grant is currently assigned to Nissan Motor Company, Limited. Invention is credited to Tsuneomi Yano, Haruo Yuzawa.
United States Patent |
RE32,030 |
Yano , et al. |
November 12, 1985 |
Closed loop controlled auxiliary air delivery system for internal
combustion engine
Abstract
An auxiliary air delivery system for an internal combustion
engine includes an intake vacuum sensor for generating an intake
vacuum signal, a deceleration sensor and a microcomputer in which
is stored a set of data representing different values of reference
intake vacuum and programmed to retrieve a datum as a function of
the length of time from the occurrence of engine deceleration. The
retrieved information is used a reference signal with which the
intake vacuum signal is compared to provide a control signal. A
servo mechanism is provided to allow auxiliary air to be admitted
into the manifold at a point downstream of the nearly closed
throttle in response to the control signal to reduce the difference
between the actual intake vacuum and the reference intake
vacuum.
Inventors: |
Yano; Tsuneomi (Tokyo,
JP), Yuzawa; Haruo (Yokohama, JP) |
Assignee: |
Nissan Motor Company, Limited
(Yokohama, JP)
|
Family
ID: |
26475074 |
Appl.
No.: |
06/416,162 |
Filed: |
September 9, 1982 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
965467 |
Nov 30, 1978 |
04240145 |
Dec 16, 1980 |
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Foreign Application Priority Data
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Dec 1, 1977 [JP] |
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52-143309 |
Dec 1, 1977 [JP] |
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52-143310 |
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Current U.S.
Class: |
701/102; 123/585;
123/327; 123/587; 701/110; 123/339.22 |
Current CPC
Class: |
F02D
31/005 (20130101); F02M 3/06 (20130101); F02D
41/0005 (20130101); F02D 41/26 (20130101); F02D
41/14 (20130101); F02D 41/12 (20130101); F02D
41/2406 (20130101); Y02T 10/42 (20130101); Y02T
10/40 (20130101) |
Current International
Class: |
F02D
41/14 (20060101); F02D 41/12 (20060101); F02D
41/00 (20060101); F02D 31/00 (20060101); F02D
41/24 (20060101); F02M 3/06 (20060101); F02M
3/00 (20060101); F02D 41/26 (20060101); G06F
007/70 (); F02M 023/06 (); F02M 023/08 () |
Field of
Search: |
;123/327,339,340,352,492,570,588,589 ;364/431.04,431.05,431.06 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2523283 |
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Jan 1976 |
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DE |
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48-21032 |
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Mar 1973 |
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JP |
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49-53118 |
|
May 1974 |
|
JP |
|
50-48024 |
|
May 1975 |
|
JP |
|
51-23435 |
|
Oct 1976 |
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JP |
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Primary Examiner: Gruber; Felix D.
Attorney, Agent or Firm: Schwartz, Jeffery, Schwaab, Mack,
Blumenthal & Evans
Claims
What is claimed is: .[.1. A method for controlling an internal
combustion engine having a main air intake passage for introducing
air into said engine, a throttle control valve in said main air
intake passage, an auxiliary air intake passage for partially
passing air from an upstream side to a downstream side of said
throttle control valve, a second control valve in said auxiliary
passage, and a vacuum pressure sensor provided downstream of said
throttle control valve, the method comprising the steps of:
detecting when the deceleration of said engine is started;
measuring the length of time from the occurrence of said
deceleration;
sensing vacuum pressure downstream of said throttle control value
with said vacuum pressure sensor;
generating a first binary signal representative of the vacuum
pressure sensed by said vacuum pressure sensor;
generating a second binary signal representative of a reference
intake vacuum pressure according to a function defining a desired
relationship between said length of time and the intake vacuum
pressure sensed by said vacuum pressure sensor;
comparing said first binary signal with said second binary signal
to generate a control signal representative of the difference
between said sensed vacuum pressure and said reference vacuum
pressure; and
controlling said second control valve in response to said control
signal to reduce the difference between said sensed vacuum pressure
and said reference vacuum pressure substantially to zero..]. .[.2.
A method as claimed in claim 1, further comprising the steps
of:
detecting the temperature of said engine;
detecting the speed of revolution of said engine;
detecting when said engine is in an idle condition;
generating in response to the detection of said idle condition a
third binary signal representative of the detected speed of said
engine;
generating a fourth binary signal representative of a reference
idle engine speed according to a function defining a desired
relationship between the detected temperature and the detected
engine speed;
comparing said third binary signal with said fourth binary signal
to generate a second control signal representative of the
difference between said detected engine speed and said reference
idle engine speed; and
controlling said second control valve in response to said second
control signal to reduce the difference between said detected
engine speed and said reference idle engine speed substantially to
zero..]. .[.3. A method as claimed in claim 2, wherein said
internal combustion engine is equipped with a vehicle air
conditioner powered by said engine, further comprising the steps
of:
detecting when a vehicle is air conditioner powered by said engine
is in operation;
generating in response to the detection of said air conditioner
being in operation a fifth binary signal representative of a second
reference idle engine speed according to a second function defining
a desired relationship between the detected engine speed and the
detected engine temperature;
comparing said third binary signal with said fifth binary signal to
generate a third control signal representative of the difference
between said second reference idle engine speed and said detected
engine speed; and
controlling said second control valve in response to said third
control signal to reduce the difference between said second
reference idle engine
speed and said detected engine speed substantially to zero..].
.[.4. A control system for use in an internal combustion engine
having a main air intake passage for introducing air to said
engine, a throttle control valve in said main intake passage and an
auxiliary air intake passage connected to said main intake passage
for partially passing air from an upstream side to a downstream
sine of the throttle control valve, comprising:
an engine deceleration detector for detecting when deceleration of
said engine is started;
means for detecting intake vacuum pressure in said main intake
passage downstream of said throttle control valve;
a programmed microcomputer, responsive to said deceleration
detector and said vacuum pressure detecting means and operative
for
detecting a difference between said detected vacuum pressure and a
reference vacuum pressure from a function defining a desired
relationship between the length of time from the occurrence of said
engine deceleration and the intake vacuum pressure in said main
intake passage at the downstream side of said throttle control
valve; and
generating a control signal representing said difference; and
means provided in said auxiliary air intake passage for controlling
the air passing therethrough in response to said control signal to
reduce said difference substantially to zero..]. .[.5. A control
system as claimed in claim 4, further comprising:
means for detecting the temperature of said engine, and
means for detecting the speed of revolution of said engine when
said engine is idled;
said programmed microcomputer being further responsive to said
temperature detecting means and said engine speed detecting means
and operative for
detecting a second difference between said detected engine speed
and a reference idle engine speed from a second function defining a
desired relationship between the detected engine temperature and
the detected engine revolution speed; and
generating a second control signal representing said second
difference;
wherein said air controlling means is further responsive to said
second control signal for controlling air passing through said
auxiliary intake passage to reduce said second difference
substantially to zero..]. .[.6. A control system as claimed in
claim 5, further comprising:
means for detecting when said engine is idled;
said programmed microcomputer being further responsive to said
engine idle detecting means and operative for
detecting a third difference between said detected engine speed and
a second reference idle engine speed which is desired when said
engine delivers power to a work load during engine idle condition
from a third function defining a desired relationship beween the
detected engine speed and the detected engine temperature; and
generating a third control signal representing said third
difference;
wherein said air controlling means is further responsive to said
third control signal for controlling air passing through said
auxiliary intake
passage to reduce said third difference substantially to zero..].
.[.7. A control system as claimed in claim 4, wherein said air
controlling means comprises:
a first control valve having a housing, a diaphragm dividing the
housing into first and second chambers, the first chamber forming
part of said auxiliary air intake passage, and a valve member
within said first chamber and connected to said diaphragm for
movement therewith to vary the cross-section of said auxiliary
passage;
means for providing fluid communication of air in said main air
intake passage from the upstream to the downstream side of said
throttle control valve through said second chamber of said first
control valve; and
a second control valve disposed in said fluid communication means
for regulating the amount of air introduced into said second
chamber of said first control valve in response to said control
signals..]. .[.8. A control system as claimed in claim 7, wherein
said controlling means further comprises a pressure regulator
disposed in said fluid communication means between a point in said
main air intake passage downstream of said throttle valve and said
second chamber of said first control valve..]. .[.9. A control
system as claimed in claims 7 or 8, wherein said second control
valve is of a pulse responsive type, said control signals
comprising pulses for controlling said second control valve..].
.[.10. A control system as claimed in claim 7 or 8, wherein said
air controlling means further comprises an orifice in which said
valve member of said first control valve is disposed, said valve
member comprising larger and smaller diameter portions and a
gradually varying diameter portion intermediate said larger and
smaller diameter portions, the cross-sectional area of said smaller
diameter portion defining a first air gap with said orifice in said
auxiliary air intake passage croresponding to engine cold start
condition and the cross-sectional area of said larger diameter
portion defining a second air gap with said orifice corresponding
to an engine idle condition which occurs at the end
of engine warm-up operation..]. .Iadd.11. A method for controlling
an air control valve disposed in an auxiliary passage which is
connected to a main intake passage of an internal combustion
engine, the auxiliary passage extending between a portion upstream
of a throttle valve disposed in the main intake passage and a
portion downstream of the throttle valve, the internal combustion
engine having means for supplying fuel thereto in response at least
to the flow of air passing through the main intake passage, said
method comprising the steps of:
detecting a vacuum within the main intake passage downstream of the
throttle valve and generating a vacuum indicative signal;
determining that the engine is under deceleration and generating an
elapsed time indicative signal indicative of time elapsed from the
start of deceleration;
determining a maximum vacuum value for said elapsed time indicative
signal and generating a maximum vacuum indicative signal, said
maximum vacuum value being variable with variation of time elapsed
from the start of deceleration;
comparing said vacuum indicative signal with said maximum vacuum
indicative signal and generating a first difference indicative
signal indicative of the difference between said vacuum indicative
signal and said maximum vacuum indicative signal;
controlling the air control valve in response to said first
difference indicative signal, to control the flow of air passing
through the auxiliary passage to control the vacuum within the main
intake passage downstream of said throttle valve so that the vacuum
within the main intake passage downstream of the throttle valve
becomes equal to said
maximum vacuum value. .Iaddend. .Iadd.12. A method for controlling
an air control valve disposed in an auxiliary passage which is
connected to a main intake passage of an internal combustion
engine, the auxiliary passage extending between a portion upstream
of a throttle valve disposed in the main intake passage and a
portion downstream of the throttle valve, the internal combustion
engine having means for supplying fuel thereto in response at least
to the flow of air passing through the main intake passage, said
method comprising the steps of:
detecting a vacuum within the main intake passage downstream of the
throttle valve and generating a vacuum indicative signal;
determining that the engine is under deceleration and generating an
elapsed time indicative signal indicative of time elapsed from the
start of deceleration;
determining a maximum vacuum value for said elapsed time indicative
signal and generating a maximum vacuum indicative signal, said
maximum vacuum value being variable with variation of time elapsed
from the start of deceleration;
comparing said vacuum indicative signal with said maximum vacuum
indicative signal and generating a first difference indicative
signal indicative of the difference between said vacuum indicative
signal and said maximum vacuum indicative signal;
detecting an engine temperature of the engine and generating a
temperature indicative signal;
determining that the engine is idling and generating an idling
indicative signal;
detecting in response to said idling indicative signal an idling
revolution speed of the engine and generating an idling revolution
speed indicative signal;
determining in response to said idling indicative signal a first
optimum idling revolution speed value for said temperature
indicative signal and generating a first optimum idling revolution
speed value indicative signal, said first optimum idling revolution
speed value being variable with a variation of the engine
temperature of the engine;
comparing said idling revolution speed indicative signal with said
first optimum revolution speed indicative signal and generating a
second difference indicative signal indicative of the difference
between said idling revolution speed indicative signal and said
first optimum idling revolution speed value indicative signal;
controlling, in response to the presence of said elapsed time
indicative signal, the air control valve in response to said first
difference indicative signal, to control the flow of air passing
through the auxiliary passage to control the vacuum within the main
intake passage downstream of said throttle valve so that the vacuum
within the main intake passage downstream of the throttle valve
becomes substantially equal to said maximum vacuum value; and
controlling, in response to the presence of said idling indicative
signal, the air control valve in response to said second difference
indicative signal to control the flow of air passing through the
auxiliary passage so that the idling revolution speed of the engine
becomes substantially equal
to said first optimum idling revolution speed value. .Iaddend.
.Iadd.13. A method for controlling an air control valve disposed in
an auxiliary passage which is connected to a main intake passage of
an internal combustion engine, the auxiliary passage extending
between a portion upstream of a throttle valve disposed in the main
intake passage and a portion downstream of the throttle valve, the
internal combustion engine having means for supplying fuel thereto
in response at least to the flow of air passing through the main
intake passage, the engine being equipped with an air conditioner
which, when in operation, becomes a load of the engine, said method
comprising the steps of:
detecting a vacuum within the main intake passage downstream of the
throttle valve and generating a vacuum indicative signal;
determining that the engine is under deceleration and generating an
elapsed time indicative signal indicative of time elapsed from the
start of deceleration;
determining a maximum vacuum value for said elapsed time indicative
signal and generating a maximum vacuum indicative signal, said
maximum vacuum value being variable with variation of time elapsed
from the start of deceleration;
comparing said vacuum indicative signal with said maximum vacuum
indicative signal and generating a first difference indicative
signal indicative of the differene between said vacuum indicative
signal and said maximum vacuum indicative signal;
detecting an engine temperature of the engine and generating a
temperature indicative signal;
determining that the engine is idling and generating an idling
indicative signal;
detecting in response to said idling indicative signal an idling
revolution speed of the engine and generating an idling revolution
speed indicative signal;
determining in response to said idling indicative signal a first
optimum idling revolution speed value for said temperature
indicative signal and generating a first optimum idling revolution
speed value indicative signal, said first optimum idling revolution
speed value being variable with a variation of the engine
temperature of the engine;
comparing said idling revolution speed indicative signal with said
first optimum revolution speed indicative signal and generating a
second difference indicative signal indicative of the difference
between said idling revolution speed indicative signal and said
first optimum idling revolution speed value indicative signal;
detecting whether the air conditioner is being operated and
generating an air conditioner operation indicative signal when the
air conditioner is being operated;
determining in response to said air conditioner operation
indicative signal a second optimum idling revolution speed value
for said temperature indicative signal and generating a second
optimum idling revolution speed value indicative signal, said
second optimum idling revolution speed value being at least higher
than said optimum idling revolution speed value;
comparing said idling revolution speed indicative signal with said
second optimum idling revolution speed value indicative signal and
generating a third difference indicative signal indicative of the
difference between said idling revolution speed indicative signal
and said second idling revolution speed value indicative
signal;
controlling, in response to the presence of said elapsed time
indicative signal, the air control valve in response to said first
difference indicative signal to control the vacuum within the main
intake passage downstream of said throttle valve so that the vacuum
within the main intake passage downstream of the throttle valve
becomes substantially equal to said maximum vacuum value;
controlling, in response to the presence of said idling indicative
signal and the absence of said air conditioner operation indicative
signal, the air control valve in response to said second difference
indicative signal to control the flow of air passing through the
auxiliary passage so that the idling revolution of the engine
become substantially equal to said first optimum idling revolution
speed value; and
controlling, in response to the presence of said idling indicative
signal and the presence of said air conditioner operation
indicative signal, the air control valve in response to said third
difference indicative signal to control the flow of air passing
through the auxiliary passage so that the idling revolution speed
of the engine becomes substantially equal to
said second optimum idling revolution speed value. .Iaddend.
.Iadd.14. A control system for controlling an air control valve
disposed in an auxiliary passage which is connected to a main
intake passage of an internal combustion engine, said auxiliary
passage extending between a portion upstream of a throttle valve
disposed in the main intake passage and a portion downstream of the
throttle valve, the internal combustion engine having means for
supplying fuel thereto in response at least to the flow of air
passing through the main intake passage, said control system
comprising:
means for detecting a vacuum within the main intake passage
downstream of the throttle valve and generating a vacuum indicative
signal;
a microcomputer including a memory which stores maximum vacuum
values for time elapsed from the start of deceleration, and a
central processor unit,
said central processor unit determining that the engine is under
deceleration and generating an elapsed time indicative signal
indicative of time elapsed from the start of deceleration,
determining one maximum vacuum value from said stored maximum
vacuum values for said elapsed time indicative signal and
generating a maximum vacuum value indicative signal, and comparing
said vacuum indicative signal with said maximum vacuum value
indicative signal and generating a first difference indicative
signal indicative of the difference between said vacuum indicative
signal and said maximum vacuum value indicative signal; and
means for controlling the air control valve in response to said
first difference indicative value to control the flow of air
passing through the auxiliary passage to control the vacuum within
the main intake passage downstream of said throttle valve so that
the vacuum within the main intake passage downstream of the
throttle valve becomes equal to said
maximum vacuum value. .Iaddend. .Iadd.15. A control system for
controlling an air control valve disposed in an auxiliary passage
which is connected to a main intake passage of an internal
combustion engine, said auxiliary passage extending between a
portion upstream of a throttle valve disposed in the main intake
passage and a portion downstream of the throttle valve, the
internal combustion engine having means for supplying fuel thereto
in response at least to the flow of air passing through the main
intake passage, said control system comprising:
means for detecting a vacuum within the main intake passage
downstream of the throttle valve and generating a vacuum indicative
signal;
a microcomputer including a memory which stores maximum vacuum
values for time elapsed from the start of deceleration, and a
central processor unit,
said central processor unit determining that the engine is under
deceleration and generating an elapsed time indicative signal
indicative of time elapsed from the start of deceleration,
determining one maximum vacuum value from said stored maximum
vacuum values for said elapsed time indicative signal and
generating a maximum vacuum value indicative signal, and comparing
said vacuum indicative signal with said maximum vacuum value
indicative signal and generating a first difference indicative
signal indicative of the difference between said vacuum indicative
signal and said maximum vacuum value indicative signal;
means for detecting an engine temperature of the engine and
generating a temperature indicative signal;
means for detecting the revolution speed of the engine and
generating an engine revolution speed indicative signal;
said memory storing optimum idling revolution speed values, each
for an engine temperature value indicated by said temperature
indicative signal;
said central processor unit determining that the engine is idling
to generate an idling indicative signal, determining one optimum
idling revolution speed from said optimum idling revolution speed
values for said temperature indicative signal to generate an
optimum idling revolution speed value indicative signal, and
comparing said engine revolution speed indicative signal with said
optimum revolution speed value indicative signal to generate a
second difference indicative signal indicative of the difference
between said engine revolution speed indicative signal and said
optimum idling revolution speed value indicative signal;
means for controlling, in response to the presence of said elapsed
time indicative signal, the air control valve in response to said
first difference indicative signal to control the flow of air
passing through the auxiliary passage to control the vacuum within
the main intake passage downstream of said throttle valve so that
the vacuum within the main intake passage downstream of the
throttle valve becomes substantially equal to said maximum vacuum
value;
said controlling means controlling, in response to the presence of
said idling indicative signal, the air control valve in response to
said second difference indicative signal to control the flow of air
passing through the auxiliary passage so that the idling revolution
speed of the engine becomes substantially equal to said first
optimum idling revolution speed
value. .Iaddend. .Iadd.16. A control system for controlling an air
control valve disposed in an auxiliary passage which is connected
to a main intake passage of an internal combustion engine, said
auxiliary passage extending between a portion upstream of a
throttle valve disposed in the main intake passage and a portion
downstream of the throttle valve, the internal combustion engine
having means for supplying fuel thereto in response at least to the
flow of air passing through the main intake passage, the engine
being equipped with an air conditioner which, when in operation,
becomes a load of the engine, said control system comprising:
means for detecting a vacuum within the main intake passage
downstream of the throttle valve and generating a vacuum indicative
signal;
a microcomputer including a memory which stores maximum vacuum
values for time elapsed from the start of deceleration, and a
central processor unit,
said central processor unit determining that the engine is under
deceleration and generating an elapsed time indicative signal
indicative of time elapsed from the start of deceleration,
determining one maximum vacuum value from said stored maximum
vacuum values for said elapsed time indicative signal and
generating a maximum vacuum value indicative signal, and comparing
said vacuum indicative signal with said maximum vacuum value
indicative signal and generating a first difference indicative
signal indicative of the difference between said vacuum indicative
signal and said maximum vacuum value indicative signal;
means for detecting an engine temperature of the engine and
generating a temperature indicative signal;
means for detecting a revolution speed of the engine and generating
an engine revolution speed indicative signal;
said memory storing first optimum idling revolution speed values,
each for an engine temperature value indicated by said temperature
indicative signal;
said central processor unit determining that the engine is idling
to generate an idling indicative signal, determining one first
optimum idling revolution speed from said first optimum idling
revolution speed values for said temperature indicative signal to
generate a first optimum idling revolution speed value indicative
signal, and comparing said engine revolution speed indicative
signal with said first optimum revolution speed value indicative
signal to generate a second difference indicative signal indicative
of the difference between said engine revolution speed indicative
signal and said first optimum idling revolution speed value
indicative signal;
said memory storing second optimum idling revolution values, each
for an engine temperature value indicated by said temperature
indicative signal;
said central processor unit determining that the air conditioner is
operated to generate an air conditioner operation indicative
signal, determining one second optimum idling revolution speed
value from said stored second optimum idling revolution speed
values for said temperature indicative signal to generate a second
optimum idling revolution speed value indicative signal, comparing
said engine revolution speed indicative signal with said second
optimum idling revolution speed value indicative signal to generate
a third difference indicative signal indicative of the difference
between said engine revolution speed indicative signal and said
second optimum idling revolution speed value indicative signal,
means for controlling, in response to the presence of said elapsed
time indicative signal, the air control valve in response to said
first difference indicative signal to control the flow of air
passing through the auxiliary passage to control the vacuum within
the main intake passage downstream of said throttle valve so that
the vacuum within the main intake passage downstream of the
throttle valve becomes substantially equal to said maximum vacuum
value;
said controlling means controlling, in response to the presence of
said idling indicative signal and the absence of said air
conditioner operation indicative signal, the air control valve in
response to said second difference indicative signal to control the
flow of air passing through the auxiliary passage so that the
idling revolution speed of the engine becomes substantially equal
to said first optimum idling revolution speed value;
said controlling means controlling, in response to the presence of
said idling indicative signal and the presence of said air
conditioner operation indicative signal, the air control valve in
response to said third difference indicative signal to control the
flow of air passing through the auxiliary passage so that the
engine revolution speed of the engine becomes substantially equal
to said second optimum idling revolution speed value. .Iaddend.
.Iadd.17. A method for controlling an air control valve disposed in
an auxiliary passage which is connected to a main intake passage of
an internal combustion engine, said auxiliary passage extending
between a portion upstream of a throttle valve disposed in the main
intake passage and a portion downstream of the throttle valve, the
internal combustion engine having means for supplying fuel thereto
in response at least to the flow of air passing through the main
intake passage, the engine being equipped with a device which, when
in operation, becomes a load of the engine, said method comprising
the steps of:
detecting a temperature of the engine and generating a temperature
indicative signal;
detecting an idling revolution speed of the engine and generating
an idling revolution speed indicative signal;
detecting whether the device is being operated and generating
device operation indicative signal when the device is being
operated;
determining in response to the absence of said device operation
indicative signal a first optimum idling revolution speed
indicative signal for said temperature indicative signal and
generating a first optimum idling revolution speed value being
variable with a variation of the temperature of the engine.
.Iaddend.
determining in response to the presence of said device operation
indicative signal a second optimum idling revolution speed value
for said temperature indicative signal and generating a second
optimum idling revolution speed value indicative signal, said
second optimum idling revolution speed value being at least higher
than said optimum idling revolution speed value and variable with a
variation of the temperature of the engine;
comparing, in response to the absence of said device operation
indicative signal, said idling revolution speed indicative signal
with said first optimum revolution speed value indicative signal
and generating a first difference indicative signal indicative of
the difference between said idling revolution speed indicative
signal and said first optimum idling revolution speed value
indicative signal;
comparing, in response to the presence of said device operation
indicative signal, said idling revolution speed indicative signal
with said second optimum idling revolution speed value indicative
signal and generating a second difference indicative signal
indicative of the difference between said idling revolution speed
indicative signal and said second optimum idling revolution speed
value indicative signal;
controlling, in response to the absence of said device operation
indicative signal, the air control valve in response to said first
difference indicative signal so that the idling revolution speed of
the engine becomes equal to said first optimum idling revolution
speed value; and
controlling, in response to the presence of said device operation
indicative signal, the air control valve in response to said second
difference indicative signal, to control the flow of air passing
through the auxiliary passage so that the idling revolution speed
of the engine becomes equal to said second optimum idling
revolution speed value.
.Iadd.8. A method for controlling an air control valve disposed in
an auxiliary passage which is connected to a main intake passage of
an internal combustion engine, said auxiliary passage extending
between a portion upstream of a throttle valve disposed in the main
intake passage and a portion downstream of the throttle valve, the
internal combustion engine having means for supplying fuel thereto
in response at least to the flow of air passing through the main
intake passage, the engine being equipped with a device which, when
in operation, becomes a load of the engine, said method comprising
the steps of:
detecting a temperature of the engine and generating a temperature
indicative signal;
detecting an idling revolution speed of the engine and generating
an idling revolution speed indicative signal;
detecting whether the device is being operated and generating a
device operation indicative signal when the device is being
operated;
determining in response to the absence of said device operation
indicative signal a first optimum idling revolution speed
indicative signal and generating a first optimum idling revolution
speed value indicative signal, said first optimum idling revolution
speed value being variable with a variation of the temperature of
the engine;
determining in response to the presence of said device operation
indicative signal a second optimum idling revolution speed value
for said temperature indicative signal and generating a second
optimum idling revolution speed value indicative signal, said
second optimum idling revolution speed value being at least higher
than said optimum idling revolution speed value and being variable
with a variation of the temperature of the engine;
comparing, in response to the absence of said device operation
indicative signal, said idling revolution speed indicative signal
with said first optimum revolution speed value indicative signal
and generating a first difference indicative signal indicative of
the difference between said idling revolution speed indicative
signal and said first optimum idling revolution speed value
indicative signal;
comparing, in response to the presence of said device operation
indicative signal, said idling revolution speed indicative signal
with said second optimum idling revolution speed value indicative
signal and generating a second difference indicative signal
indicative of the difference between said idling revolution speed
indicative signal and said second optimum idling revolution speed
value indicative signal;
controlling, in response to the absence of said device operation
indicative signal, the air control valve in response to said first
difference indicative signal to control the flow of air passing
through the auxiliary passage only when the difference indicated by
said first difference indicative signal continues to be greater
than a predetermined value for a predetermined duration of time so
that the idling revolution speed of the engine becomes equal to
said first optimum idling revolution speed value; and
controlling, in response to the presence of said device operation
indicative signal, the air control valve in response to said second
difference indicative signal, to control the flow of air passing
through the auxiliary passage only when the difference indicated by
said second difference indicative signal continues to be greater
than said predetermined value for said predetermined duration of
time so that the idling revolution speed of the engine becomes
equal to said second optimum
idling revolution speed value. .Iaddend. .Iadd.19. A method for
controlling an air control valve disposed in an auxiliary passage
which is connected to a main intake passage of an internal
combustion engine, said auxiliary passage extending between a
portion upstream of a throttle valve disposed in the main intake
passage and a portion downstream of the throttle valve, the
internal combustion engine having means for supplying fuel thereto
in response at least to the flow of air passing through the main
intake passage, the engine being equipped with an air conditioner
which, when in operation, becomes a load of the engine, said method
comprising the steps of:
detecting a temperature of the engine and generating a temperature
indicative signal;
detecting in response to said idling indicative signal an idling
revolution speed of the engine and generating an idling revolution
speed indicative signal;
detecting whether the air conditioner is being operated and
generating an air conditioner operation indicative signal when the
air conditioner is being operated;
determining in response to the absence of said air conditioner
operation indicative signal a first optimum idling revolution speed
indicative signal for said temperature indicative signal and
generating a first optimum idling revolution speed value indicative
signal, said first optimum idling revolution speed value being
variable with a variation of the temperature of the engine;
determining in response to the presence of said air conditioner
operation indicative signal and a second optimum idling revolution
speed value for said temperature indicative signal and generating a
second optimum idling revolution speed value indicative signal,
said second optimum idling revolution speed value being at least
higher than said optimum idling revolution speed value;
comparing, in response to the absence of said air conditioner
operation indicative signal, said idling revolution speed
indicative signal with said first optimum revolution speed value
indicative signal and generating a first difference indicative
signal indicative of the difference between said idling revolution
speed indicative signal and said first optimum idling revolution
speed value indicative signal;
comparing, in response to the presence of said air conditioner
operation indicative signal, said idling revolution speed
indicative signal with said second optimum idling revolution speed
value indicative signal and generating a second difference
indicative signal indicative of the difference between said idling
revolution speed indicative signal and said second optimum idling
revolution speed value indicative signal;
controlling, in response to the absence of said air conditioner
operation indicative signal, the air control valve in response to
said first difference indicative signal to control the flow of air
passing through the auxiliary passage only so that the idling
revolution speed of the engine becomes equal to said first optimum
idling revolution speed value; and
controlling, in response to the presence of said air conditioner
operation indicative signal, the air control valve in response to
said second difference indicative signal, to control the flow of
air passing through the auxiliary passage so that the idling
revolution speed of the engine becomes equal to said second optimum
idling revolution speed value.
.Iaddend. .Iadd.20. A method for controlling an air control valve
disposed in an auxiliary passage which is connected to a main
intake passage of an internal combustion engine, said auxiliary
passage extending between a portion upstream of a throttle valve
disposed in the main intake passage and a portion downstream of the
throttle valve, the internal combustion engine having means for
supplying fuel thereto in response at least to the flow of air
passing through the main intake passage, the engine being equipped
with an air conditioner which, when in operation, becomes a load of
the engine, said method comprising the steps of:
detecting a temperature of the engine and generating a temperature
indicative signal;
determining that the engine is idling and generating an idling
indicative signal;
detecting in response to said idling indicative signal an idling
revolution speed of the engine and generating an idling revolution
speed indicative signal;
detecting that the air conditioner is operated and generating a air
conditioner operation indicative signal;
determining in response to the absence of said air conditioner
operation indicative signal a first optimum idling revolution speed
indicative signal for said temperature indicative signal and
generating a first optimum idling revolution speed value indicative
signal, said first optimum idling revolution speed value being
variable with a variation of the temperature of the engine;
determining in response to the presence of said air conditioner
operation indicative signal a second optimum idling revolution
speed value for said temperature indicative signal and generating a
second optimum idling revolution speed value indicative signal,
said second optimum idling revolution speed value being at least
higher than said optimum idling revolution speed value;
comparing, in response to the absence of said air conditioner
operation indicative signal, said idling revolution speed
indicative signal with said first optimum revolution speed value
indicative signal and generating a first difference indicative
signal indicative of the difference between said idling revolution
speed indicative signal and said first optimum idling revolution
speed value indicative signal;
comparing, in response to the presence of said air conditioner
operation indicative signal, said idling revolution speed
indicative signal with said second optimum idling revolution speed
value indicative signal and generating a second difference
indicative signal indicative of the difference between said idling
revolution speed indicative signal and said second optimum idling
revolution speed value indicative signal;
controlling, in response to the absence of said air conditioner
operation indicative signal, the air control valve in response to
said first difference indicative signal only when the difference
indicated by said first difference indicative signal continues to
be greater than a predetermined value for a predetermined duration
of time to control the flow of air passing through the auxiliary
passage so that the idling revolution speed of the engine becomes
equal to said first optimum idling revolution speed value; and
controlling, in response to the presence of said air conditioner
operation indicative signal, the air control valve in response to
said second control signal only when the difference indicated by
said second difference indicative signal continues to be greater
than said predetermined value for said predetermined duration of
time to control the flow of air passing through the auxiliary
passage so that the idling revolution speed of the engine becomes
equal to said second optimum idling revolution speed value.
.Iaddend. .Iadd.21. A method for controlling an air control valve
disposed in an auxiliary passage which is connected to a main
intake passage of an internal combustion engine, said auxiliary
passage extending between a portion upstream of a throttle valve
disposed in the main intake passage and a portion downstream of the
throttle valve, the internal combustion engine having means for
supplying fuel thereto in response at least to the flow of air
passing through the main intake passage, the internal combustion
engine being drivingly connected to a transmission, the engine
being equipped with an air conditioner which, when in operation,
becomes a load of the engine, said method comprising the steps
of:
detecting a temperature of the engine and generating a temperature
indicative signal;
detecting a revolution speed of the engine and generating an engine
revolution speed indicative signal;
detecting a throttle position of a throttle valve and generating a
throttle position indicative signal when the throttle valve is
closed;
detecting a vehicle speed of the vehicle and generating a vehicle
speed indicative signal when the vehicle speed is lower than a
predetermined value;
detecting the state of the transmission and generating a neutral
state indicative signal when the transmission is in the neutral
state;
determining that the engine is idling when said throttle position
indicative signal is present and said vehicle speed indicative
signal is absent or when said throttle position indicative signal
is present and said vehicle speed indicative signal is absent and
said neutral state indicative signal is absent and generating an
idling indicative signal;
detecting that the air conditioner is operated and generating an
air conditioner operation indicative signal;
determining in response to the presence of said idling indicative
signal and the absence of said air conditioner operation indicative
signal a first optimum idling revolution speed value for said
temperature indicative signal and generating a first optimum idling
revolution speed value indicative signal, said first optimum idling
revolution speed value being variable with a variation of the
temperature of the engine.
determining in response to the presence of said idling indicative
signal and the presence of said air conditioner operation
indicative signal a second optimum idling revolution speed value
for said temperature indicative signal and generating a second
optimum idling revolution speed value indicative signal, said
second optimum idling revolution speed value being at least higher
than said first optimum idling revolution speed value and being
variable with variation of the temperature of the engine;
comparing, in response to the presence of said idling signal, and
the absence of said air conditioner operation indicative signal,
said engine revolution speed indicative signal with said first
optimum revolution speed value indicative signal and generating a
first difference indicative signal indicative of the difference
between said engine revolution speed indicative signal and said
first optimum idling revolution speed value indicative signal;
comparing, in response to the presence of said idling indicative
signal and the presence of said air conditioner operation
indicative signal, said engine revolution speed indicative signal
with said second optimum idling revolution speed value indicative
signal and generating a second difference indicative signal
indicative of the difference between said engine revolution speed
indicative signal and said second optimum idling revolution speed
value indicative signal;
controlling, in response to the absence of said idling indicative
signal and the absence of said air conditioner operation indicative
signal, the air control valve in response to said first difference
indicative signal to control the flow of air passing through the
auxiliary passage to control air fuel mixture in the main intake
passage downstream of the throttle valve so that the idling
revolution speed of the engine becomes equal to said first optimum
idling revolution speed value; and
controlling, in response to the presence of said idling indicative
signal and the presence of said air conditioner operation
indicative signal, the air control valve in response to said second
difference indicative signal, to control the flow of air passing
through the auxiliary passage to control air fuel mixture in the
main intake passage downstream of the main intake passage so that
the idling revolution speed of the engine becomes equal to said
second optimum idling revolution speed value. .Iaddend. .Iadd.22. A
control system for controlling an air control valve disposed in an
auxiliary passage which is connected to a main intake passage of an
internal combustion engine, said auxiliary passage extending
between a portion upstream of a throttle valve disposed in the main
intake passage and a portion downstream of the throttle valve, the
internal combustion engine having means for supplying fuel thereto
in response at least to the flow of air passing through the main
intake passage, the engine being equipped with an air conditioner
which, when in operation, becomes a load of the engine, the engine
being drivingly connected to a transmission, said control system
comprising:
means for detecting a temperature of the engine and generating a
temperature indicative signal;
means for detecting a revolution speed of the engine and generating
an engine revolution speed indicative signal;
means for detecting a throttle position of a throttle valve and
generating a throttle position indicative signal when the throttle
valve is closed;
means for detecting a vehicle speed of the vehicle and generating a
vehicle speed indicative signal when the vehicle speed is lower
than a predetermined value;
means for detecting a neutral state of the transmission and
generating a neutral state indicative signal when the transmission
is in the neutral state;
means for detecting that the air conditioner is operated and
generating an air conditioner operation indicative signal;
a microcomputer including a memory storing a plurality pairs of
optimum idling revolution speed values, each paid being for a
temperature value indicated by said temperature indicative signal
and comprising a first optimum idling revolution speed value and a
second optimum idling revolution speed value, said second optimum
idling revolution speed value being lower than said first optimum
idling revolution speed value;
said central process unit determining that the engine is idling
when said throttle position indicative signal is present and said
vehicle speed indicative signal is present or when the said
throttle position indicative signal is present and said neutral
state indicative signal is present to generate an idling indicative
signal, in response to the presence of said idling indicative
signal and the absence of said air conditioner operation indicative
signal determining one of said first optimum idling revolution
speed values for said temperature indicative signal to generate a
first optimum idling revolution speed value indicative signal, in
response to the presence of said idling indicative signal and the
presence of said air conditioner indicative signal determining one
of said second optimum idling revolution speed values for said
temperature indicative signal to generate a second optimum idling
revolution speed value indicative signal, said second optimum
idling revolution speed value being at least higher than said first
optimum idling revolution speed value, comparing, in response to
the presence of said air conditioner operation indicative signal
with said first optimum revolution speed value indicative signal
and generating a first difference indicative signal indicative of
the difference between said engine revolution speed indicative
signal and said first optimum idling revolution speed value
indicative signal, comparing, in response to the presence of said
idling indicative signal and the presence of said air conditioner
operation indicative signal, said engine revolution speed
indicative signal with said second optimum idling revolution speed
value indicative signal and generating a second difference
indicative signal indicative of the difference between said engine
revolution speed indicative signal and said second optimum idling
revolution speed value indicative signal; and
means for controlling, in response to the presence of said idling
indicative signal and the absence of said air conditioner operation
indicative signal, the air control valve in response to said first
difference indicative signal to control the flow of air passing
through the auxiliary passage to control air fuel mixture in the
main intake passage downtream of the throttle valve so that the
idling revolution speed of the engine becomes equal to said first
optimum idling revolution speed value, said controlling means
controlling, in response to the presence of said idling indicative
signal and the presence of said air conditioner operation
indicative signal, the air control valve, in response to said
second difference indicative signal, to control the flow of air
passing through the auxiliary passage so that the idling revolution
speed of the engine becomes equal to said second optimum idling
revolution
speed value. .Iaddend. .Iadd.23. A method for controlling an air
control valve disposed in an auxiliary passage which is connected
to a main intake passage of an internal combustion engine, said
auxiliary passage extending between a portion upstream of a
throttle valve disposed in the main intake passage and a portion
downstream of the throttle valve, the internal combustion engine
having means for supplying fuel thereto in response at least to the
flow of air passing through the main intake passage, said method
comprising the steps of:
detecting a temperature of the engine and generating a temperature
indicative signal;
detecting an idling revolution speed of the engine and generating
an idling revolution speed indicative signal;
determining an optimum idling revolution speed value for said
temperature indicative signal which is variable with a variation of
the temperature of the engine and generating an optimum idling
revolution speed value indicative signal;
comparing said idling revolution speed indicative signal with said
optimum idling revolution speed value indicative signal and
generating a first comparison result indicative signal when said
idling revolution speed indicative signal is greater than said
optimum idling revolution speed value indicative signal by a
predetermined value, a second comparison result indicative signal
when said idling revolution speed indicative signal is less than
said optimum idling revolution speed value indicative signal by
said predetermined value, and a third comparison result indicative
signal when said idling revolution speed indicative signal is not
greater than said optimum idling revolution speed value indicative
signal by said predetermined value and not less than said optimum
idling revolution speed value indicative signal by said
predetermined value;
controlling the air control valve to decrease the flow of air
passing through the main intake passage in response to said first
comparison result indicative signal thereby to decrease the idling
revolution speed of the engine;
controlling the air control valve to increase the flow of air
passing through the main intake passage in response to said second
comparison result indicative signal thereby to increase the idling
revolution speed of the engine; and
maintaining opening degree of the air control valve as it is in
response to said third comparison result indicative signal.
.Iaddend. .Iadd.24. A method for controlling an air control valve
disposed in an auxiliary passage which is connected to a main
intake passage of an internal combustion engine, said auxiliary
passage extending between a portion upstream of a throttle valve
disposed in the main intake passage and a portion downstream of the
throttle valve, the internal combustion engine having means for
supplying fuel thereto in response at least to the flow of air
passing through the main intake passage, said method comprising the
steps of:
detecting a temperature of the engine and generating a temperature
indicative signal;
detecting an idling revolution speed of the engine and generating
an idling revolution speed indicative signal;
determining an optimum idling revolution speed for said temperature
which is variable with a variation of the engine temperature of the
engine and generating an optimum idling revolution speed value
indicative signal;
computing a difference between said idling revolution speed
indicative signal and said optimum idling revolution speed value
indicative signal and generating a difference indicative
signal;
comparing said difference indicative signal with a predetermined
value and generating a first comparison result indicative signal
when said difference indicative signal is greater than said
predetermined value and a second comparison result signal when said
difference indicative signal is not greater than said predetermined
value;
controlling the air control valve in response to said difference
indicative signal when said first comparison result indicative
signal is present; and
maintaining opening degree of the air control valve as it is when
said second comparison result indicative signal is present.
.Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method and a system for
maintaining the intake vacuum of an internal combustion engine at a
predetermined reference value when the engine is decelerated.
Under decelerating condition of an internal combustion engine, air
supply to the engine is insufficient to maintain air-fuel ratio at
the stoichiometric point of the mixture, thereby resulting in the
emission of high content hydrocarbon.
Various devices have hitherto been developed to mitigate this
problem. These include throttle opener, throttle positioner and
boost controlled deceleration device (BCDD). The latter has a valve
controlled throttle bypass air passage which admits auxiliary air
into the manifold at a point downstream of the closed throttle.
For purposes of reducing the undesirable emission, it is desirable
that the intake vacuum be relatively low during the initial period
of deceleration. Conversely, during the subsequent period of
deceleration a relatively high value of intake vacuum is desirable
to operate the engine as a brake. During the later period when the
engine is idled, it is further desirable that the intake vacuum be
lower than that during the initial deceleration period. It is
impossible for the prior art devices to meet these requirements
accurately.
SUMMARY OF THE INVENTION
The invention is a closed loop electronic auxiliary air delivery
system to accurately provide auxiliary air to an internal
combustion engine in order to minimize undesirable emissions and
assure engine brake operation when the engine is decelerated.
The system of the invention comprises a microcomputer in which is
stored a set of data representing different values of reference or
optimum intake vacuum which are experimentally determined as a
function of time from the occurrence of deceleration, an intake
vacuum sensor for generating an intake vacuum signal indicative of
the actual intake vacuum and an air delivery servo mechanism. The
microcomputer is in receipt of the intake vacuum signal for
comparison with a reference signal retrieved from the stored data
to generate a control signal to which the servo mechanism is
responsive to allow auxiliary air to be admitted into the manifold
at a point downstream of the closed throttle valve to reduce the
difference between the actual intake vacuum and the reference
intake vacuum to zero.
The computer is further provided with another set of stored data
which represent reference idle engine speeds as a function of
engine temperatures. An engine speed sensor is provided to generate
an engine speed signal representative of the actual engine speed
and an engine temperature signal indicative of the actual engine
temperature. The computer is so programmed as to retrieve the
corresponding datum to compare it with the actual engine speed as a
function of the actual engine temperature to generate a second
control signal which is applied to the servo control mechanism to
reduce the difference between the actual and reference idle engine
speeds to zero.
The intake vacuum, engine speed and engine temperature signals used
in the invention may be the conventional vacuum sensor, speed and
temperature sensors embodied in an electronic fuel injection (EFT)
control system. However, it may be applied to conventional, non-EFI
equipped engines with some modifications.
The object of this invention is to provide an auxiliary air
delivery system for controlling the intake vacuum when the throttle
is nearly closed.
Another object of the invention is to provide a closed loop
controlled auxiliary air delivery system in which the intake vacuum
is controlled as a function of time when the engine is
decelerated.
A further object of the invention is to provide a closed loop
controlled auxiliary air delivery system in which the engine idle
speed is controlled as a function of the engine temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be further described in detail with reference to
the accompanying drawings, in which:
FIG. 1 is a schematic block diagram of the closed loop controlled
auxiliary air delivery system of the invention;
FIG. 2 is a graphic illustration of an operating characteristic of
the system of FIG. 1;
FIGS. 3A to 3E are flow diagrams illustrating the operating process
steps of the microcomputer of FIG. 1;
FIG. 4 is a graphic illustration of another operating
characteristic of the system of FIG. 1; and
FIG. 5 is a detailed illustration of the valve member of the servo
mechanism of FIG. 1.
DETAILED DESCRIPTION
Referring now to FIG. 1, an engine control system embodying the
invention is illustrated. A flow of air is admitted through air
cleaner 2 to the intake manifold 6 in which air flow responsive
plates 3 are provided between the air cleaner 2 and the throttle
control valve 7. The air flow plates 3 have the transverse axis
connected to the slider of an air-flow potentiometer 4 to develop a
DC voltage signal in proportion to the angular position of the
plate 3 and hence to the quantity of air taken in per unit time. A
throttle position sensing potentiometer 5 is provided having its
slider linked to the axis of the throttle valve 7 to develop a
corresponding DC voltage proportional to the opening angle of the
throttle in response to the depression of the accelerator pedal.
The voltage signals so developed at the sliders of the
potentiometers 4 and 5 are coupled to analog-to-digital converters
28 and 29, respectively, from whence the converted digital signals
are applied to the interface 23 of a microcomputer 20. The intake
passage 6 serves as a main air intake passage in cooperation with
the throttle control valve 7. Additional air is supplied to the
engine through an auxiliary air supply system comprised of an
auxiliary air passageway 10 formed outside of the main passageway 6
between points upstream and downstream of the throttle valve 7. In
the auxiliary air passageway 10 is provided a control valve 11
which includes a valve member 12 forming an orifice with a valve
seat adjacent thereto for purposes of controlling air passing
through the passage 10 to the downstream side of the throttle valve
7. The valve member 12 is connected with a diaphragm 13 supported
by a spring 14 in the valve housing to form a vacuum chamber 15
therein. To the vacuum chamber 15 is connected a vacuum supply
conduit 16 leading from a pressure regulator 17 whose inlet port is
connected to the intake passage 6 downstream from the control valve
7. Also connected to the vacuum chamber 15 of the control valve 11
is an air supply conduit 18 which leads from a pulse-operated
control valve 19. The latter has its normally closed valve member
19a which is supported by a spring 19c and operable to open in
response to a pulse supplied to solenoid 19b from the interface 23
of the microcomputer. The control valve 19 has its inlet passage
19d connected to the main intake passageway 6 upstream from the
inlet port of the auxiliary air passage 10 to supply a
predetermined amount of air to the vacuum chamber 15 of control
valve 11 via air passageway 18 in response to the opening of the
valve member 19a. Therefore, the vacuum pressure within the vacuum
chamber 15 of control valve 11 is controlled in response to the
control signal supplied from the microcomputer 20, so that the
diaphragm 13 and hence the valve member 12 is positioned to vary
the cross-section of the orifice in response to that control
signal.
Therefore, the vacuum pressure in the intake manifold 6 downstream
from the throttle valve 7 is under the control of the signal from
the computer.
A bypassport 8 and an idle adjustment screw 9 are provided in the
intake manifold 6 to serve as a bypass air supply passage during
idle condition. Fuel supply is provided by means of an injector 34
which is responsive to an output signal from the computer 20.
Although electronic fuel injection is disclosed as a means for
supplying fuel, the invention can also be applied to carburetted
engines.
The microcomputer 20 is so programmed that it controls in response
to signals supplied thereto through the interface 23 the vacuum
pressure in the intake manifold as a function of time as
illustrated in FIG. 2 when the engine is being decelerated. The
central processor unit 21 receives data stored in the memory 22 and
signals from the interface 23 and generates instructions to perform
various functional steps to derive the control signal.
For purposes of generating the control signal, the interface 23 is
in receipt of various digital signals representing engine operating
parameters in addition to the signals supplied from the A/D
converters 28 and 29. A pressure sensor 50 is provided downstream
of the throttle valve 7 to generate a vacuum pressure
representative voltage signal which is converted by an A/D
converter 51 into a corresponding digital signal. Engine coolant
temperature is detected by a temperature sensor 25 whose output
voltage signal is converted by an A/D converter 26 and supplied to
the computer 20. Engine-speed related pulses are derived from an
RPM sensor 24, and a gear position signal is generated at 30.
A deceleration detector 31 is connected to the slider of throttle
opening potentiometer 5 to provide an output in the presence of
deceleration to the interface 23. Responsive to the output from the
detector 31 the central processor 21 starts counting clock pulses
to measure the length of time from the occurrence of deceleration
to locate relevant data stored in the memory 22 required in the
processing of steps which will be described below. In the memory 22
there is stored a set of data, representing maximum allowable
intake vacuum pressures, which will be retrieved as a function of
time elapsed from the occurrence of engine deceleration (FIG. 2).
The retrieved data are compared with the data represented by the
signal from the A/D converter 51 in the processor unit 21 which
generates a control signal in the form of pulses which control the
pulse responsive valve 19 such that the vacuum pressure in the
intake manifold may not exceed the retrieved maximum value. More
specifically, the microcomputer senses the difference between the
actual and reference vacuum representative signals to generate a
control signal and reduce the difference between the actual and
reference intake vacuum pressures substantialy to zero.
After the description of the hardware construction of the engine
control system now follows the description of the software of the
microcomputer 20 with reference to flow charts shown in FIGS. 3A to
3E.
In response to the operation of the ignition key, the central
processor 21 receives data indicative of engine temperature (Tw),
engine speed (N), intake vacuum (Vc) and other data through the
interface 23 in synchronism with each revolution of the engine
crankshaft (step 100, FIG. 3A). These read-in data are temporarily
stored in the memory unit 22 and updated at each crankshaft
revolution.
For a given engine operating temperature there is an optimum open
time of the valve 19, and for a range of such temperatures a set of
corrective multiplication factors (represented in percentages in
digital values) in relation to a reference open time is stored in
the memory unit 22. Responsive to the read-in temperature data Tw,
the central processor 21 proceeds to step 101 to locate the
corresponding corrective pulsewidth multiplication factor and
retrieve it from the memory to generate a control pulse. The
processor 21 goes to step 102 to check to see if the engine starter
motor (not shown) is being energized for cranking operation. If
cranking operation is being effected, the control pulse has a
reference or standard pulsewidth P(Tw) and if it is detected that
the starter motor remains de-energized, the processor goes to the
next step 103 to check if the engine speed is above or below a set
value of 100 revolutions per minute and if the engine speed is
below that value the processor recognizes it as a condition prior
to combustion and delivers a standard control pulse P(Tw).
If the engine speed is above 100 RPM, the processor goes to step
104 to check to see if the throttle valve 7 is open or closed. If
open, the processor goes to step 128, FIG. 3D, to provide a
corrective action by adding a corrective pulsewidth .DELTA.P to the
referece pulsewidth P(Tw). When closed condition of the throttle is
detected, that is, the engine is idled or decelerated, the
processor proceeds to step 106 to check to see if the vehicle is
idled. This is detected by the presence of a signal from a vehicle
speed sensor 33 (FIG. 1) which occurs when the vehicle speed is
below 10 km/h. In the presence of idle condition, the processor
goes to step 107, FIG. 3B. If the vehicle speed is above 10 km/h,
the processor goes to step 108 to check to see if the transmission
gear shift lever is at the neutral position. If the transmission
gear is in the neutral position, the processor receives a signal
from the gear position sensor 30 and recognizes it as an idle
condition and proceeds to step 107 as referred to above. If it is
detected that the gear position is other than the neutral, the
processor recognizes it as a decelerating condition and proceeds to
step 109, FIG. 3C, to see if the engine speed is above or below a
set value of 3000 revolutions per minute. If the engine revolution
is below this set value the processor goes to step 110 to determine
whether the transmission gear is at the top gear position. If the
gear position is not at the top position, then the processor goes
to step 111 in which the engine temperature is checked to ascertain
if it is within a specified range between 15.degree. C. and
95.degree. C. and if that temperature is within the specified range
the processor goes to step 112 to locate the data stored in the
memory 22 which indicates the maximum intake vacuum Vc.sub.max as a
function of time from the start of engine deceleration. In each of
the steps 109 to 111 if the detected conditions are different from
those described above, the processor will go to step 128, FIG.
3D.
In the memory unit 22 there is stored a set of data representing
maximum intake vacuum as a function of time elapsed from the
detection of engine deceleration as depicted in FIG. 2. In step
112, the computer 20 counts the elapse of time in response to a
signal from the deceleration detector 31 and retrieves the maximum
intake vacuum value which corresponds to the counted elapsed time,
and compared the retrieved value with the actual vacuum pressure Vc
provided by the pressure sensor 50 now temporarily stored in the
memory 22 in step 113. If Vc is smaller than Vc.sub.max, a
correction pulsewidth which is equal to 1% less than a standard
correction pulsewidth .DELTA.PV is derived so that in the following
step 105 the total pulsewidth becomes P(Tw)+0.99.DELTA.PV.
Conversely, if Vc is greater than Vc.sub.max, the total pulsewidth
becomes P(Tw)+1.01.DELTA.PV. When Vc equals Vc.sub.max, the
standard correction pulsewidth of .DELTA.PV is added to the
standard pulsewidth value. Therefore, the vacuum pressure at a
point downstream of the throttle valve 7 is controlled
correspondingly with the total pulsewidth of the control signal in
a feedback loop so that the vacuum precisely follows the curve
shown in FIG. 2.
The standard pulsewidth P(Tw) may be determined so that the vacuum
pressure is optimized for idle conditions. Preferably, this
standard pulsewidth is determined based on the engine revolution at
the instant the deceleration condition is detected.
If idle condition is detected in step 106 to 108, the processor
will proceed to step 107, FIG. 3B, to check to see if the air
conditioner (not shown) is operated and if not operated a
correction pulsewidth P(C) is nullified and the processor proceeds
to step 114.
In the memory unit 22, there is stored a set of engine revolution
data (N.sub.M) which correspond to the optimum pulsewidth as a
function of coolant temperature as indicated by a solid line curve,
FIG. 4, which is determined as an optimum idle engine speed
provided that the air conditioner is not operated. Another engine
revolution data is stored in the memory unit 22 which corresponds
to the optimum pulsewidth as indicated by a chain-dot-line, FIG. 4
for idle conditions with the air conditioner being operated.
In the step 114 (FIG. 3B), the processor attempts to locate the
optimum engine revolution data in the memory and retrieve it
therefrom as a function of the detected engine temperature. If the
air conditioner is detected as being in operation in step 107, the
processor determines that the correction pulsewidth P(C)=Cl and
then proceeds to step 115 to locate the optimum engine speed data.
The correction pulsewidth data will be added to the standard
pulsewidth P(Tw) as will be described later to maintain adequate
engine speed to prevent engine from stalling and deliver additional
engine output power for operating the air conditioner.
After the optimum idle engine rpm N.sub.M has been obtained, a
comparison is made between N.sub.M and the actual engine rpm N. In
this case, if the absolute value of the difference between
N--N.sub.M is equal to or smaller than C2 (where C2 is 25 rpm, for
example), the feedback operation is disabled to provide stability
to the system. Further, the computer is so programmed that the
system does not resume feedback operation even if the absolute
value of the difference becomes greater than C2 if such condition
exists only for the duration of a single crankshaft revolution.
More specifically, the system resumes feedback operation until such
conditions subsist for a duration of C3 (five crankshaft
revolutions, for example) revolutions in order to prevent the
system from oscillating between closed and open loop control modes.
Therefore, the computer counts the occurrence of these events.
During the counting operation of the event N--N.sub.M >C2, there
is a likelihood of the occurrence of the event N.sub.M --N>C2
and if this occurs, the previous counts are cleared to initiate the
counting operation of the latter. PN1 and PN2 serve the purpose of
the counting operations.
More specifically, if the event that the engine rpm value N is
greater than the optimum value N.sub.M (25 rpm) occurs five times,
the corrective action is initiated to reduce the corrective
pulsewidth .DELTA.P by 1% of its value (where .DELTA.P is initially
at zero) with the result that the total pulsewidth is
P(Tw)+P(C)+0.99.DELTA.P is obtained so that the amount of air
supply is reduced so as to allow the engine to decrease its rpm
value. Conversely, if the event that the actual engine rpm N is
smaller than N.sub.M occurs five times, the supplied air quantity
is increased to allow the engine rpm to increase by increasing the
corrective pulsewidth .DELTA.P by 1% of its value with a total of
P(Tw)+P(C)+1.01.DELTA.P. If the absolute value of the difference
between N--N.sub.M is smaller than C2 a correction pulsewidth
.DELTA.P is provided so that a total of P(Tw)+P(C)+.DELTA.P is
generated.
Therefore, the engine rpm varies in accordance with the curves of
FIG. 4 when idled. The portion of the curve designated "C" has a
gradual rate of change as a function of temperature. This serves to
reduce the emission of harmful waste products when the engine
coolant temperature is in the neighborhood of zero degree. On the
other hand, the portion designated "D" in the characteristic curves
is to avoid the overheating of the engine due to the reduced air
supply for the purposes of reducing the emission of harmful
products. This is achieved by supplying additional air to cool the
engine.
Since the amount of air taken into the manifold is measured
upstream of the throttle control valve 7 and the fuel supply is
controlled in response to the measured air quantity, the quantity
of supplied fuel can be so controlled as to give an optimum mixture
ratio under idle conditions.
As previously described, the control signal with the standard or
basic pulsewidth P(Tw) for controlling valve 19 is generated as a
function of engine temperature when the starter motor is being
operated for cranking operation or engine rpm is below the set
value of 100 rpm (steps 102, 103, FIG. 3A). Since this basic
pulsewidth is experimentally determined and stored in the memory
unit 22 as a fixed value, the control valve 19 is directly
energized with this basic pulsewidth signal. However, if correction
pulsewidth is to be added in a manner as described in connection
with the other process steps to the basic pulsewidth, the computer
should be so programmed that the total pulsewidth must not exceed
the maximum open time of the control valve 19 if the direction of
correction is positive or must not become smaller than zero open
time if the direction of correction is negative.
Referring to FIG. 3D, in the step 105, the basic pulsewidth P(Tw)
and a correction pulsewidth .DELTA.PV for vacuum pressure are added
together. The processor now goes to check in step 120 to see if the
total pulsewidth P is equal to or smaller than the 100% value
corresponding to the maximum open time of the control valve 19. If
the total pulsewidth is greater than 100%, the memory is so
programmed that the total pulsewidth P should be set to a value
corresponding to 100%. If P is smaller than 100%, the processor
proceeds to step 121 to check whether the total pulsewidth is equal
to or greater than zero and if not, the total pulsewidth is
automatically set to a value corresponding to the zero open time.
If P is greater than zero, the total pulsewidth P(Tw)+.DELTA.PV,
which is between the maximum and minimum values of the pulsewidth,
is derived. The aforesaid steps also apply to limit the pulsewidth
P(Tw)+.DELTA.P which is generated when the throttle valve is
open.
Similarly, in FIG. 3E, the total pulsewidth P'=P(Tw)+P(C) is
checked in step 122 against the maximum value 100% and if greater
than the maximum the total pulsewidth is limited to the 100% value
in the step 123. If P' is equal to or greater than the maximum
value, the nonlimited value P' is processed in the next step 124 as
well as the value restricted in step 123 to be added up to the
correction pulsewidth .DELTA.P and compared with the maximum 100%
value. If greater than the maximum, the P'+.DELTA.P value is
limited in step 125 so that P'=100 and .DELTA.P=100--P'. If smaller
than the maximum value, the total pulsewidth P is checked in step
126 to see if it is equal to or greater than zero and if greater
than zero the processor recognizes it that the total pulsewidth
falls within the operating range of the control valve and generate
in step 127 the pulsewidth P=P(Tw)+P(C)+.DELTA.P which is delivered
to the control valve 19. If P is smaller than zero, the P value is
set to zero and .DELTA.p is set to --P.
FIG. 5 is an illustration of the detail of the control valve 11.
The valve member 12 is formed into a substantially conical shape
having a smaller diameter cylindrical portion 12a with a diameter
d.sub.1 and a larger diameter cylindrical portion 12b with a
diameter d.sub.2 and an intermediate or conical portion 12c. The
diameter d.sub.1 is so selected that the smaller diameter portion
12a defines an air gap with the orifice wall which is optimum for
cold start and the diameter d.sub.2 is so selected that it gives an
optimum air flow for idle operation at the end of engine warm-up.
The intermediate portion 12c is so designed that the rate of change
in engine revolution as a function of the rate of change in control
pulsewidth is rendered to be constant, as a result of which a
satisfactory engine rpm control is assured in the presence of a
rapid change in pulsewidth.
Because of the provision of the pressure regulator 17, the pressure
in the vacuum induction passage 16 is held at a constant vacuum
pressure regardless of the operating condition of the engine and
since this constant vacuum pressure is diluted in the control
chamber 15 by the air supplied from the pulse-operated control
valve 19, the idle control valve 11 operates with a high degree of
precision in response to the control signal from the
microcomputer.
* * * * *