U.S. patent number RE34,234 [Application Number 07/808,812] was granted by the patent office on 1993-04-27 for control apparatus for internal combustion engines.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Hiroshi Kuroiwa, Toshiharu Nogi, Yoshishige Oyama.
United States Patent |
RE34,234 |
Kuroiwa , et al. |
April 27, 1993 |
Control apparatus for internal combustion engines
Abstract
An internal combustion engine control apparatus has a digital
arithmetic unit to which signals are inputted from a plurality of
detectors such as detectors for detecting an operational state of
the engine and air fuel ratio detector and controls a fuel air
ratio and ignition timing according to output signals from the
arithmetic unit. The apparatus comprises by a misfire detector for
detecting a misfiring state of the engine, NOx concentration
detector and a controller for controlling the fuel air ratio and
the ignition timing so as to fall within a tolerable stable
combustion range defined by a detected misfire boundary and a
detected NOx limit. The misfiring state and/or NOx concentration
can be detected through detection of temperature change in the
combustion chamber by a detector. The detector comprises a black
body disposed in the combustion chamber and a fused silica cable
mounting the black body.
Inventors: |
Kuroiwa; Hiroshi (Hitachi,
JP), Oyama; Yoshishige (Katsuta, JP), Nogi;
Toshiharu (Hitachi, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
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Family
ID: |
26437352 |
Appl.
No.: |
07/808,812 |
Filed: |
December 17, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
184076 |
Apr 20, 1988 |
04887574 |
Dec 19, 1989 |
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Foreign Application Priority Data
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Apr 21, 1987 [JP] |
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62-96123 |
Jun 3, 1987 [JP] |
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62-138071 |
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Current U.S.
Class: |
123/406.27;
73/114.09; 123/435; 123/494; 123/406.28 |
Current CPC
Class: |
F02D
35/022 (20130101); G01M 15/108 (20130101); G01M
15/048 (20130101); F02P 5/045 (20130101); F02D
41/1451 (20130101); F02P 5/152 (20130101); G01M
15/10 (20130101); F02D 35/025 (20130101); Y02T
10/40 (20130101) |
Current International
Class: |
F02D
41/14 (20060101); F02D 35/02 (20060101); F02P
5/152 (20060101); G01M 15/10 (20060101); G01M
15/04 (20060101); F02P 005/10 (); G01L 023/22 ();
G01M 015/00 () |
Field of
Search: |
;123/419,425,435,436,494,479,630 ;73/35R,35K,35O,116,119R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3410067 |
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Sep 1985 |
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DE |
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186040 |
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Nov 1982 |
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JP |
|
13137 |
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Jan 1983 |
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JP |
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162329 |
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Sep 1984 |
|
JP |
|
17239 |
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Jan 1985 |
|
JP |
|
56150 |
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Apr 1985 |
|
JP |
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Primary Examiner: Wolfe; Willis R.
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus
Claims
What is claimed is:
1. A lean-burn control apparatus, having a digital arithmetic unit
to which signals are inputted from a plurality of detectors for
detecting an operational state of an internal combustion engine and
an air fuel ratio detector, and controlling a fuel air ratio and
ignition timing according to output signals from said arithmetic
unit, characterized by
misfire detecting means for detecting a misfiring state of said
engine;
means for detecting NOx concentration information of said engine;
and
means for controlling said fuel air ratio and said ignition timing
so as to fall within a tolerable stable combustion range which is
defined based on signals from misfire detector and said NOx
concentration information detector, and in which combustion is
stable and produces NOx of a tolerable concentration.
2. A lean-burn control apparatus according to claim 1, wherein said
misfire detecting means is a detector for measuring the intensity
of the combustion light of said engine, and said NOx concentration
detecting means is a detector for measuring the intensity of said
combustion light of said engine having a specific wavelength.
3. A lean-burn control apparatus according to claim 1, wherein said
misfire detecting means and said NOx concentration detecting means
are detectors for converting said combustion light of said engine
into a temperature.
4. A lean-burn control apparatus according to claim 1, wherein said
misfire detecting means and NOx concentration detecting means are a
temperature detector comprising an optical transmission element,
and a black body disposed in a combustion chamber of said engine
and mounted on said optical transmission element.
5. A lean-burn control apparatus according to claim 4, wherein said
transmission element is of quartz, said black body is a thin film
adhered to an end portion of said optical transmission element so
as to cover said end portion and made of one element selected from
a group consisting of iridium, platinum, zirconium nitride and
graphite.
6. A combustion control apparatus for an internal combustion engine
having a plurality of cylinders and means for generating a timing
signal relating to the timing of firing of combustion in said
cylinders, comprising:
a plurality of combustion flame optical sensors, each associated
with a respective cylinder, for detecting firing of combustion in
said cylinders;
a plurality of optical fiber cables, each connected to a respective
one of said combustion flame optical sensors;
an optical signal processing circuit connected to all of said
optical fiber cables to produce an output signal having a series of
pulses each corresponding to an optical signal of a respective
optical sensor;
detecting means responsive to said timing signal and said output
signal of said optical signal processing unit for detecting a
condition of combustion in said cylinders on the basis of said
series of pulses; and
means for controlling at least one of fuel air ratio and ignition
timing in said internal combustion engine using detected conditions
of combustion in said cylinders.
7. A combustion control apparatus according to claim 6, wherein
said controlling means operates to control both fuel air ratio and
ignition timing.
8. A combustion control apparatus for an internal combustion engine
having a plurality of cylinders, comprising:
a combustion flame optical sensor, associated with a cylinder for
detecting firing combustion in said cylinder, said optical sensor
having a non-linear characteristic;
optical signal processing means connected to said optical sensor
for converting an optical output thereof to an electrical signal
output;
linear processing means connected to said optical signal processing
means for linearizing said electrical signal output thereof;
and
means for controlling at least one of fuel air ratio and ignition
timing in said internal combustion engine using an output of said
linear processing means.
9. A combustion control apparatus according to claim 8, wherein
filter means is connected to said linear processing means for
filtering said linearized electrical signal.
10. A combustion control apparatus according to claim 8, wherein
said controlling means operates to control both fuel air ratio and
ignition timing.
11. A method of controlling fuel air ratio and ignition timing in
an internal combustion engine so as to maintain values of fuel air
ratio and ignition timing within a target range in which combustion
is stable and NOx concentration is tolerable, comprising the steps
of:
(a) detecting a misfiring state of said engine;
(b) detecting NOx concentration information of said engine; and
(c) adjusting the value of at least one of fuel air ratio and
ignition timing so that both fuel air ratio and ignition timing
fall within a target range defined by a misfire boundary and a
predetermined NOx concentration boundary.
12. A method according to claim 11, wherein said step (c) comprises
adjusting the value of both said fuel air ratio and said ignition
timing to cause both fuel air ratio and ignition timing to fall
within said target range.
13. A method according to claim 11, wherein step (a) comprises
measuring the intensity of combustion light in a cylinder of the
engine, and step (b) comprises measuring the intensity of a
specific wavelength of combustion light. .Iadd.
14. A method of detecting misfire of an internal combustion engine,
comprising the steps of:
detecting combustion light intensity in respective combustion
chambers of the engine;
converting the detected combustion light intensity of a combustion
chamber into an electrical signal corresponding to a measure of the
detected combustion light intensity;
comparing the level of said electrical signal with a predetermined
slice level; and
detecting misfire when a signal level of the electrical signal is
less than the slice level. .Iaddend. .Iadd.15. A method of
detecting misfire of an internal combustion engine, according to
claim 14, and further comprising the steps of counting a number of
times of the misfire occurring for a prescribed number of power
cycles;
calculating an average number of times of the misfire in one power
cycle; and
comparing the average number of times of misfire with a
predetermined value to judge that the engine is in a misfire
condition when the average number of times is larger than the
predetermined value. .Iaddend. .Iadd.16. A method of detecting
misfire of an internal combustion engine, comprising the steps
of:
detecting combustion temperature in respective cylinders of the
engine;
converting the detected combustion temperature of a cylinder into
an electrical signal corresponding to a measure of the detected
combustion temperature;
comparing the electrical signal with a predetermined level; and
judging a misfire condition of the engine when the electrical
signal is
less than the predetermined level. .Iaddend. .Iadd.17. A method
according to claim 16, wherein judgement of the misfire is effected
at each power cycle. .Iaddend. .Iadd.18. A method according to
claim 16, and further comprising the steps of:
counting misfire signals each of which is an electrical signal
having a level which is less than said predetermined level and is
outputted for a prescribed number of power cycles;
calculating an average number of times of occurrence of the misfire
signal;
comparing the calculated average number of times with a
predetermined value; and
judging a misfire condition of the engine when the calculated
average number of times is larger than the prescribed value.
.Iaddend. .Iadd.19. A method of detecting a condition of operation
of an internal combustion engine, comprising the steps of:
detecting combustion light intensity in respective combustion
chambers of the engine:
converting the detected light intensity of a combustion chamber
into the electrical signal corresponding to a measure of the
detected combustion light intensity; and
comparing the electrical signal with a predetermined slice level
and judging that the engine is operating outside of an allowable
limit of NOx emission when the signal level of the electrical
signal is less than said predetermined slice level. .Iaddend.
.Iadd.20. A method of detecting a condition of operation of an
internal combustion engine according to claim 19, wherein an
average value of combustion light intensity is determined for a
prescribed number of power cycles; and
said average value is compared with a predetermined level for
judging a misfire condition of the engine. .Iaddend. .Iadd.21. A
method of detecting a condition of an internal combustion engine,
comprising the steps of:
detecting combustion light intensity in respective combustion
chambers of the engine;
converting the detected combustion light intensity of a combustion
chamber into an electrical signal corresponding to a measure of the
detected combustion light intensity; and
detecting an amount of NOx emitted from the engine on the basis of
said electrical signal. .Iaddend. .Iadd.22. An apparatus for
controlling an internal combustion engine, comprising:
means for detecting combustion light intensity in respective
combustion chambers of the engine;
means for converting detected combustion light intensity of a
combustion chamber into an electrical signal corresponding to a
measure of the detected combustion light intensity;
means for comparing the electrical signal with a predetermined
slice level and judging that the engine is operating in a misfire
condition when the signal level of the electrical signal is less
than the predetermined slice level; and
means for controlling at least one of fuel air ratio and ignition
timing
until no misfire takes place. .Iaddend. .Iadd.23. An apparatus for
controlling an internal combustion engine, comprising:
means for detecting combustion temperature in respective combustion
chambers of the engine;
means for converting detected combustion temperature of a
combustion chamber into an electrical signal corresponding to a
measure of the detected combustion temperature;
means for comparing the electrical signal with a predetermined
level and judging that the engine is operating in a misfire
condition when the signal level of the electrical signal is less
than the predetermined level; and
means for controlling at least one of fuel air ratio and ignition
timing until no misfire takes place. .Iaddend. .Iadd.24. An
apparatus for controlling an internal combustion engine,
comprising:
means for detecting combustion light intensity in respective
combustion chambers of the engine;
means for converting detected combustion light intensity into an
electrical signal corresponding a measure of the detected
combustion light intensity;
means for comparing the electrical signal with a predetermined
level corresponding to an allowable limit of NOx exhausted from the
engine and judging the amount of NOx to be outside of the limit
when a signal level of the electrical signal is equal to or larger
than the predetermined level; and
means for controlling at least one of fuel air ratio and ignition
timing until the amount of NOx is within an allowable limit.
.Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates to a control apparatus for internal
combustion engines and, more particularly, to apparatus for
controlling the fuel air ratio and the ignition timing of a
lean-burn engine so as to keep them within the target range.
In a control apparatus for internal combustion engine, for example,
a conventional lean burn control apparatus detects the air fuel
ratio controlled by a lean sensor which produces a signal
corresponding to the concentration of the oxygen in exhaust gas and
controls the detected air fuel ratio so as to be the same as the
target lean air fuel ratio, as described in Japanese Patent
Laid-Open No. 279747/1987.
The target lean air fuel ratio is set at a specific air fuel ratio
within the air fuel ratio range defined by the misfire boundary air
fuel ratio of an engine and the air fuel ratio determined by the
NOx limit necessary to clear a regulation of exhaust gas, namely,
at a specific air fuel ratio within the target control range.
In the above-described prior art, however, a change of an engine
with time is not taken into adequate consideration, and the target
lean air fuel ratio set in the above-described way keeps a constant
value irrespective of a change of the engine with time. Since it is
expected that a change of the engine with time, a change in fuel
property, a change in the atmosphere condition and the like move
the misfire boundary to the high air fuel ratio side, the target
lean air fuel ratio is conventionally set in advance at a value on
a fuel rich side of the target control range (in FIG. 3) in
consideration of the above-described movement of the misfire
boundary. This fact makes a sacrifice of fuel cost and brings about
a problem such as the increase in an amount of exhausted NOx with
the increase in the weight of the car body, thereby making it
difficult to clear the regulation of exhaust gas.
SUMMARY OF THE INVENTION
An object of the invention is to provide a control apparatus for an
internal combustion engine which is constantly capable of
determining an appropriate target control range and controlling the
engine so as to run within the target control range.
Another object of the invention is to provide a lean-burn control
apparatus which is constantly capable of determining an appropriate
target control range in accordance with a change of an engine with
time or the like and controlling the lean air fuel ratio so as to
keep it within the target range.
According to an aspect of the invention, a lean-burn control
apparatus is characterized by misfire means for detecting a
misfiring state of said engine; means for detecting NOx
concentration information of said engine; and means for controlling
said fuel air ratio and said ignition timing so as to fall within a
tolerable stable combustion range which is defined based on signals
from misfire detector and said NOx concentration information
detector, and in which combustion is stable and produces NOx of a
tolerable concentration.
In an internal combustion engine control, it is preferable to
provide a temperature sensor or detector employing a black body
which can directly detect temperature change in the combustion
chamber, and which comprises a thin black body film and an optical
transmission element connected to the black body film for
transmitting radiant energy generated by the black body film.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a flow chart of a lean-burn control for explaining an
embodiment of the present invention;
FIG. 2 is a schematic diagram of a lean-burn control apparatus;
FIG. 3 is a graphical illustration showing the characteristics of
air fuel ratio, torque and NOx;
FIG. 4 is a graphical illustration showing the characteristics of
air fuel ratio and ignition timing;
FIG. 5 is a schematic diagram of an engine control system according
to an embodiment of the invention;
FIGS. 6 and 7 each are a sectional view of a combustion light
sensor;
FIG. 8 is a schematic diagram showing the detailed structure of the
present invention;
FIG. 9 is a schematic diagram showing a part of the structure shown
in FIG. 8;
FIG. 10 is a graphical illustration showing a relationship between
combustion light intensity and NOx concentration;
FIG. 11 is a graphical illustration showing characteristics of
combustion pressure and combustion light intensity;
FIG. 12 is a graphical illustration showing relationship between
ignition timing and air fuel ratio;
FIG. 13 is a detailed flow chart of part of the above
embodiment;
FIG. 14 is a detailed flow chart of part of the above
embodiment;
FIG. 15 a detailed whole flow chart of lean-burn control according
to the present invention;
FIG. 16 is a sectional view of a black body sensor;
FIG. 17 is a sectional view taken along a line 17--17 of FIG.
16;
FIG. 18 is a sectional view of parts of an engine and a black body
sensor;
FIG. 19 is a sectional view of an ignition plug incorporated with a
black body sensor;
FIG. 20 is a graphical illustration showing a relationship between
spectral radiant energy and wavelength;
FIG. 21 is a graph showing a relationship between optical current
and temperature;
FIG. 22 is a graph showing a relationship between NOx and
temperature;
FIG. 23 is a block diagram of a processing circuit in another
embodiment of a lean-burn control apparatus;
FIG. 24 is a detailed flow chart;
FIG. 25 is a detailed flow chart;
FIG. 26 is a block diagram of an embodiment of a knock control
apparatus;
FIG. 27a is a diagram showing a circuit of photo detector;
FIGS. 27b and 27c are diagrams showing input waveform and output
waveform, respectively, of the photo detector;
FIG. 28 is a graph showing a relationship between the load
resistance and the response time of the photo detector;
FIG. 29 shows a relationship between the wavelength and relative
sensitivity of the photo detector;
FIG. 30 shows a relationship between the radiation illuminance of
the photo detector and the optical current;
FIGS. 31a-c show the waveforms of a knock signal and a cylinder
discrimination signal;
FIGS. 32(a) and 32(b) each are a graph showing the relationship
curve of the knock level and the cumulative frequency distribution
at which the knock is judged;
FIG. 33 is graphs (a) to (f) showing the waveforms of the knock
signal at the respective stages in the embodiment;
FIG. 34 is graphs (a) to (c) showing the waveform of the detection
signals obtained from the respective cylinders of the engine, the
waveform of the knock signal taken out by the optical transmission
element, and the waveform of the knock signal obtained by the
shaping circuit in the embodiment of the present invention,
respectively;
FIG. 35 is a flow chart of the operation of the embodiment of the
present invention;
FIG. 36 is graphs (a) to (d) respectively showing the knock
waveform detected by a piezoelectric element, the knock waveform
detected by the detector of the present invention, the waveform of
distribution of the high frequency components of the knock waveform
detected by the piezoelectric element, the waveform of distribution
of the high frequency components of the knock waveform detected by
the detector of the present invention; and
FIG. 37 is a graph showing a relationship between the compression
ratio and the .[.output.]. .Iadd.power .Iaddend.of an engine, and a
relationship between the compression ratio and the ignition timing
with respect to a knocking state a, no knocking state b and a trace
knock state c.
DETAILED DESCRIPTION OF THE INVENTION
Description will be made on a lean-burn control of an aspect of the
invention.
First of all, in the lean-burn control, the misfire boundary and
the NOx limit are detected.
The misfire boundary and the NOx limit have characteristics shown
in FIG. 4 with respect to air fuel ratio and ignition timing. The
misfire boundary consists of the misfire boundary -A- on an
advanced ignition timing side and the misfire boundary -B- on a
.[.delay.]. .Iadd.retarded .Iaddend.ignition timing side. The NOx
limit comes closer to the lean air fuel ratio side as the ignition
timing advances. As engine torque to the weight of the car becomes
smaller due to the progress of lean-burn, the NOx limit moves to
the right-hand side in FIG. 4 and, hence, the target control range
defined by the NOx limit and the misfire boundary becomes smaller,
thereby making the control difficult.
The misfire cycle includes a defective ignition cycle -B- in which
a spark does not produce a flame nucleus, and a defective flame
propagation cycle -A- in which ignition does not grow the flame.
Both of these cycles are a cycle which produces little combustion
flame light, so that it is possible to detect a misfire cycle from
the intensity of the combustion light or the combustion
temperature. On the other hand, it is known that NOx is a parameter
of a combustion temperature. It is also said that the emission
spectrum of NOx is a wavelength of 5.3 .mu.m and the light
intensity at this wavelength is a function of the concentration of
NOx.
Therefore, the misfire cycle and the concentration of NOx can be
detected through detection of the combustion light or the
combustion temperature in the combustion chamber of an engine.
Next, a control target range for effecting lean-burn of an internal
combustion engine is determined by using the detected misfire cycle
and the detected NOx concentration.
Finally, the ignition time and the air fuel ratio are set in the
control range defined by the misfire cycle and the concentration of
NOx.
In an internal combustion engine control, it is preferable to
directly detect the temperature in the engine. A temperature
detector using black body suitable to detect such a temperature is
provided.
An embodiment of the present invention will be explained in detail
hereinunder.
In FIG. 1 showing a schematic control flow chart, on steps 1 and 2,
signals of an air fuel ratio A/F, an ignition timing Adv, misfire
and NOx are inputted to a digital arithmetic unit of a
microcomputer. At step 3, judgement is made as to whether or not
the misfire signal and the NOx signal are in the target control
range which is determined by a misfire boundary and a NOx limit. If
these signals are out of the target control range, the process is
moved to the correcting operational mode at step 4 to control the
A/F and the Adv so as to enter the target control range. If these
signal are in the target control range, the process is moved to the
ordinary operational mode at block 5 to carry out ordinary
control.
In FIG. 2 showing an embodiment of a lean-burn control apparatus,
the apparatus comprises a misfire detector 7 for detecting the
misfiring state of an engine 6, a NOx detector 8 for outputting a
signal corresponding to the concentration of NOx which is produced
by or exhausted from the engine 6, and a digital arithmetic unit 9
of a microcomputer for inputting the signals of these detectors 7
and 8. In addition to these signals, the air fuel ratio A/F signal
of an air fuel mixture supplied to the engine 6 and the ignition
timing Adv signal are inputted to the digital arithmetic unit 5.
Based on these items of information, the digital arithmetic unit 9
selects the ordinary operational mode 10 or the correcting
operational mode 11 in accordance with the control flow shown in
FIG. 1. The selected operational mode is executed, and a control
signal is outputted to the ignition timing control means 12 and the
fuel amount or air amount control means 13 so as to control the Adv
and the A/F.
The above-mentioned method will be further explained referring to
FIG. 4. If the misfire boundary is taken into consideration, the
target control range must be on the left-hand side of the misfire
boundary in FIG. 4, while if the NOx limit is taken into
consideration, the target control range must be on the right-hand
side of the NOx limit in FIG. 4. Therefore, if both are taken into
consideration, the target control range must be set at the range
surrounded by the misfire boundary and the NOx limit. Assuming that
the misfire detector detects the misfiring state of the engine, and
the A/F and Adv values at this state indicate point P.sub.1, the
A/F is so controlled as to move in the direction of Rich and be
situated at point P.sub.2, thereby canceling the misfiring state.
If the detected value of NOx is smaller than a tolerance limit of
the NOx limit, it is judged to be controlled within the target
control range.
On the other hand, if the signals are, for example, at point
P.sub.3 at which the detected value of NOx is beyond the tolerance
limit, the A/F is so controlled as to move in the direction of Lean
and be situated at point P.sub.4 at which the NOx is in the
tolerance limit. In this case, if the signal detected by the
misfire detector is judged to be a non-misfiring state, the misfire
and NOx signals are considered to have been moved to the target
control range, and the correction control is stopped at that
stage.
If the misfire and NOx signals are at, for example, point P.sub.5
at which the detected value of the NOx detector is beyond the
tolerance limit, the A/F is so controlled as to move in the
direction of Lean and be situated at point P.sub.6 at which the NOx
is in the tolerance limit in the same way as in the case of
P.sub.1. In this case, however, since the misfire detector judges
the engine to be in the misfiring state, both conditions cannot be
satisfied. In this case, it is necessary to temporarily return to
point P.sub.5 and control the A/F so as to move in the direction of
Lean and in the direction in which the ignition timing Adv is
.[.delayed.]. .Iadd.retarded .Iaddend.and to reach point P.sub.7,
or to control the A/F and Adv so that the misfire and NOx signals
move from point P.sub.6 to point P.sub.7.
If the signals are at, for example, point P.sub.8 at which the NOx
is within the tolerance limit but the misfire signal is judged to
be beyond the misfire boundary, the A/F is made richer so as to
reach the point P.sub.9, thereby escaping from the misfire
boundary. However, since the NOx is beyond the tolerance boundary
at point P.sub.9, it is necessary to temporarily return to the
point P.sub.8 so as to advance the ignition timing Adv by a
predetermined value and simultaneously to make the A/F richer so as
to reach point P.sub.10, thereby satisfying the conditions of both
misfire and NOx. Alternatively, a control from P.sub.9 to P.sub.10
is possible, as described above.
FIG. 5 shows the total structure of the lean-burn control apparatus
according to the present invention. In FIG. 5, a combustion sensor
having a function of detecting the misfiring state of an engine and
the concentration of NOx comprises a combustion detecting terminal
21 mounted on a combustion chamber 23 of the engine 22 in such a
manner as to communicate with the combustion chamber 23, an optical
fiber cable .Iadd.24 .Iaddend.for carrying out optical transmission
between the combustion detecting terminal 21 and an optical signal
processing circuit 25 .[.and the optical signal processing circuit
25.]..
The combustion detecting terminal 21 may be either integrally
provided with an ignition plug, as shown in FIG. 6, or of a
stand-alone type, as shown in FIG. 7. In FIG. 5, the former type of
detection terminal is mounted on the apparatus. In this case, an
ignition pulse is provided for the combustion detecting terminal 21
by a controller 27 having a built-in microcomputer through an
ignition device 26, so that the combustion detecting terminal also
has a function of an ignition plug.
A combustion light signal or combustion temperature signal which is
subjected to photoelectric conversion and signal processing by the
optical signal processing circuit 25 is introduced to the
controller 27. To the controller 27, an air fuel ratio signal
detected by an air fuel ratio sensor 28 (or oxygen sensor), a
throttle valve opening degree information signal supplied from a
throttle valve opening degree sensor or a throttle valve opening
degree switch 29, an air flow rate signal detected by an air flow
sensor 30, and an engine cooling water temperature signal detected
by a water temperature sensor 31, an engine revolution number
signal and a crank angle signal detected by a revolution sensor 32,
etc. are also inputted.
The controller 27 determines the optimum fuel amount and the
optimum ignition timing by the arithmetic processing of these
plural signals, and outputs a control signal to both an injector 33
and the ignition device 26. The injector 33 injects the optimum
amount of fuel to supply it to the engine in accordance with the
control signal. The ignition device 26 discharges sparks to the
ignition plug 21 at the optimum ignition timing.
In FIG. 5, the multi-point fuel injection system is adopted, but
the present invention is not restricted thereto, and any system
such as a carburetor and a single-point fuel injection system may
be adopted. Although the air flow rate direct measuring system
using the air flow sensor 30 is adopted in FIG. 5, any other air
flow rate measuring system may be adopted such as a speed density
system for calculating the air flow rate from the revolution number
of the engine and the suction negative pressure and a system for
calculating the air flow rate from the revolution number of the
engine and the opening degree of the throttle valve.
FIG. 6 is a sectional view of the main part of the fuel detecting
terminal of a type in which it is integrally provided with an
ignition plug. A fused silica fiber 36 having a diameter of about
1.0 to 1.5 mm, which is a photoconductive material, is provided
therein in such a manner as to pass through a central axis of a
central electrode 34 of the ignition plug and a high-voltage
terminal 35. An insulator 37 is secured to these three members 34,
35 and 36 at a sealed portion 38 by heat sealing of a conductive
glass sealing material. A high voltage for spark discharge is
introduced to the central electrode 34 through the high-voltage
terminal 35 and the conductive glass sealed portion 38 to carry out
spark discharge with a grounding electrode 39. The configuration of
the end portion 36a of the fused silica fiber on the combustion
chamber side may be the optimum configuration selected from among a
convex lens, a flat shape, a tapered shape and the like in
accordance with the configuration of the combustion chamber, the
angle at which the combustion detecting terminal 21 is provided and
the like.
FIG. 7 is a sectional view of the main part of the stand-along type
combustion detecting terminal. The combustion detecting terminal is
provided with a metal housing 41 having a screw portion 40 for
mounting the combustion detecting terminal to an engine, and the
fused silica fiber 36 provided in such a manner as to go through a
central axis of an optical fiber guide terminal 42. These three
members 41, 36 and 42 are secured to each other at the sealed
portion 38 by heat sealing of a glass sealing material, in the same
way as in FIG. 6. Additionally, although explanation of the sealing
material is omitted in FIG. 6, a material having a melting point of
about 600.degree. to 800.degree. C. is used as the sealing material
so as to secure adequate sealing property and adherence even at a
high temperature due to heat conduction or radiation from the
engine. The end portion 36a of the fused silica fiber has a similar
structure to that in FIG. 6, explanation thereof being omitted
herein.
In a conventional method of detecting misfire, it is generally
inferred from the magnitude of a revolution change of an engine. In
the present invention, however, a method of detecting misfire from
the intensity of the combustion flame light or the combustion
temperature at the time of combustion is adopted.
In the present invention, the concentration of NOx is obtained from
the combustion temperature by utilizing the fact that there is a
corresponding relationship between the combustion temperature in
the combustion chamber and the concentration of NOx. As another
method, a method of obtaining the concentration of NOx from the
intensity of the combustion light at the wavelength of 5.3 .mu.m is
adopted by utilizing the fact that the emission spectrum of NOx is
5.3 .mu.m. Alternatively, a method of inferring the concentration
of NOx from the temperature of the exhaust gas immediately after
the combustion chamber is effective, because the temperature of
this exhaust gas substantially corresponds to the combustion
temperature.
The above-described methods of detecting misfire and NOx will be
summed up as follows:
(1) A method of detecting misfire and NOx from the intensity of the
combustion light.
(2) A method of obtaining misfire and NOx by detecting the
combustion temperature.
The method (1) of detecting misfire and NOx from the intensity of
the combustion light will first be explained. In this case, the end
portion 36a of the combustion detecting terminal 21 is so designed
as to secure sufficient light transmission by polishing the surface
or the like, as shown in FIGS. 6 and 7.
FIG. 8 schematically shows the structure of the transmission and
processing of an optical signal in this case. The combustion light
detecting terminal 21 is mounted on each of the combustion chambers
23a to 23d in a manner as shown in FIG. 5. The present invention
also allows a system for detecting only one specified chamber. The
optical signals from the combustion light detecting terminals 21a,
21b, 21c and 21d are introduced to the optical signal processing
circuit 25 through the respective optical fiber cables 24a, 24b,
24c and 24d. As the optical fiber cable 24, a high heat-resistant
plastic fiber which can resist a temperature above about
140.degree. to 150.degree. C. is preferable. A plastic fiber
facilitates the formation of an integrated single-core fiber 43
which is composed by melting the plural fibers into one fiber, as
shown in FIG. 8. The power or combustion stroke of a four-cycle
engine is one cycle of the four cycles. In the case of a
four-cylinder (combustion chamber) engine, the power stroke in each
combustion chamber is subsequently repeated at every 180 degrees.
In the case of a six-cylinder engine, it is repeated at every 120
degrees, and the overlap of the power stroke between each chamber
is as small as 60 degrees. Therefore, even if the single-core fiber
43 is used, it is easy to discriminate an optical signal from one
cylinder (combustion chamber) from an optical signal from another
cylinder, because the optical signal from each combustion chamber
is introduced to the optical signal processing circuit 25
intermittently with almost no overlapping. It goes without saying
that light may be transmitted from each cylinder through optically
separate fibers without integrating the fibers.
FIG. 9 shows the structure of the optical signal processing circuit
25. The combustion light introduced by the single-core fiber 43 is
divided here again into two parts, and introduced to a fiber 44 for
NOx concentration detection and a fiber 45 for misfire cycle
detection. The light for detecting the concentration of NOx is
introduced to a first photoelectric transducer 47 through an
optical filter 46 which only transmits the light of a wavelength of
5.3 .mu.m. The light intensity corresponding to the concentration
of NOx is detected and is converted into electricity. On the other
hand, the light for detecting misfire is directly introduced to a
second photoelectric transducer 48 and is converted into
electricity. The electrically converted signals are processed by
electric signal processing circuits 49 and 50 to output electric
signals 49a, 50a which are supplied to a controller 27. In the case
of this system, since it is necessary to transmit the light of a
wavelength of 5.3 .mu.m in the infrared spectral range, there is a
possibility of a photoconductive material such as the
above-described plastic fiber not introducing sufficient light to
the optical signal processing circuit 25 due to large transmission
loss. In this case, a fluorine optical fiber which is excellent in
transmission to light in the infrared spectral range is used. When
it is impossible to melt a plurality of fibers into one fiber
unlike a plastic fiber, they are integrated into one by an optical
element at the optical signal processing circuit, or a
photoelectric transducer is provided in correspondence with each
cylinder (combustion chamber).
The misfire signal and the NOx signal obtained in this way are
introduced to the controller 27, as shown in FIG. 8, and computed
together with a plurality of other engine parameter signals 22a,
whereby the air fuel ratio control 13a and the ignition timing
control 12a are effected.
FIG. 10 shows a relationship between the concentration of NOx and
the combustion light intensity signal in the 5.3 .mu.m zone in the
case of adopting the system shown in FIGS. 8 and 9. Since they have
substantially proportional relationship, an electric signal output
from the signal output end 49a in FIG. 9 takes the value
substantially corresponding to the concentration of NOx.
FIG. 11 shows an example of the waveform of a misfiring state
detected by the system shown in FIGS. 8 and 9. The electric signal
of the intensity of the combustion light and the combustion
pressure signal output from the signal output end 50a in FIG. 9 are
detected at the same time for judging misfire. As is obvious from
FIG. 11, when the engine is misfired, the intensity of the
combustion light becomes zero, thereby producing no waveform, while
the combustion pressure is only composed of the compression
pressure, and no rise in the pressure following combustion is
observed. Therefore, a slicing level S is provided as indicated by
the symbol S in FIG. 11, and if the signal has a value lower than
this value, the engine is judged to be in a misfiring state, and
signal pulse corresponding to this misfire cycle is produced and
transmitted to the controller 27. Thus, the misfire information is
consecutively transmitted to the controller.
FIG. 12 shows the average value of the peak values V.sub.p for
several cycles of the combustion light intensity signals shown in
FIG. 11 with respect to the air fuel ratio and the ignition timing
represented by a contour line. The smaller the subscript is, like
V.sub.pl, the larger the peak value, and V.sub.pn is the smallest.
As is clear .[.form.]. .Iadd.from .Iaddend.FIG. 12, the contour
line of V.sub.p has a configuration well corresponding to the curve
of the misfire boundary in FIG. 4, and judgement as to misfire also
may be made by using the average value V.sub.p for several
cycles.
FIG. 13 is a flow chart for judging the tolerance limit of NOx. At
step 51, the signal is photoelectrically converted into an electric
signal through the photoelectric transducer 47 and the electric
signal processing circuit 49 shown in FIG. 9, and the electric
signal input as a NOx signal to the controller 27 at step 52. The
concentration of NOx is calculated at the step 53 according to the
characteristics shown in FIG. 10. In this case, it is preferable to
obtain the average value for several .[.ten.]. .Iadd.tens of
.Iaddend.power cycles. At step 54, the tolerance value (value
satisfying the right-hand side range of the NOx limit line of FIG.
4) is compared with the NOx value calculated at the step 53 and
judgement is made as to whether or not the calculated NOx value is
in the range of the tolerance limit. If the answer is yes, the
process proceeds to step 55 for the ordinary operational mode,
while if the answer is no, the process proceeds to step 56 for the
collecting operational mode and various controls are executed.
FIG. 14 is a flow chart for judging a misfiring state. The
combustion light intensity signal is photoelectrically converted
through the photoelectric transducer 48 and the electric signal
processing circuit 50 in FIG. 9 at step 57 and a misfire pulse is
produced at the electric signal processing circuit 50 at step 58.
More specifically, the waveform of the combustion light intensity
signal as shown in FIG. 11 is input at the step 58, and judgement
is made as to whether the peak value of the waveform of the
combustion light intensity signal produced in each power cycle is
larger or smaller than a predetermined slicing level S as shown in
FIG. 11. If the peak value is larger than S, the cycle is judged to
be misfire, and a misfire pulse is produced and outputted for a
predetermined period in the corresponding cycle.
The misfire pulses obtained in this way are inputted to the
controller 27 at step 59. The misfire pulses produced at the step
59 are counted for a predetermined number of times of power cycles
at the step 60 and the count value is supplied to step 61. At the
step 61, whether or not the count value is above a predetermined
value is judged, and if the answer is yes, the process proceeds to
the correcting operational mode 62, while if the answer is no, the
process proceeds to the ordinary operational mode 63.
The portion A in FIG. 13 and the portion A' in FIG. 14 are executed
by the controller 27.
FIG. 15 is a flow chart integrating the portions A and A' and
showing the details of the correcting operational mode.
At step 64, the signals of the engine revolution number N.sub.E and
the air flow rate Q.sub.A (or load information such as the pressure
of the intake pipe and the opening degree of the throttle valve)
are inputted to the controller 27 and further at step 65, signals
of air fuel ratio A/F (the value is represented by X) and ignition
timing Adv (the value is represented by Y) are inputted to the
controller 27.
At step 66, the signal of the misfire pulses (M) produced at the
electric signal processing circuit 50 in FIG. 9 and the signal of
NOx (N) produced at the electric signal processing circuit 49 are
inputted to the controller 27. The value of N is a waveform
peak-held for each power cycle.
At step 67, the concentration of NOx is converted from the NOx
signal (N) inputted at the step 66 by using the characteristics
shown in FIG. 10. At this step, the thus-converted concentration
values of NOx for given several ten power cycles are averaged to
.[.calculated.]. .Iadd.calculate .Iaddend.the average value N. At
step 68, judgement is made as to whether or not N is larger than
the tolerance value of the concentration of NOx which is determined
in advance in correspondence with the operational state of the
engine which is, in turn, determined by the N.sub.E and the
Q.sub.A. If the answer is yes, the process proceeds to steps 69 and
70. If the answer is no, the process proceeds to steps 71 and
72.
On the other hand, the number of the misfire pulses M in a
predetermined number of times of power cycles is counted at step
73, and the count value Mx is supplied to step 74, at which whether
or not the count value Mx is smaller than a predetermined number is
judged. If Mx is larger than the predetermined number, the process
proceeds to the steps 72 and 71, while if Mx is smaller, the
process proceeds to the steps 69 and 71. At the steps 69, 70, -70
and 72, operation is carried out only when signals are transmitted
at the same time from two signal lines.
At the step 69, the processing is executed only when the NOx is out
of the tolerance limit and misfire is within the tolerance limit.
In other words, the operation is carried out in the case where the
signals are situated at the points such as P.sub.3, P.sub.5 and
P.sub.9 in FIG. 4. In this case, the air fuel ratio is increased so
as to be lean by a predetermined value in the form of X=X+1, and
the control signal is transmitted to A/F correction control step
75. At the step 75, the amount of air or fuel is controlled by this
control signal, and the mixture having a leaner air fuel ratio than
that at the previous time is supplied to the engine. In the case
of, for example, P.sub.3 in FIG. 4, this mode is repeated so as to
move the NOx signal and misfire signal to the target control range,
for example, to the point P.sub.4, which satisfies both conditions,
and thereafter the process proceeds to step 71 for the ordinary
operational mode. In the case of, for example, P.sub.5 and P.sub.9,
if the mode through the step 69 is repeated, the signals enter the
range, for example, to the points P.sub.6 and P.sub.8, in which NOx
is in the tolerance limit but misfire exceeds the tolerance value.
This state is treated at the step 72. At the step 72, the deviation
.DELTA.Y of the ignition timing Y at the current time from the
preset ignition timing Y.sub.0 which has been set in advance in
correspondence with the operational state of the engine is taken as
.DELTA.Y=Y-Y.sub.0, and at step 76 judgement is made as to whether
or not .DELTA.Y is positive, in other words, ahead of the preset
ignition timing. If .DELTA.Y is positive, namely, if the signals
are situated, for example, at the point P.sub.6 in FIG. 4, the air
fuel ratio is set on the Rich side in the form of X=X-0.5 at step
77, and the signal is supplied to the step 75, thereby executing
the A/F correction control. In parallel to this, the process
proceeds to step 78, and the ignition timing is set on the delay
side in the form of Y=Y-1, and the signal is transmitted to step
79, thereby executing the Adv correction control so that the state
of P.sub.6 comes to the state as indicated by the point
P.sub.7.
On the other hand, if .DELTA.Y is negative, and the state is as
indicated by P.sub.8, the process proceeds to step 80, wherein the
air fuel ratio is set on the Rich side in the form of X=X-0.5, and
the signal is transmitted to the step 75 so as to execute A/F
correction control. At the same time, the ignition timing is set on
the advanced side in the form of Y=Y+1 at the step 81, and the
signal is transmitted to the step 79 so as to execute Adv
correction control, whereby the state of P.sub.8 comes to the state
as indicated by the point P.sub.10.
If both NOx and misfire take values beyond the respective tolerance
values, the process proceeds to the step 70, and the deviation of
the ignition timing is obtained in the form of .DELTA.Y=Y-Y.sub.0.
Whether or not .DELTA.Y is positive is judged at step 82. If
.DELTA.Y is positive, namely, if the state such as that indicated
by the point P.sub.11 in FIG. 4 is assumed, the air fuel ratio is
set at a little richer side than at P.sub.1, in the form of X=X-0.1
at step 83, and the signal is transmitted to the step 75 so as to
execute A/F correction control. Simultaneously, the ignition timing
is set .[.at a little largely delayed side.]. .Iadd.a little bit
larger on the retarded side with respect .Iaddend.to the present
timing in the form of Y=Y-1.5 at step 84, and the signal is
transmitted to the step 79 to execute Adv correction control so
that the point P.sub.11 falls within the target control range. On
the other hand, if .DELTA.Y is negative, namely, if the state such
as that indicated by the point P.sub.12 in FIG. 4 is assumed, the
process proceeds to step 85, and the air fuel ratio is set at a
little leaner side than at P.sub.12 in the form of X=X+0.2, and the
signal is transmitted to the step 75 so as to execute A/F
correction control. Simultaneously, the ignition timing is set at a
largely advanced side in the form of Y=Y+1.5 at step 86, and the
signal is transmitted to the step 79 so as to execute Adv
correction control so that the state of P.sub.12 comes into the
target control range.
In the above A/F X=x+1, X-0.1 . . . and Adv Y=Y+1.5, Y-1, etc., the
numeral "1", "0.5", "1.5", etc. represent control gains each
obtained by once control, for example, "1" is 10% of X, or Y, "0.5"
is 5% of X or Y.
It is effective to add the controller 27 a function of storing A/F
and Adv in a map table made from the N.sub.E and the Q.sub.A when
A/F and Adv are moved to the target control range in this way and
renewing these values when new A/F and Adv are obtained by
executing similar control at the preceding cycle. It is also
effective to obtain the misfire boundary line and NOx limit line by
the repetition of the above-described controls and store these
lines on the map table of A/F and Adv.
The method (2), namely, the method of detecting and controlling
misfire and NOx from the detected combustion temperature will now
be explained.
FIGS. 16 to 18 show in example of a detector 110 suitable for
detecting combustion temperature which can be used for the
combustion detecting terminal 21 used in the system shown in FIG.
5.
The detector 110 comprises an end portion of an optical
transmission element 111 made of quartz (or fused silica fiber)
having a diameter of about 1 mm and having a resistance to a
temperature of 300.degree. to 1,500.degree. C. in the combustion
chamber 23, and a thin black body film 112 of iridium having a
linear expansion coefficient approximate to that of quartz and
attached to the end portion of the optical transmission element
111. The end portion of the element 111 is obliquely cut to provide
a large end surface for detecting spectral radiant energy. The
black body film 112 is attached to the end so as to cover the end
portion of the element including the cut surface. The black body
film 112 is covered with a protective film 113 made of high
heat-resistant material such as quartz and ceramic to prevent the
black body film from being peeled from the element 111 and to
prevent the deterioration of the black body film 112 due to
oxidization and corrosion.
The black body film 112 is formed on the end portion of the element
111 by evaporation, sputtering or the like. The protective film 113
is also formed on the surface of the element 111 by evaporation,
sputtering or the like. The protective film 113 is fused to the
element 111 at an end thereof, so that it is firmly adhered to the
element 111. A sapphire rod may be used in place of the element
111. The black body film 112 and the protective film 113 preferably
have a thickness of as small as about 2 to 5 .mu.m from the point
of view of heat capacity. However, when a sufficient adhesion is
not obtained, the thickness of those films is increased.
The temperature in the combustion chamber 23 of the engine 22
varies with a period of several KHz, and the pressure in the
combustion chamber 23 rapidly changes, but the use of quartz as the
optical transmission element 111 and iridium as the black body 112
realizes a firm structure having a good thermal response because
quartz and iridium have good adhesion and approximately the same
linear expansion coefficient.
In the detector 110 including a part of the optical transmission
elements 111, it is also possible to use platinum, zirconium
nitride or graphite as the black body 112, and, if measurement of a
high temperature is necessary, to use sapphire as the optical
transmission element.
As shown in FIG. 18, the detector 110 and part of the optical
transmission element 111 is located in the combustion chamber 23 of
an engine and secured to a wall portion 22a of the combustion
chamber 23 by screwing.
More specifically, a metal pipe 114 is secured to the outer
periphery of the optical transmission element 111 by a fused glass
115 and the outer periphery of the metal pipe 114 is threaded. A
thread bore engaging the metal pipe 114 is formed on the wall 22a
of the combustion chamber 23. The detector 110 and the optical
transmission element 111 is screwed into and fixed on the wall 22a
through the metal pipe 114.
To the projecting end of the pipe metal 114 which is fixed on the
wall 22a of the combustion chamber 23 in this way, a connecting
member 116 is secured by screwing. The connecting member 116
accommodates a connector 117 for connecting an optical fiber 118 to
the optical transmission element 111. Therefore, when the
connecting member 116 is connected to the projecting end of the
metal pipe 114, the optical transmission element 111 and the
optical fiber 118 are optically connected to each other.
By covering the outer periphery of the optical transmission element
111 with the metal pipe 114 through the fused glass 115, as
described above, the pressure in the combustion chamber 23 of the
engine is prevented from leaking to the outside.
Another example of the detector is of a plug type as shown in FIG.
19.
The detector portion 36b is an end of fused silica or quartz fiber
36 which is disposed in a central electrode 34. The other
construction including a high voltage terminal 35, electrically
insulating porcelain 37, a sealing 38 and a grounding electrode is
the same as in FIG. 6.
The detector portion 36b is the same as in FIGS. 16 and 17. Namely,
it comprises the fiber 36, a black body film adhered on a surface
of and end portion of the fiber 36, and a protective film. The plug
type detector has functions of detection of temperature and
ignition of fuel air mixture in the combustion chamber.
It is known that a black body produces radiant energy to a
temperature. FIG. 20 shows a relationship between the spectral
radiant energy and wavelength and temperature of a black body. It
is possible to infer the temperature by detecting the radiant
energy with respect to a certain wavelength. For example, the
temperature of 1,000.degree. to .[.5,000.degree. C..].
.Iadd.5,500.degree. C. .Iaddend.is obtained by detecting the
radiant energy at the wavelength of a point P in FIG. 20.
When the temperature of the black body film 112 shown in FIG. 16
rises due to combustion gas, in other words, when the combustion
temperature changes, the radiant energy (radiant light)
corresponding to the change is radiated from the black body film
112. By receiving the radiant energy the a photoelectric transducer
through an optical filter (having a transmission to light of 550 nm
in the case of the point P in FIG. 20), it is possible to obtain an
electric signal corresponding to the combustion temperature.
FIG. 21 shows the characteristics of optical current with respect
to the combustion temperature of a photoelectric transducer. The
optical current changes on a log scale with respect to a change in
temperature. Therefore, in the case of detection in a wide
temperature range, a technique of logarithmically compressing the
optical current through a log diode for linearization or the like
is added.
FIG. 22 shows a relationship between combustion temperature and
NOx. The higher the temperature is and the larger the ratio
.lambda. of excess air is, in other words, the larger and leaner
the air fuel ratio A/F is, the higher is the concentration of NOx.
However, there is little difference in the concentration of NOx
between 1 atm and 50 atm in the pressure in the combustion chamber
and it is understood that the influence of the pressure is
negligible in an ordinary combustion state. Therefore, if the air
fuel ratio is detected at a specified time, the concentration of
NOx is easily calculated from the combustion temperature at that
time. Since the value corresponding to the average air fuel ratio
is detected by the air fuel ratio sensor 28, as shown in FIG. 5, if
the combustion temperature is detected, it is possible to calculate
the concentration of NOx.
FIG. 23 shows the structure of the signal processing circuit 25 in
the case of adopting the combustion temperature detecting system.
The heat radiating light from the black body film 112 at the end
portion 110 or 36b introduced by the single-core integrated fiber
43 is introduced to a photoelectric transducer 90 through an
optical filter 89 which transmits only light of a specific
wavelength (e.g., 700 nm). Since the intensity of the radiating
light is a function of a temperature, information on the combustion
temperature is obtained by photoelectric convention of the light
intensity. In case of a misfire cycle, the combustion temperature
naturally does not rise. Therefore, when the voltage of a signal is
less than a predetermined voltage level, the cycle is judged to be
a misfire cycle and the signal is passed through a comparator and a
wave shaper, thereby outputting a misfire signal. Since the
absolute value of the combustion temperature is substantially
proportional to the concentration of NOx, it is possible to output
a signal corresponding to the concentration of NOx from the peak
value or the integrated value of the photoelectrically converted
electric signal. These processings are carried out by an electric
signal processing circuit 91.
The electric signal processing circuit 91 forms the waveforms of
the combustion temperature signals for the respective cycles which
are substantially equal to the waveforms of the combustion
temperature signals shown in FIG. 11 by utilizing the
characteristics shown in FIGS. 20 and 21. A given slicing level is
set by utilizing the fact that the combustion temperature does not
rise at the time of misfire, and when the combustion temperature
signal in a power cycle does not exceed the slicing level, one
misfire pulse is produced in that power cycle and the signal is
output from an output end 92. From an output end 93, the peak value
of the combustion signal which is peak held at each power cycle is
output.
FIG. 24 is a flow chart for judging the tolerance limit of NOx. The
signal photoelectrically converted by the photoelectric transducer
90 and peak held at each power cycle by the electric signal
processing circuit 91 in FIG. 23 (at step 94) is transmitted to the
controller 27 and inputted as a combustion temperature signal at
step 95.
At step 96, an air fuel ratio signal is inputted from the air fuel
ratio sensor 28 shown in FIG. 5. At step 99, the concentration of
NOx is calculated from the combustion temperature by using the
characteristics curve of NOx with respect to the air fuel ratio
(ratio of excess air) such as that shown in FIG. 22. The average
value of the concentrations of NOx for ten cycles is further
calculated, and the result is supplied to step 100 as an average
NOx value. At the step 100, the tolerance value of NOx value are
compared with each other to judge whether or not the average value
is within the tolerance limit. If yes, the process proceeds to
ordinary operational mode 101, while if no, the process proceeds to
the correcting operational mode 102 and the same control as that in
FIG. 15 is carried out.
FIG. 25 is a flow chart for judging a misfiring state. The misfire
pulse obtained by photoelectrically converting a signal by the
photoelectric transducer 90 (at the step 94) and produced by the
electric signal processing circuit 91 (at the step 103) in FIG. 23
is transmitted to the controller 27 and inputted as a misfire pulse
at step 104. At step 105, the number of the misfire pulses is
counted for a predetermined power cycles, and judgment is made as
to whether or not the value is above a preset value. If the value
is less than the preset value, the combustion state is judged to be
a non-misfiring state, and the process proceeds to the step 101. On
the other hand, if the value is above the preset value, the state
is judged to be a misfiring state, and the process proceeds to the
step 102, and the same control as that in FIG. 24 and the portion
B' in FIG. 25 are carried out by the controller 27.
Since the details of the control flow at the portions B and B' are
the same as those in FIG. 15, explanation thereof will be
omitted.
An engine control system employing the abovementioned temperature
detector such as the detector disclosed in FIGS. 16 to 19 is
capable of a precise and effective control of an internal
combustion engine because the sensor directly detects the
temperature in the combustion chamber of the engine.
Such engine control apparatus is applicable to a knock control of
the engine. An example, of the knock control will be described
hereunder, referring to FIGS. 26 to 27.
In an internal combustion engine, there may appear three kinds of
engine combustion states with respect to knock, that is, no knock
state, a knock state and a trace knock state, which are shown by
(a), (b) and (c) in FIG. 37 respectively. The optimum knock state
is of a trace knock from a view point of engine power output. The
knock state or strength, can be changed by changing ignition
timing.
Occurrence of the knock influences change in temperature in the
combustion chamber, so that the knock strength can be detected
through detection of the temperature in the combustion chamber.
Referring first to FIG. 26, the structure of an embodiment of knock
control apparatus according to the invention will be explained.
In FIG. 26, in a combustion chamber 23 of an engine, a detector 110
for detecting a change in the temperature in the combustion chamber
23 is disposed, and the signal detected by the detector 110 is
inputted to a band-pass filter 120 by an optical transmission
element 111, a connector 116 and an optical fiber 118. The output
terminal of the band-pass filter 120 is connected to the input
terminal of a photo detector 130, and the output terminal of the
photo detector 130 is connected to the input terminal of a shaping
circuit 140. The shaping circuit 140 comprises a signal amplifier
141, a linear processing part 142, and a high pass filter 143. The
output terminal of the photo detector 130 is connected to the input
terminal of the signal amplifier 141, the output terminal of which
is connected to the input terminal of the linear processing portion
142. The output terminal of the linear processing part 142 is
connected to the input terminal of the high pass filter 143, the
output terminal of which is, in turn, connected to the input
terminal of an ignition timing correcting means 150.
The detector 110 is the same as disclosed in FIGS. 16 to 18. The
detector as shown in FIG. 19 also can be used for the knock control
apparatus.
The structure of each part of the embodiment will now be explained
in more detail further referring to FIGS. 20 and 27 to 30.
Referring to FIG. 20, there is shown a relationship between the
spectral radiant energy and the wavelength of the black body with
temperature as a parameter. The detector 110 disposed in the
combustion chamber 23 receives heat, and the black body or film 112
generally produces radiant energy such as that shown in FIG. 20 in
correspondence with a temperature. Accordingly, a temperature at a
certain wavelength is obtained by measuring the radiant energy at
that wavelength.
Since the combustion temperature in the combustion chamber 23 is
1,000.degree. to 2,500.degree. C., a band-pass filter having a
transmission range of 0.6 to 0.7 .mu.m is used as the band-pass
filter 120 in FIG. 26, so as to detect a temperature in the range
of 1,000.degree. to 2,500.degree. C.
In this embodiment, an Si photo transistor having a circuit
structure such as that shown in FIG. 27a is used as the photo
detector 130, and a load resistance 131 is connected between the
emitter and the ground at the output stage of the photo transistor.
A bias voltage Vcc is applied between the collector and the ground
of the photo transistor.
FIG. 29 shows the characteristics of the Si photo transistor used
as the photo detector 130 in this embodiment. It is possible to
detect light in the wavelength range of 500 to 1,200 nm.
In the case of using an Si photo transistor as the photo detector
130 in this way, if the combustion temperature varies in the range
of 1,000.degree. to 2,000.degree. C. at the time of generation of
knock, for example, the radiant energy varies in the range of
5.times.10.sup.-1 to 1 mW/cm.sup.2, as shown in FIG. 20, so that
the collector current Ic varies in the range of 0.8 to 2 mA, as
shown in FIG. 30.
In order to convert the collector current Ic produced in the
above-described way into a voltage, a load resistance of 0.1
k.OMEGA. is connected as the load resistance 131 in FIG. 27a in
this embodiment.
When the Si photo transistor is used as the photo detector 130 in
this way, the output signal with respect to the input signal shown
in FIG. 27b takes a same form such as that shown in FIG. 27c. There
is a relationship such as that shown in FIG. 28 between the
response time t.sub.r shown in FIG. 27c and the load resistance
131.
Since it is necessary to detect a change in the temperature for a
period of about 10 KHz for the purpose of detecting knock the value
of 0.1 k.OMEGA. is selected as the load resistance, as described
above.
The operation of this embodiment will be explained with reference
to FIGS. 31 to 36.
A cylinder discrimination signal such as those shown by (a) and (b)
of FIG. 31 and a knock such as that shown by (c) of FIG. 31 are
produced from the engine. A change in the temperature corresponding
to the spectral radiant energy of the knock which is indicated by
the symbol W.sub.1 to W.sub.4 in (a) of FIG. 34 is detected by the
detector 110 shown in FIG. 26 in correspondence with each cylinder.
The thus-detected signal is taken out of the combustion chamber 23
of the engine by the optical transmission element 111 as a time
series optical signal such as that shown by (b) of FIG. 34, and
input to the band-pass filter 120 by the optical fiber 118 through
the connecting member 116.
The band-pass filter 120 has a pass band at 0.6 to 0.7 .mu.m, and
an optical signal Qc corresponding to a combustion temperature of
1,000.degree. to 2,500.degree. C. in the combustion chamber 23 is
supplied to the photo detector 130 through the band-pass filter
120.
The photo detector 130 is composed of the Si photo transistor, as
described above. As shown in FIG. 33, a collector current such as
that shown by (b) is caused to flow in accordance with the
above-described optical signal such as that shown by (a), so that
an output voltage signal such as that shown by (c) is obtained. The
output voltage signal V.sub.c is amplified by the signal amplifier
141 so as to form an output voltage signal V.sub.A such as that
shown by (d) of FIG. 33, which is further linearized by the linear
processing part 142 so as to form an output voltage signal V.sub.L
such as that shown by (e) of FIG. 33. The output voltage signal
V.sub.L is supplied as an input to the high pass filter 143 having
a pass band at above 4 KHz.
The high pass filter 143 takes only the knock component out of the
output voltage signal V.sub.L, and a knock signal V.sub.S such as
that shown by (f) of FIG. 33 is inputted from the high pass filter
143 to the ignition time correcting means 150.
In this way, according to this embodiment, a knock signal V.sub.S
such as that shown by (d) of FIG. 36 is supplied to the output
terminal of the shaping circuit 140. In contrast, (c) of FIG. 36
shows that the knock signal shaped in the same process as in the
present invention and detected by a piezoelectric element is mixed
with the vibration caused by other factors than knock, thereby
making discrimination between them impossible. Incidentally,
measurement in FIG. 36 was carried out when the number of
revolutions of the engine was 6,000 rpm.
As described above, the ignition timing correcting means 150
corrects the ignition timing of the engine in accordance with the
knock signal V.sub.S which has been inputted to the output terminal
of the shaping circuit 140.
FIGS. 32a and 32b are the curves obtained by the statistical
processing of the cumulative frequency distribution of the S values
for 1024 igniting operations which are obtained by converting the
optical signals after passing them through the band-pass filter 120
shown by (c) of FIG. 31 relative to the state S in which no knock
is generated, the state T in which trace knock is generated and the
state U in which knock is generated, respectively.
By using these curves, the ignition timing of the engine is
corrected in the following way.
At step 161 in the flow chart of FIG. 35, the number N of
revolutions of the engine and the basic injection pulse width
are fetched, and at step 162, the optimum ignition timing
.theta..sub.0 is read from the map on the basis of the values
fetched at the step 161.
At step 163, judgement is made as to whether or not the number N of
revolutions of the engine is not more than 4,000 rpm, and if the
answer is yes, the process proceeds to step 165.
At the step 165, the S/L value is set at the position at which the
sensor signal exceeds the slicing level by 10% in the trace knock
state, as shown in FIG. 32a.
On the other hand, if the number N of revolutions of the engine is
judged to be larger than 4,000 rpm at the step 163, the process
proceeds to step 164. Since it is dangerous that the S values
larger than those in the trace knock state continue when the engine
is rotated at such a high speed, the S/L value is set at the
position at which the sensor signal exceeds the slicing level by 2%
in the trace knock state, as shown in FIG. 32b.
The S/L values set at the steps 164 and 165 have been obtained in
advance from experiments.
The process next proceeds to step 166, and the knock signal V.sub.S
of one cylinder obtained in the above-described way is subjected to
A/D conversion to obtain the S value. At step 167, the
thus-obtained S value is compared with the S/L value which has been
obtained in advance.
If it is found from the comparison that the S value is larger than
the S/L value which has been preset in correspondence with the
rotational speed of the engine, the engine is judged to be in the
knock state, whereby the delay control of the ignition timing is
carried out. On the other hand, if the S value is smaller than the
preset S/L value, it is judged that no knock is generated, whereby
the advanced control of the ignition timing is executed.
In this case, in order to make the distribution of the S values
coincide with that in the trace knock state, the ratio of the S
values which are judged to show the knock state and the ratio of
advanced control angle/delay control angle are controlled in
combination with each other. More specifically, if it is assumed
that the generation ratio of the S values larger than the S/L is
10%, since the advance control is carried out once for every ten
igniting operations in the state in which the ignition timing is
stably controlled, the ratio of the advanced control angle to the
delay control angle is set at 1:10. For example, if the S value has
changed by +.DELTA.S with respect to the preset S/L value, the
ignition time is delayed by .DELTA..theta..sub.1, and if the S
value has changed by -.DELTA.S with respect to the preset S/L
value, the ignition timing is advanced by .DELTA..theta..sub.2, and
.DELTA..theta..sub.1 /.DELTA..theta..sub.2 is set at 1/10.
In this way, if the S value is equal to the preset S/L value at the
step 167, the process proceeds to step 168 without any correction
of the ignition timing. If the S value is larger than the present
S/L value at the step 167, the process proceeds to step 169 to set
the delay control angle of .DELTA..theta..sub.1, and at step 171
the ignition timing is subjected to delay control so as to be
.theta.=.theta..sub.0 +.DELTA..theta..sub.1.
On the other hand, if the S value is judged to be smaller than the
preset S/L value at the step 167, the process proceeds to step 170
to set the advanced control angle of .DELTA..theta..sub.2, and at
the step 171 the ignition timing is subjected to advanced control
so as to be .theta.=.theta..sub.0 +.DELTA..theta..sub.2.
This process next proceeds to step 672 to judge whether or not n
and Tp are the same. If the answer is in the affirmative, the
operation of the steps 166 to 172 are repeated. On the other hand,
if the answer is in the negative at the step 172, .theta. is
reloaded as .theta..sub.0 at step 173.
In this embodiment, the ratio of the advanced control angle to the
delay control angle is set at 1:10 in the case where the rotational
speed of the engine is lower than 4,000 rpm, and it is set at 1:50
in the case where the rotational speed of the engine is 4,000 rpm
or higher. In this way, by making the frequency distribution of the
S values coincide with that in the trace knock state and operating
the engine in the state indicated by the curve c in FIG. 37, it is
possible to obtain the maximum .Iadd.power .Iaddend.output
efficiency.
As described above, according to the embodiment of the present
invention, since a change in the temperature in the combustion
chamber is detected by utilizing the radiation of a black body and
a knock signal is obtained on the basis of this detected signal, it
is impossible to detect the strength of the knock without an error
due to vibration even in a high-speed rotational state of the
engine or an error due to the detection surface smudged by soot or
the like. Since the ignition timing of the engine is corrected on
the basis of the thus-detected strength of the knock, this
embodiment of the present invention enables the engine to be
operated constantly in the trace knock state, thereby obtaining the
output of the maximum efficiency.
* * * * *