U.S. patent application number 11/945071 was filed with the patent office on 2008-11-13 for knock control apparatus for internal combustion engine.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. Invention is credited to Takahiko INADA, Kimihiko Tanaya.
Application Number | 20080281504 11/945071 |
Document ID | / |
Family ID | 39829543 |
Filed Date | 2008-11-13 |
United States Patent
Application |
20080281504 |
Kind Code |
A1 |
INADA; Takahiko ; et
al. |
November 13, 2008 |
KNOCK CONTROL APPARATUS FOR INTERNAL COMBUSTION ENGINE
Abstract
A knock control apparatus for an internal combustion engine can
avoid an incorrect knock determination thereby to prevent output
power reduction and suppress knocks occurring in succession. A
knock detection section outputs a knock detection signal based on
an ionic current, and a threshold setting section sets a knock
determination threshold. A knock determination section determines
the occurrence of a knock based on the threshold and the knock
detection signal. A required correction amount setting section sets
a required correction amount for ignition timing based on a knock
determination result, and a control parameter correction section
corrects ignition timing based on the required correction amount. A
noise determination section determines the occurrence of noise
based on whether said knock detection signal or said control
parameter correction amount is within a set level range, and a
noise removal period setting section sets a noise removal period
based on the noise determination result.
Inventors: |
INADA; Takahiko; (Tokyo,
JP) ; Tanaya; Kimihiko; (Tokyo, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Tokyo
JP
|
Family ID: |
39829543 |
Appl. No.: |
11/945071 |
Filed: |
November 26, 2007 |
Current U.S.
Class: |
701/111 |
Current CPC
Class: |
Y02T 10/46 20130101;
F02P 2017/128 20130101; F02D 35/021 20130101; Y02T 10/40 20130101;
F02P 5/152 20130101 |
Class at
Publication: |
701/111 |
International
Class: |
F02D 45/00 20060101
F02D045/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 11, 2007 |
JP |
2007-126850 |
Claims
1. A knock control apparatus for an internal combustion engine
comprising: a knock detection section that evaluates an ionic
current generated upon combustion of a mixture around a spark plug
of the internal combustion engine and outputs a knock detection
signal; a threshold setting section that sets a knock determination
threshold for said knock detection signal; a knock determination
section that determines the presence or absence of a knock based on
said threshold and said knock detection signal; a required
correction amount setting section that sets an amount of correction
for a control parameter including at least ignition timing based on
a determination result of said knock determination section; a
control parameter correction section that sets a control parameter
correction amount based on said required correction amount and
corrects said control parameter; a noise determination section that
determines the presence or absence of noise based on whether at
least one of said knock detection signal and said control parameter
correction amount is within a set level range; and a noise removal
period setting section that sets a noise removal period based on a
determination result of said noise determination section; wherein
said noise removal period setting section starts a noise removal
period timer when it is determined that at least one of said knock
detection signal and said control parameter correction amount is
within said set level range; and said noise removal period setting
section inhibits correction processing of said control parameter
correction section for a period of time in which a timer value of
said noise removal period timer is less than a predetermined value,
and permits said correction processing when said timer value
reaches said predetermined value.
2. The knock control apparatus for an internal combustion engine as
set forth in claim 1, wherein said noise determination section
variably sets said set level range in accordance with said control
parameter correction amount.
3. The knock control apparatus for an internal combustion engine as
set forth in claim 1, wherein said noise removal period setting
section permits, after start of said noise removal period timer,
the correction processing of said control parameter correction
section over a predetermined number of times within a predetermined
time after said timer value reaches said predetermined value.
4. The knock control apparatus for an internal combustion engine as
set forth in claim 1, wherein when at least one of said knock
detection signal and said control parameter correction amount
deviates from said set level range after start of said noise
removal period timer, said noise removal period setting section
permits the correction processing of said control parameter
correction section regardless of said timer value.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a knock control apparatus
for an internal combustion engine which detects knocking
(hereinafter abbreviated as a "knock") of the internal combustion
engine based on an amount of ions (ionic current) generated upon
combustion of the internal combustion engine, and corrects control
parameters (ignition timing, etc.) of the internal combustion
engine in a direction to suppress the knocking.
[0003] 2. Description of the Related Art
[0004] In general, in internal combustion engines, a mixture of air
and fuel introduced into a combustion chamber of each cylinder is
compressed by an ascending movement of a piston received therein,
and in an explosion stroke, the compressed mixture is fired and
combusted by a spark on a spark plug which is generated by
impressing a high voltage to the spark plug in the combustion
chamber, whereby explosion energy at this time is taken out as a
depression force of the piston and is converted into a rotational
output.
[0005] When combustion is performed in the combustion chamber of
each cylinder in the explosion stroke, molecules of the mixture in
the combustion chamber are electrically dissociated (ionized), so
when a high voltage is impressed, immediately after the explosion
stroke, to electrodes for detection of an ionic current which are
installed in the combustion chamber, ions with electric charge thus
generated flow as an ionic current. In addition, it is known that
the ionic current changes sensitively in accordance with the
combustion state of the combustion chamber, and hence, the
combustion state (occurrence of a misfire or a knock) in the
cylinder can be determined by detecting the state of the ionic
current.
[0006] Accordingly, there has conventionally been proposed an
apparatus that can detect the occurrence of a knock in an internal
combustion engine by detecting the state of an ionic current (see,
for instance, a first patent document: Japanese patent application
laid-open No. H10-9108).
[0007] In such a known knock control apparatus for an internal
combustion engine described in the above-mentioned first patent
document, a frequency band corresponding to the knock is extracted
from the ionic current as a knock signal by means of a band-pass
filter, and the knock signal is compared with a predetermined level
to provide knock pulses, based on the number of which it is
determined whether knocking has occurred.
[0008] In case where in the ionic current there occurs noise which
has a frequency approximate to that of a knock and is able to pass
through the bandpass filter, pulses corresponding to the noise are
generated and detected, in view of which the number of the pulses
thus detected is averaged to obtain an average number of pulses,
which is subtracted from the number of knock pulses to provide a
number of pulses corresponding to the knock, by which a control
amount of retard angle is increased.
[0009] In addition, there has also been proposed an apparatus that
is constructed so as to avoid noise generated upon seating of
engine operating valves when vibration generated upon occurrence of
a knock is detected by a knock sensor (see, for example, a second
patent document. Japanese patent application laid-open No.
HE-147079).
[0010] In the knock control apparatus for an internal combustion
engine described in the above-mentioned second patent document, a
first detection knock signal, when being within a set level range,
is assumed to be valve seating noise, and by focusing attention on
a cylinder for which the knock detection signal was obtained, a
reoccurrence detection period timer is started to be driven from
that point in time for counting a predetermined period Ts that is
preset so as to detect the recurrence of noise. When the following
knock detection signal, being within the set level range, is
detected from the same cylinder before the reoccurrence detection
period timer completes the counting of the period Ts, the knock
detection signal is determined as valve seating noise and retard
angle processing corresponding to the knock is cancelled.
[0011] It is known that noise of the same vibration component as a
knock frequency might sometimes be superposed on the ionic current,
depending upon the operating state of the internal combustion
engine, in spite of the non-occurrence of a knock.
[0012] In addition, it is also known that in some engines, the
pressure in a cylinder is sometimes caused to pulsate without
regard to the occurrence of a knock, so a vibration component might
be superposed on the waveform of an ionic current in accordance
with the generation of such pressure pulsation. Further, the
pulsating noise due to the cylinder internal pressure is misjudged
as the occurrence of a knock, so ignition timing is correctively
set to a retard angle side, and the supply of fuel is also
correctively set to a rich side, as a result of which it is
experimentally known that the frequency of occurrence of pulsating
noise and the amplitude strength of vibration thereof both tend to
increase.
[0013] With the conventional knock control apparatuses for an
internal combustion engine, in case where a knock vibration
component is extracted by using a band-pass filter as described in
the above-mentioned first patent document, there is a problem that
noise with the same frequency component as a knock frequency of a
knock is not able to be distinguished from the knock.
[0014] Moreover, there is another problem as stated below. That is,
it is very difficult to extract only a knock signal on which a
noise component with a vibration amplitude strength and a vibration
duration that are comparable with the detection level of a large
knock upon occurrence thereof is superposed, which becomes an
obstacle to the development of a knock detection apparatus
particularly using an ionic current detection system.
[0015] Also, in the case of avoiding pulsating noise of cylinder
internal pressure as in the second patent document, ignition timing
need be correctively set to a retard angle side, and the supply of
fuel need also be correctively set to a rich side due to the
pulsating noise, so the frequency of occurrence of pulsating noise
and the amplitude strength of vibration thereof both tend to
increase. As a result, there exists noise, such as seating noise of
valves of the valve operating system of the engine, which does not
fall into the set level range for masking, and hence there is a
problem that it is after all impossible to avoid the incorrect
detection of pulsating noise.
[0016] Further, when a subsequent knock detection signal, being
within the set level range, is detected from the same cylinder, it
is mistakenly determined that the knock detection signal is valve
seating noise, and retard angle correction processing for ignition
timing is canceled in spite of a knock occurrence state, so there
is a problem that it is impossible to suppress knocks occurring in
succession.
SUMMARY OF THE INVENTION
[0017] Accordingly, the present invention is intended to obviate
the problems as referred to above, and has for its object to obtain
a knock control apparatus for an internal combustion engine which
is capable of avoiding an incorrect knock determination under a
condition in which noise might occur, thereby to prevent falling
into a vicious circle in which noise is further increased due to
the retard angle correction of ignition timing based on the
incorrect knock determination, of preventing the trouble of causing
reduction in output power due to successive retard angle
corrections of ignition timing based on the incorrect knock
determination, and of suppressing knocks occurring in
succession.
[0018] Bearing the above object in mind, a knock control apparatus
for an internal combustion engine according to the present
invention includes: a knock detection section that evaluates an
ionic current generated upon combustion of a mixture around a spark
plug of the internal combustion engine and outputs a knock
detection signal; a threshold setting section that sets a knock
determination threshold for the knock detection signal; a knock
determination section that determines the presence or absence of a
knock based on the threshold and the knock detection signal; a
required correction amount setting section that sets an amount of
correction for a control parameter including at least ignition
timing based on a determination result of the knock determination
section; a control parameter correction section that sets a control
parameter correction amount based on the required correction amount
and corrects the control parameter; a noise determination section
that determines the presence or absence of noise based on whether
at least one of the knock detection signal and the control
parameter correction amount is within a set level range; and a
noise removal period setting section that sets a noise removal
period based on a determination result of the noise determination
section. The noise removal period setting section starts a noise
removal period timer when it is determined that at least one of the
knock detection signal and the control parameter correction amount
is within the set level range. The noise removal period setting
section inhibits correction processing of the control parameter
correction section for a period of time in which a timer value of
the noise removal period timer is less than a predetermined value,
and permits the correction processing when the timer value reaches
the predetermined value.
[0019] According to the present invention, it is possible to avoid
an incorrect knock determination under a condition in which noise
might occur, thereby to prevent falling into a vicious circle in
which noise is further increased due to the retard angle correction
of ignition timing based on the incorrect knock determination. In
addition, it is also possible to prevent the trouble of causing
reduction in output power due to successive retard angle
corrections of ignition timing based on the incorrect knock
determination, and knocks occurring in succession can be
suppressed.
[0020] The above and other objects, features and advantages of the
present invention will become more readily apparent to those
skilled in the art from the following detailed description of a
preferred embodiment of the present invention taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a block diagram schematically showing a knock
control apparatus for an internal combustion engine according to a
first embodiment of the present invention.
[0022] FIG. 2 is a flow chart illustrating a knock determination
operation according to the first embodiment of the present
invention.
[0023] FIG. 3 is an explanatory view showing conversion table
values for retard angle control basic increase amount with respect
to a knock detection pulse in the first embodiment of the present
invention.
[0024] FIG. 4 is a flow chart illustrating a noise avoidance
processing operation according to the first embodiment of the
present invention.
[0025] FIG. 5 is an explanatory view showing the conversion table
values of noise setting level upper and lower limit values with
respect to retard angle control amounts in the first embodiment of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Hereinafter, a preferred embodiment of the present
invention, in which the invention is applied, by way of example, to
a four-cylinder engine, will be described while referring to the
accompanying drawings.
Embodiment 1
[0027] Referring to the drawings and first to FIG. 1, there is
schematically shown, in a block diagram, a knock control apparatus
for an internal combustion engine according to a first embodiment
of the present invention.
[0028] In FIG. 1, the knock control apparatus for an internal
combustion engine includes a knock detection section 6 that has a
spark plug 1 and an ignition coil 2 and is connected to the
internal combustion engine (hereinafter also referred to as an
engine), and an ECU 15 (engine control unit) that is connected to
the knock detection section 6.
[0029] The spark plug 1 is connected to the ignition coil 2 and is
disposed in a combustion chamber of the internal combustion engine,
so that upon de-energization of the ignition coil 2, a high voltage
is impressed to the spark plug 1 thereby to generate a discharge
spark to fire or combust an air fuel mixture in the combustion
chamber. In addition, in order to detect ions generated around the
spark plug 1 during the combustion of the mixture, the ignition
coil 2 has a bias voltage for detection of an ionic current.
[0030] The knock detection section 6 includes a current-voltage
conversion circuit 3 that converts an ionic current i detected
through the ignition coil 2 into a current-voltage signal, a
band-pass filter 4 that extracts a knock signal from the ionic
current signal output from the current-voltage conversion circuit
3, and a waveform shaping circuit 5 that generates a knock pulse
(knock detection signal) by comparing the knock signal from the
band-pass filter 4 with a predetermined level.
[0031] As a result, the knock detection section 6 evaluates the
ionic current i generated upon the combustion of the mixture around
the spark plug 1, and outputs the knock pulse as a knock detection
signal.
[0032] Here, not that the spark plug 1 and the ignition coil 2 for
only one of four cylinders are representatively shown, but ionic
currents from ignition coils for the other three cylinders are also
input to the current-voltage conversion circuit 3 (see an arrow in
FIG. 1).
[0033] The ECU 15 includes a threshold setting section 7, a knock
determination section 8, a counter 9, a required correction amount
setting section 10, a control parameter correction section 11, a
noise avoidance processing section 14 that comprises a noise a
determination section 12 and a noise removal period setting section
13, and unillustrated other calculation units.
[0034] The threshold setting section 7 sets a threshold BGN for the
knock pulse based on the knock pulse (knock detection signal) from
the waveform shaping circuit 5.
[0035] The knock determination section 8 determines the presence or
absence of a knock by comparison of the knock pulse with the
threshold BGN, and outputs the knock pulse larger than or equal to
the threshold BGN as a knock pulse after knock determination
result.
[0036] The counter 9 counts the number of knock detection pulses
KPLS from the knock determination section 8 at each ignition
cycle.
[0037] The required correction amount setting section 10 sets a
required amount of correction for each of control parameters (an
amount of retard angle control) including at least ignition timing
based on the number of knock detection pulses KPLS corresponding to
the knock determination result.
[0038] The control parameter correction section 11 sets a
correction amount of a control parameter based on at least a
required amount of correction (e.g., and an amount of increase of
retard angle control) from the required correction amount setting
section 10, and corrects the control parameter (e.g., ignition
timing).
[0039] The noise determination section 12 in the noise avoidance
processing section 14 determines the presence or absence of noise
in the knock pulse based on whether at least one of the knock pulse
and the control parameter correction amount is within a set level
range. For example, as will be described later, the noise
determination section 12 determines, based on a current number of
input pulses NPLS[Cyl] from the knock detection section 6 as a
knock detection signal, whether the number of input pulses
NPLS[Cyl] is within the set level range.
[0040] In addition, the noise determination section 12 variably
sets the set level range for the noise determination in accordance
with the control parameter correction amount.
[0041] The noise removal period setting section 13 has a noise
removal period timer, and sets the noise removal period for the
control parameter correction section 11 based on the determination
result of the noise determination section 12.
[0042] Specifically, when the noise determination section 12
determines that at least one of the knock pulse and the control
parameter correction amount is within the set level range, the
noise removal period setting section 13 starts the noise removal
period timer, and at the same time, it inhibits the correction
processing of the control parameter correction section 11 for a
period in which the value of the noise removal period timer
(hereinafter also referred to as the "timer value") is smaller than
a predetermined value, whereas it permits correction processing of
the control parameter correction section 11 when the timer value
reaches the predetermined value.
[0043] In addition, after start of the noise removal period timer,
the noise removal period setting section 13 permits correction
processing over a predetermined number of times within a
predetermined time after the timer value reaches the predetermined
value.
[0044] Further, when at least one of the knock pulse and the
control parameter correction amount deviates from the set level
range after start of the noise removal period timer, the noise
removal period setting section 13 permits correction processing
regardless of the timer value.
[0045] Next, reference will be made to the operation of this first
embodiment of the present invention, as shown in FIG. 1.
[0046] The ignition coil 2 detects the ionic current i flowing
through the spark plug 1 and supplies it to the current-voltage
conversion circuit 3. In this connection, note that the detected
values of other ionic currents are supplied from individual
ignition coils (not shown) corresponding to the other cylinders to
the current-voltage conversion circuit 3.
[0047] The ionic current signal generated from the current-voltage
conversion circuit 3 is turned into a knock signal through the
band-pass filter 4, and is further compared with a predetermined
level in the waveform shaping circuit 5 to be turned into a knock
pulse, which is then supplied to the threshold setting section 7,
the noise determination section 8 and the noise determination
section 12 in the ECU 15.
[0048] The counter 9 in the ECU 15 counts the number of knock
detection pulses KPLS at each ignition cycle, and inputs it to the
required correction amount setting section 10 and other calculation
units in the ECU 15.
[0049] Here, note that the first embodiment of the present
invention is not limited to the construction example of FIG. 1, and
like other constructions may also be employed. For example, in FIG.
1, in the knock detection section 6, a knock signal is compared
with the predetermined level to provide a waveform shaped knock
pulse, and the number of knock detection pulses KPLS obtained by
the counter 9 is used as knock information, but an integral value,
a peak value, etc., of the knock signal at each ignition may be
used as knock information. In addition, the ionic current signal or
the knock signal may be converted from analog into digital form at
a predetermined period, and input to an FFT calculation unit (not
shown) in the ECU 15, so that the result of FFT calculation may be
used as knock information.
[0050] Now, reference will be made to knock determination
processing operation of the ECU 15 in FIG. 1 while referring to a
flow chart in FIG. 2 and an explanatory view in FIG. 4.
[0051] Here, note that steps S2, S3 in FIG. 2 correspond to the
processing of the threshold setting section 7, and step S4
corresponds to the processing of a knock determination section 8,
the counter 9 and the noise determination section 12. Also, steps
S5 through S7 correspond to the processing of the control parameter
required correction amount setting section 10, and step S8
corresponds to the processing of the noise avoidance processing
section 14, and step S9 corresponds to the processing of the
control parameter correction section 11.
[0052] In FIG. 2, first of all, the ECU 15 identifies the number of
knock pulses currently generated from the knock detection section 6
as an input pulse number NPLS[Cyl] for each cylinder (Cyl) (step
S1).
[0053] Subsequently, the threshold setting section 7 in the ECU 15
updates, as shown in the following expression (1), a current filter
value FLT[Cyl], which becomes a part of the knock determination
threshold BGN, by using the last filter value FLT[Cyl](n-1) and the
current number NPLS of input pulses (step S2).
FLT[Cyl]=FLT[Cyl](n-1).times.0.98+NPLS[Cyl].times.0.02 (1)
[0054] In expression (1) above, the current filter value FLT[Cyl]
is obtained as a sum pf 98% of the last filter value FLT[Cyl](n-1)
of the cylinder concerned and 2% of the current number of input
pulses NPLS, but other arbitrary filter calculation methods can be
used. In addition, it may be possible to apply processing not to
update the filter value when it is determined the presence or
occurrence of knock.
[0055] Then, the threshold setting section 7 generates a knock
determination threshold BGN[Cyl] based on the level of the knock
detection signal, as shown in the following expression (2), by
adding an offset value OFS(Rev, Load) to the filter value FLT[Cyl]
(step S3).
BGN[Cyl]=FLT[Cyl]+OFS(Rev, Load).times.Coef[Cyl] (2)
where a correction coefficient Coef[Cyl] is a set value which is
weighted for each cylinder, and the offset OFS(Rev, Load) is
acquired by a map value set at least for each pair of the number of
engine revolutions per minute (Rev) and the engine load (Load).
[0056] Subsequently, the knock determination section 8 calculates
the number of pulses corresponding to the knock by subtracting the
knock determination threshold BGN[Cyl] from the current number of
input pulses NPLS[Cyl]. The counter 9 counts pulses from the knock
determination section 8, and obtains the number of knock detection
pulses KPLS[Cyl] for each cylinder, as shown in the following
expression (3) (step S4).
KPLS[Cyl]=NPLS[Cyl]-BGN[Cyl] (3)
[0057] Thereafter, the required correction amount setting section
10 compares the number of knock detection pulses KPLS[Cyl] obtained
in step S4 with a knock determination reference level KJDG, and
determines whether the number of knock detection pulses KPLS[Cyl]
is larger than or equal to the reference level KJDG (step S5).
[0058] When it is determined as KPLS[Cyl]<KJDG in step S5 (that
is, NO), the required correction amount setting section 10 assumes
that the engine is in a non-knocking state, and sets an amount of
increase in the retard angle control of ignition timing
(hereinafter referred to as an "ignition timing retard angle
control increase amount) RINC[Cyl] to zero (step S7), after which
the control flow proceeds to noise avoidance processing (step
S8).
[0059] On the other hand, when it is determined as
KPLS[Cyl].gtoreq.KJDG in step S5 (that is, YES), the required
correction amount setting section 10 assumes that the engine is in
a knocking state, and calculates the ignition timing retard angle
control increase amount RINC[Cyl], as shown in the following
expression (4), by using the retard angle control basic increase
amount (conversion table value) Rtable (KPLS[Cyl]) corresponding to
the number of knock detection pulses KPLS[Cyl] and the correction
coefficient Coef[Cyl] (step S6).
RINC[Cyl]=Rtable(KPLS[Cyl])/Coef[Cyl] (4)
[0060] As shown in expression (4) above, the final retard angle
control increase amount RINC[Cyl] becomes a value that is obtained
by dividing the retard angle control basic increase amount
(conversion table value) Rtable[Cyl] of FIG. 3 by the correction
coefficient Coef[Cyl].
[0061] Here, note that the ignition timing retard angle control
basic increase amount (conversion table value) Rtable (KPLS[Cyl])
is set in accordance with the number of knock detection pulses
KPLS[Cyl], for example as shown in FIG. 3.
[0062] FIG. 3 shows one example of a conversion table from the
number of knock detection pulses KPLS[Cyl] to the retard angle
control basic increase amount Rtable (KPLS[Cyl]), but as is clear
from FIG. 3, the retard angle control basic increase amount Rtable
(KPLS[Cyl]) is set to be larger in accordance with the increasing
number of knock detection pulses KPLS[Cyl].
[0063] Although in FIG. 2, both of correction coefficient division
processing for adjusting the threshold BGN (step S3) and correction
coefficient multiplication processing for adjusting the required
amount of correction with respect to each control parameter (step
S6) are used at the same time, either one of these adjustment
processings may be used. For example, if the step S3 is used
singularly or independently of the other, the division processing
in step S6 can be omitted, whereas if the step S6 is used
singularly, the multiplication processing in step S3 can be
omitted.
[0064] By executing the above-mentioned calculation processing
(steps S1 through S7) at each ignition cycle, the retard angle
control increase amount RINC[Cyl] can be obtained.
[0065] Then, the noise avoidance processing section 14 executes
noise avoidance processing (to be described later together with
FIG. 4) (step S8).
[0066] Finally, the control parameter correction section 11 adds
the retard angle control increase amount RINC[Cyl] to the last
retard angle control amount RTD[Cyl](n-1) for each cylinder, and
correctively calculates a retard angle control amount RTD[Cyl] to
be finally reflected on the ignition timing, as shown in the
following expression (5) (step S9), after which the processing
routine of FIG. 2 is terminated and exited.
RTD[Cyl]=RTD[Cyl](n-1)+RINC[Cyl] (5)
[0067] In this regard, note that the control parameter correction
section 11 applies the decreasing control of retard angle control
amount RTD[Cyl] or like other control at each knock occurrence or
at each predetermined time. In addition, only the ignition timing
is used here as a parameter to be controlled for execution of knock
suppression, but the air fuel ratio of the mixture can also be used
as a control parameter.
[0068] Next, reference will be made to the noise avoidance
processing (step S8) in FIG. 2 while referring to a flow chart in
FIG. 4 and an explanatory view in FIG. 5.
[0069] Here, note that step S11 in FIG. 4 corresponds to the
processing of the noise determination section 12, and steps S12
through S22 correspond to the processing of the noise removal
period setting section 13.
[0070] In addition, the processing of FIG. 4 (step S8 in FIG. 1)
may be executed only within a predetermined range of the number of
revolutions per minute of the engine.
[0071] Here, there is shown the case where the noise determination
section 12 makes a noise determination based on the knock pulse
(the number of input pulses NPLS[Cyl]) from the knock detection
section 6, but the noise determination section 12 can perform a
noise determination based on at least one of the knock pulse from
the knock detection section 6 and the control parameter correction
amount in the control parameter correction section 11, as
previously stated.
[0072] In FIG. 4, first of all, the noise determination section 12
in the noise avoidance processing section 14 compares the current
number of input pulses NPLS[Cyl] from the knock detection section 6
with a noise setting level upper limit value NH[RTD[Cyl]] and a
noise setting level lower limit value NL[RTD[Cyl]], respectively,
and determines whether the current number of input pulses NPLS[Cyl]
is within a set level range between the noise setting level upper
limit value NH[RTD[Cyl]] and the noise setting level lower limit
value NL[RTD[Cyl]] (step S11).
[0073] When it is determined in step S11 that the number of input
pulses NPLS[Cyl] is within the set level range and a relation of
NH[RTD[Cyl]].gtoreq.NPLS[Cyl].gtoreq.NL[RTD[Cyl]] is satisfied
(that is, YES), the noise determination section 12 assumes that the
engine is in a noise generation state, and releases the noise
avoidance stand-by state of the noise removal period setting
section 13 (step S12).
[0074] When it is determined in step S11 that the number of input
pulses NPLS[Cyl] is outside the set level range and a relation of
NH[RTD[Cyl]]<NPLS[Cyl] or NPLS[Cyl]<NL[RTD[Cyl]] is satisfied
(that is, NO), the noise determination section 12 assumes that the
engine is not in a noise generation state, and the noise removal
period setting section 13 proceeds to the following determination
processing (step S17) without executing the processing in steps S12
through S16.
[0075] Here, it is found that noise of the same vibration component
as a knock frequency might sometimes be superposed on the ionic
current i, depending upon the operating state of the internal
combustion engine, in spite of the non-occurrence of a knock, as
stated above, and that in some engines, the pressure in a cylinder
is sometimes caused to pulsate without regard to the presence or
absence of the occurrence of a knock, so a vibration component
might be superposed on the waveform of an ionic current i in
accordance with the generation of such pressure pulsation.
[0076] Further, it is also experimentally known that the
above-mentioned noise due to the pressure pulsation is increased in
both the frequency of occurrence of noise and the amplitude
strength of vibration (i.e., the number of knock pulses is
increased) by setting the ignition timing to a retard angle side
(i.e., by setting the air fuel ratio to a rich side).
[0077] Accordingly, it is found that a high noise avoidance effect
can be obtained by increasing, within the set level range in step
S11, the noise setting level upper limit value NH[RTD[Cyl]] and the
noise setting level lower limit value NL[RTD[Cyl]] with respect to
at least one of the increase of the ignition timing retard angle
control amount RTD[Cyl] and the enriching of fuel.
[0078] On the other hand, regarding knocking, the occurrence of
knocks can be suppressed with respect to the increase of the retard
angle control amount RTD[Cyl], and the frequency of knock
occurrences and the amplitude strength of vibration are decreased,
so an increase in the noise setting level upper and lower limit
values cause no impediment to the knock suppression.
[0079] FIG. 5 is an explanatory view that shows conversion table
values within the set level range in step S11, wherein setting
examples of the noise setting level upper and lower limit values
NH[RTD[Cyl]] and NL[RTD[Cyl]] with respect to the retard angle
control amount RTD[Cyl].
[0080] Since it is considered that the frequency of occurrence and
the amplitude strength of vibration of noise, which has the same
frequency component as the knock frequency, vary depending upon the
operating state of the internal combustion engine, the noise
setting level upper limit value NH[Rev, Load] and the noise setting
level lower limit value NL[Rev, Load] are acquired by map values
that are set for each of the number of engine revolutions per
minute (Rev) and the load (Load), and those values which are
obtained by adding the noise setting level upper limit value
NH[RTD[Cyl]] and the noise setting level lower limit value
NL[RTD[Cyl]] to the noise setting level upper and lower limit
values NH[Rev, Load], NL[Rev, Load], respectively, may be used as
the final noise setting level upper and lower limit values,
respectively.
[0081] Reverting to FIG. 4, after releasing a noise avoidance
processing stand-by state in step S12, the noise removal period
setting section 13 determines whether a noise avoidance counter
NC[Cyl] is less than a retard angle reflection permission period
NJDGC, and at the same time determines whether a retard angle
reflection permission frequency counter RC[Cyl] is larger than "0"
(step S13).
[0082] Here, let us assume that the retard angle reflection
permission period NJDGC is set to "10", and for the first time of
starting noise avoidance processing, the noise avoidance counter
NC[Cyl] is set to "0", and the retard angle reflection permission
frequency counter RC[Cyl] is set to "3".
[0083] Accordingly, for the first time of starting the noise
avoidance processing, the noise removal period setting section 13
determines as NC[Cyl]<NJDGC and [Cyl]>0 RC in step S13 (that
is, YES), and subsequently clears the noise avoidance counter
NC[Cyl] to "0" (step S14) and decrements the retard angle
reflection permission frequency counter RC[Cyl] by one to "2" (step
S15), after which it proceeds to step S17.
[0084] On the other hand, when it is determined as
NC[Cyl].gtoreq.NJDGC or RC[Cyl]=0 in step S13 (that is, NO), the
noise removal period setting section 13 assumes that the retard
angle control increase amount RINC[Cyl] set in step S6 in FIG. 2 is
due to noise, and sets the retard angle control increase amount
RINC[Cyl] to "0" (step S16), after which it proceeds to step
S17.
[0085] At this time, in step S13, the retard angle reflection
permission period NJDGC is set to "10", and the retard angle
reflection permission frequency counter RC[Cyl] is set to the
initial value of "3", so even in an operating state in which knocks
occur in succession, the initially set value (=3) of the retard
angle reflection permission frequency counter RC[Cyl] is reflected
without fail in a retard angle manner within the set value (=10
cycles) of the retard angle reflection permission period NJDGC.
[0086] Although in the example of FIG. 4, the retard angle
reflection permission period NJDGC is set to 10 cycles, and the
retard angle reflection permission frequency counter RC[Cyl] is set
to 3 times, these individual values may instead be set to required
minimum values which can provide a sufficient retard angle control
increase amount RINC[Cyl] against the successive occurrence of
knocks. As a result, it is possible to avoid noise which occurs
sporadically at high frequencies (e.g., once or more every 10
cycles), unlike knocks, thereby making is possible to suppress the
occurrence of successive knocks.
[0087] Reverting to FIG. 4, in step S17, the noise removal period
setting section 13 determines whether the noise avoidance counter
NC[Cyl] is more than or equal to a noise avoidance period set value
NSTC, and at the same time, determines whether it is not in a noise
avoidance stand-by state. Here, it is assumed that the noise
avoidance period set value NSTC is set to "50".
[0088] When in step S17 it is determined as NC[Cyl].gtoreq.NSTC
(=50) and that the noise avoidance stand-by state is released (that
is, YES), the noise removal period setting section 13 is set to a
noise avoidance stand-by state (step S18).
[0089] Subsequently, the noise removal period setting section 13
clears the noise avoidance counter NC[Cyl] to "0" (step S19), and
sets the retard angle reflection permission frequency counter
RC[Cyl] to a reflection frequency initial value RSTC (e.g., "3" in
this example) (step S20), after which the processing routine of
FIG. 4 is terminated and exited.
[0090] On the other hand, when it is determined in step S17 as
NC[Cyl]<NSTC (=50) or that the noise removal period setting
section 13 is in a noise avoidance stand-by state (that is, NO),
the noise removal period setting section 13 subsequently determines
whether the current state thereof is not a noise avoidance stand-by
state (NC[Cyl]<NSTC) (step S21).
[0091] When it is determined in step S21 that the current state is
a noise avoidance stand-by state (that is, NO), the processing
routine of FIG. 4 is terminated without executing step S22, whereas
when it is determined in step S21 that the current state is not a
noise avoidance stand-by state (that is, YES), the noise removal
period setting section 13 increments the noise avoidance counter
NC[Cyl] by one (step S22), and then terminates and exits the
processing routine of FIG. 4.
[0092] As described above, according to the first embodiment of the
present invention, provision is made for the noise avoidance
processing section 14 having the noise determination section 12 and
the noise removal period setting section 13, and the noise removal
period setting section 13 sets the noise removal period based on
the determination result of the noise determination section 12. In
addition, the noise removal period timer is started when it is
determined that at least one of the knock detection signal and the
control parameter correction amount is within the set level range,
and correction processing of the control parameter correction
section is inhibited for a period of time in which the timer value
of the noise removal period timer is smaller than the predetermined
value, but the correction processing is permitted when the timer
value reaches the predetermined value.
[0093] As a result, an incorrect determination of the occurrence of
knocks can be avoided even in a condition where the pulsation noise
of the cylinder internal pressure in the internal combustion engine
is generated, so retard angle correction of the ignition timing
based on the incorrect determination of knocks is not performed,
thus preventing falling into a vicious circle in which noise is
further increased.
[0094] Moreover, it is possible to prevent the trouble or
inconvenience of keeping correcting the ignition timing to a retard
angle based on the incorrect determination thereby to cause the
reduction in the output power of the internal combustion engine,
and in addition, it is also possible to suppress the occurrence of
successive knocks, thus making it possible to improve knock
controllability.
[0095] Further, the noise determination section 12 variably sets
the set level range for noise determination in accordance with the
control parameter correction amount in the control parameter
correction section 11, so the state of noise occurrence can be
determined accurately based on the appropriate set level range.
[0096] Furthermore, the noise removal period setting section 13
permits, after start of the noise removal period timer, correction
processing of the control parameter correction section 11 over the
predetermined number of times within the predetermined time after
the timer value reaches the predetermined value, whereby the
occurrence of knocks can be suppressed in a reliable manner.
[0097] In addition, when at least one of the knock detection signal
and the control parameter correction amount deviates from the set
level range after start of the noise removal period timer, the
noise removal period setting section 13 permits the correction
processing of the control parameter correction section 11
regardless of the timer value, so the occurrence of knocks can also
be suppressed in a reliable manner.
Embodiment 2
[0098] Although in the above-mentioned first embodiment, the noise
determination section 12 determines whether the number of input
pulses NPLS[Cyl] from the knock detection section 6 is within the
set level range, the knock detection signal used for noise
determination is not limited to the number of input pulses
NPLS[Cyl].
[0099] For example, the integral value or the peak value at each
ignition of a knock signal output from the band-pass filter 4 may
be used as a knock detection signal, or an ionic current signal or
a knock signal output from the current-voltage conversion circuit
3, being subjected to an FFT calculation, may be used as a knock
detection signal, and in these cases, it may be determined whether
those values are within the set level range.
[0100] In addition, it may be determined whether the retard angle
control increase amount RINC[Cyl], which is one of control
parameter required correction amounts set in steps S5 through S7 in
FIG. 2, is within the set level range.
[0101] Moreover, the retard angle reflection permission period
NJDGC, the noise avoidance period set value NSTC and the reflection
frequency initial value RSTC in steps S13, S17 and S20,
respectively, in FIG. 4 may be acquired by map values which are set
for each of the number of engine revolutions per minute (Rev) and
the load (Load), so that they may be set to optimal values in each
operating condition.
[0102] Further, the noise avoidance counter NC[Cyl] in step S13 in
FIG. 4 is not limited to the number of ignition cycles but may be
handled as a time.
[0103] Furthermore, if the internal combustion engine is mounted as
for the knock control apparatuses for an internal combustion engine
according to the first and second embodiments of the present
invention are not limited to application to motor vehicles, but can
be applied to other special machines such as motorcycles, outboard
machines, etc., on which an internal combustion engine can be
installed, and in these cases, it is possible to make use of them
for environmental protection through improvements in operation
efficiency, reduction in emissions, etc., of the internal
combustion engine thus installed.
[0104] While the invention has been described in terms of a
preferred embodiment, those skilled in the art will recognize that
the invention can be practiced with modifications within the spirit
and scope of the appended claims.
* * * * *