JPH08128378A - Combustion stability control device of internal combustion engine - Google Patents

Abstract

PURPOSE: To provide a combustion stability control device of an internal combustion engine by which an improvement in fuel consumption, operability and exhaust performance can be reconciled with each other. CONSTITUTION: Though correction control of the ignition timing is added besides controlling an internal combustion engine in desired stability by controlling the air-fuel ratio and an EGR quantity, on combustion whose combustion stability is largely beyond target stability due to realization of leanness of the air-fuel ratio and an increase in the EGR quantity, when the ignition timing is corrected on the basis of θPmax of its combustion, excellent output torque cannot be obtained on the contrary, and it follows that the deterioration of fuel consumption and the deterioration of operability and exhaust performance or the like are incurred. Then, combustion unsuitable for correction control of the ignition timing is detected (d3) on the basis of a combustion condition, and an improvement in fuel consumption and maintenance of operability and exhaust performance are reconciled with each other without performing correction control (d5) of the ignition timing on the basis of θPmax in its combustion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in a device for controlling combustion stability of an internal combustion engine.

[0002]

2. Description of the Related Art The following is a conventional combustion stability control system for an internal combustion engine. That is, in a lean-burn engine or an engine that performs exhaust gas recirculation (hereinafter, also referred to as EGR), as the air-fuel ratio is made leaner or the EGR amount is increased, fuel efficiency is generally improved and NOx production amount is also reduced. However, if a certain limit is exceeded, combustion will become unstable and HC will increase, and there will be problems that engine vibration and vehicle body vibration will increase due to fluctuations in generated torque. Therefore, by detecting the change in the combustion state, calculating the combustion stability index from it, and controlling the air-fuel ratio or the EGR amount accordingly, it is possible to achieve both improved fuel efficiency and drivability and exhaust performance. There is a control system designed to work.

An example of such a device is disclosed in Japanese Patent Application Laid-Open No. 60-104754. This one detects the pressure in the combustion chamber, calculates the average effective pressure from this, and calculates the torque fluctuation from the time series,
The dispersion is used as an index, and the stability of combustion is controlled by controlling the EGR amount so that this index has a desired value.

[0004]

However, in such a conventional combustion stability control device, the air-fuel ratio or the EGR amount (in other words, the control amount for changing the state of the engine intake air-fuel mixture). Therefore, the blow-by gas amount, the purge gas amount from the canister, etc. can be grasped in the same manner.Hereinafter, the MBT (Minimum Spark Advance) will be changed in accordance with the change of the air-fuel ratio or the EGR amount.
Since the required ignition timing that is for the Best Torgue) changes, it is necessary to feedback control the ignition timing in order to obtain a good output. However, because the combustion state is near the stability limit, there are large variations in combustion, and abnormal combustion may be mixed, and the crank angle (θPmax) that maximizes the pressure in the combustion chamber is the target that maximizes the output torque. When feedback control of the ignition timing (that is, MBT control of the ignition timing) is performed so as to match the crank angle, the above θPmax
Is greatly deviated from the target crank angle (and the cause of the deviation is not due to the ignition timing,
This is due to variations in combustion associated with changes in the air-fuel ratio or EGR amount. ), The normal ignition timing control becomes impossible, and there arises a problem that fuel efficiency, drivability, and exhaust performance deteriorate. Therefore, in such a situation, in order to perform the ignition timing control, it is necessary to accurately determine whether or not the θPmax can be reflected in the control.

The present invention has been made in view of the above-mentioned conventional circumstances, and provides a good output even when the control amount for changing the state of the engine intake air-fuel mixture such as the air-fuel ratio and the EGR amount is changed in the vicinity of the combustion stability limit. An object of the present invention is to provide a combustion stability control device for an internal combustion engine, which is capable of optimally controlling the ignition timing so as to obtain a torque and making it possible to improve both fuel efficiency and drivability and exhaust performance. Another object is to improve the accuracy of the control device and simplify the configuration.

[0006]

Therefore, the present invention is configured as follows. FIG. 1 is a block diagram corresponding to the invention described in claim 1. (A) is a combustion chamber pressure detecting means for detecting the pressure in the combustion chamber of the internal combustion engine, and (b) is 1
Combustion state detection means for detecting the combustion state for each combustion, (c)
Is a combustion stability index calculating means for calculating a combustion stability index, and (d) is a function of detecting the crank angle (θPmax) at which the pressure in the combustion chamber is maximum during one combustion stroke according to (a).
It is a Pmax detection means.

(E) is a first ignition timing correction permitting means for permitting correction of the ignition timing when the combustion state detected in (b) is within a predetermined range, and (f) is the above ( This is a first ignition timing correction means for correcting the ignition timing so that θPmax calculated in d) matches the target crank angle at which the output torque of the engine becomes maximum. And
(G) adjusts the control amount (for example, air-fuel ratio, EGR amount, etc.) that changes the state of the air-fuel mixture supplied to the engine based on the combustion stability index calculated in (c) above, and obtains the desired combustion It is a combustion stability control means for realizing the degree.

According to a second aspect of the present invention, the first ignition timing correction permitting means (e) is provided with an ignition timing when the detected combustion state is within a predetermined range with respect to its average value. It is configured as a means for permitting correction of. FIG. 2 is a block diagram corresponding to the invention described in claim 3. The same symbols are given to the same means as the invention described in claim 1,
Description is omitted.

(H) is a second ignition timing correction permission means for permitting correction of the ignition timing when the combustion stability index calculated in (c) is within a predetermined range. (I) is a second ignition timing correction means for correcting the ignition timing so that the θPmax calculated in (d) matches the target crank angle at which the output torque of the engine becomes maximum. Claim 4
In the invention described in (3), the second ignition timing correction permission means (h) is a means for permitting correction of the ignition timing when the calculated combustion stability index is within a predetermined range with respect to a target value. Configured.

FIG. 3 is a block diagram corresponding to the invention described in claim 5. A combustion chamber pressure detection means (a) for detecting the combustion chamber pressure, and a rotational position detection means (j) for detecting the rotational position of the crankshaft or the camshaft,
An average effective pressure calculating means (k) for calculating an average effective pressure in a predetermined rotation section based on the pressure in the combustion chamber detected by the combustion chamber pressure detecting means (a) is included.

According to the sixth aspect of the present invention, the combustion stability index is configured such that the magnitude of combustion fluctuation in the same frequency band as the drive system resonance frequency band is the main index.

[0012]

According to the present invention having the above-mentioned structure, the desired amount is controlled by controlling the control amount (for example, the air-fuel ratio, the EGR amount, the blow-by gas amount, the purge gas amount, etc.) for changing the state of the air-fuel mixture. In addition to controlling the internal combustion engine within the stability of, the ignition timing correction control is performed, but the combustion stability greatly deviates from the target stability due to the lean air-fuel ratio and the increase in the EGR amount. With respect to the above, even if the ignition timing is corrected based on the above-mentioned θPmax of the combustion, not only the effect cannot be expected, but rather, a good output torque is not obtained, but the fuel efficiency is deteriorated and the drivability and the exhaust performance are deteriorated. Etc. will be invited. Therefore, the combustion that is not suitable for the ignition timing correction control is detected based on the combustion state, and the ignition timing correction control based on θPmax in the combustion is not performed to improve the fuel consumption and the operation. Performance and exhaust performance are maintained at the same time.

According to a second aspect of the present invention, the first ignition timing correction permitting means is provided for correcting the ignition timing when the detected combustion state is within a predetermined range with respect to its average value. As a means of permitting, with a relatively simple configuration,
The ignition timing correction permission is determined promptly.
In the invention described in claim 3, instead of the first ignition timing correction permission means according to claim 1, the correction of the ignition timing is permitted when the calculated combustion stability index is within a predetermined range. Since it is configured as described above, it is possible to make a highly accurate permission determination of the ignition timing correction in which control hunting or the like is less likely to occur as compared with the invention described in claim 1.

According to a fourth aspect of the present invention, the second ignition timing correction permission means permits the correction of the ignition timing when the calculated combustion stability index is within a predetermined range with respect to the target value. Since it is configured as a means, it is possible to make a highly accurate determination of permission of ignition timing correction with a relatively simple configuration. In a fifth aspect of the present invention, the combustion state detecting means is set to a predetermined value based on a rotational position detecting means for detecting a rotational position of a crankshaft or a camshaft, and a combustion chamber internal pressure detected by the combustion chamber internal pressure detecting means. An average effective pressure calculating means for calculating the average effective pressure in the rotation section is included, and a combustion state can be detected with high accuracy while saving processing time, memory capacity, etc. with a relatively simple configuration. did.

According to the sixth aspect of the present invention, the combustion stability index is mainly the magnitude of the combustion fluctuation in the same frequency band as the drive system resonance frequency band, so that the frequency range representing the surge torque level is shown. Since the fluctuation in the drive system resonance frequency band can be detected, the combustion stability control can be performed while suppressing the occurrence of surge. For example, the air-fuel ratio is unnecessarily made rich, or the EGR amount (or unnecessarily) is increased. Since it is possible to suppress the reduction of the blow-by gas amount and the purge gas amount), it is possible to improve the fuel economy, drivability, exhaust characteristics and the like.

[0016]

An embodiment of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 4, as a means for detecting the operating condition / state of the engine 100, an air flow meter 1 for measuring the intake air flow rate and a pulse signal are generated at predetermined angles in synchronization with the rotation of the crankshaft and the camshaft. And a crank angle sensor 7 for detecting the crank position. Air flow meter 1, crank angle sensor 7
May be a conventionally known one.

As the pressure detecting means for the combustion chamber, the combustion chamber 10
A combustion pressure sensor 8 that directly measures the internal pressure via a piezoelectric element or the like is used. This may be installed for each cylinder,
Only one cylinder, or 1 for each bank for V engines
You may install one by one. In this embodiment, the case where the combustion pressure sensor 8 is installed for each cylinder will be described. By the way, as the combustion pressure sensor 8, a so-called washer type combustion pressure sensor integrated with the ignition plug 16 in which the washer of the ignition plug 11 is composed of a piezoelectric element or the like may be used.

The EGR valve control means includes an EGR valve 16 including a step motor or a proportional solenoid and capable of changing a lift amount (valve opening amount), and an exhaust system and an intake system via the EGR valve 16. An exhaust gas recirculation passage 15 capable of communicating with
It is configured to include. The EGR valve 16 has an input / output interface, an A / D converter, and an R, as shown in FIG.
The drive is controlled by a drive signal from a control unit 50 including an OM, a RAM, a CPU and the like.

As for the air-fuel ratio of the engine intake air-fuel mixture, the drive signal from the control unit 50 is used as the fuel amount injected and supplied by the fuel injection valve 12 provided for each cylinder in the manifold section 6 downstream of the intake manifold 5. It is controlled by adjusting based on. The control unit
In 50, the drive signal is sent to the fuel injection valve 12 so that the target air-fuel ratio can be obtained based on the air-fuel ratio detection signal from the oxygen sensor 17 provided in the exhaust passage.

Besides, a water temperature sensor (not shown) for detecting the cooling water temperature of the engine 100, an intake air temperature sensor (not shown) for detecting the intake air temperature, etc. are provided. The control unit 50 is provided with various calculating means and information extracting means, which will be described later, by software. FIG.
In the figure, 9 is a cylinder head, 13 is an intake valve, 14 is an exhaust valve, 2 is an auxiliary air passage for bypassing the throttle valve 4 at the time of idling, etc. to control the intake flow rate, 3
Is an auxiliary air control valve that controls the auxiliary air flow rate.

The flow chart of the control program executed by the control unit 50 will be described below. FIG. 6 is a general flow chart for combustion stability control. a is a block for detecting the combustion state for each combustion, b is a block for detecting the crank angle (θPmax) at which the pressure in the combustion chamber is maximum, and as an example of combining the blocks a and b, FIG. 7 shows a flowchart for calculating the indicated mean effective pressure in a certain crank angle section and θPmax in that section.

In FIG. 6, c is a block for calculating the combustion stability index based on the combustion state, and as one example, the processing shown in FIG. 8 described later is performed. Reference numeral d is a block that permits correction of the ignition timing, and performs processing as shown in FIG. 9 described later as an example. Reference numeral e is a block for performing ignition timing control based on the determination result of d, and as one example, the processing shown in FIG. 10 described later is performed.

Reference numeral f is a block for controlling the air-fuel ratio and the EGR amount and maintaining the desired combustion stability. For example, the process shown in FIG. 11 is performed. Here, the flowchart shown in FIG. 7 will be described. This processing is executed for each predetermined crank angle, for example, for each crank angle of 2 deg.

In this flowchart, the current crank angle is less than the first crank angle (AD start angle) shown in (a1) or the second crank angle (AD end angle) shown in (a2). If it is larger than), the process is terminated as it is, otherwise, AD start a
If the crank angle is between angle and AD end angle, the output of the combustion pressure sensor 8 at that time is A / D converted in (a3) and stored in the memory as combustion chamber pressure information (data) in (a4). .

When the necessary data are prepared (determined in a5), the AD start angle and AD end a are determined in (a6).
The average effective pressure (Pi) in a predetermined section between ngle is calculated. This value becomes a parameter indicating the combustion state that has a strong correlation with the generated torque. Then, in (b1), this AD
Within the predetermined section between the start angle and the AD end angle, the crank angle (θPma
x) is calculated.

Here, the method of calculating the average effective pressure is the well-known indicated mean effective pressure (Indicated mean effective pressure).
This is basically the same as the calculation method of pressure),
A predetermined section between D start angle and AD end angle
If the crank angle of the entire combustion cycle is 720 deg, the indicated average effective pressure is obtained. In the case where the crank angle section is limited as in the present embodiment, it is natural from the object of the present invention to include the combustion stroke in which the influence of combustion fluctuation appears remarkably, and it does not affect combustion fluctuation. Limiting the crank angle section so as not to include the intake and exhaust strokes can save memory capacity and simplify arithmetic processing. Further, as the combustion pressure sensor 8,
When a sensor to which a bias component is added is used, in order to remove the influence of this bias, this crank angle section may be a section having the same width in the front and rear with the compression top dead center as the center.

Next, the flow chart shown in FIG. 8 will be described. This process is performed every predetermined time, for example, 10 msec.
It is executed every time. The amount of fluctuation of the combustion state obtained from the time-series data of the combustion state detected in (a6) is used as a stability index. In this embodiment, the magnitude of the fluctuation in the frequency band including the resonance frequency of the drive system is particularly used. It is used as an indicator.

(C1) is a band-pass filter having a characteristic of passing only a signal having a frequency near the resonance frequency of the vehicle drive system and removing the other portions, and the control unit 50 functions as a digital filter by software. Can be prepared for. This digital filter process may be a known process. However, since the resonance frequency of the drive system changes depending on the value of the transmission gear ratio, the characteristic (extraction frequency band) of the bandpass filter is changed according to the current transmission ratio, or a frequency that can support all transmission ratios. It is desirable to be able to cover the band. Since the filter processing time is relatively long, it is preferable to provide the former function of changing the extraction frequency band in terms of processing time reduction.

The combustion state information extracted as the information of the drive system resonance frequency band by the bandpass filter processing in (c1) is then subjected to a moving average in (C2). The combustion state varies approximately probabilistically, and it is not possible to judge whether the current air-fuel ratio or EGR amount is proper only with one-time data, and it is necessary to judge from a tendency such as distribution. In this embodiment, the tendency of the combustion state is grasped by signal processing called moving average, and this is used as an index (S) of combustion stability. In this case, the better the combustion stability,
The value calculated here becomes smaller.

If the combustion stability index (S) is mainly the magnitude of combustion fluctuation in the same frequency band as the drive system resonance frequency band as in this embodiment, the surge torque level is Fluctuations in the frequency range (that is, the drive system resonance frequency band) can be detected, and combustion stability control can be performed while suppressing the occurrence of surges, so that the air-fuel ratio is unnecessarily enriched or the EGR amount is unnecessarily increased. The fuel consumption, drivability, and exhaust characteristics can be improved. Further, since it is sufficient to detect the combustion fluctuation in a relatively narrow frequency band, it is possible to save the calculation processing time and the memory capacity. Note that the combustion stability index (S) is set to the magnitude of the combustion fluctuation in the same frequency band as the drive system resonance frequency band, for combustion stabilization control or unless the calculation processing time or memory capacity is saved. It does not have to be the main indicator.

Next, the flow chart shown in FIG. 9A will be described. This process is an example of the invention according to claims 1 and 2, and is executed for each combustion. First,
In (d1), the average effective pressure (Pi), which is a parameter indicating the combustion state calculated in (a6) of FIG. 7, is read,
In (d2), the average value of this combustion state (Pi) (AP
i) is calculated. This APi is, for example, the past combustion state (P
It is a value estimated from the moving average of i) or the operating conditions at that time.

At (d3), "APi-Pi" and a predetermined value d
The size of Pi (> 0) is compared. Then, "APi-P
If "i" is smaller than dPi, correction of the ignition timing is permitted in (d4). On the other hand, when "APi-Pi" is greater than or equal to dPi, the correction of the ignition timing is not permitted in (d5), and the present flow ends. Here, in the processing of (d3), the combustion state is deteriorated due to the leaning of the air-fuel ratio and the increase of the EGR amount, and therefore, the combustion state that is not suitable for the MBT control of the ignition timing is detected. is there.

As shown in FIG. 12, the distribution of the combustion state (Pi) is different between when the combustion state is good and when it is bad, and when the combustion state is bad, the distribution spreads and combustion with a small Pi value occurs. . For combustion in which the value of Pi is smaller than a certain fixed value, the flowchart of FIG. 9A is executed in order to prevent correction of the ignition timing (MBT control) based on θPmax in the combustion. is there. That is, when the ignition timing is feedback-controlled (that is, the MBT control of the ignition timing) so that the crank angle (θPmax) that maximizes the combustion chamber pressure matches the target crank angle that maximizes the output torque, Abnormal combustion (combustion with a small value of Pi), the above θPm
Although ax is greatly deviated from the target crank angle, normal ignition timing control becomes impossible, and fuel efficiency, drivability, and exhaust performance deteriorate, but this can be prevented.

Next, the flow chart shown in FIG. 9B will be described. This processing is an example of the invention according to claims 3 and 4, and is executed for each combustion. First, (d
In 7), the combustion stability index (S) calculated in FIG. 8 is read, and the target stability (SL) is read by referring to the map or the like stored for each operating condition. Then, in (d8), |
S-SL | is compared with the magnitude of a predetermined value dS (> 0). Here, as dS, for example, a value of 10% of SL is used.

When | S-SL | is smaller than dS, correction of the ignition timing is permitted (d9), and | S-SL |
If is greater than or equal to dS, the correction of the ignition timing is not permitted (d10), and the present flow ends. Note that (d8)
In the process (1), it is determined whether the combustion stability is near the target combustion stability. In the present embodiment, the idea that the MBT control of the ignition timing is performed only on the basis of θPmax in the combustion of the air-fuel ratio or the EGR amount that is close to the target combustion stability (in other words, leaning of the air-fuel ratio and 13 is based on the idea that when the combustion state is fluctuating due to the fluctuation of the EGR amount, the case where the control timing hunting is likely to occur when the MBT control of the ignition timing is performed is shown in FIG. As described above, when the combustion stability exceeds a certain range, or when the combustion stability does not reach the certain range, the ignition timing is not corrected based on θPmax, so that rotation hunting occurs. It is intended to prevent the above and improve the stability of the engine.

Next, the flowchart of FIG. 10 will be described. This process is a flow for correcting the ignition timing, and is executed for each combustion. First, in (e1), read the crank angle θPmax that maximizes the pressure in the combustion chamber,
The target crank angle TθPmax at which the output torque of the engine is maximized is read in (e2), and these magnitudes are compared in (e3).

Here, TθPmax may be a fixed value determined in advance, a value stored in a map or the like for each operating condition, or may be calculated for each operating condition. As a result of comparison in (e3), if θPmax is larger than TθPmax, the ignition timing is advanced by a predetermined amount (e4), and then this flow is ended. On the other hand, if θPmax is equal to or less than TθPmax, the process proceeds to (e5).

At (e5), θPmax <TθPmax is discriminated. If YES, the ignition timing is retarded by a predetermined amount (e
6) Then, this flow ends. On the other hand, in the case of NO, θPmax = TθPmax, and the present flow is directly terminated without correcting the current ignition timing. Continued to,
The flowchart shown in FIG. 11 will be described. The process is an example of combustion stabilization control, and is executed for each combustion.

First, the combustion stability index (S) calculated in the flowchart of FIG. 8 is read in (f1), and the target value (SL, slice level) of the stability is read in (f2). This SL may be a fixed value determined in advance,
The value may be stored in a map or the like for each operating condition, or may be calculated for each operating condition. And
In (f3), the magnitudes of S and SL are compared. If S is larger than SL, the EGR amount is reduced by a predetermined amount (f4), and S is SL.
If it is below, the EGR amount is increased by a predetermined amount (f5), and the present flow ends.

As a result, the stability S is maintained at the same level as the target value SL. Thus, according to the present embodiment,
By controlling the air-fuel ratio or the EGR amount (or the canister purge amount [evaporation amount of evaporated fuel], etc.), in addition to controlling the internal combustion engine within a desired degree of stability, correction control of ignition timing is performed. , Lean air-fuel ratio and EG
For combustion in which the combustion stability greatly deviates from the target stability due to an increase in the R amount, even if the ignition timing is corrected based on the θPmax of the combustion, the effect cannot be expected, but is rather good. Output torque is not obtained,
Combustion that is not appropriate for such ignition timing correction control will be detected based on the combustion state, which will lead to deterioration of fuel efficiency and deterioration of drivability and exhaust performance. Since the correction control of the ignition timing is not performed, a good output torque can be obtained even if the air-fuel ratio or the EGR amount is changed near the combustion stability limit, thereby improving fuel efficiency and drivability and exhaust gas. The performance can be maintained at the same time.

In this embodiment, the control amount for changing the state of the engine intake air-fuel mixture has been described by using the air-fuel ratio or the EGR amount as a representative, but the blow-by gas amount, the purge gas amount introduced from the canister, etc. It can also be applied when adjusting to obtain a desired combustion stability.

[0042]

As described above, according to the first aspect of the present invention, by controlling the control amount (for example, the air-fuel ratio or the EGR amount) that changes the state of the engine intake air-fuel mixture, the desired amount can be obtained. When the ignition timing correction control is performed in addition to the control of the internal combustion engine within the stability of, the combustion stability greatly deviates from the target stability due to the lean air-fuel ratio and the increase in the EGR amount. For combustion, the ignition timing correction control for that combustion is not performed, so
Even if the air-fuel ratio or the EGR amount is changed near the combustion stability limit, a good output torque can be obtained, and it is possible to achieve both improved fuel efficiency and drivability / exhaust performance.

According to the invention described in claim 2, the first
Since the ignition timing correction permitting means is means for permitting correction of the ignition timing when the detected combustion state is within a predetermined range with respect to the average value thereof, the ignition timing correction permitting means is relatively simple and quick. In addition, it is possible to determine whether to permit the ignition timing correction, thereby improving the control responsiveness. According to the invention of claim 3, instead of the first ignition timing correction permitting means of claim 1, the ignition timing correction is performed when the calculated combustion stability index is within a predetermined range. Since it is configured to permit the ignition timing correction, it is possible to make a more accurate determination of permission of the ignition timing correction as compared with the invention described in claim 1, and thus it is possible to improve the control accuracy.

According to the invention of claim 4, the second
Since the ignition timing correction permission means is configured as means for permitting the correction of the ignition timing when the calculated combustion stability index is within the predetermined range with respect to the target value, the ignition timing correction permission means has a relatively simple structure and high accuracy. It is possible to determine whether to permit various ignition timing corrections. According to the fifth aspect of the present invention, the combustion state detecting means is based on the rotational position detecting means for detecting the rotational position of the crankshaft or the camshaft, and the combustion chamber pressure detected by the combustion chamber pressure detecting means. ,
The average effective pressure calculating means for calculating the average effective pressure in the predetermined rotation section is included, and the combustion state can be detected with high accuracy with a relatively simple configuration while saving processing time, memory capacity, and the like.

According to the sixth aspect of the invention, since the combustion stability index is mainly the magnitude of combustion fluctuation in the same frequency band as the drive system resonance frequency band, it represents the surge torque level. Since fluctuations in the frequency range (that is, the drive system resonance frequency band) can be detected, combustion stability control can be performed while suppressing the occurrence of surge, and thus the air-fuel ratio is unnecessarily made rich or the EGR amount (or unnecessarily) is increased. Since it is possible to suppress the reduction of the blow-by gas amount and the purge gas amount), it is possible to improve the fuel economy, drivability, and exhaust characteristics.

[Brief description of drawings]

FIG. 1 is a block diagram corresponding to the invention described in claim 1.

FIG. 2 is a block diagram corresponding to the invention of claim 3.

FIG. 3 is a block diagram corresponding to the invention of claim 5.

FIG. 4 is a diagram showing an overall configuration according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of a control unit according to the embodiment.

FIG. 6 is a general flowchart of the above embodiment.

FIG. 7 is a flowchart for explaining combustion state detection and θPmax detection according to the embodiment.

FIG. 8 is a flowchart illustrating calculation of a combustion stability index according to the above-described embodiment.

FIG. 9A is a flowchart illustrating an ignition timing correction permission control (corresponding to a first ignition timing correction permission means) of the embodiment. 9B is a flowchart illustrating an ignition timing correction permission control (corresponding to second ignition timing correction permission means) by another method.

FIG. 10 is a flowchart for explaining ignition timing correction control according to the above embodiment.

FIG. 11 is a flowchart illustrating combustion stabilization control according to the above embodiment.

FIG. 12 is a diagram showing a distribution of a combustion state.

FIG. 13 is a diagram showing changes in the combustion stability index.

[Explanation of symbols]

 1 Air flow meter 7 Crank angle sensor 8 Combustion pressure sensor 10 Combustion chamber 11 Spark plug 12 Fuel injection valve 15 Exhaust gas recirculation passage 16 EGR valve 17 Oxygen sensor 50 Control unit 100 Engine

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location F02D 41/04 305 J 43/00 301 B EN M 45/00 368 T F02M 25/07 550 R 25/08 301 U F02P 5/15

Claims (7)

[Claims] 1. A combustion chamber pressure detecting means for detecting a pressure in a combustion chamber of an internal combustion engine; a combustion state detecting means for detecting a combustion state for each combustion based on the detected combustion chamber pressure; A combustion stability index calculating means for calculating a combustion stability index based on the combustion state; and a θPmax detecting means for detecting a crank angle (θPmax) at which the detected combustion chamber pressure becomes maximum in one combustion stroke, When the detected combustion state is within the predetermined range,
A first ignition timing correction permitting means for permitting correction of the ignition timing; and a target crank at which the output torque of the engine becomes maximum when the ignition timing correction is permitted by the first ignition timing correction permitting means. The first ignition timing correction means for correcting the ignition timing and the control amount for changing the state of the air-fuel mixture to be supplied to the engine are adjusted based on the calculated combustion stability index so as to match the angle. A combustion stability control device for an internal combustion engine, comprising: a combustion stability control means for realizing combustion stability; 2. The first ignition timing correction permission means is means for permitting correction of ignition timing when the detected combustion state is within a predetermined range with respect to its average value. The combustion stability control device for an internal combustion engine according to claim 1, characterized in that: 3. A combustion chamber pressure detection means for detecting a pressure in a combustion chamber of an internal combustion engine; a combustion state detection means for detecting a combustion state for each combustion based on the detected combustion chamber pressure; A combustion stability index calculating means for calculating a combustion stability index based on the combustion state; and a θPmax detecting means for detecting a crank angle (θPmax) at which the detected combustion chamber pressure becomes maximum in one combustion stroke, Second ignition timing correction permission means for permitting correction of ignition timing when the calculated combustion stability index is within a predetermined range, and ignition timing correction is permitted by the second ignition timing correction permission means Based on the calculated combustion stability index, second ignition timing correction means for correcting the ignition timing so that the θPmax matches the target crank angle at which the output torque of the engine becomes maximum. A combustion stability control device for an internal combustion engine, comprising: a combustion stability control unit that adjusts a control amount that changes the state of the air-fuel mixture supplied to the engine, and that achieves a desired combustion stability. . 4. The second ignition timing correction permission means is means for permitting correction of the ignition timing when the calculated combustion stability index is within a predetermined range with respect to a target value. The combustion stability control device for an internal combustion engine according to claim 3. 5. The combustion state detecting means detects a rotational position of a crankshaft or a camshaft, and an average of predetermined rotation intervals based on the combustion chamber pressure detected by the combustion chamber pressure detecting means. An average effective pressure calculation means for calculating an effective pressure, and a combustion stability control device for an internal combustion engine according to any one of claims 1 to 4. 6. The combustion stability index mainly uses the magnitude of combustion fluctuation in the same frequency band as the drive system resonance frequency band, as a main index. A combustion stability control device for an internal combustion engine according to claim 1. 7. The control amount for changing the state of the air-fuel mixture supplied to the engine is an air-fuel ratio, an EGR amount or a canister purge gas amount, according to any one of claims 1 to 6. A combustion stability control device for an internal combustion engine as described above.