JPH109014A - Combustion control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of noise by providing a means for calculating combustion noise to correct at least one of a fuel injection rate and an ignition timing so as to keep the noise at an allowable value or less. SOLUTION: An operating condition is calculated by an air flow signal and the signal of a crank angle sensor in S1, a fundamental ignition timing and a fundamental fuel injection rate are calculated in an operating condition in S2, it is judged whether stoichiometric control is carried out or not, and lean control is carried out or not in S3, and a fuel injection rate and an ignition timing when lean control is carried out is calculated in S4. Steady judgment is carried out on the basis of a TVO signal in S7, and combustion noise is calculated from engine speed and volume efficiency in S9. Roughness is judged in S8, the fuel injection rate is increased at the time of an allowable value or more, the fundamental ignition timing is delayed so as to improve stability. Combustion noise is judged at the time of the allowable value or less. It is judged that the fuel injection rate and the referential ignition timing are not changed since A/F is not made in a lean condition at the time of a judgment value or more, and the A/F can be made in the lean condition at the time of the judgment value or less. As a result, the fuel injection rate is reduced, the fundamental ignition timing is advanced so as to approach a stable limit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combustion control device for an internal combustion engine.

[0002]

2. Description of the Related Art A conventional combustion control apparatus for an internal combustion engine is disclosed in Japanese Patent Application Laid-Open No. 60-62661. This conventional example is shown in FIG.
As shown in the figure, the fuel injection amount and the ignition timing are corrected based on the detection result of the roughness sensor 99. One example of a specific control method will be described with reference to FIG. The initial setting points of A / F and ADV are determined according to the operating conditions. This is from the stability limit in consideration of the fuel injection amount and the variation in parts.
The point is that a margin (ΔA / F) of / F is secured. On the other hand, when the roughness can be detected, the A / F is made lean for the purpose of improving fuel efficiency and reducing NO _x (AD
V is the best point of fuel economy, MBT setting). Finally, in consideration of roughness detection accuracy, control is performed to a point where the stability is slightly better than the stability limit (control point). Thus, in the conventional example, the roughness is detected and the A / F and ADV are controlled to the stability limit (this is called lean limit control).

[0003]

However, such a conventional combustion control apparatus for an internal combustion engine does not calculate the combustion noise when performing the lean limit control.
As shown in FIG. 4, as the A / F is made leaner or the ADV is advanced, the combustion noise (CPL: a parameter representing the magnitude of the combustion noise) increases. For this reason, there is a problem that the combustion noise exceeds an allowable value depending on the operating conditions and noise is generated.

The present invention has been made in view of such a conventional problem. When performing lean limit control,
The combustion noise is calculated, and even if the roughness is lower than the stability limit, if the combustion noise is higher than the allowable value, the lean limit control is stopped, and the control is performed so that the combustion noise becomes lower than the allowable value. The purpose is to solve the problem.

[0005]

SUMMARY OF THE INVENTION The present invention has a means for detecting an operating state of an engine in an internal combustion engine, a steady state determining means for determining a steady state, and a roughness detecting means for detecting an engine roughness. A combustion control device for controlling at least one of a fuel injection amount and an ignition timing so that the roughness becomes a stability limit, comprising means for calculating a combustion noise, wherein the combustion noise is equal to or less than an allowable value. In such a configuration, means for correcting at least one of the fuel injection amount and the ignition timing is provided.

[0006] Further, according to the present invention, the means for calculating the combustion noise is configured to predict from the volumetric efficiency and the engine speed.

Further, according to the present invention, the means for calculating the combustion noise has a means for calculating the combustion period, and is configured to predict from the combustion period and the volumetric efficiency.

Further, the present invention has a structure in which means for detecting the in-cylinder pressure is provided, and the combustion period is predicted from the in-cylinder pressure.

Further, the present invention has a configuration in which the combustion period is predicted from the roughness of the engine.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a first embodiment of the present invention. First, the configuration will be described.
The air flow meter 12 detects the intake air amount, the TVO sensor 13 detects the throttle opening, calculates the engine speed from the signal of the crank angle sensor 14, and the ECU 15 calculates the fuel injection amount and ignition based on the signal. Calculate the timing. The fuel of the calculated fuel injection amount is injected from the injector 16, and a spark is ignited by the spark plug 17 at the calculated ignition timing.

FIG. 5 shows a control flow. In step 1 (hereinafter referred to as "S1"), operating conditions are calculated from the airflow signal and the signal of the crank angle sensor. Next, S
A basic ignition timing and a basic fuel injection amount are calculated from the operating conditions calculated in step (2). In S3, it is determined whether to perform the stoichiometric control or the lean control based on the operating conditions. In S4, the fuel injection amount and the ignition timing for performing the lean control are calculated. T at S7
The steady state is determined based on the VO signal. At S8, a roughness determination is performed. In S9, the combustion noise is calculated. In S5, the fuel injection amount and the ignition timing at the lean control point are calculated from the results of the roughness and the combustion noise. Finally, fuel injection and ignition are performed with the fuel injection amount and ignition timing calculated in S6.

Next, the operation will be described. FIG. 6 shows A / F and ADV settings during lean control. First, the condition is satisfied,
When performing the lean control, the A / F of the base determined by the operating conditions (A / F with the A / F allowance (ΔA / F) secured)
F) Control to the ADV set point (initial set point). Next, when the operation state is stable, the A / F is made lean while detecting the roughness, the ADV is advanced, and the stability limit is set (lean limit control point). However, A / F
Lean, the volumetric efficiency (ηc) increases and the pressure in the combustion chamber increases, so that the combustion noise (CPL) increases.
Therefore, as shown in FIG. 7, depending on the operating conditions, when the engine is leaned to the lean limit control point, the CPL exceeds the allowable value.

Here, CPL is ηc and engine speed N
(FIG. 7), it is known that the CPL is predicted from ηc and N, and by controlling the CPL to be equal to or less than the allowable value, an increase in combustion noise can be prevented.

FIG. 8 shows a schematic control flow of the first embodiment. At S11, the operation conditions are calculated. In S12, the basic ignition timing (at the time of stoichiometric control) is calculated. In S13, the basic fuel injection amount (at the time of stoichiometric control) is calculated. In S14, it is determined whether to perform the stoichiometric control or the lean control according to the operating conditions. In S15, the fuel injection amount and the ignition timing at the time of the lean operation are calculated. At S16, a steady state determination is performed. LLC (lean limit control) is performed in a steady state (in an unsteady state, LLC is not performed because it is difficult to accurately detect roughness). In S17, the combustion noise is calculated. The roughness is determined in S18, and when the roughness is equal to or more than the allowable value, the fuel injection amount is increased in S19, and the ADV is retarded to improve the stability. If it is less than the allowable value, the combustion noise is determined in S1a. A /
Since F cannot be made lean, the fuel injection amount and ADV are not changed. If the value is equal to or less than the determination value, the fuel injection amount is reduced in S1b to advance the ADV to approach the stability limit.

Next, a detailed control flow will be described. S1
1 is shown in FIG. In S21, the intake air amount Q is calculated based on the airflow signal. In S22, the engine speed N is calculated. In S23, a basic fuel injection amount TP (at the time of stoichiometric control) is calculated. FIG. 10 shows the flow of S12.
In S31, TP and N are called, and in S32, the basic ignition timing BADV (at the time of stoichiometric control) is looked up from the map of FIG. The basic fuel injection amount in S13 uses the TP in S23. FIG. 12 shows the flow of S14. TP at S41
0, call TVO (throttle opening). T at S42
It is determined that P> α, and when α is greater than or equal to α, a high load range is set, so stoichiometric control is performed. When TP is equal to or smaller than α, the process proceeds to S43. S
When ΔTVO (the amount of change in TVO) is equal to or larger than β in 43, rapid acceleration is performed, so that stoichiometric control is performed. If β or less, the process proceeds to S44 to perform lean control. In S44, the lean basic fuel injection amount calculation coefficient KLTP (0 <KLTP <1) is set to KL.
Look up from the TP map (FIG. 14). S45
Calculates the lean basic fuel injection amount LTP. In S46, the lean basic ignition timing LADV is mapped to the LADV map (FIG. 1).
Look up from 5). FIG. 13 shows the flow of S16. At step S51, TVO is called. In S52, ΔTVO and γ are compared. If it is more than γ, it is not steady, so LLC
(Lean limit control) is not performed. If the value is equal to or smaller than γ, it is determined to be steady, and LLC is performed in S53. FIG. 16 shows the flow of S17. As shown in FIG. 17, the combustion noise CPL has a correlation with the volumetric efficiency ηc. Also, the higher the engine speed, the higher the CPL. Therefore, CPL can be predicted from ηc and N. In S61, the intake air amount Q and the engine speed N are called. In S62, an intake air amount QP per one rotation of the engine is calculated. QP in S63
The volume efficiency ηc is looked up from the table of FIG. In S64, the CPL is looked up from ηc and N using the map of FIG. FIG. 20 shows the flow of S18 to S1b. At S71, the engine speed N is called.
In S72, the rotation fluctuation rate dN is calculated as the roughness.
(The calculated average effective pressure Pi is calculated as roughness.
It is also possible to use a surge torque obtained by extracting the fluctuation rate of i or the fluctuation of Pi from 3 to 7 Hz. In step S73, the roughness is determined. When dN> b, the stability exceeds the allowable value, and the stability is improved in S74 to S77. FIG.
1 shows a low load condition, and FIG. 22 shows A / F and A under a high load condition.
3 shows a DV map. The low load burns more slowly than the high load, and the MBT has a steep slope. Therefore, the ratio between the correction of the fuel injection amount (ΔA / F) and the correction of the ADV (ΔADV) when performing the LLC is changed according to the operating conditions. In the control, the LLC correction injection amount HTP and the LLC correction ignition timing HADV are given in a map of TP and N. FIG. 2 at S74
The LLC correction injection amount HTP is looked up from the map 3. In S75, the LLC fuel injection amount LLCTP is calculated (the injection amount is increased). At S76, LLC is obtained from the map shown in FIG.
The corrected ignition timing HADV is looked up. L in S77
The LC ignition timing LLCADV is calculated (ADV is retarded). When a ≦ dN ≦ b in S73, it is determined that the vehicle is near the stability limit, and the fuel injection amount and the ADV are left as they are. When dN <a in S73, since the stability is equal to or less than the allowable value, the aim is to make the A / F lean. When CPL> c, C
PL is determined to be near the allowable value, and the fuel injection amount and A
DV is left as it is. When CPL ≦ c, the CPL is below the allowable value, so that it is determined that the A / F can be made leaner, and the fuel injection amount is reduced in AD at S7a to S7d to adjust the ADV.
To approach the stability limit.

By performing the above control, L
Even during the LC control, the CPL can be kept below the allowable value.

As described above, in the first embodiment,
The engine speed and the volumetric efficiency are calculated, and the combustion noise is calculated from the calculated engine speed and the volumetric efficiency. Since the fuel injection amount and the ignition timing are controlled so that the calculated combustion noise becomes equal to or less than the allowable value, it is possible to prevent the generation of engine noise due to an increase in the combustion noise during the lean burn operation, which has conventionally occurred.

Next, a second embodiment of the present invention will be described.

The second embodiment is characterized in that the combustion noise is calculated from the volumetric efficiency and the combustion period. This configuration is shown in FIG. The second embodiment is different from the first embodiment (FIG. 1) in that an in-cylinder pressure sensor 18 is provided.
Is added. FIG. 26 shows an in-cylinder pressure waveform with respect to the crank angle. Here, a method of calculating the heat generation rate from the in-cylinder pressure waveforms at the time of firing and motoring, and calculating the combustion period from the ratio of the heat generation rate is known and generally used. In the second embodiment, a combustion noise (CPL) is calculated using this combustion period. As shown in FIG. 27, when ηc is constant, CPL
It is known from experiments that the shorter the combustion period MB is, the higher the value is. Therefore, the CPL can be obtained from a map of ηc and MB as shown in FIG. The control flow is
This is equivalent to the embodiment. However, the method of calculating the combustion noise in S64 of FIG. 16 is different. Figure 2 shows the flow of CPL calculation
9 In step S81, the in-cylinder pressure waveform is called. In S82, the combustion period MB is calculated. In step S83, ηc is called. S8
In step 4, the CPL is looked up from the map of FIG. 28 based on ηc and MB. By performing the above control, CPL can be calculated.

Next, a third embodiment will be described.

The configuration of the third embodiment is the same as that of the first embodiment (FIG. 1). In the third embodiment, the combustion noise is calculated from the combustion period and the volumetric efficiency as in the second embodiment. However, the third embodiment is characterized in that the combustion period is predicted from the stability. FIG.
As shown in the figure, the stability (rotation fluctuation rate dN) and the combustion period M
B has a correlation. The faster the combustion, the better the stability.
N becomes smaller. Thus, the combustion period can be predicted from the stability. The control flow is the same as in the second embodiment. The method of calculating the combustion period is different. FIG. 31 shows a flow for S82 of the second embodiment. At S91, the rotation fluctuation rate dN (S72) is called. In S92, the MB is looked up from the table of FIG. CPL can be calculated by the above control. As described above, in the present control, by predicting the CPL and correcting the A / F and ADV controls by the lean limit control, the CPL can be suppressed to the allowable value or less as shown in FIG.

As described above, in the second and third embodiments, the combustion period and the volumetric efficiency are calculated, and the combustion noise is calculated from the calculated combustion period and the volumetric efficiency. Since the fuel injection amount and the ignition timing are controlled so that the calculated combustion noise becomes equal to or less than the allowable value, it is possible to prevent the generation of engine noise due to an increase in the combustion noise during the lean burn operation, which has conventionally occurred.

[0024]

As described above, according to the present invention, the configuration is provided with a means for detecting the operating state of the engine,
A means for detecting engine roughness, wherein at least one of the fuel injection amount and the ignition timing is set so as to reach the stability limit.
In the combustion control device for controlling the combustion noise, at least one of the fuel injection amount and the ignition timing is corrected so that the combustion noise is equal to or less than an allowable value. Can be suppressed to below an allowable value, and generation of noise can be prevented.

Further, in each of the embodiments, in addition to the above-mentioned common effects, the following effects are further obtained. In the second embodiment, since the combustion noise is predicted by calculating the combustion period using the in-cylinder pressure sensor, the combustion noise can be accurately predicted.

In the third embodiment, since the combustion period is calculated from the stability of the engine without using the in-cylinder pressure sensor, the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional example.

FIG. 3 is a diagram illustrating lean limit control.

FIG. 4 is a diagram illustrating the relationship between CPL for A / F and ADV.

FIG. 5 is a diagram illustrating the configuration of the present control.

FIG. 6 is a diagram illustrating a change in CPL due to lean limit control.

FIG. 7 is a diagram illustrating the relationship between ηc and CPL.

FIG. 8 is a flowchart illustrating the present control.

FIG. 9 is a flowchart of operation condition calculation.

FIG. 10 is a flowchart of basic ignition timing calculation.

FIG. 11 is a BADV characteristic diagram.

FIG. 12 is a flowchart of stoichiometric / lean control determination.

FIG. 13 is a flowchart of a steady state determination.

FIG. 14 is a KLTP characteristic diagram.

FIG. 15 is a LADV characteristic diagram.

FIG. 16 is a flowchart of CPL calculation.

FIG. 17 is a diagram illustrating the relationship between ηc and CPL.

FIG. 18 is a diagram illustrating the relationship between QP and ηc.

FIG. 19 is a CPL characteristic diagram.

FIG. 20 is a flowchart of LLC.

FIG. 21 is a diagram illustrating LLC control under a low load condition.

FIG. 22 is a diagram illustrating LLC control under a high load condition.

FIG. 23 is an HTP characteristic diagram.

FIG. 24 is a HADV characteristic diagram.

FIG. 25 is a configuration diagram of a second embodiment of the present invention.

FIG. 26 is a diagram illustrating an in-cylinder pressure waveform.

FIG. 27 is a diagram illustrating the relationship between MB and CPL.

FIG. 28 is a CPL characteristic diagram.

FIG. 29 is a flowchart of CPL calculation according to the second embodiment.

FIG. 30 is a diagram illustrating the relationship between dN and MB.

FIG. 31 is a flowchart of MB calculation according to the third embodiment.

FIG. 32 is a diagram illustrating the effect of the present control.

[Explanation of symbols]

 11 Internal combustion engine 12 Air flow meter 13 TVO sensor 14 Crank angle sensor 15 ECU 16 Injector 17 Spark plug 18 In-cylinder pressure sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display F02P 5/153

Claims (5)

[Claims] 1. An internal combustion engine, comprising: means for detecting an operation state of the engine; means for determining steady state; means for detecting roughness of the engine; means for detecting roughness of the engine; A combustion control device for controlling at least one of a fuel injection amount and an ignition timing so as to reach a stability limit, comprising means for calculating a combustion noise, and a fuel injection device for controlling the fuel injection so that the combustion noise becomes an allowable value or less. A combustion control device for an internal combustion engine, wherein at least one of an amount and an ignition timing is corrected. 2. The combustion control device for an internal combustion engine according to claim 1, wherein the calculation of the combustion noise is predicted from volumetric efficiency and engine speed. 3. The combustion control device for an internal combustion engine according to claim 1, further comprising means for calculating a combustion period, wherein the calculation of the combustion noise is predicted from the combustion period and volumetric efficiency. 4. The combustion control apparatus for an internal combustion engine according to claim 3, further comprising means for detecting an in-cylinder pressure, wherein the combustion period is predicted from the in-cylinder pressure. 5. The combustion control device according to claim 3, wherein the combustion period is predicted from engine roughness.