JPH11336590A - Fuel supply controlling device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel supply controlling device capable of enhancing fuel economy by leaning an air-fuel ratio as high as possible within the range of ensuring stability of engine rotation during idling condition. SOLUTION: By multiplying an average value DMSBAVE of variation amounts of engine rotation DMSSLB by threshold factors α(>1) and β(<1), first thresholds α × DMSBAVE and β× DMSBAVE are determined, and then second thresholds MSLEAN 1 and MSLEAN 2 are calculated in accordance with an absolute pressure within an intake pipe and the like. In accordance with a relation in magnitude between a variation amount of rotation DMSSLB and these thresholds MSLEAN1 and MSLEAN2, a lean burn correcting factor KLSAF is calculated. These thresholds are set to be smaller in an idling condition of engine than those in conditions other than the idling condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an internal combustion engine which detects a combustion state of the internal combustion engine and controls a fuel amount supplied to the engine according to the detected combustion state.
In particular, the present invention relates to a fuel supply control device for a direct injection internal combustion engine that directly injects fuel into a combustion chamber.

[0002]

2. Description of the Related Art It is widely known to set an air-fuel ratio to a lean side in order to improve fuel efficiency of an internal combustion engine, or to perform exhaust gas recirculation in order to improve exhaust gas characteristics. However, if the air-fuel ratio is excessively lean or excessive exhaust gas recirculation is performed, the combustion of the engine becomes unstable and the operability is deteriorated.Therefore, the combustion state of the engine is detected based on the rotation fluctuation amount of the engine. Conventionally, there has been known a method of correcting the fuel supply amount in an increasing direction when the amount exceeds a predetermined upper threshold value, and correcting the fuel supply amount in a decreasing direction when the amount falls below a predetermined lower threshold value (JP-A-8-284707). No.).

[0003]

An in-cylinder injection type internal combustion engine in which fuel is directly injected into a combustion chamber has an air-fuel ratio considerably leaner than a stoichiometric air-fuel ratio (for example, A / F = about 40). Also, since ignition is possible, it is possible to operate at such a lean air-fuel ratio even in the idle operation state of the engine.

However, when the air-fuel ratio is changed to the lean direction in the idling operation state, the increase amount of the rotation fluctuation is larger than in the operation state other than the idling state. In this state, there is a problem that the fuel supply amount tends to be insufficient, and the rotation fluctuation amount of the engine increases.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and the air-fuel ratio is maximized as long as the stability of the engine rotation can be ensured in an idling operation state.
An object of the present invention is to provide a fuel supply control device capable of improving fuel efficiency.

[0006]

According to a first aspect of the present invention, there is provided a rotation fluctuation detecting means for detecting a rotation fluctuation amount of an internal combustion engine, and detecting the detected rotation fluctuation amount with a predetermined threshold value. An internal combustion engine comprising: a correction unit that compares and corrects a fuel amount supplied to the engine according to the comparison result; and a fuel injection unit that directly injects the fuel amount corrected by the correction unit into a combustion chamber of the engine. In the fuel supply control device, the correction means sets the predetermined threshold to a value smaller than a value when the engine is in an idle state when the engine is in an idle state.

According to this configuration, when the engine is in the idle state, the predetermined threshold value to be compared with the detected rotation fluctuation amount is set to a value smaller than the value when the engine is not in the idle state. When it is in the state, the rotation fluctuation amount is more likely to exceed the upper threshold value than in the other operation state, or it is hard to fall below the lower threshold value, and the fuel supply amount is easily corrected in the increasing direction, or in the decreasing direction. It is difficult to correct. As a result, the air-fuel ratio is made lean within a range where rotation stability can be ensured in the idling state of the engine, and the fuel efficiency can be improved.

According to a second aspect of the present invention, there is provided a rotation fluctuation detecting means for detecting a rotation fluctuation amount of an internal combustion engine, comparing the detected rotation fluctuation amount with a predetermined threshold value, and operating the engine in accordance with the comparison result. A fuel supply control device for an internal combustion engine, comprising: a correction unit for correcting the amount of fuel to be supplied; and a fuel injection unit for directly injecting the fuel amount corrected by the correction unit into a combustion chamber of the engine. Is smaller than a predetermined idling determination rotation speed, and the engine is in a predetermined low load state, so that the engine is in an idling state. When the engine is determined to be in an idle state, the predetermined threshold is set to a value higher than the value in the idle determination rotation speed when the engine is not in the idle state. And sets the the value.

According to this structure, the predetermined threshold value to be compared with the detected rotation fluctuation amount is set according to the engine speed,
When the engine is in the idling state, the predetermined threshold value is set to a value smaller than the value of the idling determination speed when the engine is not in the idling state, so that the same effect as the first aspect of the invention is obtained. That is, when in the idling operation state, the rotation fluctuation amount is more likely to exceed the upper threshold value than in the other operation state, or hardly falls below the lower threshold value, and the fuel supply amount is easily corrected in the increasing direction, Alternatively, since it is difficult to correct in the decreasing direction, the air-fuel ratio is made lean within a range in which the rotation stability can be ensured in the idling operation state of the engine, and the fuel efficiency can be improved.

[0010]

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

FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter referred to as “engine”) and a fuel supply control device therefor according to an embodiment of the present invention. Is arranged. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3, outputs an electric signal corresponding to the opening of the throttle valve 3, and supplies it to an electronic control unit (hereinafter referred to as “ECU”) 5. .

A fuel injection valve 6 as a fuel injection means is provided for each cylinder so as to inject fuel directly into the combustion chamber of each cylinder. Each injection valve is connected to a fuel pump (not shown) and is connected to the ECU 5. Is electrically connected to the
The valve opening timing and valve opening time of the fuel injection valve 6 are controlled by a signal from the CU 5.

An auxiliary air passage 17 that bypasses the throttle valve 3 is connected to the intake pipe 2.
7, an auxiliary air control valve 18 for controlling the amount of auxiliary air.
Is provided. The auxiliary air control valve 18 is connected to the ECU 5, and the ECU 5 controls the valve opening amount.

On the other hand, immediately downstream of the throttle valve 3, a pipe 7 is provided.
An absolute pressure signal (PBA) sensor 8 is provided through the intake pipe, and an absolute pressure signal converted into an electric signal by the absolute pressure sensor 8 is supplied to the ECU 5. Further, an intake air temperature (TA) sensor 9 is attached downstream thereof.
Detects intake air temperature TA and outputs the corresponding electrical signal for EC
Supply to U5.

An engine water temperature (TW) sensor 10 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects an engine water temperature (cooling water temperature) TW, outputs a corresponding temperature signal, and supplies it to the ECU 5.

A signal pulse (hereinafter referred to as a "CYL signal pulse") is provided around a camshaft or a crankshaft (not shown) of the engine 1 at a predetermined crank angle position of a specific cylinder of the engine 1.
A cylinder discriminating sensor (hereinafter referred to as “CYL sensor”) 13 at a crank angle position a predetermined crank angle before the top dead center (TDC) at the start of the intake stroke of each cylinder (180 ° crank angle in a four-cylinder engine). T)
A TDC sensor 12 for generating a DC signal pulse, and one pulse (hereinafter referred to as a “CRK signal pulse”) at a constant crank angle (for example, 30 °) cycle shorter than the cycle of the TDC signal pulse
A crank angle sensor (hereinafter referred to as “CRK sensor”) 11 for generating a CYL signal pulse, a TDC signal pulse, and a CRK signal (crank angle signal) pulse are supplied to the ECU 5. These signal pulses are used for various timing controls such as fuel injection timing, ignition timing, and the like, and detection of an engine speed NE and a rotation fluctuation amount described later.

The three-way catalyst 15 is disposed in the exhaust pipe 14 of the engine 1 and purifies components such as HC, CO, and NOx in the exhaust gas. An oxygen concentration sensor 16 (hereinafter, referred to as an “O2 sensor 16”) as an air-fuel ratio sensor is mounted upstream of the three-way catalyst 15 in the exhaust pipe 14.
The 2 sensor 16 detects the oxygen concentration in the exhaust gas, outputs an electric signal corresponding to the detected value, and supplies the electric signal to the ECU 5.

Various sensors such as a vehicle speed sensor 20 for detecting a traveling speed V of a vehicle equipped with the engine 1 and a gear ratio sensor 21 for detecting a gear ratio (shift position) of a transmission of the vehicle are connected to the ECU 5. The detection signals of these sensors are supplied to the ECU 5. Further, the gear ratio may be obtained from the vehicle speed V and the engine speed NE.

The ECU 5 shapes input signal waveforms from various sensors, corrects a voltage level to a predetermined level, and converts an analog signal value into a digital signal value. The CPU 5b includes a storage unit 5c for storing various calculation programs executed by the CPU 5b, calculation results, and the like, an output circuit 5d for supplying a drive signal to the fuel injection valve 6, and the like.

The CPU 5b determines various engine operation states such as a feedback control operation area and an open loop control operation area corresponding to the oxygen concentration in the exhaust gas based on the various engine parameter signals described above, and sets the engine operation state. Accordingly, based on the following equation (1), the TDC
Fuel injection time TO of the fuel injection valve 6 synchronized with the signal pulse
Calculate UT.

TOUT = TI × KLSAF × KO2 × K1 + K2 (1) Here, TI is a basic fuel amount, specifically, a basic fuel injection time determined according to the engine speed NE and the intake pipe absolute pressure PBA. And a TI for determining this TI value
The map is stored in the storage unit 5c. The TI map is set such that the air-fuel ratio of the air-fuel mixture supplied to the engine substantially becomes the stoichiometric air-fuel ratio in the operating state corresponding to the engine speed NE and the intake pipe absolute pressure PBA.

KLSAF is a lean burn correction coefficient set to a value smaller than 1.0 in a predetermined operating state of the engine 1 and the vehicle.

In this embodiment, the stoichiometric control region, the first lean control region, and the second lean control region as shown in FIG. 2 are determined according to the engine speed NE and the throttle valve opening θTH, and the engine speed is determined. In the engine operating state in which the NE and the throttle valve opening θTH are in the stoichiometric control range, feedback control is performed with the target air-fuel ratio being substantially the stoichiometric air-fuel ratio, and a limit is applied in a high-load operating state where the throttle valve is fully opened. In the operating state given,
Open loop control is performed. In the stoichiometric control region, the lean burn correction coefficient KLSAF is set to “1.0”.

In an engine operating state in which the engine speed NE and the throttle valve opening θTH are in the first lean control region, the target air-fuel ratio is set, for example, to an air-fuel ratio of about 18 to 22, and the target air-fuel ratio is set in the second lean control region. In a certain engine operating state, for example, the air-fuel ratio is set to about 30 to 50. In these lean control regions, a lean burn correction coefficient K is determined in accordance with a target equivalence ratio KOBJ obtained by converting the target air-fuel ratio into an equivalence ratio, as will be described later, and a rotation fluctuation amount of the engine 1.
LSAF is calculated. This lean burn correction coefficient KL
The calculation method of the SAF will be described with reference to FIGS.

KO2 is an air-fuel ratio correction coefficient calculated based on the output of the O2 sensor 16. During the air-fuel ratio feedback control in the stoichiometric control region, KO2 is
The air-fuel ratio (oxygen concentration) detected is set to match the stoichiometric air-fuel ratio, and is set to a predetermined value or a learning value according to the engine operating state during open-loop control and lean control.

K1 and K2 are other correction coefficients and correction variables calculated in accordance with various engine parameter signals, respectively, to optimize various characteristics such as fuel consumption characteristics and engine acceleration characteristics according to the engine operating state. Is set to such a value.

The CPU 5b further includes an auxiliary air amount control valve 1
An auxiliary air control amount ILEAN substantially proportional to the valve opening amount of No. 8 is calculated. More specifically, in the stoichiometric control region and the first lean control region, FIG.
A maximum control amount ILEANH and a minimum control amount ILEANL are calculated by searching an ILEAN table shown in FIG.
Interpolation calculation is performed according to the throttle valve opening θTH to determine the auxiliary air control amount ILEAN. In this case, the auxiliary air control amount ILEAN is set such that the larger the throttle valve opening θTH, the larger the auxiliary air amount.

In the second lean control region, an ILEAN table shown in FIG. 3B is searched according to the engine speed NE to obtain a maximum control amount ILEANH and a minimum control amount IL.
EANL is calculated, and an interpolation operation is performed according to the lean burn correction coefficient KLSAF to determine the auxiliary air control amount ILEAN. In this case, the auxiliary air control amount ILEAN is set such that the larger the lean burn correction coefficient KLSAF, the larger the auxiliary air amount.

The CPU 5b further determines the valve opening timing (fuel injection timing) of the fuel injection valve 6 according to the engine operating state. Specifically, the stoichiometric control region of FIG. 2 and the first
In the lean control region, fuel is injected during the intake stroke of each cylinder,
In the lean control region, it is determined that the fuel is injected in the compression stroke of each cylinder.

The CPU 5b supplies a drive signal for opening the fuel injection valve 6 to the fuel injection valve 6 via the output circuit 5d based on the fuel injection time TOUT and the fuel injection timing obtained as described above, Air control amount ILEA
A drive signal corresponding to N is supplied to the auxiliary air amount control valve 18.

FIG. 4 shows the lean burn correction coefficient KLSAF.
5 is a flowchart of a process of calculating a rotation fluctuation amount DMSSLB used for calculation of, and this process is executed by the CPU 5b.

FIG. 4A shows a CRK process executed every time the CRK signal pulse is generated. In step S1, a CRK signal pulse generation time interval (proportional to the reciprocal of the engine speed) is shown. Parameter). Specifically, as shown in FIG. 5, every time the crankshaft rotates 30 degrees, CRME (n) and CRME (n +
1), CRME (n + 2)... Are measured.

Note that the period during which the crankshaft rotates 180 degrees is divided into every 30 degrees, and each of the periods is # 0STG to # 5STG.
(# 0 stage to # 5 stage).

In step S2, 11 is obtained by the following equation (2).
The latest measured value C from the previous measured value CRME (n-11)
A first average value CR12ME (n) is calculated as an average value of the twelve CRMe values up to RME (n).

[0035]

(Equation 1) In this embodiment, since the CRK signal pulse is generated every time the crankshaft rotates 30 degrees, the first average value CR12ME
(N) is an average value corresponding to one rotation of the crankshaft. By performing such an averaging process, a primary vibration component of the engine rotation for one cycle of one rotation of the crankshaft, that is, a mechanical error (a manufacturing error, a mounting error, etc.) of the pulsar or the pickup constituting the crank angle sensor 11 ) Can be removed.

The engine speed NE is calculated based on the CR12ME (n) value.

FIG. 3B shows a process executed in # 3STG (# 3 stage, see FIG. 3) having the same period as the TDC signal pulse generation period. First, step S11
Then, according to the following equation (3), the average value of the six CR12ME values from the calculated value CR12ME (n−5) five times before the first average value CR12ME to the latest calculated value CR12ME (n) is calculated as An average value MSME (n) of 2 is calculated.

[0038]

(Equation 2) In this embodiment, the engine 1 is a four-cylinder four-cycle engine, and ignition is performed in one of the cylinders every time the crankshaft rotates 180 degrees. Therefore, the second average value MSME
(N) is an average value of the first average value CR12ME (n) for each ignition cycle. By performing such averaging processing, it is possible to remove a secondary vibration component represented as a torque fluctuation of the engine rotation due to combustion, that is, a vibration component of a crankshaft half rotation cycle.

Next, according to the following equation (4), the rotational fluctuation DM
Calculate SSLB (n).

DMSSLB (n) = | (MSME (n) −MSME (n−1) / KMSSLB | (4) Here, in KMSSLB, the control accuracy at the time of the lean burn control does not change according to the engine speed. Is set so as to be in inverse proportion to the engine speed, and the rotation fluctuation amount DMSSLB is set to the engine speed NE.
Is not changed in accordance with the condition.

The rotation fluctuation amount DM thus calculated
SSLB tends to increase as the combustion state of the engine 1 deteriorates, and can be used as a parameter indicating the combustion state of the engine. Generally, as the air-fuel ratio becomes leaner, the combustion state becomes gradually unstable, and the rotation fluctuation amount DMSSLB increases. Then, as shown in FIG. 15 (b), a state in which irregular combustion in which the rotation fluctuation amount DMSSLB increases in a spike manner about once every several seconds appears, is a state in which the air-fuel ratio is controlled to substantially the lean limit. When the vehicle further leans, the combustion becomes unstable, in which surging is transmitted to the driver. Therefore, it is desirable to control the air-fuel ratio to the state shown in FIG.

FIG. 6 is a flow chart of a lean burn control process for executing such air-fuel ratio control. This process is executed every time a TDC signal pulse is generated.
b.

In step S21, a target equivalence ratio KOBJ obtained by converting the target air-fuel ratio into an equivalence ratio is calculated by the processing of FIG. 7, and then based on the target equivalence ratio KOBJ and the rotation fluctuation amount DMSSLB of the engine 1 by the processing of FIG. A KLSAF calculation process for calculating the lean burn correction coefficient KLSAF is executed (step S22).

In step S101 of FIG. 7, it is determined whether or not the engine operating state is in the second lean control area. If the answer is negative (NO), that is, if the engine is in the first lean control area or the stoichiometric control area, Then, the target equivalent ratio KOBJ is calculated according to the operating state of the engine 1 and the vehicle (step S104). Specifically, the target equivalent ratio KOB
J is engine water temperature TW, gear ratio, vehicle speed V, throttle valve opening θTH, engine speed NE, and absolute pressure P in the intake pipe.
It is calculated according to BA or the like.

When the engine operating state is in the second lean control region, the KOBJDI table shown in FIG. 8 is searched according to the engine speed NE to obtain the maximum target equivalent ratio KO.
BJDIH and the minimum target equivalent ratio KOBJDIL are calculated, and an interpolation calculation is performed according to the throttle valve opening θTH.
The target equivalent ratio KOBJDI for the second lean control region is calculated (step S102). In this case, the target equivalent ratio KO
BJDI is set to increase as the throttle valve opening θTH increases. Then, the calculated target equivalent ratio KOBJDI for the second lean control region is set to the target equivalent ratio KOBJ.
(Step S103), and the present process ends.

Next, the KLSAF calculation processing of FIG. 9 will be described. In step S31 of the figure, the current target equivalent ratio KO
BJ (N) and previous lean burn correction coefficient KLSAF
In order to calculate the deviation from (N-1) and to determine whether the current correction of the air-fuel ratio is the rich direction or the lean direction, the change amount DKLSAF is calculated by the following equation (5) using the current value KOBJ of the target air-fuel ratio. (N) and the previous value KL of the lean burn correction coefficient
It is calculated as the difference from SAF (N-1). In addition,
(N) and (N-1) are added to indicate the current value and the previous value, respectively, but (N) indicating the current value is usually omitted.

DKLSAF = KOBJ (N) −KLSAF (N−1) (5) In the following step S34, it is determined whether or not the change amount DKLSAF calculated in step S31 is a positive value. When the answer is affirmative (YES), that is, when the air-fuel ratio is to be corrected in the rich direction, it is determined whether or not the engine speed NE is higher than the first predetermined speed NKSLB1 (step S37), and NE ≦ If NKSLB1, the addition term DKC1 is set to the predetermined value for low rotation DKC1M1H (step S41), and the process proceeds to step S42.

If NE> NKSLB1 in step S37, it is further determined whether or not the speed is higher than a second predetermined speed NKSLB2 higher than the first predetermined speed NKSLB1 (step S38). When NE ≦ NKSLB2, the addition term DKC1 is set to the predetermined value DKC1M for medium rotation.
1M, and if NE> NKSLB2, set them to the high rotation predetermined value DKC1M1L (steps S40, S39), and proceed to step S42. In addition, each predetermined value is DKC1M1H>DKC1M1M> DKC1M
It has a relationship of 1L.

In the step S42, the step S31
The absolute value of the change amount DKLSAF calculated in the step is calculated as the addition term DKC
It is determined whether it is greater than 1 and | DKLSAF | ≦ DK
If C1, the current value of the lean burn correction coefficient KLS
AF (N) is set to the current target equivalent ratio KOBJ (N) (step S43), and the process proceeds to step S45. Also |
When DKLSAF |> DKC1, the present value KLSAF (N) of the lean burn correction coefficient is obtained by the following equation (6).
Is set (step S44), and the process proceeds to step S45.

KLSAF (N) = KLSAF (N−1) + DKC1 (6) In step S45, “1” indicates that the KLSAF value is set according to the rotation fluctuation amount DMSSLB (feedback control of the KLSAF value). The lean feedback flag FSLFBB is set to "0", and then KL
It is determined whether the SAF (N) value is greater than 1.0 (step S46). Then, KSAF (N) ≦ 1.
0, immediately, and KLSAF (N)> 1.0
If KLSAF (N) = 1.0 (step S47), the process proceeds to step S48.

In step S48, it is determined whether or not the KLSAF (N) value is smaller than a predetermined lower limit value KLSAFFL.
As soon as KLSAF (N) ≧ KLSAFL,
If KLSAF (N) <KLSAFL, K
This process ends with LSAF (N) = KLSAFL.

As described above, when FWOT = 1 and WO
When in the T region or when DKLSAF> 0 and KLS
When the AF value increases, setting of the KLSAF value according to the rotation fluctuation amount DMSSLB (lean feedback control)
Do not do.

In step S34, the change amount DKLSAF ≦
0, that is, when the target equivalent ratio KOBJ (N) becomes smaller than the previous value LSSAF (N-1) of the lean burn correction coefficient, and when the current air-fuel ratio should be corrected in the lean direction, or KOBJ (N) = KLSAF ( If N-1), the threshold setting process (the process of setting a predetermined threshold) shown in FIG. 10 and the KLSAF feedback process shown in FIGS. 13 and 14 are executed, and the process proceeds to step S48.

In step S111 in FIG. 10, it is determined whether or not the engine 1 is in an idle state (idling determining means). In the idle state, the throttle valve 3 is almost fully closed, or the intake pipe absolute pressure PBA indicates a value corresponding to the throttle valve fully closed state (a predetermined low load state), and the engine speed NE is a predetermined level. The idling rotation speed NIDLE (for example, about 1000 rpm,
(It may be changed according to the warm-up state of the engine 1). When the answer is negative (NO), that is, when the engine 1 is in a state other than the idle state (hereinafter referred to as “off-idle state”), the second lower threshold value is set according to the engine speed NE and the intake pipe absolute pressure PBA. MSLE
AN1 and the second upper threshold value MSLEAN2 (FIG. 15)
(See (b)) is determined (step S112). Specifically, first, the table of FIG. 11A in which a threshold is set according to the engine speed NE is searched according to the engine speed NE (the horizontal axis of FIG. 11A indicates the engine speed NE). The lower the rotation speed, the lower the rotation speed, and the set value indicates the maximum, and the part where the set value is constant is the threshold value at the rotation speed corresponding to the idling determination rotation speed NIDLE), and the upper limit value of the threshold values MSLEAN1 and MSLEAN2. MSLEA
N1H, MSLEAN2H and lower limit value MSLEAN1
L, MSLEAN2L is determined. Next, FIG.
As shown in the figure, the absolute pressure PBA in the intake pipe is equal to the upper limit value PBMS.
If it is not less than H, the threshold values MSLEAN1, MSLEA
As N2, upper limit values MSLEAN1H, MSLEAN2
H, the absolute pressure PBA in the intake pipe is lower than PBMSL
If not more than the lower limit value MSLEAN1L, MSLE
When AN2L is adopted and PBMSL <PBA <PBMSH, MSLEAN1 value and MS
Determine the LEAN2 value.

As will be described later, the first upper threshold value and the first lower threshold value are obtained by adding threshold coefficients α (> 1.0) and β (<1.0) to the average value DMSBAVE of the rotation fluctuation amount DMSSLB.
1.0) is multiplied by (α × DMS
BAVE) (β × DMSBAVE) (FIG. 15).
(B)).

In the following step S113, as shown in Table 1, the correction coefficient KMSGRiM (i = m) depends on whether the vehicle is an MT (manual transmission) vehicle or an AT (automatic transmission) vehicle and the gear ratio.
3,4,5) or KMSGRjA (j = 2,3,4)
Is determined as the correction coefficient KMSGR. Next, by multiplying the value calculated in step S112 by the correction coefficient KMSGR, final second lower threshold value MSLEAN1 and second upper threshold value MSLEAN2 are calculated (step S114).

[0057]

[Table 1] In addition, each correction coefficient value is KMSGR3M <KMSGR4
M <KMSGR5M, KMSGR2A <KMSGR3A
<KMSGR4A is set. Also,
"CVT" in Table 1 means a continuously variable transmission.
When the gear ratio is equivalent to the 3rd, 4th, and 4th speed, respectively, KMSG
R2A, KMSGR3A, KMSGR4A are used.

In the following step S115, a first upper threshold (α × DMSBAVE) and a first lower threshold (β × D
MSBAVE) are set to off-idle coefficient values α1 and β1, respectively, and the process proceeds to step S118.

On the other hand, when the engine 1 is in the idle state, the process proceeds from step S111 to S116, where the second lower threshold value MSLEAN1 and the second upper threshold value MSLEAN2 are set.
With the idle threshold values MSLEAN1IDL, M
Set to SLEAN2IDL. Here, the threshold values for idle MSLEAN1IDL and MSLEAN2IDL are:
Lower limit values MSLEAN1L and MSL shown in FIG.
Idle determination rotation speed NIDL indicating the maximum of EAN2L
The values MS1LMAX and MS at a rotational speed corresponding to E
Set to a value smaller than 2LMAX (MSLEAN
1IDL <MS1LMAX, MSLEAN2IDL <M
S2LMAX).

In the following step S117, threshold coefficients α and β are set to idle coefficient values α2 and β2, respectively.
Proceed to step S118. Here, the idle coefficient value α
2 and β2 are off-idle coefficient values α1 and β1 respectively.
Set to a smaller value. That is, α2 <α1,
β2 <β1.

In step S118, it is determined whether or not the enrichment request flag FMFLBRICH, which indicates that air-fuel ratio enrichment is required by misfire detection, is "1". As a result, when FMFLBRICH = 0, immediately, and when FMFLBRICH = 1, the threshold coefficient α is set to the misfire detection coefficient value α3 (<α2)) (step S119), and the process ends. .

According to the threshold setting process described above, each threshold M
SLEAN1, MSLEAN2, (β × DMSBAV
E) and (α × DMSBAVE) are set to values smaller in the idle state of the engine 1 than in the off-idle state where the engine speed NE is low. This is because, as shown in FIG. 12, the increasing tendency of the rotation fluctuation amount DMSSLB with respect to the change of the air-fuel ratio in the lean direction is indicated by the curve A in the off-idle state, and as indicated by the curve B in the idling state. This is because the fact that the rate of increase of the rotation fluctuation amount DMSSLB with respect to the leaning of the air-fuel ratio is large is taken into consideration. By setting the threshold value according to this process, in the KLSAF feedback process described below, the lean burn correction coefficient K
The setting of the LSAF moves in the rich direction, the amount of rotation fluctuation when executing the lean burn control in the idle state is maintained at an appropriate level, and the fuel efficiency can be improved while ensuring the stability of the engine rotation.

Next, the KLSAF feedback processing will be described with reference to FIG.

In step S51 of the figure, it is determined whether or not the lean feedback flag FSLFBB is "1".
When FSLBFB = 1, the following equation gives (7):
An average value DMSBAVE of the fluctuation amount DMSSLB is calculated (step S52).

DMSBAVE = DMSCRF × DMSSLB (N) / A + (A−DMSCRF) × DMSBAVE (N−1) / A (7) where A is a predetermined value set to, for example, 10000 HEX, and DMSCRF is 1 to DMSBAVE (N-1), a smoothing coefficient set to a value between A, is a previously calculated value.

In the following step S53, the change amount DTH (= θTH (N) -θTH (N
-1)) is larger than a predetermined change amount DTHSLB, and if DTH> DTHSLB and the opening amount of the throttle valve (the amount of depression of the accelerator pedal) is large, the rich correction term DAFR is opened. The predetermined value for valve operation DAFTH is set (step S54), and the process proceeds to step S92 in FIG.

In step S92, the current value KL of the lean burn correction coefficient is obtained by adding the rich correction term DAFR to the previous value KLSAF (N-1) according to the following equation (8).
Set SAF (N).

KLSAF (N) = KLSAF (N−1) + DAFR (8) Next, the calculated KLSAF (N) value is equal to the predetermined upper limit value KL.
It is determined whether it is larger than SAFFBH (step S9).
3) If KLSAF (N) ≦ KLSAFFBH, immediately if KLSAF (N)> KLSAFFBH, set KLSAF (N) = KLSAFFBH (step S94), and end this processing.

Returning to FIG. 13, in step S53, DTH ≦
When it is DTHSLB, the change amount DPB of the absolute pressure PBA in the intake pipe (= PBA (N) -PBA (N-1)) is expressed by:
It is determined whether or not it is larger than the predetermined change amount DPBSLB (step S55).
The rich correction term DAFR is set to a predetermined value DAFRP for increasing the load.
B (step S56), and step S92
Proceed to (FIG. 14).

When the answer to step S55 is negative (NO), that is, when DPB≤DPBSLB, the process proceeds to step S74 in FIG.

In step S74, the rotation fluctuation amount DMSS
It is determined whether or not LB is smaller than a second lower threshold value MSLEAN1 (see FIG. 15B), and DMSSLB <MSL
If EAN1, the first lower threshold (β × D
MSBAVE) is determined (step S75).

In step S75, DMSSLB <(β ×
DMSBAVE), the lean correction term DAFL
Is set to the first predetermined value DAFL1 (step S7).
6) If DMSSLB ≧ (β × DMSBAVE), a second predetermined value DAFL2 smaller than the first predetermined value DAFL1 is set (step S77), and the process proceeds to step S82.

In step S82, step S3 in FIG.
It is determined whether or not the absolute value of the change amount DKLSAF calculated in step 1 is smaller than the lean correction term DAFL, and | DKLS
If AF│ ≧ DAFL, the lean correction term DAFL is subtracted from the previous value KLSAF (N−1) by the following equation (9) to set the current value KLSAF (N) (step S83), and this processing is performed. To end.

KLSAF (N) = KLSAF (N−1) −DAFL (9) Thus, | DKLSAF | ≧ DAFL, and the current target equivalent ratio K with respect to the previous value KLSAF (N−1)
When the decrease amount of OBJ (N) is equal to or greater than the lean correction term DAFL, the present value KLSAF (N) value is set so that the decrease amount of the lean burn correction coefficient KLSAF becomes the DAFL value set according to the rotation fluctuation amount DMSSLB. Is set to prevent the air-fuel ratio from becoming excessively lean.

If | DKLSAF | <DAFL, the routine proceeds to step S84, where the present value KLSAF (N) of the lean burn correction coefficient is set to the target equivalent ratio KOBJ.
(N), then KLSAF (N-1) <1.0
It is determined whether the lean flag FSLB indicating “1” is “1” (step S85). As a result, as soon as FSLB = 0, FSLB =
When it is 1, the lean feedback flag FSLBF
B is set to "1" (step S86), and this processing ends.

If the answer to step S74 is negative (NO),
That is, when DMSSLB ≧ MSLEAN1, the rotation fluctuation amount DMSSLB is set to the second upper threshold value MSLEAN2.
It is determined whether or not the value is smaller than (see FIG. 15B) (step S78). If DMSSLB <MSLEAN2, the DMSSLB value is further set to the first upper threshold (α × D).
MSBAVE) (step S)
79), when DMSSLB <(α × DMSBAVE), the DMSSLB value is further reduced to the first lower threshold (β × DMSBAVE).
DMSBAVE) is determined.

Then, the answer to step S80 is affirmative (YE
S), that is, when DMSSLB <(β × DMSBAVE), the lean correction term DAFL is set to the third predetermined value DAF.
L3 (<DAFL1), and the process goes to step S82.
Proceed to.

If the answer to step S80 is negative (NO),
That is, when DMSSLB ≧ (β × DMSBAVE), the lean burn correction coefficient KLSAF is held as the previous value (step S87), and the process ends.

If the answer to step S78 is negative (NO),
That is, when DMSSLB ≧ MSLEAN2, the DMSSLB value further becomes the first upper threshold (α × DMSBAV).
E) It is determined whether or not it is smaller (step S88).
As a result, when DMSSLB ≧ (α × DMSBAVE), the rich correction term DAFR is changed to the first predetermined value DAF.
R1 (step S91) and DMSSLB
If <(α × DMSBAVE), the second predetermined value DAFR2 is set to be smaller than the first predetermined value DAFR1 (step S90), and the process proceeds to step S92.

If the answer to step S79 is negative (N
O), that is, when DMSSLB ≧ (α × DMSBAVE), the rich correction term DAFR is set to the third predetermined value DAF.
R3 (<DAFR1) (step S89)
Proceed to step S92.

As described above, when the rotation fluctuation amount DMSSLB is large, the rich correction term DAFR is set to a larger value as the DMSSLB value is larger, thereby preventing the combustion state from further deteriorating.

Returning to FIG. 13, when the answer to step S51 is negative (NO), that is, when FSLBFB = 0, it is determined whether or not the previous value KLSAF (N-1) is larger than a predetermined value KLSAFX1 (step S57). ), KLSAF (N
-1) When KLSAFX1, the lean correction term D
AFL is set to the fourth predetermined value DAFLX1 (step S58), and the process proceeds to step S82.

In step S57, KLSAF (N-
1) When ≧ KLSAFX1, a high load flag FSLBP indicating “1” indicating a predetermined high load operation state
It is determined whether or not ZN is "1" (step S59).
When LBPZN = 0, the previous value KLSAF
(N-1) is a predetermined value KLSAFX2 (<KLSAFX
1) It is determined whether or not the value is larger than the value (step S62).
Then, when FSLBPZN = 1 or KLSAF (N
-1) If KLSAFX2, step S60
To the average value DMSBAV of the rotation fluctuation amount DMSSLB
E is initialized, and the lean feedback flag FSLFBFB is set to "1" (step S6).
1), and proceed to the step S74. Here, the average value DM
The initialization of SBAVE is as follows: DMSBAVE = DMSSLB
(N).

If the answer in step S62 is affirmative (YE
S), that is, when KLSAF (N−1)> KLSAFX2, the rotation fluctuation amount DMSSLB is equal to the second upper threshold M
It is determined whether or not it is larger than SLEAN2 (step S6).
3) If DMSSLB ≦ MSLEAN2, the lean correction term DAFL is set to a fifth predetermined value DAFLX2 (step S67), and the routine proceeds to step S82.

In step S63, DMSSLB> M
If the combustion state has deteriorated due to SLEAN2, the average value DMSBAVE is initialized and the lean feedback flag FSL is executed in the same manner as in steps S60 and S61.
BFB is set to "1" (steps S64 and S65),
Further, a fourth predetermined value DAFRX is added to the rich correction term DAFR.
Is set (step S66), and the process proceeds to step S92.

By the processing shown in FIGS. 13 and 14, the rotational fluctuation amount DMSSLB and the correction terms DAFR and DAFL of the lean burn correction coefficient KLSAF selected according to the value.
The set values DAFR1 to 3 and DAFL1 to 3 are summarized as follows. That is, when the DMSSLB value is equal to or larger than the upper threshold value MSLEAN2 or α × DMSBAVE, the rich correction term DA increases as the DMSSLB value increases.
When FR is set to a large value and becomes smaller than the lower threshold value MSLEAN1 or β × DMSBAVE, DMSSLB is set.
As the value decreases, the lean correction term DAFL is set to a larger value, and when the DMSSLB value is between the upper threshold value and the lower threshold value, the lean burn correction coefficient KLSAF is held at the previous value.

1) DMSSLB ≧ MSLEAN2 and D
When MSSLB ≧ α × DMSBAVE, DAFR
= DAFR1 2) α × DMSBAVE> DMSSLB ≧ MSLEAN
2) DAFR = DAFR2 (<DFR1) 3) MSLEAN2> DMSSLB ≧ α × DMSBAV
When E, DAFR = DAFR3 (<DFR1) 4) DMSSLB <MSLEAN2 and DMSSLB <
α × DMSBAVE and DMSSLB ≧ MSLEAN1
And when DMSSLB ≧ β × DMSBAVE, K
LSAF (N) = KLSAF (N-1) (previous value retained) 5) β × DMSBAVE> DMSSLB ≧ MSLEAN
When it is 1, DAFL = DAFL3 (<DFL1) 6) MSLEAN1> DMSSLB ≧ β × DMSBAV
When E, DAFL = DAFL2 (<DFL1) 7) DMSSLB <MSLEAN1 and DMSSLB <
When β × DMSBAVE, DAFL = DAFL1 As described above, according to the present embodiment, as shown in FIG. 15, the rich correction of the lean burn correction coefficient KLSAF is performed in accordance with the degree of increase or decrease of the rotation fluctuation amount DMSSLB. Since the term DAFR or the lean correction term DAFL is determined, good fuel economy characteristics can be obtained within a range that does not deteriorate the operability of the engine. In addition, in the present embodiment, the rotation fluctuation amount DMSSLB is calculated based on the first threshold value (α × DMSBAVE) calculated according to the average value DMSBAVE,
(Β × DMSBAVE), and the lean burn correction coefficient KLSAF is set according to the comparison result. Therefore, regardless of the mass production variation and the degree of deterioration of the engine components, good lean feedback control, that is, Lean feedback control that achieves the best fuel efficiency within a range where the performance is not deteriorated becomes possible. Further, a second threshold M
Since the correction terms DAFR and DAFL of the lean burn correction coefficient KLSAF are also determined using SLEAN1 and MSLEAN2, finer control can be performed.

Further, each threshold value (α × DMSBAVE),
(Β × DMSBAVE), MSLEAN1, MSLEA
N2 is set to a smaller value when the engine 1 is in the idle state than in the off-idle state (FIG. 10), so that when the engine 1 is in the idle operation state, it is smaller than when it is in another operation state. As a result, the rotation fluctuation amount DMSSLB easily exceeds the upper threshold value (α × DMSBAVE) and MSLEAN2, and the lower threshold value (β × DMSBAV)
E), it is difficult to fall below MSLEAN1, and it is difficult to update the lean burn correction coefficient KLSAF in the decreasing direction. As a result, the air-fuel ratio is made lean within a range in which rotation stability can be ensured in an idle operation state of the engine, so that fuel efficiency can be improved.

In the present embodiment, the processing of FIG. 4 executed by the crank angle sensor 11 and the CPU 5b corresponds to the rotation fluctuation detecting means, and the threshold setting processing (FIG. 10) and the KLSAF feedback processing (FIG. 10) executed by the CPU 5b. 13, 14) correspond to the correction means. Also, the thresholds (α × DMSBAVE) and (β × DMSBAVE)
The threshold value MSLEAN corresponds to the “predetermined threshold value” in claim 1.
1, MSLEAN2 corresponds to the “predetermined threshold value” in claim 2.

Note that the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above-described embodiment, the threshold value (α ×
DMSBAVE), (β × DMSBAVE), MSLE
For all of AN1 and MSLEAN2, the value in the idle state is set to be smaller than the value in the off-idle state. You may.

Further, the average value D of the rotation fluctuation amount DMSSLB is obtained.
Smoothing factor DMSCRF used to calculate MSBAVE
(Equation (7)) is set to a larger value in the idle state than in the off-idle state, and the current value DMSSLB (N)
The degree of contribution (decrease the smoothing time constant)
You may do so.

[0092]

As described in detail above, according to the first aspect of the present invention, when the engine is in the idle state, when the predetermined threshold value to be compared with the detected rotation fluctuation is other than the idle state. Is set to a value smaller than the value of, the amount of rotation fluctuation is more likely to exceed the upper threshold value in the idling operation state than in the other operation state, or less likely to fall below the lower threshold value, and the fuel supply The amount is easily corrected in the increasing direction or hardly corrected in the decreasing direction.
As a result, the air-fuel ratio is made lean within a range where rotation stability can be ensured in the idling state of the engine, and the fuel efficiency can be improved.

According to the second aspect of the present invention, the predetermined threshold value to be compared with the detected rotation fluctuation amount is set according to the engine speed, and when the engine is in the idle state,
Since the predetermined threshold value is set to a value smaller than the value of the idling determination speed when the engine is not in the idling state, the same effect as that of the first aspect is obtained. That is, when in the idling operation state, the rotation fluctuation amount is more likely to exceed the upper threshold value than in the other operation state, or hardly falls below the lower threshold value, and the fuel supply amount is easily corrected in the increasing direction, Alternatively, since it is difficult to correct in the decreasing direction, the air-fuel ratio is made lean within a range in which the rotation stability can be ensured in the idling operation state of the engine, and the fuel efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an internal combustion engine and a fuel supply control device thereof according to an embodiment of the present invention.

FIG. 2 is a diagram showing an air-fuel ratio control region determined according to an engine speed and a throttle valve opening;

FIG. 3 is a diagram illustrating a control amount (ILEA) for controlling an auxiliary air amount;
FIG. 9 is a diagram showing a table for determining N).

FIG. 4 is a flowchart of a process for detecting a rotation fluctuation amount (DMSSLB) of the engine.

FIG. 5 is a diagram for explaining a relationship between measurement of a parameter representing a rotation speed of an engine and a rotation angle of a crankshaft.

FIG. 6 is a flowchart of a lean burn control process.

FIG. 7 is a flowchart of a process for calculating a target equivalent ratio (KOBJ).

FIG. 8 is a diagram showing a table used in the processing of FIG. 7;

FIG. 9 is a flowchart of a lean burn correction coefficient (KLSAF) calculation process.

FIG. 10 is a flowchart of a threshold setting process of FIG. 9;

FIG. 11 is a diagram showing a table used in the processing of FIG. 10;

FIG. 12 is a diagram showing a relationship between an air-fuel ratio and an engine rotation fluctuation amount.

FIG. 13 is a flowchart of a feedback process of a lean burn correction coefficient (KLSAF).

FIG. 14 is a flowchart of a feedback process of a lean burn correction coefficient (KLSAF).

FIG. 15 is a diagram illustrating a relationship between a rotation fluctuation amount (DMSSLB) and a lean burn correction coefficient (KLSAF).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 4 Throttle valve opening sensor 5 Electronic control unit (rotation fluctuation detection means, correction means, idling determination means) 6 Fuel injection valve (fuel injection means) 11 Crank angle sensor (rotation fluctuation amount detection means)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Hideyuki Oki 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Inventor Hironao Fukuchi 1-4-1 Chuo, Wako-shi, Saitama No. Within Honda R & D Co., Ltd. (72) Inventor Takashi Kiyomiya 1-4-1 Chuo, Wako-shi, Saitama

Claims (2)

[Claims] 1. A rotation fluctuation detecting means for detecting a rotation fluctuation amount of an internal combustion engine, comparing the detected rotation fluctuation amount with a predetermined threshold value, and correcting a fuel amount supplied to the engine according to the comparison result. In a fuel supply control device for an internal combustion engine, comprising: a correction unit, and a fuel injection unit that directly injects the fuel amount corrected by the correction unit into a combustion chamber of the engine, wherein the correction unit is in an idle state. In some cases, the predetermined threshold value is set to a value smaller than a value in a state other than the idle state. 2. A rotation fluctuation detecting means for detecting a rotation fluctuation amount of an internal combustion engine, comparing the detected rotation fluctuation amount with a predetermined threshold value, and correcting a fuel amount supplied to the engine according to the comparison result. A fuel supply control device for an internal combustion engine, comprising: a correction unit, and a fuel injection unit that directly injects the fuel amount corrected by the correction unit into a combustion chamber of the engine. An idle determining unit that determines an idle state of the engine when the engine is smaller and the engine is in a predetermined low load state, wherein the correcting unit sets the predetermined threshold value according to a rotation speed of the engine. If it is determined that the engine is in the idle state, the predetermined threshold value is set to a value smaller than the value of the idle determination rotation speed when the engine is not in the idle state. Fuel supply control apparatus for an internal combustion engine, characterized.