JP3089094B2 - Control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for an internal combustion engine, and more particularly to a control apparatus for controlling the control parameters of an engine (for example, fuel injection amount, Exhaust gas recirculation amount).

[0002]

2. Description of the Related Art Conventionally, a specific one of a multi-cylinder internal combustion engine has been known.
A combustion pressure sensor is provided for each cylinder, and the output of the combustion pressure sensor
Calculates the torque fluctuation of that cylinder from
The engine's air-fuel ratio to the lean side as much as possible
Known fuel injection amount control device for feedback control
(JP-A 1-271634). This conventional device
Fuel injection control reduces the amount of torque fluctuation between cycles
Since it is performed near the limit value, lean limit
Control, which improves fuel efficiency and reduces nitrogen oxides (NO _X)of
It is effective for reduction.

In the above-described conventional apparatus, the combustion pressure sensor is provided only in one of the multiple cylinders in order to prevent the cost of the apparatus and the complexity of the control from being increased. As a representative of the combustion pressure of all cylinders, variations in the misfire limit between cylinders (eg, exhaust gas recirculation (EG due to variations in valve clearance)
R), there is a possibility that a cylinder that reaches the misfire region is generated, and the overall torque fluctuation is controlled to be extremely poor.

Therefore, in the above-mentioned conventional apparatus, the magnitude of the torque generated between the cylinders is detected from the time required for the combustion stroke of each cylinder and the like, and the control for correcting the air-fuel ratio for each cylinder so that this is the same for each cylinder. (Inter-cylinder correction) is first performed, and after the inter-cylinder correction is completed, the above-described lean limit control is started.

However, in the above-described conventional apparatus, the calculation of the cylinder-to-cylinder correction coefficient requires that the operating state satisfy predetermined conditions, and that a certain amount of time is required to complete the cylinder-to-cylinder correction. I do. In other words, the calculation of the inter-cylinder correction coefficient is performed not only when each cylinder is in the combustion state, but also during the fuel cut in which each cylinder is not in the combustion state in order to eliminate a detection error, and the data is collected a predetermined number of times or more. However, depending on the operation pattern, the operation conditions during fuel cut are not easily set, and it may take a considerable time until the cylinder-to-cylinder correction is completed.

In such a case, the operating conditions (warm-up, rotation speed, load, etc.) of the internal combustion engine are corrected during the cylinder-to-cylinder operation despite the condition that the engine can be operated under fuel-efficient conditions by lean limit control. Since lean control of the air-fuel ratio cannot be performed, the fuel efficiency deteriorates during the inter-cylinder correction when the control is performed at the stoichiometric state.

Therefore, the present applicant has previously filed Japanese Patent Application No. 2-405.
No. 622 proposes a control device for an internal combustion engine that can control the air-fuel ratio to the lean side without causing the cylinder to fire even during the period in which the inter-cylinder correction is not completed. That is, the control device for the internal combustion engine proposed by the present applicant uses an inter-cylinder correction coefficient for equalizing the generated torque of each cylinder of the multi-cylinder internal combustion engine,
In a device that controls the air-fuel ratio of all cylinders so that the torque fluctuation value for each cycle of the cylinder provided with the combustion pressure sensor matches the target value, when the inter-cylinder correction is not completed, In this configuration, at least the guard value of the torque fluctuation amount correction coefficient on the side where the torque fluctuation amount is large is corrected to the side where the torque fluctuation amount is small.

[0008]

However, according to the control apparatus for an internal combustion engine proposed by the present applicant, the air-fuel ratio is made as lean as possible from the stoichiometric air-fuel ratio so that the torque fluctuation value becomes the target torque fluctuation amount. During the lean limit control in which feedback control is performed on the side, regardless of whether the torque fluctuation value of each specific cylinder in each cycle converges to the target torque fluctuation amount, the above-described inter-cylinder correction control is performed. The correction may be adversely affected.

That is, in a state where the torque fluctuation value is excessively smaller than the target torque fluctuation amount and the air-fuel ratio is richer than the limit lean air-fuel ratio, even if the fuel injection amount is increased or decreased based on the inter-cylinder correction. Since the change in the ratio of the substitute angular velocity change amount used for calculating the inter-cylinder correction coefficient is small, the inter-cylinder correction coefficient is continuously corrected to the upper and lower limits and is fixed at the upper and lower limits.

On the other hand, in a state where the torque fluctuation value is excessively large with respect to the target torque fluctuation amount and the air-fuel ratio is leaner than the target lean value, the combustion is extremely unstable, so that the rotation fluctuation is reduced. As a result, the ratio of the substitute angular velocity change amount for each calculation greatly changes, and the inter-cylinder correction control becomes unstable.

The present invention has been made in view of the above points,
An object of the present invention is to provide a control device for an internal combustion engine that solves the above-mentioned problem by performing inter-cylinder correction after the torque fluctuation value converges around the target torque fluctuation amount.

[0012]

FIG. 1 is a block diagram showing the principle of the present invention for achieving the above object. The present invention provides an inter-cylinder correction coefficient calculating means 1 for calculating an inter-cylinder correction coefficient for equalizing the generated torque of each cylinder of the multi-cylinder internal combustion engine 10 for each cylinder.
1. Torque fluctuation correction for calculating a torque fluctuation correction coefficient for a predetermined cylinder or all cylinders for matching a torque fluctuation value based on an integrated value of a torque fluctuation amount for each cycle of a generated torque of a predetermined cylinder to a target torque fluctuation amount. In a control device for an internal combustion engine, comprising a coefficient calculating means 12 and a correction control means 13 for correcting and controlling an engine control parameter of each cylinder by the inter-cylinder correction coefficient and the torque fluctuation amount correction coefficient, It is characterized by having a control means 15.

The detecting means 14 detects whether or not the torque fluctuation correction coefficient calculating means 12 is executing a process. In addition, when the calculation operation control means 15 detects that the processing is being executed by the detection means 14, the calculation operation control means 15 calculates the inter-cylinder correction coefficient calculation means only when the torque fluctuation value converges to a value near the target torque fluctuation amount. In step 11, the inter-cylinder correction coefficient is calculated.

[0014]

According to the present invention, a torque fluctuation correction coefficient calculating means 1 is provided.
During the execution of the process 2, the calculation operation of the inter-cylinder correction coefficient by the inter-cylinder correction coefficient calculating means 11 is executed only when the torque fluctuation value converges to a value near the target torque fluctuation amount, and the torque fluctuation value becomes the target torque. When the value does not converge to a value near the fluctuation amount, the calculation of the inter-cylinder correction coefficient is prohibited, so that the inter-cylinder correction control can be stabilized.

[0015]

FIG. 2 is a block diagram of a main part of a multi-cylinder internal combustion engine to which the control apparatus for an internal combustion engine according to the present invention is applied. FIG. 2 shows a four-cylinder spark ignition type internal combustion engine.
Two ignition plugs 22 ₁ , 22 ₂ , 22 ₃ and 22 ₄ are attached, and the combustion chamber of each cylinder is connected to an intake manifold 23 and an exhaust manifold 24, which are divided into four branches.

Each of the branch pipes on the downstream side of the intake manifold 23 is separately provided with a fuel injection valve 25 ₁ , 25 ₂ , 25 ₃ and 2.
5 ₄ is attached. The upstream side of the intake manifold 23 communicates with the intake passage 26. The first cylinder is provided with a combustion pressure sensor 27. The combustion pressure sensor 27 is a heat-resistant piezoelectric sensor that directly measures the in-cylinder pressure in the first cylinder, and generates an electric signal corresponding to the in-cylinder pressure.

The distributor 28 includes the spark plug 22
Distributing supplies each high voltage to _{1-22 4.} The distributor 28 is provided with a reference position sensor 29 that generates a reference position detection pulse signal at every 720 ° crank angle and a crank angle sensor 30 that generates a crank angle detection signal at every 30 ° crank angle. The output pulse of the crank angle sensor 30 detects the engine speed NE.

The microcomputer 31 has a central processing unit (CPU) 32, a memory 33, an input interface circuit 34, and an output interface circuit 35, which are connected by a bidirectional bus 36.
The microcomputer 31 calculates the inter-cylinder correction coefficient calculating means 11 and the torque variation correction coefficient calculating means 1 by using the microcomputer 31.
2. The correction control unit 13, the detection unit 14, and the calculation operation control unit 15 are realized.

FIG. 3 shows the structure of the first cylinder of the internal combustion engine of FIG. 2 and its vicinity. 2, the same components as those of FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 3, the air filtered by the air cleaner 40 passes through a throttle valve 42 provided in the intake passage 26, and is further distributed to the intake manifold 23 of each cylinder by a surge tank 43. when opening of the intake valve 44 after being mixed with fuel injected from the injection valve 25 ₁ is drawn into the combustion chamber 45.

The combustion chamber 45 has a piston 46 therein.
Further, it is connected to the exhaust manifold 24 via an exhaust valve 47. The combustion pressure sensor 27 described above is configured such that its tip projects through the combustion chamber 45.

The opening of the throttle valve 42 is adjusted in conjunction with an accelerator pedal (not shown). The opening of the throttle valve 42 is detected by a throttle position sensor 48. Water temperature sensor 4
A part 9 penetrates through the engine block and protrudes into the water jacket to detect the temperature of the engine cooling water. In the middle of the exhaust manifold 24, an oxygen concentration detection sensor (O ₂ sensor) 50 is provided so that a part thereof protrudes into the exhaust manifold 24. Detect oxygen concentration. The suction pipe pressure PM is detected by a vacuum sensor 53 attached to the surge tank 43. The detection signals of these sensors 48, 49, 50, 51 and 53 are input to the microcomputer 31 and stored in the memory 33.

Next, the operation of the microcomputer 31 for controlling the fuel injection amount of the present invention will be described. In this embodiment, the torque fluctuation control routine shown in FIG.
The microcomputer 31 executes an inter-cylinder correction coefficient calculation routine shown in FIG.
In this way, the above-described lean limit control is performed, and a stable cylinder-to-cylinder correction is performed.

First, the flowchart of the torque fluctuation control routine shown in FIG. 4 will be described. The torque fluctuation control routine shown in FIG. 4 is performed at, for example, 720 ° CA (crank angle).
When activated for each value VCP ₀ taken based on the electrical signal taken out from the combustion pressure sensor 27 at cylinder pressure uptake routine separately executed (No. combustion pressure) First ~V
Calculating the axial torque PTRQ with CP ₄ (step 101).

Here, the value of the combustion pressure signal VCP _0-
As shown in FIG. 5, VCP ₄ has a crank angle of BTD.
C155 ° CA (155 ° before top dead center), ATDC 5 ° C
A (5 ° after top dead center), ATDC 20 ° CA, ATDC3
The value is at 5 ° CA and at 50 ° CA ATDC. The combustion pressure signal VCP ₀ when the crank angle is BTDC 155 ° CA is used to absorb output drift due to the temperature of the combustion pressure sensor 27, variation in offset voltage, and the like.
This is used as a reference value of the combustion pressure at other crank positions.

In FIG. 5, the value of the angle counter NA is counted up every 30 ° CA interrupt, and is incremented by 360 °.
Cleared for each CA. ATDC5 ° CA, ATDC3
Since the position of 5 ° CA does not coincide with the 30 ° CA interrupt point, the timing of ATDC 5 ° CA and ATDC 35 ° CA is set to the immediately preceding 30 ° CA interrupt point (NA =
“0”, “1”) sets the 15 ° CA time in the timer,
Obtained by timer output.

In step 101 of FIG. 4, the combustion pressure C
Calculating a P _n, to calculate the axial torque PTRQ from the combustion pressure CP _n for each cylinder. That is, the combustion pressure CP _n is calculated by the following equation VCP ₀ as a reference (where, n
= 1 to 4).

CP _n = K ₁ × (VCP _n −VCP ₀ ) (1) In the above equation, K ₁ is a combustion pressure signal-combustion pressure conversion coefficient. Then, the shaft torque PTRQ is calculated for each cylinder by the following equation. PTRQ = K ₂ × (0.5 CP ₁ +2 CP ₂ +3 CP ₃ + 4CP ₄ ) (2) where K ₂ is a combustion pressure-torque conversion coefficient.

Next, the routine proceeds to step 102 in FIG. 4, where the torque fluctuation amount DTRQ between cycles is set for each cylinder based on the following equation.
Is calculated.

DTRQ = PTRQ _i−1 −PTRQ _i (3) (DTRQ ≧ 0) In other words, only in the case of a positive value out of the values DTRQ obtained by subtracting the current shaft torque PTRQ _i from the previous shaft torque PTRQ _i−1 , paraphrasing is performed. Then, only when the torque decreases, it is considered that a torque fluctuation has occurred. This is because when DTRQ is negative, it may be erroneously determined to be acceleration torque fluctuation.

As a result, assuming that the shaft torque PTRQ changes as shown in FIG. 6A, the above-mentioned torque fluctuation amount DTRQ changes as shown in FIG. 6B.

Next, the routine proceeds to step 103, where it is determined whether or not the current operating region NOAREA _i has changed from the previous operating region NOAREA _{i-1. If} not, the routine proceeds to step 104, where the determination of the torque fluctuation integration is performed. It is determined whether the condition is satisfied. It should be noted that a torque fluctuation determination value (target torque fluctuation amount) KTH described later is determined by the engine speed NE and the intake pipe pressure PM.
(Or, the intake air amount QN) is provided for each of the operating regions that regularly divide the two-dimensional map. This is because the required target torque variation differs for each operation region.

Subsequently, in step 104, it is determined whether or not a determination condition for performing torque fluctuation integration is satisfied.
The conditions under which the torque fluctuation integration is not performed include: during deceleration, during idling, during startup, during warm-up, when the exhaust gas recirculation system is on, when the fuel is cut, and a torque fluctuation value D described later.
Before TRQISM calculation, there is a time of operation in a non-learning area, and the like. Therefore, only when none of these conditions is satisfied, it is considered that the torque fluctuation integration determination condition is satisfied, and the routine proceeds to the next step 105.

The deceleration is determined when the inter-cycle torque fluctuation amount DTRQ is continuously positive, for example, five times or more. At the time of deceleration, since the torque decrease due to the decrease in the intake air amount and the torque decrease due to the combustion deterioration cannot be distinguished, the control of the engine based on the torque fluctuation amount is stopped. Step 105 In cycle between the torque fluctuation amount integrated value DTRQI _i of (torque reduction amount) is calculated based on the following equation.

DTRQI _i = DTRQI _i−1 + DTRQ (4) That is, the torque variation integrated value DTRQI up to the previous time.
_The torque fluctuation amount DTRQ calculated this time is added to _i-1 .

Next, it is determined whether the cycle number counter CDTRQI is equal to or more than a predetermined value (for example, 8) (step 10).
6) If less than a predetermined value, cycle number counter CDTR
After QI is incremented by "1" (step 10)
7) This routine is temporarily ended (step 11).
2).

By repeating the control routine of FIG. 4 a predetermined number of times (for example, eight times), the torque variation integrated value DTRQI is regarded as corresponding to a substantially accurate torque variation. Step 106
From step 108 to the next step 108, where the torque fluctuation value DTRQ
ISM is calculated based on the following equation.

DTRQISM _i = {(DTRQI _i −DTRQISM _i−1 ) / 4} + DTRQISM _i−1 (5) As can be seen from equation (5), the torque fluctuation value DTRQIS
M _i is a value obtained by subtracting 1/4 times the value obtained by subtracting the previous torque fluctuation value DTRQISM _i-1 from the current torque fluctuation amount integrated value DTRQI _i into the previous torque fluctuation value DTRQISM _i-1 . Value. The torque fluctuation value DT
The constant “4” in the calculation formula of RQISM is the value in step 1
08 may be changed according to the number of times that the step 08 is executed.

Subsequently, a torque fluctuation determination value (target torque fluctuation amount) KTH is stored in the memory 33. For example, as shown in FIG. 7, the rotational speed NE (unit: rpm) and the intake pipe pressure PM (unit: mmHg) (Step 109). This torque fluctuation determination value KTH
Represents a target torque fluctuation amount. As can be seen from FIG. 7, the value is larger as the intake pipe pressure PM increases at the same engine speed NE, and increases as the engine speed NE increases at the same intake pipe pressure PM. Is shown.

When the calculation of the torque fluctuation determination value KTH is completed, the torque fluctuation correction coefficient (air-fuel ratio correction value) KGCP of the same value for all cylinders in the operation region in which the above-mentioned DTRQI is integrated is calculated based on the following equation. Updated (step 110).

KGCP _i = KGCP _i−1 + tDLKGCP (6) As can be seen from the above equation, the current air-fuel ratio correction value KGCP _i
Is the update width t to the air-fuel ratio correction value KGCP _i-1 calculated last time.
Updated by adding DLKGCP. Note that KGCP _i may be a correction coefficient that is reflected only for the predetermined cylinder for which the torque fluctuation is detected. In that case, the correction amount of the other cylinders is reflected in the inter-cylinder correction coefficient described later.

The update width tDLKGCP is calculated from the map shown in FIG. 8 stored in the memory 33 according to which of the plurality of determination ranges the torque fluctuation value DTRQISM is in. . In FIG. 8, LVDTRQH6 to LVDTRQH1, LVD
TRQL6 to LVDTRQL1 are determination values, which are calculated from a one-dimensional map as shown in FIG. 9 stored in advance in the memory 33 using the set widths KDTRQH and KDTRQL according to the torque fluctuation determination value KTH. .

As can be seen from FIG. 9, KDTRQHk ≧
KDTRQLk (where k = 1 to 6) and K
DTRQHk and KDTRQLk are each substantially proportional to the torque fluctuation determination value KTH. Further, the set width KDTR
Based on QHk, KDTQLk and the torque variation determination value KTH, the determination value LVDTRQH in the map of FIG.
k and LVDTRQLk are calculated (where k = 1
~ 6).

LVDTRQHk = LVDTRQ + KDTRQHk (7) LVDTRQk = LVDTRQ−KDTRQLk (8) As can be seen from FIG. 8, when the torque fluctuation value DTRQISM is a value on the LVDTRQH side that is larger than the torque fluctuation determination value KTH, it is empty. Since the fuel ratio is shifted to the lean side, the value of the update width tDLKGCP is made positive, and the air-fuel ratio correction value KGCP is updated to a value larger than the previous value. As a result, the fuel injection time TAU becomes large in the TAU calculation routine of FIG. 13 described later, and the air-fuel ratio is controlled to be corrected to the rich side.

On the other hand, when the torque fluctuation value DTRQISM is a value on the LVDTRQL side that is smaller than the torque fluctuation determination value KTH, the air-fuel ratio is shifted to the rich side, so that the value of the update width tDLKGCP is made negative. The air-fuel ratio correction value KGCP is updated to a value smaller than the previous value. This allows
The fuel injection time TAU is reduced, and the air-fuel ratio is corrected and controlled to lean.

As shown in FIG. 8, the value of the update width tDLKGCP in the equation (6) in step 110 is such that the absolute value at the time of rich correction is larger than the absolute value at the time of lean correction. At the time of the rich correction, the air-fuel ratio is further deviated to the lean side from the value indicating the predetermined lean at that time, and combustion is unstable, so that it is easy to misfire, and the torque fluctuation value DTRQISM is quickly changed to the target torque fluctuation amount. At the time of lean correction, the air-fuel ratio is shifted to a rich side from a value indicating a predetermined lean state at the time of lean correction, but the combustion is stable, so that the torque fluctuation value DTRQSIM is gradually determined. By approaching the value LVDTRQ, it is possible to prevent occurrence of a sudden fluctuation in torque fluctuation.

Thus, in step 110, the torque fluctuation value DTRQISM and the torque fluctuation determination value KTH
Update width tDLKG variably set according to the relative relationship with
When the air-fuel ratio correction value KGCP _i is updated by the amount of CP, the updated air-fuel ratio correction value KGCP _i is stored in the memory 33.
Are stored in areas corresponding to each operation area which are regularly partitioned in a two-dimensional area of the engine speed NE and the intake pipe pressure PM.

As described above, when the air-fuel ratio correction value KGCP is updated in step 110 of FIG. 4, the integrated value DTRQI of the torque fluctuation and the cycle number counter C
The DTRQI is reset to “0” (step 11).
1), the process ends (step 112).

If it is determined in step 103 that the operating range has changed, it is determined that accurate lean limit control is difficult, and the routine proceeds to step 111, where the integrated value DTRQI of the torque variation and the cycle number counter are determined. CDTRQI is reset to "0", respectively, and this routine ends. Also, when it is determined in step 104 that the determination condition of the torque fluctuation integration is not satisfied, the routine proceeds to step 111, where the DTRQI and CDTRQI are reset to “0”, respectively.

According to the routine shown in FIG. 4, the cycle number counter CDTRQI changes as shown in FIG. 6C, there is no change in the operating region in step 103, and the condition for judging the integrated torque fluctuation is satisfied in step 104. When a predetermined value (a value indicated by III in FIG. 10C, for example, “8”) is reached in step 106 while the state of
It is reset in step 111. FIG.
FIG. 6D shows how the inter-cycle torque fluctuation amount DTRQ is integrated, and the value obtained by integrating DTRQ eight times is shown in FIG.
Is the torque variation integrated value DTRQI shown in FIG. FIG. 6F shows the torque fluctuation value D calculated in step 108.
The state of change of TRQSIM is shown.

As described above, according to the present embodiment, the torque variation correction coefficient calculating means 12 is executed by the routine shown in FIG.
And the air-fuel ratio correction value KGCP, which is the torque fluctuation amount correction coefficient having the same value for all cylinders, is changed to the torque fluctuation value DTRQISM.
Is approximated to the target torque variation (torque variation determination value) KTH.

Next, an inter-cylinder correction routine for realizing the inter-cylinder correction coefficient calculation means 11, the detection means 14, and the calculation operation control means 15 will be described with reference to the flowcharts of FIGS. When the inter-cylinder correction routine shown in FIGS. 10 to 12 is started at every 180 ° CA (crank angle) at which the crank angle becomes the top dead center or the bottom dead center based on the crank angle detection signal, first, the cylinder number j Calculate the 180 ° CA required time T180 _j of the combustion stroke (step 2).
01) Then, it is determined whether the timing of 720 ° CA has come (step 202). If the timing has not reached 720 ° CA, this routine ends.

When the timing of 720 ° CA is reached, the 180 ° CA required time T180 ₁ of the combustion stroke of each cylinder ignited in the order of the first, third, fourth and second cylinders at this time.
The four data of T180 ₃ , T180 ₄ and T180 ₂ are obtained, and accordingly, the process proceeds to the next step 203, where the 180 ° CA required time T180 _j of a certain cylinder and the 180 ° CA required The difference DT180 _{j from the} time T180 _j−1 is calculated for each cylinder (for example,
DT180 ₃ = T180 ₃ −T180 ₁ ). This difference D
T180 _j is a substitute parameter of the angular acceleration change amount,
When DT180 _j in the steady state is a negative value, j-th cylinder is determined that the generated torque large than j-1 cylinder of the immediately preceding combustion process.

Next, the 180 ° CA required time T180 _j
After calculating the average value T180AV (step 20)
4), DT180 corresponding to the average value of difference DT180 _j
AV is calculated based on the following equation (step 205).

[0054] _{DT180AV = (T180AV i -T180AV i-} 1) / 4 (9) In the above formula, T180AV _i is 180 ° CA duration average of all the cylinders calculated in this step 204, T180A
V _i-1 is 18 of all cylinders calculated in the previous step 204.
This is the average value of the 0 ° CA required time.

Subsequently, DT180 _j and DT18 of each cylinder are used.
Calculating the percentage WDT _j by each cylinder with respect to the average value T180AV of the difference (cancel change in overall angular acceleration) of the 0AV (step 206). This ratio WDT _j
Is a negative value, the j-th cylinder is determined to have a larger generated torque than the average of the four cylinders.

In the following step 207, the current 720 °
It is determined whether the interval between CAs is during fuel cut or in a normal fuel injection state. When the throttle valve 42 is substantially fully closed by the throttle position sensor 48 in FIG. 3 and the engine speed NE is within a predetermined range based on the crank angle detection signal from the crank angle sensor 30 in FIG. It is determined that the fuel cut is being performed, and it is determined that the fuel cut is not being performed when the operating conditions are other than the above, and step 208 is executed.

In step 208, it is determined whether or not the injection state (all-cylinder injection state) has been performed throughout the current 720 ° CA. If the injection state and the fuel cut are mixed, this routine is terminated. When the injection state is during the time of ° CA, the process proceeds to step 211 in FIG.

When it is determined that the fuel is being cut,
Proceeding to step 209 of FIG. 11, the ratio WDT _j obtained in step 206 is smoothed based on the following equation to obtain an average value WDTSMC _ji , which is stored in the memory 33.

[0059]

(Equation 1)

In the above equation, WDTSMC _ji-1 indicates the smoothed value WDTSMC calculated in the previous step 209.
When the calculation of the smoothed value WDTSMC _ji is completed, the WDT
The counter CWDTC indicating the number of updates of the SMC is incremented by "1" (step 210).

Step 211 shown in FIG. 11 is a step for realizing the detection means 14, and it is determined whether or not the torque fluctuation correction coefficient is being calculated, that is, the lean limit feedback control (CPSF / B) is being performed. During power increase,
When both the lean condition that the engine is not being warmed up, the vehicle is starting or the vehicle being accelerated, and the CPS controllable condition that the engine speed NE is within a predetermined range and the intake pipe pressure PM is within a predetermined range are both satisfied. , It is determined that CPS feedback is being performed.

For example, NE is 2400 at 800 rpm or more.
It is necessary that the rotation speed be equal to or less than the rpm. This is because it is not necessary to perform the lean operation when the rotation speed is high, so that the rotation speed fluctuates greatly when the rotation speed is low and the output of the crank angle sensor 30 is not output. Because.

When it is determined that the CPS feedback is being performed, the torque fluctuation value DTRQISM is determined by adding a predetermined value r to the torque fluctuation determination value KTH, and
It is determined whether or not the value falls within a range from a determination lower limit value obtained by subtracting r from KTH (steps 212 and 213). If the value falls within the range, the torque fluctuation value DTRQISM is determined.
Is determined to be highly likely to have converged to the target torque variation (torque variation determination value) KTH, and the routine proceeds to step 214, where the value of the CPS control convergence counter CCPSFB is set to “1”.
Increment (step 214). The initial value of the counter CCPSFB has been reset to zero by an initial routine.

On the other hand, if it is determined in step 212 or 213 that the torque fluctuation value DTRQISM is not within the above-described determination range, the process proceeds to step 215, where the torque fluctuation value DT
When RQISM is larger than KTH + α (α> r),
It is determined whether any of the conditions smaller than KTH-α is satisfied.

DTRQISM> KTH + α, DTR
If any of the inequalities QISM <KTH-α is satisfied, it is determined that the torque fluctuation value DTRQISM has not converged to the torque fluctuation determination value KTH, and the CPS control convergence counter CCPSFB is reset to “0” (step 216). When neither of the above two inequalities is satisfied, neither the increment nor the reset of the CPS control convergence counter CCPSFB is performed, the previous value is retained, and the process proceeds to step 217. Step 21
If it is determined in step 1 that the CPS feedback control is not being performed, the CPS control convergence counter CCPSFB is reset to "0" (step 216).

After the processing in steps 214 and 216 is completed, or after it is determined in step 215 that the inequality expression does not hold, the process proceeds to step 217, where the value of the CPS control convergence counter CCPSFB is equal to or greater than the predetermined value "16". It is determined whether or not. When CCPSFB <16, this routine is ended without performing convergence determination (FIG. 12).
Step 221). When CCPSFB ≧ 16, this routine is executed at least 16 times, and when it is detected 16 times in the state of KTH−r <DTRQISM <KTH + r, the torque fluctuation value DTRQISM is set to the target torque fluctuation amount (torque fluctuation). Judgment value) It is determined that KTH has converged, and the routine proceeds to the next step 218.

In this way, the above steps 212 to 212 are executed.
217 implements the calculation operation control means 15 described above, and when it is determined that the torque fluctuation value DTRQISM has converged to the target torque fluctuation amount (torque fluctuation determination value) KTH (steps 212, 213, 214, 21)
7), when the inter-cylinder correction coefficient calculation processing operation of step 218 and subsequent steps is executed and it is determined that DTRQISM does not converge to KTH (steps 215, 216, 21)
7) Without calculating the inter-cylinder correction coefficient KTAU _i ,
This routine ends (step 227).

At step 218, the ratio WDT _j of the substitute angular velocity change amount during combustion to the 180 ° CA required time is calculated based on the following equation using the ratio WDT _j obtained at step 206.
Calculate SMB _ji .

[0069]

(Equation 2)

In the above equation, WDTSMB _ji-1 represents the smoothed value WDTSMB calculated in the previous step 218. When the calculation of the smoothed value WDTSMB _ji is completed, WD
The counter CWDTB indicating the number of updates of TSMB is set to "1"
Increment (step 219).

When the processing in step 210 or 219 is completed, it is determined in step 220 whether or not the counter CWDTB is equal to or greater than "8" and the value of CWDTC is equal to or greater than "2". This routine is terminated assuming that the value is unreliable, and when this condition is satisfied, it is determined that each of the obtained values has reliability, and the process proceeds to the next step 221 shown in FIG.

In step 221, the basic injection coefficient KTAUB _j is calculated for each cylinder based on the following equation.

[0073]

(Equation 3)

However, in the above equation, (KTAU _j ) _i-1 is an inter-cylinder correction coefficient calculated in step 223, which will be described later, when this routine is started last time. Also, the basic injection coefficient K
The initial value of TAUB _j is “1.0”. Here, (1
2) As shown in equation (2), the injection state smoothing value WDTTSMB _j
The correction of the basic injection coefficient KTAUB _j according to the difference between the fuel injection and the average value WDTSMC _j during fuel cut is as follows.
This is because only the rotation fluctuation of each cylinder in the combustion state is observed by removing the error of the crank angle sensor and the like. That is, the smoothed value WDTSMC _j during the fuel cut represents the background noise of the engine rotation fluctuation when each cylinder is not in a combustion state and there is no generated torque.

Next, in order to set the average value of the inter-cylinder correction coefficient KTAU _j of each cylinder to “1.0”, the following equation is obtained in step 222.

[0076]

(Equation 4)

After calculating the deviation KCTAU of the average value of the basic injection coefficient KTAUB _j with respect to “1.0” for each cylinder, the basic injection coefficient KTAUB _{j is determined} in step 223.
Calculating the inter-cylinder correction coefficient KTAU _j each cylinder by subtracting the deviation KCTAU from. KTAU _j
Is set to "1.0" in order to prevent the average air-fuel ratio of all cylinders from being changed by the inter-cylinder correction control. Processing from the above steps 218 to 223 corresponds to the calculation process of the inter-cylinder correction coefficient KTAU _j.

Next, at step 224, | W of each cylinder
It is determined whether or not DTSMB _j −WDTSMC _j | is equal to or less than a predetermined value (for example, 0.01) for all cylinders. The cylinder-to-cylinder correction is a process for making the generated torque of each cylinder substantially the same.
When the inter-cylinder correction has been completed normally, the above | WDT
The rotation fluctuation in the combustion state represented by SMB _j −WDTSMC _j | is equal to or smaller than a predetermined value. When there is no torque variation between the cylinders, | WDTSMB _j −WDTS
_MCj | is all cylinders "0.0".

Therefore, | WDTSMB _j -WDTSMC
_{When j} | is equal to or less than the predetermined value, it is estimated that the inter-cylinder correction has been completed, and the inter-cylinder correction completion flag XKITOU is set to "1" (step 225). When the absolute value is larger than the predetermined value, the inter-cylinder correction has not been performed. Flag XKIT as complete
OU is cleared to "0" (step 226), and this processing routine ends (step 227).

Next, a fuel injection amount calculation routine for implementing the correction control means 13 will be described with reference to FIG. The fuel injection amount calculation routine shown in FIG. 13 is started at every predetermined crank angle (for example, every 360 ° CA), executes the process of step 301, and ends this routine. Intake pipe pressure PM read from memory 33 in step 301
From the data of the engine speed and the data of the engine speed NE, K · PM /
Calculating a basic injection time TP by NE (although, K is a constant), and based on the inter-cylinder correction coefficient KTAU _j and the torque variation amount correction coefficient KGCP read from the memory 33, the fuel injection time TAU _j by the following equation Calculate for each cylinder.

TAU _j = TP × KGCP × KTAU _j × A (14) In the above equation, A is a warm-up increase, a post-start increase, and other various correction coefficients.

Fuel injection is performed by the fuel injection valves 25 _{1 to} 25 ₄ of each cylinder based on the fuel injection time TAU _j . Thus, according to this embodiment calculates a correction coefficient KTAU _j between saw cylinder of when the torque fluctuation value DTRQISM is determined to have converged target torque variation (torque variation determination value) KTH near (14 ) because they performed only the fuel injection time TAU based on expression ratio WDTSMB _j of the substitute angular velocity variation can be appropriately calculated between cylinders correction coefficient KTAU _j in a state in which changes stably, thus the inter-cylinder control accuracy Can be improved as compared with the related art.

In the above-described embodiment, the torque fluctuation value DTRQISM is determined by the routines shown in FIGS.
Although the fuel injection time is controlled so that the value becomes close to the target torque variation KTH, the exhaust gas recirculation amount (EGR amount) may be controlled to obtain a desired torque variation.
In this case, a recirculation passage for exhaust gas from the exhaust manifold 24 to the intake passage 26 on the downstream side of the throttle valve 42 is provided in FIG. 3, and the degree of valve opening is controlled by the microcomputer 31 in the middle of the recirculation passage. When a switching valve (VSV) is provided and the amount of torque fluctuation is corrected to a larger value (lean correction), the VSV valve opening is set to be larger than the current valve opening and EGR is performed.
The amount may be increased, and in the opposite case, the EGR amount may be decreased.

As described above, the present invention can be widely applied to an apparatus for correcting the engine control parameters such as the fuel injection amount and the EGR amount using the inter-cylinder correction coefficient and the torque fluctuation amount correction coefficient.

[0085]

As described above, according to the present invention, the air-fuel ratio control is performed by calculating the inter-cylinder correction coefficient only when the torque fluctuation value converges to a value near the target torque fluctuation amount. It has features that the correction control can be stabilized and the accuracy of the cylinder-to-cylinder correction control can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a configuration diagram of a main part of an internal combustion engine to which an embodiment of the present invention is applied.

FIG. 3 is a sectional view showing the structure of the first cylinder and its vicinity in FIG. 2;

FIG. 4 is a flowchart showing a torque fluctuation control routine of a main part of one embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a change in a combustion pressure signal for calculating a shaft torque in the flowchart of FIG. 4 and a crank angle detection signal and the like.

FIG. 6 is a time chart for explaining the operation of FIG. 4;

FIG. 7 is an explanatory diagram of a map used for calculating a torque fluctuation determination value in the flowchart of FIG. 4;

FIG. 8 is an explanatory diagram of a map used for calculating an air-fuel ratio correction value in the flowchart of FIG. 4;

FIG. 9 is a diagram showing a map for calculating an update width used for calculating an air-fuel ratio correction value in the flowchart of FIG. 4;

FIG. 10 is a flowchart (part 1) illustrating an inter-cylinder correction routine of another main part of the embodiment of the present invention.

FIG. 11 is a flowchart (part 2) illustrating an inter-cylinder correction routine of another main part of the embodiment of the present invention.

FIG. 12 is a flowchart (part 3) illustrating an inter-cylinder correction routine of another main part of the embodiment of the present invention.

FIG. 13 is a flowchart showing a fuel injection amount calculation routine of another main part of one embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 10 multi-cylinder internal combustion engine 11 inter-cylinder correction coefficient calculation means 12 torque fluctuation correction coefficient calculation means 13 correction control means 14 detection means 15 calculation operation control means 27 combustion pressure sensor 31 microcomputer 211 torque fluctuation control detection steps 212, 213 215 Torque fluctuation value convergence determination step

Continuation of the front page (56) References JP-A-2-308949 (JP, A) JP-A-1-271165 (JP, A) JP-A-4-370346 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) F02D 45/00 330 F02D 41/14 330

Claims (1)

(57) [Claims] An inter-cylinder correction coefficient calculating means for calculating, for each cylinder, an inter-cylinder correction coefficient for equalizing the generated torque of each cylinder of a multi-cylinder internal combustion engine, and integrating a torque fluctuation amount of a generated cylinder of a predetermined cylinder for each cycle. A torque fluctuation correction coefficient calculating means for calculating a torque fluctuation correction coefficient of a predetermined cylinder or all cylinders for matching a torque fluctuation value based on the target torque fluctuation value to a target torque fluctuation amount, and correcting the engine control parameters of each cylinder between cylinders. A control device for an internal combustion engine, comprising: a correction control unit that performs correction control based on a coefficient and the torque fluctuation amount correction coefficient. A detection unit that detects whether the torque fluctuation amount correction coefficient calculation unit is executing a process, When the means detects that the processing is being performed, the inter-cylinder correction coefficient calculation is performed only when the torque fluctuation value converges to a value near the target torque fluctuation amount. Control apparatus for an internal combustion engine and having a calculating operation control means for calculating the inter-cylinder correction coefficient by stage.