JP2920262B2 - Control device for multi-cylinder 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 a multi-cylinder internal combustion engine, and more particularly to a control apparatus for controlling an engine (for example, fuel injection amount, exhaust gas re-starting rate, etc.) so that a torque fluctuation becomes a target value after inter-cylinder correction. Circulating amount).

[0002]

2. Description of the Related Art Conventionally, a plurality of cylinders (for example, four cylinders) have been used.
A combustion pressure sensor is provided in one of the cylinders, a torque fluctuation of the cylinder is calculated from an output of the combustion pressure sensor, and the air-fuel ratio of the engine is feedback-controlled to a lean side as much as possible so that the value becomes a predetermined target value. An injection amount control device is known (JP-A-1-271634). This since the fuel injection amount control of the conventional apparatus for performing such that the torque variation amount between cycles near the lean limit value, called the lean limit control, such as the reduction of improving and nitrogen oxides in fuel economy (NO _X) It is valid.

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, in the control device for an internal combustion engine proposed by the applicant of the present invention, the air-fuel ratio of each cylinder is set so that the generated torque of each cylinder becomes uniform. Since control is performed based on the average air-fuel ratio, FIG.
As schematically shown in (A), the air-fuel ratio (A) is set in the order of the fourth cylinder # 4, the third cylinder # 3, the second cylinder # 2, and the first cylinder # 1.
/ F) has become rich from lean, and assuming that provided or the combustion pressure sensor in the first cylinder # 1, when you start the inter-cylinder correction control from the time t _1, No. 1 at time t ₂ The torque fluctuation of cylinder # 1 reaches the target value, and the air-fuel ratio becomes I
Given even after being controlled in the vicinity of the lean limit value, the air-fuel ratio of all the cylinders are gradually being controlled in the vicinity of a predetermined lean limit of the above, an empty finally all cylinders at time t ₃ as shown in The fuel ratio reaches near the lean limit.

Therefore, according to the proposed device of the present applicant, it takes time to stabilize the control, the learning speed of the cylinder-to-cylinder correction coefficient is slow, and there is a possibility that the longitudinal vibration and emission of the vehicle become excessive. There is.

The present invention has been made in view of the above points, and provides a control device for a multi-cylinder internal combustion engine which solves the above-mentioned problems by performing inter-cylinder correction based on engine control parameters of a specific cylinder. The purpose is to do.

[0011]

FIG. 1 is a block diagram showing the principle of the present invention. The present invention comprises a multi-cylinder internal combustion engine 10 comprising an inter-cylinder correction coefficient calculating means 11 for calculating an inter-cylinder correction coefficient for equalizing the generated torque of each cylinder for each cylinder, a torque variation correction coefficient calculating means 12, and a control means 13. The control device for a cylinder internal combustion engine is characterized by the configuration of the inter-cylinder correction coefficient calculation means 11.

Here, the above-mentioned torque fluctuation correction coefficient calculating means 12 calculates a torque fluctuation correction coefficient for all cylinders to make the torque fluctuation value of each cycle of the generated torque of the predetermined cylinder coincide with the target torque fluctuation. I do. The control unit 13 corrects and controls the engine control parameters of each cylinder using the inter-cylinder correction coefficient and the torque fluctuation amount correction coefficient.

The inter-cylinder correction coefficient calculating means 11
Calculates an inter-cylinder correction coefficient of each cylinder based on the engine control parameters of the predetermined cylinder.

[0014]

According to the present invention, the inter-cylinder correction coefficient calculating means 11 does not calculate the inter-cylinder correction coefficient based on the average value of the engine control parameters of all cylinders, but the cylinder based on the engine control parameters of a predetermined cylinder. Since the interval correction coefficient is calculated, the engine control parameters of the cylinders other than the predetermined cylinder can be more quickly adjusted to the engine control parameters of the predetermined cylinder.

[0015]

FIG. 2 is a block diagram of a main part of an internal combustion engine to which one embodiment of the present invention is applied. FIG. 2 shows a four-cylinder spark ignition type internal combustion engine, in which four spark plugs 22 ₁ ,
22 _2, 22 ₃ and 22 ₄ are attached, also are communicated stations each second intake manifold 23 and exhaust manifold 24 which is a combustion chamber of each cylinder is 4 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 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 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.
Each means 11 to 13 of FIG. 1 described above is realized by the microcomputer 31.

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 in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 3, the air filtered by an air cleaner 37 has its intake air amount measured by an air flow meter 38, passes through a throttle valve 39 provided in an intake passage 26, and further passes through a surge tank 40 to an intake manifold 23 of each cylinder. distributed, when opening of the intake valve 41 in the case of the first cylinder after being mixed with fuel injected from the fuel injection valve 25 ₁ here, is drawn into the combustion chamber 42.

The combustion chamber 42 has a piston 43 inside,
Further, it is connected to the exhaust manifold 24 via an exhaust valve 44. The above-described combustion pressure sensor 27 is configured so that its tip projects through the combustion chamber 42.
A throttle position sensor 45 detects the opening of the throttle valve 39 and supplies a detection signal to the microcomputer 31.

Next, the operation of controlling the fuel injection amount by the microcomputer 31 will be described. In the present embodiment, the microcomputer 31 executes the inter-cylinder correction routine shown in FIGS. 4 and 5, the torque fluctuation control routine shown in FIG. 6, and the fuel injection amount control routine shown in FIG. And the time required until the control is stabilized is controlled as short as possible.

First, an inter-cylinder correction routine will be described. FIG. 4 is a flow chart showing the outline of the inter-cylinder correction routine.
1) The cylinder whose generated torque is larger than the average among the four cylinders is determined.

Next, an inter-cylinder correction coefficient KTAU _j (where,
j is the cylinder number) for each cylinder (step 10)
2). This step 102 corresponds to the inter-cylinder correction coefficient calculating means 11.

[0024] Then, the process proceeds to step 103, the decision is whether the inter-cylinder correction coefficient KTAU _j calculated parameters between cylinders corrected based on the using is complete. If the inter-cylinder correction has been completed, the inter-cylinder correction completion flag XK
ITOU is set to "1" (step 104), and this routine ends (step 106). On the other hand, if the inter-cylinder correction has not been completed, the flag XKITO
U is set to "0" (step 105), and this routine ends (step 106).

Next, the inter-cylinder correction routine will be described in further detail with reference to FIG. In the cylinder-to-cylinder correction routine shown in FIG.
When the engine is started every time, first, 18
The 0 ° CA required time T180 _j is calculated (step 20).
1) Subsequently, it is determined whether the timing of 720 ° CA has come (step 202). If the timing has not reached 720 ° CA, this routine is ended.

When the timing of 720 ° CA is reached,
Ignition in order of No. 1, No. 3, No. 4 and No. 2 cylinders
180 ° CA required time T180 for combustion stroke of each cylinder₁,
T180_Three, T180_FourAnd T180_TwoFour data
Is obtained, so that the process proceeds to the next step 203.
180 ° CA required time T180 of cylinder_jAnd just before burning
180 ° CA required time T180 of cylinder to be processed_j-1When
Difference DT180_jIs calculated for each cylinder (for example,
DT180_Three= T180_Three-T180₁). This difference D
T180_jIs a parameter that substitutes for angular acceleration.
DT180 in the state _jIs negative, cylinder j is
Judgment that generated torque is greater than cylinder j-1 in the immediately preceding combustion process
Is done.

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).

[0028] DT180AV = 1/4 in _{(T180AV i -T180AV i-1)} (1) above equation, 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 39 is substantially fully closed by the throttle position sensor 45 in FIG. 3 and the engine speed is within a predetermined range based on the crank angle detection signal from the crank angle sensor 30 in FIG. Is determined to be in step 2
09 is executed, and it is determined that the fuel cut is not being performed in cases other than the above-described operating conditions, 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 maintained during the time of ° CA, the routine proceeds to step 210.

In step 209, 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.

[0033]

(Equation 1)

Here, WDTSMC _ji-1 in the above equation 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 211).

On the other hand, in step 210, step 2
In step S 06, the average WDT _j is obtained by performing an averaging process based on the following equation to obtain an average value WDTTSMB _ji , which is stored in the memory 33.

[0036]

(Equation 2)

In the above equation, WDTSMB _ji-1 indicates the smoothed value WDTSMB calculated in the previous step 210. 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 212). Steps 201 to 212 described above correspond to the processing for determining the priority between cylinders in step 101 in FIG.

When the processing of step 211 or 212 is completed, it is determined in step 213 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, the obtained values are deemed to have reliability and the process proceeds to the next step 214.

In step 214, the basic injection coefficient KTAUB _j is calculated for each cylinder based on the following equation.

[0040]

(Equation 3)

However, in the above equation, (KTAU _j ) _i-1 is an inter-cylinder correction coefficient calculated in step 215, which will be described later, when this routine was started last time. Also, the basic injection coefficient K
The initial value of TAUB _j is “1.0”.

Here, as shown in the equation (4), the basic injection coefficient KT is determined in accordance with the difference between the smoothed value WDTSMMB _j in the fuel injection state and the smoothed value WDTSMC _j during fuel cut.
AUB _j is corrected in order to remove the friction of each cylinder and see only the rotation fluctuation of each cylinder in the combustion state. That is, the average value WD during fuel cut
TSMC _j represents the rotation fluctuation due to friction when each cylinder is not in a combustion state and there is no generated torque.

Next, an inter-cylinder correction coefficient KTAU _j of each cylinder is calculated for each cylinder based on the following equation.

KTAU _j = KTAUB _j −KTAUB1 + 1 (5) That is, the cylinder-to-cylinder correction coefficient KTAU _j of each cylinder is the basic injection coefficient K of each cylinder calculated for each cylinder in step 214.
This is a value obtained by adding a constant “1” to a value obtained by subtracting the basic injection coefficient KTAUB1 of the first cylinder (j = 1) to which the combustion pressure sensor 27 is attached from TAUB _j , and is the basic injection coefficient KTAUB1 of the first cylinder. Is used as a reference, another inter-cylinder correction coefficient KTAUB _j is determined.

The processing from steps 213 to 215 is the cylinder-to-cylinder correction coefficient KTAUB in step 102 in FIG.
_j calculation processing, that is, the inter-cylinder correction coefficient calculation means 11
Is equivalent to

Next, at step 216, | 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 217). 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 218), and this processing routine ends (step 219). The processing in step 217 corresponds to the processing in step 103 in FIG. 4, and steps 217 and 218 are steps 104 and 105.
Is equivalent to

Next, a description will be given of a torque fluctuation control routine for lean limit control. FIG. 6A is a flowchart showing the main routine of the torque fluctuation control.
It is started every 20 ° CA. FIG. 6B shows a routine for taking in-cylinder pressure, wherein a predetermined crank angle (for example, 3
The electric signal (combustion pressure signal), which is started by interruption every 0 ° CA) and is input from the combustion pressure sensor 27 to the input interface circuit 34, is subjected to analog-to-digital conversion (A / D conversion) (step 401). The stored digital data is stored in the memory 33.

That is, based on the crank angle detection signal, the crank angle becomes BTDC 155 ° CA (1 before top dead center).
55 °), ATDC 5 ° CA (5 ° after top dead center), ATD
C20 ° CA, ATDC 35 ° CA and ATDC 50 °
At each timing of CA, the digital data of the combustion pressure signal at that time is loaded into the memory 33, respectively.

FIG. 8 shows the relationship between the change of the combustion pressure signal and the crank angle detection signal at this time. When the crank angle is BTDC 155 ° CA, the combustion pressure signal VCP ₀ is
In order to absorb output drift due to the temperature of the combustion pressure sensor 27, variations in offset voltage, and the like, the reference value of the combustion pressure at another crank position is used.

When the crank angle is ATDC5 ° CA, ATD
C20 ° CA, ATDC 35 ° CA and ATDC 50 °
FIG. 8 shows VCP ₁ , VCP
_2, represented by VCP ₃ and VCP _4. In FIG. 8,
NA counts up every 30 ° CA interrupt, and 36
This is the value of the angle counter NA that is cleared every 0 ° CA. Since the positions of ATDC5 ° CA and ATDC35 ° CA do not coincide with the 30 ° CA interrupt point, ATDC5 ° CA
In the A / D conversion at 35 ° CA, ATDC 35 ° CA, the 15 ° CA time is set in the timer at the time of the 30 ° CA interrupt (NA = “0”, “1”) immediately before the A / D conversion.
To be interrupted.

On the other hand, the main routine of FIG.
When activated at every 0 ° CA, the shaft torque is calculated by the following method based on the five combustion pressure data taken in step 401 (step 301).

First, the combustion pressure CP based on VCP ₀
Calculate _n (where n = 1 to 4).

CP _n = K ₁ × (VCP _n −VCP ₀ ) (6) In the above equation, K ₁ is a combustion pressure signal-combustion pressure conversion coefficient. Next, 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 ) (7) In the above equation, K ₂ is a combustion pressure-torque conversion coefficient.

Next, the process proceeds to step 302 of FIG.
The torque fluctuation amount D between cycles for each cylinder based on the following equation
Calculate TRQ.

DTRQ = PTRQ _i−1 −PTRQ _i (DTRQ ≧ 0) (8) That is, 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 , in other words, Then, only when the torque decreases, it is considered that a torque fluctuation has occurred. This is because when DTRQ is negative, it can be considered that the torque is changing along with the ideal torque.

As a result, assuming that the shaft torque PTRQ changes as shown in FIG. 9A, the above-mentioned torque fluctuation amount DTRQ changes as shown in FIG. 9B.

Next, the routine proceeds to step 303, 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 the next step 304 where the fluctuation determination condition is set. Is determined. Note that a torque fluctuation determination value (target torque fluctuation amount) KTH described later is provided for each operation region. The conditions under which the torque fluctuation determination is not performed include: during deceleration, during idling, during startup, during warm-up, during EGR on, during fuel cut, before the calculation of a smoothed value TH of torque fluctuation described later, in the non-learning region. And when driving. Therefore, when neither of these conditions is satisfied, the process proceeds to the next step 305 by regarding the condition as the torque fluctuation determination condition.

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. The integrated value DTRQ10 _i in step 305 in the cycle between the amount of torque fluctuation is calculated based on the following equation.

DTRQ10 _i = DTRQ10 _i−1 + DTRQ (9) That is, the torque variation integrated value DTRQ10 up to the previous time.
_The torque fluctuation amount DTRQ calculated this time is added to _i-1 .

Next, it is determined whether or not the cycle number CYCLE10 is equal to or greater than a predetermined value (for example, 10) (step 306).
If less than the predetermined value, the cycle number CYCLE10 is set to "1".
After the increment (step 307), this routine ends, and the above processing is started again.

By repeating the main routine of FIG. 6A a predetermined number of times in this way, the torque variation integrated value is regarded as corresponding to a substantially accurate torque variation. Next step 3
In step 08, the torque fluctuation value TH is calculated based on, for example, the following equation. TH = {1/16} × (DTRQ10 _i −TH _i−1 ) + TH _i−1 (10) As can be seen from the equation (10), the torque fluctuation value TH is replaced by the previous torque fluctuation value TH _i−1 Torque fluctuation integrated value DT
This is a smoothed value reflecting a value that is 1/16 times the value obtained by subtracting the previous torque fluctuation value TH _i-1 from RQ10 _i .

When the calculation of the torque fluctuation value TH is completed, the target torque fluctuation KTH is calculated from a two-dimensional map of the engine speed and the intake air amount stored in the memory 33 (step 309). Subsequently, the torque fluctuation value TH becomes
(i) KTH-α <TH <KTH, (ii) TH ≧ KTH, (i
ii) A torque fluctuation determination is made as to whether TH ≦ KTH-α (step 310). Here, α indicates the width of the dead zone.

In the case (i), the torque fluctuation value TH is within the dead zone. In this case, the correction value is left as it is, the cycle number is reset, and the routine of FIG. 312, 314). On the other hand,
In the case of (ii) and (iii), the process proceeds to step 311 to update the correction value KGCP of the fuel injection amount.

This KGCP corresponds to the torque variation correction coefficient, which is a coefficient having the same value for all cylinders, and step 311 corresponds to the torque variation correction coefficient calculating means 12. That is, in step 311, in the case of (ii), the torque fluctuation value TH is shifted to the side where the torque fluctuation is larger than the target torque fluctuation KTH, and in this case, the torque fluctuation correction coefficient is A certain fuel injection amount correction value KGCP is increased as shown by the following equation to perform rich correction.

KGCP _i = KGCP _i-1 +0.01 (11) In step 311, in the case of (iii), when the torque fluctuation value TH is shifted to the side where the torque fluctuation amount is smaller than the dead zone. In this case, the fuel injection amount correction value KGCP is made small as shown by the following equation to perform lean correction.

KGCP _i = KGCP _i−1 −0.01 (12) Note that in equations (11) and (12), KGCP _i−1 is the previous correction value,
KGCP _i indicates the current correction value.

The fuel injection amount correction value KGCP calculated in step 311 is, for example, as shown in FIG. 10, a two-dimensional map in the memory 33 composed of the engine speed NE and the smoothed value QNSM of the intake air amount is regularly stored. Learning area K divided into
Of ₀₀ ~K _34, it is updated stored in the corresponding learning region.

When the process of step 311 is completed, the value of the cycle number CYCLE10 is reset to zero (step 312), and this routine is terminated (step 314). When it is determined in step 303 that the operating range has changed, or when it is determined in step 304 that the torque fluctuation determination condition is not satisfied, the process proceeds to step 313, where the torque reduction amount, that is, the torque reduction amount calculated in step 305 is calculated. After resetting the integrated value DTRQ10 of the previous inter-cycle torque variation,
Proceeding to 2, the cycle number CYCLE10 is reset, and the routine ends (step 314).

By the torque fluctuation correction routine shown in FIG. 6A, the cycle number CYCLE10 changes as shown in FIG. 9C, and a predetermined value to be compared in step 306 (shown by III in FIG. 9C). When the value reaches, for example, "10", it is reset in the step 312. FIG. 9 (D) shows how the inter-cycle torque variation DTRQ is integrated, and the value obtained by integrating DTRQ ten times is shown in FIG.
This is the integrated value DTRQ10 shown in (E).

Next, a fuel injection amount control routine for realizing the control means 13 will be described with reference to FIG. FIG.
Is started at every predetermined crank angle (for example, every 360 ° CA), the processing of step 501 is executed, and this routine is ended. Step 50
The basic injection time TP is calculated by K · QN / NE (where K is a constant) from the intake air amount data QN read from the memory 33 and the data of the engine speed NE in step 1, and further read from the memory 33. Inter-cylinder correction coefficient KTAU
_{Based on j} and the fuel injection amount correction value KGCP, the fuel injection time TAU _j is calculated for each cylinder by the following equation.

TAU _j = TP × KGCP × KTAU _j × A (13) In the above equation, A is an increase in warm-up, an increase after startup, and other various correction coefficients.

[0074] The fuel injection is performed by the fuel injection valve 25 ₁ to 25 ₄ of each cylinder based on the fuel injection time TAU _j. Therefore, when the torque fluctuation value TH is within a dead zone between the target torque fluctuation amounts KTH and KTH-α, the fuel injection amount correction value KGCP is a value within a predetermined range,
Fuel injection is performed such that the air-fuel ratio becomes as lean as possible.

When TH ≧ KTH, the correction value KGCP is increased by the equation (11), so that the fuel injection time TAU of the equation (13) is increased, so that the fuel injection amount is increased and the air-fuel ratio is increased. Is corrected to the rich side, and the torque variation TH becomes K
Control is performed in such a manner that the amount of torque fluctuation below TH is reduced. On the other hand, when TH ≦ KTH−α, the correction value KG is calculated by the equation (12).
By reducing the CP, the TAU is shortened,
Since the fuel injection amount is small, the air-fuel ratio is corrected to the lean side, and the torque fluctuation value TH is controlled in a direction in which the torque fluctuation amount is larger than KTH-α. In this way, lean limit control is performed.

In the present embodiment, the combustion pressure sensor 27
Correction coefficient K of each cylinder other than the first cylinder provided with
TAU2 to KTAU4 are the basic injection coefficient KT of the first cylinder
Since it is determined based on AUB1 (steps 213 to 215 in FIG. 5), the time from the start of the inter-cylinder correction coefficient control until the air-fuel ratio controlled by the fuel injection amount control routine in FIG. It can be shorter than the proposed device of the present applicant.

That is, as schematically shown in FIG. 11B, similarly to FIG. 11A, the fourth cylinder # 4 and the third cylinder #
The air-fuel ratio (A / A) is in the order of the third and second cylinders # 2 and # 1.
F) has become rich from lean, from time t ₁ as that initiated the inter-cylinder correction, the No. 1 cylinder # 1 of the torque fluctuation at the time indicated by t ₂ in FIG. (B) reaches the target value ,
The air-fuel ratio is controlled near the lean limit as indicated by I.

On the other hand, torque fluctuations of the other cylinders # 2 to # 4 also
Control is performed to reach the target value with reference to cylinder # 1.
As shown schematically in FIG. 11B,
Time t _Two, The air-fuel ratio becomes near the lean limit value. Therefore, the book
According to the embodiment, the control stabilization time (t_Two-T₁) And
Therefore, compared to the above-mentioned proposed device of the present applicant,
Time can be shortened.

In particular, when the speed of the torque fluctuation control by the combustion pressure sensor is faster than the speed of the inter-cylinder correction control,
This embodiment, in which the speed of the cylinder-to-cylinder correction control is faster than in the past, is effective.

In the above embodiment, step 31
1 and the fuel injection amount calculation routine of FIG. 7, the torque fluctuation value TH becomes the target torque fluctuation amount KTH.
Although the fuel injection amount is controlled to have a value close to the value, the exhaust gas recirculation amount (EG
R amount) may be controlled. In this case, in FIG. 3, an exhaust gas recirculation passage from the exhaust manifold 24 to the intake passage 26 downstream of the throttle valve 39 is provided, and the microcomputer 3 is provided in the middle of the recirculation passage.
A vacuum switching valve (VSV) whose opening degree is controlled by 1 is provided, and when the torque fluctuation amount is corrected to a larger value, the VSV opening degree is made larger than the current opening degree and the EGR amount is increased. do it. As described above, the present invention can be widely applied to a device that corrects 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.

[0081]

As described above, according to the present invention, the inter-cylinder correction of each cylinder is calculated based on the engine control parameters of the specific cylinder, so that the inter-cycle fluctuation of the specific cylinder is the target torque fluctuation. It is possible to improve the responsiveness from the time when the amount reaches the amount until the generated torque of each cylinder becomes equal.Therefore, during the learning of the inter-cylinder correction coefficient, the possibility of occurrence of vibration in the longitudinal direction of the vehicle and excessive emission may be reduced. It has such features that it can be greatly reduced.

[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 view showing a structure of a first cylinder of the internal combustion engine of FIG. 2 and its vicinity.

FIG. 4 is a flowchart illustrating an outline of an inter-cylinder correction routine according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating details of an inter-cylinder correction routine according to an embodiment of the present invention.

FIG. 6 is a diagram showing a torque fluctuation control routine and the like according to an embodiment of the present invention.

FIG. 7 is a diagram showing a fuel injection calculation routine.

8 is a diagram showing a relationship between a change in a combustion pressure signal for calculating a shaft torque in FIG. 6 and a crank angle detection signal and the like.

FIG. 9 is a time chart for explaining the operation of FIG. 6;

10 is a learning area in which a fuel injection amount correction value KGCP calculated in the routine of FIG. 6 is stored.

FIG. 11 is a diagram showing a comparison between a device previously proposed by the present applicant and a change in air-fuel ratio by the inter-cylinder correction control of the present embodiment.

[Explanation of symbols]

 Reference Signs List 10 multi-cylinder internal combustion engine 11 inter-cylinder correction coefficient calculating means 12 torque fluctuation amount correction coefficient calculating means 13 control means 27 combustion pressure sensor 31 microcomputer

Continuation of front page (56) References JP-A-2-308949 (JP, A) JP-A-2-61145 (JP, A) JP-A-2-30956 (JP, A) JP-A-2-64252 (JP) JP-A-1-106958 (JP, A) JP-A-2-277947 (JP, A) JP-A-62-17342 (JP, A) JP-A-4-224259 (JP, A) JP-A-1-271634 (JP, A) JP-A-63-202751 (JP, U) JP-A-63-202771 (JP, U) JP-A-63-83445 (JP, A) U) Japanese Utility Model 2-69075 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 41/00-45/00

Claims (1)

(57) [Claims] An inter-cylinder correction coefficient calculating means for calculating an inter-cylinder correction coefficient for equalizing the generated torque of each cylinder of a multi-cylinder internal combustion engine for each cylinder, and a target for a torque variation value of a generated cylinder of a predetermined cylinder for each cycle. Torque fluctuation correction coefficient calculating means for calculating a torque fluctuation correction coefficient for all cylinders to match the torque fluctuation, and an engine control parameter of each cylinder is corrected by the inter-cylinder correction coefficient and the torque fluctuation correction coefficient. A multi-cylinder internal combustion engine control device comprising: a control unit that controls the inter-cylinder correction coefficient calculation unit, wherein the inter-cylinder correction coefficient calculation unit calculates an inter-cylinder correction coefficient of each cylinder based on an engine control parameter of the predetermined cylinder. Control device for a multi-cylinder internal combustion engine.