JPH0668250B2 - Air-fuel ratio controller for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an air-fuel ratio control device for an internal combustion engine.

(Prior Art) Electronically controlled fuel injection type engines are actually widely used because of their high fuel metering accuracy, and in controlling the injection amount supplied from the injection valve to the engine intake system, engine load (for example, intake air) is used. The basic fuel injection amount (basic pulse width) Tp (= K · Qa / N, where K is a constant) based on the amount Qa) and the engine speed N is corrected according to other operating variables. The injection amount (injection pulse width) Ti is calculated based on the following formula (1) (see, for example, "Automotive Engineering" Vol. 34, No. 11, page 28, etc., issued by the Japan Railway Company, November 1985). .

Ti = Tp x COEF x LAMBDA + Ts (1) However, COEF: Sum of various correction factors LAMBDA: Air-fuel ratio correction factor Ts: Invalid pulse width.

(Problems to be Solved by the Invention) By the way, intake system fuel (fuel that adheres to the inner wall surface of the intake pipe or the intake port until a part of the supplied fuel reaches the engine cylinder or is not sucked into the intake pipe) The amount of (floating fuel) adhering to the intake pipe wall changes according to the operating condition of the engine, and is influenced by the engine speed, engine temperature, and the absolute pressure of the intake pipe. In conventional air-fuel ratio control, a method is used to optimize the air-fuel ratio by approximately calculating the transient fuel excess / deficiency using a previously determined correction method and performing a correction according to the engine cooling water temperature. Therefore, as described above, it is not always possible to obtain an appropriate air-fuel ratio corresponding to the amount of intake system fuel adhering to the intake pipe wall that fluctuates based on various factors. Error except when operating It was inevitable that it would occur.

In consideration of this point, Japanese Patent Application Laid-Open No. 56-47638 discloses a method in which an excessive / deficient fuel amount during intake air fuel is determined and added to the basic fuel amount. Since the actual intake surface fuel corresponding to the variable is calculated in time synchronization, the actual intake surface fuel is updated regardless of the fuel injection timing. Will not match and the control accuracy of the air-fuel ratio to the target value during the transition will deteriorate.

On the other hand, the equilibrium state quantity M0 of the intake system fuel is calculated, and this equilibrium state quantity M0 and the prediction variable M of the intake system fuel at that time are calculated.
It has been proposed that the excess and deficiency fuel amount DM as a transient correction amount be obtained based on the difference between the above and the prediction variable M and be updated in synchronization with the fuel injection (see Japanese Patent Application No. 60-24360). According to the above, the amount of fuel that is considered to be insufficient (excessive during deceleration) from one injection timing to immediately before the next injection timing during acceleration (this fuel amount is associated with changes in intake system fuel) is Since it is added at the injection timing to compensate (excess fuel is subtracted during deceleration), the accuracy of estimation of the amount of intake system fuel adhering to the intake pipe wall increases, and this highly accurate transient correction amount is used during transition. However, the accuracy of the air-fuel ratio control near the stoichiometric air-fuel ratio is greatly improved.

Since the predictive variable M of the intake system fuel and the excess / deficient fuel amount DM as the transient correction amount in the prior application are values calculated in the microcomputer and stored in the RAM, the microcomputer causes disturbance due to electromagnetic waves or the like. When received, the value up to that time may be lost, and the predictive variable M may be garbled to a small positive value or the excess / deficient fuel amount DM may be garbled to a large positive value. When the abnormality of the predictive variable M occurs in the steady state near a high load, or the abnormality of the excess / deficient fuel amount DM occurs in the steady state, the excess / deficient fuel amount DM of a large positive value is suddenly generated even though it is not the transient time. Therefore, even in this case, if the air-fuel ratio control is performed using the abnormal value of the predictive variable M and the excess / deficient fuel amount DM, the air-fuel ratio becomes a predetermined air-fuel ratio (for example, the theoretical air-fuel ratio (It is called a window within a predetermined range) and changes to the rich side, increasing NOx emissions. Further, the air-fuel ratio may change to the rich side up to the point where the flammability limit is exceeded, at which time rich misfiring occurs and the drivability deteriorates.

On the other hand, it is also possible that the predictive variable M has a large positive value and the excess / deficiency fuel amount DM has a large negative value. When an abnormality of the insufficient fuel amount DM occurs at a steady state, a large negative value of the excess / deficient fuel amount DM suddenly occurs this time. If air-fuel ratio control is performed using the amount DM, CO and HC will increase, and lean misfire will occur, resulting in poor drivability.

However, the prior application does not take into consideration the case where the predictive variable MF and the excess / deficient fuel amount DM become abnormal values due to the disturbance of the microcomputer due to electromagnetic waves or the like.

This invention is a further improvement of the previous application, and calculates the equilibrium adhesion amount of intake system fuel (corresponding to the equilibrium state amount in the previous application),
Based on the difference between the equilibrium deposit amount and the predicted value of the intake fuel deposit amount (corresponding to the predictive variable in the previous application), the deposition rate per injection (corresponding to the excess / deficient fuel amount in the previous application) )
While further updating the deposit amount prediction value in synchronism with fuel injection, it is determined whether or not one of the deposit amount prediction value and the deposit speed is within the limit width, and this limit width is deviated. If it is determined that the amount of sticking amount prediction or the speed of sticking is set to a predetermined value, the storage unit of the amount of sticking amount prediction value loses its value and becomes a very small positive value. Even if an abnormality that can be converted into a value occurs at a steady state near a high load, or if an extremely large abnormality that can be converted into a very large positive value occurs at a steady state due to the storage of the adhesion rate, the amount of NOx emissions To prevent the occurrence of a rich misfire, and the storage unit for the estimated adhesion amount loses its value and becomes a very large positive value during a steady state under low load conditions, and the adhesion speed memory Means losing its value and a very large negative Even when the abnormality garbled to occur during steady, and an object thereof is CO, emissions of HC is prevented from or cause lean misfire or increased.

(Means for Solving Problems) In order to achieve the above object, in the present invention, as shown in FIG. 1, the engine operating condition is a parameter including at least engine speed, engine load, and engine temperature. From the engine 100, means 101 for calculating the basic fuel injection amount Tp based on the operating state of the engine, and the equilibrium adhering amount MFH of the intake system fuel based on the engine speed, engine load and engine temperature.
And a means 103 for calculating a difference MFH-MFM between the equilibrium deposit amount MFH and a predicted intake fuel amount MFH at that time, and a difference M0-M for correcting the fuel injection amount. The correction coefficient KMF that indicates how much is reflected in the engine speed,
Means 104 for computing based on engine load and engine temperature;
Means 105 for calculating the adhesion speed VMF per injection based on the correction coefficient KMF and the difference MFH-MF, and the adhesion speed
VMF and the adhesion amount prediction value MF are added in synchronism with the fuel injection, and the adhesion amount prediction value MF is updated with this addition value.
Means 107 for calculating the fuel injection amount Ti by correcting the basic injection amount Tp at the adhesion speed VMF, means 108 for supplying the injection amount of fuel to the intake pipe, the adhesion amount predicted value MF or the adhesion amount Means 109 for judging whether or not any one of the speeds VMF is within the limit width, and when it is judged that the speed VMF is out of the limit width, the adhered amount predicted value MF or the adherence speed which is outside the limit width
A means 110 for setting any one of the VMFs to a predetermined value is provided.

(Operation) In the present invention, the equilibrium amount MFH of intake air fuel during engine transient
Adhesion speed VM per injection from
If F is obtained and the predicted value MF of the adhered amount is updated in synchronization with the timing of fuel injection, it will be insufficient from the injection timing of 1 to immediately before the next injection timing during acceleration (excess during deceleration). The amount of fuel that seems to be (the amount of fuel that accompanies a change in intake system fuel) is predicted, and the amount of this insufficient fuel amount is added and supplemented at the next injection timing (excess fuel amount is subtracted during deceleration. ), The accuracy of estimation of the intake system fuel quantity is always improved. Even with this highly accurate transient correction amount (that is, the adhesion speed per injection), the accuracy of air-fuel ratio control near the stoichiometric air-fuel ratio is greatly improved even during the transition.

Further, it is determined whether or not one of the adhesion amount prediction value MF and the adhesion speed VMF is within the limit width, and when it is determined that the deviation is out of the limit width, the adhesion amount prediction value outside the limit width is determined.
Either one of MF and deposition speed VMF is set to a predetermined value.

For example, when the adhesion amount predicted value MF becomes smaller than the positive limit width minimum value and becomes smaller, or when the adhesion speed VMF becomes larger than the positive limit width maximum value and becomes larger, it is limited to a predetermined value,
Abnormality that the storage means of the estimated adhesion amount MF loses its value and turns into a very small positive value occurs at a steady state near a high load, or the storage means of the adhesion speed VMF loses that value and becomes very small. Even when an abnormality that changes into a large positive value occurs in a steady state, the phenomenon that the air-fuel ratio suddenly changes greatly to the rich side immediately after the abnormality is avoided, and as a result, NOx
Increase and rich misfires are prevented.

On the other hand, when the predicted deposition amount MF becomes larger than the positive maximum limit value and becomes larger, or when the deposition speed VMF becomes smaller than the negative minimum limit value and becomes smaller, the predetermined value is set. Abnormality that the storage means of the quantity prediction value MF loses its value and turns into a very large positive value occurs at a steady state under low load condition, or the storage means of the adhesion speed VMF loses that value and a very large negative value. Even when abnormalities that change into values occur in the steady state,
Immediately after the abnormality, the air-fuel ratio does not suddenly change greatly to the lean side, and increases in CO and HC and lean misfiring are prevented.

An example will be described below.

(Embodiment) FIG. 2 shows that one fuel injection valve 24 for covering all cylinders is provided in the intake passage 22 upstream of the intake throttle valve 21 (SPI device), and an engine load signal is provided for simplification of the device. It shows a mechanical configuration when the present invention is applied to an engine that uses a throttle valve opening α (also referred to as TVO) instead of an air amount.

Therefore, in this example, the injection pulse width is controlled using α and N as basic variables (hereinafter referred to as the α-N method). Therefore, no air amount sensor is provided and the throttle valve is used instead. An opening sensor 25 is provided. In addition, the throttle valve 21
Two solenoid valves for idle-up (referred to as SV) 2 are connected in parallel in the passage 23 that bypasses the control valve 2 in order to enhance control at the time of starting.
6, 27 are provided, while a swirl control valve 28 is provided at the intake port.

The engine speed N is measured by the crank angle sensor 32 built in the distributor 31, and the cooling water temperature Tw is measured by the water temperature sensor 33.
The oxygen sensor 34 is also used as a sensor to detect the actual air-fuel ratio.
The crank angle signal (reference signal and angle signal), the water temperature signal, and the actual air-fuel ratio signal are input to the control unit 35 together with the throttle valve opening signal. The optimum fuel injection pulse width Ti is calculated based on these signals.

Next, the content of calculation of the injection pulse width Ti will be described with reference to FIG. 3 (consisting of FIG. 3A to FIG. 3C. The same applies hereinafter) to FIG. The part according to the present invention will be described below, and then the entire system will be outlined. That is, the control contents shown in these figures constitute one air-fuel ratio control system as a whole. The breakdown of these is that FIG. 3 is the main routine of the injection pulse width calculation, and FIG. 4 to FIG. This is a subroutine for obtaining the variables (transient correction amount KATHOS, feedback correction amount LAMBDA, target air-fuel ratio TFBYA, intake air temperature correction coefficient KTA) used in the main routine. The numbers in the figure represent process numbers. Such control can be easily performed by configuring the control unit 35 with a microcomputer. In this case, the calculation of each variable is executed in the control cycle shown in the table below.

A feature of the present invention is that steps 97 and 98 are provided in the routine (FIG. 4) for calculating the transient correction amount KATHOS. In other words, it is determined whether or not the adhering amount MF is below MFMIN by comparing the adhering amount of the intake system fuel (predicted adhering amount) MF with the minimum value MFMIN of its control range, and if the adhering amount MF falls below MF <MFMIN. If it is determined that the amount of sticking, MF is set to a predetermined value. Therefore, step 97 corresponds to the discriminating means 109 in FIG. 1 and step 98 corresponds to the setting means 110 in FIG.

Under the condition of MF <MFMIN, when the microcomputer is disturbed by an electromagnetic wave, the storage amount of the adhered amount (calculated value) MF loses its memory and becomes an abnormal value, so that the abnormality in the storage device of MF is determined. It is a thing. Since the value stored in the storage means when the storage means of the MF loses the storage is often a small value (for example, 0) empirically, the equilibrium adhesion amount MFH is a value that can be originally (meaning normal time). By setting the control width minimum value MFMIN (MFMIN> 0) to a value between the minimum value and 0, it is possible to judge that the memory means of the MF has lost its memory when the condition of MF <MFMIN is satisfied. is there.

When the MF storage means loses memory, a predetermined value (temporary value) is stored in the MF storage means so that the abnormal performance of the MF is used as it is, so that the driving performance and exhaust performance are not significantly affected.
Need to put. The predetermined value at this time may simply be a positive constant value, but in this example, the equilibrium adhesion amount MFH at that time is adopted. This is because the deposition amount MF deviates from the equilibrium deposition amount MFH only during the transition, and MF during the transition
Is MF after chasing MFH with the first delay and calming down to a steady state
Focuses on the agreement with MFH again.

Next, the operation in the case of such a configuration will be described during acceleration.

Since the adhesion amount MF is a value calculated in the microcomputer, the storage unit of the adhesion amount MF loses its memory when it is disturbed by electromagnetic waves. For example, in FIG. 9, when the memory is lost at the time t ₃ shown in the figure, which is settled down steadily in the state near the high load, the adhesion amount MF stored in the storage means corresponds to the state near the high load. What has been a large positive value up to becomes a small value (for example, 0) that does not reflect the operating state at that time. Difference due to this abnormality MFH
When −MF appears as a large positive value (= MFH), a VMF with a large positive value suddenly occurs from time t ₃ even though it is not during acceleration, and this causes the air-fuel ratio to change greatly to the rich side. . The state at this time is shown by the alternate long and short dash line in Fig. 9, and the magnitude of the adhesion speed VMF when an abnormality in the MF occurs during steady state under high load condition is the acceleration from the time t ₁ to t ₂ immediately before that. It is rather larger than the original deposition rate VMF that sometimes occurs. Therefore, when the above MF abnormality occurs in the feedback control region of the air-fuel ratio and the air-fuel ratio shifts out of the window and changes to the rich side, the NOx emission amount increases, and the degree of enrichment is large and the combustible mixture ratio region is increased. If it comes off, rich misfire will occur and driving performance will deteriorate.

On the other hand, in this example, when the deposition amount MF becomes a small value of 0 due to the disturbance due to electromagnetic waves to the microcomputer, the condition of MF <MFMIN is satisfied, and the equilibrium deposition amount MFH at that time is the deposition amount. Since it is entered as a temporary value of MF (steps 97, 98), the difference MFH-MF at this time is MFH-M.
F = MFH−MFH = 0, and the deposition rate VMF per deposition does not occur (see the chain double-dashed line in FIG. 9). Equilibrium adhesion amount
Even when the adhering amount MF may change to a small positive value due to disturbance due to electromagnetic waves to the microcomputer during steady operation near a high load where the MFH increases, the air-fuel ratio suddenly increases to the rich side immediately after the abnormality. The phenomenon of change can be avoided, which can prevent an increase in NOx and rich misfiring.

Next, when the entire system is outlined, the routine of FIG. 3 is a part that finally calculates the injection pulse width Ti by the following equation (4).

Here, in the SPI device, the amount of air Qc _YL flowing into the cylinder does not necessarily match the amount of air Q _AINJ passing through the injection valve, and there is a delay in the supply of fuel injected from the injection valve to the cylinder. There is an unavoidable difference, and these two points are taken into consideration in this system. However, these are calculated independently for each (Q _AINJ for air amount and transient correction amount KATHOS for fuel delay).
Ask for. ). This is to simplify the idea and clarify whether the target of the control error is the measurement error of the air amount or the fuel delay. Thereby, the accuracy at the time of setting is significantly improved. In addition, the accuracy deterioration is caused by the change with time and the difference in fuel property after the setting, so the learning function is added to these factors.

If this is expressed by a mathematical formula, the effective pulse width Te is given by the following formula (4).
Is calculated in step 70. In addition, the invalid pulse width
The sum of Ts and Te is Ti (= Te + Ts) (step 6)
9,70).

Te = (Tp x KBLRC + KATHOS x KBTLRC) x LAMBDA (4) where Tp: basic pulse width KATHOS: transient correction amount LAMBDA: air-fuel ratio correction coefficient KBLRC: basic injection amount learning correction coefficient KBTLRC: fuel delay learning correction coefficient . Here, Tp is used as the basic pulse width, but its content is calculated by the following equation (5) unlike the L-Jetronic system.

Tp = Q _AINJG × TFBYA × K (5) where Q _AINJG : injection valve air amount (mg) TFBYA: target air-fuel ratio K: constant based on injection valve characteristics (ms / mg).

First, _regarding the air amount Q _AINJ of the injection valve portion, it is difficult to directly obtain this in the present embodiment that does not have an air amount sensor, so it is obtained based on Qc _YL . That is, Q
_Considering that _AINJ can be _{approximately calculated} from Qc _YL and its variation dQc _YL / dt by the following equation (3) Q _AINJ = Qc _YL + c · dQc _YL / dt (3), (6A)
~ (6F) required.

Q _AINJG = Q _AINJ c x KTA ... (6A) Q _AINJ c = Qc _YL x Vc _YL + DCM ... (6B) Qc _YL = Q _H x K2 + Qc _YL-1 x (1-K2) ... (6C) Q _H = Q _H0 x KFLAT (6D) DCM = (Qc _YL -Qc _YL-1 ) x KMANIO x Tref (6E) KTA = KTA0 x KTAQc _YL ... (6F) However, Q _AINJG : Injection valve air amount / cylinder ( mg) Q _AINJ c: Injection valve air amount / cylinder (cc) Qc _YL : Air amount to cylinder / cylinder volume (%) Vc _YL : Cylinder volume (cc) DCM: Manifold air change amount (cc) KTA: Intake Temperature correction factor (mg / cc) Q _H : Equilibrium air amount / cylinder volume (%) K2: Change rate of Qc _YL / calculation Q _H0 : Linearized air amount / cylinder volume (%) KFLAT: Flat air-fuel ratio factor (%) KMANIO: Manifold coefficient Tref: Ref signal cycle (μs) KTA0: Basic intake air temperature correction coefficient (mg / cc) KTAQc _YL : Intake temperature correction load correction rate (%).

These formula groups (6A) to (6F) are complicated due to various corrections and standardization (converted per cylinder, per cylinder volume, etc.), but basically, Q
_AINJ c is obtained by the sum of the stationary term (Qc _YL × Vc _YL ) and the transient term (DCM). However, since this value Q _AINJ c is a volume unit and can change due to changes in intake air temperature, KTA is converted into a mass unit as a correction coefficient (steps 61 to 63).

Further, Qc _YL is obtained by a weighted average value in which K 2 is a smoothing constant, Q _H and Qc _YL-1 are variables, and K2 is a weight (steps 54 to 57).

Next, variables such as Q _H0 and K FLAT are obtained from the flow area of the intake system and the engine speed. This is because the air amount sensor is eliminated from the intake system to reduce costs and facilitate maintenance. Therefore, the flow path area is
G), (6H) (steps 41 to 52).

AADNV = AA × Tref / Vc _YL … (6G) AA ＝ ATVO ＋ AI ＋ AAC… （6H） However, AADNV: Flow path area / (rotation speed × cylinder volume)
^{(Cm 2 / rpm · cc)} AA: Soryuro area (cm ²⁾ ATVO: throttle valve flow area (cm ²⁾ AI: SV26 flow passage area (cm ²⁾ AAC: SV27 flow passage area (cm ² ) Is.

That is, this system uses the throttle valve opening TV as a load signal.
Although the flow passage area ATVO based on O is adopted, if there is a passage 23 that bypasses the throttle valve 21, these areas AI and AAC also need to be considered, and therefore the total flow passage area AA is It is given by the sum of the flow passage area ATVO based on the throttle valve opening and the flow passage area of the bypass passage (AI or AAC) (steps 41 to 49). These SVs 26 and 27 are two-position valves. This is to reduce the cost by performing four-stage control instead of using the duty-controlled solenoid valve.

Further, in actual control, a value AA / N obtained by dividing the total flow passage area AA by the rotation speed N (corresponding to the portion AA × Tref in step 52) is adopted. If this is AA as it is, N
Since it has a region that changes abruptly with respect to the change of, if this is used as a parameter, the accuracy is reduced in this region of abrupt change. However, increasing the grid points of the map in order to improve the accuracy also lengthens the calculation time. Therefore, by adopting AA / N, these control problems have been solved.

Therefore, the amount of linearization air Q _H0 is obtained by using this AADNV (= AA × Tref / Vc _YL ) (step 53). The flat air-fuel ratio coefficient KFLAT is obtained from the map using Q _H0 , N as a parameter, and the throttle valve passage area ATVO is obtained from the table using TVO as a parameter (steps 54, 42).

In addition, the basic intake air temperature correction coefficient KTA0 and the intake air temperature load correction factor KT
AQc _YL is also searched using the intake air temperatures T _A and Qc _YL as parameters, and the intake air temperature correction coefficient KTA is obtained by the product of these (steps 81 to 83 in FIG. 7).

Since the air amount Q _AINJ of the injection valve portion has been obtained by the above calculation, the next step is to obtain a correction amount for the fuel delay that occurs during the transition. This correction amount is KATHOS used in step 66, and is specifically calculated by the routine shown in FIG.

Regarding the transient correction, this example and two prior applications (Japanese Patent Application No. 60)
-243605 and Japanese Patent Application No. 61-2810) have different symbols, but the method for determining the transient correction amount KATHOS is basically Japanese Patent Application No. 60-
The correction rate GHF in this example is the same as that of the Japanese patent application No. 243605.
It corresponds to the correction rate KGI in the earlier application of 1-2810. In other words, the amount ratio KMF (which indicates how much this difference is reflected in the correction of the fuel injection amount in the difference MFH-MF between the equilibrium adhering amount MFH of the intake system fuel and the adhering amount MF of the intake system fuel at that time. The sticking speed VMF per injection is obtained by multiplying by (corresponding to the correction coefficient DK in the previous application), and the value obtained by multiplying this by the correction rate GHF that takes into account the use of light fuel is the final transient correction amount KAT.
HOS. This can be expressed mathematically by the following equations (7A) to (7
Given in E).

KATHOS = VMF x GHF ... (7A) VMF = (MFH-MF) x KMF ... (7B) MF = MF _-1REF + VMF ... (7C) KMF = (KMFAT + KMFVMF) x KMFN x KMFDBT ... (7D) GHF = GHFQc _YL x GHFFBYA (7E) However, KATHOS: Transient correction amount (μs) VMF: Adhesion velocity (μs / injection) MFH: Equilibrium adhesion amount (μs) MF: Adhesion amount (μs) KMF: Volume ratio (%) KMFAT: Basic amount Proportion (%) KMFVMF: Adhesion speed correction rate of volume ratio (%) KMFN: Rotation correction rate of volume ratio (%) KMFDBT: Boost correction rate of volume ratio (%) GHF: Correction rate (%) GHFQc _YL : Deceleration correction Rate (%) GHFFBYA: Air-fuel ratio correction rate (%). It has been described above that steps 96 to 98 in this routine are the features of the present invention.

The deposition speed VMF per injection is closer to the equilibrium deposition amount MFH of the intake system fuel at a rate at which the deposition amount MF of the intake system fuel at the present time approaches per unit cycle (for example, every one rotation of the crankshaft). The quantity ratio KMF representing the ratio is calculated by multiplying the difference between the equilibrium adhesion amount MFH and its preliminary value MF (step 103). The deposit amount MF at this time is the previous process amount of MF obtained in the process shown in FIG. 8 described later, and by subtracting this from MFH, the excess amount of fuel at the present time with respect to the equilibrium deposit amount of intake system fuel Since the amount or the deficiency is obtained, the excess or deficiency of the fuel per unit cycle (that is, the deposition rate) can be obtained by multiplying this by the quantity ratio KMF. In this case, the adhesion speed VMF takes a positive value in the acceleration state to represent the fuel shortage amount, and takes a negative value in the deceleration state to represent the fuel excess amount.

Here, the equilibrium deposit amount MFH depends on not only the basic operating variables Q _AINJ , N but also the cooling water temperature Tw, so there are a total of 3 parameters. Since there are too many parameters, a 3D map should be used as it is. I can't. So, in this example, 3
This problem is solved by a combination of the search of the dimensional map and the interpolation calculation of the linear approximation. That is, n (= 4 or 5) different reference temperatures Tw _{0 to} Twn (Tw _{0 that} are set in advance within the range of the temperature change width that the cooling water temperature Tw can actually take.
＞ _{・ ・ ・} ＞ _Twn ) for each Q _AINJ and N as parameters
For convenience of providing the adhesion amount MFHTwn at Twn, n pieces of adhesion amount data are prepared by actual measurement. Then, the upper and lower reference temperature Twk the actual water temperature Tw (integer k is from 0 to n), the adhesion amount MFHTwk, the MFHTwk + ₁ used in Twk + _1, Tw, Twk, Twk + ₁
The MFH is finally obtained by the interpolation calculation by (step 101). Although high accuracy can be obtained by the method using the map and the interpolation calculation, there is also a method that uses two tables to obtain the accuracy if the calculation speed is to be increased, and this can be calculated using the following formula (7F). Shown in.

MFHTwn = MFHQn x MFHNn (7F) However, MFHQn: _Coefficient based on Q _AINJ MFHNn: Coefficient based on N, MFHQn is obtained by table search with Q _AINJ and MFHNn with N as parameters.

Note that when Tw> Tw ₀ and Tw <Twn, interpolation calculation cannot be performed, so MFH = MFHTw ₀ . During fuel cut, MFH = FCMFH (constant value).

On the other hand, as shown in FIG. 8, the adhesion amount MF is set by adding the adhesion speed VMF of this time to the adhesion amount MF _-1REF of the previous injection (step 121). This is because VMF is the amount that represents the change in the amount of intake system fuel adhering, while MF gives the amount of intake system fuel adhering at this point, so MF should be sequentially corrected by the amount of VMF. Therefore, the MF for the next correction is predicted as MF _-1REF + VMF. The process of FIG. 8 is performed in synchronization with the fuel injection timing, and the adhered amount MF is updated at each injection timing.

Next, the volume ratio KMF may be a constant value, but in this example AAD
Basic value KMFAT by map search with NV and Tw as parameters
And the high pass value DB of VMF, N and boost pressure change
Correction based on OST is performed. That is, the basic value KMFAT
There are three correction factors for KMFVMF, KMFN, and KMFDBT, which are introduced so that the air-fuel ratio has a flat characteristic in the initial stage of the transition. That is, slight acceleration causes a slight undercorrection, and a slight deviation occurs when an experiment is performed such that an error occurs due to a difference in the number of revolutions. These are intended to be solved individually.

The high-pass value DBOST is calculated by the following equations (7G) to (7I), and the content is calculated by integrating the minute change amount of the boost pressure.
This value is gradually attenuated in synchronization with the Ref signal.

(1) When set (first time) DBOST = DBOST _-1 + (BOOST-BOOSTO) (7G) (2) When attenuated (DBOST ≥ 0) (2nd time or later) DBOST = DBOST _-1 × TGEN (7H) ( 3) During damping (DBOST <0) (2nd time or later) DBOST = DBOST _-1 × TGENG (7I) where BOOST: Boost pressure BOOSTO: Boost pressure during previous calculation TGEN: Damping coefficient during acceleration (constant) TGENG : Damping coefficient (constant) during deceleration Note that boost pressure BOOST is AADDNV, volume ratio adhesion speed correction rate KMF VMF is VMF _-1 , volume ratio rotation correction rate KMF
N is N, and the boost correction rate KMFDBT of the proportion is obtained by a table search using the absolute value of DBOST as a parameter.

Next, the correction rate GHF is a value that takes into consideration the difference in fuel properties and the like (step 105). This is because in the case of highly volatile fuel, it is vaporized rapidly due to the development of suction negative pressure during deceleration and is sucked into the engine cylinder. Less. Therefore, it is necessary to underestimate the amount of adhesion during deceleration, and conversely, a small value should be given as the correction coefficient (GHFQc _YL ). That is, during acceleration (when VMF is positive)
Is not corrected (GHFQc _YL = 1.0), but a value of 1 or less is adopted during deceleration (when VMF is negative). The target air-fuel ratio TFBYA is also corrected, and the deceleration correction rate GHFQc _YL is Qc _YL and the air-fuel ratio correction rate GHFFBYA.
Is obtained by table search using TFBYA as a parameter.

The transient correction amount KATHOS is finally obtained using the VMF and GHF thus obtained (step 106).

Next, the air-fuel ratio correction coefficient LAMBDA and the target air-fuel ratio TFBYA used in steps 68 and 64 of FIG. 3 (C) are being calculated in the conventional example, and their routines are respectively the fifth.
FIG. 6 and FIG.

That is, LAMBDA is a correction coefficient in feedback control of the air-fuel ratio. FIG. 5 shows an example of PID control, which is the deviation E between the actual air-fuel ratio (specifically, the oxygen sensor output Ip) and the target value of the air-fuel ratio (specifically, the sensor output equivalent amount T _IP of the target value).
LAMBDA is obtained by the following equations (8A) to (8D) for adding the proportional component (P), the integral component (I), and the derivative component (D) obtained based on R (steps 111 to 118).

LAMBDA = P + I + D (8A) P = K _P・ ER (8B) I = I _-1 + K _I・ ER (8C) D = K _D・ (ER-ER _-1 ) (8D) However, K _P : proportional gain K _I: integral gain K _D: a derivative gain.

The deviation ER is given by the following equation (8E) (step 11
Four).

ER = Ip−T _IP − (n + 1) (8E) where the second term of the equation (8E) is (n + 1) times before (where n is the number of cylinders) Ref signal is input. The sensor output Ip of is shown. This is because there is a time delay until the result of the air-fuel ratio set in the intake system is detected by the sensor 34 provided in the exhaust system, and this is taken into consideration.

Further, the target air-fuel ratio TFBYA is calculated using Tw, Qc _YL , N as parameters (steps 91 to 95 in FIG. 6). It should be noted that step 95 in the figure is provided with an upper limit value and a lower limit value in TFBYA and is provided with a function as a fail safe.

Next, regarding the learning correction coefficients KBLRC and KBTLRC used in steps 65 and 67 of FIG. 3C, in this example, the air amount (Q _AINJ ) and the fuel delay correction amount (KATHOS) are separated. Therefore, learning corrections are also separated and performed independently. That is, the learning correction coefficient KBLRC for the basic injection amount is the air-fuel ratio correction coefficient L
Fuel delay learning correction coefficient KBT in AMBDA calculation routine
The LRC is calculated in the calculation routine for the transient correction amount KATHOS (steps 119 and 120 in FIG. 5, steps 107 to 110 in FIG. 4).

Learning correction is basically to add a control amount based on the deviation from the target value in advance so that deviation does not occur in the next calculation.KBLRC is added to LAMBDA and KBTLRC is added.
Is the LAMBDA, the actual air-fuel ratio AFBYA, and the target air-fuel ratio TFBYA.
Is calculated based on the deviation B of (steps 119, 120, 1
07-110).

Incidentally, steady state by comparing the deposition rate VMF and the reference value L ₁ (V
It is determined whether MF <L ₁ ) or a transient time (VMF ≧ L ₁ ), and learning is performed only for a steady state for KBLRC and a transient time for KBTLRC (steps 119 and 107).

Next, FIG. 10 shows the transient correction amount KATH of the second embodiment of the present invention.
It is a flow chart which shows calculation of OS.

In the first embodiment, the target of the limit width is the adhesion amount MF, whereas in this example, the adhesion speed VMF per injection is adopted. That is, instead of immediately setting the value calculated by the product of the difference (MFH-MF) and the quantity ratio KMF as the sticking speed VMF, this is once set as the basic sticking speed VMFS, and this value VMFS is the limit width maximum. VMFS when the value exceeds VMFMAX
Insert 0 as a temporary value into the value of (step 131, 13
3).

In this example, when the condition of VMFS> VMFMAX is satisfied, it is determined that the storage means of the basic adhesion speed VMFS has lost the memory, so the limit width maximum is exceeded when the basic adhesion speed VMFS exceeds the minimum value that can be originally taken. The value VMFMAX (VMFMX> 0) may be set. For example, in Figure 11, VM at the position shown
Determine FMAX.

Note that VMFS> VMFMAX may result as a result of loss of the storage means for the adhesion amount MF, so in this example, VMFS
When FS> VMFMAX is established, the equilibrium adhesion amount MFH is put in the adhesion amount MF (steps 131 and 132). However, FIG. 11 is a waveform diagram when step 132 is not provided.

In this example as well, even if the storage means of the basic deposition speed VMFS loses its memory and an abnormality occurs that becomes a very large positive value in a steady state, the deposition speed VMF becomes 0. Similarly, the phenomenon in which the air-fuel ratio suddenly changes greatly to the rich side immediately after the abnormality is avoided, which results in NOx.
Increase and rich misfires are prevented.

By the way, in the first embodiment, only the positive limit width minimum value MFMIN is set as the limit width for the MF, and the limit width maximum value is not set. Also in the second embodiment, the positive limit width VMFS is positively limited. Only the maximum width VMFMAX is set, and the minimum width limit is not set. From experience, this means that the value of MF can only be changed to a small positive value and not to a large positive value.
This is because the value of FS cannot be turned into a very large negative value only by turning into a very large positive value.

However, if the types of storage means of the microcomputer, MF, and VMFS are different, it is theoretically possible that the value of MF becomes a large positive value or the value of VMFS becomes a very large negative value. In this case, for example, when the memory means of the MF loses its memory and changes to a large positive value at a steady state under a low load condition, the difference MFH-MF becomes large with a negative value this time, and therefore, it suddenly becomes empty. The fuel ratio changes to the lean side, and also when the VMFS memory means loses its memory during normal times and changes to a very large negative value, the air-fuel ratio suddenly changes to the lean side. When these abnormalities of MF and VMFS occur in the air-fuel ratio feedback control area and the air-fuel ratio changes to the lean side out of the window, CO and HC increase, and the degree of leaning is large and it goes out of the combustible mixture ratio area. If this happens, a lean misfire will occur and the drivability will deteriorate.

Therefore, when widely considering the difference in the types of storage means of the microcomputer, MF, and VMFS, set the maximum limit value MFMAX (MFMAX> 0) for MF and set MF> MF.
When the condition of MAX is satisfied, set MF = MFH, and set the minimum value VMFMIN (VMFMIN <0) for VMFS to VMSF <VMFMIN.
By setting VMFS = 0 when the condition of (VMFMIN <0) is satisfied,
It can prevent increase of CO and HC and lean misfire.

In the example, the minimum width limits MFMIN and VMFS for MF are also used.
Maximum limit value for VMFMAX (Maximum limit value for MF
(Also regarding the minimum limit value VMFMIN for MFMAX and VMFS)
In the above description, a constant value is used for all, but the present invention is not limited to a constant value. For example, the equilibrium deposit amount MFH, which can be taken even under the same rotation speed and the same temperature condition, varies depending on the engine load. The equilibrium deposit amount under one load condition is MFH1, which is higher than the one load condition. It is assumed that the equilibrium adhesion amount under the second load condition on the side is MFH2 and the relationship between them is MFH2> MFH1. In this case, the minimum limit width under load condition 1 is MFH1
Between 0 and 0 is sufficient, and the minimum limit width under the load condition of 2 is between MFH2 and 0. Therefore, if the operating conditions can be distinguished, it is possible to give different values to the minimum width MFMIN.

The value temporarily entered when the MF storage means loses the value in the first embodiment is not limited to the equilibrium adhesion amount MFH itself, but takes an allowable width ± ε ₁ (ε ₁ > 0) around the MFH. Is allowed. However, in this case, a difference of ± ε ₁ occurs between MFH and MF, and the adhesion velocity VMF corresponding to this difference is calculated, and the air-fuel ratio changes to the rich side or the lean side.
This air-fuel ratio variation range must be set so as not to deviate from the above-mentioned window in the air-fuel ratio feedback control region, or to deviate from the combustible mixture ratio region, for example. _Further , the same method as the calculation of the equilibrium adhesion amount MFH from the three operating variables (the injection valve air amount Q _AINJ , the rotation speed N, the cooling water temperature Tw) is used as the value to be entered when the MF storage means loses the value. You can also ask at. Even in this case, the allowable difference between MFH and MF should be within the allowable range ±
It must be contained within ε ₁ .

Similarly, in the second embodiment, the value entered when the VMFS storage means loses a value is not limited to 0, and a permissible width ± ε ₂ (ε ₂ > 0, ε ₂ ≠ ε ₁₎ centered around 0. ) Is allowed. In this case, since the air-fuel ratio change to the rich side or lean side corresponding to the allowable width ± ε ₂ occurs, it is necessary to prevent this air-fuel ratio change range from deviating from the above window or combustible mixture ratio range. . In addition, since the requirements from the operating performance and the exhaust performance for the permissible range ± ε ₂ differ depending on the operating conditions, the permissible range ± ε ₂ with different values for each operating condition.
Can also be set.

(Effects of the Invention) As described above, according to the present invention, the depositing speed per injection is based on the difference between the equilibrium depositing amount of intake system fuel and the estimated depositing amount of intake system fuel at the time of engine transient. Is calculated, and the adhesion amount prediction value is updated in synchronism with fuel injection, while it is determined whether any one of the adhesion amount prediction value and the adhesion speed is within the limit width. When it is determined that the air-fuel ratio is out of range, either one of the adhered amount predicted value and the adhered velocity is set to a predetermined value. While the storage amount of the predicted adhesion amount loses its value and changes to a very small positive value during normal operation under high load conditions, the storage device of the adhesion speed changes the value. Difference that is lost and becomes a very large positive value Even if the normal state occurs in the steady state, it is possible to prevent the phenomenon that the air-fuel ratio suddenly changes greatly to the rich side immediately after the abnormality and prevent the increase of NOx and rich misfire, and also to predict the deposit amount. An abnormality that the storage means loses its value and turns into a very large positive value occurs at a steady state under a low load condition, or an abnormality that the storage means of the adhesion speed loses that value and turns into a very large negative value is steady. Even when it occasionally occurs, the air-fuel ratio does not suddenly change greatly to the lean side immediately after the abnormality, and it is possible to prevent an increase in CO and HC and a lean misfire.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram of the present invention, FIG. 2 is a schematic diagram showing a mechanical configuration of a first embodiment of the present invention applied to an SPI device, and FIGS. 3 to 7 are schematic diagrams in FIG. FIG. 8 is a flowchart for explaining the operation contents executed in the control unit, FIG. 8 is a flowchart for explaining the operation contents synchronized with the injection timing, and FIG.
FIG. 10 is a waveform diagram for explaining the action at the time of acceleration of the above-mentioned embodiment, FIG. 10 is a flow chart for explaining the operation contents executed in the control unit of the second embodiment of the present invention, and FIG. FIG. 5 is a waveform diagram for explaining the action during acceleration of the example. 100 ... Operating state detecting means, 101 ... Basic injection amount calculating means, 102 ... Equilibrium adhesion amount calculating means, 103 ... Difference calculating means,
104: correction coefficient calculation means, 105: adhesion speed calculation means,
106 ... Adhesion amount predicted value calculation means, 107 ... Fuel injection amount calculation means, 108 ... Fuel supply means, 109 ... Discrimination means, 110 ...
… Setting means, 21 …… Intake throttle valve, 22 …… Intake passage, 23…
Bypass passage, 24 Fuel injection valve, 25 Throttle valve opening sensor, 34 Oxygen sensor (air-fuel ratio sensor), 35 Control unit.

Claims (1)

[Claims] 1. A means for detecting an operating state of an engine from parameters including at least an engine speed, an engine load and an engine temperature, a means for calculating a basic injection amount of fuel based on the operating state of the engine, and an engine speed. Means for calculating the equilibrium adhesion amount of intake system fuel based on the number, engine load and engine temperature, and means for calculating the difference between this equilibrium adhesion amount and the predicted value of the intake system fuel adhesion amount at that time, A means for calculating a correction coefficient indicating how much the difference is reflected in the correction of the fuel injection amount based on the engine speed, the engine load, and the engine temperature, and one injection per injection based on the correction coefficient and the difference. Means for calculating the adhesion speed, means for adding the adhesion speed and the adhesion amount predicted value in synchronism with fuel injection, and updating the adhesion amount predicted value with this added value, and the basic injection amount at the adhesion speed Correct and burn Means for calculating the injection amount, means for supplying the injection amount of fuel to the intake pipe, means for determining whether or not any one of the adhesion amount predicted value and the adhesion speed is within the limit width, An air-fuel ratio control apparatus for an internal combustion engine, which is provided with a means for setting either one of the predicted value of adhered amount and the adhered speed, which is out of the limit width, to a predetermined value .