JPH0670387B2 - 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, adhesion of the intake system, floating fuel (adhesion of some of the injected fuel to the inner wall surface of the intake pipe or the intake port, or floating before it reaches the cylinder) The amount of fuel that is present) occurs as a fuel delay during a transition, and this affects the control accuracy of the air-fuel ratio.

Therefore, the intake system adhesion and floating fuel equilibrium amount MFH are calculated, and this equilibrium amount MFH and intake system adhesion that changes with a first-order lag relative to this equilibrium amount, and floating fuel (this fuel is referred to as "adhesion amount" below). The difference value MFH-MF and the amount ratio indicating how much this difference value is reflected in the correction of the fuel injection amount.
Based on the KMF, the adhesion speed (adhesion amount per unit cycle) VMF is calculated, and the adhesion speed VMF and the above adhesion amount
MF and MF are added in synchronism with fuel injection, and the added value is MF
The applicant has previously proposed to update the
60-243605), this device does not detect the factors related to the adhesion amount but directly handles the adhesion amount. It has become possible to obtain air-fuel ratio characteristics.

However, experiments have shown that the adhesion of the intake system and the behavior of floating fuel are not uniform, and can be divided into fuel that changes with a relatively fast time constant and fuel that changes with a relatively slow time constant. I understood. That is, the difference in the behavior between the adhesion of the intake system and the floating fuel is divided into those that change with a relatively fast time constant (shown by a broken line) and those that change with a relatively slow time constant (shown by a dashed line). Matching was performed for each of the above fuels, and experiments were conducted based on the deposition rates obtained for each fuel.

Based on such experimental results, the present applicant has previously proposed a device that calculates a plurality of deposition rates for a plurality of types of fuels having different responses (see Japanese Patent Application No. 61-183057). . According to such a device, there is no problem at the time of setting, but if there is a difference in fuel properties or a change over time after setting, the deposition rate set by matching will not match the actual, and due to this difference the target It is conceivable that the desired air-fuel ratio cannot be obtained. For example, if the actual air-fuel ratio deviates from the target air-fuel ratio, it will lead to poor drivability and increase in harmful emissions, so make sure that the target air-fuel ratio can be obtained even if error factors occur after setting. Is desirable.

The present invention has been made in view of these conventional problems, and provides an air-fuel ratio control device provided with a learning function for calculating the adhesion speed of a plurality of intake systems having different time constants and the adhesion speed of floating fuel. The purpose is to

(Means for Solving the Problems) In the present invention, as shown in FIG. 1, an operating state detecting means 1 for detecting the operating state of the engine from parameters including at least the engine speed, the engine load and the engine temperature. , A basic injection amount calculation means 2 for calculating a basic injection amount Tp of fuel based on the operating state of the engine, and adhesion and floating of a plurality of types of intake systems having different responses based on the engine speed, engine load and engine temperature Balance amount calculation means 3 for calculating the fuel balance amount MFHi
A, 3B and a plurality of adhesions calculated by the equilibrium amount calculation means 3A, 3B,
In the difference value calculation means 4A, 4B for calculating the difference value MFHi-MFi between the equilibrium amount MFHi of the floating fuel and the plurality of attachment amounts MFi that change with a first-order lag with respect to this balance amount MFHi, and the difference value calculation means 4A, 4B. A plurality of quantity ratios KMFi indicating how many calculated difference values MFHi-MFi are reflected in the correction of the fuel injection amount, the engine speed,
Quantity ratio calculating means 5A, 5B for calculating based on the engine load and engine temperature, the adhesion speed calculating means 6A for calculating the adhesion speed VMFi based on the plurality of difference values MFHi-MFi and the plurality of quantity ratios KMFi, 6B, the adhesion speed calculation means 6A, a plurality of adhesion speeds VMFi calculated by 6B and the adhesion amount MFi are added in synchronization with fuel injection, and the adhesion amount calculation means 7A for updating the adhesion amount MFi with the added value. 7B, a plurality of learning values KBTLRCi for the plurality of adhesion speed VMFi, storage means 8A, 8B for storing in association with the engine speed and engine load, the storage means 8A, depending on the engine speed and engine load. Adhesion speed correction means 9A, 9B for correcting the adhesion speed VMFi corresponding to the plurality of learning values KBTLRCi read from 8B, and the fuel injection amount Ti based on the basic injection amount Tp and the corrected plurality of adhesion speeds. Fuel injection amount calculation means 10 for calculating and outputting an injection signal,
Fuel supply means 11 for supplying fuel to the engine based on the injection signal, and a target air-fuel ratio TFBYA based on the operating state of the engine.
Target air-fuel ratio calculation means 12 for calculating, actual air-fuel ratio detection means 13 for detecting the actual air-fuel ratio AFBYA from the exhaust of the engine, and among the plurality of adhesion speeds VMFi, which adhesion speed is currently dominant The determination means 14 for determining whether or not, the basic injection amount Tp, the target air-fuel ratio TFBYA, the actual air-fuel ratio FABYA and the shortage rate of the learning value is calculated based on the sum of the plurality of adhesion speeds VMFi, the determination The learning value calculating means 15 is provided for updating the learning value KBTLRCi for the adhesion speed determined by the means 11 according to the deficiency rate.

It should be noted that in the figure, A means
, B is attached to the means for remaining unresponsive fuel. Further, the suffix "1" is added to the symbol for one fuel having a fast response, and the suffix "2" is added to the symbols for the remaining fuels having a slow response.

(Operation) With this configuration, it is determined which _{one of the} plurality of deposition velocities VMF ₁ and VMF ₂ is currently dominant, and the learning value calculation unit 15 determines the basic injection amount Tp and the target empty space. Fuel ratio TFBYA, actual air-fuel ratio AFBYA and multiple deposition rates VMF ₁ ,
The insufficiency rate of the learned value is calculated based on the sum of VMF ₂ , and the learned value KBTLRCi for the determined adhesion speed is updated according to the insufficiency rate.

As a result, a plurality of deposition rates VMF are obtained with these learning values KBTLRCi.
₁ and VMF ₂ are finely adjusted, and even if there are differences in fuel properties or differences in atmospheric pressure and intake air temperature that are error factors after setting, a good air-fuel ratio is maintained regardless of these differences. Therefore, drivability and exhaust emission can be improved.

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 with the throttle valve opening α and the engine speed N as basic variables (hereinafter referred to as the α-N method).

Therefore, the air amount sensor is not provided, and the throttle valve opening sensor 25 is provided instead. 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 23 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.
There is no difference from the conventional device such as the provision of these crank angle signals (Ref 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, and the optimum fuel injection pulse width Ti is calculated in the control unit 35 based on these signals.

Next, regarding the calculation contents of the basic pulse width Tp and the injection pulse width Ti, refer to FIG. 3 (consisting of FIG. 3A to FIG. 3C. The same applies hereinafter) to FIG. 10 and FIG. However, the parts according to the present invention will be described first, 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, and the breakdown of these is:
3 and 12 are main routines for calculating the injection pulse width, and FIGS. 4 to 7 are variables used in the main routine (transient correction amount KATHOS, feedback correction amount LAMBDA, target air-fuel ratio TFBYA, intake air). A subroutine for obtaining the temperature correction coefficient KTA) and FIGS. 8 to 10 are routines for rewriting learning contents and learning values. 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.

Now, the feature of the present invention is to calculate the adhesion velocities VMF ₁ and VMF ₂ for the fuel that changes with a relatively fast time constant and the fuel that changes with a relatively slow time constant among the adhering and floating fuel in the intake system. Therefore, a storage means is provided for storing the plurality of learning values KBTLRC ₁ and KBTLRC ₂ for the plurality of adhesion speeds VMF ₁ and VMF ₂ in association with the engine speed and the engine load. Corresponding to the adhesion speed VMF ₁ , by a plurality of learning values KBTLRC ₁ , KBTLRC ₂ read from the storage means,
VMF ₂ is corrected, and the fuel injection amount Ti is calculated based on the basic injection amount Tp and the corrected plurality of adhesion speeds,
Of the plurality of adhesion speeds VMF ₁ and VMF ₂ , which adhesion speed is currently dominant is determined, and the basic injection amount Tp, the target air-fuel ratio TFBYA, the actual air-fuel ratio AFBYA, and the plurality of adhesion speeds VM
The point is that the learning value shortage rate is calculated based on the sum of F ₁ and VMF ₂ , and the learning value KBTLRCi for the determined adhesion speed is updated according to the shortage rate. That is, the learning routine of FIG. 8 is newly provided, and the main routine of injection control shown in FIGS. 3 and 12 is executed based on the plurality of learning coefficients KBTLRC ₁ and KBTLRC ₂ calculated in this learning routine. Then, the injection pulse width Ti of the synchronous injection described later is calculated by the following equation.

Here, the first term is the steady term, the second term is the transient term, and LAMB
DA is the air-fuel ratio feedback correction coefficient, and KBLRC is the basic injection amount learning correction coefficient. The learning correction coefficient (hereinafter simply referred to as “learning coefficient”) KBTLRC ₁ , KBTLRC ₂ for a plurality of fuels shown in the equation (4-A) is the main part of the present invention, and will be described below. is there.

First, to determine which fuel has the deposition rate is to clarify the learning target.
Since the transient correction amount KATHOS is basically equivalent to the adhesion speed VMF, the adhesion speed VMF is targeted in this embodiment. That is, when the deposition rates VMF ₁ (solid line) and VMF ₂ (dashed line) of multiple fuels with different time constants are overlapped and shown in FIG. Fuel with a time constant is dominant, and in the latter half of the transition period, fuel with a slow time constant is dominant instead. Note that the deposition rate VMF for the entire fuel is these VMF ₁ , VMF
Given by the sum of _two . Therefore, to determine which of the multiple fuels, set the reference value TVMF at an appropriate position,
It may be divided into cases where the reference value is exceeded and cases where it is below the reference value.

Therefore, in this example, each deposition rate VMF ₁ , VMF ₂ and the reference value TVMF
And VMF ₁ > TVMF and VMF ₂ > TVMF, it is determined that the deposition rate is for a fuel that changes with a fast time constant, and VMF ₁ ≦ TVMF and VMF ₂ > TVMF. It is determined that the fuel is a constant fuel (steps 133 to 136).

Next, the learning coefficients KBTLRC ₁ and KBTLRC ₂ are calculated based on the target air-fuel ratio for the adhered velocity of the identified fuel.

Here, even if there are a plurality of fuels, the learning content is the same, so for the sake of convenience of the following description, basically, a fuel that changes with a fast time constant will be described, and a fuel that changes with a slow time constant only when different To mention. Further, for convenience of explanation, “old” added before the symbol indicates a value at the time of the previous calculation, and “new” indicates a value at the time of the current calculation. Further, since the fuel-air ratio and the air-fuel ratio have an inverse relationship, the fuel-air ratio can be similarly controlled. Therefore, although the fuel-air ratio is adopted in this embodiment, the air-fuel ratio will be described. Therefore, the air-fuel ratio in the following description of the mathematical formula may mean the fuel-air ratio.

The purpose of learning is to prevent the actual air-fuel ratio AFBYA from deviating from the target air-fuel ratio TFBYA. Therefore, the ratio or deviation from the actual air-fuel ratio based on the target air-fuel ratio may be taken into the learning calculation. Therefore, in this example, the ratio is adopted to define the steady state shortage ratio R and the transient shortage ratio RTR by the following equations (steps 137, 140, 138, 141).

R = (TFBYA / AFBYA) × LAMBDA… (9A) RTR = {R (Tp + KATHOS) −Tp} / KATHOS… (9B) where Tp is the basic pulse width and KATHOS is the total transient correction amount for each of multiple fuels. (ΣKATHOSk).

First, the steady state will be explained.
Since KATHOS is almost equal to zero, by setting the transient correction amount KATHOS to zero in the previous equation (4-A),
(Former Te) is required. Note that Te = Ti-Ts.

Old Te = Tp x Old KBLRC x Old LAMBDA (9C) As a result, the actual air-fuel ratio AFBYA is AFBYA = Qa / Old Te (however, Qa is the air flow rate). ) Is substituted, and it arranges about Qa.

Qa = AFBYA x Tp x old KBLRC x old LAMBDA (9D) Also, the target air-fuel ratio TFBYA at this time of calculation is TFBYA = (Tp x new
Since KBLRC x new LAMBDA / Qa (however, this time, assuming that the air-fuel ratio has reached the target value, new LAMBDA = 1.0.), This equation is modified to obtain the new KBLRC.

New KBLRC = Qa × TFBYA / Tp… (9E) When Qa is deleted from formulas (9D) and (9E) and rearranged, new KBLRC = old new KBLRC × (TFBYA × old LAMBDA / AFBYA) = old KBLRC × R… (9F) That is, since R = new KBLRC / old KBLRC, R has a meaning as a learning coefficient deficiency rate. For example, R =
If it becomes 1.0, it means that it agrees with the target value. After all, the learning value is rewritten so that R = 1.0.

Next, regarding the transient time, since it is the transient time this time, the shortage rate R is R = new Te / old Te ... (9J). However, New Te = New Tp × New KBLRC × New KATHOS × New KBTLRC ₁ … (9K) Old Te = Old p × Old BLRC + Old KATHOS × Old KBTLRC ₁ … (9L).

These equations (9K) and (9L) are modified to summarize the new KBTLRC ₁ .

New KBTLRC ₁ = {R (old Tp x old KBLRC + old KATHOS x old KBTLRC ₁ ) -new Tp x new KBLRC} / new KATHOS… (9M) Learning coefficient deficiency ratio RTR is RTR = new KBTLRC ₁ / old KBT
Since it is LRC ₁ , the formula (9M) is substituted for this.

RTR = {R (old Tp x old KBLRC + old KATHOS x old KBTLRC ₁ ) -new Tp x new KBLRC} / (new KATHOS x old KBTLRC ₁ ) ... (9N) where, basic pulse width Tp, learning coefficient in steady state Regarding KBLRC and transient correction amount KATHOS, the following equation (9P) is obtained assuming that the new and old are almost equal.

RTR = {R (old Tp x old KBLRC + old KATHOS x old KBTLRC ₁ ) -old Tp x old KBLRC} / (old KATHOS x old KBTLRC ₁ ) ... (9P) Therefore, this formula (9P) is a strict formula for RTR. It is the best if RTR is obtained using this equation. But,
In practice, the learning direction is the same, and the shortfall (RTR
From the relationship with the detection accuracy of -1), the old KBLRC and old KBTLRC ₁ may be set to approximately 1.0, and therefore the following equation (9Q) is obtained as a practical RTR calculation equation.

RTR = (R (old Tp + old KATHOS) -old Tp) / (old KATHOS) (9Q) As described above, the correction factor RTR during the transition was calculated.

Then, the learning value is rewritten based on this RTR (steps 139 and 142). FIG. 9 shows the contents of this rewriting, and the learning coefficient KBTLRC ₁ is rewritten according to the following equation (9-B) (step 153).

KBTLRC ₁ = KBTLRC _1-1 x {1 + (RTR-1) x X _KAT } (10-a) Here, the meaning of this equation (10-a) is (RTR
-1) indicates the shortfall, and it can be rewritten by X _KAT (a constant between 0 and 1) times this shortfall. The rewriting rate X _KAT of 1.0 (100% rewriting) causes overshoot or hunting, and is a value introduced to avoid this (for example, 50%). In addition,
The rewriting method itself is publicly known, and as shown in FIG. 9, an address corresponding to the engine speed N and the amount of air Q _CYL flowing into the engine cylinder at that time is selected, and the data at that address is old. Data (KBTLRC _1-1 ) is read, new data (KBTLRC ₁ ) is calculated using this old data, and this new data is stored in the address (step
151-154).

The same applies to the fuel that changes with a slow time constant (step 142 in FIG. 8, step 161-164 in FIG. 10),
The old data (KBTLRC _2-1 ) is rewritten to the new data (KBTLRC ₂ ) by the following formula (10-b) (step 163).

(KBTLRC ₂ ) = KBTLRC _2-1 × {1+ (RTR-1) × X _KAT } (10-b) Also, considering the change characteristics of the feedback correction coefficient LAMBDA, R and RTR are actually the same as in the conventional example. Average of, ▲
▼ It is adopted.

Next, the operation in the case of being configured in this way will be described with reference to FIG. 11. Whether or not the adhering speed of a plurality of fuels is determined by comparison with the reference value TVMF,
At the initial stage of the transition, the deposition rate (VMF ₁ ) for fuel that changes with a fast time constant becomes dominant, so the deviation from the target air-fuel ratio TFBYA is learned for this deposition rate, and then the deposition rate for fuel with a slow time constant is learned. Once the velocity (VMF ₂ ) becomes dominant, this deposition rate is learned. That is, since there are a plurality of fuels having different time constants, it is necessary to calculate the learning coefficient for each fuel.

As a result, when the actual air-fuel ratio AFBYA during the transition is out of the target air-fuel ratio TFBYA as shown in the figure, this is taken into the average value ▲ ▼ and learning is performed so that there will be no deviation from the target air-fuel ratio at the next interrupt injection. (Steps 139, 142, steps 151-154 in FIG. 9, steps 161-164 in FIG. 10). For example, if the air-fuel ratio is leaner than the target air-fuel ratio, the insufficiency ratio R (or RTR)> 1, so the injection pulse width Ti increases and the fuel is increased. Conversely, if it becomes richer than the target air-fuel ratio, The amount is reduced (Note that the calculated target air-fuel ratio and actual air-fuel ratio are the reciprocals of these (target fuel-air ratio, actual fuel-air ratio), so the positions of TFBYA and AFBYA are replaced by the denominator and numerator. ing).

That is, the injection pulse width Ti In the above, since the learning coefficients KBTLRC ₁ and KBTLRC ₂ are different in fuel properties and the like, when the actual air-fuel ratio deviates from the target air-fuel ratio, it subtly changes to bring the actual air-fuel ratio close to the target air-fuel ratio.

As a result, even if there are differences in fuel properties or differences in atmospheric pressure and intake air temperature that are error factors after setting, regardless of these differences, a good air-fuel ratio can be obtained and drivability and exhaust gas can be improved. Emissions can be improved.

On the other hand, Japanese Patent Application No. 61-1830 previously proposed by the applicant.
Even with No. 57, since the actual air-fuel ratio is matched so as to match the target air-fuel ratio at the time of setting, stable air-fuel ratio characteristics can be obtained as long as there is no change over time or a difference in fuel properties thereafter. However, since it does not have a learning function, it is not possible to deal with the error factor of the air-fuel ratio that occurs after the setting. For example, even if the injection pulse width itself is the same, the substantial amount of fuel changes according to the difference in the environment in which it is used, so a difference from the fuel used for matching will result in a difference in the air-fuel ratio. . Therefore, it can be said that if there is a difference in atmospheric pressure or intake air temperature caused by a difference in fuel property or a difference between highland and lowland, the air-fuel ratio must be changed.

Next, when the entire system is outlined, the routines of FIGS. 3 and 12 finally use the following equation (4-A) to finally determine the injection pulse width Ti.
Is a part for performing the calculation of.

Here, in the SPI device, the amount of air Q _CYL 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-
A) is calculated (step 171 in FIG. 12). In addition,
The sum of Te and Te becomes Ti (= Te + Ts) with the invalid pulse width being Ts (step 69, step 171 in FIG. 12).

However, Tp: Basic pulse width KATHOS ₁ : Transient correction amount for fuel that changes with fast time constant KATHOS ₂ : Transient correction amount for fuel that changes with slow time constant LAMBDA: Air-fuel ratio correction coefficient KBLRC: Learning correction coefficient for steady state KBTLRC ₁ : A learning coefficient for transient learning for fuels that change with a fast time constant KBTLRC ₂ : A learning coefficient for transient learning for fuels that change with a slow time constant. 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 x TFBYA x 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 Q _CYL . That is, Q
_Considering that _AINJ can be _{approximately calculated} from Q _CYL and its variation dQ _CYL / dt by the following equation (3) Q _AINJ = Q _CYL + c · dQ _CYL / dt (3), the following equation group (6A)
~ (6F) required.

Q _AINJG = Q _AINJC x KTA ... (6A) Q _AINJC = Q _CYL + V _CYL + DCM ... (6B) Q _CYL = Q _H x K2 + Q _CYL-1 x (1-K2) ... (6C) Q _H = Q _H0 x KFLAT … (6D) DCM ＝ （Q _CYL −Q _CYL-1 ） × KMANIO × Tref… （6E） KTA ＝ KTA0 × KTAQ _CYL … （6F） However, Q _AINJG : Injection valve air amount / cylinder (mg) Q _AINJC : Injection valve air amount / Cylinder (cc) Q _CYL : Air amount to cylinder / Cylinder volume (%) V _CYL : Cylinder volume (cc) DCM: Manifold air change amount (cc) KTA: Intake temperature correction coefficient (mg) / cc) Q _H : Equilibrium air amount / Cylinder volume (%) K2: Change rate of Q _CYL / Calculation Q _H0 : Linearized air amount / Cylinder volume (%) KFLAT: Flat air-fuel ratio coefficient (%) KMANIO: Manifold coefficient Tref : Ref signal cycle (μs) KTA0: Basic intake air temperature correction coefficient (mg / cc) KTAQ _CYL : Intake temperature correction load correction rate (%).

These formula groups (6A) to (6F) are complicated due to various corrections and standardization (converted into per cylinder, per cylinder volume, etc.), but basically, Q
_AINJC is _{calculated as the sum} of the steady term (Q _CYL × V _CYL ) and the transient term (DCM). However, since this value Q _AINJC 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, Q _CYL is obtained by a weighted average value in which K 2 is a smoothing constant, Q _H and Q _CYL-1 are variables, and K2 is a weight (steps 55 to 57 in FIG. 3 (B)).

Next, variables such as Q _H0 and K FLAT are obtained from the flow passage 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 x Tref / V _CYL ... (6G) AA = ATVO + AI + AAC ... (6H) where AADNV = flow area / (rotation speed x 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, it is necessary to consider these areas AI and ACC as well, 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, this AADNV (= AA × Tref / V _CYL ) is used to obtain the linearizing air amount Q _H0 (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
AQ _CYL is also searched using the intake air temperature T _A and Q _CYL as parameters, and the intake air temperature correction coefficient KTA is calculated using the product of these.
Are required (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 KATHOSi (i = 1, 2) used in step 66, and is specifically calculated by the routine shown in FIG.

In this example, the adhesion velocities of a plurality of fuels having different time constants are calculated based on the difference between the adhesion amount of the intake system and the equilibrium amount of floating fuel and the calculated value of the adhesion amount that changes with a first-order lag to this equilibrium amount. Ask. When this is expressed by a mathematical formula, the following formula group (7A ~ a) ~
Given in (7E).

KATHOSi = VMFi + GHF ... (7A-a) VMFi = (MFHi-MFi) * KMFi ... (7B-a) MFi = MFi- _1Ref + VMFi ... (7C-a) KMFi = (KMFATi + KMFVMFi) * KMFNi ... (7D-a) GHF ＝ GHFQ _CYL × GHFFBYA (7E) However, KATHOSi: Overall transient correction amount (μs) VMFi: Adhesion speed (μs / injection) MFHi: Equilibrium amount (μs) MFi: Adhesion amount (μs) KMFi at this calculation KMFi: Volume ratio (%) KMFATi: Basic volume ratio (%) KMFVMFi: Adhesion speed correction rate of volume ratio (%) KMFNi: Rotational correction rate of volume ratio (%) GHF: Correction rate (%) GHFQ _CYL : Deceleration correction rate ( %) GHFFBYA: Air-fuel ratio correction rate (%).

That is, the adhesion speed VMFi is the difference value (MFHi between the equilibrium amount MFHi and the calculated adhesion amount that changes with a first-order lag relative to this equilibrium amount.
-MFi) is a coefficient KM that indicates how much the calculated value of the adhered amount approaches per unit cycle (per injection)
Calculated by multiplying by Fi (steps 103, 10
Four).

Here, the equilibrium amount MFH (MFHi) is calculated by a combination of a three-dimensional map search and a linear approximation interpolation calculation based on the air amount Q _AINJ passing through the injection valve unit, the engine speed N, and the cooling water temperature Tw. . That is, Q _AINJ and N are used as parameters for each of six different reference temperatures Tw _{0 to} Tw ₅ (Tw ₀ >...> Tw ₅ ) that are preset within the range of the temperature change width that the cooling water temperature Tw can actually take. Equilibrium amount MFH at reference temperature Twn (n = 0 to 5)
For the convenience of assigning iTwn, 12 equilibrium data are prepared by actual measurement. Then, the upper and lower reference temperature Twn of actual water temperature Tw, the equilibrium amount MFHiTwn, the MFHiTwn ₊₁ used in Twn _+1, Tw, Twn, Twn ₊₁
MFHi is finally obtained by the interpolation calculation by (step 101).

Although a high accuracy can be obtained by the method using the three-dimensional map and the interpolation calculation, there is also a method of obtaining the accuracy by using two tables when it is desired to increase the calculation speed even if the accuracy is moderate. 7F).

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

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

On the other hand, the MFi calculated this time is a value obtained by adding the adhesion speed VMFi obtained this time to MFi _-1Ref (each adhesion amount calculated immediately after the previous injection) (steps 173 and 174 in FIG. 12).

Next, the volume ratio KMFi may be a constant value, but in this example AA
Basic value KMFA by map search with DNV and Tw as parameters
Ti is calculated, and correction based on VMFi, N is performed. That is, there are two correction factors KM for the basic value KMFATi.
FVMFi and KMFNi, which are introduced so that the air-fuel ratio has a flat characteristic in the initial stage of transition.
That is, slight acceleration is slightly undercorrected, and a slight deviation occurs when an experiment is performed such that an error occurs due to a difference in the number of rotations, and these are individually solved.

Note that the deposition rate correction rate KMFVMFi for the volume ratio is VMFi and the rotation correction rate KMFNi for the volume ratio is N as a parameter, and is obtained by a table search.

Next, the correction factor GHF is a value that takes into consideration differences in fuel properties and the like. 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. For this reason, it is necessary to underestimate the amount of adhesion during deceleration, and conversely, the correction coefficient (GHFQ
_CYL ) should be given a small value.
That is, no correction is performed during acceleration (when VMFi is positive) (GHFQ _CYL = 1.0), but 1 during deceleration (when VMFi is negative).
The following numerical values are adopted. The target air-fuel ratio TFBY
Correction is also made according to A, and the deceleration correction factor GHFQ
_CYL is calculated by Q _CYL , and air-fuel ratio correction rate GHFFBYA is calculated by table search using TFBYA as a parameter.

The transient correction amount KATHOSi is finally obtained by using the VMFi and GHF thus obtained (steps 109 and 110).

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 + ER (8C) D = K _D・ (ER-ER _-1 ) (8D) However, K _P : Proportional gain K _I : Integral gain K _D : Differential gain.

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

ER = Ip-T _{IP- (n + 1)} (8E) Here, the second term of the equation (8E) is input (n + 1) times before (where n is the number of cylinders) Ref signal. The sensor output Ip 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, Q _CYL , 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, there are a plurality of learning correction coefficients KBLRC, KBTLRCi used in steps 65 and 67 of FIG. 3C, but in this example,
Since the air amount (Q _AINJ ) and the fuel delay correction amount (KATHOS) are separately calculated, the learning correction is also separated and performed independently. That is, the learning correction coefficient KBLRC in the steady state is calculated by the calculation routine of the air-fuel ratio correction coefficient LAMBDA.
KBTLRCi is calculated by the calculation routine for the transient correction amount KATHOS (steps 119 and 120 in FIG. 5, FIG. 8 to FIG. 1).
(Figure 0).

Learning correction basically prevents the deviation from occurring during the next calculation by adding a control amount based on the deviation from the target value in advance.KBLRC is added to LAMBDA and KBTLRCi
Is calculated based on LAMBDA and the deviation B of the actual air-fuel ratio AFBYA and the target air-fuel ratio TFBYA (steps 119, 120, 8th).
(Fig. 10).

Of these, the point that the learning coefficients KBTLRC ₁ and KBTLRC ₂ at the time of transition are provided is the main part of the present invention and has been described above.

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

(Effects of the Invention) As described above, according to the present invention, a plurality of types of intake systems having different responses are attached, and among floating fuels, fuel that changes with a relatively fast time constant and fuel that changes with a relatively slow time constant are used. On the other hand, while calculating a plurality of adhesion speeds, a storage means for storing a plurality of learned values for a plurality of adhesion speeds in association with the engine speed and the engine load is provided, and the learned values are stored according to the engine speed and the engine load. Then, the adhering speed corresponding to the plurality of learning values read from the storage means is corrected, and the fuel injection amount is calculated based on the basic injection amount and the corrected plural adhering speeds. , Which of the deposition rates is currently dominant, the basic injection amount,
Since the target air-fuel ratio, the actual air-fuel ratio, and the shortage rate of the learning value are calculated based on the sum of the plurality of adhesion speeds, the learning value for the determined adhesion speed is updated according to the shortage rate. Even if a difference in fuel properties or a difference in atmospheric pressure or intake air temperature, which is an error factor after setting, may occur, a good air-fuel ratio can be obtained to improve drivability and exhaust emission regardless of these differences. Can be improved.

[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 one embodiment of the present invention applied to an SPI device, and FIGS. 3 to 10 and 12 are second diagrams. FIG. 11 is a flow chart for explaining the operation contents executed in the control unit in the figure, and FIG. 11 is a waveform chart for explaining the characteristics of the learning coefficients KBTLRC ₁ , KBTLRC ₂ for a plurality of fuels in this embodiment. 1 ... Operating state detection means, 2 ... Basic injection amount calculation means,
3A, 3B: Balance amount calculation means, 4A, 4B: Difference value calculation means, 5
A, 5B ... quantity ratio calculating means, 6A, 6B ... adhesion speed calculating means, 7A, 7B ... adhesion amount calculating means, 8A, 8B ... storage means, 9
A, 9B ... Adhesion speed correction means, 10 ... Fuel injection amount calculation means, 11 ... Fuel supply means, 12 ... Target air-fuel ratio calculation means,
13 …… actual air-fuel ratio detecting means, 14 …… determining means, 15 …… learning value calculating 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.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location F02D 45/00 312 A 7536-3G 340 C 7536-3G 364 K 7536-3G (72) Inventor Uchida Masaaki 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (56) References Japanese Patent Publication 6-15828 (JP, B2)

Claims (1)

[Claims] 1. An operating state detecting means for detecting an operating state of an engine from parameters including at least an engine speed, an engine load and an engine temperature, and a basic injection for calculating a basic injection amount of fuel based on the operating state of the engine. The amount calculation means, the equilibrium amount calculation means for calculating adhesion of a plurality of types of intake systems having different responses, and the equilibrium amount of floating fuel based on the engine speed, engine load and engine temperature, and the equilibrium amount calculation means Difference value calculation means for calculating a difference value between a plurality of adhered and floating fuel equilibrium amounts and a plurality of adhered amounts that change with a first-order lag to the equilibrium amount, and a plurality of difference values calculated by the difference value calculation means A plurality of dose ratios showing how much is reflected in the correction of the injection amount,
Quantity ratio calculating means for calculating based on engine speed, engine load and engine temperature, adhesion speed calculating means for calculating adhesion speed based on the plurality of difference values and the plurality of quantity ratios, and adhesion speed calculating means The adhesion amount calculation means for adding the plurality of adhesion speeds and the adhesion amount calculated in step S1 in synchronism with the fuel injection, and updating the adhesion amount with the added value, and the plurality of learning values for the plurality of adhesion speeds are stored in the engine. Storage means for storing the rotation speed and engine load in association with each other, and adhesion speed correction means for correcting the corresponding adhesion speed by a plurality of learning values read from the storage means according to the engine speed and engine load; Fuel injection amount calculation means for calculating the fuel injection amount based on the injection amount and the corrected plurality of adhesion speeds and outputting an injection signal, and a fuel supplier for supplying fuel to the engine based on the injection signal. A target air-fuel ratio calculating means for calculating a target air-fuel ratio based on the operating state of the engine, an actual air-fuel ratio detecting means for detecting an actual air-fuel ratio from the exhaust of the engine, and one of the plurality of adhesion speeds, whichever is present. Of the learning value is calculated based on the sum of the basic injection amount, the target air-fuel ratio, the actual air-fuel ratio, and the plurality of adhesion speeds. An air-fuel ratio control apparatus for an internal combustion engine, comprising: a learning value calculation unit that updates a learning value for the adhesion speed determined by the determination unit according to the deficiency rate.