JPH0742878B2 - 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, a method of predicting the intake air amount from the throttle valve opening α for adjusting the intake air amount and the rotation speed N (hereinafter referred to as α-N system) and fuel is used. When one or more injection valves are attached to the collective portion of the intake passage that is far from the engine cylinder (hereinafter referred to as "SPI (single point injection)"), the intake air amount is controlled for injection pulse width control. Between the error due to the measurement of fuel and the error due to fuel delay
Two factors are complicatedly entangled, and this reduces the control accuracy of the injection pulse width.

Here, in order to obtain the air-fuel ratio which is the same as that in the steady state even in the transient state, it is necessary to supply the fuel amount in proportion to the air amount passing through the injection valve portion.

First, when considering the measurement of the air amount, even when the SPI is measuring the air amount with the air flow meter, this sensor can also measure the air amount that flows during a transition, so the air flow meter detects it as the air amount of the injection valve. The amount of air to be used may be used after the response delay of the air flow meter is corrected.

However, in the α-N method, it is possible to obtain the steady-state air amount of the throttle valve portion from the throttle valve opening degree, but it is not possible to obtain the air amount of the throttle valve portion flowing during the transition. For example, the steady-state air amount Qth of the throttle valve portion is Qth = g × A {(2κ / (κ−1)) × Pa × ρ × ((Pm / pa) ^{2 /} κ− (Pm / Pa) ^{(κ -1) / κ} )} ^1/2
(11) However, it is known that A: flow area of the throttle valve Pa: atmospheric pressure Pm: intake pipe negative pressure ρ: air density κ: constant If the flow passage area A of the throttle valve portion is obtained, Qth can be obtained from the equation (11), but the equation (11) is only the air amount in the steady state, not the air amount in the transition. Therefore,
If equation (11) is used even during the transition, an error will occur in the air amount measurement during the transition.

In order to cope with this, in the α-N system and SPI, a method has been proposed in which the air amount in the injection valve section is obtained as follows (Japanese Patent Application No. 61-181102).

In this first prior application device (details will be described later in the embodiment of the present application), from the throttle valve opening TVO to the equilibrium flow rate Qh of the throttle valve portion.
Then, calculate the cylinder air flow rate QcyI from this Qh using the formula Qcy1 = Qh x K2 + Qcy1 _-1 x (1-K2) (12) where K2 is the weighted average coefficient (first-order lag). The cylinder air flow rate Qcy1 matches Qh in a steady state, but even if Qh increases stepwise during acceleration, Qcy1 has a delayed response, so Qcy1 is approximated by a first-order delay of Qh.

However, equation (12) does not consider the air volume in the manifold that exists downstream of the throttle valve. Therefore, for example, at the time of acceleration, only the amount of air change ΔCM in this manifold
Injection valve air amount (equal to throttle valve air amount) than Qcy1
Qainj is more (decreasing on the contrary when decelerating).
In other words, Qainj can be obtained by the equation Qainj = Qcy1 + ΔCM (13).

Here, ΔCM can be given by the following formula: ΔCM = (Qcy1−Qcy1 ₋₁ ) × K1 × Tref (14) where K1: Manifold coefficient Tref: Ref signal period. The amount of change in the cylinder air flow rate (Qcy1-Qcy1 _-1 ) considers the degree of acceleration (or deceleration). The greater the degree of acceleration, the more (Qcy1-Qc
The value of y1 _-1 ) becomes large and gives a large value of ΔCM.

By obtaining the injection valve air amount Qainj in this way, α
Even in the -N system and SPI, the air amount passing through the injection valve portion can be accurately obtained without providing an air amount sensor and even during a transition.

Further, in the first prior application device, the basic injection pulse width Tp is Tp = Qainj × K (15) However, by giving the expression of K: injection pulse conversion coefficient It should be possible to obtain the fuel ratio.

On the other hand, not all the fuel injected from the injection valve is carried on the air flow and sucked into the cylinder, but a part of the injected fuel is
It adheres to the wall of the intake pipe downstream of the injection valve and becomes liquid, forming a so-called fuel wall flow that flows along the wall surface. Even if such a fuel wall flow exists, in a steady state, the amount of fuel that is deprived from the injected fuel as a fuel wall flow and the amount that flows into the cylinder in the state of the fuel wall flow coincide with each other, so that fuel feeding does not occur.

Here, the fuel wall flow rate depends on the suction negative pressure, the rotation speed, and the temperature, and decreases as the suction negative pressure increases. For this reason, during acceleration in which the state of strong suction negative pressure changes to the state of atmospheric pressure, the injected fuel is deprived of an increase in the fuel wall flow, and the amount of fuel flowing into the cylinder is insufficient. The air-fuel ratio leans toward the lean side (the air-fuel ratio leans toward the rich side during deceleration). During the transition, a fuel delay occurs due to the fuel wall flow.

In order to deal with this, adhesion of intake system, equilibrium amount of floating fuel
M0 is calculated using the engine load, engine speed and engine temperature as parameters, and the difference value (M0-M) between the equilibrium amount M0 and the predictive variable M of adhering intake system and floating fuel at that time and this difference The transient correction amount DM is obtained based on the correction coefficient DK indicating how much the value is reflected in the correction of the fuel injection amount, and the transient correction amount DM and the predictive variable M of the adhered and floating fuel are used for the fuel injection. The applicant of the present invention has previously proposed a method of adding the values synchronously and updating the prediction variable M with the added value (Japanese Patent Application No. 60-
No. 243605), according to the second prior application device, it is possible to accurately detect the adhesion of the intake system and the behavior of the floating fuel that cause the fuel delay.

The first prior application device for the α-N system and SPI, which is the same as the second prior application device, takes over completely, and this causes an error due to the measurement of the air amount and a fuel delay. It is now possible to clearly separate and understand the error.

Now, in the first prior application device, when an experiment was conducted, a phenomenon was observed in which the air-fuel ratio became temporarily leaner than the target air-fuel ratio at the initial stage of acceleration (becomes rich at the initial stage of deceleration). . Considering this, this is because the equilibrium amount M0 was initially calculated based on the value AA / N obtained by dividing the total flow passage area AA of the intake passage by the rotation speed N. Because, according to this AA / N value, there is no factor of response delay, so there is no problem as far as the response is concerned.
The value of / N is obtained because it is equivalent to the above equilibrium flow rate Qh (that is, the flow rate in the steady state), and is not the flow rate flowing through the throttle valve portion during the transition. In the α-N system and SPI, the amount of air that actually flows even though more air than the steady-state flow rate passes through the throttle valve portion by the amount of change ΔCM of the air inside the manifold that exists downstream of the throttle valve. If the equilibrium amount M0 is calculated with respect to the air amount that is estimated to be smaller than that, the transient correction amount DM will be insufficient at the initial stage of acceleration, and the air-fuel ratio will be diluted.

On the other hand, the second prior application device is of the L-Jetronic type and MPI (multipoint injection) type, and in this case, it is obtained by using a signal from a flap type or hot wire type air amount sensor. The basic pulse width Tp is used as the engine load to calculate the equilibrium amount M0. In this case, since the air amount sensor can detect the air amount flowing through the injection valve portion even during a transition, the problem as in the α-N system does not occur, but on the other hand, the air amount sensor has a response delay, Due to this response delay, the correction becomes insufficient at the initial stage of the transition.

After all, regardless of whether it is the α-N method and the SPI method or the L-Jetronic method and the MPI method, the fuel wall flow is generated downstream of the injection valve portion, so that the optimum air amount for the intake system downstream of the injection valve portion is balanced. It must be given as a parameter for the calculation of the quantity M0.

The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide an air-fuel ratio control device for calculating the equilibrium amount based on the amount of air flowing through the injection valve portion. .

(Means for Solving Problems) In the present invention, as shown in FIG. 1, a means 1 for calculating a basic fuel injection amount Tp according to the operating state of the engine, and an equilibrium adhesion amount of intake system fuel. Means 3 for calculating MFH based on at least the air amount Q _AINJ passing through the fuel injection valve 9, and this equilibrium adhesion amount MFH and the calculated value of the adhesion amount that changes with a first-order lag with respect to this equilibrium adhesion amount Means 4 for calculating the deviation (MFH-MF) and means 5 for calculating a quantity ratio KMF indicating how much the deviation is reflected in the correction of the fuel injection amount based on the engine speed, the engine load and the engine temperature. And a means 6 for calculating a VMF adhesion amount per unit cycle (per injection) (this adhesion amount is hereinafter referred to as "adhesion speed") based on the quantity ratio KMF and the deviation (MFH-MF). , The fuel injection amount is corrected by correcting the basic injection amount Tp with this adhesion speed VMF. And means 7 for, a means 8 for driving the fuel injection valve 9 at the injection signal corresponding to the injection amount, the deposition rate
A means (10) for adding the VMF and the previously calculated adhesion amount MF in synchronism with the fuel injection and updating the adhesion amount MF with the added value is provided.

_{Reference numeral} 2 is a means for calculating the air amount Q _AINJ passing through the injection valve portion, and parameters for calculating Q _AINJ include, for example, the engine speed N and the intake throttle valve opening α.

(Operation) For example, in the α-N system and SPI, when the equilibrium adhesion amount MFH is calculated based on the ratio AA / N of the total area of the intake passage and the rotational speed, the target air-fuel ratio is temporarily changed from the target air-fuel ratio at the initial stage of acceleration. It becomes lean (excessive at the beginning of deceleration).

When the intake throttle valve opening TVO increases stepwise for acceleration, AA / N is calculated from the intake throttle valve opening TVO. However, there is no response delay, but the reason why the value of AA / N is obtained is the steady-state air flow rate of the throttle valve section and not the actual flow rate of the throttle valve section during acceleration. α-
Since in the N type and SPI, it become possible to more than an amount corresponding equilibrium flow rate Q _H in the variation of DCM manifold air present in the throttle valve downstream air passes through the throttle valve unit, the air actually flowing amount If the equilibrium deposit amount MFH is calculated from the steady-state air amount, which is estimated to be smaller than that, the attachment velocity VMF will be insufficient at the initial stage of acceleration, and the air-fuel ratio will be diluted.

In this case, according to the injection valve air amount Q _AINJ calculated by the first prior application device, the waveform has a peak portion superimposed on the waveform of AA / N at the initial _stage of acceleration. The equilibrium deposit amount calculated from Q _{AINJ is} larger than the equilibrium deposit amount calculated from AA / N, which increases the deposition rate VMF. The area of the pointed portion corresponds to the manifold air change amount at the time of acceleration.
In this case, the transient correction amount KATHO can be calculated by calculating the equilibrium adhesion amount MFH for the air amount at this peak as well.
S is increased, and the leaning of the air-fuel ratio in the initial stage of acceleration is suppressed.

Similarly, in the case of the L-Jetronic system and MPI, the response delay occurring in the air amount sensor is corrected for the output of the air amount sensor, and the output of the air amount sensor after this response delay correction is linearly corrected. The cylinder air amount Qcy1 can be obtained from the delay, and the injection valve air amount Qainj can be obtained by time delay correction for the cylinder air amount Qcyl. The injection valve air amount Qainj obtained in this way is used as the equilibrium adhesion amount MFH.
L-Jetronic system and MP
Also in the case of I, the leaning of the air-fuel ratio in the initial stage of acceleration is suppressed.

α-N system and SPI, L-Jetronic system and M
Even with PI, since the fuel wall flow occurs downstream of the injection valve unit, the optimum air amount for the intake system downstream of the injection valve unit may be given as a parameter for calculating the equilibrium deposit amount MFH. The optimum air amount is the injection valve air amount.

An example will be described below.

(Embodiment) In FIG. 2, one fuel injection valve 24 covering all cylinders is provided in the intake passage 22 upstream of the intake throttle valve 21 (SPI), and the throttle valve opening α (also called TVO) rotates. The mechanical structure of the engine for predicting the intake air amount from the number N (α-N method) is shown.

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 32 built in the distributor 31, and the cooling water temperature Tw is measured by the water temperature sensor 33.
Also, the oxygen sensor 34 is 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. 8 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). FIG. 8 shows a subroutine for obtaining the temperature correction coefficient KTA), and FIG. 8 shows a subroutine for obtaining the variable (equilibrium deposition amount MFH) used in FIG. The numbers in the figure represent process numbers. In addition,
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.

By the way, in the case of the α-N system and SPI, the injection pulse width control involves two factors, an error associated with measurement of the intake air amount and an error associated with fuel delay, which complicatedly affects the control accuracy of the injection pulse width. As described above, the first prior application device (Japanese Patent Application No. Sho 61-18) is used as a solution.
1102), and with this device, even in the α-N system and SPI, it is possible to clearly separate and grasp the error due to the measurement of the air amount and the error due to the fuel delay. Has become.

To describe the measurement of the air amount again, when the intake air amount is being measured by the air amount sensor, the air amount that flows during a transition can also be measured, so the amount of air in the injection valve section in SPI is immediately upstream of the injection valve. The air amount detected by the sensor located on the side may be used after the response delay of the sensor is corrected.

However, in the α-N method, only the equilibrium flow rate of the throttle valve portion can be obtained from the throttle valve opening degree, and the amount of air passing through the throttle valve portion at the time of transition cannot be obtained. Since the steady-state air amount Qth of the throttle valve portion is given by the above equation (11), if the flow passage area A of the throttle valve portion is obtained from the throttle valve opening, Qth can be obtained. Is a steady-state value and is not the air amount at the time of transition. Therefore, if the value at the time of steady-state is used also at the time of transition, an error will occur in the air amount measurement at the time of transition.

To deal with this, the first prior application device calculates the injection valve air amount Q _AINJG as follows. This Q
The calculation part of _AINJG is the same in this application (3rd part)
(A shown in FIG. 3A and FIG. 3B). For convenience of description below, a symbol "-1" is added to the symbol, which means that the value is the value calculated last time.

Equilibrium amount of air in a steady flow rate of the throttle valve unit from the throttle valve opening TVO Q _H (%, cylinder per volume) is obtained (FIG. 3 (B)
Step 53, 55), the amount of air from this Q _H to the cylinder Q
_CYL (%, per cylinder volume) is _{calculated by} the formula Q _CYL = Q _H × K2 + Q _CYL-1 (1-K2) (6C) (first-order lag formula) (step 57 in Fig. 3 (B)). ). The air quantity Q _CYL to the cylinder matches the equilibrium air quantity Q _H in the steady _state.For example, even if the equilibrium air quantity Q _H increases stepwise during acceleration, the air quantity Q _CYL to the cylinder responds better. Therefore, the air amount Q _CYL to the cylinder is approximated by the first-order lag of the equilibrium air amount Q _H.

However, equation (6C) does not consider the air volume in the manifold that exists downstream of the throttle valve. Therefore, for example, when accelerating, Q
Injection valve air amount (equal to throttle valve air amount) Q than _CYL
AINJC (cc, per cylinder) increases (decreases conversely during deceleration). In other words, Q _AINJC can be obtained by the formula of Q _AINJC = Q _CYL × V _CYL + DCM (6B) (step 61 in Fig. 3 (B)).

Since Q _CYL is the value per cylinder, (6B)
In the formula, it is converted into a flow rate unit by multiplying the cylinder volume V _CYL (cc).

Here, manifold air variation DCM _{is, DCM = (Q CYL -Q CYL} -1) × KMANIO × Tref ...... (6E) However, KMANIO: Manifold coefficient Tref: can be given by the formula of the period of the Ref signal ( Step 5 in FIG. 3 (B)
9). The amount of change in cylinder air amount (Q _CYL -Q _CYL-1) is intended to take into account the degree of acceleration (or deceleration), the greater the degree of acceleration, the greater the value of (Q _CYL -Q _CYL-1) , Give a large value of DCM.

In addition, Q _AINJC is Q _AINJG = Q _AINJC × KTA (6A) However, it is converted into mass flow rate unit by the formula of KTA: intake air temperature correction coefficient ((step 63 in Fig. 3 (B)).

In this way, by _obtaining the injection valve air amount Q _AIHJG (mg, per cylinder), the injection valve portion can be set even in the α-N system and SPI without providing an air amount sensor and at the time of transition. The amount of air passing through can be accurately obtained.

In addition, the basic pulse width Tp (ms) is _calculated from the injection valve air amount Tp = Q _AINJG × TFBYA × K (5) where TFBYA is the target air-fuel ratio K is a constant based on the injection valve characteristics. , It should be possible to obtain the target air-fuel ratio.

On the other hand, not all the fuel injected from the injection valve is carried on the air flow and sucked into the cylinder, but a part of the injected fuel is
It adheres to the wall of the intake pipe downstream of the injection valve 21 and becomes a liquid to form a fuel wall flow. Even if such a fuel wall flow exists, if it is in a steady state, it will be deprived from the injected fuel as a fuel wall flow,
Since the amount of fuel flowing into the cylinder in the state of the fuel wall flow matches, no fuel delay occurs.

In this case, the fuel wall flow rate depends on the suction negative pressure, the rotation speed, and the temperature, and in the steady state, the fuel suction flow rate decreases as the suction negative pressure increases. For this reason, during acceleration in which the state of strong suction negative pressure changes to the state of atmospheric pressure, the injected fuel is deprived of an increase in the fuel wall flow, and the amount of fuel flowing into the cylinder is insufficient. The air-fuel ratio leans toward the lean side (the air-fuel ratio leans toward the rich side during deceleration). During the transition, a fuel delay occurs due to the fuel wall flow.

In order to deal with this, the second prior application device (Japanese Patent Application No. 60-
No. 243605), the correction amount for the fuel wall flow is calculated as follows. This calculation part is also inherited in the present application, and the basic idea is almost the same (shown in FIG. 4).

However, since the symbol and the name are different from those of the second prior application device, when the symbol and the name of the present application are repeated, the amount of the intake fuel adhered under the steady operation condition (the amount of the adhered is referred to as “equilibrium” MFH is calculated using the engine load, engine speed, and engine temperature as parameters (step 10 in FIG. 4).
1) Find the difference value (MFH-MF) between this equilibrium deposit amount MFH and the deposit amount MF that changes with a first-order lag with respect to this equilibrium deposit amount.

Here, the behavior of the equilibrium deposit amount MFH is briefly described.Since MFH is simply a map value, during acceleration that increases stepwise from the throttle valve opening, it adjusts to this throttle valve opening change.
MFH also increases stepwise, while the actual amount of adhesion responds with a first-order lag. The adhesion amount MF is obtained by approximating the behavior of the actual adhesion amount with a first-order lag. Therefore,
A deviation of (MFH-MF) occurs at the time of acceleration, and the fuel corresponding to this deviation is deprived by the increase in the fuel wall flow. Therefore, it is necessary to increase the fuel amount corresponding to this deviation.

However, in reality, if all of the above deviations are used as correction amounts, there will be too much fuel, so VMF calculated by the formula VMF = (MFH-MF) x KMF (7B) will be used as the wall flow correction amount. This is the case (step 103 in FIG. 4). The KMF in the equation (7B) is a value (quantity ratio) indicating how much the deviation (that is, MFH-MF) is reflected in the correction of the fuel injection amount. Further, since the injection is synchronized with the Ref signal, the VMF in the expression (7B) means the amount of adhesion per unit cycle (per injection), so the name "adhesion speed" is attached to the VMF.

On the other hand, the deposition speed VMF is synchronized with the fuel injection and the deposition amount MF is
And the attached amount MF is updated with the added value (step 153 in FIG. 12). Since the VMF calculated this time is given at the time of this injection, immediately after that injection (that is, at the time of the next injection)
MF is MFMF _-1Ref (MF just before this injection) this V
It has to be changed to the value with MF added.

Since it is necessary to consider the difference in fuel properties during deceleration, the value calculated by the formula KATHOS = VMF x GHF (7A) with the correction factor GHF (1.0 during acceleration) is the final wall flow. Correction amount (name is transient correction amount) KATHOS (Step 10 in FIG. 4)
6), this KATHOS is added to the basic injection pulse width Tp (step 151 in FIG. 12).

By obtaining the transient correction amount KATHOS in this manner, the behavior of the intake system fuel that causes the fuel delay can be accurately captured.

In the present application as well, by _{performing the} calculation of the injection valve air amount Q _AINJG in the α-N method and the SPI in this manner and performing the wall flow correction carried over from the second prior application device, an error accompanying the measurement of the air amount is performed. It is now possible to clearly separate and understand the error due to fuel delay.

Now, in the first prior application device, when an experiment was conducted, a phenomenon was observed in which the air-fuel ratio became temporarily leaner than the target air-fuel ratio at the initial stage of acceleration (becomes rich at the initial stage of deceleration). . Considering this, initially, the equilibrium adhesion amount MFH is
This is because the calculation is performed based on the value AA / N obtained by dividing the total flow area AA of the intake passage by the rotation speed N. Because this AA
According to the value of / N, there is no factor of response delay, so there is no problem as far as the response is concerned, but as mentioned above, the value of AA / N is equivalent to the equilibrium flow rate Q _H above. This is because the flow rate (that is, the flow rate in the steady state) is not the flow rate flowing through the throttle valve portion during the transition. In the α-N system and SPI, the amount of air that actually flows when more air than the equilibrium flow rate Q _H passes through the throttle valve portion by the amount of change DCM of the air inside the manifold that exists downstream of the throttle valve. If the equilibrium adhesion amount MFH is calculated with respect to the air amount estimated to be smaller than that, the transient correction amount KATHOS will be insufficient at the initial stage of acceleration, and the air-fuel ratio will be diluted.

To deal with this, the control unit 35 calculates the equilibrium adhesion amount MFH based on the air amount Q _AINJ passing through the injection valve portion (step 101 in FIG. 4).

Here, the above-mentioned second prior application device (Japanese Patent Application No. 60-243605) is used.
No.), the conventional basic pulse width Tp, the engine speed N, and the cooling water temperature Tw in the L-Jetronic system are used as parameters to obtain a combination of a search of a three-dimensional map and an interpolation calculation of a linear approximation interpolation approximation. However, in the present application, L-
Only Q _AINJ is used instead of the conventional basic pulse width Tp in the _JETRONIC method, and the person who obtained it does not change.

Specifically, as shown in FIG. 8, different 6 preset values are set within the range of the temperature change width that the cooling water temperature Tw can actually take.
Q _AINJ is _set to N for each individual reference temperature Tw _{0 to} Tw ₅ (Tw ₀ ＞ ... ＞ Tw ₅ ).
Is used as a parameter, and six pieces of adhesion amount data for providing the equilibrium adhesion amount MFHTwn at the reference temperature Twn (n = 0 to 5) are prepared by actual measurement. Then, the upper and lower reference temperature Twn of actual water temperature Tw, the equilibrium adhesion amount MFHTwn, the MFHTwn ₊₁ used in Twn _+1, Tw, Twn, is the ultimately determine the MFH at Twn ₊₁ by interpolation calculation (step 132 ~ 143).

Further, although a high accuracy can be obtained by the method using the three-dimensional map and the interpolation calculation, there are cases where it is desired to increase the calculation speed even if the accuracy is moderate, and this case is shown by the following expression (7F).

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

Next, the operation of this embodiment at the time of transition will be described with reference to FIG. 11, which is for acceleration.

In the figure, AA / N (the ratio of the total area of the intake passage to the number of revolutions,
Shown by a solid line. ), The MFH is calculated to be leaner than the target air-fuel ratio at the beginning of acceleration (see the solid line in the lower row).

When the intake throttle opening TVO increases stepwise for acceleration, AA / N is calculated from the intake throttle opening TVO,
The waveform immediately increases in steps and there is no response delay to changes in TVO, but the value of AA / N is the steady-state air flow rate of the throttle valve, and the throttle valve during acceleration. This is because the flow rate does not actually flow through the section. In the α-N system and SPI, since more air than the equilibrium flow rate Q _H passes through the throttle valve portion by the change amount DCM of the air in the manifold existing downstream of the throttle valve, it actually flows. If the equilibrium adhesion amount MFH is calculated from the steady-state air amount that is estimated to be less than the air amount, the transient correction amount KATHOS will be insufficient at the initial stage of acceleration, and the air-fuel ratio will be diluted.

In this case, the first prior application device (Japanese Patent Application No. 61-181102).
According to the injection valve air amount Q _AINJ calculated by
As shown in the figure, the waveform of AA / N is a waveform in which a peak portion is superimposed in the initial stage of acceleration (see the middle dashed line).
The equilibrium adhesion amount MFH calculated from Q _{AINJ is} larger than the equilibrium adhesion amount calculated from AA / N, and the transient correction amount KATHOS is also increased accordingly. In the middle part of the figure, the area of the peak portion surrounded by the one-dotted dashed line QAINJ and the solid line AA / N corresponds to the manifold air change amount during acceleration, and in the α-N system and SPI, this The transient correction amount KATHOS is increased and the leaning of the air-fuel ratio at the initial stage of acceleration is suppressed by estimating the equilibrium deposition amount MFH for the air amount in the peak portion as well.

The figure also shows the conventional L-Jetronic system and MI.
Based on the change in the conventional basic pulse width Tp used in P (see the broken line in the middle row) and the Tp, the equilibrium deposition amount MF
As shown in the waveform when H is calculated (see the broken line in the lower part), Tp shows the air amount of the throttle valve well because Tp is obtained from the air amount sensor, but the response that occurs in the air amount sensor The waveform has a peak that lags behind Q _{AINJ in} time from the delay, and rather the degree of _leaning of the air-fuel ratio in the early stage of acceleration is rather worse depending on AA / N.

Next, as an overview of the entire system, the routine of FIG. 3 has a basic pulse width Tp, and FIG. 12 shows the final injection pulse width Ti.
Is a part for performing the calculation of.

Here, in the α-N system and SPI, as described above, the air amount Q _CYL flowing into the cylinder and the air amount Q _AINJ passing through the injection valve portion do not match at the transition time, and the air is injected from the injection valve. These two points are taken into consideration in this system, because there is a delay in the supply of fuel to the cylinder. However, these are calculated independently of each other (Q _AINJ is calculated for the air amount and the transient correction amount KATHOS is calculated for the fuel delay.) This simplifies the concept and the target of control error is the measurement of the air amount. This is to clarify whether it is an error or a fuel delay. As a result, the accuracy at the time of setting is remarkably improved, and further, it becomes a factor of lowering the accuracy due to changes over time and differences in fuel properties after the setting. Therefore, a 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 (step 151 in FIG. 12). The sum of Te and Te is Ti (Te = Te + Ts) with the invalid pulse width Ts (step 69, step 151 in FIG. 12).

Te ＝ (Tp × KBLRC ＋ KATHOS × KBTLRC) × LAMBDA ……
(4) However, Tp: basic pulse width KATHOS: transient correction amount LAMBDA: air-fuel ratio correction coefficient KBLRC: steady state learning correction coefficient KBTLRC: transient 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) However, 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 is _{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), Group (6A)
~ (6F) required.

Q _AINJG = Q _AINJC × KTA …… (6A) Q _AINJC = Q _CYL × V _CYL + DCM …… (6B) Q _CYL = Q _H × K2 + Q _CYL-1 × (1-K2) …… (6C) Q _H ＝ Q _H0 x KFLAT ...... (6D) DCM = (Q _CYL -Q _CYL-1 ) x KMANIO x Tref ...... (6E) KTA = KTA0 x 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 air 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 to per cylinder, per cylinder volume, etc.), but basically,
_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 as a weighted average value having Q _H and Q _CYL-1 as variables and K2 as a weight as a constant for smoothing K2 (steps 55 to 57 in FIG. 3 (B)).

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 intake 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 / V _CYL …… (6G) AA ＝ ATVO ＋ AI ＋ AAC …… (6H) However, AADNV: Channel area / (rotation speed × cylinder volume) (cm ² / rpm ・ cc) AA: Total channel area (Cm ² ) ATVO: Flow area of throttle valve (cm ² ) AI: Flow area of SV26 (cm ² ) AAC: Flow area of SV27 (cm ² ).

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.

In actual control, a value AA / N obtained by dividing the total flow passage area AA by the rotation speed N (corresponding to the AA / Tref portion 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 flow 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
The AQ _CYL is also searched using the intake air temperatures T _A and Q _CYL 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. Note that FIG. 8 is a subroutine for calculating a variable (MFH) used in this routine with FIG. 4 as a main routine.

In this example, it is calculated based on the deviation between the equilibrium adhesion amount MFH of the intake system fuel and the calculated adhering amount that changes with a first-order lag with respect to this equilibrium adhesion amount. This can be expressed mathematically as the following formula group (7A)
~ (7E) will be given.

KATHOS = VMF × GHF …… (7A) VMF = (MFH−MF) × KMF …… (7B) MF = MF _-1Ref ＋ VMF …… (7C) KMF = (KMFAT + KMFVMF) × KMFN × KMFDBT …… (7D) GHF ＝ GHFQ _CYL × GHFFBYA (7E) However, KATHOS: Transient correction amount (μs) VMF: Adhesion speed (μs / injection) MFH: Equilibrium adhesion amount (μs) MF: Adhesion amount (μs) at this time calculation KAFAT: Basic volume ratio (%) KMFVMF: Adhesion speed correction rate of volume ratio (%) KMFN: Rotational correction rate of volume ratio (%) KMFDBT: Boost correction rate of volume ratio (%) GHT: Correction rate (%) GHFQ _CYL : Deceleration correction factor (%) GHFFBYA: Air-fuel ratio correction factor (%).

The routine shown in FIG. 8 is a characteristic part of the present invention, and the contents thereof have been described above. Therefore, although the description of the MFH is duplicated, it will be described as it is.

That is, the deposition speed VMF means the deposition amount per unit cycle (per injection), and the deviation (MFH−) between the equilibrium deposition amount MFH and the calculated value of the deposition amount that changes with a first-order lag with respect to this equilibrium deposition amount. MF) is multiplied by a coefficient KMF indicating how close the calculated value of the adhered amount approaches per unit cycle (step 103).

Here, the equilibrium deposit amount MFH is the amount of air Q passing through the injection valve section.
_{Based on AINJ} , machine speed N, and cooling water temperature Tw, it is calculated by a combination of search of a three-dimensional map and interpolation calculation near a straight line. That is, six different reference temperatures Tw set in advance within the range of the temperature change width that the cooling water temperature Tw can actually take.
_{0 ~Tw 5 (Tw 0> ...} > Tw 5) the equilibrium adhesion amount at the reference temperature Twn (n = 0~5) and Q _AINJ and N as a parameter for each MFH
Data of six equilibrium adhesion amounts for the purpose of giving Twn are prepared by actual measurement. Then, reference temperatures Twn and Twn above and below the actual water temperature Tw
Equilibrium adhesion amount MFHTwn in _+1, using MFHTwn _+1, Tw, Twn,
The MFH is finally obtained by interpolation calculation using Twn _{+ 1} (steps 101, 132 to 143).

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).

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. 9 and 10
The figure is a diagram for explaining the contents of MFHQn and MFHNn.

When Tw> Tw ₀ and when Tw <Twn, interpolation calculation cannot be performed, so MFH = MFHTW _{0 is} set (steps 132, 138, 137, 138). Also, during fuel cut, MFH = FCM
FH (constant value) is set (steps 131 and 144).

On the other hand, the adhesion amount MF calculated this time is a value obtained by adding the adhesion amount VMF obtained immediately before the current injection to the adhesion amount MF _-1Ref calculated immediately after the previous injection (step 153 in FIG. 12).

Next, for the volume ratio KMF, in this example, the basic value KMFAT is obtained by map search using AADNV, Tw as a parameter, and
Correction is performed based on the high-pass value DBOST of MF, N and boost pressure change amount. That is, the correction coefficients for the basic value KAFAT are three coefficients KMFVMF, KMFN, KMFDBT, which are introduced so that the air-fuel ratio has a flat characteristic in the initial stage of the transition. In other words, a slight undercorrection is seen in slow acceleration, and an error occurs due to the difference in rotational speed,
In addition, a slight deviation occurs when an experiment is performed such as an error occurs at the initial stage of the transient, for which the boost correction factor KMFDFT is used, for the rotation correction factor KMFN, and for KMFVMF. Is to be solved individually by.

Regarding the three coefficients KMFVMF, KMFN, KMFDTB, another application proposed at the same time as the present application (Japanese Patent Application No. 61-183056).
As it will be briefly described, KMFDBT is obtained by table search with high-pass value DBOST as a parameter, KMFN is obtained by table search with rotation speed N as a parameter, and KMFVMF is obtained by table search with VMF _-1 as a parameter.

In this way, the volume ratio KMF is
It is calculated based on NV, Tw as the engine temperature, the engine speed N, and also based on the high-pass value DBOST and the adhesion speed (VMF _-1 ).

The high-pass value DBOST is obtained by the following equations (7G) to (7I), and the content thereof is a value that integrates the minute change amount of the boost pressure BOOST and gradually attenuates in synchronization with the Ref signal.

(1) When set (first time) DSOST = DSOST _-1 + (BOOST-BOOSTO) ...... (7G) (2) When attenuated (DBOST ≥ 0) (2nd time or later) DBOST = DBOST _-1 × TGEN ...... (7H ) (3) When damping (DBOST <0) (2nd time or later) DBOST = DBOST _-1 × TGENG (7I) where BOOST: Boost pressure BOOSTO: Last boost pressure 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 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 adhered amount during deceleration, and conversely, a small value should be given as the correction coefficient (GHFQ _CYL ). That is, during acceleration (VM
If F is positive), no correction is made (GHFQ _CYL = 1.0),
When decelerating (when VMF is negative), a value of 1 or less is adopted. The target air-fuel ratio TFBYA is also corrected according to the target air-fuel ratio TFBYA, and the deceleration correction ratio GHFQ _CYL is obtained by a table search using Q _CYL , and the air-fuel ratio correction ratio GHFFBYA is obtained by 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 ₁・ ER …… (8C) D = K _D・ (ER-ER _-1 ) …… (8D) However, K _P : proportional gain K _I : integral gain K _D : derivative 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 (n + 1) times before (where n is the number of cylinders) and the Ref signal is Indicates the sensor output Ip when input. 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, 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. As a result, the learning correction will be separated and performed independently. That is, the learning correction coefficient KBLRC in the steady state is the air-fuel ratio correction coefficient LAMBDA
In this calculation routine, the learning correction coefficient KBTLRC during transient is calculated in the calculation routine for the transient correction amount KATHOS (steps 119 and 120 in FIG. 5, steps 107 to 11 in FIG. 4).
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 the LAMBDA and KBTLRC is the LAMBDA and the actual value. It is calculated based on the air-fuel ratio AFBYA and the deviation B of the target air-fuel ratio TFBYA (steps 119, 120, 107).
~ 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).

In the embodiment, only the α-N system and the SPI have been described, but it goes without saying that it is also applicable to the L-Jetronic system and the MPI. In the case of the L-Jetronics system and MPI, since the air amount sensor has a response delay as described above, the response delay is corrected for the output of the air amount sensor, and the air amount sensor after this response delay correction is performed. Since the cylinder air amount Qcy1 can be obtained with a first-order lag with respect to the output of, and the injection valve air amount Qainj can be obtained by time delay correction for this cylinder air amount Qcy1, the injection valve air amount thus obtained is It is used in the calculation of MFH.

(Effects of the Invention) As described above, in the present invention, the means for calculating the basic fuel injection amount according to the operating state of the engine, and the equilibrium adhesion amount of the intake system fuel at least the air passing through the fuel injection valve portion Means for calculating based on the amount, means for calculating a deviation between the equilibrium adhesion amount and a calculated value of the adhesion amount that changes with a first-order lag with respect to the equilibrium adhesion amount, and the deviation for correcting the fuel injection amount. Amount ratio that shows how much is reflected, engine speed,
Means for calculating based on the engine load and engine temperature, means for calculating the adhering speed based on the amount ratio and the deviation, and calculating the fuel injection amount by correcting the basic injection amount based on the adhering speed Means, a means for driving the fuel injection valve with an injection signal according to the injection amount, the adhesion speed and the previously calculated adhesion amount are added in synchronism with the fuel injection, and the addition amount is the added value. And means for updating
Even in the α-N system and the SPI or L-Jetronic system and the MPI, it is possible to eliminate the insufficient correction of the fuel wall flow at the initial transition and obtain a flat air-fuel ratio characteristic.

[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 an .alpha.-N system and SIP engine, and FIGS. 3 to 8 and 12 are shown in FIG. FIG. 9 is a flowchart for explaining the operation contents executed in the control unit, FIG.
FIG. 10 is a diagram for explaining the contents of the coefficients MFHQn, MFHNn in this embodiment, and FIG. 11 is a waveform diagram for explaining the operation of this embodiment. 1 ... Basic injection amount calculation means, 2 ... Injection valve air amount calculation means, 3 ... Equilibrium adhesion amount calculation means, 4 ... Deviation calculation means, 5 ... Quantity ratio calculation means, 6 ... Adhesion speed calculation Means, 7 ... Fuel injection amount calculation means, 8 ... Driving means, 9 ...
... Fuel injection valve, 10 ... Adhesion amount calculation 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 front page (72) Inventor Masaaki Uchida 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Toshio Takahata 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. ( 72) Inventor Hiromasa Kubo 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. A means for calculating a basic fuel injection amount according to an operating state of an engine, and a means for calculating an equilibrium adhesion amount of intake system fuel based on at least an air amount passing through a fuel injection valve portion, A means for calculating a deviation between the equilibrium adhesion amount and a calculated value of the adhesion amount that changes by a first-order lag with respect to the equilibrium adhesion amount, and a quantity ratio indicating how much the deviation is reflected in the correction of the fuel injection amount. , Means for calculating based on the engine speed, engine load and engine temperature, means for calculating the deposition speed based on the quantity ratio and the deviation, and fuel for correcting the basic injection amount with this deposition speed. Means for calculating an injection amount, means for driving the fuel injection valve with an injection signal according to the injection amount, the adhesion speed and the calculated adhesion amount are added in synchronization with fuel injection, and Means to update the adhesion amount with the added value And an air-fuel ratio control device for an internal combustion engine.