JPS62101855A - Fuel-injection control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the accuracy of air-fuel ratio control through obtaining the transient correction quantity with a high accuracy by computing a basic injection quantity by way of calculating a transient correction quantity based on the difference value between the equilibrium quantity of the sticking and floating fuel in an intake system and the prediction parameter of said equilibrium quantity. CONSTITUTION:Based on the output of an operating condition detecting means (a), the equilibrium quantity of the sticking and floating fuel in an intake system at the time of a steady state is computed by an equilibrium quantity computing means (c), and then, the difference value between the equilibrium quantity obtained and the prediction parameter of the sticking and floating fuel quantity in an intake system at the point of time is computed by a difference value computing means (d). In addition, a new prediction parameter is computed by a prediction parameter computing means (f) according to a transient correction quantity, which is calculated through a transient correction quantity computing means (e) on the basis of both the above difference values and the correction factors set up in advance according to the operating conditions of an engine, and also to the prediction parameters for the above. And further, based on a basic injection quantity computed by a basic injection quantity computing means (b), and the above transient correction quantity, a fuel injection quantity is computed through a fuel injection quantity computing means (g) so that a fuel supply means (h) is controlled according to the fuel injection quantity obtained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a fuel injection system for an internal combustion engine in which the optimum fuel injection amount is determined by correcting the basic injection amount according to the operating state of the engine during a transient period. This invention relates to an injection control device.

(Prior art) In general, the deviation of the air-fuel ratio from the target air-fuel ratio during acceleration or deceleration of the engine is mainly caused by changes in the amount of adhering fuel and floating fuel adhering to the intake manifold and intake ports of the intake system. The amount of adhering and floating fuel varies greatly depending on the operating condition of the engine. Further, the amount of adhering and floating fuel does not change stepwise in response to changes in operating conditions, but changes with a certain delay, and the time constant of this delay is also not constant. Furthermore, changes in the amount of adhering and floating fuel vary not only depending on changes in the operating conditions but also depending on the magnitude of the difference between the amount at that point in time and the amount in equilibrium state B (steady state B).

Therefore, as a conventional example, changes in adhesion and floating fuel are approximately determined from changes in intake pipe pressure and accelerator opening during a transient period, and the amount of fuel injection is increased during acceleration and decreased during deceleration, and when the engine is warmed up. In JP-A-58-144632 and JP-A-58-144634, the correction coefficients for acceleration increase and deceleration decrease are further corrected using a correction factor according to the cooling water temperature.
No. 58-144636, No. 58-144637, and No. 58-150033, each publication).

(Problem to be solved by this invention) However,
In such conventional fuel injection control devices, adhesion in the intake system and changes in the amount of floating fuel are determined not only by changes in the pressure inside the intake pipe, but also by the absolute value of the pressure inside the intake pipe. It also depends on engine speed etc. Also,
The correction magnification is not constant with respect to the cooling water temperature, but changes depending on the engine rotation speed and the like. Therefore, although the conventional control device can control the air-fuel ratio with relatively high accuracy under specific acceleration/deceleration conditions, it has not been possible to control the air-fuel ratio with high accuracy under all acceleration/deceleration conditions. As a result, there was a problem in that harmful exhaust gases could not be sufficiently reduced, especially when the engine was cold, and drivability could not be sufficiently improved.

In addition, in the conventional example, correction is performed separately for increasing acceleration and decreasing deceleration, but in most cases, such one type of correction does not provide sufficient control accuracy, so correction during idling may be stopped, or Furthermore, control devices have been proposed that determine the injection amount by performing a number of corrections such as starting and post-start increase correction, post-idling increase correction, and fuel cut correction. However, in such a control device, not only is the control configuration for determining the injection amount complicated, but also the matching of correction coefficients takes time, resulting in a problem that highly accurate control cannot be performed.

(Means for Solving the Problems) The present invention has been made for the purpose of solving these problems, and the overall configuration diagram thereof is shown in FIG. 1. That is, the present invention has an operating state detecting means a for detecting the operating state of the engine, and a basic injection amount calculating means for calculating the basic injection amount based on the operating state of the engine. Balance amount calculation means C for calculating the balance amount of adhesion and floating fuel in the intake system
and a difference value calculation means d that calculates the difference between the equilibrium amount of adhesion and floating fuel calculated by the equilibrium amount calculation means C and the predictive variable of the amount of adhesion and floating fuel in the intake system at that time, and a difference value calculation means d. means d
A transient correction amount calculation means e that calculates a transient correction amount based on the difference value calculated in and a correction coefficient predetermined according to the operating state of the engine, and a transient correction amount calculated by the transient correction amount calculation means e. A predictive variable calculating means f newly calculates the predictive variable based on the predictive variable of the adhesion and floating fuel, and a basic injection amount calculating means that calculates the basic injection amount already calculated and the transient correction amount calculating means e that calculates the transient correction amount. The fuel injection amount calculation means g calculates the fuel injection amount based on the correction amount and outputs an injection signal, and the fuel supply means g supplies fuel to the engine based on the injection signal.

(Function) In the present invention having such a configuration, a highly accurate transient correction amount can be obtained with a simple control configuration during engine transients, so the accuracy of air-fuel ratio control can be greatly improved. can.

As a result, it is possible to improve drivability, reduce the amount of harmful exhaust gases, increase output, and improve fuel efficiency, and the matching time can be shortened by simplifying the control configuration.

(Example) Embodiments of the present invention will be described below based on the drawings.

2 to 10 are diagrams showing a first embodiment of the present invention.

First, to explain the configuration, in FIG. 2, 21 is an internal combustion engine, and intake air is supplied to each cylinder of the engine 21 through an intake pipe 2.
2. A fuel injection valve (fuel supply means) 23 that injects fuel to each cylinder is attached to the intake pipe 22, and the flow rate of intake air supplied to the engine 21 is controlled by a throttle provided at the gathering part of the intake pipe 22. Controlled by valve 24. The throttle valve 24 is linked with the accelerator pedal of the vehicle, and the valve opening Cv of the throttle valve 24 is detected by a throttle opening sensor 25. The flow rate of intake air (hereinafter referred to as intake air amount) Qa is detected by the air flow sensor 26. Further, the rotation speed N of the engine 21 is detected by a crank angle sensor 27, and the crank angle sensor 27 is connected to a signal disc plate 27a attached to the crankshaft of the engine 21 and provided with a protrusion on the outer periphery, and It has a magnetic deck 27b for detecting protrusions. Further, the temperature Tw of the cooling water flowing through the water jacket is detected by a water temperature sensor 28. The throttle opening sensor 25, air flow sensor 26, crank angle sensor 27, and water temperature sensor 28
constitutes an operating state detection means as a whole, and each of these signals is input to the control unit 29.

The control unit 29 has functions as a basic injection amount calculation means, an equilibrium amount calculation means, a difference value calculation means, a transient correction amount calculation means, and a fuel injection amount calculation means.
It is composed of U30, ROM31, RAM32 and I10 port 33. The CPU 30 follows the program written in the ROM 31! 10 port 33 to import necessary external data, and RA
Arithmetic processing is performed while exchanging data with the M32, and the processed data is sent to the I10 boat 33 as necessary.
Output to.

The ROM 31 stores a program for controlling the CPU 30, and the RAM 32 is made up of, for example, a non-volatile memory and stores data used in calculations in the form of a map or the like, and retains the stored contents even after the engine 21 is stopped. . The I10 boat 33 has the throttle opening sensor 25.
, the air flow rate sensor 26, the crank angle sensor 27, and the water temperature sensor 28, as well as signals from an air-fuel ratio sensor, an ignition switch, etc. (not shown), and the analog input signals are converted into digital signals. In addition, the injection signal Si is sent from the I10 port 33 to the fuel injection valve 2.
3 is output.

Next, the effect will be explained.

Generally, the air-fuel ratio of an internal combustion engine using a fuel injection valve is controlled by changing the duty value of an injection signal output to the fuel injection valve to adjust the fuel injection amount.

In this embodiment, the duty value of this injection signal St is calculated by the control unit 29.

This operation will be explained below based on the flowcharts shown in FIGS. 3 and 4. Note that these flows are executed, for example, in synchronization with engine rotation.

In the flowchart showing the basic injection amount calculation routine in FIG. 3, the basic injection amount Tp and the transient correction amount DM described later are
and seek.

First, the basic injection amount 'rp is calculated using Pl according to the following equation (2).

However, K: constant Next, at P2, the equilibrium amount (steady amount) Mφ of adhesion and floating fuel in the intake system under steady conditions is calculated based on the engine rotation speed N, the basic injection amount Tp, and the cooling water temperature TV. Specifically, it is determined from the flow chart showing the balance amount calculation routine in FIG. That is, each cooling water temperature T
Rotation speed N and basic injection ff for w O-T w 4
The equilibrium quantities MφO to Mφ4 obtained as experimental values using 1Tp as a parameter are allocated in the RAM 32, and are looked up from the table map according to the cooling water temperature TwOxTw4 and calculated by linear approximation interpolation. This is to find Mφ. For example, when the cooling water temperature TV is equal to or higher than the cooling water temperature TWI due to pH, the equilibrium i1 according to the engine speed N and the basic injection amount Tp is calculated from the table map Mφφ' corresponding to the cooling water temperature TWO at P1□.
Look-amp Mφφ, and in PI□ coolant temperature Twl
The balance amount Mφ1 corresponding to the engine speed N and the basic injection amount TI is looked up from the table map Mφ1' corresponding to the table map Mφ1′ (see FIG. 7). Next, at PI3, the equilibrium amount M
φ is determined by linear approximation interpolation calculation formula from cooling water temperature TW to 2≦
When Tw≦Twl, 7w3≦'l' w <'l' When w 2, 'I' When w < Tw 3, the equilibrium MMφ is determined.

Next, returning to the flowchart of FIG. 3 again, the correction coefficient DK is calculated using P. Here, the correction coefficient DK is a coefficient that indicates how much to compensate for adhesion in the intake system and insufficient or excessive amount of floating fuel by correcting the current fuel injection amount, and this correction coefficient DK is constant. Although it may be set as a value, in order to perform more accurate correction, the engine rotation speed N
, is determined from experimental values based on the basic injection amount 'rp and the transient correction amount DM, which will be described later. Specifically, the correction coefficient DK is calculated according to the flow chart showing the correction coefficient calculation routine in FIG.
Calculate. First, in P3+, the cooling water temperature correction coefficient DKT
As shown in FIG. 8, w is looked up from the table map DKTw' obtained as experimental values using the cooling water temperature 7'w and the target correction amount DM as parameters, and the rotational speed correction coefficient DKN, As shown in FIG. 9, look-amplification is performed from a table map DKN' obtained as experimental values using engine speed N and basic injection ftTp as parameters. Then, in P'13, the correction coefficient DK is calculated by the following formula ■
Calculate according to

DK = DKTw

DM=DK (Mφ−M) ・・・・・・■Here, M is a predictive variable that is calculated separately as described later,
This variable M has a meaning as a predicted value of the amount of adhering floating fuel in the intake system at that time. Therefore, Mφ−
M means the amount of adhesion or floating fuel that is insufficient or in excess compared to that in the equilibrium state.

Next, in the flow chart showing the fuel injection amount calculation routine of FIG. 4, the actual fuel injection amount Tl and the variable M are calculated.

First, at Pd2, the fuel injection amount TPF is calculated according to the following formula (■): TPF=TP+DM ......■ Then, P
In step 4□, calculate the actual injection amount TI according to the following equation.

Tr=TPFXαXC0EF+Ts ・・・・・・■
Here, α is the air-fuel ratio feedback correction coefficient that is increased or decreased depending on the output of the oxygen sensor, and C0EF is the correction to give the air-fuel ratio that produces the maximum output when the engine is fully opened, the increase correction at startup, and the increase at low water temperature. This is a correction coefficient for performing correction, and TS is a voltage correction bone, which is a correction coefficient that has been conventionally used.

The actual fuel injection amount TI obtained in this way is P4, and I
The voltage pulse width is stored in the output register of the 10 boat 33 as a voltage pulse width having a predetermined duty value, and is output from the fuel injection valve 23 as an injection signal Si.

As a result, a predetermined amount of fuel is injected from the fuel injection valve 23. Next, at Pd2, the variable M is calculated according to the following equation (2), and the routine ends.

M=Old DM+DM ・・・・・・■Transient correction amount D
Since M is an amount corresponding to the amount of change in adhesion and floating fuel in the intake system, M is a variable that means the amount of adhesion and floating fuel at the current moment.
has been corrected by the transient correction amount DM, and the variable M
is used to calculate the next transient correction amount DM as the predicted value M+DM to be used next.

In this embodiment, the rotational speed N, the basic injection amount Tp, and the cooling water temperature TW were used to find the equilibrium amount Mφ and the correction coefficient DK, but for example, the basic injection amount 'r
Instead of p, intake air amount Qa, intake pipe internal pressure, throttle valve opening CV, etc. may be used, or cooling water temperature T
Instead of W, the intake pipe internal temperature or the like may be used.

Next, Fig. 10 shows the conditions during acceleration (see Fig. 10 (A)), deceleration (see Fig. 10 (B)), and gear change during acceleration (see Fig. 10 (C)). Mφ, M,
The waveforms of Mφ-M% DKN% DKTW, DK%DM, Tp, and TPF are shown. As is clear from this figure, highly accurate transient correction [DM
is obtained. Therefore, the optimum fuel injection 11TPF can be ensured, and the optimum air-fuel ratio can be achieved.

Further, even when changing gears, it is possible to perform accurate and continuous correction without performing control such as switching between acceleration increase and deceleration decrease. As a result, it is possible to improve drivability, reduce harmful exhaust gases, increase output, and improve fuel efficiency.

Next, FIG. 11 and FIG. 12 are diagrams showing a second embodiment of the present invention.

This example is an example in which the control of the transient correction amount DM described above is similarly applied to fuel cut and temporary recovery correction. .

Figure 11 shows the basic injection amount 'rp and transient correction i1 in Figure 3.
4 is a flowchart showing a routine similar to the injection amount calculation routine for calculating DM, and differs from the routine shown in FIG. 3 in that step t and step psa are added.

After calculating the basic injection amount 'rp with Pal, it is determined whether or not fuel is being cut using psz, and if the fuel is not being cut, the process proceeds to PS4. During fuel cut, PS3 sets the balance amount Mφ to a predetermined value MFC, for example, zero or a value much smaller than the normal balance amount Mφ, pss sets the correction coefficient DK, and psi sets the transient correction amount DM. , respectively, and the routine ends. Note that if the fuel is not being cut, the routine ends after going through P54 to PS&, as in the case described above.

Normally, the air-fuel ratio shifts toward lean during fuel cut and recovery. This is because floating fuel adhering to the intake system is sucked into the engine 21 during fuel cut, and during recovery, the amount of fuel injected to match the intake air amount Qa is insufficient to compensate for the fuel adhering to the intake system again. However, in this embodiment, as shown in FIG. 12, the equilibrium amount Mφ is set to zero, for example, during fuel cut, so the variable M gradually decreases and gradually approaches the equilibrium amount Mφ. Therefore, when the equilibrium amount Mφ reaches a predetermined value at the time of recovery, Mφ−M
ho, and an appropriate increase correction is made. Note that when fuel cut and recovery are performed when the fuel cut time is short, that is, when Mφ-M does not take a large value, Mφ-M at the time of recovery does not take a very large value, and the transient correction amount DM is also small. However, in this case, the adhesion in the intake system and the amount of floating fuel have not decreased so much, so it is possible to perform an optimal correction that takes this into account.

Further, the increase correction at the time of starting the engine can be performed in the same way. In this case, when the ignition/notion switch is turned on, the variable M should be set to zero in a separately prepared initialization routine to appropriately make an increase correction according to the operating condition at the time of starting cranking. I can do it.

Furthermore, appropriate correction can be made in the same way even after the complete explosion. However, in this case, during a cold start, some of the fuel adheres to the cylinder wall and is discharged without being burned, so it is preferable to increase the amount by that amount.

As can be seen from this, in the present invention, various corrections that have conventionally been made can be reduced to a minimum, and can be controlled with high precision. In other words, it is possible to simplify the start-up increase correction and start-up increase correction (only correct for unburned emissions), and eliminate the increase correction after idling, and it is also possible to perform the correction after fuel cut separately. There is no need to perform correction separately for acceleration and deceleration.

Next, FIGS. 13 and 14 are diagrams showing a third embodiment of the present invention.

This embodiment is an example in which not only learning control during steady operation but also learning control during transient correction is performed.

FIG. 13 is a flowchart showing the feedback routine of learning control, and P61 to P'+4 indicate each step.

First, Pal determines whether the feedback condition is satisfied based on the operating conditions, and if it is satisfied, P
Proceed to bz, and if not established, proceed to Pb0. Pb
At Pb0, the feed hack correction coefficient α is obtained by referring to the steady learning result from the address of the RAM 32 stored according to the operating conditions, and at Pb0, the integrated value Σα of α and the integrated number n of α are calculated.
Finish this routine by setting and as zero. Next, when the feedback condition is satisfied, the output 02 of the oxygen sensor is compared with the comparison reference value S/L in P6□, and V s <
When the air-fuel ratio is S/L, it is determined that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and an increase correction amount is calculated by PI control in P6. V
When s>S/L, it is determined that the air-fuel ratio is less than the stoichiometric air-fuel ratio, and a reduction correction amount is calculated by PI control in p66. Next, P6? The increase/decrease correction amount P to the old feedback correction coefficient is
+I is added to obtain a new feedback correction coefficient α, and the process proceeds to PhB. On the PCB, the absolute value I DM l of the transient correction amount DM is compared with the comparison reference value LGDM, and l DM
When l < LGDM, it is determined that it is not a transient state (it is a steady state state), and the integrated value of α (Σα=Σα+
α) and the cumulative number n (n=n+1) of α are calculated and the process proceeds to P70. When l DM l > LGDM, it is judged that it is in a transient state, and the number of integrations n is compared with the number of learning judgments LGn at PH1, and when n>LGn, the average value of α is calculated cx at p7g.
Calculate (cx=Σα/n) and proceed to P, 3.

In pti, the average feed bank correction coefficient 7 is used to rewrite the addresses of the RAM 32 corresponding to the transient learning coefficients GMφ1 to GMφn. Transient learning coefficients GMφ1 to GMφn are respectively assigned to the addresses of the RAM 32 according to the cooling water temperature Tw, and the contents of the addresses are rewritten according to the cooling water temperature Tw. That is, the average feedback correction coefficient 7 and the value in the RAM 32 corresponding to the cooling water temperature Tw may be used, and the difference between them may be added to the value in the RAM. When the rewriting of the RAM 32 is completed, PVA sets the integrated value Σα and the integrated number n to zero. Proceed to.

When n<LGN in Pal, it is determined that the number of samples is small and the accuracy is poor, and the integrated value Σα and the integrated number n are set to zero and the process proceeds to PTO. Next, at P7°, a steady learning calculation is performed and this routine ends.

P. Although the details will be omitted here, it is determined that it is in a steady state, and the value in the RAM 32 is rewritten using the average feedbank correction coefficient W as in the case of a transient state. Transient learning coefficient GM
It is preferable to allocate it according to the engine rotational speed N and the basic injection amount Tp instead of allocating φ1-GMφn.

Next, FIG. 14 is a flowchart showing a calculation routine for calculating the basic injection amount Tp and the transient correction amount DM, and this calculation routine differs from the calculation routine shown in FIG. 3 in the following points. That is, in this routine, the transient learning coefficient GMφ is referred to in step PB4, and the transient correction amount DM is calculated in accordance with the following equation (2) in step pH15.

DM=DKX (MφXGMφ−M) ・・・・・・■
Note that the transient learning coefficient GMφ is referred to by retrieving the value learned for the cooling water temperature Tw in the feedback routine from the address of the RAM 32 corresponding to the current cooling water temperature TW. This type of transient learning control is effective because the adhesion of the intake system and the amount of floating fuel may change depending on the nature of the fuel.
Furthermore, since this changes over time depending on the amount of deposit attached to the intake system, the purpose is to correct this change. Here, if inferior fuel is used, the air-fuel ratio shifts toward lean during acceleration.

Therefore, in this embodiment, the average feedback correction coefficient i that becomes a large value during a transition during feedback control is used to rewrite the transient learning coefficient GMφ in a direction that becomes a large value. Therefore, the transient correction amount DM also increases, so that the lean air-fuel ratio during acceleration is corrected. Furthermore, the accuracy of the transient correction amount DM can be increased little by little each time learning is repeated.

In this way, by using the transient learning coefficient GMφ through learning control, it is possible to provide the optimum transient correction amount DM even when using inferior fuel or when deposits are attached to the intake system. I can do it. Therefore, the accuracy of air-fuel ratio control can be improved.

(Effects) As explained above, according to the present invention, the air-fuel ratio is controlled not only during acceleration and deceleration of the engine, but also during fuel cut recovery, when poor quality fuel is used, or when deposits are attached to the intake system. Since the accuracy of the engine can be greatly improved, it is possible to improve drivability, reduce the amount of harmful exhaust gases, and increase output.

Further, since the amount increase correction according to the coolant temperature can be significantly reduced in order to prevent breathing during acceleration during warm-up, it is possible to improve fuel efficiency and prevent the plug from smoldering.

Furthermore, since the various corrections that have been performed in the past can be limited to the minimum ratio correction, the control configuration can be simplified.
Matching man-hours can also be reduced, and matching time can be shortened.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of this invention, FIGS. 2 to 10 are diagrams showing a first embodiment of this invention, FIG. 2 is a schematic configuration diagram thereof, and FIGS. 3 and 4 are diagrams showing a fuel Flowcharts showing the main routine of injection control, FIG. 5 is a flowchart showing a subroutine for calculating the transient correction amount, and FIG.
The figure is a flowchart showing a subroutine for calculating the correction coefficient, Fig. 7 is a table map showing an example of the balance amount, Fig. 8 is a table map of the cooling water correction coefficient, Fig. 9 is a table map of the rotation speed correction coefficient, Figure 10 (A), (
B) and (C) are graphs showing the waveforms of each signal during acceleration, low speed, and gear change, and FIGS. 11 and 12 are diagrams showing the second embodiment of the present invention. FIG. 12 is a flow chart showing the main routine of fuel injection control during fuel cut recovery, FIG. 12 is a graph showing the waveform of each signal during fuel cut recovery, and FIGS. 13 and 14 are diagrams showing a third embodiment of the present invention. , FIG. 13 is a flowchart showing the learning control feedback routine,
FIG. 14 is a flowchart showing the main routine of fuel injection control using learning control. 21...Engine, 23...Fuel injection valve (fuel supply means), 25.
26.27.28... Operating state detection means, 29
...Control unit (basic injection amount calculation means, equilibrium amount calculation means, difference value calculation means, transient correction amount calculation means, predictive variable calculation means, fuel injection amount calculation means).

Claims (1)

[Scope of Claims] a) Operating state detection means for detecting the operating state of the engine; b) Basic injection amount calculation means for calculating the basic injection amount based on the operating state of the engine; c) Based on the operating state of the engine. d) Balance amount calculation means that calculates the equilibrium amount of adhesion and floating fuel on the intake system in a steady state based on the equilibrium amount of adhesion and floating fuel calculated by the equilibrium amount calculation means and the adhesion on the intake system at that time. , a difference value calculation means for calculating a difference value between the floating fuel quantity and a predictive variable; a transient correction amount calculation means for calculating a correction amount; and f) a predictive variable calculation means for newly calculating the predictive variable based on the transient correction amount calculated by the transient correction amount calculation means and the predictive variable of the adhesion and floating fuel. and g) fuel injection amount calculation means for calculating the fuel injection amount based on the basic injection amount calculated by the basic injection amount calculation means and the transient correction amount calculated by the transient correction amount calculation means and outputting an injection signal. , h) a fuel supply means for supplying fuel to the engine based on an injection signal; and a fuel injection control device for an internal combustion engine.