JP2573930B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a fuel supply control device for an internal combustion engine, and more particularly, to a fuel supply control device during a normal operation or during an acceleration according to a change in fuel properties. It relates to a device for correcting.

(Prior Art) Recently, there has been a tendency for engines to be required to have higher fuel economy and drivability. From such a viewpoint, microcomputers and the like are applied to more precisely control the air-fuel ratio. In such control, the characteristics of the fuel may also occupy an important position as input information.

As a conventional fuel supply control device, for example,
There is one described in JP-A-43138. In this device, an air-fuel ratio is detected by an oxygen sensor provided in an exhaust pipe, and a feedback control is performed so that the air-fuel ratio is set to a target value by operating a fuel injection amount based on the detection result. That is, the injection pulse signal (final injection amount) Ti output to the injector is calculated according to the following equation based on the detection results of the air-fuel ratio, the intake air amount, the engine speed, the cooling water temperature, and the like.

Ti = Tp × Co × α + Ts where Tp: basic injection amount Co: various correction coefficients α: air-fuel ratio feedback correction coefficient Ts: voltage correction In the above equation, various correction coefficients Co are calculated according to the following equations.

Co = 1 + K _TRM + K _MR + K _TW + K _AS + K _AI + K _ACC + K _H ... K _TRM : Mixing ratio correction coefficient K _MR : Mixing ratio correction coefficient K _TW : Water temperature increase correction coefficient K _AS : Start and after start Increase correction coefficient K _AI : Increase correction coefficient after idling K _ACC : Acceleration increase correction coefficient K _H : High water temperature increase correction coefficient The calculation in the formula gives a normal injection amount, which is a predetermined crank angle for each revolution of the engine. Injected in. In addition, there is interrupt injection during acceleration. For example, when the throttle valve switch is turned off after about 1 second, interrupt injection is performed in addition to the normal injection amount.

The various correction values are set on the assumption that all standard fuels (for example, regular gasoline) are used as fuel supplied to the engine.

(Problems to be Solved by the Invention) However, in such a conventional fuel supply control device, typical fuel properties (for example, 50% distilling temperature: T
_The above-described various correction values are calculated and set according to the operating conditions (for example, a preset value or a table) so that optimal acceleration performance and exhaust emission performance can be obtained when gasoline of ₅₀ = 95 to 100 ° C. is used. (Read from the map), so that even when the properties of the supplied fuel change and the liquefaction level (that is, volatility) changes, a matching constant (correction coefficient) suitable for typical fuel properties ) And the injection amount is corrected.
The value of the supplied air-fuel ratio deviates from the required value. That is,
Since the air-fuel ratio correction due to the change in the properties of the supplied fuel is not considered, in such a case, a deviation occurs between the air-fuel ratio calculated based on using the standard fuel and the actual air-fuel ratio, and an accurate air-fuel ratio is generated. It was difficult to control the fuel ratio.

In particular, the problem becomes remarkable during acceleration. Here, the behavior of the air-fuel ratio during acceleration will be described. The amount of intake air increases during acceleration, and even if the amount of fuel is increased, fuel that contributes to combustion is a part of the supplied fuel. The remainder is divided into the amount of fuel supplied to adhere to the wall surface in the intake pipe and the amount of fuel entering the combustion chamber, and there is a part of fuel discharged to the exhaust pipe without burning. As the fuel becomes heavier, the amount of adhesion to the wall increases,
In addition, the amount of HC discharged to the exhaust pipe without burning increases. For this reason, the air-fuel ratio contributing to the combustion at the time of acceleration becomes leaner as the fuel becomes heavier, and the torque generated by the combustion becomes insufficient and the drivability deteriorates. Conversely, when a light fuel is used, the amount of wall adhesion decreases, the air-fuel ratio becomes excessively rich, the emission deteriorates, the ignition plug smolders, and a misfire may occur. Therefore, it is desirable to take into account differences in the properties of the fuel used when correcting the fuel amount. In particular, it is desired to improve the driving feeling during acceleration.

(Object of the Invention) Therefore, the present invention detects a parameter related to the property of the fuel used, and corrects the fuel supply amount such that the parameter matches a target value obtained from the throttle opening and the like and delayed for a predetermined period. By doing so, it is an object of the present invention to make the fuel supply amount appropriate irrespective of the change in the properties of the fuel, and to further improve the acceleration responsiveness, operability, and exhaust performance of the engine.

(Means for Solving the Problems) To achieve the above object, the fuel supply control device for an internal combustion engine according to the present invention has a basic conceptual diagram as shown in FIG. Operating state detecting means a for detecting the operating state of the engine from at least one of the degree or the pressure in the intake pipe, pressure detecting means b for detecting the combustion pressure of the engine, and fuel based on the output of the operating state detecting means. First calculating means c for calculating the basic supply amount of
A second calculating means d for calculating an output torque parameter which increases and decreases in correlation with an output torque of the engine based on an output of the pressure detecting means; The reference target value of the output torque parameter is learned and stored in the storage unit,
Target setting means e for setting a target value of the output torque parameter based on the reference target value and the output of the operating state detecting means, and delaying and outputting the target value
Correction amount calculating means f for calculating a fuel correction amount for correcting the basic supply amount of fuel so that the output torque parameter matches the delayed target value; and correcting the basic supply amount of fuel with the fuel correction amount. And a fuel supply unit h for supplying fuel to the engine based on the output of the supply amount determination unit.

Further, the correction amount calculating means f calculates the fuel correction amount such that the fuel supply amount is increased and corrected as the output torque parameter is smaller than the delayed target value, or the operating state detection is performed. It is preferable that the calculation of the fuel correction amount is executed only when the air-fuel ratio recognized from the output of the means is on the lean side.

Further, the target setting unit e obtains a moving average from the set target value of the output torque parameter and outputs the moving average as a delayed target value, or based on an output from the operating state detecting unit. The difference between the target value set as the throttle opening is smaller is larger, and the difference between the set target value is smaller as the difference between the throttle opening and the previous throttle opening is smaller. It is preferable that the value is output as a delayed target value.

(Operation) In the present invention, while a parameter (output torque) related to the property of the fuel used is detected, a target value of the parameter is set based on the throttle opening and the like, and the set value is set to a predetermined value. Delayed for a period. Then, the fuel amount is corrected so that the detected parameter value matches the delayed target value. Therefore, the fuel supply amount is appropriate regardless of the change in the fuel properties, and the acceleration response, driving feeling,
Exhaust performance is improved.

Hereinafter, the present invention will be described with reference to the drawings.

FIGS. 2 to 10 are views showing a first embodiment of the present invention. The fuel supply control is a method of detecting a combustion speed from an in-cylinder pressure signal as a fuel property detection parameter and determining the fuel property based on the detected value. The example which applied to the apparatus is shown.

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes a four-cylinder engine, in which intake air is supplied to each cylinder from an air cleaner 2 through an intake pipe 3 as indicated by an arrow in the figure, and fuel is injected based on an injection signal Si (fuel supply means).
4 injected. A spark plug 5 is mounted on each cylinder, and a high-voltage pulse Hp from an ignition coil 6 is supplied to the spark plug 5 via a distributor (not shown). The ignition coil 6 generates a high-voltage pulse based on the ignition signal Sp.
Hp is generated and supplied to the ignition plug 5, and the air-fuel mixture in the cylinder is ignited and exploded by the discharge of the high-pressure pulse Hp, becomes exhaust, and is discharged from the exhaust pipe 7 through the catalytic converter 8 and the muffler 9 sequentially. .

The flow rate Qa of the intake air is detected by the air flow meter 10 and controlled by the throttle valve 11 in the intake pipe 3. The opening Cv of the throttle valve 11 is a throttle sensor composed of a potentiometer, etc.
The air flow rate detected by 12 and bypassing the throttle valve 11 is AA
The idle speed is controlled by the C valve 13. On the other hand, the EGR amount is controlled by the EGR valve 14, and the operation of the EGR valve 14 is controlled by the VCM valve 15. 16 is a BC valve, and 17 is a check valve.

The temperature Tw of the cooling water flowing through the water jacket of the engine 1 is detected by a water temperature sensor 18, and the crank angles Ca and C ₁ of the engine are detected by a crank angle sensor 19. The oxygen concentration in the exhaust is detected by the oxygen sensor 20,
As the oxygen sensor 20, one having such a characteristic that its output Vs changes abruptly at a stoichiometric air-fuel ratio is used. Further, the combustion pressure (in-cylinder pressure) in the cylinder is detected by an in-cylinder pressure sensor 21. The in-cylinder pressure sensor 21 is constituted by a piezoelectric element and is molded as a washer for the ignition plug 5. Cylinder pressure sensor 21 detects a cylinder pressure which acts on the piezoelectric element via the spark plug 5, and outputs a charge signal S ₁₁ having a charge value corresponding to the cylinder pressure. The in-cylinder pressure sensor 21 is provided for each cylinder. In addition, the fuel temperature Tf is detected by the fuel temperature sensor 22, and the accelerator pedal depression angle Acc is detected by the accelerator sensor 23. The neutral position Nc of the transmission 24 is detected by a neutral switch 25, and the vehicle speed Ss is detected by a vehicle speed sensor 26. 27 is a canister, 28
Is a fuel pump.

The above-mentioned sensor groups 10, 12, 18, 19, 20, 22, 23, and 26 constitute operating state detecting means 29, and signals from the operating state detecting means 29 and the in-cylinder pressure sensor 21 are transmitted to the control unit.
Entered in 30. The control unit 30 calculates the in-cylinder pressure, the engine load, and the engine speed based on the sensor information, and controls the combustion state optimally according to the calculation result. There are various types of combustion control such as EGR control, but here, the description will be limited to air-fuel ratio control.

FIG. 3 is an overall block diagram of a portion related to air-fuel ratio control. In FIG. 3, the control unit 30 includes charge amplifiers 31a to 31d, a multiplexer (MPX) 32,
It comprises a high-frequency vibration detection circuit 33, a low-frequency vibration detection circuit 34, and a microcomputer 35. Charge output S ₁₁ to S ₁₄ from the cylinder pressure sensor 21a~21d disposed in each cylinder is input to the charge amplifier 31a~31d respectively. Charge amplifier 31a is charge - form a voltage conversion amplifier, the charge output S ₁₁
Converts the voltage signal S ₂₁ and outputs to the multiplexer 32. Incidentally, the same applies for other charge amplifier 31b-31d, and outputs a voltage signal S ₂₂ to S _24, respectively. The in-cylinder pressure sensors 21a to 21d and charge amplifiers 31a to 31d
Constitute pressure detecting means 36.

On the other hand, a signal from the crank angle sensor 19 is further input to the control unit 30. The crank angle sensor 19 outputs the reference signal Ca 70 ° before the compression top dead center (BTDC) of each cylinder.
And it outputs a 1-degree crank angle (or twice) and outputs a position signal C ₁ for each. In addition, out of the reference signal Ca,
The pulse width of the reference signal corresponding to the first cylinder is wider than that of the reference signals corresponding to the other cylinders. Also,
Its position signal C ₁ may be configured to output other example for each angle of 0.1 degrees, etc., control accuracy enough to finely improved.

The multiplexer 32 outputs the output signals of the charge amplifiers 31a to 31d based on the selection signal Sc from the microcomputer 35.
Switching S ₂₁ to S ₂₄ of each cylinder Alternatively, outputs a signal S _2n to the high-frequency vibration detection circuit 33 and low-frequency vibration detection circuit 34. Frequency vibration detection circuit 33 outputs the output signal S _2n multiplexer 32 amplifies the extracted corresponding components to knocking vibration, as a signal S ₇ performs a process of integration such as the microcomputer 35. In addition, the low-frequency vibration detection circuit 34
Outputs compressed from the signal S _2n, burning, a signal S ₉ that corresponds to the cylinder pressure generated in each combustion process in the exhaust to the microcomputer 35.

The microcomputer 35 has functions as first and second calculation means, target setting means, correction amount calculation means and supply amount determination means, and includes a CPU 50, a ROM 51, a RAM 52, a non-volatile memory (NVM) and an I / O port 54. It consists of. CPU50 is R
In accordance with the program written in OM51, necessary external data can be fetched from NVM53, and RAM52 and N
While transmitting and receiving data to and from the VM 53, processing values required for sensor abnormality determination and knock control are calculated, and the processed data is output to the I / O port 54 as necessary. I
The signals from the crank angle sensor 19, the high frequency vibration detection circuit 33 and the low frequency vibration detection circuit 34 are input to the / O port 54, and the selection signal Sc and the injection signal S are output from the I / O port 54.
i and the ignition signal Sp are output.

Next, the operation will be described. FIGS. 4 and 6 to 8 are flowcharts showing the programs JOB-1 to JOB-3 written in the ROM 51, respectively.

FIG. 4 shows a routine for detecting the indicated mean effective pressure Pi. This routine is executed once every 4 degrees of the crank angle (or any value between 2 and 10 degrees).

First, the current crank angle before the compression top dead center 50 ° with P ₁ determines whether or not (hereinafter, 50 ° abbreviated as in BTDC) earlier, when the 50 ° BTDC previously proceeds to P _2. Crank angle at P ₂ is determined whether or not the 50 ° BTDC, and then returns determined that the advance side of 50 ° must match the 50 ° BTDC. On the other hand, if the matching 50 ° BTDC, indicated mean effective pressure Pi (hereinafter appropriately Pi only abbreviated) proceeds to P ₃ to initiate the operation of the. P ₃ in the cylinder pressure P converted A / D, to the value and P _'n-1. Then, as the stroke volume V _n-1 by P ₄ 50
° Place the combustion chamber volume V ₅₀ ° _BTDC when the BTDC, 50 ° B at P ₅
The value of Pi at the time of TDC is looked up from a predetermined table map. This table map is Pi ₅₀゜_BTDC = func
As represented by the function form (Qa, N), map values are stored in advance by experiments or the like in accordance with the intake air amount and the rotation speed. Then, Pi ₅₀ as old value of Pi Pi 'with P _6
を Set _BTDC and return.

On the other hand, when there is no 50 ° BTDC previously in step P ₁ is P ₇
Then, it is determined whether or not it is before 5 ° (ATDC50 °) after the compression top dead center. If it is not before 50 ° TADC, it returns because it is after 50 ° ATDC. When a 50 ° ATDC previous proceed to the step after the P _8. First, the in-cylinder pressure P is A / D converted by the P _8, the value and Pn '. Then, to look up the P ₉ combustion chamber volume Vn. Vn is geometrically determined from the specifications of the engine, and includes, for example, a calculation method based on the following equation or a method of looking up from a table calculated and digitized in advance according to this equation.

However, B: cylinder bore diameter l: connecting rod length r: Stroke × (1/2) .theta.n: crank angle then the previous (4 ° CA before) this cylinder pressure Pn 'in P ₁₀
The average value of the in _- cylinder pressure P _n-1 ′ is determined, and this is set as Pn. This relationship is illustrated in FIG. In P ₁₁ the difference value ΔVn of the combustion chamber volume is computed according to the following equation.

ΔVn = Vn−Vn− ₁ where Vn− ₁ : The previous combustion chamber volume difference value ΔVn is negative before TDC and positive when TDC. Then, the workload of ΔPi made during the volume change made a difference value ΔVn at P ₁₂ is calculated according to the following equation, the Pi an integrated value of Pi in P ₁₃ is calculated according to the following equation.

ΔPi = Pn × ΔVn ...... Pi = Pi '+ ΔPi ...... However, Pi': previous value and, for the computation of the last order in the P ₁₄ (after 4 ° _{CA), V n-1,} P 'n- ₁ , Put this value in Pi. Incidentally, when the process returns accordance NO instruction in step P ₇ are considered to calculation of Pi is completed, Pi at this time 50 °
This means that the work amount Pi between BTDC and 50 ゜ ATDC has been calculated. By executing the above routine, the indicated mean effective pressure Pi corresponding to the property of the used fuel is accurately detected.

In the above-described JOB-1, the amount of work is obtained by integrating Pi over a range of 50 ° BTDC to 50 ° ATDC. This is not limited to the section of ± 50 °.
It may be obtained by a process slightly different from 1 and an example thereof is shown in FIG. The 'In this time of crank angle at P _101, it is determined whether or not the 40 ° BTDC after, when the prior 40 ° BTDC Old value Pi of Pi in P _102' 6 view of JOB-1 clears the To return. When the 40 ° BTDC after the crank angle is determined whether or not the 40 ° ATDC earlier P _103, to return when not previously. When the previous cylinder pressure P is A / D converted by the P _104, to its value as Pn. Next, at _P105 , the current work amount Δ
Pi is calculated according to the following equation.

ΔPi = Pn × θn In the formula, θn is a crank angle to be zero (origin) at TDC, and takes a value of [-] at BTDC and [+] at ATDC. The integrated value Pi of the P ₁₀₆ .DELTA.Pi calculated according to the following equation, put the current value Pi Old value Pi 'for the next operation in the P _107.

Pi = Pi ′ × ΔPi Pi can also be obtained by such a routine JOB-1 ′. In this case, since the interval is ± 40 °, approximately Vn
∝θ, which simplifies the arithmetic expression.

The gist of the present invention is to correct the fuel supply amount so that the Pi detected in this way approaches the target Pi (= Pim) and to make the supply air-fuel ratio appropriate regardless of the change in the fuel property. Here, the basic principle will be described.

First, the target value Pim is given as a function {Pim = func (V, N)} of the throttle opening Cv and the engine speed N. If the Tp portion (Tp is proportional to the intake air amount Qa) of the fuel amount Ti supplied during acceleration is completely burned, Pim corresponding to Pi in a steady state is obtained.
Can be achieved. On the other hand, if Pi has not reached Pim, it is considered that part of Tp has burned to become Pi, and the fuel amount corresponding to Pi is T _PB , and the unburned portion T _PU is the amount attached to the wall surface. The following equation is established. When this is modified to obtain _TPU , the following equation is obtained.

Assuming that the next basic injection amount is C ′ × Tp = Tp + _TPU , a temporary correction coefficient C ′ is obtained by substituting the equation into the following equation.

In this case, when Pi = Pim, C '= 1, so that the amount is not substantially increased. Since the amount of the next wall surface adhesion may be smaller than this time, the value of the next correction coefficient C is determined by multiplying the coefficient by 1 or less as shown by the following equation.

C = β−C ′ where β <1 According to the correction coefficient C, the next corrected basic injection amount C · Tp is expressed by the following equation. Become.

However, Co = 1 + K _TRM + K _MR + K _{TW As} is clear from the above equation, A _AI , K _ACC , K _H
Since the correction term is not required, the number of matching steps is reduced accordingly. Although the post-start increase correction coefficient _KAS is necessary, it is omitted for convenience of explanation.

Thus, the unburned portion _TPU is obtained from the comparison between Pi and Pim,
If the next injection amount is appropriately corrected based on this data, the fuel amount at the time of acceleration or the like will be optimal in consideration of the amount of wall adhesion that varies depending on the degree of heavy fuel. This embodiment is based on this principle. Specifically, light fuel is basically used as a matching base, and the injection amount is corrected to an increasing side according to the fuel property. Since the increase in the normal injection amount cannot be made in time for the first (first) fuel injection of the start of acceleration, in this embodiment, the interrupt injection is performed at the time of rapid acceleration.

In addition, during transient operation, the setting of Pim may be inaccurate, and the variation in detection sensitivity of the pressure detecting means 36,
Considering the change over time, it is preferable to adopt the concept of learning control when setting Pim.Therefore, the Pi detection value in the steady state is learned sequentially, and when setting Pim, the learning value is used to set Pim. High accuracy is maintained.

In addition, simply comparing Pi and Pim would mean
The steep rise of Pim gives Pim a delay to mitigate shocks during sudden acceleration and dramatically improve driving feeling.

Next, actual injection amount control based on the above principle will be described.

FIG. 7 is a routine showing a program JOB-2 for the interrupt injection control during acceleration, and this routine is executed once every predetermined time (for example, every 10 msec). First reads the throttle valve opening degree Cv, intake air volume Qa, and the engine speed N in P _21, P
_{At 22} , the basic injection amount Tp (Tp = K × Qa / N) is calculated. Then, various necessary correction coefficient K _TRM at P _23, looks up the K _MR, K _TW, to calculate a feedback correction coefficient for controlling the air-fuel ratio in the P ₂₄ lambda alpha. In P ₂₅ obtains a voltage correction amount Ts. The above processing is the same as the conventional processing. Then
In P ₂₆ per throttle valve opening degree Cv amount of change ΔCv (ΔCv = Cv-C
v ', where, Cv = Determines the previous value), and compares this with P ₂₇ to a predetermined value a. Although a may be a constant value, it is changed according to operating conditions. That is, it is preferable that a = func (Tp, N). When ΔCv <a, it returns because it is not sudden acceleration, and ΔCv ≧
Interrupt injection quantity Tad at P ₂₈ it is determined that the rapid acceleration when the a
d 'is looked up from a table map expressed in a function form of Tadd' = func (Tw). The cooling water temperature
Tw is read by a background job (BGJ) not shown. Then, the throttle valve 11 is the last time in the P ₂₉ (10msec
Each time), it is determined whether or not it is in the fully closed position and has deviated from the current fully closed position, that is, whether it is immediately after opening from the fully closed position. It is determined that rapid acceleration from fairly low load if immediately after, as well as look up the interrupt correction amount To a To = func (Tw) becomes functional form of table maps at P _30,
Adding To a final interruption injection quantity Tadd corrected to interrupt injection amount Tadd 'at P _31, performs an interrupt injection corresponding to Tadd at P _32. Meanwhile, the increase of the interrupt correction amount To and if not immediately after opening from the fully closed at P ₂₉ is determined to be unnecessary, the process proceeds to P ₃₂ as Tadd = Tadd 'at P _33.

FIG. 8 is a routine showing a program for controlling the injection amount based on the Pi detection information. This routine is executed once for each reference crank angle of each cylinder. First, look up a reference target value Pim ₀ of Pi in P ₄₁ from _{Pim 0 = func (Cv, N} ) become functional form of a table map. Throttle valve opening degree Cv is because those earliest reacts to the driver's intention, the Pim ₀ which varies depending on the value of Cv If the Cv and parameters can be obtained quickly element. Then, learning the target value Pim of Pi in learning routine consisting of P ₂₀₁ to P _205. Learning routine in this embodiment is to learn the difference ΔPim between the detection Pi and the reference target value Pim _0.

First, in _P201 , it is determined whether or not a learning condition is satisfied. The learning condition may be learned within a predetermined engine temperature range, within a predetermined load fluctuation, and within a predetermined engine speed fluctuation. When the learning condition is satisfied, a difference ΔPim (ΔPim = Pi−Pim ₀ ) between the detected Pi and the reference target Pim ₀ is calculated in P ₂₀₂ ,
Nonvolatile memory this with P ₂₀₃ as ΔPim = func (Cv, N) of the learning table, represented by the functional form that the data
Write to 53, proceed to the P _204. Note that this learning data (Δ
Pim) is learned with positive and negative signs. In this way, ΔPim is learned under predetermined learning conditions, and the values in the table are sequentially updated to become the latest data set group.

On the other hand, when there is no learning condition P ₂₀₁ moves to read the subsequent processing P ₂₀₄ to jump P _202, P _203. Learning value Δ at P ₂₀₄
Look up the Pim, it calculates the present target Pi a (= Pim) according to the following equation in P _205.

Pim = Pim ₀ + ΔPim By performing such learning, the data in the table is constantly updated to the optimal data as described above.
Therefore, for example, variations in the sensitivity of the pressure detecting means 36,
Even if there is a change over time in the apparatus, it is possible to absorb a variation in data and provide an appropriate target Pi. In addition, it is possible to always provide an appropriate target Pi even when the atmospheric pressure changes while traveling at high altitudes or in a transient operation state, without the problem on the side of the device. It will be expensive.

After the learning routine as described above, the flow returns to the injection amount control flow again. First calculated according to the following equation delay target value Pimd at P _206. Pimd is a value obtained by delaying the target value Pim for a predetermined period of time, in order to intentionally delay the set target value so as not to have a sharp Pim particularly during acceleration.

Pimd = k.times.Pimd '+ (1-k) .times.Pim where Pimd': previous value 0 <k <1 The calculation of the equation means that the moving average of Pimd is obtained. The calculation of Pimd is not limited to the method of the expression, but may be another calculation method, for example, a calculation method based on the following expression.

In the case of the formula, when the throttle valve opening Cv is suddenly accelerated from a small value, the rise of Pimd is delayed, and when ΔCv becomes small, it approaches Pim. Delay target value in the P ₄₂ Pimd and the current detection value Pi
Is calculated (ΔPi = Pimd−Pi), and the following items are determined in a step consisting of P _{43 to} P ₄₅ to determine whether or not to perform feedback control of the injection amount by detecting Pi.

P _43: ΔPi ≧ Dpo (predetermined value) or P _44: Vs ≦ Vso or (air-fuel ratio is either lean than a predetermined value), however, Vs: output of the oxygen sensor 20 Vso: lean predetermined value P _45: either Tp ≧ Tpo (Is the load equal to or greater than a predetermined value?) The condition of Tp ≧ Tpo is imposed because when the value of Tp is small, combustion is unstable and the value of Pi varies widely.

When above conditions are satisfied, it is determined that feedback control to calculate the correction coefficient C of the normal injection amount at P ₄₆ from the basic principle described above according to the following equation, the process proceeds to P _58.

On the other hand, it is determined not to perform the injection amount of the feedback control by Pi detected when following the NO instruction P ₄₃ to P _45, the process proceeds to P ₅₈ as C = 1 in P _47. In _P58 , the final injection amount Ti is calculated in accordance with the following equation, and the fuel of Ti amount is injected at the normal synchronous injection timing.

Ti = C × Tp × Co × α + Ts In this manner, based on the Pi detection information which is a parameter relating to the property of the fuel used, the injection amount (acceleration) is adjusted using the correction coefficient C so as to match the target delay value Pimd. (Including interrupt injection at the time) is appropriately feedback-corrected. Therefore, for example, when heavy gasoline is used, the gasoline component that actually contributes to combustion is smaller than the standard fuel, and the mixture ratio is substantially lean. On the other hand, according to the present apparatus, the heavier level of the used fuel is appropriately determined, and the amount of wall flow adhesion is sufficiently determined according to the deviation of the detection Pi from the delay target value Pimd according to the degree of the heavier fuel. Since the injection amount is corrected in consideration of the above, the state where the gasoline component contributing to combustion is small when heavy gasoline is used as described above is corrected. That is, at this time, the correction is performed so that the total amount of the fuel injection amount increases. Accordingly, a state in which the mixture ratio becomes lean is substantially avoided, and the original effect of the air-fuel ratio control can be achieved. In addition, when the interruption injection is performed, the fuel injection amount is corrected so as to increase the total amount, so that it is possible to sufficiently improve the acceleration performance.

As a result, at the time of acceleration, the air-fuel ratio at the time of acceleration will be corrected to an appropriate value corresponding to the property of the fuel used at that time, and the occurrence of hesitation, tumbling, etc. can be suppressed, It is possible to improve the acceleration response of the engine. Further, since the supply air-fuel ratio becomes an appropriate value, the exhaust emission characteristics can be improved.
In this case, since the data is learned when setting the target value Pim, the setting accuracy is high and the injection amount correction can be effectively performed. Furthermore, since the target value Pim is delayed for a predetermined period and the injection amount is corrected so that the Pi detection value matches the delayed target value Pi, the rising of Pim is excessively steep even during rapid acceleration. Characteristics, the rise of the torque during acceleration becomes smooth, and the driving feeling can be remarkably improved.

It should be noted that the effect of this embodiment is based on the ninth and tenth experimental results.
As shown in the figure, there are prominent ones. In FIG. 9, 3
The contents of specifications 1 to 3 shown in the types of line graphs are as shown in the following table.

As shown in Fig. 10, after the throttle switch was turned on, the detected cylinder pressure Pi was changed to the target cylinder pressure.
The measurement was performed by measuring the time required to reach Pi 'until the position indicated by T in FIG. As is apparent from FIG. 9, according to the present embodiment, the time to reach the target value Pim is reduced to about 1/3, and the acceleration performance is greatly improved.

As described above, in the present embodiment, the program shown in FIG. 8 has a learning routine (between G and G ').
Even if there is a variation in the sensitivity of the pressure detecting means 36, a change over time of the device, or the like, or even if the running conditions change, the control accuracy can always be made high as an appropriate target Pi.

This learning routine may be omitted as acceleration interrupt injection control program shown in FIG. 11, since the omitted step of learning routine following the P _41, the delay target value according to the following equation or P ₂₀₇ Pimd will be calculated.

Pimd = k × Pimd ′ + (1-k) × Pim ₀ ...... That is, since the learning routine is omitted, Pim ₀ = fu
Pimd by moving average directly from the map nc (Cv, N)
Will be required. Therefore, when the variation in the sensitivity of the pressure detecting means 36 is small, there is no problem even if the learning routine is omitted, and there is an advantage that the processing is simple and the storage capacity is small. Since the object of the present invention cannot be achieved in response to the variation in sensitivity, the change over time of the device, and the change in running conditions, control for executing a learning routine as in the present embodiment is preferable.

Here, in the present embodiment, the throttle valve opening Cv is used for the acceleration determination. However, other factors may be used for the acceleration determination, and these aspects will be described as other embodiments.

12, 13 Figure is a diagram showing a second embodiment of the present invention, without using the throttle valve opening degree Cv acceleration determining in this embodiment uses the intake pipe pressure P _B. That is, FIG. 12 is a routine showing a program of the interrupt injection control at the time of acceleration. In the description of this routine, steps for performing the same processing as in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The different steps are denoted by step numbers surrounded by a circle and their contents will be described.

In Figure 12, without loading the throttle valve opening degree Cv At P _51, Q
Read only a and N. P ₂₅ followed the P ₅₂ intake pipe pressure P
_{For B} , the change amount ΔP _B (ΔP _B = P _B −P _B ′, where: P _B ′ =
It determines the previous value), and compares this with P ₅₃ and a predetermined value b.
Then, the program returns from non-rapid acceleration when the [Delta] P _B <b, the process proceeds to the determination to P ₂₉ and subsequent steps to be rapid acceleration when the [Delta] P _B ≧ b. Although not illustrated in FIG. 12, since in this embodiment uses the intake pipe pressure P _B as a parameter for the acceleration judgment, a similar routine to that corresponding to the JOB-3 of the first embodiment, step _{P 41 Pim 0 = func (P} B, N) the reference target value Pim ₀ in made by looking up the functional form of a table map, DerutaPim the DerutaPim the same learning routine = func (P _B, N) comprising the functional form Lookup from table map of. Therefore, in this embodiment, although there is a difference in the acceleration determination, the same effect as in the first embodiment can be obtained.

Further, according to this method, there is no overshoot in the initial stage of acceleration unlike the intake air amount signal, so that there is an advantage that a smooth driving performance can be obtained. That is, as shown in the timing chart at the time of acceleration in FIG. 13, if the throttle valve opening degree Cv now changes as shown in FIG. 13A, the speed of change to the intake pipe pressure P is a sonic speed, Although a rise delay occurs, the throttle valve opening Cv changes as shown in FIG.
Will be similar to Further, since the intake pipe pressure P _B changes in accordance with the movement of the opening area of the intake throttle valve unit, rising early and later becomes slope somewhat steep. On the other hand, the intake air amount Qa is further rising is delayed than P _B as shown in FIG. (C), the rising inclination to fill the intake pipe volume overshoot becomes steeper than P _B. Therefore, the basic injection amount Tp calculated based on the intake air amount Qa changes in proportion to Qa up to the Tp limit as shown in FIG. When the change of the reference target value Pim ₀ with respect to the change of each value is illustrated by the parameters Cv, P _B , and Tp, the change is as shown in FIG.
As is clear from this figure, the driver's value given by Pim ₀ = func (Cv, N) and Pim ₀ = func (P _B , N) is better than that given by Pim ₀ = func (Tp, N). A target value close to a feeling of stepping can be given.

FIG. 14 is a view showing a third embodiment of the present invention, in which the basic injection amount Tp is used for acceleration determination without using the throttle opening Cv. That is, FIG. 14 is a routine showing a program of the interrupt injection control at the time of acceleration. In the description of this routine, steps for performing the same processing as in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The different steps are denoted by step numbers surrounded by a circle and their contents will be described.

In Figure 14, without loading the throttle valve in the P ₆₁ opening Cv, Q
Read only a and N. Followed by P ₂₅ P ₆₂ in the basic injection quantity Tp
The amount of change ΔTp (ΔTp = Tp-Tp ' , where: Tp = previous value) per seek, to compare this with P ₆₃ to a predetermined value c. And when ΔTp <c, it returns because it is not sudden acceleration.
When the [Delta] Tp ≧ c proceeds to decision and subsequent P ₂₉ in step with a rapid acceleration. Although not shown in FIG. 14, in the present embodiment, the basic injection amount Tp is used as a parameter for the acceleration determination. Therefore, in the same routine as that corresponding to JOB-3 in the first embodiment, step look up a reference target value Pim ₀ from _{Pim 0 = func (Tp, N} ) become functional form table maps the P _41. Therefore, in this embodiment, although there is a difference in the acceleration determination, the same effect as in the first embodiment can be obtained.

FIG. 15 is a view showing a fourth embodiment of the present invention. In this embodiment, the opening area Av of the intake throttle valve portion is used for acceleration determination without using the throttle valve opening degree Cv. That is, FIG. 15 is a routine showing a program of the interrupt injection control at the time of acceleration. In the description of this routine, steps for performing the same processing as in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The different steps are denoted by step numbers surrounded by a circle and their contents will be described.

In Figure 15, the throttle valve opening degree in step P ₇₁ followed P ₂₁
Based on Cv, the opening area Av of the intake throttle portion is calculated from a functional form of Av = func (Cv). Further, the amount of change per subsequent P ₇₂ in the opening area Av in _{P 25 ΔAv (ΔAv = Av-} Av ', where: A
v '= Determines the previous value), and compares this with P ₇₃ with a predetermined value d. Then, when the ΔAv <d returns from non-rapid acceleration, the process proceeds to the determination to P ₂₉ and subsequent steps to be rapid acceleration when ΔAv ≧ d. Although not shown in FIG. 15, in this embodiment, the opening area is used as a parameter for the acceleration determination.
Because with Av, the same routine as that corresponding to the JOB-3 of the first _{embodiment, Pim 0 = func (Av,} N) comprising a table map of a function form the reference target value Pim ₀ in step P ₅₁ From the learning routine, and similarly in the learning routine, Δ
Pim is looked up from a function-format table map of ΔPim = func (Av, N). Therefore, in this embodiment, although there is a difference in the acceleration determination, the same effect as in the first embodiment can be obtained.

Further, in this embodiment the case of the timing chart shown in FIG. 13, the movement of Pim ₀ is characterized in that become func (Cv, N) and func (P _B, N) in the middle of.

(Effect) According to the present invention, a parameter related to the property of the used fuel is detected, and the fuel supply amount is corrected so that the parameter matches a target value obtained from the throttle opening and the like and delayed for a predetermined period. Therefore, the supply air-fuel ratio can be made appropriate irrespective of the change in the properties of the fuel, and the acceleration response, drivability, and exhaust performance can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the basic concept of the present invention, FIGS. 2 to 10 are diagrams showing a first embodiment of the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. FIG. 4 is a flowchart showing a program for detecting the indicated mean effective pressure Pi, FIG. 5 is a graph showing the relationship between the in-cylinder pressure and the crank angle, and FIG. 6 is the indicated mean of other examples. FIG. 7 is a flowchart showing a program for detecting an effective pressure, FIG. 7 is a flowchart showing a program for interrupt injection control during acceleration, FIG. 8 is a flowchart showing a program for injection amount control based on the Pi detection information, and FIG.
FIG. 10 is a graph for explaining the effect, FIG. 10 is a timing chart showing the method of the experiment, FIG. 11 is a flowchart for explaining the effect of the learning, and FIGS.
FIG. 12 is a diagram showing a second embodiment of the present invention. FIG. 12 is a flowchart showing a program of the interrupt injection control at the time of acceleration, FIG. 13 is a timing chart for explaining the operation thereof, and FIG. FIG. 15 is a flowchart showing a program of the interrupt injection control at acceleration showing the third embodiment of the present invention, and FIG. 15 is a flowchart showing a program of the interrupt injection control at acceleration showing the fourth embodiment of the present invention. 1 ... engine 4 ... injector (fuel supply means) 29 ... operating state detection means 35 ... microcomputer (first and second calculation means, target setting means, correction amount calculation means, supply amount determination means ), 36 ... Pressure detecting means.

Claims (5)

(57) [Claims] A) operating state detecting means for detecting an operating state of the engine from at least one of an engine load, a rotational speed, a throttle valve opening degree, an intake pipe pressure, and the like; and b) detecting an engine combustion pressure. C) first calculating means for calculating a basic supply amount of fuel based on the output of the operating state detecting means, and d) correlating with the output torque of the engine based on the output of the pressure detecting means. E1) learning a reference target value of the output torque parameter for each operation state based on the output of the pressure detection means during steady operation, and storing the reference target value in the storage means. In addition, a target value of the output torque parameter is set based on the reference target value and the output of the operating state detecting means, and a target for delaying and outputting the target value is set. F1) correction amount calculating means for calculating a fuel correction amount for correcting the basic supply amount of fuel so that the output torque parameter coincides with the delayed target value; and g) calculating the basic supply amount of fuel. Supply amount determining means for determining a fuel supply amount to the engine by correcting with the fuel correction amount; and h) fuel supply means for supplying fuel to the engine based on an output of the supply amount determining means. A fuel supply control device for an internal combustion engine. F2) The correction amount calculating means calculates the fuel correction amount such that the fuel supply amount is increased and corrected as the output torque parameter becomes smaller than the delayed target value. The fuel supply control device for an internal combustion engine according to claim 1, wherein F3) The correction amount calculating means executes the calculation of the fuel correction amount only when the air-fuel ratio recognized from the output of the operating state detecting means is on the lean side. 3. A fuel supply control device for an internal combustion engine according to item 2. 4. The apparatus according to claim 1, wherein said target setting means calculates a moving average from the set target value of said output torque parameter and outputs the moving average as a delayed target value. A fuel supply control device for an internal combustion engine according to any one of the preceding claims. E3) The target setting means increases the difference between the throttle valve opening degree and the set target value as the throttle valve opening degree becomes smaller based on the output from the operating state detecting means. The value according to any one of claims 1 to 3, wherein a value obtained by reducing the difference from the set target value as the difference from the previous throttle opening degree is smaller is output as a delayed target value. A fuel supply control device for an internal combustion engine.