JPH02199251A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent an air-fuel ratio from being brought into a wide lean state during acceleration running by a method wherein, when, after the starting of an engine, a predetermined period starting from completion of warming up lapses, an increase correction factor is increased to a value higher than an increase correction value stored in a recording means. CONSTITUTION:A fuel injection control means B controls a fuel injection amount based on an output signal from an O2 sensor 19 arranged in an exhaust passage A. Under an acceleration running state detected by a detecting means C, an increase means D increases and corrects an injection amount according to a given increase correction factor, but until after the starting of an engine, a given period starting from a time when completion of warming-up is detected by a detecting means F lapses, a control means G increases an increase correction factor to a value higher than a given increase correction factor stored in a memory means E, and based on the increased factor, an injection amount is increased by an increase means D. This constitution enables fuel-air mixture to be prevented from being brought into a wide lean state during acceleration running until a specified period starting from completion of warming-up lapses after the starting of an engine.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel injection control device for an internal combustion engine.

[Conventional technology]

In a fuel-injected internal combustion engine, the basic fuel injection amount is usually calculated from the intake pipe negative pressure and the engine speed, or from the intake air amount and the engine speed. By correcting the basic fuel injection amount based on the output signal of the engine, the air-fuel mixture supplied into the engine cylinders is feedback-controlled to a predetermined target air-fuel ratio, for example, the stoichiometric air-fuel ratio. However, even with this kind of feedback control, when the fuel injection amount increases rapidly, such as during acceleration, the amount of injected fuel that adheres to the inner wall of the intake boat in the form of liquid fuel increases. Since the deposited liquid fuel is not immediately supplied into the engine cylinder after depositing, the air-fuel mixture supplied into the engine cylinder becomes temporarily lean. On the other hand, during deceleration operation, the absolute pressure inside the intake boat decreases, and as a result, the amount of evaporation of the liquid fuel adhering to the inner wall of the intake boat increases, causing the air-fuel mixture supplied to the engine cylinder to temporarily It becomes overly concentrated, that is, rich. Therefore, normally in a fuel-injected internal combustion engine, even during transient operating conditions such as acceleration or deceleration, the fuel-injection engine is operated in an accelerated manner so that the air-fuel mixture supplied into the engine cylinders reaches the target air-fuel ratio, such as the stoichiometric air-fuel ratio. At times, the amount of injected fuel is increased, and during deceleration operation, the amount of injected fuel is decreased. Therefore, in such a fuel-injected internal combustion engine, the air-fuel mixture supplied into the engine cylinders is controlled to approximately the target air-fuel ratio regardless of the operating state of the engine.

However, in such an internal combustion engine, for example, blow-by gas and lubricating oil enter the intake boat through the gap between the intake valve stem and the stem guide, and when the engine is used for a long period of time, these blow-by gases and lubricating oil leak. The carbon particulates contained in the air gradually accumulate on the back surface of the intake valve shank and on the inner wall surface of the intake boat. These deposits, such as carbon particles, have the property of retaining liquid fuel. Therefore, when deposits accumulate on the inner wall surface of the intake boat, the amount of liquid fuel adhering to the inner wall surface of the intake boat increases. It takes time for the liquid fuel attached to the engine cylinders to flow into the engine cylinder. Therefore, while the engine is relatively new, the air-fuel mixture is supplied into the engine cylinders and controlled to the stoichiometric air-fuel ratio regardless of the engine's operating state, but as the engine is used for a long period of time, deposits may be deposited on the inner wall of the intake boat, etc. If the fuel adheres to the inner wall of the intake boat, it takes time for the injected fuel to adhere to the inner wall surface of the intake boat and flow into the engine cylinder, so the air-fuel mixture supplied to the engine cylinder becomes lean during acceleration operation, and further Since the amount of injected fuel that adheres to the inner wall surface and the like increases, the air-fuel mixture supplied into the engine cylinder becomes rich during deceleration operation. As described above, the degree to which the air-fuel mixture becomes lean during acceleration operation and the degree to which the air-fuel mixture becomes rich during deceleration operation increase as the amount of deposit increases. In this case, for example, the degree to which the air-fuel mixture becomes lean during acceleration is greater (the more time it takes for the air-fuel mixture to become lean).

Therefore, calculate the time when the air-fuel mixture supplied into the engine cylinder becomes lean and rich during a certain period of time after acceleration operation starts, and use these lean and rich times to determine whether it is during acceleration operation or not. There is also a known fuel injection control device that corrects the acceleration increase value of the injected fuel so that the air-fuel mixture supplied into the engine cylinder has a target air-fuel ratio (see Japanese Patent Laid-Open No. 128944/1983).

[Problem to be solved by the invention]

By the way, when the engine temperature is low, the amount of liquid fuel adhering to the inner wall surface of the intake boat increases, and therefore the air-fuel mixture becomes much leaner during acceleration operation than when warm-up has been completed.

In addition, the warm-up state of the engine is generally judged based on the engine cooling water temperature, but even if the engine cooling water temperature reaches the water temperature during steady operation, the temperature of the engine intake system has not risen sufficiently. Even after it is determined that warm-up has been completed based on the cooling water temperature, there is a large amount of liquid fuel adhering to the inner wall surface of the intake boat, so the air-fuel mixture becomes significantly lean during acceleration operation.

That is, even if the increase rate of the fuel injection amount during acceleration operation is controlled based on the lean time during acceleration operation as in the above-mentioned fuel injection control device, the engine will not accelerate until a certain period of time has elapsed after warm-up is completed. There is a great danger that the air-fuel mixture will continue to become lean during operation.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, as shown in the block diagram of the invention in FIG. Based on the output signal of the fuel injection control means B that controls the fuel injection amount so that the supplied air-fuel mixture has the target air-fuel ratio, the acceleration operation state detection means C that detects the acceleration operation state, and the oxygen concentration detector 19. Find the time for the mixture to become lean and the time for it to become rich during acceleration, and if the time for the mixture to become lean is longer than the time for it to become rich, increase the correction coefficient for increasing the fuel injection amount during acceleration. An injection amount increasing means for increasing the fuel injection amount, a storage means E for continuing to store the above-mentioned increase correction coefficient even when the engine is stopped, a warming-up completion detecting means F for detecting the completion of warm-up of the engine, and a warming-up completion detecting means F for detecting the completion of warm-up of the engine. It further includes an increase correction coefficient control means G that makes the increase correction coefficient larger than the increase correction coefficient stored in the storage means until a predetermined period has elapsed after the warm-up is completed.

[For production]

After starting the engine, until a certain period of time has elapsed after warm-up is completed, the amount of injected fuel will be increased to a larger amount than during acceleration when warm-up is completed, so the air-fuel mixture may become lean during acceleration. There is no.

〔Example〕

Referring to Figure 2, 1 is the engine body, 2 is the piston, and 3
is the cylinder head, 4 is the piston 2 and cylinder head 3
A combustion chamber is formed in between, 5 is a spark plug, 6 is an intake valve, 7 is an intake boat, 8 is an exhaust valve, and 9 is an exhaust port.
Each intake boat 7 is connected to a surge tank 11 via a corresponding branch pipe 10, and a fuel injection valve 12 for injecting fuel into the corresponding intake boat 7 is attached to each branch pipe 10. Fuel injection from each fuel injection valve 12 is controlled based on an output signal from an electronic control unit 1-30.

The surge tank 11 is connected to an air cleaner 14 via an intake duct 13, and a throttle valve 1 is installed in the intake duct 13.
5 is placed. A bypass passage 16 that bypasses the throttle valve 15 is connected to the intake duct 13, and a bypass air amount control valve 17 is disposed within the bypass passage I6. Each exhaust port 9 is connected to an exhaust manifold 18, and an Ox sensor 19 is installed within the exhaust manifold 18.

The electronic control unit) 30 consists of a digital computer with ROMs interconnected by a bidirectional bus 31.
(read only memory) 32, RAM (random access memory) 33, CPU (microprocessor) 3
4, an input port 35 and an output port 36.

The CPU 34 has a backup RA via the bus 31a.
M33a is connected.

A water temperature sensor 20 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine body l.
The output voltage is input to the input port 35 via the AD converter 37. Further, the output voltage of the Ox sensor 19 is inputted to the input boat 35 via the AD converter 38 . An absolute pressure sensor 21 that generates an output voltage proportional to the absolute pressure inside the surge tank 11 is attached to the surge tank 11, and the output voltage of the absolute pressure sensor 21 is inputted to the input port 35 via the AD converter 39. Ru. A throttle switch 22 is attached to the throttle valve 15 to detect that the throttle valve 15 is in the fully closed position, and the output signal of the throttle switch 22 is manually input to the human-powered boat 35. An output pulse is generated every time the crank angle rotates, and the rotation speed sensor 23
The output pulses of are input to the input port 35. The CPU 34 calculates the engine speed from this output pulse. Furthermore, the starter switch 24 is connected to the input boat 35. On the other hand, the output port 36 is connected to the corresponding drive circuit 4
0.41 to the fuel injection valve 12 and the bypass air amount control valve 17. The bypass air amount control valve 17 is provided to control the engine idling speed, and during engine idling operation, the bypass air amount control valve 17 controls the inside of the bypass passage 16 so that the engine idling speed becomes the target speed. The amount of bypass air flowing is controlled.

On the other hand, the fuel injection time TAU of the fuel injection valve 12 is calculated based on the following equation.

TAU = (TP+K −TPAEW)・FAF −
F...(1) Here, TP: Basic fuel injection time TPAEW: Corrected fuel injection time during transition, that is, acceleration/deceleration: Corrected fuel injection time due to deposit accumulation TPAR
- Correction coefficient FAF: Feedback correction coefficient F: Correction coefficient determined by intake temperature, engine cooling water temperature, etc. Basic fuel injection time TP is the absolute pressure P in the surge tank 11
Calculated from M and engine speed NE. The relationship between the basic fuel injection time TP, absolute pressure PM, and engine speed NE is the basic fuel injection time TP from the fuel injection valve I2 during steady operation.
It has been determined in advance through experiments that the air-fuel mixture supplied into the engine cylinder when the fuel is injected has a target air-fuel ratio, for example, the stoichiometric air-fuel ratio, and this relationship is stored in the ROM 32.
stored within. Therefore, when steady operation is being carried out, ROM is calculated from absolute pressure PM and engine speed NE.
Basically, if fuel is injected from the fuel injection valve 12 for the basic fuel injection time TP calculated based on the relationship stored in 32, the air-fuel mixture supplied into the engine cylinder will basically have a target air-fuel ratio. If a 02 sensor capable of detecting an arbitrary air-fuel ratio is used as the 0□ sensor 19, the target air-fuel ratio can be set arbitrarily, but in order to easily understand the present invention, the following description will be made.
A case where the target air-fuel ratio is set to the stoichiometric air-fuel ratio will be explained. In this case, if fuel is injected from the fuel injection valve 12 for the basic fuel injection time TP, basically the air-fuel mixture supplied into the engine cylinder will have approximately the stoichiometric air-fuel ratio.

When not in a transient operating state, that is, during steady operation, the corrected fuel injection time TPAE- becomes zero. Therefore, in this case, the above-mentioned equation (1) is expressed as the following equation.

TAU=TP-FAF-F・
(2) That is, at this time, the fuel injection time TAU is the basic fuel injection time TP, the feedback correction coefficient FAF,
It is determined by the correction coefficient F. The correction coefficient F is determined by the intake air temperature, engine cooling water temperature, etc., and for example, it will be a value larger than 1.0 before warm-up is completed when the engine cooling water temperature is low, and it will be a value close to 1.0 or 1.0 after warm-up is completed. become. The feedback correction coefficient FAF changes based on the output signal of the Ot sensor 19 so that the air-fuel mixture supplied into the engine cylinder has a stoichiometric air-fuel ratio. Next, this feedback correction coefficient FAF will be explained.

0□Sensor 19 detects 0.1 when the air-fuel mixture supplied into the engine cylinder is larger than the stoichiometric air-fuel ratio, that is, when it is lean.
It generates an output voltage of about 0.9 volts when the air-fuel ratio is smaller than the stoichiometric air-fuel ratio, that is, when it is rich. Therefore, it can be determined from the output signal of the 02 sensor 19 whether the air-fuel mixture supplied into the engine cylinder is lean or rich. FIG. 3 shows a routine for calculating the feedback correction coefficient FAF from the output signal of the Ot sensor 19. Referring to FIG. 3, first, in step 100, it is determined whether or not the air-fuel ratio feedback control condition is satisfied. is determined to have been established. If the feedback control condition is not satisfied, the process proceeds to step 101, where the feedback correction coefficient FAF is set to 1.0. Therefore, during steady operation where the feedback control conditions are not satisfied, the fuel injection time T is calculated based on the following formula.
AU is calculated.

TAU=TP -F On the other hand, when it is determined that the feedback control condition is satisfied, the process proceeds to step 102 and determines whether the air-fuel mixture supplied into the engine cylinder is rich based on the output signal of the 0□ sensor 19. is determined.

Assuming that it was rich in the previous processing cycle and changed to rich in the current processing cycle, step 103
In step 104, it is determined whether the flag CAFR, which is reset when the fuel changes from rich to lean, has been reset. When the change from lean to rich occurs, the flag CAFR is reset, so step 105
Then, a predetermined skip value Rs is subtracted from the feedback correction coefficient FAF. Then step 10
At 6, the flag CAPR is set. Therefore, in the next processing cycle, the process proceeds from step 104 to step 107, where a predetermined constant value Ki (Ki (Rs)) is subtracted from the feedback correction coefficient FAF.

On the other hand, when the condition changes from rich to lean, the process proceeds from step 102 to step 108 where the flag CAFR is reset, and then the process proceeds to step 109 where it is determined whether or not the flag CAFL has been reset.

At this time, since the flag CAFL has been reset, the process proceeds to step 110, where the skip value Rs is added to the feedback correction coefficient FAF, and then, in step 111, the flag CAPL is set. Therefore, in the next processing cycle, the process proceeds from step 109 to step 112, where the constant value Ki is added to the feedback correction coefficient FAF. Therefore, the feedback correction coefficient FAF changes as shown in FIG.

If it becomes rich, the feedback correction coefficient FAF is decreased and the fuel injection time TAU is shortened, and if it is lean, the feedback correction coefficient FAF is increased and the fuel injection time TAU is lengthened. The air-fuel mixture supplied to the engine will be controlled to a stoichiometric air-fuel ratio.

In this way, if the engine is in a steady operating state and feedback control is being performed, the air-fuel mixture supplied into the engine cylinders is controlled to the stoichiometric air-fuel ratio. However, when calculating the fuel injection time TAU based on equation (2) above, even if feedback control is performed during transient operating conditions such as acceleration and deceleration, deposits will still accumulate on the inner wall surface of the intake boat. Even if this is not done, the air-fuel mixture supplied into the engine cylinders will deviate from the stoichiometric air-fuel ratio. That is, the air-fuel mixture becomes temporarily lean during acceleration, and the air-fuel mixture temporarily becomes rich during deceleration.

The difference in air-fuel ratio during such transient operating conditions is due to the time delay from the start of calculating the fuel injection time TAU until the actual fuel injection, and the fact that liquid injected fuel adhering to the inner wall of the intake boat may This is due to a time delay before the fluid flows into the cylinder, and therefore, these time delays during accelerated operation will first be explained with reference to FIGS. 5 and 6.

FIG. 5 shows the deviation in the air-fuel ratio due to the time delay from the start of calculation of the fuel injection time TAU until the actual fuel injection. As shown in FIG. 5, when acceleration operation is performed and the absolute pressure PM in the surge tank 11 rises from PM to PM, the basic value calculated from the absolute pressure PM and the engine speed NB is calculated accordingly. Fuel injection time T
P also increases. Fuel injection time TAU at current time
If the calculation of is started, the absolute pressure PM at this time is P
M, so the basic fuel injection time TP is calculated based on this absolute pressure PM, and the basic fuel injection time TP at this time is
Let be TP. By the way, calculation of the normal fuel injection time TAU is started at a predetermined crank angle, and then actual fuel injection is started after a certain crank angle. That is,
In FIG. 5, when calculation of the fuel injection time TAU is started at time L1, actual fuel injection is started at time . However, at time Lh, the absolute pressure PM becomes PM,
PM is higher than TP, and the basic fuel injection time required to bring the air-fuel mixture to the stoichiometric air-fuel ratio is TP, which is longer than TP. Nevertheless, at time th, fuel injection is performed only for the time calculated based on the basic fuel injection time TP, so the injected fuel is less than the amount of injected fuel required to bring the air-fuel mixture to the stoichiometric air-fuel ratio. , thus the mixture becomes lean. That is, actually the broken line W
Since the basic fuel injection time TP changes along the line W, the air-fuel mixture becomes lean as shown by Yl during the period shown by the broken line W.

On the other hand, FIG. 6 shows the deviation in the air-fuel ratio due to the time delay until the liquid injected fuel adhering to the inner wall surface of the intake boat flows into the engine cylinder. Note that FIG. 6 also shows a case where the absolute pressure PM in the surge tank 11 increases from PM to PM.

In FIG. 6, curves TPc and TP4 show changes in the basic fuel injection time TP, and are hatched Xa.

xb indicates the amount of liquid fuel flowing into the engine cylinder.0 The amount of liquid fuel flowing into the engine cylinder depends on the amount of injected fuel, that is, the amount of fuel attached to the inner wall surface of the intake boat, etc. As the fuel injection amount increases, the amount of liquid fuel that flows into the engine cylinder increases.0 When the engine is in steady operation, the amount of liquid fuel is almost constant; The amount of this liquid fuel increases as the engine load increases. Xa in Fig. 6 indicates the case where it is assumed that the same amount of liquid fuel is supplied into the engine cylinders as during steady operation for each absolute pressure PM. The air-fuel mixture supplied into the tank is maintained at a stoichiometric air-fuel ratio. However, in reality, when acceleration is being performed, even if the amount of fuel adhering to the inner wall surface of the intake boat increases, all the adhering fuel does not immediately flow into the engine cylinder. The amount of fuel will be less than in the case indicated by Xa. As the amount of adhering fuel increases, the amount of liquid fuel flowing into the engine cylinder gradually increases, and after acceleration operation is completed, this amount of liquid fuel becomes equal to the amount of liquid fuel during steady operation. xb in FIG. 6 indicates the amount of liquid fuel actually flowing into the engine cylinder. Therefore, between the start of acceleration operation and completion of acceleration, the liquid fuel 1xb flowing into the engine cylinder is smaller than the liquid fuel 1Xa during steady operation, so the air-fuel mixture becomes lean as shown by Y2. becomes.

Therefore, during acceleration operation, as shown by Y in Fig. 7, Yi
The lean shown by is overlapping with the lean shown by Yt. Therefore, as shown in Fig. 7, the amount of fuel is increased by IctΔPH・C4 corresponding to Yl during acceleration operation,
Quantity C1 (ΔPM + C1ΣΔPM) corresponding to Y2
If the amount of fuel is increased by C4, the air-fuel mixture will be maintained at approximately the stoichiometric air-fuel ratio as shown by Z. Here, ΔPM is the rate of change of the absolute pressure PM, and C4 is a coefficient for converting the absolute pressure into time.

That is, in FIG. 5, the basic fuel injection time TP is insufficient!
(TPb TP,) is the time, ΔPM-Ca at
is approximately equal to the product of time (tb - ta), and if time (t, -ta) is expressed as 02, the shortfall in the basic fuel injection time TP will be expressed as C2ΔPM·C4. Note that since the time (11°1,) corresponds to the crank angle, 62 is a function of the engine speed NE.

On the other hand, the curve corresponding to the curve shown in Y2 is CS (Δ
PM+C1ΣΔPM) - Can be expressed as C4. Here, C3 is called an attenuation coefficient and has a value smaller than 1.0. That is, Cff (ΔPM+C+ΣΔPM
)・C4 is calculated when calculating the fuel injection time TAU, and is CS (ΔPM+C1ΣΔPM)・The value of C4 increases rapidly when ΔPM is a large value, and slowly decreases when ΔPM becomes a small value. When the engine temperature and the intake air temperature decrease, the amount of liquid fuel adhering to the inner wall surface of the intake boat increases, and the mixture becomes leaner. Therefore, C1 is a function of engine temperature and intake air temperature.

Therefore, during acceleration operation, 02Δr'M・C4 and C1(ΔPM
-C1ΣΔPM) - By increasing the amount of fuel to which C6 is added, the air-fuel mixture can be maintained at the stoichiometric air-fuel ratio. This added value becomes the corrected fuel injection time TPA[W during the transient period in the above-mentioned equation (1). That is, TPAE- is expressed by the following formula.

TPAEW= (ctΔPM+C3(ΔPM+C+ΣΔ
PM)) Cm... (3) The rich state during deceleration operation is also as shown in Y, Y, in Figures 5 and 6, so if TPAE- in equation (3) above is used, the same result can be obtained. The air-fuel mixture supplied into the engine cylinders is maintained at the stoichiometric air-fuel ratio. However, during deceleration operation, ΔPM becomes negative, so TPAEI ( becomes negative.

Therefore, when deposits are not attached to the inner wall surface of the intake boat, etc., by calculating the fuel injection time TAU based on the following equation, the air-fuel mixture can be maintained at the stoichiometric air-fuel ratio regardless of the operating state of the engine.

TAU= (TP+TPAEW) ・FAF −F
-(4) However, if the engine is used for a long time and deposits adhere to the inner wall of the intake boat, the deposits have the property of retaining liquid fuel, so the liquid fuel that adheres to the inner wall of the intake boat, etc. Moreover, it takes time for the liquid fuel adhering to the inner wall surface of the intake boat to flow into the engine cylinder after it adheres. Therefore, when the deposit adheres to the inner wall surface of the intake boat, etc., using equation (4) above, during acceleration operation, the deposit delays the inflow of liquid fuel into the engine cylinder, resulting in a lean mixture, whereas during deceleration operation, the deposit will cause the mixture to become lean. Since the amount of liquid fuel adhering to the inner wall surface of the intake boat increases, the air-fuel mixture becomes rich. Therefore, if a deposit is attached, the correction coefficient K is adjusted to the correction injection time TPAIE1.
This correction coefficient K is used to correct the increase or decrease in fuel during acceleration/deceleration operation, so that the air-fuel mixture is maintained at the stoichiometric air-fuel ratio regardless of the operating state of the engine. In this case, as shown in (1) 2 above, the fuel injection time TAU is calculated by the following formula.

TAIJ = (TP+K I TPAEW)・FAP
-F, that is, when there is no deposit attached and therefore the air-fuel mixture supplied into the engine cylinder is maintained at approximately the stoichiometric air-fuel ratio even during acceleration operation, the acceleration operation is performed as shown in Figure 8 (A). After the start of the lean and rich cycles, the lean and rich cycles are repeated alternately at almost the same period, so the lean time and rich time do not differ much. However, when a deposit is deposited, the acceleration operation occurs as shown in Figure 8 (B). Sometimes the mixture becomes lean temporarily. If the air-fuel mixture becomes lean temporarily during acceleration operation, the air-fuel mixture shown in Figure 8 (
As shown in B), the lean time after acceleration operation is started is longer than the rich time. On the other hand, if the air-fuel mixture temporarily becomes rich during acceleration operation, the rich time after acceleration operation is started becomes longer than the lean time.

Therefore, by comparing the lean time and the rich time, it is possible to determine whether the air-fuel mixture is temporarily lean or rich. Therefore, roughly speaking, if the lean time becomes longer than the rich time during acceleration operation, the value of the correction coefficient is increased to increase the acceleration fuel increase rate, and the lean time becomes longer than the rich time. If it becomes shorter than that, the value of the correction coefficient is decreased and the acceleration fuel increase rate is decreased. On the other hand, if the rich time becomes longer than the lean time during deceleration operation, the value of the correction coefficient is increased and the deceleration fuel reduction rate increases, causing the rich time to become less than the lean time. If it is short, the value of the correction coefficient is decreased and the deceleration fuel reduction rate is decreased.

However, as mentioned above, the temperature of the engine intake system is low until a certain period of time has passed after warm-up is completed after the engine starts, and therefore, there is a large amount of liquid fuel adhering to the inner wall surface of the intake boat, so during acceleration operation, the temperature of the engine intake system is low. Become lean in the Big 11. In this case, the lean time becomes longer, so as mentioned above, the value of the correction coefficient is increased and the acceleration fuel increase rate is increased, but in order to ensure a stable change in the correction coefficient, this acceleration fuel increase is necessary. It is not possible to increase the amount of increase in the ratio so much, and therefore the air-fuel mixture will become as lean as 11 during the next acceleration operation. Until then, the acceleration fuel increase rate is greatly increased by adding the experimentally determined value to the original correction coefficient K.

Next, with reference to the time chart shown in FIG. 9 and the flowcharts shown in FIGS. 10 and 11, the calculation routine for the correction coefficient, that is, the calculation routine for the deposit learning value will be explained. Note that this routine is executed by an interrupt every 360 crank angles.

10 and 11, first, in step 200, the current absolute pressure PM in the surge tank 11 detected by the absolute pressure sensor 21 is changed to the absolute pressure in the surge tank 11 detected in the previous processing cycle. PM,
is subtracted, and the result of the subtraction is taken as the absolute pressure change rate ΔPM. Next, in step 201, it is determined whether feedback control based on the output signal of the 02 sensor 19 is being performed. If feedback control is not being performed, the process advances to step 202 to control each counter CAC.

CLRN 1 and CLRN 2 are cleared to 0. Then, when feedback control is started, the process proceeds to step 203, where it is determined whether or not the counter CLRN 1 has been cleared. At this time, since the counter CLRN1 has been cleared, the process advances to step 204, and the counter CLRN1 is cleared.
It is determined whether or not 2 is cleared. At this time, since the counter CLRN2 is cleared, the process proceeds to step 205. In step 205, it is determined whether ΔPM is larger than a certain value, for example, 39 msHg, that is, whether or not it is during acceleration operation. If ΔPM<39rusHg, it is determined that the vehicle is not in acceleration mode, and the process proceeds to step 206. In step 206, ΔPM is a constant value, for example -3
It is determined whether or not it is smaller than 9++siHg, that is, whether or not it is during deceleration operation. If ΔPM<39mm11g, it is determined that the operation is not decelerating, and the process proceeds to step 202, where each counter CAC, CLRN 1 is set.

CLRN2 is cleared.

On the other hand, in step 205 ΔPM2:39saHg
In other words, when it is determined that the vehicle is in acceleration operation, the process proceeds to step 207, where the count value of the counter CLRN1 is set to 1. Next, the routine proceeds to a fuel injection time calculation routine. In the next processing cycle, the process proceeds from step 203 to step 208. In step 208, ΔPM is equal to 5.
It is determined whether or not it has become lower than snHg, that is, whether or not it has been decelerated after the start of acceleration operation, and ΔPM<-5mm11g
In this case, the process advances to step 202 and each counter CAC,
CLRN1 and CLRN2 are cleared. On the other hand, when acceleration operation continues, ΔP M
> -5s+m11g, so the process advances from step 208 to step 209, where the counter CLRN1 is incremented by 1. That is, as shown in FIG. 9(A), the acceleration operation is started and the absolute pressure P in the surge tank 11 is increased.
M increases from PM to PMt, and at this time ΔPM becomes 39
If it exceeds msHg, the counter CLRN1 starts counting up.

Next, in step 210, it is determined whether the count value of the counter CLRN1 has become larger than a predetermined constant value A1. When CLRNI<A l, proceed to the fuel injection time calculation routine; on the other hand, when CLRNI≧A
When it becomes 1, the process proceeds to step 211, where it is determined from the output signal of the 02 sensor 19 whether or not the air-fuel mixture supplied into the engine cylinder is lean. If the air-fuel mixture is lean, the process proceeds to step 212 where the counter CAC is incremented by 1, and then the process proceeds to step 213. On the other hand, if the air-fuel mixture is not lean, that is, if the air-fuel mixture is rich, the process proceeds to step 214 where the counter CAC is decremented by 1, and then the process proceeds to step 213. In step 213, it is determined whether the counter CLRN1 has become larger than a predetermined constant value Bl.

If CLRNI<Bl, the routine proceeds to a fuel injection time calculation routine. That is, as shown in FIG. 9(A), until the count value of counter CLRN1 changes from AI to Bl, it is determined whether the air-fuel mixture is lean or rich, and the air-fuel mixture is lean. Sometimes the counter CAC is counted up, and when the air-fuel mixture is rich, the counter CAC is counted down. Therefore, counter C
If the time when the count value of LRN 1 is lean from A1 to F31 is longer than the time when it is rich, the count value of counter CAC increases, and the time when it is rich is increased. If the time is longer than the lean time, the count value of the counter CAC decreases. Therefore, whether the air-fuel mixture is lean or rich during acceleration operation can be determined from the count value of the counter CAC when CLRN1 becomes Bl.

In this way, in the embodiment shown in FIG.
It is determined whether the air-fuel mixture is lean or rich until the count value of counter CLRN1 reaches AI from AI.
The period from 1 to 81 is the lean/rich judgment period. Next, this lean/rich judgment period will be explained with reference to (C) to (H) of FIG. 8. In addition, the 8th
In Figures (C) to (H), this lean/rich judgment period is indicated by L' or 11.

Figure 8 (C), (D), and (E) show 0□ when accelerating operation is performed when no deposit is attached.
It shows the behavior of the change in the output voltage of the sensor 19 and the count value of the counter CAC. In this case, Fig. 8(C), (
As shown in Figures 8(C) and 8(E), lean and rich cycles are repeated at almost the same cycle even during accelerated operation, and the lean/rich judgment period is as shown in Figure 8(C) and (D). The cycle is set to be lean or rich in such a state. In other words, counter CL
Setting value A1 for RN1. B1 is determined so that the period until the count value reaches 81 from AI is approximately equal to the lean or rich period.

When the lean-rich judgment period is determined in this way, as shown in Figure 8 (C) and (D), if no deposit is attached, the lean time and rich time within the lean-rich judgment period are determined. are almost equal, so the counter C when the lean/rich judgment period has elapsed
The AC count value becomes almost zero. On the other hand, as shown in FIG. 8(E), if the lean-rich judgment period L' is one and a half cycles of lean or rich fluctuations, the lean time within the lean-rich judgment period L' is the rich time. In this way, the count value of the counter CAC becomes a large value when the lean-rich judgment period L' has elapsed. Therefore, in the case shown in FIG. 8(E), the lean-rich judgment period If it is determined that the air-fuel mixture is lean during acceleration operation when the count value of the counter CAC exceeds Ct when L' has elapsed, this will clearly result in an erroneous determination. Therefore, in order to avoid such misjudgment, Fig. 8 (C),
As shown in (D), the lean/rich judgment period needs to be approximately one cycle of lean or rich.

As mentioned above, during the lean/rich judgment period, the counter C
This corresponds to the period from when the count value of LRN 1 reaches Bl from At. By the way, fuel injection is usually started at a predetermined crank angle;
The routine shown in Figure 1 is executed by an interrupt every 360 crank angles, so fuel injection is performed a fixed number of times regardless of the engine speed until the count value of the counter CLRNl reaches 81 from A1. . In other words, during the lean/rich determination period, fuel injection is performed a fixed number of times regardless of the engine speed.

Incidentally, the air-fuel ratio changes for each fuel injection, and feedback control is performed with respect to this air-fuel ratio change, so the lean/rich period depends on the number of fuel injections.

Therefore, regardless of the engine speed, that is, regardless of the degree of acceleration, the lean/rich determination period will approximately match the lean or rich period.

On the other hand, if the deposit is attached, the mixture will be lean when acceleration starts, and therefore Fig. 8 (F), (G)
As shown in Figure 8 (C) and (D), the lean time is
It will be longer than . Therefore, the lean time within the lean-rich judgment period is longer than the rich time, and when the lean-rich judgment period elapses, the counter CAC
The count value of increases. Therefore, since the count value of the counter CAC exceeds Ct, it can be determined that the air-fuel mixture has become lean during acceleration operation. As shown in Fig. 8 (F), CG), when the rich judgment period has elapsed, it becomes rich, and this rich time is determined by the control system of the fuel injection system. It may be short as shown in FIG. 8(G), or it may be long as shown in FIG. 8(G). However, if the lean/rich judgment period is made to roughly match the lean or rich cycle when no deposit is attached, the lean/rich judgment period has elapsed in Figures 8 (F) and (G). Regardless of the length of the rich time, it is possible to reliably determine leanness due to deposit adhesion.

Furthermore, depending on the fuel injection system, if the rich time is short after the lean/rich judgment period has elapsed as shown in Fig. 8 (F), deposits may be deposited as shown in Fig. 8 (H). The lean/rich judgment period 1. is an integral multiple of the lean or rich cycle during acceleration operation when the engine is not running, for example 2 cycles. It can be IP.

In addition, the lean operation is continued until the counter CLRN1 reaches A1.
The reason why a rich determination is not made is that it takes a certain amount of time for the air-fuel mixture supplied into the engine cylinder to turn into exhaust gas and reach the Ot sensor 19.

If it is determined in step 213 that CLRN 1≧81, the process proceeds to step 215, where it is determined whether the count value of the counter CAC is larger than a predetermined positive constant value C1. Step 2 for CACiCl
The process proceeds to step 16, where it is determined whether the count value of the counter CAC is smaller than a predetermined negative constant value DI.

If CAC>DI, the process advances to step 202 and each counter CAC and CLRN 1 are counted.

CLRN 2 is cleared. On the other hand, step 2
When it is determined that CAC≧01 in step 15, that is, when the lean state is reached during acceleration operation, step 2 is performed.
17, a predetermined constant value, for example 0.1, is added to the acceleration correction coefficient KAC, and thus the acceleration correction coefficient K
AC is increased.

On the other hand, when it is determined in step 216 that CAC<Dl, that is, when the engine is rich during acceleration operation, the process proceeds to step 218, where a predetermined constant value, for example 0.1, is subtracted from the acceleration correction coefficient KAC. , thus the acceleration correction coefficient KAC is reduced.

On the other hand, in step 206 ΔPMs-39msHg
In other words, when it is determined that the vehicle is in deceleration operation, the process proceeds to step 219, where the count value of the counter CLRN2 is set to 1. Next, in the 0th order processing cycle, which proceeds to the fuel injection time calculation routine, the process proceeds from step 204 to step 220. In step 220, ΔPM is 5.
It is determined whether or not it has become higher than s+geHg, that is, whether or not it has been accelerated after the start of deceleration operation, and ΔPM≧5+s■H
In the case of g, the process advances to step 202 and each counter CAC
, CLRN 1 and CLRN 2 are cleared.

On the other hand, when deceleration operation continues, ΔP
Since M<5, the process advances from step 220 to step 221, where the counter CLRN2 is incremented by one. That is, as shown in FIG. 9(B), deceleration operation is started and the absolute pressure PM in the surge tank 11 is increased to P.
M, decreases from PM, and at this time, ΔPM is -39 mm
Hg (if it is, the counter CLRN2 starts counting up.

Next, in step 222, it is determined whether the count value of the counter CLRN2 has become larger than a predetermined constant value A2. CLl? When N2<A2, the routine proceeds to a fuel injection time calculation routine. On the other hand, C.L.R.
When N2≧A2, the process proceeds to step 223, where it is determined from the output signal of the 0□ sensor 19 whether or not the air-fuel mixture supplied into the engine cylinder is rich.

If the air-fuel mixture is rich, the process proceeds to step 224 where the counter CAC is incremented by 1, and then the process proceeds to step 225. On the other hand, if the air-fuel mixture is not rich, that is, if the air-fuel mixture is full, the process proceeds to step 226 where the counter CAC is decremented by 1, and then the process proceeds to step 225. In step 225, the counter CLR
It is determined whether N2 has become larger than a predetermined constant value B2.

If CLRN2 < 82, the routine proceeds to a fuel injection time calculation routine. That is, as shown in FIG. 9 (CB), until the count value of the counter CLRN2 reaches from A2 to 82, it is determined whether the air-fuel mixture is rich or full, and the air-fuel mixture is rich. Sometimes counter CAC
is counted up, and when the air-fuel mixture is lean, the counter CAC is counted down. Therefore, if the time during which the count value of counter CLRN 2 is rich from A2 to 82 is longer than the time when it is lean, the count value of counter CAC increases, and the time when it is lean is increased. If the time is longer than the rich time, the count value of the counter CAC decreases. Therefore, whether the air-fuel mixture is rich or lean during deceleration operation can be determined from the count value of the counter CAC when CLRN2 reaches 82.

If it is determined in step 225 that it is the CLRN2 pin 82, the process proceeds to step 227, where it is determined whether the count value of the counter CAC is larger than a predetermined positive constant value C2. If CAC,<C2, step 2
Proceeding to step 28, it is determined whether the count value of the counter CAC is smaller than a predetermined negative constant value D2.

If CAC>D2, the process advances to step 202 and each counter CAC and CLRN 1 are counted.

CLRN 2 is cleared. On the other hand, step 2
When it is determined in step 27 that CAC≧02, that is, when the engine is rich during deceleration operation, step 2
29, a predetermined constant value, for example 0.1, is added to the deceleration correction coefficient KDC, and thus the deceleration correction coefficient K
DC is increased.

On the other hand, when it is determined in step 228 that CAC≦D2, that is, when the lean state is achieved during deceleration operation, the process proceeds to step 230, where a predetermined constant value, for example 0.1, is subtracted from the deceleration correction coefficient KDC. , thus the deceleration correction coefficient KDC is reduced.

The acceleration correction coefficient KAC and the deceleration correction coefficient KDC represent the correction coefficient K for the corrected fuel injection time TPAEW due to the accumulation of deposits. Therefore, if the accelerating operation becomes lean due to the accumulation of deposits, the correction coefficient K is increased, and the Accumulation causes damage during deceleration operation.
When Sochi arrives, the correction coefficient K is similarly increased.

FIG. 12 shows a fuel injection time calculation routine executed subsequent to the routines shown in FIGS. 10 and 11.

Referring to FIG. 12, first, in step 300, the basic fuel injection time TP is calculated from the output signals of the absolute pressure sensor 21 and the rotation speed sensor 23.Next, in step 301, ΣΔPM is calculated based on the following equation.

ΣΔPM=ΔPM+C, ΣΔM...(
5) Next, in step 302, the corrected fuel injection time TPAE- is calculated based on the following equation.

TPABW= (CzΔPM+C, ΣΔPM)・C4・
...(6) Combining the above equations (5) and (6) gives the following equation.

TPA lung = (C2ΔPM+C, (ΔPM+C, ΣΔPM
)) C4 This equation represents the above-mentioned equation (3). Therefore, the corrected fuel injection time T P A F, W is used to maintain the air-fuel mixture at the stoichiometric air-fuel ratio during transient operation when deposits are not accumulated. It represents the increase/decrease in the amount of injected fuel.

Next, in step 303, it is determined whether ΔPM is positive or zero. When it is determined in step 303 that ΔPM>0, that is, when the accelerating state or Δ
When PM=O, the process proceeds to step 304 where the acceleration correction coefficient KAC is set as the correction coefficient, and then the process proceeds to step 306. On the other hand, when it is determined in step 303 that ΔPM<O, that is, when the vehicle is in a deceleration state, the process proceeds to step 305 where the deceleration correction coefficient KDC is set as the correction coefficient, and then the process proceeds to step 306.

In step 306, it is determined whether a flag indicating that the engine cooling water temperature at the time of engine startup is below a predetermined constant temperature is set. Next, this flag will be explained first with reference to FIG. FIG. 13 shows a routine executed when the starter switch 24 is turned on, that is, when the engine is started. Referring to FIG. 13, first, in step 400, the water temperature sensor 2 is
From the output signal of 0, it is determined whether the engine cooling water temperature T is lower than a predetermined constant value, for example, 50°C. T
<If the temperature is 50°C, the process proceeds to step 401 and a flag is set.

Returning to FIG. 12 again, if it is determined in step 306 that the flag is not set, that is, if the engine cooling water temperature T is 50° C. or higher when the engine is started, the process jumps to step 308. In step 308, fuel injection time TAU is calculated based on the following equation.

TAU・(TP 10K・TPAE oath)・FAF-F In this case, when the accelerating operation becomes lean due to deposit accumulation, the correction coefficient K is increased, so the next accelerating operation will be K・↑PAEW, that is, acceleration fuel increase rate. is increased, thereby maintaining the mixture at the stoichiometric air/fuel ratio. On the other hand, when the fuel becomes rich during deceleration due to deposit accumulation, the correction coefficient K is increased, so that -TPABW, that is, the deceleration fuel reduction rate increases during the next deceleration, thereby maintaining the air-fuel mixture at the stoichiometric air-fuel ratio. be done. In this way, even if deposits adhere to the inner wall surface of the intake boat, the air-fuel mixture can be maintained at the stoichiometric air-fuel ratio regardless of the operating state of the engine.

Note that the acceleration correction coefficient KAC and the deceleration correction coefficient KDC are stored in the backup RAM 33a, so these K
AC and DC are memorized even if the engine is stopped.

On the other hand, when it is determined that the flag is set in step 306 of FIG. A coefficient K is calculated.

K = +24・(1-CT/250)・
(7) Here, CT represents a count value, and 2 OCT is calculated by the routine shown in FIG.

Therefore, next, the routine shown in FIG. 14 will be explained.

The routine shown in FIG. 14 is executed by interruption at regular intervals, for example every second.

Referring to FIG. 14, first, in step 500, it is determined whether the engine cooling water temperature T detected by the output signal of the water temperature sensor 20 has become higher than a predetermined constant temperature, for example, 80°C. This temperature of 80°C is the temperature at which warm-up is normally determined to have been completed. When T>80° C., the process proceeds to step 501, where it is determined whether the count value CT has reached the upper limit value 250 or not. When CT<250, the process proceeds to step 502, where the count value CT is incremented by one. Therefore, when T>80°C, the count value CT is gradually increased to 250. Therefore, the correction coefficient determined by the above equation (7) changes as shown in FIG. That is, when T<80° C., CT=0, so the correction coefficient is +24, which is a constant value. Here, K in (K+24) is the acceleration correction coefficient AC and KDC when the engine was operated last time,
Therefore, the correction coefficient includes K when the engine was last operated.
AC is increased by 24 compared to DC. On the other hand, T
>80'C, the count value CT gradually increases to 250 (so the correction coefficient becomes gradually smaller and finally becomes KAC, then DC.

After the correction coefficient K is calculated in step 307, the fuel injection time TAU is calculated in step 308.

Therefore, during acceleration operation, it is possible to prevent the air-fuel mixture from becoming significantly leaner because TPAE- becomes larger than TPAE- after cooling down after completion of warm-up.

(Effects of the Invention) It is possible to prevent the air-fuel mixture from becoming significantly lean during acceleration operation until a certain period of time has elapsed after warm-up is completed after the engine is started.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the invention, Fig. 2 is a diagram showing the entire internal combustion engine, Fig. 3 is a flowchart for calculating the feedback correction coefficient, Fig. 4 is a diagram showing changes in the feedback correction coefficient, and Fig. 5 is a diagram showing the change in the feedback correction coefficient. The figure is a diagram to explain the deviation in the air-fuel ratio due to the time delay from the start of fuel injection time calculation until the actual fuel injection. Figure 6 shows the time until liquid fuel flows into the engine cylinder. Fig. 7 is a diagram to explain the amount of fuel injection that should be increased or decreased during acceleration/deceleration operation, and Fig. 8 is a diagram for explaining the amount of fuel injection that should be increased or decreased during acceleration/deceleration operation. Figure 9 is a time chart showing the method of calculating the deposit learning value, Figures 10 and 11 are flowcharts for calculating the deposit learning value, and Figure 12 is the calculation of the fuel injection time. 13 is a flowchart for setting a flag, FIG. 14 is a flowchart for controlling a counter, and FIG. 15 is a diagram showing changes in correction coefficients. 6...Intake valve, 8...Exhaust valve, 12...
Fuel injection valve, 15... Throttle valve, 19...
Ot sensor, 21... Absolute pressure sensor.

Claims (1)

[Claims] a fuel injection control means for controlling a fuel injection amount so that the air-fuel mixture supplied into the engine cylinder has a target air-fuel ratio based on an output signal of an oxygen concentration detector disposed in the engine exhaust passage; and an acceleration operating state. an acceleration operation state detection means for detecting the acceleration operation state, and a time when the mixture becomes lean during acceleration operation and a time when the mixture becomes rich based on the output signal of the oxygen concentration detector, and when the time when the mixture becomes lean is longer than the time when it becomes rich an injection amount increasing means for increasing the fuel injection amount during acceleration operation by increasing an increase correction coefficient for the fuel injection amount during acceleration operation; a storage means for continuing to store the increase correction coefficient even when the engine is stopped; a warm-up completion detection means for detecting the completion of warm-up; and a warm-up completion detection means for detecting the completion of warm-up; 1. A fuel injection control device for an internal combustion engine, comprising: increasing correction coefficient control means.