JPH0367043A - Control device for fuel injection amount of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent deterioration of the rate of fuel consumption and exhaust of a large quantity of detrimental components by increasing the initial value of the post-starting increment with the degree of leanness of the mixture gas under accelerative running, and increasing the damping rate of the post-starting increment with the leanness of mixture gas under accelerative operation. CONSTITUTION:On the basis of the output signal from an oxygen concentration sensor 19, an incremental rate calculating means D calculates the incremental rate of the fuel injection amount from the time, at which the mixture gas becomes lean under accelerative operation, and the time it becomes rich, and this rate is stored in a memory E. A fuel injection amount increasing means F increases the fuel injection amount by an incremental value of lessening gradually with the elapse of the time from completion of the start at a damping rate enlarging with increasing incremental rate according to the incremental rate from the initial value to be enlarged with increasing incremental rate according to the incremental rate stored in the memory E when the starting of the engine is completed. This prevents the air-fuel ratio in the later half of the post-start increment from becoming rich to a great extent, which should enhance the rate of fuel consumption and reduction of emission of the exhaust gas.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel injection amount 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 negative pressure and the engine speed, or from the intake air amount and the engine speed, and an oxygen concentration detector (hereinafter referred to as 02 sensor) installed in the engine exhaust passage is used. By correcting the basic fuel injection amount based on the output signal of the engine (referred to as the stoichiometric air-fuel ratio), feedbank control is performed so that the air-fuel mixture supplied into the engine cylinder reaches 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. Sometimes the amount of injected fuel is increased, and during deceleration operation the amount of injected fuel is m! I try to do that. 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 space 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 enter the intake boat. The contained carbon particles gradually accumulate on the back surface of the intake valve bulk 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 port, the amount of liquid fuel adhering to the inner wall surface of the intake port increases, and the inner wall surface of the intake boat increases. It takes time for the liquid fuel that has adhered to the engine cylinders to flow into the engine cylinders. Therefore, while the engine is relatively new, the air-fuel mixture supplied into the engine cylinders is controlled to approximately the stoichiometric air-fuel ratio regardless of the engine operating condition, but as the engine is used for a long period of time, deposits are deposited in the intake port. If the liquid fuel adheres to walls, etc., it takes time for the liquid fuel that adheres to the inner wall of the intake boat to flow into the engine cylinder after it adheres, so the air-fuel mixture supplied to the engine cylinder becomes lean during acceleration operation. Furthermore, since the amount of injected fuel that adheres to the inner wall surface of the intake boat increases, the air-fuel mixture supplied into the engine cylinders becomes richer 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 greater the degree of lean during acceleration, the longer the time for the mixture to become lean.

Additionally, the more the fuel used in the engine contains heavy components with low volatility, the worse the vaporization of the injected fuel will be, and the more liquid fuel will adhere to the inner wall of the intake port, the more the mixture will become lean during acceleration. The degree to which the air-fuel mixture becomes lean during deceleration increases, and the degree to which the air-fuel mixture becomes rich during deceleration increases. For example, the greater the degree to which the air-fuel mixture becomes lean during acceleration, the longer the amount of time the air-fuel mixture becomes lean.

Therefore, calculate the time during which the air-fuel mixture supplied into the engine cylinder becomes lean and rich during a certain period of time after the start of acceleration operation, and use these lean times and rich times to calculate the time during acceleration operation. There is a known fuel injection amount control device that corrects the acceleration increase value of the injected fuel so that the air-fuel mixture supplied into the engine cylinder has the target air-fuel ratio even when the fuel mixture is supplied into the engine cylinder. ).

When deposits form in this way, or when fuel containing many heavy components is used, the air-fuel mixture becomes lean during acceleration, but the air-fuel mixture also becomes lean when starting the engine and during a predetermined period after the engine has started. becomes lean. In other words, when starting the engine and during a predetermined period after the completion of engine starting, if deposits are deposited or if fuel containing a large amount of heavy components is used, a large amount of injected fuel will adhere to the inner wall surface of the intake boat, causing damage inside the engine cylinder. The air-fuel mixture supplied to the engine becomes significantly lean, making it difficult to start the engine, or even if the engine starts, its subsequent idling becomes unstable.

Therefore, the degree of mixture leanness during acceleration is detected from the amount of variation in the amount of feedback correction during a certain period of time after the start of acceleration. Fuel injection that increases the fuel injection amount at engine start and the initial value of the so-called post-start increase value, which is executed when engine start is completed, as the degree of lean of the air-fuel mixture increases. A quantity control device is known (see Japanese Patent Laid-Open No. 129435/1983).

[Problem to be solved by the invention]

By the way, the degree of air-fuel mixture supplied into the engine cylinder due to the accumulation of deposits or the use of fuel containing a large amount of heavy components during the engine start and a predetermined period after the engine start is completed is determined by the time elapsed since the engine start. For example, taking deposits as an example, the amount of liquid fuel held by these deposits increases with each fuel injection from engine startup, and as a result, the amount of fuel evaporation from the liquid fuel attached to the deposits increases. Since the degree of leanness of the air-fuel mixture supplied into the engine cylinders due to the buildup of deposits gradually increases, the degree of leanness of the air-fuel mixture supplied into the engine cylinders gradually decreases as time passes after the engine is started. Therefore, the increase in the amount of fuel injection due to the accumulation of deposits during the engine start and a predetermined period after the completion of the engine start, or due to the use of fuel containing a large amount of heavy components, must be reduced as time passes from the engine start. The larger the increase in fuel injection amount due to deposits or the use of fuel containing many heavy components, the more liquid fuel will adhere to the inner wall of the intake boat, and the amount of fuel evaporation from this liquid fuel will increase. Therefore, the rate of decrease in this increase must be increased.

However, as in the above-mentioned Japanese Patent Application Laid-Open No. 61-129435, if the initial value of the post-start fuel increase is simply increased as the degree of leanness of the air-fuel mixture during acceleration is increased upon completion of engine startup, deposits may be deposited in the latter half of the post-start fuel increase. , or due to the use of fuel containing many heavy components, the degree of leanness of the air-fuel mixture supplied into the engine cylinder is relatively small, but deposits are deposited during the first half of the fuel increase after startup, or the amount of heavy components is increased. A large amount of fuel is injected in proportion to the leanness of the air-fuel mixture supplied to the engine cylinder due to the use of the fuel contained in the engine, and as a result, the air-fuel ratio becomes significantly richer during this period, resulting in poor fuel efficiency. This causes the problem that a large amount of harmful components are discharged.

[Means to solve the problem]

In order to solve the above-mentioned problems, according to the present invention, as shown in the constituent countries of the invention in FIG. a fuel injection amount correction means B that corrects the fuel injection amount so that the air-fuel mixture supplied into the engine cylinder has a target air-fuel ratio based on the output signal of the oxygen concentration detector 19 disposed in the engine; Accelerated driving state detection means C to detect;
an increase ratio calculation means for calculating an increase ratio of the fuel injection amount from the time when the air-fuel mixture becomes lean and the time when it becomes rich during acceleration operation based on the output signal of the oxygen concentration detector 19; A storage means E for storing the calculated increase rate, and an increase rate according to the increase rate from an initial value that increases as the increase rate increases, according to the increase rate stored by the storage means E when engine starting is completed. The fuel injection amount increasing means F increases the fuel injection amount by an increase of 1 tfl, which is gradually decreased as time elapses from the completion of starting, with a damping rate that increases as .

[For production]

The initial value of the increase after starting increases as the degree of leanness of the air-fuel mixture during acceleration operation increases, and the attenuation rate of the increase after startup increases as the degree of leanness of the mixture after acceleration increases.

[Example] Referring to Fig. 2, 1 is the engine body, 2 is the piston, and 3 is the engine body.
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 boat.

Each intake boat 7 is connected to a surge tank 11 via a corresponding branch pipe IO, and a fuel injection valve 12 for injecting fuel into the corresponding intake boat 7 is attached to each branch pipe IO. Fuel injection from each fuel injection valve 12 is controlled based on an output signal from an electronic control unit 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 6 bypassing the throttle valve 15 is connected to the intake duct 13, and a bypass air amount control valve 17 driven by a step motor 17a is disposed within the bypass passage 16. Each exhaust port 9 is connected to an exhaust manifold 18, and an 08 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.

A bank-up RAM 33a is connected to the CP[I 34 via a bus 31a. A water temperature sensor 20 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine main body 1, and the output of this water temperature sensor 20 The voltage is supplied to the human powered boat 35 via the AD converter 37. Also, O
The output voltages of all f sensors 9 are input to the human powered 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 a fully closed position, and an output signal of the throttle switch 22 is input to an input port 35. The rotation speed sensor 23 generates an output pulse every time the crankshaft rotates by a predetermined crank angle, and the output pulse of the rotation speed sensor 23 is inputted to the input port 35 .

The CPU 34 calculates the engine speed from this output pulse. On the other hand, the output port 36 is connected to the fuel injection valve 12 and the step motor 17a of the bypass air amount control valve 17 via a corresponding drive circuit 40.41. The bypass air amount control valve 17 is provided to control the engine idling speed, and when the engine is idling, the bypass passage 1 is controlled by the bypass air amount control valve 17 so that the engine idling speed becomes the target speed.
6 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+-TPAEw)・FAF-FAS
E-F...(1) Here, TP: Basic fuel injection time TPAEW: Corrected fuel injection time during transition, that is, acceleration/deceleration K: Corrected fuel injection time TPAE- according to deposit accumulation and fuel properties Learning coefficient FAF: Feedback correction coefficient FASE: Post-start increase correction coefficient F: Correction coefficient determined by intake air temperature, engine cooling water temperature, etc. Basic fuel injection time TP is based on 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 target air-fuel mixture supplied into the engine cylinder when fuel is injected from the fuel injection valve 12 for the basic fuel injection time TP during steady operation. The air-fuel ratio, for example, the stoichiometric air-fuel ratio, is determined in advance through experiments, and this relationship is stored in the RO) 132. Therefore, when steady operation is being performed, ROM 32 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 , the air-fuel mixture supplied into the engine cylinder will basically have a stoichiometric air-fuel ratio. If the 02 sensor, which can detect any 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 target air-fuel ratio will be set to the stoichiometric air-fuel ratio below. The case where this is set will be explained.

In this case, the basic fuel injection time TP from the fuel injection valve 12
Basically, if only the fuel is injected, the air-fuel mixture supplied into the engine cylinder will have approximately the stoichiometric air-fuel ratio.

When the engine is not in a transient operating state, that is, during steady operation, the corrected fuel injection time TPAEW becomes zero, and the post-start increase correction coefficient FASE becomes 1.0 shortly after starting the engine. Therefore, the above equation (1) can be expressed as the following equation.

TAU MiTP-FAP-F...
(2) That is, at this time, the fuel injection time TAU is determined by the basic fuel injection time TP, the feedback correction coefficient FAF, and the correction coefficient F. The correction coefficient F is determined by the intake air temperature, engine cooling water temperature, etc., and for example, before warm-up is completed when the engine cooling water temperature is low, it becomes a value larger than 1.0, and 11
After one aircraft is completed, the value will be close to 1.0 or 1.0.

The feedback correction coefficient FAF is set to 0□ sensor 19 so that the air-fuel mixture supplied into the engine cylinder has the stoichiometric air-fuel ratio.
changes based on the output signal of Next, this feed bank correction coefficient FAF will be explained.

02 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 the air-fuel ratio is 1.
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 Ox 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 this Ox sensor 19. Referring to FIG. 3, first, in step 100, it is determined whether air-fuel ratio feedback control conditions are satisfied. For example, the increase correction coefficient FASE after engine startup is 1.
0, and when the engine cooling water temperature is not below a predetermined value, it is determined that the feedback control condition is satisfied. If the feedback control conditions are not satisfied, step 1
01, the feedback correction coefficient FAF is set to 1.0.

Therefore, during steady operation where the feedback control conditions are not met, the fuel injection time TAU is calculated based on the following equation.

TAυ=TP-F...(
3) On the other hand, if it is determined that the feed bank control conditions are satisfied, the process proceeds to step 102 and the Ox sensor 19
It is determined from the output signal whether the air-fuel mixture supplied into the engine cylinder is rich or not.

If 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 R5 is subtracted from the feedback correction coefficient FAF. Then step 10
At 6, the flag CAFR is sent. Therefore, in the next processing cycle, the process proceeds from step 104 to step 107, where = (Ki Rs) is subtracted from the feedback correction coefficient FAF to a predetermined constant value.

On the other hand, when the fuel changes from rich to lean, the process proceeds from step 102 to step 10B, 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 R8 is added to the feedback correction coefficient FAF, and then, in step 111, the flag CAFL is set. Therefore, in the next processing cycle, the process proceeds from step 109 to step 112, where a constant value is added to the feedback correction coefficient FAF. Therefore, the feedback correction coefficient FAF changes as shown in FIG.

When the fuel becomes rich, the feedback correction coefficient FAF is decreased and the fuel injection time TAU is shortened, and when the fuel becomes lean, the feedback correction coefficient FAF is increased and the fuel injection time TAU is lengthened. The supplied air-fuel mixture 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 of the intake port. 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 when fuel injection time TAU calculation starts to when fuel injection is actually performed, and because liquid injected fuel adhering to the inner wall surface of the intake boat 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, if an acceleration operation is performed and the absolute pressure PM in the surge tank 1 rises from PM to PM, the basics calculated from the absolute pressure PM and the engine speed NE will be calculated accordingly. Fuel injection time TP
will also rise. If the calculation of the fuel injection time TAU is started at all times ta, the absolute pressure PM at this time is PM
a, the basic fuel injection time TP is calculated based on this absolute pressure PMa, and the basic fuel injection time TP at this time is set as TPa. 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 ta, actual fuel injection is started at time tb. However, at time tb, the absolute pressure PM is PMb, which is higher than PMa, and at this time, the basic fuel injection time required to bring the air-fuel mixture to the stoichiometric air-fuel ratio is TPb, which is longer than TPa. Nevertheless, at time tb, fuel injection is performed only for the time calculated based on the basic fuel injection time TPa, so the injected fuel is less than the amount of injected fuel required to bring the mixture to the stoichiometric air-fuel ratio.
In this way, the mixture becomes lean. That is, actually the broken line W
Since the basic fuel injection time TP changes along the line, the air-fuel mixture becomes lean as shown by Y while it is 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 TPd indicate changes in the basic fuel injection time TP, and haftings Xa and Xb indicate the amount of liquid fuel flowing into the engine cylinder. The amount of liquid fuel flowing into the cylinder between I depends on the amount of fuel injection, that is, the amount of fuel adhering to the inner wall surface of the intake boat, etc.
Therefore, as the fuel injection amount increases, the amount of liquid fuel flowing into the engine cylinder increases.0 When the engine is in steady operation, the amount of liquid fuel is almost constant; The amount of liquid fuel increases as the engine load increases. Xa in Figure 6 is each absolute pressure PM
It is assumed that the same amount of liquid fuel is supplied into the engine cylinder as during steady operation, and in this case, even during acceleration operation, the air-fuel mixture supplied into the engine cylinder is theoretically empty. The fuel ratio is maintained. 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. x in Figure 6
b indicates the amount of liquid fuel that actually flows into the engine cylinder. Therefore, the liquid fuel 1xb that flows into the engine cylinder for a while after acceleration is started and after the acceleration is completed is smaller than the liquid fuel IXa during steady operation, so the air-fuel mixture becomes lean during this period as shown by Y. becomes.

Therefore, during acceleration operation, as shown by Y in Fig. 7, Y,
The lean shown by and the lean shown by Y2 overlap. Therefore, as shown in Fig. 7, the amount of fuel is increased by IczΔPM・C9 corresponding to Y during acceleration operation,
Quantity C3 (ΔPM+(, ΣΔPM) corresponding to Y2
If the amount of fuel is increased by C, 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 shortage amount (
TPb - TPa) is approximately equal to ΔPM・C# at time ta multiplied by time (tb - ta>),
If time (tb-ta) is expressed as 02, basic fuel injection time T
The insufficient amount of P will be expressed as C4AFM·C4. Note that since time (tb-ta) corresponds to the crank angle, Ct is a function of the engine speed NE.

On the other hand, the curve corresponding to the curve shown in Yt is C1(ΔP
M+C, ΣΔPM) - Can be expressed as C4. Here, C0 is called an attenuation coefficient and has a value smaller than 1.0. That is, C3(ΔPM+CIΣΔPM)C
4 is calculated when calculating the fuel injection time TAU, and C
3(ΔPM+C1ΣΔPM) - The value of C1 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 air-fuel mixture becomes leaner.

Therefore, C3 is a function of engine temperature and intake air temperature.

Therefore, C2ΔP during acceleration operation? I・C9 and Cs (Δ
PM+C+ΣΔPM) - By increasing the amount of fuel including C, the air-fuel mixture can be maintained at the stoichiometric air-fuel ratio.

This added value becomes the corrected fuel injection time TPAEW during the transient period in the above-mentioned equation (1). That is, TPAI! W is expressed by the following formula.

TPAB; (C4AFM+C3(ΔPM+〇IΣΔP
M)) ・C#...(4) Note that the rich state during deceleration operation is also as Yl and Yt in Figures 5 and 6, so if TPAEW in equation (4) above is used, the same result can be obtained. The air-fuel mixture supplied into the engine cylinders is maintained at a stoichiometric air-fuel ratio. However, during deceleration operation, ΔPM becomes negative, so TPAB- 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)・PAF-P
(5) However, if the engine is used for a long period of 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 may Moreover, it takes time for the liquid fuel that adheres to the inner wall surface of the intake boat to flow into the engine cylinder after it adheres. Therefore, when deposits adhere to the inner wall surface of the intake boat, etc., using equation (5) above, during acceleration operation, the deposits delay the inflow of liquid fuel into the engine cylinder, resulting in a lean mixture, whereas during deceleration operation, the deposits 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 formed, the corrected fuel injection time TPAE- is multiplied by the correction coefficient K, and the increase/decrease of fuel during acceleration/deceleration is corrected by this correction coefficient K, so that the air-fuel mixture is maintained regardless of the operating state of the engine. is maintained at the stoichiometric air-fuel ratio. In this case, as shown in equation (1) above, the fuel injection time TAU is calculated using the following equation.

TAIJ=(Tp+x-TPAEW>-FAF-F
-(6) In other words, 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, as shown in Fig. 8 (
As shown in A), after the acceleration operation is started, lean and rich are alternately repeated at approximately the same cycle, so the lean time and rich time do not differ much. However, if the deposit is attached, the air-fuel mixture becomes lean temporarily during acceleration operation, as shown in FIG. 8(B). If the air-fuel mixture temporarily becomes lean during acceleration operation in this way, the lean time after acceleration operation is started becomes longer than the rich time, as shown in FIG. 8(B). 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 is increased.
If the rich time becomes shorter than the rich time, the value of the correction coefficient is decreased and the deceleration fuel reduction rate is decreased.

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 0□ sensor 19 is being performed. If feedback control is not being performed, the process advances to step 202 to control each counter CAC.

Clearing CLAN 1 and CLAN 2 0 Next, when feedback control is started, the process proceeds to step 203 where it is determined whether or not the counter CLAN 1 has been cleared. At this time, the counter CLAN 1 has been cleared, so the process advances to step 204, and the counter CLAN 1 is cleared.
It is determined whether or not 2 is cleared. At this time, the counter CLAN 2 has been cleared, so the process proceeds to step 205. In step 205, it is determined whether ΔPM is larger than a certain value, for example, 391 mHg, that is, whether or not the vehicle is under acceleration. If ΔPM<39wH, it is determined that the operation is not accelerating, and the process proceeds to step 206. In step 206, ΔPM is set to a constant value, for example, -39m.
It is determined whether or not it is smaller than Hg, that is, whether or not it is during deceleration operation. If ΔPM>-39 mHg, it is determined that the operation is not decelerating, and the process proceeds to step 202, where each counter CAC, CLAN 1 is set.

CLAN 2 is cleared.

On the other hand, if it is determined in step 205 that ΔPM≧39mHg, that is, it is determined that acceleration operation is being performed, the process proceeds to step 207, where the count value of counter CLAN 1 is set to 1.
is set to 0. Then, the fuel injection time calculation routine proceeds to 0. In the next processing cycle, the process proceeds from step 203 to step 208. In step 208, ΔPM is -5wH.
It is determined whether or not it has become lower than CAC, that is, whether or not it has been decelerated after the start of acceleration operation. If ΔPM≦-5mHg, the process proceeds to step 202 and each counter CAC, CLAN
1, CLAN 2 is cleared. On the other hand, when the acceleration operation continues, ΔPM>-5 mHg, so the process proceeds from step 208 to step 209, where the counter CLAN 1 is incremented by 1. That is, as shown in FIG. 9(A), the acceleration operation is started and the absolute pressure PM in the surge tank 11 changes from PM+ to PMz.
If ΔPM exceeds 39fl)Ig, the counter CLAN1 starts counting up.

Next, in step 210, it is determined whether the count value of the counter CLAN 1 has become larger than a predetermined constant value A1. When CLANI<At, the routine proceeds to a fuel injection time calculation routine. On the other hand, CLAN1aA1
Then, the process proceeds to step 211, where it is determined from the output signal of the Ot total sensor 9 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, where the counter CAC is decremented by 1.
It is determined whether N1 has become larger than a predetermined constant value Bl.

If CLANI < 81, the routine proceeds to a fuel injection time calculation routine. That is, as shown in FIG. 9(A), until the count value of counter CLAN 1 changes from A1 to B1, it is determined whether the air-fuel mixture is lean or rich, and the air-fuel mixture is lean. Sometimes counter CAC
is counted up, and when the air-fuel mixture is rich, the counter CAC is counted down. Therefore, if the time period during which the count value of counter CLAN 1 reaches from AI to 81 is longer than the time period during which it is rich, the count value of counter CAC increases and becomes rich. 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 can be determined from the count value of the counter CAC when CLAN 1 becomes B1.

In this way, in the embodiment shown in FIG.
Until the count value of counter CLAN 1 reaches from Al to Bl, it is determined whether the air-fuel mixture is lean or rich, and therefore the count value of counter CLAN 1 becomes A1.
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 L''.

Figures 8 (C), (D), and (E) show 02 when accelerated 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 (D) and (B), lean and rich cycles are repeated at almost the same period even during acceleration operation, and lean and rich cycles are repeated at almost the same cycle.
As shown in FIGS. 8(C) and 8(D), the rich judgment period is set to a period in which the fuel becomes lean or rich in such a state. In other words, the set value A1. for the counter CLAN1. Bl has a count value of A
The period from 1 to 81 is determined to be 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), when 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 longer than the rich time. As a result, 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), when the count value of the counter CAC exceeds C1 when the lean/rich judgment period L' has elapsed, it is determined that the air-fuel mixture is lean during acceleration operation. If you do so, you will obviously make a wrong decision. 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 AI until the count value of LAN 1 reaches 81. By the way, fuel injection is usually started at a predetermined crank angle, and
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 counter CLAN 1 reaches 81 from A1. . In other words, during the rich determination period, fuel injection is performed a fixed number of times regardless of the engine speed.

By the way, the air-fuel ratio changes for each fuel injection, and feedback control is performed on this air-fuel ratio change, so the lean and rich cycles depend 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 01, it can be determined that the air-fuel mixture has become lean during acceleration operation. As shown in FIGS. 8(F) and (G), the fuel becomes rich when the lean rich judgment period has elapsed, and this rich time is determined by the control system of the fuel injection system as shown in FIG. 8(F). ) as shown in FIG. 8(G), or as shown in FIG. 8(G), it may become longer. However, if the lean/rich judgment period is set to almost the same as the lean or rich cycle when no deposit is attached, the results in Figures 8 (F) and (G) are shown.
To reliably judge leanness due to deposit attachment regardless of the length of the rich time when a lean/rich judgment period has elapsed.

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

Also, lean until the counter CLAN l reaches A1.
The reason why a rich determination is not made is that it takes a certain period of time for the air-fuel mixture supplied into the engine cylinder to become exhaust gas and reach the 02 sensor 19.

Returning to FIG. 11 again, in step 213 CLAN
If it is determined that 1≧B1, 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. CAC<C
If I, the process proceeds to step 216, where it is determined whether the count value of the counter CAC is smaller than a predetermined negative constant value DI. If CAC>Di, step 2
02 and each counter CLAN CLAN 1,
CLAN2 is cleared.

On the other hand, when it is determined in step 215 that CAC≧01, that is, when the CAC is at one level during acceleration, the process proceeds to step 217, where the acceleration correction coefficient KA
A predetermined constant value, for example 0.1, is added to C,
In this way, the acceleration correction coefficient KAC is increased. On the other hand, when it is determined in step 216 that CAC≦D1, that is, when the engine is rich during acceleration, 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, if it is determined in step 206 that ΔPM≦-39 mHg, that is, the vehicle is in deceleration operation, the process proceeds to step 219, where the count value of the counter CLAN 2 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 204 to step 220. In step 220, ΔPM is 5ml
It is determined whether or not it has become higher than Hg, that is, whether or not it has been accelerated after the start of deceleration operation, and ΔP M 'ia 5 WM
In the case of ug, the process advances to step 202 and each counter CA
C, CLAN 1 and CLAN 2 are cleared.

On the other hand, when deceleration operation is performed at mm, Δp
Since M < 5 mmHg, the process proceeds from step 220 to step 221, where the counter CLAN 2 is incremented by 1. That is, as shown in FIG. 9(B), deceleration operation is started and the absolute pressure P in the surge tank 11 is reduced.
M decreases from PM to PM, and at this time ΔPM is -3
When the temperature becomes lower than 9 mmHg, the counter CLAN 2 starts counting up.

Next, in step 222, it is determined whether the count value of the counter CLAN2 has become larger than a predetermined constant value (t!A2).If CLAN2<A2, the process proceeds to a fuel injection time calculation routine. , C.L.
When AN2≧A2, the routine proceeds to step 223, 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 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 lean, that is, if the air-fuel mixture is lean, 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 CLA
It is determined whether N2 has become larger than a predetermined constant value B2.

If CLAN2 < 82, the routine proceeds to the fuel injection time calculation routine, during which time the count value of counter CLAN2 reaches 82 from A2, as shown in FIG. 9(B), that is, during deceleration operation. It is determined whether the air-fuel mixture is rich or lean within the rich judgment period, and when the air-fuel mixture is rich, the counter CAC is counted up and the air-fuel mixture is incremented. When the signal is on, the counter CAC is counted down. Therefore, until the count value of counter CLAN 2 changes from A2 to B2, that is, within the lean/rich judgment period, if the time of being rich is longer than the time of being lean, the count value of counter CAC will increase. , if the lean time is longer than the rich time, the count value of the counter CAC decreases. Therefore, CLAN 2 is 82 to determine whether the air-fuel mixture is rich or lean during deceleration operation.
This can be determined from the count value of the counter CAC when .

If it is determined in step 225 that CLAN 2≧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>02, the process advances to step 202 and each counter CLAN CLAN 1 is counted.

CLAN 2 is cleared. On the other hand, step 2
When it is determined in step 27 that the current is CACkC2, that is, when it is rich during deceleration operation, step 2 is executed.
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 the CAC is 5D2, that is, 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 decreased.

The acceleration correction coefficient KAC and the deceleration correction coefficient KDC represent the correction coefficient K for the corrected fuel injection time TPAHW 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 If the fuel becomes rich during deceleration operation due to accumulation, the correction coefficient K is similarly increased. Note that these acceleration correction coefficient KAC and deceleration correction coefficient KD
C is stored in the bank up RAM 33a.

12th rgJ indicates a fuel injection time calculation routine executed subsequent to the routines shown in FIGS. 10 and 11. Referring to Figure 12, first step 30
At 0, it is determined whether or not the engine is starting. For example, when the engine speed NE is lower than 50 Or, p, II+, it is determined that the engine is starting. 0 If the engine is starting, proceed to step 301. The fuel injection time TAUSTA at the time of starting the engine is calculated based on the relationship shown in FIG. 14(A). This TAIISTA is a function of the engine cooling water temperature T and the acceleration correction coefficient KAC, as shown in FIG. It becomes larger as the amount of deposited increases. Next, in step 302, the fuel injection time TAU is set to TAUSTA, and fuel is injected for a period determined by this TAUSTA.

In the next step 303, the initial value of the post-start increase correction coefficient FASH, which is the increase value when the engine start is completed, is calculated based on the relationship shown in FIG. 14(B).

The initial value of PASE is also a function of the engine cooling water temperature T and the acceleration correction coefficient KAC, as shown in Fig. 14 CB).
It becomes larger as the engine cooling water temperature T becomes lower, and becomes larger as the acceleration correction coefficient KAC becomes larger, that is, as the amount of deposit increases.

Next, in step 304, the FASE attenuation rate α is calculated based on the relationship shown in FIG. 14(C). This attenuation ratio α is a function of the acceleration correction coefficient KAC as shown in FIG. 14(C), and increases as the acceleration correction coefficient KAC increases, that is, as the amount of deposit increases. Note that the relationships shown in FIGS. 14 (A) and (C) are
32.

If the engine speed NE exceeds 50 Or, p, a+ and it is determined that the engine is not starting, the process proceeds from step 300 to step 3.
05, absolute pressure sensor 21 and rotation speed sensor 23
The basic fuel injection TP is calculated from the output signal of . Next, in step 306, ΣΔPM is calculated based on the following equation.

ΣΔPM=Δgate+C1ΣΔPM...(
7) Next, in step 307, the corrected fuel injection time TPAEW is calculated based on the following equation.

TPAEW= (czΔPM+CzΣΔPM)・C4・
...(8) Combining the above equations (7) and (8) gives the following equation.

TPAEW = (CzΔPM + C1(ΔPl'l
+C1ΣΔPM))・C4 This equation represents the above-mentioned equation (4). Therefore, the corrected fuel injection time TPAE- is the injection time to maintain the air-fuel mixture at the stoichiometric air-fuel ratio during transient operation when no deposits have accumulated. It represents the increase/decrease in fuel.

In the next step 308, it is determined whether ΔPM is positive or zero. When it is determined in step 308 that ΔPM=0, or when it is determined that ΔPM>O5, that is, the accelerating operation is in progress, the process proceeds to step 309 where the acceleration correction coefficient KAC is set as the correction coefficient, and then the process proceeds to step 311. On the other hand, in step 30B, ΔPM<
When it is determined that the value is 0, that is, in a deceleration state, the process proceeds to step knob 310 where the deceleration correction coefficient KDC is set as a correction coefficient, and then the process proceeds to step 311.

In step 311, fuel injection time TAU is calculated based on the following equation.

TAU= (TP+-TPAf!W)・FAF-F
When the accelerating operation becomes lean due to the accumulation of ASE and F deposits, the correction coefficient K is increased. Therefore, during the next accelerating operation, K - TPAEW, that is, the accelerating fuel increase rate is increased, so that the air-fuel mixture reaches the stoichiometric air-fuel ratio. maintained. On the other hand, when the fuel becomes rich during deceleration due to deposit accumulation, the correction coefficient K is increased, so that K -TPAHW, that is, the deceleration fuel reduction rate, is increased during the next deceleration, thereby maintaining the air-fuel mixture at the stoichiometric air-fuel ratio. be done. Furthermore, when the engine becomes lean during acceleration due to deposit accumulation, the correction coefficient K is increased, and therefore the post-start increase correction coefficient FASE is increased, thereby preventing the air-fuel mixture from becoming lean during a predetermined period from the completion of engine start.

In the next step 312, the attenuation ratio α calculated in step 304 is subtracted from the post-start increase correction coefficient FASE. Next, in step 313, it is determined whether FASE has become 1.0 or less, and if FASE<1.0, the process proceeds to step 314, where FASE is set to 1.0. Therefore, when the engine start is completed, as shown in FIG. 13, the post-start increase correction coefficient FASt! is gradually decreased from the initial value calculated in step 303 each time the fuel injection time calculation routine is executed by a damping ratio α that increases as the acceleration correction coefficient KAC increases. In addition, the 13th
In the figure, the solid line indicates the post-start increase correction coefficient FASE when a deposit is attached, and the broken line indicates the post-start increase correction coefficient FASE when no deposit is attached. Therefore, as can be seen from Fig. 13, the increase in fuel injection amount due to deposits during a predetermined period after the completion of engine startup decreases with the elapsed time from engine startup, and the rate of decrease is further increased by the acceleration correction coefficient KAC. I see, it gets bigger. In this way, over a predetermined period of time after the engine has been started, the amount of air-fuel mixture after the start is commensurate with the leanness of the air-fuel mixture supplied to the engine cylinders due to deposits or the use of fuel containing a large amount of heavy components. This makes it possible to prevent the air-fuel ratio from becoming too rich in the latter half of the increase after startup.

In addition to the fuel injection valve 12, in an engine that is provided with a fuel injection valve for starting, a so-called start injector, and in which fuel injection is performed by the start injector when starting the engine, the opening time of the start injector is determined by the acceleration described above. Based on the correction coefficient KAC, it can be made longer as the acceleration correction coefficient KAC becomes larger.

In addition, the initial value of the post-start increase correction coefficient FASH was made a function of the engine cooling water temperature T and the acceleration correction coefficient KAC, but instead of the engine cooling water temperature T, a value indicating the engine warm-up state, such as engine oil temperature, is used. You can also do that.

〔Effect of the invention〕

The greater the degree of lean during acceleration, the greater the term z after startup.
By increasing the initial value and decay rate of the value,
It is possible to prevent the air-fuel ratio from becoming extremely rich in the latter half of the fuel increase after starting, thereby improving fuel efficiency and reducing exhaust gas tension.

[Brief explanation of drawings]

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 how to calculate the deposit learning value, Figure 10 and the first engineering drawing are flow charts for calculating the deposit learning value, and Figure 12 is the fuel injection time. FIG. 13 is a time chart showing control of fuel injection, and FIG. 14 is a diagram showing injection time, etc.

Claims (1)

[Claims] A fuel injection amount calculation means that calculates the fuel injection amount based on the engine operating state, and a target air-fuel ratio of the air-fuel mixture supplied into the engine cylinder based on the output signal of the oxygen concentration detector disposed in the engine exhaust passage. A fuel injection amount correction means for correcting the fuel injection amount so that the fuel injection amount is corrected, an acceleration operation state detection means for detecting the acceleration operation state, and a time period during which the air-fuel mixture becomes lean during acceleration operation based on the output signal of the oxygen concentration detector. an increase ratio calculation means for calculating an increase ratio of the fuel injection amount from the time when the fuel injection amount becomes rich; a storage means for storing the increase ratio calculated by the increase ratio calculation means; and a storage means for storing the increase ratio calculated by the increase ratio calculation means; The amount increases gradually from the initial value, which is increased as the amount increase rate is larger, according to the amount increase rate stored by , to the attenuation rate, which increases as the amount increase rate increases, as time elapses from the completion of starting. A fuel injection amount control device for an internal combustion engine, comprising a fuel injection amount increasing means for increasing the fuel injection amount by a value.