JPH06330788A - Fuel injection control device for multicylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent deterioration of emission caused by irregularity of A/F of each cylinder when unsynchronous injection is carried out at the starting time or accelerating time, in a fuel injection control device for a multicylinder internal combustion engine having a multi-point injection system. CONSTITUTION:In respect to #1 cylinder under an intake process during unsynchronous injection time, a factor K#1 is calculated for largely correcting the unsynchronous injection rate in a decreasing manner as the intake flow velocity is in a speedy timing (step 211). In respect to other cylinders, times T#3, T#4, T#2 from the timing of unsynchronous injection to the intake process immediately after it are obtained (step 212). A factor K2#3 is obtained for largely correcting the unsynchronous injection rate in a decreasing manner as the time T#3 is long (step 213). An unsynchronous injection pulse TASY1 is multiplied by the factors K1#1, K2#3, K2#4, K2#2, and an invalid injection pulse TV is added thereto. Then final injection pulses TAU1 to TAU2 are obtained (step 214).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention employs a multi-point injection system, which normally performs an independent injection for each cylinder at a timing synchronized with an intake stroke, and a predetermined condition such as starting or accelerating. The present invention relates to a fuel injection control device for a multi-cylinder internal combustion engine, in which simultaneous injection is simultaneously performed at all cylinders at asynchronous timing, and synchronous injection is suspended within a predetermined period covered by the asynchronous simultaneous injection.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Laid-Open No. 01-170735, in a fuel injection control device of a multipoint injection system, asynchronous simultaneous injection is performed at the time of acceleration, and at the time of this asynchronous simultaneous injection, other than the intake stroke. It has been proposed to control each cylinder in the stroke to suspend the independent injection only once.

Further, as disclosed in Japanese Patent Application Laid-Open No. 02-104934, there is known that a reduction correction means for reducing the pulse amount of the synchronous independent injection after the asynchronous simultaneous injection is provided in place of the suspension. Has been.

[0004]

However, the conventional system has the following problems. In conventional systems, the amount of asynchronous simultaneous injection is the same for each cylinder. Therefore, when the asynchronous simultaneous injection is performed, the cylinder in the intake stroke rides on the intake flow velocity and the wall wetness decreases, so that more fuel is more easily sucked in than in the cylinders outside the intake stroke, and the A / F becomes rich. , The emission was sometimes worse.

On the other hand, when the asynchronous simultaneous injection is performed, the cylinders that are in the explosion, compression, and exhaust strokes have different times until the subsequent intake, so the amount of fuel evaporation from the wall surface wet caused by the asynchronous simultaneous injection is different. The amount of fuel entering each cylinder in the intake stroke is different, and the A / F cannot be controlled correctly, which causes a problem that emission is deteriorated.

Furthermore, since the remaining amount of wall surface wetness of the intake port of each cylinder at the time of the synchronous injection (independent injection) first performed after the asynchronous simultaneous injection is different, the independent injection is first performed after the asynchronous simultaneous injection. The fuel is affected by the fuel evaporated from the wet wall surface, and the amount of fuel sucked into each cylinder is different from the required amount, so that the A / F cannot be controlled correctly and the essence deteriorates. there were.

Regarding the above problem, Japanese Patent Laid-Open No. 02-
No. 104934 shows that the emission reduction should be used to prevent emission deterioration, but it does not show how to specifically reduce the emission. Further, in the technique described in Japanese Patent Application Laid-Open No. 02-104934, since the independent injection is not stopped immediately after the asynchronous simultaneous injection, it is likely to be overrich in the first place, and thus it is necessary to reduce the amount in the independent injection. It did not suggest how to control the independent injection after the suspension of fuel injection.

Therefore, according to the present invention, in such a system, when asynchronous simultaneous injection is performed, the A /
The purpose is to prevent the emission from deteriorating due to the irregularity of F.

[0009]

A fuel injection control device for a multi-cylinder internal combustion engine according to the present invention, which has been made to achieve the above object, employs a multi-point injection system as described in claim 1. During normal operation, independent injection is performed for each cylinder at the same timing as the intake stroke, and simultaneous injection is performed at asynchronous timing for all cylinders when the engine is in a predetermined condition such as during start-up or acceleration. In a fuel injection control device for a multi-cylinder internal combustion engine, which suspends synchronous injection within a predetermined period covered by fuel by the asynchronous simultaneous injection, the asynchronous injection is performed according to the stroke of each cylinder at the time of the asynchronous simultaneous injection. It is characterized in that it comprises an asynchronous injection amount correction means for correcting the amount.

According to the fuel injection control device for a multi-cylinder internal combustion engine of the first aspect, the asynchronous injection is performed so that the amount of asynchronous injection varies depending on the stroke of each cylinder during asynchronous simultaneous injection. Therefore, in the cylinder in the intake stroke, the amount of fuel that is in consideration of the intake stroke is simultaneously injected asynchronously, and the amount of fuel that is suitable for each is asynchronous depending on whether it is in each of the exhaust stroke, the explosion stroke, and the compression stroke. It is injected simultaneously.

Particularly, as described in claim 2, in the fuel injection control device for a multi-cylinder internal combustion engine according to claim 1, the asynchronous injection amount correcting means is a cylinder in an intake stroke during asynchronous simultaneous injection. The amount of asynchronous injection to the cylinder is corrected according to the intake flow velocity at the time of asynchronous simultaneous injection so that it becomes smaller as the intake flow velocity becomes faster, and at the time of asynchronous simultaneous injection, the asynchronous injection to the cylinders other than the intake stroke is performed. The amount of injection
Depending on the time from the timing of the asynchronous simultaneous injection to the intake stroke immediately after, it is preferable to correct so that the longer this time is, the less it becomes.

In a cylinder in the intake stroke at the time of asynchronous simultaneous injection, the fuel is sucked into the cylinder before adhering to the intake port as a wall wet, so that it is almost unnecessary to consider the occurrence of wall wet. The fuel injection amount is corrected from a viewpoint different from that of other cylinders that must be considered. In this case, since the fuel intake amount in the cylinder in the intake stroke increases as the intake flow velocity increases, it is better to take this into consideration and make a correction so that the intake flow velocity becomes smaller as the intake flow velocity increases.

On the other hand, in the cylinders other than the intake stroke at the time of asynchronous simultaneous injection, almost all of the asynchronously injected fuel is once wet on the wall surface and then evaporated. And
In the intake stroke, this evaporated fuel and a part of the wall surface wet are sucked into the cylinder. The evaporation amount from the wet wall surface increases as the evaporation time increases. Therefore, according to the time from the timing of the asynchronous simultaneous injection to the intake stroke immediately after that, if the time is corrected so as to decrease as the time increases, the intake stroke into the cylinder is performed immediately after the asynchronous simultaneous injection. The fuel amount can be adjusted in a well-balanced manner for each cylinder.

On the other hand, as described in claim 3, in the fuel injection control device for a multi-cylinder internal combustion engine according to claim 1 or 2, further, regarding the first independent injection after the asynchronous simultaneous injection, It is desirable to provide an independent injection amount reduction correction means for reducing the amount of independent injection according to the stroke of each cylinder at the time of asynchronous simultaneous injection.

As described above, by correcting the amount of asynchronous injection for each cylinder, both the cylinders in the intake stroke at the time of asynchronous injection and the other cylinders are fueled during the asynchronous simultaneous injection and the rest thereafter. The inhaled amount is stable, the A / F can be controlled correctly, and the emission does not deteriorate. In addition to this, the apparatus according to the third aspect of the invention has the following effect by further correcting the first independent injection.

In the cylinder that is in the intake stroke at the time of asynchronous simultaneous injection, the amount of adhesion of the wall surface wet due to the asynchronous injection is very small. Therefore, at the time of the first independent injection, the fuel vapor based on the wall wet becomes very small. On the other hand, in the cylinder that was in the exhaust stroke at the time of asynchronous simultaneous injection, the asynchronously injected fuel became wet on the wall surface, and only the fuel vaporized in a short period from that was taken in during the period when the synchronous injection was suspended. Inhaled during the stroke. This means that, conversely, immediately after the intake stroke within the synchronous injection rest period, a large amount of wall wet remains. Therefore, at the time of the first independent injection, a large amount of the fuel vapor evaporated from the wall surface wet, which still remains in large quantities, is sucked together with the fuel that is synchronously injected.

In addition, also in each of the cylinder in the explosion stroke and the cylinder in the compression stroke at the time of asynchronous injection, the fuel vapor from the wall wet, which was left in the same manner, is also similarly left at the time of the first independent injection. It is inhaled together with the fuel that is synchronously injected. The amount of fuel vapor sucked in as evaporation from the wall surface wet at the time of the first independent injection in each cylinder is different depending on the relationship with the remaining amount of the wall surface wet.

Under such a phenomenon, according to the apparatus of the third aspect, the amount of the first independent injection is corrected according to the stroke of each cylinder at the time of asynchronous simultaneous injection, so that such a phenomenon is canceled out. The amount of fuel sucked in each cylinder can be balanced. The asynchronous injection correction means may not be provided, and the device may be configured to include only the independent injection reduction amount correction means.

That is, as described in claim 4, the multi-point injection system is adopted, and in normal times, independent injection is carried out for each cylinder at the timing synchronized with the intake stroke, such as during starting and acceleration. In a fuel injection control device for a multi-cylinder internal combustion engine, when a predetermined condition is satisfied, simultaneous injection is simultaneously performed in all cylinders at asynchronous timing, and synchronous injection is suspended within a predetermined period covered by the asynchronous simultaneous injection. With respect to the first independent injection after the asynchronous simultaneous injection, an independent injection reduction correction means for reducing the amount of the independent injection according to the stroke of each cylinder at the time of the asynchronous simultaneous injection is provided, and the independent injection reduction correction means is provided. The weight reduction correction is determined for the cylinder that was in the intake stroke at the time of asynchronous simultaneous injection according to the intake flow velocity so that the faster the intake flow velocity, the less the reduction correction. In cylinders other than, the multi-cylinder internal combustion engine is characterized in that, according to the time from the timing of asynchronous simultaneous injection to immediately after the intake stroke, the longer the time is, the smaller the correction of the amount of reduction becomes. The invention has been completed as a fuel injection control device.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall schematic diagram of a fuel injection control device for an internal combustion engine. The device is mounted on a vehicle. The embodiment relates to fuel injection control at the time of starting in a vehicle equipped with a 4-cylinder spark ignition type gasoline engine 1 adopting a multipoint injection system.

An intake pipe 2 and an exhaust pipe 3 are connected to the engine 1. An air cleaner 4 is provided in the most upstream part of the intake pipe 2, and intake air is introduced through the air cleaner 4 into the intake pipe 2.
It is designed to be inhaled inside. A surge tank 5 is provided in the middle of the intake pipe 2. An injector (fuel injection valve) 6 is arranged in an intake pipe (intake port) 2 of each cylinder in the engine 1. Further, the fuel in the fuel tank 7 is sucked up by the fuel pump 8, passes through the fuel filter 9, and the pressure regulator 1
0, the pressure is adjusted by the pressure regulator 10, and the pressure is returned to the fuel tank 7 again. The fuel whose pressure is adjusted to this constant pressure is supplied to the injector 6. Then, the injector 6 is opened by the power supply from the battery 15. As a result, fuel is injected and mixed with intake air to form a mixture, which is supplied to the combustion chamber 12 for each cylinder via the intake valve 11.

A spark plug 13 is arranged in each combustion chamber 12 of each cylinder. The high voltage generated by the igniter 14 is distributed to the spark plug 13 of each cylinder via the distributor 16. Further, a bypass passage 18 is formed so as to bypass the throttle valve 17 provided in the middle of the intake pipe 2. An idle speed control valve 19 is arranged in the bypass passage 18. When the engine is idle, this idle speed control valve 19
The engine speed is adjusted by adjusting the opening degree of.

An intake air temperature sensor 20 is provided at the most upstream portion of the intake pipe 2.
Is provided, and the intake air temperature can be detected by the sensor 20. Also, the throttle valve 1 of the intake pipe 2
A throttle opening sensor 21 is provided in the vicinity of the arrangement position of 7, and the opening of the throttle valve 17 can be detected by the throttle opening sensor 21. Further, the intake pipe internal pressure sensor 22 can detect the intake pipe internal pressure in the surge tank 5.

The engine 1 is provided with a water temperature sensor 23 for detecting the temperature of engine cooling water. Also,
A cylinder discrimination sensor 24 and a crank angle sensor 25 are arranged in the distributor 16. The crank angle sensor 25 generates a crank angle signal for each predetermined crank angle associated with the rotation of the crank shaft or the cam shaft of the engine 1. The cylinder discrimination sensor 24 also generates a cylinder discrimination signal for each specific position of a specific cylinder associated with rotation of the crankshaft or camshaft of the engine 1. More specifically, as shown in FIG. 10, the cylinder discrimination sensor 24 outputs two types of cylinder discrimination signals, and the crank angle sensor 25 outputs a crank angle signal.

Here, the cylinder discrimination signal is a signal for knowing at which rotational position the engine is now, and in the example of FIG. 10, the No. generated in the compression TDC of the first cylinder. No. 1 signal and No. 1 generated in the compression TDC of the fourth cylinder. There are two types of two signals. The cylinder discrimination signal is a signal for detecting a specific position of the specific cylinder (for example, the compression TDC of the first cylinder) at least once during the crankshaft 720 ° CA,
The crank angle signal is a signal that is generated a plurality of times in the crankshaft 180 ° CA and is generated at a cycle of at least 30 ° CA or less.

Further, in FIG. 1, an oxygen concentration sensor 26 is provided in the exhaust pipe 3 of the engine 1, and the oxygen concentration sensor 26 can detect the oxygen concentration in the exhaust gas of the engine 1. An electronic control unit (hereinafter referred to as ECU) 27 as a fuel injection control means is mainly composed of a microcomputer. ECU 27
A signal associated with the drive of the starter motor is input from the starter switch 28. Further, an intake air temperature sensor 20, a throttle opening sensor 21, an intake pipe pressure sensor 22, a water temperature sensor 23, a cylinder discrimination sensor 24, and a crank angle sensor 25 are connected to the ECU 27. And the ECU
27 receives signals from these sensors and detects the intake air temperature, throttle valve opening, intake pipe internal pressure, engine cooling water temperature, oxygen concentration of exhaust gas, and the like.

A battery 15 is connected to the ECU 27, and the ECU 27 detects the voltage of the battery 15. Further, the engine 1 is configured so that a starter motor (not shown) is driven by being supplied with electric power from the battery 15 to start (crank) the engine 1.

Next, the operation of the fuel injection control device for the internal combustion engine thus configured will be described. 2 to 7 show the ECU
27 shows a process (flow chart) executed by 27. Less than,
The processing of the ECU 27 will be described according to the flowchart. When the starter switch 28 is turned on and the starter motor is driven, the processing of the routine shown in FIG. 2 is started. The ECU 27 first determines in step 101 whether or not it is the asynchronous injection timing at startup. In the present embodiment, this timing indicates whether or not 50 msec has elapsed after the starter switch 28 was turned on. If the ECU 27 determines that the asynchronous injection timing at start (timing t1 in FIG. 10) is reached, the process proceeds to step 102 (functions as asynchronous injection means at start) to cause the injector 6 to execute simultaneous asynchronous injection for all cylinders. .

FIG. 3 shows the calculation process of the asynchronous injection pulse at the time of starting in step 102 of FIG. This process is also started by turning on the starter switch 28 (starting drive of the starter motor). The ECU 27 detects the water temperature THW in step 201, and calculates the start-time asynchronous injection pulse TASY1 in step 202 according to the water temperature THW. Further, the ECU 27 detects the battery voltage BAT in step 203, and in step 204, the battery voltage B
An invalid injection pulse TV corresponding to AT is calculated. The invalid injection pulse TV is for compensating for the electrical / mechanical operation delay that is inevitably generated when the injector is opened.

From step 205, the process of subtracting the asynchronous pulse is shown. In step 205, the current crank position XCRNK is obtained from the signal of the crank angle sensor 25 and the signal of the cylinder discrimination sensor 24. At the time of the asynchronous injection pulse at the time of starting, the signal of the cylinder discrimination signal sensor does not enter, and the current crank position may not be discriminated. At that time,
It is possible to store the crank position when the engine is stopped and to determine the current crank position when the engine is started (JP-A-60-240875). Alternatively, there is also a method in which the cylinder angle is calculated and back calculated from the crank angle signal.

The following steps 206 to 208 are
This is a process for dividing the subsequent processes depending on the stroke (intake, exhaust, explosion, compression) of the # 1 to # 4 cylinders at the current crank position XCRNK. For example,
In step 206, 0 ≦ XCRNK <180 ° C.
If it is determined to be A, the present crank position XCRN
In K, # 1 cylinder is intake stroke, # 2 cylinder is compression stroke, # 3
This means that the cylinder is in the exhaust stroke and the # 4 cylinder is in the explosion stroke, and the processing from step 210 onward is performed.

In step 210, the crank position parameter YCRNK is obtained. The crank position parameter YCRNK is a crank position based on the intake TDC of the cylinder, and always takes a numerical value of 0 to 180 ° CA in the cylinder in the intake stroke at the time of asynchronous injection. For the # 1 cylinder that is in the intake stroke during asynchronous injection, the crank position X
CRNK becomes YCRNK as it is.

In the following step 211, the correction coefficient K1 # 1 for the # 1 cylinder corresponding to the crank position parameter YCRNK is calculated. This correction coefficient K1 # 1 is shown in FIG.
Paying attention to the fact that the intake flow velocity fluctuates according to the parameter YCRNK as shown in FIG. 5, it is obtained from the K1 map set as shown in FIG. According to this K1 map,
The correction coefficient is set to be smaller as the intake flow velocity is faster. Further, the correction coefficient K1 has a value of 1.0 or less, and is intended for weight reduction correction. Note that FIG. 8 is an example.

The reason why such reduction correction is performed is that, for example, the fuel asynchronously injected when the intake flow velocity is fast has a very small amount of wall wet, and most of it is sucked directly into the cylinder along with the air flow. The reason for this is that if the same amount as the asynchronous injection amount for the other cylinders is set, it will become rich, and this will be prevented.

The amount directly sucked into this cylinder increases as the intake flow velocity increases. Therefore, the balance between the amount directly sucked into the cylinder and the amount of wall surface wetness for the # 1 cylinder is determined according to the intake flow velocity, and therefore the intake flow velocity as shown in FIGS. The correction coefficient K1 corresponding to is calculated.

In the following steps 212 to 213,
Since the time from asynchronous fuel injection to fuel intake is different,
This is a process for correcting the phenomenon that the amount of evaporation from the wet wall surface is different, so that the fuel drawn in the cylinders # 3, # 4, and # 2 is not different.

In step 212, the asynchronous injection is started for each of the # 3 cylinders (exhaust stroke during asynchronous injection), # 4 cylinder (explosion stroke during asynchronous injection), and # 2 cylinder (compression stroke during asynchronous injection). Calculate the time T # 3, T # 4, T # 2 until the intake stroke is completed. This time can be calculated by the following formula from the crank angle KCRNK until the intake stroke is completed and the engine speed Ne.

[0038]

[Equation 1]

When the times T # 3, T # 4, T # 2 from the start of asynchronous injection to the completion of the intake stroke are calculated in this way, in step 213, the times T # 3, T # 4, T # 2 are calculated. Then, the correction coefficient K2 is obtained. The correction coefficient K2 is obtained from the K2 map, an example of which is shown in FIG. The K2 map is set from the following viewpoints.

Intake stroke in each of cylinders # 3, # 4, and # 2 after asynchronous injection (synchronous injection is suspended)
The fuel sucked in is the fuel that has evaporated once during the time T # 3, T # 4, T # 2 after the wall surface became wet. If the time that can be evaporated is long, the amount of fuel evaporation increases,
The amount of fuel drawn into the cylinder increases. On the other hand, if the evaporable time is short, the fuel evaporation amount decreases, and the fuel amount sucked into the cylinder decreases. Therefore, unless correction is made according to the time T # 3, T # 4, T # 2 for each cylinder, the A / F will be different for each cylinder, and if an overrich cylinder occurs, the emission will deteriorate. If an over-lean cylinder occurs, a problem such as exhaust of raw gas due to poor ignition may occur. Therefore, for each of the # 3, # 4, and # 2 cylinders, in order to equalize the amount of fuel sucked into the cylinders in the intake stroke immediately after the completion of asynchronous injection, it is necessary to make a correction in consideration of the evaporation amount of the wall surface wet. Become. From such a viewpoint, the K2 map is set so that the longer the time T # 3 or the like, the larger the amount of weight reduction correction.

Since this evaporation amount is greatly influenced by the water temperature, a map is provided for each water temperature as shown in the figure. Further, since there is an influence of the intake pipe pressure and the like, the accuracy can be further improved by further correcting the intake pipe pressure and the like. In the following step 214, the asynchronous injection pulse TASY1
Then, the coefficients K1 # 1 and K2 obtained in steps 211 and 213
Multiply # 3, K2 # 4, and K2 # 2, and further, invalid injection pulse T
V is added to obtain final injection pulses TAU1 to TAU4.

On the other hand, through steps 206 and 207, 1
When it is determined that 80 ° CA ≦ XCRNK <360 ° CA, it means that the # 3 cylinder is in the intake stroke, and the routine proceeds to the processing of step 220 and thereafter. In step 220, 180 ° CA is subtracted from the crank position XCRNK in obtaining the crank position parameter YCRNK. As a result, the crank position parameter YCRNK from the intake TDC in the # 3 cylinder is determined.
The correction coefficient K1 # 3 for the # 3 cylinder corresponding to the crank position parameter YCRNK is calculated from the K1 map illustrated in FIG. 8, and the correction coefficient for cylinders other than the # 3 cylinder is calculated from the K2 map illustrated in FIG. K2 # 4, K2 # 2, K2 # 1 are calculated, and these coefficients K1 # 3, K2 # 4, K2 # 2, K2 # 1 are calculated by TAS.
By multiplying Y1 and adding the invalid injection pulse TV,
The final injection pulses TAU1 to TAU4 are obtained (steps 221 to 224).

Further, through steps 206 to 208, 3
When it is determined that 60 ° CA ≦ XCRNK <540 ° CA, it means that the # 4 cylinder is in the intake stroke, and the processing proceeds to step 230 and the subsequent steps. At step 230, 360 ° CA is subtracted from the crank position XCRNK in obtaining the crank position parameter YCRNK. As a result, the crank position parameter YCRNK from the intake TDC in the # 4 cylinder is determined.
A correction coefficient K1 # 4 for the # 4 cylinder corresponding to the crank position parameter YCRNK is calculated from the K1 map illustrated in FIG. 8, and a correction coefficient for cylinders other than the # 4 cylinder is calculated from the K2 map illustrated in FIG. K2 # 2, K2 # 1 and K2 # 3 are calculated, and these coefficients K1 # 4, K2 # 2, K2 # 1 and K2 # 3 are calculated by TAS.
By multiplying Y1 and adding the invalid injection pulse TV,
Final injection pulses TAU1 to TAU4 are obtained (steps 231 to 234).

Similarly, through steps 206 to 208,
If it is determined that 540 ° CA ≦ XCRNK, # 2
It means that the cylinder was in the intake stroke, and step 240
Move to the following process. In step 240, 540 ° CA is subtracted from the crank position XCRNK in obtaining the crank position parameter YCRNK. As a result, the crank position parameter YCRNK from the intake TDC in the # 2 cylinder is determined, and from the K1 map illustrated in FIG.
The correction coefficient K1 # 2 for the # 2 cylinder corresponding to NK is calculated, and the correction coefficients K2 # 1, K2 # 3, K2 # 4 for the cylinders other than the # 2 cylinder are calculated from the K2 map illustrated in FIG. The final injection pulses TAU1 to TAU4 are calculated by multiplying TASY1 by these coefficients K1 # 2, K2 # 1, K2 # 3, K2 # 4 and adding the invalid injection pulse TV (steps 241 to 241).
244).

In this way, when the final injection pulses TAU1 to TAU4 are calculated for each of the cases (steps 214, 224, 234, 244), the final injection pulses TAU1 to TAU4 are set as asynchronous injection pulses and fuel injection is executed. (Step 250).

According to this embodiment, as shown in FIG. 10, the asynchronous injection pulse itself is set to have a different length for each cylinder according to the stroke of each cylinder at the time of asynchronous simultaneous injection. It Moreover, the setting is made by the reduction correction corresponding to the intake flow velocity for the cylinder in the intake stroke, and for the other cylinders, the amount of the asynchronously injected fuel is evaporated after the wall surface becomes wet. Since it is performed by the reduction correction, the amount of fuel taken into each cylinder is not too much, and the emission is not deteriorated due to overrich. In addition, such correction does not reduce a fixed amount, but makes the amount of reduction different for each cylinder, so that too little fuel is taken in, misfiring due to over lean and resulting raw gas It does not cause problems such as the discharge of.

As a result, according to the fuel injection device of the embodiment, it is possible to achieve both a comfortable starting property and a suitable exhaust gas performance. Next, a second embodiment will be described.
The hardware configuration of the system of the second embodiment is similar to that of the first embodiment. In the second embodiment, the amount reduction correction is not performed for the asynchronous injection, and the amount reduction correction is performed for the first synchronous injection thereafter.

In the second embodiment, as shown in the flow chart of FIG. 11, it is judged whether or not the asynchronous injection is finished (step 301), and if it is not finished, the processing is finished. If the asynchronous injection has ended, it is determined whether the synchronous injection timing has come (step 30).
2). Then, the synchronous injection is executed (step 30).
3).

Details of the processing in step 303 are shown in FIG.
2 to 17 will be described. First, the ECU 27 detects the water temperature THW in step 401, and then executes step 402.
Then, the starting synchronous injection pulse TASY2 is calculated according to the water temperature THW. Further, the ECU 27 detects the battery voltage BAT in step 403, and calculates the invalid injection pulse TV according to the battery voltage BAT in step 404.

Steps 405 and thereafter show the processing for reducing the amount of sync pulse. In step 405, it is determined whether or not it is the first synchronous injection, and if “NO”, a pulse obtained by adding the invalid injection pulse TV to the synchronous injection pulse TASY2 is the synchronous injection pulse TA.
It is set as U1 to TAU4 (step 450), and fuel injection is executed (step 455).

If it is determined in step 405 that the injection is the first synchronous injection, the process proceeds to step 406 and thereafter. Step 40
6, the asynchronous injection start crank position XCRN at the start
K is the signal of the crank angle sensor 25 and the cylinder discrimination sensor 24
Signal and more. The processing of this step is exactly the same as in the first embodiment.

The following steps 407 to 409 are processing for dividing the subsequent processing depending on the stroke (intake, exhaust, explosion, compression) of the # 1 to # 4 cylinders at the asynchronous injection start crank position XCRNK. is there. For example,
In step 407, 0 ≦ XCRNK <180 ° C.
If it is determined to be A, this means that in the asynchronous injection start crank position XCRNK, the # 1 cylinder is in the intake stroke, #
This means that the two cylinders are in the compression stroke, the # 3 cylinder is in the exhaust stroke, and the # 4 cylinder is in the explosion stroke, and the processing from step 410 onward is performed.

In step 410, the crank angle position parameter YCRNK is obtained as in the first embodiment. This Y
CRNK is a crank position based on the intake TDC. In the following step 411, the correction coefficient K3 # 1 for the # 1 cylinder is calculated according to the crank position parameter YCRNK. This correction coefficient K3 # 1 is obtained from the K3 map set as shown in FIG. 18B, paying attention to the fact that the wall surface wet amount changes according to the parameter YCRNK as shown in FIG. 18A. . Here, the amount of wall wet becomes smaller as the intake air flow velocity becomes faster. The correction in the present embodiment is performed by reducing the fuel injection amount in the first independent injection as the wall wet in the cylinder that was in the intake stroke at the time of the asynchronous injection is decreased, and the fuel vapor from the wall wet causes the excess. The aim is to avoid being rich. Therefore, compared with the K1 map of the first embodiment, the K3 map tends to have the opposite relationship to YCRNK. The correction coefficient K3 also has a value of 1.0 or less like K1, and is intended for weight reduction correction. Further, FIG. 18 is an example.

In the following steps 412 to 413,
# 3 that was in a stroke other than the intake stroke at the time of asynchronous fuel injection
With respect to the # 4 and # 2 cylinders, this is a process for determining the reduction correction coefficient in the first independent injection according to the time until the intake stroke is completed immediately after the asynchronous injection. This process is adopted for the following reason.

In the intake stroke immediately after the asynchronous injection in the cylinders # 3, # 4, and # 2, which were in the stroke other than the intake stroke at the time of asynchronous fuel injection (the synchronous injection is suspended), the wall surface wetness caused by the asynchronous injection is caused. The vaporized fuel is sucked in as described in the first embodiment. by the way,
Some wall wet still remains when the intake stroke immediately after the asynchronous injection ends. Since the remaining amount has a complementary relationship with the evaporation amount, it is larger in the cylinder having an earlier intake stroke immediately after the asynchronous injection and smaller in the cylinder having a later intake stroke. Particularly, in the second embodiment, in asynchronous simultaneous injection, the same amount of fuel is injected into each cylinder, so
The remaining amount of steam wall wetness depends on the time from the asynchronous injection to the intake stroke immediately after. Therefore, by adjusting this relationship, it is possible to adjust # 3 during the first independent injection.
In order to prevent problems such as overrich in each of the cylinders # 4 and # 2, the coefficient K4 for reduction correction is calculated.

In step 412, the asynchronous injection is started for each of the # 3 cylinder (exhaust stroke during asynchronous injection), # 4 cylinder (explosion stroke during asynchronous injection), and # 2 cylinder (compression stroke during asynchronous injection). Calculate the time T # 3, T # 4, T # 2 until the intake stroke is completed. This time can be calculated by the equation (1) as in the first embodiment.

When the times T # 3, T # 4, T # 2 from the start of the asynchronous injection to the completion of the intake stroke are calculated in this way, in step 413, the times T # 3, T # 4, T # 2 are calculated. Then, the correction coefficient K4 is obtained. The correction coefficient K4 is obtained from the K4 map, an example of which is shown in FIG. The K4 map is
Paying attention to the fact that the amount of remaining wall wet mentioned above becomes smaller as the time T # 3, T # 4, T # 2 becomes longer. Eventually, if the remaining amount is small, it will evaporate from the remaining amount and the injected fuel will be injected during the first independent injection. In addition to this, the amount of fuel vapor inhaled is also set to be small. Therefore, as compared with the K2 map of the first embodiment, the K4 map has the opposite tendency. In this case as well, since the amount of evaporation is greatly affected by the water temperature, a map is provided for each water temperature as shown in the figure. Further, since there is an influence of the intake pipe pressure and the like, the accuracy can be further improved by further correcting the intake pipe pressure and the like.

In the following step 414, the coefficient K3 obtained in steps 411 and 413 is added to the asynchronous injection pulse TASY2.
The final injection pulses TAU1 to TAU4 are multiplied by # 1, K4 # 3, K4 # 4, and K4 # 2, and the invalid injection pulse TV is further added.
Ask for. On the other hand, through steps 406 and 407, 18
When it is determined that 0 ° CA ≦ XCRNK <360 ° CA, it means that the # 3 cylinder is in the intake stroke, and the process proceeds to step 420 and subsequent steps.

In step 420, the crank position XC is determined in determining the crank position parameter YCRNK.
Subtract 180 ° CA from RNK. by this,#
The crank position parameter YCRNK from the intake TDC in the three cylinders is determined, and the correction coefficient K3 # 3 for the # 3 cylinder corresponding to the crank position parameter YCRNK is calculated from the K3 map illustrated in FIG. 18, and illustrated in FIG. The correction coefficients K4 # 4, K4 # 2, K4 # 1 for cylinders other than the # 3 cylinder are calculated from the K4 map, and these coefficients K3
By multiplying TASY2 by # 3, K4 # 4, K4 # 2, K4 # 1 and adding the invalid injection pulse TV, the final injection pulse TA
U1 to TAU4 are obtained (steps 421 to 424).

Further, through steps 406 to 408, 3
When it is determined that 60 ° CA ≦ XCRNK <540 ° CA, it means that the # 4 cylinder is in the intake stroke, and the process proceeds to step 430 and thereafter. In step 430, 360 ° CA is subtracted from the crank position XCRNK in obtaining the crank position parameter YCRNK. As a result, the crank position parameter YCRNK from the intake TDC in the # 4 cylinder is determined.
From the K3 map illustrated in FIG. 18, the correction coefficient K3 # 4 for the # 4 cylinder corresponding to the crank position parameter YCRNK
Is calculated, correction coefficients K4 # 2, K4 # 1, K4 # 3 for cylinders other than the # 4 cylinder are calculated from the K4 map illustrated in FIG. 19, and these coefficients K3 # 4, K4 # 2, K4 are calculated. The final injection pulses TAU1 to TAU4 are obtained by multiplying TASY2 by # 1 and K4 # 3 and adding the invalid injection pulse TV (steps 431 to 434).

Similarly, through steps 406 to 408,
If it is determined that 540 ° CA ≦ XCRNK, # 2
It means that the cylinder was in the intake stroke, and step 440
Move to the following process. In step 440, 540 ° CA is subtracted from the crank position XCRNK in obtaining the crank position parameter YCRNK. As a result, the crank position parameter YCRNK from the intake TDC in the # 2 cylinder is determined, and this crank position parameter YC is determined from the K3 map illustrated in FIG.
Calculate the correction coefficient K3 # 2 for the # 2 cylinder according to RNK,
Correction coefficients K4 # 1, K4 # 3, K4 # 4 for cylinders other than the # 2 cylinder are calculated from the K2 map illustrated in FIG. 19, and these coefficients K3 # 2, K4 # 1, K4 # 3, K4 are calculated. The final injection pulses TAU1 to TAU4 are obtained by multiplying TASY2 by # 4 and adding the invalid injection pulse TV (step 441).
~ 444).

In this way, when the final injection pulses TAU1 to TAU4 are calculated for each of the cases (steps 414, 424, 434, 444), the final injection pulses TAU1 to TAU4 are set as asynchronous injection pulses and fuel injection is executed. (Step 455).

According to the present embodiment, as shown in FIG. 20, in the asynchronous simultaneous injection, the same amount of fuel is injected in all cylinders, but in the first independent injection thereafter, each cylinder is subjected to asynchronous injection. Depending on the stroke, the synchronous injection pulse itself is set to have a different length for each cylinder. Moreover, the setting is made by the reduction correction corresponding to the intake flow velocity for the cylinder in the intake stroke at the time of asynchronous injection, and for the other cylinders, the wall stroke due to the asynchronous injection is immediately after the intake stroke (injection pause). At the end of the period, a reduction correction is made according to how much remains, so there is no excessive intake of fuel into each cylinder during the first independent injection, and the emission is deteriorated due to overrich. Do not invite. On the contrary, it does not cause too little fuel to be inhaled, and it does not cause problems such as misfire due to over leaning and consequent discharge of raw gas.

As a result, according to the fuel injection device of the embodiment, it is possible to achieve both a comfortable starting property and a suitable exhaust gas performance. As described above, according to each embodiment, it is possible to achieve both a comfortable starting property and a suitable exhaust gas performance, but these embodiments are not limited to the starting time,
It may be applied as it is during acceleration.

Further, the first embodiment and the second embodiment may be combined, and the asynchronous injection may be corrected for reduction, and the first independent injection immediately after the asynchronous injection may be corrected for reduction. In this case, the K3 map and the K4 map may be set in consideration of the different asynchronous injection amounts. By combining the two, it is possible to prevent the occurrence of overrich in the intake stroke during the asynchronous injection and each subsequent injection pause, and it is possible to average the influence of the asynchronous injection in each cylinder during the first independent injection. , Even more effective.

Further, in the first embodiment, the amount of asynchronous injection is reduced from the basic amount TASY1.
It is also possible to make Y1 small and adjust the increase correction amount for this for each cylinder. As described above, it is needless to say that the present invention is not limited to the above-described embodiments, and various modes can be adopted without departing from the scope of the invention.

[0067]

According to the fuel injection control apparatus for a multi-cylinder internal combustion engine of the present invention, when asynchronous simultaneous injection is performed at the time of starting or acceleration, deterioration of emission due to imbalance of A / F of each cylinder is prevented. be able to.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a system common to each embodiment.

FIG. 2 is a flowchart showing a main routine of control processing in the first embodiment.

FIG. 3 is a flowchart of an asynchronous injection control process in the first embodiment.

FIG. 4 is a flowchart of an asynchronous injection control process in the first embodiment.

FIG. 5 is a flowchart of an asynchronous injection control process in the first embodiment.

FIG. 6 is a flowchart of an asynchronous injection control process in the first embodiment.

FIG. 7 is a flowchart of an asynchronous injection control process in the first embodiment.

FIG. 8 is an explanatory diagram of a K1 map according to the first embodiment.

FIG. 9 is an explanatory diagram of a K2 map in the first embodiment.

FIG. 10 is a timing chart illustrating the operation and effect of the first embodiment.

FIG. 11 is a flowchart showing a main routine of control processing in the second embodiment.

FIG. 12 is a flowchart of an asynchronous injection control process in the second embodiment.

FIG. 13 is a flowchart of an asynchronous injection control process in the second embodiment.

FIG. 14 is a flowchart of an asynchronous injection control process in the second embodiment.

FIG. 15 is a flowchart of an asynchronous injection control process in the second embodiment.

FIG. 16 is a flowchart of an asynchronous injection control process in the second embodiment.

FIG. 17 is a flowchart of an asynchronous injection control process in the second embodiment.

FIG. 18 is an explanatory diagram of a K3 map according to the second embodiment.

FIG. 19 is an explanatory diagram of a K4 map in the second embodiment.

FIG. 20 is a timing chart illustrating the operation and effect of the second embodiment.

[Explanation of symbols]

1 ... Engine, 2 ... Intake pipe, 3 ... Exhaust pipe,
4 ... Air cleaner, 5 ... Surge tank, 6 ...
・ Injector, 7 ... Fuel tank, 8 ... Fuel pump, 9 ... Fuel filter, 10 ... Pressure regulator, 11 ... Intake valve, 12 ... Combustion chamber, 1
3 ... Spark plug, 14 ... Igniter, 15
... Battery, 16 ... Distributor, 17
... Throttle valve, 18 ... Bypass passage, 1
9 ... Idle speed control valve, 20.
..Intake air temperature sensor, 21 ... Throttle opening sensor,
22 ... Intake pipe pressure sensor, 23 ... Water temperature sensor, 24 ... Cylinder discrimination sensor, 25 ... Crank angle sensor, 26 ... Oxygen concentration sensor, 28 ... Starter switch.

Claims (4)

[Claims] 1. A multi-point injection system is adopted, and in normal times, independent injection is carried out for each cylinder at the same timing as the intake stroke, and all cylinders are operated under prescribed conditions such as during start-up and acceleration. In a fuel injection control device for a multi-cylinder internal combustion engine, which simultaneously performs simultaneous injection at asynchronous timing, and suspends synchronous injection within a predetermined period covered by the fuel by the asynchronous simultaneous injection, Depending on the stroke for each cylinder,
A fuel injection control device for a multi-cylinder internal combustion engine, comprising an asynchronous injection amount correction means for correcting the amount of asynchronous injection. 2. The fuel injection control device for a multi-cylinder internal combustion engine according to claim 1, wherein the asynchronous injection amount correction means sets the asynchronous injection amount to the cylinder in the intake stroke at the time of asynchronous simultaneous injection. According to the intake flow velocity at the time of injection, the higher the intake flow velocity, the smaller the correction, and
Correct the amount of asynchronous injection to the cylinders other than the intake stroke during asynchronous simultaneous injection so that it decreases as the time increases, depending on the time from the timing of asynchronous simultaneous injection to the intake stroke immediately after. A fuel injection control device for a multi-cylinder internal combustion engine. 3. The fuel injection control device for a multi-cylinder internal combustion engine according to claim 1 or 2, further comprising the stroke of each cylinder at the time of asynchronous simultaneous injection for the first independent injection after the asynchronous simultaneous injection. A fuel injection control device for a multi-cylinder internal combustion engine, comprising: an independent injection amount reduction correcting means for reducing the amount of independent injection according to the above. 4. A multi-point injection system is adopted, and in normal times, independent injection is performed for each cylinder at the same timing as the intake stroke, and all cylinders are operated under predetermined conditions such as during start-up and acceleration. In a fuel injection control device for a multi-cylinder internal combustion engine, which performs simultaneous injection simultaneously at asynchronous timing and suspends synchronous injection within a predetermined period covered by fuel by the asynchronous simultaneous injection, the first after the asynchronous simultaneous injection. The independent injection is provided with an independent injection reduction correction means for reducing the amount of the independent injection according to the stroke of each cylinder at the time of the asynchronous simultaneous injection. For cylinders that were in the intake stroke, it is determined according to the intake flow velocity so that the higher the intake flow velocity, the less the weight reduction correction. Depending on the time of the intake stroke immediately after the timing of simultaneous injection, this time is longer, the fuel injection control apparatus for a multi-cylinder internal combustion engine and determining so that reduction correction decreases.