JP3156612B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel supply control device for an internal combustion engine.

[0002]

2. Description of the Related Art Immediately after the start of an engine, the temperature in the engine cylinder and the intake passage is low, and the inside of the engine cylinder is maintained at substantially atmospheric pressure, so that the rate of vaporization of the fuel injected from the fuel injection valve is small. . As a result, it is difficult to ignite. Therefore, a large amount of injected fuel is required until ignition. Therefore, there has been conventionally known an internal combustion engine in which the fuel injection amount at the start, which is the fuel injection amount at the time of engine start, is extremely large.

However, once the fuel is ignited, it is not necessary to inject such a large amount of fuel. Rather, a large amount of unburned HC is discharged from the engine, which is not preferable.
On the other hand, when the engine is ignited, the engine speed starts to increase and the crank angular speed starts to increase. Therefore, after cranking is started, it is determined whether or not ignition has occurred based on whether or not the rate of increase of the crank angular speed has exceeded the set rate of increase. A fuel supply control device for an internal combustion engine that is started is known (see Japanese Utility Model Laid-Open No. 63-138476).

[0004]

That is, in this fuel supply control device, when the detected increase rate of the crank angular velocity is lower than the set increase rate, the fuel injection amount is increased, and the increase rate of the crank angular velocity is higher than the set increase rate. Then, the fuel injection amount is reduced. In other words, the fuel injection amount is calculated based on the crank angular velocity.

However, the fuel injection amount is calculated based on the crank angular velocity before the actual fuel injection, for example, by a set crank angle. Therefore, even when the detected increase rate of the crank angular velocity is lower than the set increase rate, when the large amount of fuel calculated based on the increase rate of the crank angular velocity is actually injected, the case where the ignition has already occurred may occur. In this case, there is a problem that a large amount of unburned HC is discharged as described above.

[0006]

According to a first aspect of the present invention, there is provided a starting fuel injection amount calculating means for calculating a starting fuel injection amount which is a fuel injection amount at the time of engine start. Calculate the weight reduction coefficient from the number of fuel injections
A decrease correction coefficient calculating means, and a weight loss means to lose weight the fuel injection amount with a reduced-amount correction factor from the start timing fuel injection amount
And the reduction correction coefficient increases as the number of fuel injections increases.
And the degree of weight loss is determined to be large. Up
As described above, once the engine speed starts to increase, the engine speed
Turns increase sharply. In this case, the engine speed is detected
If the weight loss correction coefficient is calculated accordingly,
The engine speed at the time of fuel injection is the engine speed
Significantly higher than when the number was detected.
As a result, excessive fuel is injected. There
In the first invention, the reduction correction coefficient is calculated from the number of fuel injections.
Calculate and compensate for the decrease as the number of fuel injections increases
The weight loss correction coefficient is set so that the positive degree increases.
You.

[0007] According to a second aspect, in the first aspect, based on the surrounding environment or the engine operating state at the time of cranking.
The engine speed has increased since cranking started.
Estimate the cranking period before starting to ascend,
The estimated cranking period elapses after
Start the weight loss action of the weight loss means from when you pass
However, the weight loss correction coefficient has not passed during the estimated cranking period.
As the number of fuel injections from when
The degree is determined so as to increase. That is, 2
In the second invention, after cranking is started, the estimated
From the time when the ink-locking period has elapsed
Starts, so a lot of fuel is injected when it ignites
Therefore, a large amount of unburned H
C is prevented from being discharged. In addition, the estimated crankin
Engine operation during the surrounding period or during the cranking period
State, i.e. engine cooling water temperature, cylinder wall temperature, intake
Temperature, fuel temperature, engine oil temperature, cranking rotation
Estimated based on number, atmospheric pressure, etc.

[0008] According to a third aspect, in the second aspect , the engine operating state during the surrounding environment or the cranking period.
Calculates the upper limit integrated fuel injection amount based on
Is calculated since the start of fuel injection, and
Period until the fuel injection amount exceeds the upper limit integrated fuel injection amount.
It is assumed that it is during the cranking period. Blasphemy
As mentioned earlier, the cylinder inner wall temperature is low immediately after starting the engine.
At this time, the fuel adhering to the inner wall surface of the cylinder is not easily vaporized. on the other hand,
When the amount of fuel attached to the inner wall of the cylinder increases to a certain extent,
The charge is increased, and thus ignition becomes possible. So number 3
In the eye invention, the accumulated fuel from the start of cranking is
Fired when the fuel injection amount exceeded the upper limit cumulative fuel injection amount
To judge.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, 1 is a cylinder block, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is an intake valve, 6 is an intake port, 7 is an exhaust valve, and 8 is exhaust. A port 9 indicates a spark plug. Intake port 6
Are connected to a common surge tank 11 via a corresponding intake branch pipe 10, and the surge tank 11 is connected to an air cleaner 13 via an intake duct 12. A fuel injection valve 14 for injecting fuel toward the intake port 6 is disposed in the intake branch pipe 10, and the fuel injection valve 14 is controlled based on an output signal from the electronic control unit 20. A throttle valve 15 is arranged in the intake duct 12.

Still referring to FIG. 1, 16 is a starter motor, 17 is a key switch having an ignition switch 17a and a starter motor switch 17b,
Reference numeral 18 indicates a battery. When the ignition switch 17a is turned on, power is supplied to the CPU 24. The starter motor switch 17b can be turned on only when the ignition switch 17a is on. When the starter motor switch 17b is turned on, power is supplied to the starter motor 16 and thus cranking is started.

An electronic control unit (ECU) 20 is composed of a digital computer, and is connected to a ROM (Read Only Memory) 22, R
An AM (random access memory) 23, a CPU (microprocessor) 24, an input port 25, and an output port 26 are provided. The cylinder block 1 has a water temperature sensor 27 for generating an output voltage proportional to the engine cooling water temperature THW.
Is attached, and the output voltage of the water temperature sensor 27 is AD
The data is input to the input port 25 via the converter 28. A pressure sensor 29 that generates an output voltage proportional to the pressure in the surge tank 11 is attached to the surge tank 11, and the output voltage of the pressure sensor 29 is input to an input port 25 via an AD converter 30. The CPU 24 calculates the intake air amount Q based on the output voltage of the pressure sensor 29. The input port 25 is connected to a rotation speed sensor 31 for detecting the engine rotation speed. Further, a signal indicating that the starter motor switch 17b is on is input to the input port 25. On the other hand, the output port 26 is connected to each ignition plug 9 and each fuel injection valve 14 via a corresponding drive circuit 32.

FIG. 3 shows the engine speed N at the time of starting the engine.
Is shown. Referring to FIG. 3, when the starter motor switch 17b is turned on at the time a to start cranking, the engine speed N increases to the cranking speed NC, and then becomes substantially constant at this NC. Next, when ignition occurs at time b, the engine speed N starts to increase, and then at time c, the engine speed N becomes higher than a predetermined set speed N1 (for example, 400 rpm). Therefore, in the example shown in FIG. 3, the period from time a to time b is the actual cranking period ACP.

In the internal combustion engine shown in FIG. 1, the fuel injection time TAU from the start of cranking until the engine speed N becomes higher than the set speed N1 is calculated based on the following equation. TAU = TAUSTA KR KK Here, TAUSTA is the basic fuel injection time at the time of starting, KR
Represents a reduction correction coefficient, and KK represents a correction coefficient.

The starting basic fuel injection time TAUSTA is a fuel injection time required to start the engine quickly, and is much longer than during normal engine operation. The starting basic fuel injection time TAUSTA is obtained in advance by an experiment, and is stored in the ROM 22 in advance as a function of the engine cooling water temperature THW as shown in FIG.

The correction coefficient KK collectively represents an atmospheric pressure correction coefficient, a battery voltage correction coefficient, and the like.
It is set to 1 when there is no need for correction. The basic fuel injection time at start TAUS is set after the ignition is started after the cranking is started and the engine speed N starts to increase after the cranking is started.
This is for correcting the amount of decrease in TA, and is set to 1 when the amount of decrease is not corrected.

On the other hand, after N> N1, the fuel injection time TAU is calculated based on the engine speed N, the intake air amount Q, and the like. Next, a method for correcting weight loss using the weight reduction coefficient KR will be described with reference to FIGS. As described at the beginning, if a large amount of fuel is injected after the ignition is started after the cranking is started and the engine speed N starts to increase, a large amount of unburned HC is discharged from the engine. Therefore, it is necessary to accurately start the weight loss correction from the time of ignition. On the other hand, the ignition timing, that is, the cranking period is determined according to the surrounding environment or the engine operating state during the cranking period. Therefore, in the present embodiment, the cranking period is estimated based on the surrounding environment or the engine operating state during the cranking period, and the amount of reduction by the weight reduction correction coefficient KR is determined after the estimated cranking period ECP has elapsed after the cranking was started. The correction operation is started. In this manner, the corrective action for reducing the amount of fuel can be accurately started from the time of ignition, so that a large amount of unburned HC can be prevented from being discharged at the time of starting the engine. In addition, it is possible to prevent misfire due to excessive injected fuel after ignition, and thus it is possible to ensure good engine startability.

Incidentally, the cranking period becomes longer as the engine cooling water temperature THW becomes lower. On the other hand, the longer the cranking period, the greater the number of fuel injections since the start of cranking. Therefore, in the present embodiment, as shown in FIG. 4, an upper limit fuel injection number CCP that increases as the engine cooling water temperature THW becomes lower is obtained in advance, and the fuel injection number CINJ after the cranking is started is determined by the upper limit fuel injection number CINJ. Until the number of times of injection CCP becomes larger, the estimated cranking period ECP is set. In other words, when the number of times of fuel injection CINJ becomes larger than the upper limit of number of times of fuel injection CCP, the reduction correction operation by the reduction correction coefficient KR starts. Therefore, the upper limit fuel injection number CCP indicates the estimated cranking period. The upper limit fuel injection number CCP is stored in advance in the ROM 22 as a function of the engine coolant temperature THW as shown in FIG.

Referring again to FIG. 3, when cranking is started at time a, the number of times of fuel injection CINJ gradually increases, and then becomes larger than the upper limit number of times of fuel injection CCP. CINJ> CCP after starting cranking
Is the estimated cranking period ECP and CI
When NJ> CCP, the weight loss correction coefficient KR is made smaller than 1, and the weight loss correction operation is started. Thus, CINJ> CCP at time b,
Therefore, it is possible to accurately start the weight loss correction operation from the time of ignition. Note that CINJ ≦ CCP
In the case of, the weight loss correction coefficient KR is maintained at 1, that is, the weight loss correction operation is stopped.

By the way, after the engine speed N starts to increase, as the engine speed N increases, the intake charging efficiency decreases, and therefore the intake air amount Q decreases. Therefore, in order to inject fuel corresponding to the intake air amount Q at this time, it is necessary to increase the degree of reduction correction as the engine speed N increases. Therefore, as shown in FIG. 3, after the estimated cranking period ECP has elapsed and the weight-reduction correction operation has started, the weight-reduction correction coefficient KR is gradually reduced, so that the fuel injection time TAU is gradually shortened. .

On the other hand, at this time, as described above, the engine speed N sharply increases. Therefore, if the engine speed N is detected and the decrease correction coefficient KR is calculated in accordance with the engine speed N, the actual fuel injection is performed. The amount becomes larger than the optimal fuel injection amount. Therefore, the optimum amount correction coefficient KR for the intake air amount Q after the elapse of the estimated cranking period ECP is obtained in advance by experiment and stored, and the stored amount of reduction correction coefficient KR is used to perform the amount reduction operation. I'm trying to do it. That is, as shown in FIG. 5, the number of fuel injections after the elapse of the estimated cranking period ECP is CINJ-CCP.
Is stored in advance, and the reduction correction coefficient KR is updated each time fuel injection is performed. This decrease correction coefficient KR is the number of fuel injections CINJ after the estimated cranking period ECP has elapsed.
-Decrease as CCP increases
22.

In this way, the reduction correction coefficient KR can always be maintained at the optimum value with respect to the intake air amount Q after the elapse of the estimated cranking period ECP, so that the fuel injection amount can be maintained at the optimum value. . After the time c and N> N1, the fuel injection time TAU is calculated based on the engine speed N and the intake air amount Q, as described above. Stopped.

FIG. 6 is a routine for calculating the fuel injection time according to this embodiment. This routine is executed by interruption every set injection processing angle after the starter motor switch 17b is turned on and cranking is started. Referring to FIG. 6, first, at step 40, it is determined whether or not the engine speed N is equal to or less than a set speed N1. Since N ≦ N1 during the cranking period, the routine proceeds to step 41, where the number of times of fuel injection CINJ is incremented by one. In the following step 42, the starting basic fuel injection time TAUSTA is calculated from the map of FIG. In the following step 43, the upper limit fuel injection number CCP is calculated from the map of FIG. In the following step 44, it is determined whether or not the current number of fuel injections CINJ is larger than the upper limit fuel injection number CCP. When CINJ ≦ CCP, it is determined that the estimated cranking period is still in progress, and then the routine proceeds to step 45, where the reduction correction coefficient KR is set to 1, and the routine proceeds to step 47. On the other hand, when CINJ> CCP, it is determined that the estimated cranking period ECP has elapsed, and then the routine proceeds to step 46, where the reduction correction coefficient KR is calculated from the map of FIG. In a succeeding step 47, a correction coefficient KK is calculated. In the following step 48, the fuel injection time TAU is calculated based on the following equation.

TAU = TAUSTA.KR.KK Next, the processing cycle ends. Fuel is injected from the fuel injection valve 14 for a fuel injection time TAU. On the other hand, when N> N1 in step 40, the routine proceeds to step 49, where the fuel injection count value CINJ is cleared. Then, the routine proceeds to step 50, where the fuel injection time TAU is determined based on the engine speed N and the intake air amount W. Is calculated. Next, the processing cycle ends.

The unburned H discharged from the engine during the operation of the engine from when the engine is started until the engine is stopped.
Most of C is discharged when the engine is started. Therefore, if a large amount of unburned HC can be prevented from being discharged at the time of starting the engine, a large amount of unburned HC can be prevented from being discharged during the operation of the engine. Next, another embodiment will be described.

FIG. 7 is a routine for calculating the fuel injection time. This routine is executed by interruption every set injection processing angle after cranking is started.
Referring to FIG. 7, first, at step 60, the engine speed N
Is smaller than or equal to the set rotation speed N1. Since N ≦ N1 during the cranking period, step 6 follows.
Proceeding to 1, the number of times of fuel injection CINJ is incremented by one. In the following step 62, the basic fuel injection time at start TAUSTA is calculated from the map of FIG. In the following step 63, the upper limit integrated fuel injection time ULS is calculated from the map of FIG.

Since the temperature of the wall surface of the intake port 6 or the combustion chamber 4 immediately after the start of the engine is low, the fuel adhering to these wall surfaces at this time is unlikely to vaporize. On the other hand, when the amount of fuel attached to these wall surfaces increases to some extent, the amount of vaporized fuel increases, and thus ignition becomes possible. Therefore, an integrated fuel injection time at which the integrated fuel injection amount after the start of cranking becomes the ignitable fuel amount is previously determined as an upper limit integrated fuel injection time ULS by an experiment, and the integrated fuel injection time after the start of cranking is calculated. The fuel injection time STAU is equal to the upper limit integrated fuel injection time UL
When it becomes longer than S, it is determined that the cranking period has elapsed. Therefore, the upper limit integrated fuel injection time ULS represents the estimated cranking period.
This upper limit integrated fuel injection time ULS is equal to the engine cooling water temperature THW.
Is stored in the ROM 22 in advance as a function of

In the following step 64, it is determined whether or not the current integrated fuel injection time STAU is longer than the upper limit fuel injection time ULS. When STAU ≦ ULS, it is determined that the estimated cranking period is still in progress, and then step 6
The process proceeds to step 5, where the weight reduction coefficient KR is set to 1, and the subsequent step 6
After incrementing the fuel injection number CCQ during the estimated cranking period by 1 in step 6, the routine proceeds to step 68.
Proceed to. On the other hand, when STAU> ULS, it is determined that the estimated cranking period ECP has elapsed, and then the routine proceeds to step 67, where the reduction correction coefficient KR is calculated from the map of FIG. That is, the reduction correction operation starts when STAU> ULS. This decrease correction coefficient KR is an optimal decrease correction coefficient for the number of fuel injections CINJ-CCQ after the estimated cranking period ECP has elapsed. This reduction correction coefficient KR is obtained in advance by an experiment, and is stored in the ROM 2 in advance in the form of a map shown in FIG.
2 is stored.

In the following step 68, a correction coefficient KK is calculated. In the following step 69, the fuel injection time TAU is calculated based on the following equation. TAU = TAUSTA KR KK Fuel is injected from the fuel injection valve 14 for the fuel injection time TAU. In the following step 70, the integrated fuel injection time ST
AU is incremented by TAU. Next, the processing cycle ends.

On the other hand, when N> N1 at step 60, the routine proceeds to step 71, where the fuel injection count value CINJ is cleared, and at step 72, the accumulated fuel injection time STAU is cleared.
At 3, the number of times of fuel injection CCQ is cleared. In the following step 74, the fuel injection time TAU is calculated based on the engine speed N, the intake air amount W, and the like. Next, the processing cycle ends.

In the embodiments described above, the upper limit fuel injection number CCP and the upper limit integrated fuel injection time ULS are calculated as functions of the engine coolant temperature THW. However, these CCP and ULS are calculated based on other ambient environment or the engine operating state during the cranking period, for example, the cylinder inner wall temperature, the intake air temperature, the fuel temperature, the engine oil temperature, the cranking speed, the atmospheric pressure, and the like. You can also. Further, in the above-described embodiment, the reduction correction coefficient KR is determined according to the number of fuel injections after the elapse of the estimated cranking period. However, the weight loss correction coefficient KR may be determined according to the time after the elapse of the estimated cranking period.

[0031]

According to the present invention, it is possible to prevent a large amount of unburned HC from being discharged when the engine is started.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a diagram showing a basic fuel injection time at start.

FIG. 3 is a time chart for explaining the present invention.

FIG. 4 is a diagram showing an upper limit fuel injection frequency.

FIG. 5 is a diagram illustrating a weight reduction correction coefficient;

FIG. 6 is a flowchart for calculating a fuel injection time.

FIG. 7 is a flowchart for calculating a fuel injection time in another embodiment.

FIG. 8 is a diagram showing an upper limit integrated fuel injection time.

FIG. 9 is a diagram showing a weight loss correction coefficient in the embodiment of FIG. 7;

[Explanation of symbols]

 4: Combustion chamber 10: Intake branch pipe 14: Fuel injection valve 16: Starter motor 17b: Starter motor switch 27: Water temperature sensor N: Engine speed CINJ: Number of fuel injections ACP: Actual cranking period ECP: Estimated cranking period KR: weight loss correction coefficient

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/06 F02D 45/00

Claims (3)

(57) [Claims] 1. A starting fuel injection amount calculating means for calculating a starting fuel injection amount which is a fuel injection amount at the time of starting the engine, and a reduction correction for calculating a reduction correction coefficient from the number of fuel injections.
Coefficient calculating means, and a reducing means for reducing the fuel injection amount from the starting fuel injection amount with the reducing correction coefficient ,
The decrease correction coefficient decreases as the number of fuel injections increases.
A fuel supply control device for an internal combustion engine that is determined to have a large degree . 2. Ambient environment or engine operation during cranking
Engine after cranking is started based on the
Estimate cranking period until rotation speed starts to increase
After cranking is started, the estimated
Weight loss means starts weight loss action after the elapse of the training period
So that the weight loss correction coefficient is
The number of fuel injections from the end of the
The fuel supply control device for an internal combustion engine according to claim 1, wherein the fuel loss control device is set so that the degree of weight reduction is increased . 3. The machine during an ambient environment or during a cranking period.
Calculates the upper limit integrated fuel injection amount based on the
Calculate integrated fuel injection amount since ranking started
And the integrated fuel injection amount exceeds the upper limit integrated fuel injection amount.
To estimate the period up to the cranking period
The supply fuel control device for an internal combustion engine according to claim 2 , wherein