JP3735933B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine, and more specifically to an internal combustion engine provided with a fuel injection device in an intake system of each cylinder of a multi-cylinder engine.
[0002]
[Prior art]
As a conventional fuel injection control technology at start-up, for example, as disclosed in Japanese Patent Laid-Open No. 5-332177, the injection end timing is always in the same crank angle in accordance with the engine operating state and the fuel injection pulse width. There are those that determine the start time, and those that start injection at the same time for all the cylinders in synchronization with the reference signal of the crank angle only at the start (normal injection start synchronized with the ignition timing).
[0003]
[Problems to be solved by the invention]
However, in such a conventional control technique, when the engine speed at the time of determining the fuel injection and the engine speed at the end of the fuel injection are greatly different (when an initial explosion occurs and the speed increases, etc.) In particular, when the fuel injection pulse width is long and the rotational change is large (see FIG. 15) as at the start, the fuel injection does not end during the intake stroke, and a predetermined amount of fuel may not be sucked.
[0004]
In addition, when injection is started simultaneously for all cylinders, the pressure of the fuel supplied to the fuel injection valve may drop, and a predetermined injection amount for the valve opening time may not be ensured.
[0005]
As a result, engine stability and emissions may deteriorate.
[0006]
The present invention solves such a problem of the prior art, and when the fuel injection pulse width at the start is longer than a predetermined value, it is not the normal fuel injection timing only for a specific cylinder, but the previous fuel. By driving the injector at the same time as the injection timing cylinder, an internal combustion engine capable of ensuring a precise injection amount by making it difficult to cause a drop in fuel pressure because all the cylinders are not simultaneously injected while sucking a predetermined amount of fuel. It aims at providing the fuel-injection control apparatus of an engine.
[0007]
[Means for Solving the Problems]
The present invention has been made paying attention to the problems of such a conventional fuel injection control device for an internal combustion engine. In an internal combustion engine having a fuel injection device in the intake system of each cylinder of a multi-cylinder engine, Crank angle detecting means for detecting the crank angle, cylinder determining means for determining each cylinder, engine operating state detecting means for detecting the operating state of the engine, and fuel injection number detecting means for detecting the number of fuel injections from the start A fuel injection pulse width calculating means for calculating the valve opening time of the injector using at least the result of the engine operating state detecting means, a crank angle detecting means, a cylinder determining means, an engine operating state detecting means, a fuel injection number detecting means, have a fuel injection timing calculating means for calculating a valve opening start timing of the injector by using the output of the fuel injection pulse width calculating means The fuel injection timing calculating means obtains the valve opening start timing of the injector so as to inject into each cylinder in accordance with a predetermined injection sequence from the start of the engine, while the specific cylinder in which the injection from the engine start corresponds to the predetermined number of times. When the fuel injection pulse width is greater than or equal to a predetermined value, the valve opening start timing of the injector in the specific cylinder is set at the same time as the valve opening start timing of the injector in another cylinder whose injection order is earlier than the specific cylinder. It is characterized by that. In addition, the valve opening start timing of injectors in three or more cylinders may be set at the same time.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0009]
FIG. 1 is a block diagram showing a configuration of an embodiment of a fuel injection control device of the present invention.
[0010]
First, the configuration will be described. Crank angle detection means A for detecting the crank angle of the engine, cylinder determination means B for determining each cylinder, various engine states (water temperature, rotation speed, St / Sw signal, intake air amount, etc.) ) To detect the fuel injection frequency from the result of the engine operation state detection means C, and the fuel injection pulse width is calculated from the result of the engine operation state detection means C. The fuel injection pulse width calculating means E and the fuel injection timing calculating means F for calculating the injector drive start timing based on the outputs of the means A to E are used.
[0011]
As described above, according to the present embodiment, normal sequential injection is performed in accordance with the set injection timing and injection pulse width from the start of the engine, but only the injection timing of a specific cylinder is set to that of the previous cylinder. By making it the same as the injection timing, it becomes possible to prevent the fuel injection of the previous cylinder from straddling the intake stroke.
[0012]
FIG. 2 shows injection in a pattern in the present embodiment. As apparent from the comparison with FIG. 15, the fuel injection does not take the closing period of the intake valve.
[0013]
Next, in order to describe the present embodiment in more detail, the operation will be described based on the control flowcharts of FIGS.
[0014]
First, the flow of FIG. 3 will be described. This routine is performed in time synchronization or angle synchronization, the fuel injection pulse width in step S1 (details are shown in steps S10 to S13 in FIG. 4), and the fuel injection cylinder timing in step S2 (details in FIG. 5). It is determined whether or not it is time to perform fuel injection in step S3 using the result calculated in steps S20 to S23.
[0015]
In step S4, it is determined whether or not the previous simultaneous injection has been performed. If the simultaneous injection flag is set, it is cleared and the process ends. If not set, the process proceeds to step S5.
[0016]
In step S5, in order to determine whether or not there is a possibility of simultaneous injection, it is confirmed how many injections have been completed up to the present time. (Determining whether INJ = 2)).
[0017]
In step S6, it is determined whether or not simultaneous injection is necessary. This is because when the injection pulse width is shorter than the predetermined value, there is no particular problem because the injection is terminated while the intake valve is opened even if the injection is started as usual in step S8.
[0018]
If simultaneous injection is determined in the determination so far, injection is performed also to the cylinders in the injection order next to the cylinders that should be injected at that timing in Step S7 (injection order # 1- # 3- # 4- #). In the case of the 2-cylinder No. 2, the fuel is also injected into # 3 at the injection timing of # 1).
[0019]
If simultaneous injection is performed, a flag indicating that simultaneous injection has been performed is set in step S10 so that the next fuel injection is not performed. In step S12, the counter (INJ) is incremented by 2 and the number of injections is counted. If it is determined in step S4 that the previous simultaneous injection has been performed, it is not necessary to perform the injection at this timing, so the simultaneous injection flag is cleared in step S11 to prepare for the next injection.
[0020]
Step S9 is only described for comparison with steps S7 and S8, and no special processing is performed.
[0021]
FIG. 4 shows an example of fuel injection pulse width calculation. In FIG. 4, in step S10, the basic value (TCST) of the pulse width is obtained from the water temperature (Tw) by reading the value assigned in the table as shown in FIG. 9, and in step S11, the rotation correction factor is obtained from the table in FIG. (TCSN) is obtained from the engine speed (Ne), and in step S12, the time correction factor (TKCS) is obtained from the St / Sw ON time from the table of FIG. In step S13, the starting fuel injection pulse width (TIST) is calculated by the following equation using the results obtained in steps S10 to S12. TS is a battery voltage correction amount.
[0022]
TIST = TCST × TCSN × TKCS + TS
FIG. 5 shows the case of injection end management as an example of the fuel injection cylinder / timing calculation. In FIG. 5, in step S20, the cylinder to inject fuel is determined (cylinder discrimination is executed in Ref synchronization, ADV synchronization, etc., and the result is used), and the injection timing is determined in step S21 and thereafter. In step S21, the injection end angle (TITM) is calculated from the engine speed (Ne). The end angle of spraying (TITM) may be a constant crank angle. In step S22, an angle converted value (MTIA) of the injection pulse width (TIST) is obtained from the engine speed (Ne). In step S23, the fuel injection start timing (TITM-MTIA) is obtained.
[0023]
FIG. 6 shows a system diagram in the case of 4 cylinders, FIG. 7 shows an example of sequential injection from the start in the case of 6 cylinders, and FIG. 8 shows an example of simultaneous injection in all the cylinders at the start in the case of 6 cylinders. Indicates.
[0024]
Next, other embodiments of the present invention will be described.
[0025]
In the case of a four-cylinder engine, when the pulse width is long and the rotation increase is large, not only the next one cylinder but also two-cylinder simultaneous injection is performed (three-cylinder simultaneous injection).
[0026]
When the fuel injection pulse width becomes long (when the water temperature is low), the fuel supply is not in time just by the simultaneous injection of one cylinder, so the two cylinders are simultaneously injected. In this case, the number of injectors driven at the same time increases and the fuel pressure is likely to decrease. However, since the second cycle, the fuel pressure is considered to have risen sufficiently. We can expect supply.
[0027]
FIG. 12 shows the injection in this pattern, and FIG. 16 shows the injection in the conventional spray end management.
[0028]
In the case of a six-cylinder engine, since the number of cylinders that will receive the first fuel injection after the occurrence of the rotation increase is larger than that in the case of four cylinders, simultaneous injection can be performed on the third to sixth fuel injection cylinders from the start.
[0029]
As a result, fuel injection can be terminated while the intake valve is open (IVO), and the number of injectors that are simultaneously driven is small, so there is little possibility of a decrease in fuel pressure. As a result, it can be expected to secure an accurate fuel injection amount, so that stable combustion can be expected.
[0030]
FIG. 13 shows injection in this pattern, and FIG. 17 shows injection in conventional spray end management.
[0031]
In the case of a six-cylinder engine, when the rotational increase is large or when the fuel injection pulse width is long, simultaneous injection can be performed on the second to sixth fuel injection cylinders. A similar effect can be expected.
[0032]
FIG. 14 shows injection in this pattern, and FIG. 18 shows injection in conventional spray end management.
[0033]
【The invention's effect】
As described above, according to the present invention, the fuel injection is taken into the intake by driving the injector at the same time as the cylinder at the previous fuel injection timing instead of the normal fuel injection timing only for a specific cylinder. Since it is terminated immediately before or during valve opening, it can be expected that a predetermined amount of fuel is inhaled.
[0034]
Further, since the simultaneous injection of all cylinders is not performed, it is difficult to reduce the fuel pressure. Therefore, an effect of ensuring an accurate injection amount for each cylinder, which is a merit of sequential injection, can be expected.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a fuel injection control device according to an embodiment of the present invention.
FIG. 2 is a diagram showing injection in a pattern according to the embodiment of the present invention.
FIG. 3 is a flowchart illustrating control of fuel injection in the embodiment of the present invention.
FIG. 4 is a flowchart illustrating start-time fuel injection pulse width TIST according to the embodiment of the present invention.
FIG. 5 is a flowchart illustrating fuel injection timing in the embodiment of the present invention.
FIG. 6 is a system diagram in the case of four cylinders in the embodiment of the present invention.
FIG. 7 is a diagram showing an example of sequential injection from the start in the case of 6 cylinders in the embodiment of the present invention.
FIG. 8 is a diagram showing an example in which all cylinders are simultaneously injected at the start of the six cylinders in the embodiment of the present invention.
FIG. 9 is a diagram showing a relationship between a basic value of pulse width (TCST) and S water temperature (Tw) in the embodiment of the present invention.
FIG. 10 is a diagram showing a relationship between a rotation correction factor (TCSN) and an engine speed (Ne) in the embodiment of the present invention.
FIG. 11 is a diagram showing a relationship between time correction factor (TKCS) and St / Sw ON time according to the embodiment of the present invention.
FIG. 12 is a diagram showing injection in a pattern according to another embodiment of the present invention.
FIG. 13 is a diagram showing injection (6 cylinders) in a pattern according to another embodiment of the present invention.
FIG. 14 is a diagram showing injection (6 cylinders) in a pattern according to another embodiment of the present invention.
FIG. 15 is a diagram showing injection in conventional spray end management.
FIG. 16 is a view showing injection in conventional spray end management.
FIG. 17 is a diagram showing injection (6-cylinder) in conventional injection end management.
FIG. 18 is a view showing injection (6 cylinders) in conventional spray end management.
[Explanation of symbols]
A Crank angle detection means B Cylinder discrimination means C Engine operating state detection means D Fuel injection number detection means E Fuel injection pulse width calculation means F Fuel injection timing calculation means

Claims (2)

In an internal combustion engine provided with a fuel injection device in the intake system of each cylinder of a multi-cylinder engine,
Crank angle detecting means for detecting the crank angle of the engine;
Cylinder discriminating means for discriminating each cylinder;
Engine operating state detecting means for detecting the operating state of the engine;
Fuel injection number detecting means for detecting the number of fuel injections from the start time, fuel injection pulse width calculating means for calculating the valve opening time of the injector using at least the result of the engine operating state detecting means,
Fuel injection timing calculating means for obtaining the valve opening start timing of the injector using output results from the crank angle detecting means, cylinder determining means, engine operating state detecting means, fuel injection number detecting means and fuel injection pulse width calculating means; have a,
The fuel injection timing calculation means obtains the valve opening start timing of the injector so as to inject into each cylinder according to a predetermined injection sequence from the start of the engine,
When the fuel injection pulse width of a specific cylinder that has been injected a predetermined number of times since the start of the engine is greater than or equal to a predetermined value, the opening timing of the injector in the specific cylinder A fuel injection control device for an internal combustion engine, wherein the fuel injection control device is set at the same time as a valve opening start timing of an injector in a cylinder . 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection timing calculation means sets the valve opening start timing of the injectors in three or more cylinders at the same time.

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