Engine fuel injection control system

The present invention relates to an engine having an in-cylinder injector for directly injecting fuel into a cylinder and an intake passage injector for injecting fuel into an intake passage, and the present invention relates to a fuel injection control device for an engine that controls fuel injection by the in-cylinder injector.

As a method of injecting and supplying fuel into the cylinder of an engine, a method of injecting fuel into an intake passage such as an intake port (intake passage injection) has been widely adopted. In this intake passage injection, fuel is injected upstream of the intake valve at the cylinder inlet. The fuel injected in this way is sucked into the cylinder in a state of being mixed with air substantially uniformly in the suction stroke.

On the other hand, in recent years, unlike such an injection method, a method of directly injecting fuel into the cylinder (in-cylinder injection) has been proposed. In this in-cylinder injection, the injection pressure is compared with the injection pressure in the intake passage injection.<u style="single">Comparison</u>The fuel is set high and is injected into the combustion chamber in a atomized state where it is easily vaporized. In such in-cylinder injection, the temperature in the combustion chamber is lowered by the heat of vaporization when the atomized fuel is vaporized, and the intake efficiency is improved, so that the engine output can be improved.

By the way, in the in-cylinder injection method, since the tip of the injector is exposed in the cylinder, there is a possibility that a deposit may adhere to the vicinity of the injection hole where the fuel is injected. When the deposit adheres in this way, the fuel injection amount decreases and, as shown in FIG. 4, the spray shape changes with time, so that the combustion state deteriorates due to these.

Therefore, conventionally, even if the engine operating state is in the region where the in-cylinder injection is performed, the fuel injection method is forcibly switched from the in-cylinder injection to the intake passage injection at regular intervals (Patent Document 1). .. By forcibly switching the fuel injection method in this way, the in-cylinder injector<u style="single">To</u>It is possible to raise the temperature of the tip portion of the sill and periodically burn off the deposit attached to the tip portion to remove it.<patcit num="1"><text>Japanese Patent Application Laid-Open No. 63-138120</text></patcit>

<p> However, in the method of switching the injection method at predetermined time intervals in this way, the injection method is switched even when the deposit is not actually attached, and appropriate switching is always performed according to the deposit amount. I can't do it. In addition, since the in-cylinder injection is stopped and completely switched to the intake passage injection, the intake efficiency is increased by lowering the temperature in the combustion chamber while the intake passage injection is being executed. The advantage of injection cannot be obtained.</p><p> Further, inconveniences such as a decrease in the fuel injection amount and a change in the spray shape in the in-cylinder injection are not limited to those caused by deposit adhesion, and the same applies to, for example, when the injection pressure in the in-cylinder injection decreases due to some abnormality. Can occur in.</p><p> An object of the present invention is that even in a situation where it is difficult to normally execute fuel injection by an in-cylinder injector such as deposit adhesion, a combustion state is achieved by appropriately setting a fuel injection method according to the situation. The purpose is to secure as much as possible the effect of increasing the intake efficiency by the in-cylinder injection while suppressing the deterioration of the fuel.</p>

<p> Hereinafter, means for achieving the above object and its action and effect will be described. The invention according to claim 1 includes an in-cylinder injector 17 that directly injects fuel into the cylinder 12 and an intake passage injector 18 that injects fuel into the intake passage 15, and injects fuel from the injectors 17 and 18 into a predetermined injection amount. In the fuel injection control device of the engine controlled by the ratio, the detection means for detecting the degree of deviation between the actual injection amount of the in-cylinder injector 17 and the target injection amount, and the fuel injection of the in-cylinder injector 17 whose engine operating state is the engine operating state are detected. When in the area to run<u style="single">Leave</u>, The degree of dissociation detected by the detection means<u style="single">,Previous</u>When the deposit adhering to the injection hole of the injector in the cylinder is burnt out and is smaller than the degree indicating that the adverse effect on the fuel injection can be ignored, the degree of deviation detected is defined as the injection amount. It is provided with a setting means to be reflected in the ratio setting.</p><p> Further, the invention according to claim 2 is<u style="single">When the engine operating state is in the region where the fuel injection of the in-cylinder injector is executed, the deposit is attached to the injection hole of the in-cylinder injector.</u>The setting means increases the injection amount ratio of the intake passage injector 18 based on the detection result that the actual injection amount of the in-cylinder injector detected by the detection means tends to be lower than the target injection amount. There is.</p><p> In the configuration described in each of these claims, when the degree of deviation between the actual injection amount of the in-cylinder injector 17 and the target injection amount is detected and the engine operating state is in the region where the fuel injection of the in-cylinder injector 17 is executed. , The injection amount ratio of the injectors 17 and 18 is set based on the detected deviation degree so that the fuel injection of the intake passage injector 18 is executed at the same time as the fuel injection of the in-cylinder injector 17. .. Specifically, the degree of dissociation detected by the detection means is<u style="single">,Previous</u>When the deposit adhering to the injection hole of the injector in the cylinder is burnt out and is smaller than the degree indicating that the adverse effect on the fuel injection can be ignored, the degree of deviation detected is defined as the injection amount. It is reflected in the ratio setting.<u style="single">As a result, when the adhered deposit is eliminated for some reason, the fuel injection amount of the in-cylinder injector 17 can be increased accordingly, and the effect of increasing the intake efficiency by the in-cylinder injection can be ensured. become.</u></p><p> In particular, in the configuration according to claim 2, a deposit is made by increasing the injection amount ratio of the intake passage injector 18 based on the detection result that the actual injection amount of the in-cylinder injector 17 tends to be lower than the target injection amount. Even if a decrease in flow rate occurs due to adhesion or the like, this can be compensated for by fuel injection of the intake passage injector 18.<u style="single">Even if the actual injection amount of the in-cylinder injector 17 is less than the target injection amount due to the deposit of the in-cylinder injector 17 or the like, it is appropriate according to the situation. By setting the fuel injection method to, it is possible to suppress the deterioration of the combustion state and to secure the effect of increasing the intake efficiency by the in-cylinder injection as much as possible.</u></p><p> Here, the "region in which the engine operating state executes fuel injection of the in-cylinder injector 17" is a region in which fuel injection is executed only by the in-cylinder injector 17, and an intake passage in addition to the in-cylinder injector 17. The area where the fuel injection of the injector 18 is executed is also included.</p><p> According to the third aspect of the present invention, in the fuel injection control device for the engine according to the first or second aspect, the detection means determines the degree of deviation based on the feedback correction amount of the air-fuel ratio control applied to the fuel injection of the in-cylinder injector 17. Is detected, and the setting means sets the injection amount ratio based on the feedback correction amount.</p><p> In the region where fuel injection is performed only by the in-cylinder injector 17, the target injection amount of the in-cylinder injector 17 is the same as the basic injection amount set based on the engine operating state. When the actual injection amount of the in-cylinder injector 17 is different from the basic injection amount in such a region, the feedback correction amount is set so that the deviation between them becomes small in the air-fuel ratio control. Further, the degree of deviation between the actual injection amount of the in-cylinder injector 17 and the target injection amount in the region where the intake passage injector 18 is used in addition to the in-cylinder injector 17 is also reflected in the feedback correction amount. Therefore, this feedback correction amount is a value that reflects the tendency of the deviation between the actual injection amount of the injectors 17 and 18 and the basic injection amount.</p><p> According to the above configuration, since the injection amount ratio of each injector is set based on the feedback correction amount, the injection amount ratio is set according to the inconvenience situation that occurs in the in-cylinder injector such as deposit adhesion. You will be able to set it.</p><p> Claim<u style="single">4</u>In the described invention, claim<u style="single">3 notes</u>In the fuel injection control device of the engine, the setting means variably sets the injection amount ratio according to the magnitude of the correction amount when setting the injection amount ratio based on the correction amount.</p><p> According to the same configuration, in the case where the in-cylinder injector 17 cannot perform its original function due to the adhesion of a deposit, the injection amount ratio is more appropriate according to the degree of deterioration of the function. Will be able to be set to.</p><p><u style="single"> In the invention according to claim 5, the degree of divergence is a learning value learned according to a steady divergence tendency between the actual injection amount of the in-cylinder injector 17 and the target injection amount. According to such a configuration, when the degree of deviation is reflected in the setting of the injection ratio, it is possible to suppress the influence of temporary disturbance such as a sudden change in the engine operating state on the injection amount ratio. The injection amount ratio can be set appropriately.</u> Also<u style="single">, Example</u>For example, as according to the invention of claim 6, the setting means is<u style="single">After reflecting the detected degree of deviation in the setting of the injection amount ratio</u>The learning value<u style="single">Absolute value of</u>To<u style="single">Decrease</u>, Etc. can be adopted<u style="single">。</u></p>

An embodiment of the present invention will be described in detail with reference to FIGS. 1 to 4. FIG. 1 is a schematic view showing a fuel injection control device for an engine according to the present embodiment. A piston 13 is provided in the cylinder 12 of the engine 11, and an intake passage 15 and an exhaust passage 16 are connected to a combustion chamber 10 partitioned by the piston 13 and the like.

The intake passage 15 is provided with an intake passage injector 18 that injects fuel into the passage 15. On the other hand, the cylinder 12 is provided with an in-cylinder injector 17 so that its tip is exposed in the combustion chamber 10, and fuel directly enters the combustion chamber 10 from an injection hole (not shown) of the in-cylinder injector 17. Be jetted. The fuel injected from the intake passage injector 18 or the in-cylinder injector 17 is mixed with the intake air introduced into the combustion chamber 10 through the intake passage 15. Then, the air-fuel mixture is burned in the combustion chamber 10 by the ignition of the spark plug 14, and then discharged from the combustion chamber 10 to the exhaust passage 16.

Further, the intake passage 15 is provided with an air flow meter 22 for detecting the amount of intake air. On the other hand, the exhaust passage 16 is provided with an oxygen sensor 23 for detecting the oxygen concentration of the exhaust gas. In addition, a rotation speed sensor 24 for detecting the rotation speed (engine rotation speed) of the engine 11 is provided in the vicinity of the crankshaft (not shown). The detection signals of each of these sensors 22 to 24 are input to the control unit 21 of the engine 11. Based on these detection signals, the control unit 21 calculates the amount of intake air (intake air amount) introduced into the combustion chamber 10 per stroke, the fuel injection amount, the air-fuel ratio, and the like. Then, the control unit 21 sets the fuel injection method based on the engine operating state such as the engine rotation speed and the engine load (intake air amount or fuel injection amount). Specifically, the fuel injection method is set to either fuel injection using only the intake passage injector 18, fuel injection using only the in-cylinder injector 17, or fuel injection using both injectors 17 and 18. In particular, when the engine load is high, the fuel injection method is set so that fuel is injected at least from the in-cylinder injector 17 in order to improve the intake efficiency by fuel injection.

Further, the control unit 21 calculates the basic injection amount based on the operating state of the engine 11 so that the air-fuel ratio becomes the target air-fuel ratio (usually the theoretical air-fuel ratio), and further corrects this according to the oxygen concentration of the exhaust gas. The so-called air-fuel ratio control is performed. The execution procedure of this air-fuel ratio control will be described below.

In this air-fuel ratio control, the basic injection amount QB is first calculated so that the air-fuel ratio becomes the theoretical air-fuel ratio based on the engine operating state such as the engine load (for example, the intake air amount) and the engine rotation speed. Here, since the fuel injection system is affected by various disturbances, it may not be possible to perform fuel injection in accordance with the actual engine operating state depending on the calculated basic injection amount QB. For example, in the case of transient operation in which the intake air amount changes significantly, such as during acceleration / deceleration of the engine 11, it is assumed that the basic injection amount QB is calculated based on the detected intake air amount and fuel injection is executed based on this. However, the actual air-fuel ratio may not match the theoretical air-fuel ratio. In addition, if a deposit adheres to the tip of the in-cylinder injector 17, especially its injection hole (not shown) and fuel is not injected normally (see Fig. 4, deposit attachment to injector 30), fuel The same tendency occurs even when the injection pressure of the in-cylinder injector 17 drops due to an abnormality in the pumping system.

Therefore, in the air-fuel ratio control, feedback control is generally performed to compensate for the influence of these disturbances. That is, the control unit 21 calculates the correction coefficient FAF (initial value = "1.0") based on the deviation between the actual air-fuel ratio and the theoretical air-fuel ratio calculated based on the detection signal of the oxygen sensor 23, and this correction coefficient. By multiplying the FAF by the basic injection amount QB, the fuel injection amount is corrected so that the above deviation becomes small.

Specifically, the correction coefficient FAF is lower than the initial value "1.0" so that the fuel injection amount is reduced in the so-called rich state where the oxygen concentration in the exhaust is lower than the reference value corresponding to the stoichiometric air-fuel ratio. Set to a small value. On the other hand, the correction coefficient FAF is set to a value larger than "1.0" so that the fuel injection amount is increased in the so-called lean state where the oxygen concentration is high.

Further, in this feedback control, the steady tendency of the above correction coefficient FAF is learned, and the learning value KG for reflecting the learning result in the correction of the fuel injection amount is calculated. This learning value KG is a correction coefficient (initial value = "0") that further corrects the basic injection amount QB corrected by the correction coefficient FAF based on the calculation formula [QB / FAF / (1 + KG)]. This is an index value indicating a steady deviation tendency between the actual injection amount and the basic injection amount QB.

Specifically, the average value FAFAVE of the correction coefficient FAF in a predetermined period is calculated, and when this average value FAFAVE exceeds the predetermined lean judgment value (&gt; 1.0), the predetermined amount α is added to the learning value KG. At the same time, the same predetermined amount α is subtracted from the correction coefficient FAF. On the other hand, when the average value FAFAVE is less than the predetermined rich determination value (&lt;1.0), the predetermined amount α is subtracted from the learning value KG and the predetermined amount α is added from the correction coefficient FAF. Incidentally, when the actual air-fuel ratio is substantially the same as the theoretical air-fuel ratio and the average value FAFAVE of the correction coefficient FAF is between the above judgment values, the learning value KG is not updated and at that time. The learning value KG of is maintained.

Here, for example, if there is a tendency that the actual injection amount of the injectors 17 and 18 is always lower than the basic injection amount QB due to the adhesion of the deposit of the injector 17 in the cylinder, the learning value KG is that. The value becomes larger than the initial value "0" by the amount corresponding to the decreasing tendency. On the other hand, when the deposit adhering to the injection hole of the in-cylinder injector 17 is burnt out and normal fuel injection can be executed by the in-cylinder injector 17, the above learning value KG gradually decreases. .. Therefore, it is possible to monitor the degree of deposit adhesion to the injection hole of the in-cylinder injector 17 based on this learning value KG.

Focusing on this point, the control device according to the present embodiment pays attention to this point, and when the engine operating state is at least in the region where the fuel injection of the in-cylinder injector 17 is executed, the intake passage injector 18 is combined with the fuel injection by the in-cylinder injector 17. The injection amount ratios of the injectors 17 and 18 are variably set according to the degree of deposit adhesion so that the fuel injection of the above is executed. Hereinafter, such fuel injection control will be described.

FIG. 2 is a flowchart showing a processing procedure related to this fuel injection control. The control unit 21 repeatedly executes a series of processes shown in this flowchart with a predetermined control cycle. In the following, a case where the series of processes is started from the state where the engine operating state is in the region where the fuel injection is executed only by the in-cylinder injector 17 will be described.

In step S101, the control unit 21 calculates a correction coefficient FAF for feedback control of the actual injection amount of the in-cylinder injector 17 so that the air-fuel ratio becomes the stoichiometric air-fuel ratio, and further, based on the average value FAFAVE of the correction coefficient FAF. Calculate the learning value KG.

Next, in step S102, the control unit 21 compares the learning value KG with the respective determination values KGINC and KGDEC, and determines whether or not the following conditions 1 and 2 are satisfied. Condition 1 KG&gt; KGINC Condition 2 KG &lt;KGDEC Here, one of the above judgment values KGINC has a deposit on the injection hole of the in-cylinder injector 17.<u style="single">Dress up</u>The adverse effect on fuel injection cannot be ignored (Condition 1), and the other judgment value, KGDEC, is such that the deposit attached to the injection hole of the in-cylinder injector 17 is burned out and the adverse effect on fuel injection can be ignored. It is a judgment value for judging each of the facts (condition 2). Therefore, through the processing of steps S101 and S102, the degree of deviation between the actual injection amount of the in-cylinder injector 17 and its target amount is detected.

If neither of the conditions 1 and 2 is satisfied in step S102, the control unit 21 temporarily ends the process. On the other hand, if either of the conditions 1 and 2 is satisfied, that is, the deposit is attached to the injection hole of the in-cylinder injector 17 and the adverse effect on the fuel injection cannot be ignored, or the deposit is the same. When is burnt down and the adverse effect on fuel injection becomes negligible, the control unit 21 shifts the process to step S103.

Then, in the following steps S103 and 104, the injection amount ratio KPINJ is updated through the following calculation formulas (1) and (2). KPINJ KPINJ + KG ... (1) KG "0" ... (2) Injection amount ratio of the above equation (1) KPINJ is the amount of fuel injected by the intake passage injector 18 of the basic injection amount QB. It is a ratio, and the initial value is set to "0".

In these steps S103 and 104, if a deposit adheres to the injection hole of the in-cylinder injector 17 and the fuel injected from the in-cylinder injector 17 tends to be less than when it is normal, the learning value KG is a positive value. It becomes. Therefore, the injection amount ratio KPINJ is set to a large value by the current learning value KG by the above calculation formulas (1) and (2), the fuel injected from the intake passage injector 18 increases, and the fuel injected from the in-cylinder injector 17 increases. The amount of fuel injected will be reduced.

On the other hand, in steps S103 and 104, when the deposit adhering to the injection hole of the in-cylinder injector 17 is burnt down and the state shifts to a state in which fuel can be normally injected from the in-cylinder injector 17, the learning value KG Is a negative value. Therefore, the injection amount ratio KPINJ is reduced by the above calculation formulas (1) and (2), the amount of fuel injected from the intake passage injector 18 is reduced, and the amount of fuel injected from the in-cylinder injector 17 is increased. It becomes.

After calculating the injection amount ratio KPINJ and the learning value KG in this way, in steps S105 and 106, the control unit 21 controls the fuel injection amount Q1 of the in-cylinder injector 17 based on the following calculation formulas (3) and (4). In addition, the fuel injection amount Q2 of the intake passage injector 18 is calculated.

Q1 QB FAF (1 + KG) ... (3) Q2 QB KPINJ ... (4) In this way, each injector 17, depending on the state of deposit attached to the injection hole of the in-cylinder injector 17. After calculating the fuel injection amounts Q1 and Q2 of 18, the control unit 21 ends this series of processes. In the above, the fuel injection method using only the in-cylinder injector 17 at the initial stage of the processing has been described, but when fuel injection is performed by the intake passage injector 18 in addition to the in-cylinder injector 17, the same applies to the above. The degree of deviation between the actual injection amount of the in-cylinder injector 17 and its target amount can be detected through steps S101 and S102 of.

Next, one aspect of the fuel injection control will be described with reference to the timing chart of FIG. In this timing chart, a case where a deposit gradually adheres to the injection hole of the in-cylinder injector 17 and the adhered deposit is burnt down after a predetermined period is taken as an example.

In the initial period of timings t1 to t2, fuel injection is executed only by the in-cylinder injector 17. During this period, a deposit gradually adheres to the injection hole of the in-cylinder injector 17, and the actual fuel injection amount decreases due to the influence of the deposit. Therefore, the learning value KG increases to compensate for this.

At the timing t2, neither the above condition 1 nor the condition 2 (step S102) is satisfied, so the injection amount ratio KPINJ is kept at the initial value 0. Therefore, the fuel injection form at this time is a form in which only the in-cylinder injector 17 is continuously used. However, the learning value KG gradually increases as the amount of deposit adhered increases.

Then, when condition 1 is satisfied at timing t3 (step S102: condition 1 is satisfied), the injection amount ratio KPINJ from the intake passage injector 18 increases from the initial value "0" by the current learning value KG1. It becomes "KPIN J1". As a result, fuel injection by the intake passage injector 18 is started. On the other hand, the injection amount from the in-cylinder injector 17 is reduced by the amount injected from the intake passage injector 18.

At timing t4, as with timing t2, neither condition 1 nor condition 2 (step S102) is satisfied. Therefore, at timings t3 to t5, there is no change in the fuel injection amount injected by the intake passage injector 18. On the other hand, the fuel injection amount injected from the in-cylinder injector 17 increases as the learning value KG increases.

The learning value KG2 at the timing t5 exceeds KGINC and satisfies the condition 1 of the above step S102. Therefore, the injection amount ratio from the intake passage injector 18 is increased by the learning value KG2 at this time. On the other hand, the fuel injection ratio from the in-cylinder injector 17 is reduced by KG2.

At timing t6, neither of the above conditions 1 and 2 (step S102) is satisfied, so the injection amount ratio by the intake passage injector 18 remains unchanged at KPINJ2. Further, the injection amount of the in-cylinder injector 17 is not changed because the deposit amount does not change between t6 and t7 and the learning value KG is kept constant.

The fuel injection amount of the in-cylinder injector 17 increases when the deposit disappears for some reason such as burning or falling off, for example, when the deposit amount decreases as seen between timings t7 to t8. Therefore, the learning value KG is reduced in order to reduce the fuel injection amount of the in-cylinder injector 17 to the reference value. The learning value KG3 at the timing t8 is lower than the judgment value KGDEC, and the above condition 2 is satisfied. Therefore, at timing t8, the learning value KG3 is added to the injection amount ratio KPINJ from the intake passage injector 18. Since the learned value KG3 is a negative value, the fuel injection amount from the intake passage injector 18 decreases. On the other hand, the injection ratio of the in-cylinder injector 17 is increased by subtracting the learning value KG3.

Furthermore, the amount of deposit attached continues to decrease, and the learning value KG4 at the timing t9 after the deposit is completely taken is also lower than the judgment value KGDEC. Therefore, the injection amount ratio of the intake passage injector 18 is further reduced by KG4. As a result, KPINJ becomes 0, and the fuel injection method is changed to inject the total amount of fuel from the in-cylinder injector 17 without using the intake passage injector 18.

As described above, in the present invention, the fuel injection form is changed by the learning value KG representing the combustion state at that time. In the fuel control of the present invention, since the fuel injection method is appropriately changed according to the engine operating state and the states of the injectors 17 and 18, the inside of the cylinder due to the cooling effect is avoided while avoiding the adverse effect of deposit adhesion by the in-cylinder injector 17. The advantage of increasing the intake amount of the injector 17 can be obtained according to the state at that time.

Furthermore, this feedback modifies the fuel injection ratio KPINJ between the in-cylinder injector 17 and the intake passage injector 18 using the learning value KG. This prevents unnecessary switching between the in-cylinder injector 17 and the intake passage injector 18, and also abruptly when the fuel injection ratio KPINJ should be changed abruptly according to the magnitude of the learning value KG. If it should be changed slowly, it can be changed slowly. Therefore, the injectors 17 and 18 can be set more quickly to the fuel injection ratio suitable for the situation at that time than the method of changing by a constant amount.

Although suitable embodiments have been described, the configuration of the present invention is not limited thereto. For example, in each process shown in the flowchart of FIG. 2, there are the following alternative embodiments. -In this embodiment, the learning value KG is used as a parameter for monitoring the degree of deposit adhesion, but only the correction coefficient FAF may be used, or both of these feedback correction amounts FAF and KG may be used. You may. This is because the effect of the present invention can be obtained if the fuel injection amount from each of the injectors 17 and 18 can be changed in a form suitable for the situation by using the feedback correction amount.

-In step S102, there are KGINC and KGDEC as judgment values to be compared with the learning value KG, but the absolute values of KGINC and KGDEC may be the same or different.

-In step S103 of changing the injection amount ratio KPINJ from the intake passage injector 18, the learning value KG is added to the injection amount ratio KPINJ. For example, the learning value KG is multiplied by a predetermined coefficient. It is also possible to add only a part of the above to the injection amount ratio KPINJ.

-As step S104, the configuration in which the learning value after changing the injection amount ratio KPINJ is set to 0 was explained. The learning value after changing the injection amount ratio KPINJ needs to be reduced in its absolute value, but it does not necessarily have to be reduced to 0.

<figref num="1">The block diagram which shows the schematic structure of the fuel injection control device.</figref><figref num="2">The flowchart which shows the outline of the fuel amount control by this invention.</figref><figref num="3">A timing chart showing the correlation between the deposit state and the fuel amount control of the present invention.</figref><figref num="4">The side view of the injector injection port which shows the spray change by the deposit adhesion of the in-cylinder injection injector.</figref>

Code description

KG, KG2, KG3, KG4 ... Learning value, KPINJ ... Injection amount ratio, 11 ... Engine, 15 ... Intake passage, 17 ... In-cylinder injector, 18 ... Intake passage injector, 21 ... Control unit (detection means, setting means).