JP2012189061A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine that excellently avoids the occurrence of pre-ignition regarding a control device for an internal combustion engine.SOLUTION: In a routine shown in Fig.4, at first, start timing CAof pre-ignition suppression injection is set (a step 100). Subsequently, additional driving of an injector 14 is started and an injection flow rate Qis operated from differential pressure ΔP between cylinder internal pressure Pand fuel pressure P(a step 110). Next, an operation value of the injection flow rate Qis integrated and an actual injection quantity Qis calculated (a step 120). Then, it is determined whether the calculated actual injection quantity Qis larger than a target injection quantity Q(a step 130). When determined that the actual injection quantity Qis larger than the target injection quantity Q, the additional driving of the injector 14 is stopped (a step 140).

Description

  The present invention relates to an internal combustion engine control device, and more particularly to an internal combustion engine control device that suppresses the occurrence of pre-ignition.

  In an internal combustion engine that ignites and burns a mixture of fuel and air with sparks of a spark plug, so-called preignition (hereinafter also referred to as “preg”) may occur. Plague refers to abnormal combustion in which an air-fuel mixture in a cylinder self-ignites before ignition by a spark plug.

  Conventionally, as a technique for suppressing the occurrence of the prag, for example, in Patent Document 1, for example, the deviation between the model value of the in-cylinder pressure and the measured value is used to predict the occurrence of the prag, and when the occurrence is predicted, the injector A control device for an internal combustion engine is disclosed in which fuel is additionally injected to inject fuel into a cylinder. If fuel is injected when the occurrence of plague is predicted, the inside of the cylinder can be cooled by the latent heat of vaporization, so that the occurrence of plague can be delayed and avoided.

  Further, for example, in Patent Document 4, when it is determined that pre-ignition has occurred in an intake stroke of an internal combustion engine, in the compression stroke before ignition of the next cycle, the injector is additionally driven to drive fuel into the cylinder. A control device for an internal combustion engine that injects the fuel into the inside is disclosed. Plague is likely to occur in the compression stroke that accompanies an increase in the pressure in the cylinder. Therefore, if fuel is injected in the compression stroke before ignition, the occurrence of plague can be avoided more effectively.

JP 2010-071284 A JP 2003-206796 A JP-A-2005-009457 JP-A-11-159368

  By the way, in Patent Document 1, the amount of fuel injected when the injector is additionally driven is set to a constant value from 10% to 200% of the amount of fuel injected during the normal drive. However, as described above, the compression stroke is accompanied by an increase in the pressure in the cylinder. If the increase is not taken into account, there is a possibility that the set fuel amount cannot be accurately injected during the additional drive of the injector. . In this regard, Patent Document 4 does not disclose a specific method for accurately injecting the set fuel amount in the compression stroke before ignition. For these reasons, the technology disclosed in the above-mentioned patent document cannot sufficiently prevent the occurrence of pre-ignition, which may lead to deterioration of drivability and engine damage.

  The present invention has been made to solve the above-described problems. That is, an object of the present invention is to provide a control device for an internal combustion engine that can favorably avoid the occurrence of pre-ignition.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
Fuel injection means for injecting fuel into a cylinder of the internal combustion engine;
Fuel pressure acquisition means for acquiring the pressure of the fuel supplied to the fuel injection means;
In-cylinder pressure acquisition means for acquiring the in-cylinder pressure of the internal combustion engine;
An operation control means for temporarily operating the fuel injection means when occurrence of pre-ignition is predicted;
When the fuel injection means is operated by the operation control means, the difference between the fuel pressure acquired by the fuel pressure acquisition means and the in-cylinder pressure acquired by the in-cylinder pressure acquisition means is used. An operation end timing control means for controlling the operation end timing;
It is characterized by providing.

According to a second invention, in the first invention,
The operation end timing control means includes
An actual injection amount calculating means for calculating an actual injection amount during operation of the fuel injection means, using the differential pressure;
An injection amount comparison means for comparing the actual injection amount calculated by the actual injection amount calculation means with a target injection amount as a target value of fuel to be injected during operation of the fuel injection means;
An operation stopping means for stopping the operation of the fuel injection means when the actual injection amount calculated by the actual injection amount calculation means exceeds the target fuel amount;
It is characterized by providing.

  According to the first invention, when the fuel injection unit is operated by the operation control unit, the differential pressure between the fuel pressure acquired by the fuel pressure acquisition unit and the in-cylinder pressure acquired by the in-cylinder pressure acquisition unit is obtained. It is possible to control the operation end timing of the fuel injection means. The amount of fuel injected during the operation of the fuel injection means changes from time to time according to the differential pressure. Therefore, if the differential pressure is used, it is possible to accurately calculate the amount of fuel to be injected. Therefore, the operation end timing of the fuel injection means can be controlled with high accuracy, and the occurrence of pre-ignition can be favorably avoided.

  According to the second invention, the amount of fuel actually injected during the operation of the fuel injection unit is calculated, and when the fuel amount exceeds the target fuel amount, the operation of the fuel injection unit is controlled by the operation stop unit. You can stop. Since the target fuel amount is a target value of the amount of fuel to be injected during the operation of the fuel injection means, if the fuel injection means is operated until the target fuel amount is exceeded, the fuel is used without excess or deficiency, The occurrence of plague can be avoided well. Further, since it becomes possible to stabilize the amount of fuel injected, it is possible to improve the air-fuel ratio controllability during the operation of the fuel injection means and suppress the deterioration of exhaust emission.

It is a figure for demonstrating the system configuration | structure of embodiment. It is a figure showing an example of injection end timing control in an embodiment. It is the figure which showed the relationship between differential pressure | voltage (DELTA) P and the injection flow coefficient (phi). 4 is a flowchart showing injection end timing control executed by an ECU 50 in the embodiment. 6 is a flowchart showing a routine for setting a start timing CA _{st (k)} of pre-ignition suppression injection executed by the ECU 50 in the embodiment.

[Description of system configuration]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a diagram for explaining a system configuration according to an embodiment of the present invention. As shown in FIG. 1, the system of this embodiment includes an engine 10 as an internal combustion engine. The engine 10 shown in FIG. 1 is an in-line four-cylinder engine, but the number of cylinders and the cylinder arrangement of the engine applicable to this embodiment are not limited to this.

In the cylinder 12 of the engine 10, an injector 14 that directly injects fuel into the cylinder 12, a spark plug 16 that ignites an air-fuel mixture in the cylinder, and a pressure in the cylinder 12 (hereinafter referred to as “in-cylinder pressure P _cyl ”). An in-cylinder pressure sensor 18 for detecting the above is installed. The injector 14 is connected to a common rail 20 common to them. The common rail 20 is connected to the fuel tank 22 via a fuel pipe 24. A supply pump 26 is connected on the fuel pipe 24, and high-pressure fuel pressurized by the supply pump 26 is stored in the common rail 20. The common rail 20 is provided with a fuel pressure sensor 28 for detecting the pressure of the fuel inside the common rail 20 (hereinafter referred to as “fuel pressure P _f ”).

  As shown in FIG. 1, the system according to the present embodiment includes a turbocharger 30. The turbocharger 30 has an exhaust turbine 30a and an intake compressor 30b driven by the exhaust turbine 30a. The exhaust turbine 30 a is disposed in the middle of the exhaust passage 32. The intake air compressor 30b is disposed in the intake passage 34.

  Further, the system of the present embodiment includes an ECU (Electronic Control Unit) 50 as a control device. An injector 14, a spark plug 16, and the like are connected to the output side of the ECU 50. An in-cylinder pressure sensor 18, a fuel pressure sensor 28, a crank angle sensor 36, and the like are connected to the input side of the ECU 50. The ECU 50 can control various actuators such as the injector 14 and the spark plug 16 based on these sensor signals.

[Features of this embodiment]
By the way, due to the increasing demand for fuel efficiency in recent years, a small supercharged engine has been developed that aims to improve fuel efficiency by reducing the engine displacement while ensuring the same output as a large displacement engine. For the feed engine, an improvement in output in a more severe operating region is required. The engine 10 of the present embodiment is such a small supercharged engine, and in order to improve its output, it is necessary to fill the cylinder 12 with more air-fuel mixture. However, as the amount of the air-fuel mixture in the cylinder 12 increases, the in-cylinder pressure P _cyl in the compression stroke and the air-fuel mixture temperature increase, so that pre-ignition easily occurs. Therefore, sufficient countermeasures are desired for the occurrence of pre-ignition in such a small supercharged engine.

When the occurrence of pre-ignition is detected in advance, it is desirable to perform pre-ignition suppression injection that additionally drives the injector 14 in the compression stroke, because the occurrence of pre-ignition can be effectively avoided. In addition, a target value of the fuel amount to be injected (hereinafter referred to as “target injection amount Q _t ”) is set in the pre-ignition suppression injection, and the additional drive period of the injector 14 is set based on the target injection amount Q _t. It is desirable that fuel is not injected more than necessary.

However, the in-cylinder pressure P _cyl in the compression stroke changes according to the crank angle, and increases in the second half of the compression stroke. Therefore, in the compression stroke, the differential pressure ΔP between the in-cylinder pressure P _cyl and the fuel pressure P _f becomes smaller in the latter half of the compression stroke. Accordingly, while the differential pressure ΔP is large, the fuel is injected vigorously. However, as the differential pressure ΔP decreases, the momentum decreases, and the injection amount decreases. Therefore, there is a possibility that the target injection amount Q _t is not accurately injected within the set additional drive period.

Therefore, in the present embodiment, the amount of fuel actually injected by sequentially calculating the differential pressure ΔP after the start of the pre-ignition suppression injection (hereinafter referred to as “actual injection amount Q _r ”) is not the additional drive period. Thus, the end timing CA _ed is controlled (injection end timing control). FIG. 2 is a diagram showing an example of injection end timing control in the present embodiment. As shown in FIG. 2, the in-cylinder pressure P _cyl gradually increases after the intake stroke, further increases after ignition, reaches a maximum value, and then decreases. On the other hand, the fuel pressure P _f is the intake, compression, expansion, takes a constant value in each exhaust strokes. The actual injection amount Q _r corresponds to the area of the shaded portion in FIG. 2 and is obtained by sequentially calculating the differential pressure ΔP after the start timing CA _st of the pre-ignition suppression injection and using this calculated value.

Calculated value of the differential pressure ΔP is used to calculate a respective injection flow rate Q _f. The injection flow rate Q _f is obtained by multiplying the nozzle opening area S of the injector 14 by the injection flow rate coefficient φ (Q _f = S × φ). Here, the nozzle opening area S is a fixed value determined by the nozzle shape of the injector 14. On the other hand, the injection flow coefficient φ is determined from a so-called throttling formula and a differential pressure ΔP. FIG. 3 is a diagram showing the relationship between the differential pressure ΔP and the injection flow coefficient φ. As shown in FIG. 3, the injection flow coefficient φ is substantially proportional to the differential pressure ΔP in the region where the differential pressure ΔP is large, and goes to zero in the region where the differential pressure ΔP is small while increasing the degree of decrease. . Such a relationship is assumed to be map data and stored in advance in the ECU 50.

Injection completion timing control in this embodiment, thus the injection flow rate Q _f integrating seeking actual injection quantity Q _r thus determined is compared with the actual injection quantity Q _r and the target injection amount Q _t obtained. When the actual injection quantity obtained exceeds the target injection amount Q _t, and ends the pre-ignition suppression injection. Thereby, generation | occurrence | production of a preg can be avoided effectively, using a fuel without waste. In addition, since it is possible to stabilize the injection amount, it is possible to improve the air-fuel ratio controllability at the time of pre-ignition suppression injection and suppress the deterioration of exhaust emission.

[Specific processing in this embodiment]
Next, a specific process for realizing the above-described injection end timing control will be described with reference to FIGS. 4 and 5. FIG. 4 is a flowchart showing the injection end timing control executed by the ECU 50 in the present embodiment. It is assumed that the routine shown in FIG. 4 is executed when the occurrence of prag is predicted by a known routine different from this routine.

In the routine shown in FIG. 4, first, the ECU 50 sets the start timing CA _{st (k)} of the pre-ignition suppression injection (step 100). In this step, the value calculated by the subroutine of FIG. 5 (details will be described later) executed in parallel with this routine is used as the start timing CA _{st (k)} of the pre-ignition suppression injection. It is assumed that 30 ° CA after intake BDC is used as the initial value of start timing CA _{st (k)} , that is, start timing CA _{st (1)} .

Subsequently, the ECU 50 starts the additional drive of the injector 14 and calculates the injection flow rate Q _f from the differential pressure ΔP between the in-cylinder pressure P _cyl and the fuel pressure P _f (step 110). Specifically, the ECU 50 calculates the differential pressure ΔP from the in-cylinder pressure P _cyl and the fuel pressure P _f input to the ECU 50 after the start time CA _{st (k)} , and performs a map search for the injection flow coefficient φ from the differential pressure ΔP. Then, the injection flow rate Q _f is calculated by substituting this injection flow rate coefficient φ into a previously stored calculation formula (Q _f = S × φ). These calculated values are temporarily stored in the ECU 50 at each input timing of the in-cylinder pressure P _cyl and the fuel pressure P _f .

Subsequently, ECU 50 cumulatively adds the calculated value of the injection flow rate _{Q f,} and calculates the actual injection quantity _{Q r} a _(k) (step 120). In this step, the ECU 50 calculates the actual injection amount Q _{r (k)} for each input timing of the in-cylinder pressure P _cyl and the fuel pressure P _f and temporarily stores it in the inside. Subsequently, the ECU 50 determines whether or not the stored actual injection amount _{Qr (k)} is larger than the target injection amount _{Qt (k)} (step 130). In this step, the target injection amount Q _{t (k)} to be compared with the actual injection amount Q _{r (k)} is the target at the time of normal injection injected for the purpose of driving the engine 10 immediately before the pre-ignition suppression injection. A value obtained by multiplying the injection amount by a predetermined coefficient is used. In addition, since the determination method of the target injection quantity at the time of normal injection is well-known, the detailed description is abbreviate | omitted here.

If it is determined in step 130 that the actual injection amount _{Qr (k)} is larger than the target injection amount _{Qt (k)} , it can be determined that the occurrence of pre-ignition has been avoided, so the ECU 50 performs additional driving of the injector 14. To stop the pre-ignition suppression injection (step 140). In the process of this step, the end timing CA _{ed (k)} of the pre-ignition suppression injection is stored in the ECU 50. On the other hand, when it is determined in step 130 that the actual injection amount _{Qr (k)} is equal to or less than the target injection amount _{Qt (k)} , the ECU 50 returns to step 110 without stopping the additional drive of the injector 14. Then, the injection flow rate _Qf is calculated again.

Next, a method for setting the start timing CA _{st (k)} of the pre-ignition suppression injection will be described with reference to FIG. FIG. 5 is a flowchart illustrating a routine for calculating the start timing CA _{st (k)} of the pre-ignition suppression injection executed by the ECU 50 in the present embodiment. In the routine shown in FIG. 5, first, the ECU 50 _obtains the previous _pre-ignition suppression injection end timing CA _{ed (k−1)} and the previous _{pre-premature} suppression injection end limit timing CA _{lmt (k−1)} ( Step 200). In this step, the ECU 50 acquires the end time CA _{ed (k−1)} stored in the ECU 50 in step 140 of FIG. Further, the ECU 50 is set by a process different from this routine, and _acquires the end limit time CA _{lmt (k−1)} stored in the ECU 50.

Here, the end limit time CA _{lmt (k−1)} is a time at which the _pre-ignition suppression injection is forcibly ended, and in this embodiment, the contact time CA _{pt at which the} injected fuel contacts the rising piston top surface. _{Of (k-1)} and the ignition timing _{CAigt (k-1)} of the spark plug 16, it is set to the one that arrives earlier. Such end limit timing CA _{lmt (k-1)} is set because of the contact timing CA _{pt (k-1)} at which the sprayed fuel is insufficiently vaporized and the cooling performance is deteriorated, or the ignition at which no plague can occur. This is to exclude the later. As the contact timing CA _{pt (k−1)} , a value that is set by experiment or the like and stored in the ECU 50 is used. The ignition timing CA _{exit (k−1)} is a value calculated by correcting the basic ignition timing determined based on the operating state of the engine 10 with various known parameters. In addition, since the calculation method of ignition timing _{CAigt (k-1)} is well-known, the detailed description is abbreviate | omitted here.

Subsequently, the ECU 50 calculates a difference ΔCA between the end time CA _{ed (k−1)} acquired in step 200 and the end limit time CA _{lmt (k−1)} (step 210). Subsequently, ECU 50 is a ΔCA calculated in step 210, it calculates a present start timing _{CA st (k)} by subtracting from the start timing of the previous Plague suppressing injection _{CA st (k-1) (step} 220) . Thereby, the start timing CA _{st (k)} of the present pre-ignition suppression injection is set.

As described above, according to the routines shown in FIGS. 4 and 5, the actual injection amount obtained by calculating the injection flow rate Q _f from the differential pressure ΔP between the in-cylinder pressure P _cyl and the fuel pressure P _f and integrating the injection flow rate Q _f. When Q _{r (k)} exceeds the target injection amount Q _{t (k)} , the pre-ignition suppression injection can be ended. Therefore, it is possible to effectively avoid the occurrence of pre-ignition while using the fuel without waste. In addition, since it is possible to stabilize the injection amount, it is possible to improve the air-fuel ratio controllability at the time of pre-ignition suppression injection and suppress the deterioration of exhaust emission.

  By the way, in this embodiment, the pre-ignition suppression injection which additionally drives the injector 14 was implemented, but this pre-ignition suppression injection can be implemented even if it is not the additional drive of the injector 14. For example, in a so-called dual injector type engine 10 provided with a port injector for injecting fuel into the intake port in addition to the injector 14, the port injector may be used during normal operation, and the injector 14 may be used during pre-ignition suppression injection. . That is, any system that can additionally inject fuel into the cylinder 12 when the occurrence of pre-ignition is detected in advance can be applied as a modification of the present embodiment.

  Moreover, although this embodiment presupposed the system provided with the turbocharger 30, the turbocharger 30 is not necessarily required and can be applied to a system that does not include the turbocharger 30.

  In the above-described embodiment, the injector 14 is the “fuel injection means” in the first invention, the in-cylinder pressure sensor 18 is the “in-cylinder pressure acquisition means” in the first invention, and the fuel pressure sensor 28 is the above-described fuel pressure sensor 28. The ECU 50 corresponds to the “fuel pressure acquisition means” in the first invention, and the “operation control means” in the first invention. In the above-described embodiment, the “operation end timing control means” in the first aspect of the present invention is realized by the ECU 50 executing the series of routines of FIG.

  In the embodiment described above, the ECU 50 executes the processing of steps 110 and 120 in FIG. 4 so that the “actual injection amount calculating means” in the second invention executes the processing of step 130 in FIG. Thus, the “injection amount comparing means” in the second invention realizes the “operation stop means” in the second invention by executing the processing of step 140 of FIG.

DESCRIPTION OF SYMBOLS 10 Engine 12 Cylinder 14 Injector 16 Spark plug 18 In-cylinder pressure sensor 20 Common rail 22 Fuel tank 24 Fuel pipe 26 Supply pump 28 Fuel pressure sensor 30 Turbocharger 30a Exhaust turbine 30b Intake compressor 32 Exhaust passage 34 Intake passage 36 Crank angle sensor 50 ECU

Claims (2)

Fuel injection means for injecting fuel into a cylinder of the internal combustion engine;
Fuel pressure acquisition means for acquiring the pressure of the fuel supplied to the fuel injection means;
In-cylinder pressure acquisition means for acquiring the in-cylinder pressure of the internal combustion engine;
An operation control means for temporarily operating the fuel injection means when occurrence of pre-ignition is predicted;
When the fuel injection means is operated by the operation control means, the difference between the fuel pressure acquired by the fuel pressure acquisition means and the in-cylinder pressure acquired by the in-cylinder pressure acquisition means is used. An operation end timing control means for controlling the operation end timing;
A control device for an internal combustion engine, comprising: The operation end timing control means includes
An actual injection amount calculating means for calculating an actual injection amount during operation of the fuel injection means, using the differential pressure;
An injection amount comparison means for comparing the actual injection amount calculated by the actual injection amount calculation means with a target injection amount as a target value of fuel to be injected during operation of the fuel injection means;
An operation stopping means for stopping the operation of the fuel injection means when the actual injection amount calculated by the actual injection amount calculation means exceeds the target fuel amount;
The control apparatus for an internal combustion engine according to claim 1, comprising:

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