JP2010285904A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine, which suppresses the torque fluctuation and emission deterioration in an internal combustion engine directly injecting fuel into a cylinder. <P>SOLUTION: In a control device of an internal combustion engine which is equipped with a fuel injection valve for directly injecting fuel into a cylinder of the internal combustion engine and which injects fuel through the fuel injection valve dividedly in several times during an intake stroke of the internal combustion engine, the second injection is executed during a period where lift speed in a period from IVO to the maximum lift is fast (a high lift speed period). It is preferable that the second injection is executed during a period near the timing where the lift speed becomes maximum. Further preferably, fuel pressure in the second fuel injection is set lower than that in the first fuel injection. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that directly injects fuel into a cylinder of the internal combustion engine.

  Conventionally, for example, as disclosed in Japanese Patent Application Laid-Open No. 2007-291887, a device for suppressing fuel adhesion to an intake valve in a direct injection gasoline engine has been disclosed. More specifically, in this device, in order to avoid interference between the fuel spray injected from the injector into the cylinder and the intake valve opened to a predetermined lift amount, the fuel is avoided while the intake valve is at a high lift. The spraying time for spraying is set. Thereby, since fuel does not adhere to the intake valve, it is possible to suppress the decrease in engine output and the occurrence of smoke.

JP 2007-291887 A Japanese Patent Laid-Open No. 9-242577 JP-A-11-101147 JP 2003-193894 A JP 2008-31932 A

  However, in the above-described conventional apparatus, the fuel injection period may be set in the latter half of the lift of the intake valve for the purpose of avoiding a high lift of the intake valve. If fuel injection is performed in the latter half of the lift of the intake valve, that is, in the period near the time when the intake valve is closed, it may be difficult to secure sufficient time for homogenizing the air-fuel mixture. Further, near the time when the intake valve is closed, since the intake valve is cooled by intake air (fresh air), fuel atomization may be deteriorated. Further, in the vicinity of the time when the intake valve is closed, the position of the piston is lowered, so there is a possibility that fuel adhesion to the liner may increase. As described above, in the conventional apparatus described above, there is a possibility that torque fluctuation and emission deterioration may be caused by retarding the fuel injection timing.

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine control device capable of suppressing torque fluctuations and emission deterioration in an internal combustion engine that directly injects fuel into a cylinder. The purpose is to provide.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A fuel injection device that directly injects fuel into a cylinder of an internal combustion engine;
Fuel injection means for injecting fuel from the fuel injection device in a plurality of times during the intake stroke of the internal combustion engine,
The fuel injection means performs the second and subsequent injections in a predetermined period within a period from the start of lift of the intake valve to the maximum lift.

According to a second invention, in the first invention,
The fuel injection means performs the second injection in a period in the vicinity of the time when the lift speed of the intake valve becomes maximum.

According to a third invention, in the first or second invention,
Fuel pressure setting means for variably setting the fuel pressure of the fuel injected from the fuel injection device is further provided, and the fuel pressure at the time of the second injection by the fuel injection means is set lower than at the time of the first injection. And

According to a fourth invention, in the third invention,
The fuel injection means performs the second injection in a period from the start of lift of the intake valve to the maximum lift.

According to a fifth invention, in any one of the first to fourth inventions,
The fuel injection means performs the first injection in a predetermined period within a period from intake TDC to the start of lift of the valve.

  According to the first invention, fuel injection into the cylinder is performed a plurality of times during the intake stroke of the internal combustion engine. At this time, the second and subsequent fuel injections are performed in a predetermined period within the period from the start of lift of the intake valve to the maximum lift. For this reason, according to the present invention, since fuel injection is not performed during the period from the maximum lift of the intake valve to the end of lift, it is possible to effectively suppress torque fluctuations and deterioration of emissions.

  According to the second invention, the second fuel injection is performed in a period in the vicinity of the time when the lift speed of the intake valve becomes maximum. For this reason, according to the present invention, it is possible to reduce the amount of fuel that collides per unit time of the intake valve, so that it is possible to effectively suppress fuel adhesion to the intake valve and suppress deterioration of emissions. Can do.

  According to the third invention, the fuel pressure of the second fuel injection is set lower than that of the first fuel injection. Therefore, according to the present invention, since the amount of fuel that collides with the intake valve per unit time is reduced, it is possible to effectively suppress the fuel adhesion to the intake valve and suppress the deterioration of the emission. .

  According to the fourth aspect, the period of the second fuel injection is set to the period from the start of lift of the intake valve to the maximum lift. Therefore, according to the present invention, it is possible to effectively ensure the fuel injection amount necessary for the second fuel injection.

  According to the fifth aspect of the invention, the first fuel injection is performed in a predetermined period within the period from the intake TDC to the start of lift of the intake valve. For this reason, according to this invention, since the homogeneity of a fuel can be improved, the deterioration of an emission can be suppressed.

It is a schematic block diagram for demonstrating the system configuration | structure as embodiment of this invention. It is a figure which shows the change of the torque fluctuation with respect to an engine load. It is a figure which shows the change of the various performance with respect to fuel injection time. It is a figure for demonstrating the relationship between the lift timing of the intake valve 22, and a fuel-injection period. It is a flowchart which shows the routine performed in Embodiment 1 of this invention. It is a figure for demonstrating the relationship between the lift timing of the intake valve 22, a fuel injection period, and a fuel pressure. It is a flowchart which shows the routine performed in Embodiment 2 of this invention.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a schematic configuration diagram for explaining a system configuration as a first embodiment of the present invention. As shown in FIG. 1, the system according to the present embodiment includes an internal combustion engine 10. The internal combustion engine 10 is configured as a spark ignition engine having a plurality of cylinders. In FIG. 1, a cross section of one cylinder of the internal combustion engine 10 is schematically shown. A piston 12 that reciprocates inside the cylinder of the internal combustion engine 10 is provided. Further, the internal combustion engine 10 includes a cylinder head 14. A combustion chamber 16 is formed between the piston 12 and the cylinder head 14. One end of an intake passage 18 and an exhaust passage 20 communicates with the combustion chamber 16. An intake valve 22 and an exhaust valve 24 are disposed at a communication portion between the intake passage 18 and the exhaust passage 20 and the combustion chamber 16, respectively.

  An air cleaner 26 is attached to the inlet of the intake passage 18. A throttle valve 28 is disposed downstream of the air cleaner 26. The throttle valve 28 is an electronically controlled valve that is driven by a throttle motor based on the accelerator opening.

  A spark plug 32 is attached to the cylinder head 14 so as to protrude from the top of the combustion chamber 16 into the combustion chamber 16. The cylinder head 14 is provided with a fuel injection valve 34 so as to protrude from the vicinity of the intake valve 22 into the combustion chamber 16. The fuel injection valve 34 is a slit nozzle type fuel injection valve that injects a fan-shaped fuel spray having a divergent shape and a relatively thin thickness into the cylinder, and the fuel injection direction is the central direction of the combustion chamber 16. Are arranged as follows.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 30 as shown in FIG. In addition to the crank angle sensor 36 for detecting the rotational position of the crankshaft, various sensors for detecting information on the internal combustion engine 10 are connected to the input portion of the ECU 30. Further, various actuators such as the throttle valve 28, the spark plug 32, and the fuel injection valve 34 described above are connected to the output portion of the ECU 30. The ECU 30 controls the operating state of the internal combustion engine 10 based on various types of input information.

[Operation of Embodiment 1]
Next, the operation of the present embodiment will be described with reference to FIGS. As described above, the internal combustion engine 10 of the present embodiment is a so-called direct injection internal combustion engine that directly injects fuel into a cylinder. In a direct-injection internal combustion engine, torque fluctuations during high rotation and high load operation become a problem. Therefore, in the system of the present embodiment, as a countermeasure, fuel injection is performed twice during the intake stroke in a predetermined high load region. FIG. 2 is a diagram illustrating a change in torque fluctuation with respect to the engine load. As shown in this figure, it is understood that if fuel injection is performed twice in the intake stroke, torque fluctuation is suppressed in the high load region of the engine as compared with the case of one fuel injection. This is because homogenization of the air-fuel mixture in the combustion chamber 16 can be promoted by performing fuel injection twice.

  However, in the internal combustion engine 10 according to the present embodiment, the second spray fuel injected from the fuel injection valve 34 may interfere with the intake valve 22 depending on the timing of fuel injection. FIG. 3 is a diagram showing changes in various performances with respect to the fuel injection timing. As shown in this figure, the fuel spray and the intake valve 22 interfere with each other during a predetermined period before and after the maximum lift timing of the intake valve 22. When the fuel spray and the intake valve 22 interfere with each other, the spray that has bounced off the intake valve 22 is concentrated in a specific region in the combustion chamber 16. For this reason, as shown in this figure, when fuel injection is performed in the interference region, the amount of PM generated increases.

  Further, if fuel is injected after the maximum lift of the intake valve 22, the homogeneity of the air-fuel mixture is deteriorated and the liner wetness is increased. For this reason, as shown in this figure, as the fuel injection is performed on the retard side with respect to the maximum lift, an increase in the amount of HC generated and an increase in torque fluctuation become more significant.

  Therefore, in this embodiment, the fuel injection timing is set in a region where the second fuel spray and the intake valve 22 do not interfere as much as possible. FIG. 4 is a diagram for explaining the relationship between the lift timing of the intake valve 22 and the fuel injection period. As shown in this figure, the second fuel injection timing is set to a predetermined period in the region from the opening timing of the intake valve 22 (hereinafter referred to as “IVO”) to the maximum lift time. The predetermined period is preferably a period during which the lift speed of the intake valve 22 is high (hereinafter referred to as “a large lift speed period”). Therefore, in the present embodiment, a period in the vicinity of the timing when the lift speed of the intake valve 22 is maximum is set as the lift speed large period, and this period is set as the second fuel injection period. The high lift speed period may be a period in which the integral value of the lift speed is maximum, for example, as long as the lift speed of the intake valve 22 is high, or a period in which the lift speed is a reference value or more. Good.

  In this way, by setting the second fuel injection at a time when the lift speed of the intake valve 22 is fast, the amount of fuel spray that interferes per unit time of the intake valve 22 can be reduced. Thereby, the position of the fuel spray that rebounds by interfering with the intake valve 22 can be effectively dispersed, so that spray concentration can be avoided and deterioration of emission can be suppressed.

  Further, in the present embodiment, since the second fuel injection timing is set in a region retarded from the maximum lift, the deterioration of the homogeneity of the air-fuel mixture and the increase in liner wetness are suppressed, and the amount of HC generated Increase and torque fluctuation can be suppressed.

  As shown in FIG. 4, the first fuel injection timing is set to a predetermined period in the region from intake TDC to IVO. As a result, a predetermined required interval can be provided between the first fuel injection and the second fuel injection, so that the homogeneity of the air-fuel mixture in the combustion chamber 16 can be improved.

[Specific Processing in First Embodiment]
Next, specific processing of the first embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing a routine in which the ECU 30 sets the fuel injection timing.

  In the routine shown in FIG. 5, first, the engine speed and load factor of the internal combustion engine 10 are detected based on detection signals from various sensors such as the crank angle sensor 36 (step 100). Next, torque fluctuation is estimated (step 102). Specifically, the torque fluctuation is estimated based on the engine speed, the load factor, etc. detected in step 100 above.

  Next, it is determined whether or not two combustion injections are executed in the intake stroke (step 104). Specifically, it is determined whether the torque fluctuation amount estimated in step 102 is greater than a predetermined determination value. As a result, when the torque fluctuation amount is equal to or less than the predetermined determination value, it is determined that there is no problem even with one fuel injection, and this routine is immediately terminated.

  On the other hand, if the torque fluctuation amount is larger than the predetermined determination value in the above step 104, it is determined that two fuel injections are necessary, the process proceeds to the next step, and the crank angle signal of the crank angle sensor 36 is obtained. Based on this, IVO and IVC (the closing timing of intake valve 22) are detected (step 106).

  In the routine shown in FIG. 5, next, a predetermined period (a large lift speed period) A1 in which the lift speed of the intake valve 22 is high is calculated (step 108). Here, specifically, a predetermined period before and after the time when the lift speed is maximum is specified as the large lift speed period A1.

  Next, the required fuel injection amount X is calculated based on the operating condition and operating state of the internal combustion engine 10 (step 110). The required fuel injection amount X represents the sum of the first fuel injection amount x1 and the second fuel injection amount x2. Next, the second fuel injection time B2 and the fuel injection timing are specified (step 112). Specifically, the large lift speed period A1 calculated in step 102 is specified as the second fuel injection time B2 and the fuel injection timing.

  Next, the required injection interval is calculated and the intake TDC is detected (step 114). The required injection interval is the minimum interval that can maintain the homogeneity of the air-fuel mixture in the combustion chamber 16, and can be calculated using a map with the fuel injection amount and the like as parameters.

  Next, the first fuel injection time B1 and the fuel injection timing are specified (step 116). Specifically, first, the second fuel injection amount x2 is calculated based on the fuel injection time B2 specified in step 112 above. Then, the first fuel injection amount x1 is calculated by subtracting the second fuel injection amount x2 from the fuel injection amount X specified in step 110 above. Next, the first fuel injection time B1 is calculated based on the first fuel injection amount x1. Then, the injection timing of the first fuel injection time B1 is specified within a period that is behind the intake TDC and within which a necessary injection interval can be secured.

  As described above, according to the system of the first embodiment, when fuel injection is performed twice, the time when the second fuel spray does not interfere with the intake valve 22 as much as possible can be set. Thereby, spray concentration can be avoided and emission deterioration can be suppressed.

  By the way, in the above-described embodiment, in the internal combustion engine 10 capable of two fuel injections, the second fuel injection timing is set to the high lift speed period, but the fuel injection set to such a period is set. Is not limited to the second time. That is, there is no particular limitation on the number of injections as long as any one of the injection timings when performing fuel injection multiple times is set to the lift speed large period.

  In the above-described embodiment, the predetermined period before and after the period when the lift speed is maximum is specified as the large lift speed period A1, but the method for specifying the high lift speed period is limited to this. Absent. That is, for example, a period in which the lift speed is equal to or higher than a reference value may be specified as the large lift speed period, or a period in which the lift speed of the intake valve 22 is high may be specified by another method. .

  In the first embodiment described above, the fuel injection valve 34 corresponds to the “fuel injection device” according to the first aspect of the present invention.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. 6 and FIG. The system of the present embodiment can be realized by causing the ECU 30 to execute a routine shown in FIG. 7 to be described later using the hardware configuration shown in FIG.

  In the first embodiment described above, no particular reference is made to control of the fuel pressure when fuel injection is performed. On the other hand, the second embodiment is characterized by further controlling the fuel pressure in addition to the control of the first embodiment. FIG. 6 is a diagram for explaining the relationship among the lift timing of the intake valve 22, the fuel injection period, and the fuel pressure. FIG. 6A shows the lift timing of the intake valve 22 in the intake stroke. Further, (B) in FIG. 6 shows a case where the fuel pressure is controlled to be constant during the fuel injection period in the first embodiment described above. Further, (C) in FIG. 6 shows a case where the fuel pressure is variably controlled in the fuel injection period in the second embodiment to be described later.

  The fuel injection amount per hour increases as the fuel pressure increases. For this reason, if the fuel pressure is high in the second fuel injection, the amount of fuel spray per unit time that interferes with the intake valve 22 increases. Therefore, in the system according to the present embodiment, the fuel pressure during the second fuel injection is set low. More specifically, as shown in FIG. 6C, the fuel pressure at the second fuel injection is set lower than that at the first fuel injection. At this time, since the fuel injection amount decreases if the fuel pressure is lowered, the desired fuel injection amount is secured by extending the fuel injection time within the period from the IVO to the maximum lift. As a result, the amount of fuel spray that interferes with the intake valve 22 per unit time can be reduced while maintaining the amount of fuel necessary for the second injection, so that deterioration of emissions can be effectively suppressed. .

[Specific Processing of Embodiment 2]
Next, specific processing of the second embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing a routine in which the ECU 30 sets the fuel injection timing.

  In the routine shown in FIG. 7, first, the engine speed and load factor of the internal combustion engine 10 are detected based on detection signals of various sensors such as the crank angle sensor 36 (step 200). Next, torque fluctuation is estimated (step 202). Next, it is determined whether or not two combustion injections are executed in the intake stroke (step 204). Here, specifically, the same processing as in steps 100 to 104 is executed. As a result, when the torque fluctuation amount is equal to or less than the predetermined determination value, it is determined that there is no problem even with one fuel injection, and this routine is immediately terminated.

  On the other hand, if the amount of torque fluctuation is larger than the predetermined determination value in step 204, it is determined that two fuel injections are necessary, and the process proceeds to the next step, where the crank angle signal of the crank angle sensor 36 is output. Based on this, the IVO and maximum lift timing are detected (step 206).

  In the routine shown in FIG. 7, next, a period A2 from IVO to the maximum lift is calculated (step 208). Here, specifically, the IVO detected in step 206 and the maximum lift timing are used. Next, the required fuel injection amount X is calculated based on the operating condition and operating state of the internal combustion engine 10 (step 210). Here, specifically, the same processing as in step 110 is executed.

  Next, the second fuel injection time C2, the fuel injection timing, and the fuel pressure are specified (step 212). Specifically, the period A2 from IVO to the maximum lift calculated in step 208 is specified as the second fuel injection time C2 and the fuel injection timing. Further, the fuel pressure d2 in the second fuel injection is set to a value smaller than the fuel pressure d1 in the first fuel injection. Next, calculation of the required injection interval and detection of intake TDC are performed (step 214). Here, specifically, the same processing as in step 114 is executed. Next, the first fuel injection time C1 and the fuel injection timing are specified (step 216). Here, specifically, the same processing as in step 116 is executed.

  As described above, according to the system of the second embodiment, when two fuel injections are performed, the fuel pressure in the second fuel injection is set lower than that in the first fuel injection. Thereby, spray concentration can be avoided effectively and the deterioration of emission can be suppressed.

  By the way, in the above-described embodiment, in the internal combustion engine 10 capable of two fuel injections in the intake stroke, the second fuel injection timing is set to the period from IVO to the maximum lift. The set fuel injection is not limited to the second time. That is, there is no particular limitation on the number of injections as long as any injection timing in the case of performing multiple fuel injections is set in the period.

  In the above-described embodiment, the two fuel injection periods are set to the period from IVO to the maximum lift, but the fuel injection period is not limited to this. In other words, as long as the fuel injection amount for the second time can be ensured, it may be set to another period within the period from IVO to the maximum lift. For example, the lift speed in the first embodiment described above is high. It is good also as setting to a period.

  In the second embodiment described above, the “fuel pressure setting means” according to the first aspect of the present invention is realized by the ECU 30 executing the process of step 212 described above.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Cylinder head 16 Combustion chamber 18 Intake passage 20 Exhaust passage 22 Intake valve 24 Exhaust valve 26 Air cleaner 28 Throttle valve 30 ECU (Electronic Control Unit)
32 Spark plug 34 Fuel injection valve 36 Crank angle sensor

Claims (5)

A fuel injection device that directly injects fuel into a cylinder of an internal combustion engine;
Fuel injection means for injecting fuel from the fuel injection device in a plurality of times during the intake stroke of the internal combustion engine,
The control device for an internal combustion engine, wherein the fuel injection means performs the second and subsequent injections in a predetermined period within a period from the start of lift of the intake valve to the maximum lift.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the fuel injection means performs the second injection in a period in the vicinity of a time when the lift speed of the intake valve becomes maximum.   Fuel pressure setting means for variably setting the fuel pressure of the fuel injected from the fuel injection device is further provided, and the fuel pressure at the time of the second injection by the fuel injection means is set lower than at the time of the first injection. The control apparatus for an internal combustion engine according to claim 1 or 2.   4. The control apparatus for an internal combustion engine according to claim 3, wherein the fuel injection means performs the second injection in a period from a start of lift of the intake valve to a maximum lift.   5. The control device for an internal combustion engine according to claim 1, wherein the fuel injection unit performs the first injection in a predetermined period within a period from intake TDC to the start of lift of the valve. .

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