JP2012112314A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device capable of ensuring a high startability.SOLUTION: The control device includes a direct injection injector, a cylinder pressure sensor, and a crank angle sensor. The combustion pressure in a crank angle in a post-ignition flame propagation detected by the cylinder pressure sensor (hereafter, referred to as a post-ignition crank angle) is divided by a unit crank angle, and a combustion speed is calculated. The control device determines whether the combustion speed is lower than the reference combustion speed during normal combustion in the post-ignition crank angle. When the combustion speed is lower than the reference combustion speed, the amount of an additional fuel is injected to a present combustion cylinder in the same cycle as a cycle from which the combustion speed is calculated.

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable for executing control of an internal combustion engine mounted on a vehicle.

  Conventionally, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 10-299563), a direct injection injector that directly injects fuel into a cylinder and an in-cylinder pressure sensor that detects combustion pressure in the cylinder are provided. Internal combustion engines are known. Patent Document 1 discloses a control device that determines misfire based on a combustion pressure waveform detected by an in-cylinder pressure sensor and corrects the fuel injection amount in the next cycle.

Japanese Patent Laid-Open No. 10-299563 JP-A-4-301158

  By the way, a vehicle having an idling stop function for automatically starting or stopping an internal combustion engine when a predetermined condition is satisfied is known. In such a vehicle, at the time of restart from the idling stop, an appropriate fuel injection amount may not be injected at the time of the first injection. Possible reasons include clogging of the injection hole of the direct injection due to deposit accumulation and fuel spray deterioration when heavy fuel is used. In such a case, there is a problem that the startability of the internal combustion engine is deteriorated.

  With respect to this problem, even if the control device of Patent Document 1 is applied, it is not possible to correct the starting amount of the internal combustion engine because the fuel injection amount can be corrected in the next cycle.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a control device for an internal combustion engine that can ensure high startability.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A direct injection injector that directly injects fuel into a cylinder of an internal combustion engine;
In-cylinder pressure acquisition means for acquiring the combustion pressure in the cylinder;
Crank angle acquisition means for acquiring a crank angle of the internal combustion engine;
A combustion speed calculating means for calculating a combustion speed by dividing a combustion pressure at a crank angle during propagation of a flame after ignition acquired by the in-cylinder pressure acquiring means (hereinafter referred to as a crank angle after ignition) by a unit crank angle;
Combustion speed determination means for determining whether or not the combustion speed is lower than a reference combustion speed during normal combustion at the crank angle after ignition;
Current combustion cylinder correction means for injecting an additional amount of fuel into the current combustion cylinder in the same cycle as the cycle in which the combustion speed is calculated when the combustion speed is lower than the reference combustion speed, To do.

The second invention is the first invention, wherein
The apparatus further comprises an additional fuel amount calculating means for calculating the additional fuel amount as the deviation between the reference combustion rate and the combustion rate increases.

The third invention is the first or second invention, wherein
A post-ignition crank angle determining means for determining whether a condition that the post-ignition crank angle is before bottom dead center and before exhaust valve opening in the expansion stroke is satisfied;
And further comprising a next combustion cylinder correcting means for correcting a predetermined amount of fuel to be increased to a basic injection amount in the next combustion cylinder when the combustion speed is lower than the reference combustion speed and the condition is not satisfied,
The current combustion cylinder correction means adds the current combustion cylinder to the current combustion cylinder in the same cycle as the cycle in which the combustion speed is calculated when the combustion speed is lower than the reference combustion speed and the condition is satisfied. Injecting the amount of fuel.

According to a fourth invention, in any one of the first to third inventions,
The predetermined fuel amount that is corrected to be increased by the next combustion cylinder correcting means is the same as the additional fuel amount.

The fifth invention is the first invention, wherein
Storage means for storing in advance an integrated value of the combustion pressure from the crank angle at the time of ignition during normal combustion to the crank angle after ignition;
Calculating means for calculating an integrated value of the combustion pressure from the crank angle at the time of ignition acquired by the in-cylinder pressure acquiring means to the crank angle after ignition;
And a means for calculating the additional fuel amount to be larger as the deviation between the integrated value stored in the storage means and the integrated value calculated by the calculating means is larger.

According to a sixth invention, in any one of the first to fifth inventions,
The in-cylinder pressure acquisition means is an in-cylinder pressure sensor.

  According to the first invention, the combustion pressure at the crank angle during flame propagation after ignition is divided by the unit crank angle to calculate the combustion speed, and when this combustion speed is lower than the reference combustion speed during normal combustion, An additional amount of fuel is injected into the current combustion cylinder during the same cycle. By performing the second fuel injection during the same cycle, it is possible to secure the torque necessary for the same cycle. For this reason, according to the present invention, high startability can be ensured. Further, by injecting the additional fuel amount, misfire can be avoided and emission can be improved.

  According to the second aspect of the invention, the larger the deviation between the reference combustion speed and the combustion speed, the larger the additional fuel amount is calculated. Therefore, the second fuel injection amount can be increased as the combustion speed is insufficient.

According to the third invention, when the combustion speed is lower than the reference combustion speed, and when the crank angle after ignition is before the bottom dead center in the expansion stroke and before the exhaust valve is opened, the current combustion is performed in the same cycle. An additional amount of fuel can be injected into the cylinder. Therefore, the additional fuel amount can be injected during the crank angle period in which torque is obtained.
On the other hand, according to the third invention, when the crank angle after ignition is not before the bottom dead center in the expansion stroke or before the exhaust valve is opened, the injection of the additional fuel amount in the current combustion cylinder is not performed. In addition, the predetermined fuel amount can be corrected to be increased to the basic injection amount in the next combustion cylinder. As a result, the deterioration of startability can be minimized.

  According to the fourth aspect of the present invention, the additional fuel amount in the current combustion cylinder correction unit can be set to a predetermined fuel amount that is increased and corrected by the next combustion cylinder correction unit. Therefore, an increase in calculation amount can be suppressed.

  According to the fifth aspect of the present invention, the post-ignition crank is calculated from the integrated value of the combustion pressure from the crank angle at the time of ignition during normal combustion to the crank angle after ignition and the crank angle at the time of ignition acquired by the in-cylinder pressure acquisition means. The additional fuel amount is calculated to be larger as the deviation from the integrated value of the combustion pressure up to the corner increases. Therefore, the second fuel injection amount can be increased as the torque becomes insufficient.

  According to the sixth aspect, by providing the in-cylinder pressure sensor, the combustion pressure can be detected in real time.

It is a schematic block diagram for demonstrating the system configuration | structure of embodiment of this invention. It is a PV diagram in a predetermined operation state. It is the enlarged view to which the area | region a of FIG. 2 was expanded. FIG. 4 is a diagram showing a combustion speed in a region b (crank angle θ1) in FIG. 3. It is a figure for demonstrating the torque in the case of performing fuel injection of the 2nd time in the cycle. It is a figure which shows the change of the cylinder pressure at the time of implementing fuel injection of the 2nd time, and the relationship between a combustion speed and a torque. It is a flowchart of the control routine which ECU50 performs in embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail 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.

Embodiment.
[System configuration]
FIG. 1 is a schematic configuration diagram for explaining a system configuration according to an embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine (hereinafter simply referred to as an engine) 10. An engine 10 shown in FIG. 1 is a spark ignition type four-stroke engine provided with a spark plug 12. The engine 10 is also an in-cylinder direct injection engine including a direct injection injector 14 that directly injects fuel into a cylinder.

  Although only one cylinder is depicted in FIG. 1, the vehicle engine 10 is generally composed of a plurality of cylinders. A common delivery pipe (not shown) is connected to the direct injection injector 14 of each cylinder. A fuel tank (not shown) is connected to the delivery pipe. The delivery pipe is provided with a fuel pressure sensor 15 for detecting the fuel pressure supplied from the fuel tank.

  Each cylinder is provided with a cylinder pressure sensor (CPS: Combustion Pressure Sensor) 16 for detecting the cylinder pressure (combustion pressure). Further, the engine 10 is provided with a crank angle sensor 18 that outputs a signal CA according to the crank angle θ.

  An intake passage 20 connected to each cylinder is provided in the intake system of the engine 10. An air cleaner 22 is provided at the inlet of the intake passage 20. An air flow meter 24 that outputs a signal GA corresponding to the flow rate of air sucked into the intake passage 20 is attached downstream of the air cleaner 22. An electronically controlled throttle valve 26 is provided downstream of the air flow meter 24. In the vicinity of the throttle valve 26, a throttle opening sensor 27 for outputting a signal TA corresponding to the opening of the throttle valve 26 is attached. A surge tank 28 is provided downstream of the throttle valve 26. An intake pressure sensor 30 for measuring intake pressure is attached in the vicinity of the surge tank 28.

  An exhaust passage 32 connected to each cylinder is provided in the exhaust system of the engine 10. A catalyst 34 is provided in the exhaust passage 32. As the catalyst, for example, a three-way catalyst, a NOx catalyst, or the like is used.

  An ECU (Electronic Control Unit) 50 is provided in the control system of the engine 10. Various sensors such as the in-cylinder pressure sensor 16, the crank angle sensor 18, the air flow meter 24, the throttle opening sensor 27, and the intake pressure sensor 30 are connected to the input unit of the ECU 50. In addition, various actuators such as the ignition plug 12, the direct injection injector 14, and the throttle valve 26 described above are connected to the output portion of the ECU 50. The ECU 50 controls the operating state of the engine 10 based on various input information. Further, the ECU 50 can calculate the in-cylinder volume V determined by the engine rotational speed (the rotational speed per unit time) and the piston position from the signal CA of the crank angle sensor 18.

  The ECU 50 includes an idling stop control device that automatically stops the engine 10 when a predetermined engine stop condition is satisfied, and automatically starts the engine 10 when a predetermined engine start condition is satisfied while the engine 10 is stopped. ing.

  The ECU 50 calculates an appropriate fuel injection amount that satisfies the target air-fuel ratio according to the operating state based on the engine speed, the load, the intake air amount, and the like, and causes the direct injection injector 14 to inject it. Even at the time of restart from the idling stop, the ECU 50 calculates an appropriate fuel injection amount. However, an appropriate fuel injection amount may not be injected at the time of the first injection at the time of restart. Possible reasons include clogging of the injection hole of the direct injection due to deposit accumulation, fuel spray deterioration when heavy fuel is used, and the like. In such a case, there is a concern about deterioration of startability and emission due to misfire.

  FIG. 2 is a PV diagram in a predetermined operation state. A line 60 in FIG. 2 represents a PV diagram in the case of normal combustion in normal operation. A line 62 represents a PV diagram in the case of normal combustion at the time of restart from the idling stop. When an appropriate fuel injection amount is injected at the time of restart from the idling stop and normal combustion is performed, the in-cylinder pressure rises as shown by the line 62.

  Next, with reference to FIG. 3 and FIG. 4, a difference in combustion speed between normal combustion and non-normal combustion at the time of restart from idling stop will be described. FIG. 3 is an enlarged view of a region a in FIG. FIG. 4 is a diagram showing the combustion speed in the region b (crank angle θ1) of FIG. The combustion speed is represented by a pressure change rate dP / dθ of the in-cylinder pressure per unit crank angle, where P is the in-cylinder pressure and θ is the crank angle.

  The combustion speed α shown in FIGS. 3 and 4 represents the combustion speed at the crank angle θ1 when a proper fuel injection amount corresponding to the target air-fuel ratio is injected and normal combustion is performed at the time of restart from idling stop. On the other hand, when the combustion speed β is restarted from the idling stop, an appropriate fuel injection amount corresponding to the target air-fuel ratio is not injected, and there is a possibility of misfire or a crank angle θ1 when the combustion speed is insufficient. Represents the burning rate.

  As shown in FIG. 3, at the combustion speed α, the in-cylinder pressure changes as indicated by the line 62. On the other hand, as shown by the line 64, the in-cylinder pressure changes at a combustion speed β smaller than the combustion speed α. For this reason, in the case of the combustion speed β, the torque (work amount) represented by the area of the PV diagram cannot be obtained sufficiently. In this case, a sufficient torque cannot be obtained in the current cycle, so that the startability is deteriorated.

  Therefore, in the system of the present embodiment, the in-cylinder pressure sensor 16 that can detect the in-cylinder pressure in real time is used to calculate the combustion speed during flame propagation immediately after ignition, and when it is determined that the combustion speed is insufficient, the crank angle is During the same cycle before the bottom dead center (BDC) of the expansion stroke and before the exhaust valve was opened, the second fuel injection was performed.

  A more specific outline of control will be described with reference to FIGS. FIG. 5 is a diagram for explaining torque fluctuation when the second fuel injection is performed during the current cycle. Line 66 shows the second fuel injection when there is a possibility of misfiring or the combustion speed is insufficient when an appropriate fuel injection amount corresponding to the target air-fuel ratio is not injected at the restart from the idling stop. It is a PV diagram at the time of implementing.

  In order to ensure the required torque in the current cycle, 2 2 is used to compensate for the area A that is insufficient compared to the case where normal combustion occurs when restarting from the idling stop (line 62 in FIG. 5). It is necessary to increase the area of the region B in the line 66 by performing the second fuel injection so that the region A and the region B coincide with each other.

  FIG. 6 is a diagram showing a change in the in-cylinder pressure when the second fuel injection is performed, and a relationship between the combustion speed and the torque. The combustion speed α1 shown in FIG. 6 (A) is the case where there is a possibility of misfire or the combustion speed is insufficient when the appropriate fuel injection amount f1 corresponding to the target air-fuel ratio is not injected when restarting from the idling stop. The combustion speed at a certain crank angle θ1 is shown (similar to the combustion speed β in FIG. 3). In the example shown in FIG. 6A, since the combustion speed α1 is lower than the combustion speed α (FIG. 3) on the line 62, the additional fuel amount is injected at the crank angle θ2 in order to ensure the necessary torque.

  Next, a method for calculating the additional fuel amount will be described. If the cooling loss is the same after combustion, the torque generated up to the exhaust valve opening timing (EVO) is proportional to the combustion speed (dP / dθ) (FIG. 6B). Therefore, the second fuel injection amount f2 corresponding to the deviation between the combustion speed α and the combustion speed α1 is calculated as the additional fuel amount. Specifically, the ECU 50 stores in advance an f2 relationship map in which the second fuel injection amount f2 increases as the deviation between the combustion speed α and the combustion speed α1 increases at the crank angle θ2. The ECU 50 calculates the fuel injection amount f2 corresponding to the deviation from the f2 relationship map.

  Thus, in the control of this embodiment, the combustion speed α1 at the crank angle θ1 during flame propagation immediately after ignition is calculated, and when the combustion speed is insufficient (α1 <α), the expansion stroke in the same cycle is calculated. The fuel injection amount f2 corresponding to the deviation between the combustion speeds α and α1 is additionally injected at the bottom dead center and the crank angle θ2 before the exhaust valve is opened.

  FIG. 7 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described operation. This control routine is executed in the first combustion cylinder at the time of restart from idling stop. In the routine shown in FIG. 7, first, the ECU 50 calculates an appropriate fuel injection amount f1 corresponding to the target air-fuel ratio when restarting from the idling stop, and injects it into the direct injection injector 14 (step S100).

  After the control for injecting the fuel injection amount f1, the ECU 50 causes the spark plug 12 to ignite fuel at a predetermined crank angle (for example, MBT: Minimum Advance for Best Torque) (step S110). Thereafter, the ECU 50 calculates a combustion speed α1 (dP / dθ) as a combustion state index at a predetermined crank angle (crank angle θ1) during flame propagation immediately after ignition (step S120).

  Whether the combustion speed α1 at the crank angle θ1 in the current cycle is larger than the combustion speed α at the crank angle θ1 when the proper fuel injection amount f1 corresponding to the target air-fuel ratio is injected and normal combustion is performed at the restart from the idling stop. It is determined whether or not (step S130). If the determination condition in step S130 is satisfied, then the processing of this routine is terminated.

  On the other hand, when the determination condition of step S130 is not satisfied, it can be determined that the injection does not satisfy the fuel injection amount f1. Therefore, the ECU 50 calculates the second fuel injection amount f2 as the additional fuel amount. The fuel injection amount f2 is calculated based on the deviation between the combustion speeds α and α1 using the above-described f2 relationship map (step S140).

  Next, it is determined whether or not the fuel pressure has risen above the set value and the crank angle θ is at the bottom dead center of the expansion stroke and before the exhaust valve is opened (step S150). As the set value, a value that can ensure a sufficient spray pressure is set according to the fuel properties. Further, as the crank angle θ, for example, the crank angle θ2 of FIG. 6 described above is set. When the determination condition in step S150 is satisfied, the fuel injection amount f2 is injected as the second fuel injection in the current combustion cylinder in the same cycle (step S160).

  On the other hand, if the determination condition in step S150 is not satisfied, it can be determined that the second combustion injection cannot be performed in the current combustion cylinder during the same cycle. In this case, the fuel injection amount f2 is corrected to increase to the basic injection amount of the next combustion cylinder to obtain the fuel injection amount f1 in the next combustion cylinder. The next combustion cylinder is a cylinder in which a combustion stroke is performed next among the plurality of cylinders, and the basic injection amount is an appropriate fuel injection amount corresponding to the target air-fuel ratio in the next combustion cylinder.

As described above, according to the control routine shown in FIG. 7, when the determination condition of step S150 is satisfied, the fuel injection amount f2 can be injected into the current combustion cylinder in the same cycle. By performing the second fuel injection during the same cycle, it is possible to secure the necessary torque in the same cycle and to ensure high startability. Further, by injecting the additional fuel amount, misfire can be avoided and emission can be improved.
Further, according to the routine shown in FIG. 7, even if the determination condition of step S150 is not satisfied and additional fuel cannot be injected in the current combustion cylinder, the first fuel injection amount of the next combustion cylinder is set. Increase correction can be performed. Therefore, startability deterioration can be minimized. According to such control, it is possible to achieve high startability and suitable emission when restarting from an idling stop.

  In the system of the above-described embodiment, the fuel injection amount f2 is calculated based on the combustion speed. However, the method for calculating the fuel injection amount f2 is not limited to this. For example, it may be calculated based on the integrated value of the in-cylinder pressure. Specifically, the ECU 50 stores in advance an integrated value of the combustion pressure from the crank angle during ignition during normal combustion to the crank angle after ignition. Further, the ECU 50 calculates the integrated value of the actual combustion pressure from the crank angle at the time of ignition detected by the in-cylinder pressure sensor 16 to the crank angle θ2. Then, the larger the difference between the stored integrated value during normal combustion and the calculated integrated value of actual combustion pressure, the larger the additional fuel amount may be calculated.

In the above-described embodiment, the direct injection injector 14 is the “direct injection injector” in the first invention, the in-cylinder pressure sensor 16 is the “in-cylinder pressure acquisition means” in the first invention, and the crank angle sensor. Reference numeral 18 corresponds to the “crank angle acquisition means” in the first invention.
In addition, here, the ECU 50 executes the process of step S120, so that the “combustion speed calculating means” in the first invention executes the process of step S130, so that the “combustion” in the first invention is executed. The “speed determining means” executes the processes of steps S140 to S160, so that the “current combustion cylinder correcting means” in the first invention executes the processes of step S140. The “additional fuel amount calculating means” executes the process of step S150, so that the “post-ignition crank angle determining means” of the third invention executes the process of step S170. "Next combustion cylinder correcting means" is realized.

P In-cylinder pressure V In-cylinder volume f1, f2 Fuel injection amount α, β, α1, α2 Combustion speed θ, θ1, θ2 Crank angle 10 Engine 12 Spark plug 14 Direct injection injector 15 Fuel pressure sensor 16 In-cylinder pressure sensor 18 Crank angle sensor 20 Intake passage 24 Air flow meter 30 Intake pressure sensor 32 Exhaust passage 34 Catalyst 50 ECU (Electronic Control Unit)

Claims (6)

A direct injection injector that directly injects fuel into a cylinder of an internal combustion engine;
In-cylinder pressure acquisition means for acquiring the combustion pressure in the cylinder;
Crank angle acquisition means for acquiring a crank angle of the internal combustion engine;
A combustion speed calculating means for calculating a combustion speed by dividing a combustion pressure at a crank angle during propagation of a flame after ignition acquired by the in-cylinder pressure acquiring means (hereinafter referred to as a crank angle after ignition) by a unit crank angle;
Combustion speed determination means for determining whether or not the combustion speed is lower than a reference combustion speed during normal combustion at the crank angle after ignition;
Current combustion cylinder correction means for injecting an additional amount of fuel into the current combustion cylinder in the same cycle as the cycle in which the combustion speed is calculated when the combustion speed is lower than the reference combustion speed;
A control device for an internal combustion engine, comprising: An additional fuel amount calculating means for calculating the additional fuel amount to be larger as the deviation between the reference combustion speed and the combustion speed is larger;
The control apparatus for an internal combustion engine according to claim 1, further comprising: A post-ignition crank angle determining means for determining whether a condition that the post-ignition crank angle is before bottom dead center and before exhaust valve opening in the expansion stroke is satisfied;
And further comprising a next combustion cylinder correcting means for correcting a predetermined amount of fuel to be increased to a basic injection amount in the next combustion cylinder when the combustion speed is lower than the reference combustion speed and the condition is not satisfied,
The current combustion cylinder correction means adds the current combustion cylinder to the current combustion cylinder in the same cycle as the cycle in which the combustion speed is calculated when the combustion speed is lower than the reference combustion speed and the condition is satisfied. Injecting fuel quantity,
The control apparatus for an internal combustion engine according to claim 1 or 2, characterized by the above-mentioned.   The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the predetermined fuel amount that is corrected to be increased by the next combustion cylinder correcting means is the same amount as the additional fuel amount. Storage means for storing in advance an integrated value of the combustion pressure from the crank angle at the time of ignition during normal combustion to the crank angle after ignition;
Calculating means for calculating an integrated value of the combustion pressure from the crank angle at the time of ignition acquired by the in-cylinder pressure acquiring means to the crank angle after ignition;
Means for calculating the amount of additional fuel larger as the deviation between the integrated value stored in the storage means and the integrated value calculated by the calculating means increases;
The control apparatus for an internal combustion engine according to claim 1, further comprising:   The control apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the in-cylinder pressure acquisition means is an in-cylinder pressure sensor.

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