JP4158494B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an internal combustion engine used for an automobile or the like is known that includes a variable compression ratio mechanism that can change the compression ratio setting according to engine operating conditions such as combustion pressure and engine rotation. (See Patent Document 1.)
[0003]
[Patent Document 1]
JP 2001-263114 A (second page)
Further, in an internal combustion engine having an injector for each cylinder and having a variable compression ratio mechanism, knocking is more likely to occur as the engine operating condition becomes higher. Therefore, when the throttle is fully opened (WOT), In order to suppress knocking, it is necessary to lower the compression ratio.
[0004]
[Problems to be solved by the invention]
Therefore, there is a problem that the engine torque generally decreases due to a decrease in combustion efficiency due to a decrease in compression ratio.
[0005]
In order to suppress the reduction of the compression ratio when the engine operating conditions are high, there is a method of suppressing the knocking by the intake stroke injection of the fuel. However, the reduction margin of the compression ratio is reduced by performing the intake stroke injection of the fuel. Even if this is suppressed, there is a limit in improving the torque of the engine.
[0006]
[Means for Solving the Problems]
An internal combustion engine control apparatus according to the present invention includes a variable compression ratio mechanism capable of changing a compression ratio setting in accordance with an operating state of the engine, and an intake air amount control means for controlling an intake air amount into a combustion chamber of the internal combustion engine. The first injector and the second injector having a larger fuel injection amount per unit time than the first injector, and the engine load region is relatively higher than the first load region and the first load region. The first load region is divided into two regions, i.e., the second load region, the fuel is injected from the first injector, the intake air amount is gradually increased as the engine load increases, and the first load region When the engine load increases, the compression ratio is gradually lowered from a predetermined reference compression ratio, and when the engine load shifts from the first load region to the second load region, the compression ratio is reduced to the reference compression ratio. The intake air amount is once reduced and the intake air amount is once reduced. In the second load region, fuel is injected from the second injector, and the intake air amount is gradually increased as the engine load increases, and predetermined as the engine load increases. The compression ratio is gradually lowered from the standard compression ratio .
[0007]
【The invention's effect】
According to the present invention, by selectively using different injectors over the fuel injection rate depending on the load, it is possible to maximize the torque when the throttle is fully open in the internal combustion engine with a variable compression ratio mechanism, generally the engine load region The torque can be improved over a wide range.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0009]
FIG. 1 is an explanatory diagram showing a schematic configuration of a control device for an internal combustion engine according to the present invention applied to a vehicle.
[0010]
The air taken in from the outside is introduced into the intake collector 2 through the air cleaner 1 and is distributed from the intake collector 2 to a plurality of branches 3 branched according to the number of cylinders of the internal combustion engine.
[0011]
Between the intake collector 2 and the air cleaner 1, there is disposed a throttle valve 5 as intake air amount control means for controlling the intake air amount into the combustion chamber 4 in accordance with the engine operating state. An air flow meter 6 is disposed between the throttle valve 5 and the air cleaner 1.
[0012]
The throttle valve 5 is controlled by an engine control module 7 (hereinafter referred to as ECM). Further, an output signal from the air flow meter 6 is input to the ECM 7.
[0013]
The branch 3 communicates with the combustion chamber 4 of the corresponding cylinder via the intake valve 8. The branch 3 is provided with a pair of injectors including a first injector 9 and a second injector 10 having different fuel injection rates. The first injector 9 is set to have a smaller fuel injection rate than the second injector 10. Here, the fuel injection rate is the ratio of the amount of fuel injected from the injector to the time, and is the amount of fuel injected per unit time. The first injector 9 and the second injector 10 are controlled by the ECM 7 according to the engine operating state (specific control will be described later).
[0014]
In FIG. 1, 11 is an exhaust passage, 12 is an exhaust valve, 13 is a spark plug, 14 is a vehicle driver's accelerator pedal depression amount (accelerator pedal opening) detected as an internal combustion engine load and input to the ECM 7. It is an accelerator pedal sensor as means for detecting the load of the internal combustion engine, that is, means for detecting the engine operating state. Although not shown, the ECM 7 detects the engine speed based on a signal from a crank angle sensor. For convenience, FIG. 1 focuses on one cylinder of a multi-cylinder internal combustion engine. From the intake collector 2 in FIG. 1, the same number of branches 3,... A pair of injectors composed of a first injector 9 and a second injector 10 is provided for each of the branches 3.
[0015]
The internal combustion engine also includes a variable compression ratio mechanism 20 that can change the setting of the compression ratio according to the operating state of the engine.
[0016]
The variable compression ratio mechanism 20 includes an upper link 23 having one end connected to a piston 21 of each cylinder via a piston pin 22, and a swing link connected to the other end of the upper link 23 via an upper link pin 24. And a lower link 27 connected to the crankpin 26 of the crankshaft 25, a control shaft 28 extending substantially parallel to the crankshaft 25, one end of which is swingably connected to the control shaft 28 and the other end. Has a control link 30 that is swingably connected to the lower link 27 via a control link pin 29.
[0017]
A pin journal (not shown) rotatably supported by a bearing (not shown) provided at one end of the control link 30 is intermittently formed on the control shaft 28 in the axial direction of the crankshaft 25. Yes.
[0018]
The rotation center P1 of the pin journal is eccentric by a predetermined amount with respect to the rotation center P2 of the control shaft 28, and the control link 30 swings with respect to the control shaft 28 using the rotation center P1 as a swing fulcrum.
[0019]
Therefore, when the control shaft 28 rotates, the position of the swing fulcrum P1 of the control link 30 changes, and accordingly, the piston top dead center position changes. That is, the compression ratio of the internal combustion engine defined by the ratio of the combustion chamber side volume at the piston top dead center position and the combustion chamber side volume at the piston bottom dead center position can be increased or decreased.
[0020]
The control shaft 28 is rotationally driven using an actuator 33 connected via a worm 31 and a worm wheel 32 as a drive source, and the actuator 33 is driven and controlled by the ECM 7 in accordance with the engine operating state.
[0021]
The control by the ECM according to the engine operating state of the throttle valve 5, the variable compression ratio mechanism 20, and the pair of injectors 9 and 10 disposed for each cylinder is performed as shown in FIG.
[0022]
First, the engine load region is divided into two regions, a first load region and a second load region having a relatively larger engine load than the first load region, with a predetermined accelerator pedal depression amount APO1 set in advance as a boundary. Divide into
[0023]
In the first load region, fuel is injected from the first injector 9 having a small fuel injection rate during the intake stroke, and fuel is not injected from the second injector 10 having a fuel injection rate larger than that of the first injector 9. On the other hand, the variable compression ratio mechanism 20 is controlled so as to have a predetermined reference compression ratio on the low load side in the first load region, that is, on the side where the accelerator pedal depression amount is small, so that the accelerator pedal depression amount becomes APO1. Since knocking is likely to occur when approaching, the compression ratio is controlled to gradually decrease from the reference compression ratio on the high load side in the first load region. Here, the reference compression ratio is a compression ratio at which the thermal efficiency of the engine is maximized, and is approximately about the compression ratio 15. The throttle valve 5 is substantially fully closed when the accelerator pedal depression amount is 0, and is substantially fully opened when the accelerator pedal depression amount is APO1. It gradually opens toward the higher side.
[0024]
When the amount of depression of the accelerator pedal reaches APO1, the compression ratio is once increased to the reference compression ratio, and the throttle valve is throttled from the fully open state to a predetermined amount at a time to temporarily reduce the intake air amount.
[0025]
In the second load region, fuel is injected from the second injector 10 having a large fuel injection rate during the intake stroke, and fuel is not injected from the first injector 9 having a fuel injection rate smaller than that of the second injector 10. On the other hand, the variable compression ratio mechanism 20 is controlled so that the compression ratio gradually decreases from the reference compression ratio as the accelerator pedal depression amount increases from APO1. The throttle valve 5 is controlled to gradually increase as the accelerator pedal depression amount increases from APO1, and the accelerator pedal depression amount is maximum, that is, the accelerator pedal is fully depressed (accelerator pedal depression amount APO2). Then the throttle valve is almost fully opened again.
[0026]
FIG. 3 is a flowchart showing a control flow of the control device for the internal combustion engine described above.
[0027]
In step 1 (hereinafter, step is simply referred to as S), the accelerator pedal depression amount APO is input to the ECM 7 from the accelerator pedal sensor 14.
[0028]
In S2, the throttle opening corresponding to the accelerator pedal depression amount APO and the target compression ratio are read out from a table (see FIG. 2 described above) stored in advance in the ECM 7.
[0029]
In S3, the ECM 7 reads the intake air amount based on a signal from the air flow meter 6, and reads the engine speed based on a signal from a crank angle sensor (not shown).
[0030]
In S4, the currently required fuel injection amount is calculated.
[0031]
In S5, it is determined whether or not the accelerator pedal depression amount APO input to the ECM 7 in S1 is smaller than the above-mentioned APO1, and if APO is less than APO1, the process proceeds to S6, and otherwise proceeds to S8. .
[0032]
In S6, the first injector 9 calculates the injection pulse width necessary for securing the fuel injection amount calculated in S4, proceeds to S7, injects fuel from the first injector 9, and proceeds to S10.
[0033]
In S8, the second injector 10 calculates the injection pulse width necessary for securing the fuel injection amount calculated in S4, proceeds to S9, injects fuel from the second injector 10, and proceeds to S10.
[0034]
In S10, the actuator 33 is driven to achieve the target compression ratio read in S2.
[0035]
In S11, the throttle valve 5 is driven so as to reach the target throttle opening degree read in S2.
[0036]
In such a control apparatus for an internal combustion engine, when the accelerator pedal depression amount APO reaches APO1, the throttle valve 5 is substantially fully opened, so that fuel is injected from the second injector 10 having a large fuel injection rate in the second load region. And knocking can be suppressed by the latent heat of vaporization of the fuel. This suppression of knocking is due to the fact that when fuel is injected during the intake stroke, the liquid fuel spray is directly sucked into the cylinder, and the inside of the cylinder is cooled by the latent heat of vaporization when the fuel vaporizes in the cylinder. When the second injector 10 is used during the intake stroke, the fuel injection amount per unit time is larger than that of the first injector 9, so that the injection end timing is earlier than that of the first injector 9, and as a result Since the vaporization time can be increased and the in-cylinder cooling effect can be effectively utilized, the compression ratio can be increased again, and the throttle valve 5 can be throttled by increasing the torque by increasing the compression ratio. In the second load region, when the accelerator pedal depression amount APO becomes larger than APO1, the compression ratio has to be lowered. However, when the accelerator pedal depression amount APO is the maximum value APO2, the throttle valve 5 is again fully opened. can do.
[0037]
In other words, the engine load area is divided into a low load area (first load area) and a high load area (second load area), and different injectors with different fuel injection rates are used in the low load area and the high load area. As a result, the throttle valve 5 is fully opened and the maximum torque is generated at the two points of the boundary between the low load region and the high load region and the maximum load, that is, the accelerator pedal depression amount APO1 and the accelerator pedal depression amount APO2. Therefore, it is possible to extract the maximum torque when the throttle is fully opened in the internal combustion engine having the variable compression ratio mechanism, and it is possible to improve the torque over a wide range of the engine load region as a whole.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a control device for an internal combustion engine according to the present invention.
FIG. 2 is an explanatory diagram showing a correlation of control of an injector, a compression ratio, and a slot opening degree with respect to an engine load.
FIG. 3 is a flowchart showing a control flow of a control device for an internal combustion engine according to the present invention.
[Explanation of symbols]
5 ... Throttle valve 7 ... Engine control module (ECM)
9 ... 1st injector 10 ... 2nd injector 14 ... Accelerator pedal sensor 20 ... Variable compression ratio mechanism

Claims (2)

A variable compression ratio mechanism that can change the setting of the compression ratio according to the operating state of the engine;
  Intake air amount control means for controlling the amount of intake air into the combustion chamber of the internal combustion engine;
  The first injector,
  A second injector having a fuel injection amount per unit time larger than that of the first injector;
  The engine load region is divided into two regions, a first load region and a second load region where the engine load is relatively larger than the first load region,
  In the first load region, fuel is injected from the first injector, the intake air amount is gradually increased as the engine load increases, and the engine is compressed from a predetermined reference compression ratio when the engine load increases in the first load region. Gradually lower the ratio,
  When the engine load shifts from the first load region to the second load region, the compression ratio is once increased to the reference compression ratio and the intake air amount is once reduced.
  In the second load region, fuel is injected from the second injector, the intake air amount is gradually increased as the engine load increases, and the compression ratio is gradually increased from a predetermined reference compression ratio as the engine load increases. A control device for an internal combustion engine characterized by being lowered. A variable compression ratio mechanism that can change the setting of the compression ratio according to the operating state of the engine;
  Intake air amount control means for controlling the amount of intake air into the combustion chamber of the internal combustion engine;
  The first injector,
  A second injector having a fuel injection amount per unit time larger than that of the first injector;
  The engine load region is divided into two regions, a first load region and a second load region where the engine load is relatively larger than the first load region,
  In the first load region, fuel is injected from the first injector, and when the engine load increases in the first load region, the compression ratio is gradually lowered from a predetermined reference compression ratio,
  When the engine load shifts from the first load region to the second load region, the compression ratio is temporarily increased to the reference compression ratio,
  In the second load region, a control device for an internal combustion engine, wherein fuel is injected from a second injector and the compression ratio is gradually lowered from a predetermined reference compression ratio as the engine load increases.

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