JP2004137960A - Fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress HC emission even when no reverse flow of intake air from a combustion chamber to an intake passage is generated. <P>SOLUTION: The fuel injection device comprises the intake passage 14 communicated with the combustion chamber 13, an intake valve 7 capable of blocking communication of the combustion chamber 13 with the intake passage 14, a variable valve mechanism for changing opening/closing timing of the intake valve 7, a means 11 for detecting reverse flow in the intake passage 14, a fuel injection means for switching an injecting direction into to two different directions, and a fuel injection control device 1 for controlling the injecting direction of the fuel injection means. The injecting direction of the fuel injecting means is switched according to a detecting signal from the reverse flow detecting means 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to a fuel injection device for reducing the amount of HC emission.
[0002]
[Prior art]
2. Description of the Related Art There is known a fuel injection device for an internal combustion engine in which one fuel injector is provided in the middle of an intake passage of each cylinder, and fuel is injected from the fuel injector toward an intake passage (Patent Document 1).
[0003]
[Patent Document 1]
JP-A-7-77139
[Problems to be solved by the present invention]
However, in the fuel injection device as disclosed in Patent Document 1, the fuel injector is always fixed in a fixed direction, so that the fuel injection axis of the fuel injector and the direction in which the intake air flows form a predetermined angle. Therefore, fuel can be injected toward the head of the intake valve at a predetermined flow rate of intake air, but when the flow direction of the injected fuel changes due to an increase or decrease in the flow rate of the intake air, fuel spray is applied to the intake valve. Is bent in a direction to come off the umbrella part. As a result, the fuel spray not directed to the umbrella portion of the intake valve adheres to the wall surface of the intake passage and forms a fuel wall flow.
[0005]
These fuels enter the combustion chamber without being vaporized, move in the direction of the exhaust valve, and adhere to the vicinity of the exhaust valve, thereby causing the emission of HC.
[0006]
In particular, the wall flow that has flowed into the combustion chamber from the intake passage wall above the intake valve (upward of the combustion chamber) tends to adhere to the vicinity of the exhaust valve.
[0007]
Therefore, the present invention prevents the non-vaporized fuel from flowing into the combustion chamber from the intake passage wall above the intake valve (upward of the combustion chamber), thereby preventing the wall flow from adhering around the exhaust valve. And reducing the emission of HC.
[0008]
[Means for Solving the Problems]
The present invention provides an intake passage communicating with a combustion chamber, an intake valve capable of cutting off the communication between the combustion chamber and the intake passage, a variable valve mechanism for changing the opening / closing timing of the intake valve, A means for detecting backflow, a fuel injection means provided in the intake passage and capable of switching an injection direction to two different directions, and a fuel injection control device for controlling the injection direction of the fuel injection means, The injection direction of the fuel injection means is switched according to a detection signal from the detection means.
[0009]
[Action / Effect]
According to the present invention, in a situation where there is no blowback (backflow) of the intake air from the inside of the cylinder to the intake passage, and the fuel adhering near the intake valve is unlikely to vaporize, only the lower side (the cylinder wall side) of the intake valve. Since the fuel is injected, unvaporized fuel does not adhere to the intake passage wall above the intake valve (upward of the combustion chamber) to cause a wall flow.
[0010]
Therefore, the wall flow does not flow into the combustion chamber from above the intake valve, and it is possible to prevent non-vaporized fuel from adhering around the exhaust valve. As a result, the emission of HC can be reduced.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 is a configuration diagram of an internal combustion engine used in the first embodiment, and shows one cylinder of a multi-cylinder internal combustion engine.
[0013]
Similar to a conventional internal combustion engine, a cylinder head 16 is fixed to an upper portion of a cylinder block 15, and a combustion chamber 13 is formed between an upper surface 18 a of a piston 18 and a lower surface of the cylinder head 16.
[0014]
The cylinder head 16 is provided with an intake passage 14 and an exhaust passage 17 facing each other for each cylinder, and communicates with the combustion chamber 13.
[0015]
The intake passage 14 includes an intake port 14a and an intake pipe 14b. The upstream side is connected to the throttle chamber 3 and the air flow meter 2 via the collector tank 4, and the downstream side is connected to the combustion chamber 13. Further, the intake passage 14 is provided with fuel injectors 5 and 6, which are features of the present invention, and a backflow detection sensor 11 for detecting a return (backflow) of intake air from the combustion chamber 13 to the intake passage 14. The fuel injectors 5, 6 are mounted so as to inject fuel in different directions.
[0016]
The exhaust passage 17 also includes an exhaust port 17a and an exhaust pipe 17b. The upstream side is connected to the combustion chamber 13 and the downstream side is connected to a catalyst (not shown).
[0017]
The intake passage 14 and the exhaust passage 17 can be cut off from the communication with the combustion chamber 13 by an intake valve 7 and an exhaust valve 8 attached to each cylinder 15b so as to be openable and closable. Not driven by a valve train.
[0018]
In particular, the intake valve 7 is driven by a variable valve mechanism that can change the opening and closing period according to the traveling state.
[0019]
Since the variable valve mechanism is a well-known technique, a detailed description thereof will be omitted. The structure and operation of the variable valve mechanism are disclosed in, for example, JP-A-2002-89305. Used.
[0020]
A spark plug 9 is provided between the intake valve 7 and the exhaust valve 8 so as to correspond to a substantially axis of the cylinder 15b, and the spark plug 9 is connected to an ignition coil 10.
[0021]
Below the cylinder block 15, a crank angle sensor 12 for detecting a rotation angle of a crank shaft 19 is provided.
[0022]
Signals from the air flow meter 2, the throttle position sensor 3a provided in the throttle chamber 3, the backflow detection sensor 11, and the crank angle sensor 12 are read into an engine control unit (hereinafter, ECM) 1, and the ECM 1 is based on these signals. , The fuel injectors 5 and 6 are switched, and the opening and closing period of the intake valve 7 is controlled.
[0023]
Next, the injection directions of the fuel injectors 5 and 6 will be described with reference to FIGS.
[0024]
FIG. 2 is an enlarged view of the vicinity of the intake valve 7 and the fuel injectors 5 and 6 in FIG. 1, and FIG. 3 is a top view of FIG. 2, in which the injection state at the time of fuel injection is shown as a shaded portion.
[0025]
The fuel injector 5 injects fuel so as to impinge on the entire head portion 7a of the intake valve 7, and the fuel injector 6 injects fuel so as to impinge only on the lower side (on the side of the cylindrical wall 15a) of the head portion 7a of the intake valve 7. So that it is attached.
[0026]
Next, control of the fuel injection device performed by the ECM 1 in the present invention will be described with reference to the flowchart of FIG. In the flowchart, the fuel injector 5 is referred to as an injector 1 (INJ1), and the fuel injector 6 is referred to as an injector 2 (INJ2).
[0027]
In step S11, the fuel injection time TP is read.
[0028]
In step S12, the engine speed EngREV is read based on the detection signal from the crank angle sensor.
[0029]
In step S13, a detection signal from the backflow detection sensor 11 is read.
[0030]
In step S14, it is determined whether or not there is a backflow in the intake passage based on the values read in steps S11 to S13. If there is, the flow proceeds to step S15, and if not, the flow proceeds to step S16.
[0031]
When there is a backflow and the process proceeds to step S15, the fuel injector 5 (INJ1) is injected with a pulse width TP. When there is no backflow and the process proceeds to step S16, the fuel injector 6 (INJ2) is injected with a pulse width TP. .
[0032]
The effects of the above embodiment will be described with reference to FIG.
[0033]
FIG. 10 shows the vicinity of the intake valve 7. When there is no backflow from the combustion chamber 13 into the intake passage 14, the fuel adhering to the upper portion of the intake valve head 7 a or the upper portion of the intake passage 14 is unlikely to vaporize, and the unvaporized fuel flows toward the exhaust valve 9. The scattered particles adhere to the lower cylindrical wall C of the exhaust valve 9 and cause HC discharge.
[0034]
However, in the present embodiment, when there is no backflow from the combustion chamber 13 to the intake passage 14, the fuel is injected by the fuel injector 6 so as to hit only the lower side of the intake valve, so that the fuel that does not vaporize accumulates above the intake valve 7. Is gone. Therefore, non-vaporized fuel does not adhere to the exhaust valve 9 side, so that the amount of HC emission can be reduced.
[0035]
When considering the air-fuel mixture sucked into the combustion chamber 13, it is ideal that the fuel is evenly distributed in the air-fuel mixture. Therefore, in a state in which the injected fuel is easily vaporized, the fuel is uniformly injected into the entire intake valve head portion 7a using the INJ1 so that the fuel distribution in the air-fuel mixture approaches evenly.
[0036]
Next, a second embodiment will be described.
[0037]
FIG. 5 is a flowchart showing the control according to the second embodiment.
[0038]
In the present embodiment, only the step S23 corresponding to the step S13 in the first embodiment is different.
[0039]
In step S23, it is determined whether or not there is a backflow based on the fuel injection time TP and the engine speed EngREV read in steps S21 and S22, using the backflow determination map (FIG. 8) obtained in advance. .
[0040]
When there is a backflow, the process proceeds to step S25, and when there is no backflow, the process proceeds to step S26.
[0041]
According to the present embodiment, in addition to the effects of the first embodiment, it is not necessary to provide a backflow detection sensor, so that the cost can be reduced.
[0042]
By using the present invention, it is possible to open and close the intake valve at various times while suppressing the amount of HC emission, so that it is also possible to realize a Miller cycle in which the intake pipe pressure becomes the atmospheric pressure. is there.
[0043]
By the way, when operating the engine in the Miller cycle, it is preferable to set the intake and exhaust valve opening / closing timing as shown in FIG.
[0044]
In the Miller cycle, the pressure in the intake passage 14 is set to the atmospheric pressure with the throttle fully open, and the amount of intake air is adjusted according to the intake valve opening / closing timing.
[0045]
Therefore, during high load operation, as shown in FIG. 8, the cylinder pressure is higher than the atmospheric pressure near the intake top dead center (intake TDC) where the intake valve 7 is open, so that a backflow to the intake passage 14 occurs, but the low load During operation, as shown in FIG. 9, the in-cylinder pressure is close to the atmospheric pressure near the intake TDC, so that no backflow to the intake passage 14 occurs.
[0046]
For this reason, in the conventional fuel injection device, during low load operation in which backflow from the combustion chamber 13 to the intake passage 14 does not occur, non-vaporized fuel is generated near the intake valve, which moves and adheres near the exhaust valve. As a result, the amount of HC emission increased, and it was difficult to put it to practical use.
[0047]
However, there is no backflow from the combustion chamber 13 to the intake passage 14 by using the fuel injection device of the present invention, that is, during low load operation, by injecting fuel so that the fuel only strikes the lower side of the intake valve head 7a. Also in this case, generation of fuel that does not vaporize near the upper side of the intake valve 7 can be suppressed, and an increase in the amount of HC emission during low load operation can be suppressed, so that the Miller cycle can be put to practical use.
[0048]
In addition, as shown in FIG. 11, it is possible to switch between two injection directions, an injection direction in which fuel strikes the entire intake valve head 7a and an injection direction in which fuel strikes only the lower side of the head 7a. The same effect as in the above-described embodiment can be obtained by switching the injection direction using a suitable fuel injector in the same manner as the switching of INJ1 and INJ2 in the above-described embodiment.
[0049]
It is needless to say that the present invention is not limited to the above-described embodiment, and various changes can be made within the scope of the technical idea described in the claims.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a system configuration according to a first embodiment of the present invention.
FIG. 2 is a diagram (transverse sectional view) illustrating an injection state of the fuel injector according to the first embodiment.
FIG. 3 is a diagram (top view) illustrating an injection state of the fuel injector of the first embodiment.
FIG. 4 is a flowchart illustrating a control routine according to the first embodiment.
FIG. 5 is a flowchart illustrating a control routine according to a second embodiment.
FIG. 6 is a backflow determination map.
FIG. 7 is a diagram showing the intake / exhaust valve opening / closing timing in the Miller cycle.
FIG. 8 is a diagram illustrating a relationship between in-cylinder pressure and intake valve opening / closing timing during a high load operation in a Miller cycle.
FIG. 9 is a diagram illustrating a relationship between in-cylinder pressure and intake valve opening / closing timing during low load operation in a Miller cycle.
FIG. 10 is a diagram illustrating a flow of fuel that does not vaporize near an intake valve.
FIG. 11 is a view (transverse cross-sectional view) illustrating an injection state when a fuel injector capable of switching injection in different directions is used.
[Explanation of symbols]
1 Engine control unit (ECM)
2 Air flow meter 3 Throttle chamber 4 Collector tank 5 Fuel injector (INJ1)
6 Fuel injector (INJ2)
Reference Signs List 7 Intake valve 7a Intake valve head 8 Exhaust valve 9 Spark plug 10 Ignition coil 11 Backflow detection sensor 12 Crank angle sensor 13 Combustion chamber 14 Intake passage 15 Cylinder block 16 Cylinder head 17 Exhaust passage 18 Piston 19 Crankshaft

Claims (4)

An intake passage communicating with the combustion chamber;
An intake valve that can shut off communication between the combustion chamber and the intake passage;
Means for detecting a backflow from the combustion chamber to the intake passage;
Fuel injection means provided in the intake passage and capable of switching an injection direction to two different directions,
A fuel injection control device that controls an injection direction of the fuel injection means,
A fuel injection device for an internal combustion engine, wherein an injection direction of a fuel injection unit is switched according to a detection signal from the backflow detection unit. When the backflow detecting means detects the backflow in the intake passage, the fuel is injected toward the entire intake valve, and when the backflow is not detected, the fuel is injected toward the portion of the intake valve on the cylinder wall side. The fuel injection device for an internal combustion engine according to claim 1, wherein the switching is performed in such a manner. 3. The fuel injection device for an internal combustion engine according to claim 2, wherein the fuel injection means is two fuel injectors installed so as to inject in different directions. The fuel injection device for an internal combustion engine according to claim 2, wherein the fuel injection means is a single fuel injector that can switch a fuel injection direction between two different directions.

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