JP2004011614A - Spark ignition type direct injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark ignition type direct injection engine where injected fuel does not attach to a wall of a combustion chamber and which forms a proper fuel-air mixture at the time of a high-speed operation of an engine, and combustion efficiency is enhanced by accelerating stratification of fuel at the time of a low-speed operation of the engine, without requiring special members. <P>SOLUTION: A main flow of intake air passing through both intake air ports 10 proceeds along the circumference of the combustion chamber 7 to a wall facing both intake air ports 10 (inflow T1), is circulated by a mask 11 toward the lower part of a range S injected by an injector 9 (outflow T2), and forms a hyperbolic flow T. The inflow T1 flows into the combustion chamber 7 without circulating the fuel injected by the injector 9, and the outflow T2 is pushed up upward in a compression process, so that this hyperbolic flow T suppresses diffusion of the injected fuel. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a spark ignition type direct injection engine in which fuel is directly injected from an injector to a spark plug.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known a spark ignition type direct injection engine which includes an injector for directly injecting fuel into a combustion chamber in addition to an ignition plug to improve fuel efficiency by stratified combustion. This type of engine promotes vaporization and atomization while suppressing the diffusion of fuel, and creates a state in which an air-fuel mixture with an appropriate ignitable air-fuel ratio is unevenly distributed near the spark plug electrode (that is, stratification). It is required to secure.
[0003]
As such a technique, for example, an in-cylinder injection spark ignition internal combustion engine as disclosed in JP-A-2001-248443 is known. According to this internal combustion engine, the gas injection valve provided in the vicinity of the fuel injection valve forms an air curtain in the cylinder, and the fuel spray injected from the fuel injection valve by the air curtain is directed downward and laterally with respect to the ignition plug. The diffusion in the direction is suppressed.
[0004]
[Problems to be solved by the invention]
When an air curtain is formed by the gas injection valve to suppress the diffusion of the fuel spray as described above, during the low-speed operation of the engine, the fuel is stratified near the spark plug by performing the compression stroke injection of the fuel. This has the advantage that the combustion efficiency can be improved. However, in this case, it is difficult to sufficiently secure combustion robustness due to insufficient suppression of diffusion of the fuel spray in the traveling direction. Also, in the case of performing the intake stroke injection of fuel during high-speed operation of the engine, the fuel injected into the combustion chamber due to the intake air flows into the combustion chamber from the injector side toward the wall surface of the combustion chamber facing the intake port. Is flowing and adheres to the wall surface, which hinders vaporization and atomization of the fuel. These problems have led to an increase in the amount of unburned components emitted, which has led to a decrease in output, fuel economy, or emission.
[0005]
Further, in the above-described conventional technology, a gas injection valve for forming an air curtain is separately required, and there is a problem in cost.
[0006]
The present invention has been made in view of the above circumstances, and does not require special members, and at the time of high-speed operation of an engine, forms an appropriate air-fuel mixture without adhesion of injected fuel to a wall surface of a combustion chamber. Another object of the present invention is to provide a spark-ignition direct injection engine that can promote stratification of fuel and increase combustion efficiency during low-speed operation of the engine.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a spark plug disposed at a substantially central portion of a ceiling portion of a combustion chamber, a pair of intake ports opening into the combustion chamber on one half side of the ceiling portion of the combustion chamber, and a spark plug. An injector disposed on the peripheral side of the combustion chamber between the two intake port openings with the injection port opened toward the intake port, wherein the injector directly injects fuel toward the spark plug. At
In the two intake ports, the main flow of the intake air flowing into the combustion chamber from the intake port flows in a direction away from a plane including the injector and the axis of the combustion chamber, and is biased toward the periphery of the combustion chamber. And a spark ignition type direct injection engine.
[0008]
According to the present invention, the main flow of the intake air flowing from the two intake ports flows in a direction away from a plane including the injector and the axis of the combustion chamber, and is biased toward the periphery of the combustion chamber. I have. Therefore, the main intake air flow formed at the time of the intake stroke flows into the combustion chamber with a small amount of the component that pushes out the fuel injected during the intake stroke by the injector during the high-speed operation of the engine (hereinafter the flow at the time of the inflow is referred to as the forward flow). Shown). That is, the forward flow flows into the combustion chamber without flowing the injected fuel to the combustion chamber wall surface, and the flow of the intake air in the combustion chamber is promoted by the main flow of the intake air.
[0009]
Further, each forward flow formed during the intake stroke of the engine is directed downward (toward the piston) along the combustion chamber wall surface opposite to both intake ports, and is further circulated to both intake ports along the upper surface of the piston. (Hereinafter, this diverted flow is referred to as a return flow). In this case, the pair of main intake air flows from the two intake ports is such that each of the outgoing flows is spread toward the periphery of the combustion chamber in plan view, and is directed downward along the periphery toward the wall surface facing the intake ports. On the other hand, the flow returns near the wall while balancing each other. The main intake air flow (hereinafter, referred to as a hyperbolic flow) including the return flow and the forward flow remains until the compression stroke of the engine. In the compression stroke, the combustion chamber is compressed with the rise of the piston, so that a pair of backward flows colliding near the wall surfaces facing both the intake ports are pushed up to the spark plug side without going. Due to the rise of the return flow, for example, during low-speed operation of the engine, the fuel injected during the compression stroke flows to the combustion chamber wall surface facing the intake port, and is pushed up to the spark plug side without diffusion.
[0010]
Therefore, the spark ignition type direct injection engine of the present invention does not require special members, forms an appropriate air-fuel mixture during high-speed operation of the engine, and promotes stratification of fuel during low-speed operation of the engine. Combustion efficiency can be increased.
[0011]
In the spark ignition type direct injection engine of the present invention, the injector radially injects fuel from the injection port toward the spark plug, and the width of the fuel spray in the vicinity of the spark plug in a plan view is equal to the center of both intake port openings. It is preferable that the radiation angle is set so as to be smaller than the distance.
[0012]
With this configuration, the forward flow of the hyperbolic flow formed during the intake stroke is more reliably prevented from flowing into the combustion chamber wall surface of the injected fuel, and flows into the combustion chamber. Therefore, the spark ignition type direct injection engine of the present embodiment can form a more appropriate air-fuel mixture.
[0013]
One aspect of the configuration of the intake ports in the present invention is that the downstream sides of both the suction ports are curved so as to open in a direction along the periphery of the combustion chamber away from a plane including the injector and the axis of the combustion chamber. Is what it is.
[0014]
According to this aspect, the downstream sides of both the intake ports are curved so as to open in the direction along the periphery of the combustion chamber away from the plane including the injector and the axis of the combustion chamber. Therefore, the main flow of the intake air passing through both intake ports flows in the direction. Therefore, it is possible to more efficiently form a proper air-fuel mixture, and to promote stratification of the fuel to increase the combustion efficiency.
[0015]
In this embodiment, since the openings of both intake ports are separated from each other, the space between both intake ports is expanded. This space is effectively used, for example, as a space for providing a cooling water passage for the injector.
[0016]
According to another aspect of the intake port, in the spark ignition type direct injection engine according to claim 1, the cross-sectional shape of each of the intake ports orthogonal to the intake direction is a substantially rectangular long passage, and one side direction of the long passage. And the main flow of intake air passing through each of these triangular passages is more deviated from a plane including the injector and the axis of the combustion chamber than the main flow of intake air passing through each of the rectangular passages. And a shutter valve provided on the upstream side of both intake ports so as to open and close the long passage.
[0017]
According to this aspect, the main flow of the intake air passing through the triangular passages of the two intake ports is located farther away from the plane including the injector and the axis of the combustion chamber than the main flow of the intake air passing through the long passages. During high-speed operation of the engine, the main flow of the intake air passing through the triangular passages and the rectangular passages is deflected in the direction and flows in. In addition, a shutter valve that can open and close the long passages of both intake ports is provided, so when the engine is running at low speed, the shutter valve is closed and the intake passage is narrowed to enhance the flow rate of intake air, and the triangular passage is opened. The passing intake air is deflected in the above direction and flows in.
[0018]
Therefore, at the time of high-speed operation of the engine, an appropriate air-fuel mixture is formed, and especially at the time of low-speed operation of the engine, stratification of fuel can be further promoted and combustion efficiency can be increased by strengthening the hyperbolic flow by the shutter valve.
[0019]
Further, in the spark ignition type direct injection engine of the present invention, a guide wall for guiding an air flow is provided at a peripheral portion of the combustion chamber at a portion facing the injector, and the guide wall allows the air to flow from both intake ports. Preferably, the main flow of the intake air is diverted in a non-intersecting direction to a plane including the axis of the injector and the axis of the combustion chamber, respectively.
[0020]
According to this aspect, the main flow of each intake air that has flowed in from both intake ports is circulated in a non-intersecting direction to a plane including the axis of the injector and the combustion chamber by the guide wall. In the hyperbolic flow circulating in this way, interference between the respective swirling motions is suppressed. Therefore, the hyperbolic flow remaining until the compression stroke becomes stronger, so that stratification during the compression stroke can be further promoted.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 1 is a cross-sectional view of a spark ignition direct injection engine 1 according to an embodiment of the present invention, with a part thereof omitted.
[0023]
With reference to FIG. 1, a spark ignition type direct injection engine 1 includes a cylinder block 2. The cylinder block 2 includes a cylindrical housing 4 into which a piston 3 is slidably fitted. The piston 3 is fitted into one end of the cylindrical housing 4, and the other end is closed by a cylinder head 5. At a position corresponding to the cylindrical housing portion 4 in the cylinder head 5, a pent roof-shaped concave portion 6 is provided. The following description will be made on the assumption that the concave portion 6 side of the cylinder block 2 is assumed to be upward.
[0024]
FIG. 2 is a partially schematic plan view schematically showing a spark ignition type direct injection engine 1 according to the first embodiment of the present invention.
[0025]
Referring to FIGS. 1 and 2, a combustion chamber 7 is formed between the recess 6 and the upper surface of the piston 3. That is, the combustion chamber 7 is a space including the upper end portion of the cylindrical housing portion 4 and the concave portion 6. A spark plug 8 is provided at the top of the concave portion 6 so as to face the combustion chamber. An injector 9 is provided on the periphery of the concave portion 6 with the injection port 9a opened to the ignition plug 8. The injector 9 directly and radially injects fuel into the ignition plug 8.
[0026]
The cylinder head 5 is provided with a pair of intake ports 10 whose downstream ends open to the combustion chamber 7. The downstream end openings of these intake ports 10 are arranged on one half side of the recess 6, and the injector 9 is arranged on the peripheral side of the combustion chamber between the openings of both intake ports 10. Each of the intake ports 10 is provided with an intake valve 10a that can open and close the intake port 10. Further, the upstream ends of the intake ports 10 are deflected toward the injector 9 in a plan view (FIG. 2). That is, in a plan view, both intake ports 10 are deflected in a direction away from a plane including the injector 9 and the axis of the combustion chamber 7 (hereinafter referred to as a plane D) as going from the upstream side to the downstream side. The flow center (ie, main flow) of the intake air flowing from the intake ports 10 deflected in this manner is separated from the plane D as shown in FIG. It faces to the wall surface of the combustion chamber 7 facing both the intake ports 10.
[0027]
A mask 11 as a guide wall is provided on a wall surface of the combustion chamber 7 facing the intake ports 10. The mask 11 is provided corresponding to the intake air flowing from both intake ports 10, and a pair of circulating surfaces 11 a for guiding the flow center of the intake air from the periphery of the combustion chamber 7 to the plane D in a non-intersecting direction. It has. These circulating surfaces 11a are circular arcs that extend from the cylindrical surface of the cylindrical housing portion 4 to the plane D in the plan view and also to the spark plug 8 side, and are continuous along the vertical direction. Further, in plan view, the diverting surfaces 11a are arranged at predetermined intervals so that the flow center of each intake air after circulating does not interfere with the plane D.
[0028]
Further, a pair of exhaust ports 12 is provided on a wall surface of the combustion chamber 7 facing the intake ports 10. Each of the exhaust ports 12 is provided with an exhaust valve 12a that can open and close the exhaust port 12.
[0029]
By the way, in a plan view, the injector 9 is configured such that the width of the fuel spray by the injection port 9a near the ignition plug 8 is smaller than the distance between the centers of the openings of the intake ports 10 to the fuel chamber 7. The injection angle 9a is set.
[0030]
In the spark-ignition direct injection engine 1 configured as described above, the intake air flowing from the intake ports 10 is separated from the plane D and biased toward the peripheral edge of the fuel chamber 7 to the forward flow T1 and flows to the mask 11. A hyperbolic flow T which is circulated by the mask 11 and swirls with the return flow T2 flowing toward the two intake ports 10 via the lower portion of the ignition plug 8 is formed.
[0031]
Referring to FIG. 1, for example, during high-speed operation of the engine, an outgoing flow T1 of a hyperbolic flow T (indicated by a two-dot chain line arrow in FIG. 1) is generated near a spark plug 8 of fuel injected during an intake stroke. The spray area S reaches the mask 11 almost without being washed away. Each forward flow T1 is circulated by the mask 11 and becomes a return flow T2 passing below the injection range S. That is, the forward flow T1 flows into the fuel chamber 7 almost without flowing the fuel injected during the intake stroke, and the forward flow T1 and the backward flow T2 promote the flow in the combustion chamber.
[0032]
On the other hand, for example, at the time of low-speed operation of the engine, even when the intake valve 10a and the exhaust valve 12a close the intake port 10 and the exhaust valve 12, the hyperbolic flow T remains in the combustion chamber 7. Then, when the piston 3 moves up to a so-called compression stroke, the swirling range of the hyperbolic flow T is compressed (in FIG. 1, indicated by a solid arrow). In other words, the backward flow T2 of the hyperbolic flow T loses a downward destination in the combustion chamber 7, and is pushed upward in the combustion chamber 7. Due to the rise of the backward flow T2, the fuel injected during the compression stroke advances to the wall surface side of the combustion chamber 7 facing the intake port 10 and is pushed upward above the combustion chamber 7 without diffusing.
[0033]
As described above, the spark ignition type direct injection engine 1 is curved such that both intake ports 10 are separated from the plane D and open in the direction along the periphery of the combustion chamber 7. Therefore, at the time of high-speed operation of the engine, the forward flow T1 of the hyperbolic flow T hardly flushes the fuel injected during the intake stroke, and the flow in the combustion chamber 7 can be promoted by the forward flow T1 and the backward flow T2. it can. On the other hand, the backward flow T2 of the hyperbolic flow T is pushed up to the spark plug 8 side by the compression stroke of the engine. Due to this return flow T2, it is possible to suppress the diffusion of the fuel injected during the compression stroke during the low-speed operation of the engine.
[0034]
Further, since the mask 11 is provided on the wall surface of the combustion chamber 7 facing the intake ports 10, the flow center of each forward flow T1 flowing from the intake ports 10 is directed in a direction not intersecting with the plane D. Diverted towards. The hyperbolic flow T circulated in this manner makes a circling motion in a state where interference is suppressed, and remains with a stronger circling motion until the compression stroke. Therefore, stratification during the compression stroke can be promoted.
[0035]
In addition, the configuration of the intake port that allows the flow center of the intake air to flow in a direction away from the plane D and to be biased toward the periphery of the combustion chamber 7 is not limited to the above-described embodiment, but is as follows. It can also be set as a structure.
[0036]
FIG. 3 is a partially schematic plan view showing a spark ignition type direct injection engine 20 according to a second embodiment of the present invention.
[0037]
Referring to FIG. 3, spark-ignition direct injection engine 20 includes the same configuration as spark-ignition direct injection engine 1 described above. Only differences from the engine 1 will be described. The cylinder head 5 of the spark ignition type direct injection engine 20 is provided with a pair of intake ports 21 whose downstream ends open to the combustion chamber 7. The downstream end openings of these intake ports 21 are arranged on one half side of the recess 6, and the injector 9 is arranged on the periphery of the combustion chamber between the openings of both intake ports 10. These intake ports 21 are arranged substantially linearly from the downstream end to the upstream side in plan view. Each of the intake ports 21 has a tapered shape whose cross-sectional area orthogonal to the intake direction is increased in the direction away from the plane D as going upstream. Therefore, the flow center of the intake air flowing from the upstream side of the intake ports 21 flows into the fuel chamber 7 along the flow center P1 which is farther from the plane D than the center line C of the intake ports 21 at the opening. You. As described above, the flow center of the intake air flowing into the fuel chamber 7 flows in a direction away from the plane D and is biased toward the peripheral edge of the combustion chamber 7. The same effect as that of the spark ignition type direct injection engine 1 can be obtained.
[0038]
Furthermore, the configuration of the intake port that allows the flow center of the intake air to flow in a direction away from the plane D and to be biased toward the peripheral edge of the combustion chamber 7 may be as follows.
[0039]
4A and 4B are imaginary sectional views orthogonal to the intake directions of both intake ports 31 in the spark ignition type direct injection engine 30 according to the third embodiment of the present invention, wherein FIG. 4A shows a closed state of the shutter valve 32, and FIG. () Shows the open state of the shutter valve 32, respectively.
[0040]
Referring to FIG. 4 (a), both intake ports 31 each include a substantially rectangular long passage 31a located above. The rectangular passage 31a has its short side arranged along the vertical direction. The lower end of each of the rectangular passages 31a is connected to a substantially triangular passage 31b. Each of these triangular passages 31b is narrowed downward from the rectangular passage 31a and away from the plane D. Therefore, the flow center P2 of the intake air passing through each of the triangular passages 31b is positioned farther from the plane D than the flow center P3 of the intake air passing through the rectangular passage 31a.
[0041]
Incidentally, each of the intake ports 31 is provided with a shutter valve 32 capable of adjusting the flow rate of the intake air passing through the intake ports 31. For example, when the engine is running at a low speed, the shutter valve 32 narrows the intake passage (improves the intake speed) to promote the flow of the intake air in the combustion chamber. The purpose is to improve the fuel efficiency of the engine by improving pumping loss and thermal efficiency. Each of the shutter valves 32 includes a shutter shaft 32a arranged in a direction normal to the plane D. The middle part of the shutter shaft 32a faces each of the rectangular passages 31a. A shutter plate 32b is provided on the shutter shaft 32a in each of the rectangular passages 31a so as to be rotatable around the shutter shaft 32a. These shutter plates 32b have substantially the same external dimensions as the rectangular passage 31a. That is, the rectangular passage 31a can be opened and closed by rotating the shutter plate 32b around the shutter shaft 32a.
[0042]
For example, at the time of high-speed operation of the engine, the rectangular passage 31a is closed by the shutter valve 32. In this state, since the intake air passes only through the triangular passage 31b, the flow center of the intake air flows into the combustion chamber 7 along the flow center P2.
[0043]
Referring to FIG. 4B, when the engine is running at a low speed, each shutter valve 32 opens the rectangular circuit 31a. In this state, since the intake air passes through both the rectangular passages 31a and the triangular passages 31b, the flow center of each intake air is separated from the flow center P4 of the rectangular passage 31a by the flow center P4 separated from the plane D. Along the combustion chamber 7.
[0044]
In the spark ignition type direct injection engine 30 configured as described above, the flow center P2 of the triangular passage 31b is located away from the plane D. Therefore, at the time of high-speed operation of the engine, the flow center of the intake air passing through each of the triangular passages 31b and the rectangular passage 31a flows into the combustion chamber 7 along the flow center P4. On the other hand, at the time of low-speed operation of the engine, the flow center of the intake air passing through each triangular passage 31b flows into the combustion chamber 7 along the flow center P2.
[0045]
Therefore, the spark ignition type direct injection engine 30 can flow the flow center of the intake air passing through both intake ports 31 in a direction away from the plane D and in a direction toward the periphery of the combustion chamber 7. The same effect as that of the direct injection engine 1 can be obtained. In particular, since the spark ignition type direct injection engine 30 is provided with the shutter valve 32, when the engine is running at a low speed, the hyperbolic flow T is enhanced by improving the intake air speed, thereby further promoting fuel stratification and increasing combustion efficiency. be able to.
[0046]
The mask 11 is not limited to being arranged on the wall surface of the combustion chamber 7 facing the intake ports 10, but is arranged on the wall surface of the combustion chamber 7 on the side where both intake ports 10 are arranged, so that the hyperbolic flow T The return flow T2 may be circulated to the forward flow T1. Further, the triangular passage 31b is not limited to being disposed below the rectangular passage 31a, but may be disposed above the rectangular passage 31a or on a side away from the plane D. .
[0047]
【The invention's effect】
As described above, in the present invention, the main flow of the intake air flows in a direction away from the plane including the injector and the axis of the combustion chamber and is biased toward the periphery of the combustion chamber. Therefore, the flow in the combustion chamber can be promoted without flowing the injected fuel to the wall surface of the combustion chamber.
[0048]
On the other hand, the hyperbolic flow formed in the intake stroke remains until the compression stroke, and the return flow is pushed up to the spark plug side during the compression stroke, so that the fuel injected in the compression stroke during the low-speed operation of the engine is injected into the combustion chamber wall. Progress and diffusion can be suppressed.
[0049]
Therefore, the spark ignition type direct injection engine of the present invention does not require special members, forms an appropriate air-fuel mixture during high-speed operation of the engine, and promotes stratification of fuel during low-speed operation of the engine. Combustion efficiency can be increased.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a spark ignition type direct injection engine according to an embodiment of the present invention, with a part thereof omitted.
FIG. 2 is a partially schematic plan view schematically showing a spark ignition type direct injection engine according to the first embodiment of the present invention.
FIG. 3 is a partially schematic plan view showing a spark ignition type direct injection engine according to a second embodiment of the present invention.
FIGS. 4A and 4B are virtual sectional views orthogonal to the intake directions of both intake ports in a spark ignition type direct injection engine according to a third embodiment of the present invention, wherein FIG. 4A is a closed state of a shutter valve, and FIG. The open state of each valve is shown.
[Explanation of symbols]
1, 20, 30 Spark ignition type direct injection engine 4 Cylindrical housing 6 Recess 7 Combustion chamber 8 Spark plug 9 Injector 9a Injection port 10, 21, 31 Intake port 11 Mask 11a Recirculation surface 31a Rectangular passage 31b Triangular passage 32 Shutter valve

Claims (5)

A spark plug arranged substantially at the center of the ceiling portion of the combustion chamber, a pair of intake ports opening into the combustion chamber on one half side of the ceiling portion of the combustion chamber, and a pair of intake ports opening the injection port toward the ignition plug. An injector disposed on the peripheral side of the combustion chamber between the intake port openings, wherein the injector directly injects fuel toward the spark plug,
In the two intake ports, the main flow of the intake air flowing into the combustion chamber from the intake port flows in a direction away from a plane including the injector and the axis of the combustion chamber, and flows in a direction toward the periphery of the combustion chamber. A spark-ignition direct-injection engine, characterized in that it is formed as follows. 2. The spark-ignition direct-injection engine according to claim 1, wherein the injector radially injects fuel from the injection port toward the spark plug, and the width of the fuel spray in the vicinity of the spark plug in a plan view is equal to the width of the two intake ports. A spark-ignition direct injection engine, wherein the radiation angle is set so as to be smaller than the distance of the center of the opening. In the spark ignition type direct injection engine according to claim 1, the downstream sides of both suction ports are curved so as to open in a direction along the periphery of the combustion chamber away from a plane including the injector and the axis of the combustion chamber. A spark-ignition direct-injection engine. 2. A spark-ignition direct injection engine according to claim 1, wherein the cross-sections of the two intake ports orthogonal to the intake direction are substantially rectangular elongated passages and substantially triangular triangular passages narrowed in one side direction of the elongated passages. The main flow of the intake air passing through each of these triangular passages is located further away from the plane including the injector and the axis of the combustion chamber than the main flow of the intake air passing through the respective rectangular passages, and A spark-ignition direct injection engine, comprising a shutter valve provided on an upstream side of the port so as to open and close the long passage. In the spark ignition type direct injection engine according to claim 1, a guide wall for guiding an air flow is provided at a peripheral portion of the combustion chamber at a portion facing the injector, and the guide wall allows the intake air flowing from both intake ports. Is circulated in a non-intersecting direction to a plane including the axis of the injector and the axis of the combustion chamber, respectively.

Images