JP4042483B2 - Direct-injection spark ignition engine - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a direct-injection spark ignition engine, and more particularly, to a technique for favorably forming a stratified mixture by a guide wall provided on an inner wall surface of a cylinder head between an injector and a spark plug.
[0002]
[Prior art]
In a direct-injection spark ignition engine, providing a guide wall on the inner wall surface of the cylinder head between the intake port and the spark plug insertion hole is described in JP-A-10-252477. In this publication, a mask wall having a rectangular cross section is provided as the guide wall, and the reverse tumble flow is relatively strengthened by preventing the flow from the intake port toward the center of the combustion chamber by this mask wall during stratified combustion, and the spark plug A technique for concentrating fuel in the vicinity is described.
[0003]
[Problems to be solved by the invention]
However, the conventional technique has the following problems. First, the technique is applied to form a reverse tumble flow of the intake air in the cylinder (a flow from the intake port toward the spark plug after passing through the vicinity of the cylinder side wall). Second, even if the mask wall is provided in a direct injection spark ignition engine in which a forward tumble flow (a flow from the intake port through the center of the combustion chamber and then toward the ignition plug) is formed, the mask wall As a result, the gas flow is stopped just before the spark plug, and the fuel cannot be transported well to the ignition position.
[0004]
Accordingly, the present invention provides a guide wall provided on the inner wall surface of the cylinder head that can be adapted to a direct-injection spark ignition engine in which a forward tumble flow is formed. Thus, an object is to form a good air-fuel mixture in the vicinity of the spark plug.
[0005]
[Means for Solving the Problems]
Therefore, in the first aspect of the invention, in the direct injection spark ignition engine in which the stratified mixture is formed by the forward tumble flow of the intake air, the injector is reversed on the crown surface of the piston of the forward tumble flow. while disposed upstream relative to the flow of air toward the spark plug after, the guide walls provided on the cylinder head inner wall surface between the insertion holes of the injector and the ignition plug, the flow of air toward the front Symbol point fire plugs the opposing surface for, can smoothly continue from the inner wall surface the cylinder head is parallel to the cylinder center axis, and in section along the plane parallel to the direction of flow of the air toward the ignition plug, be shaped as arcuate It was.
[0006]
In the invention according to claim 2 , a depression is provided on the facing surface.
In the invention according to claim 3 , the facing surface is semi-elliptical or V-shaped in a cross section by a plane orthogonal to the cylinder central axis.
[0007]
In the invention according to claim 4 , in the cross section by the plane orthogonal to the cylinder central axis, both the semi-elliptical or V-shaped blades are expanded in an arc shape.
According to a fifth and sixth aspect of the invention, in the cross section of the plane parallel to the cylinder central axis and orthogonal to the direction of the air flow toward the spark plug, both sides of the facing surface are arcuate. did.
[0008]
In the invention according to claim 7, the guide wall is provided on the inner wall surface of the cylinder head between the intake port and the spark plug insertion hole.
[0009]
【The invention's effect】
According to the first aspect of the present invention, in the guide wall, the surface facing the air flow toward the spark plug of the forward tumble flow is formed into a shape that smoothly continues from the inner wall surface of the cylinder head. The fuel to be transported can be diffused by this facing surface and stay in the vicinity of the spark plug. For this reason, a stratified mixture can be satisfactorily formed regardless of variations and changes in various conditions.
[0010]
Further , the opposed surface is formed in an arc shape in a cross section by a plane parallel to the cylinder central axis and parallel to the direction of the air flow toward the spark plug, so that fuel can be diffused and retained satisfactorily.
According to the second aspect of the present invention, the fuel can be diffused by the facing surface of the guide wall and can be retained in the vicinity of the spark plug, and the fuel can be reliably captured by the recess provided on the facing surface and diffused appropriately. Can do.
[0011]
According to the third aspect of the present invention, the opposed surface is semi-elliptical or V-shaped in a cross section orthogonal to the cylinder central axis, so that the fuel can be diffused satisfactorily without stagnating the air flow. .
According to the invention which concerns on Claim 4 , the said semi-ellipse or V-shaped both wing | blade part was spread in circular arc shape, a fuel can be spread | diffused strongly and it can be made to retain in a favorable state by the vicinity of a spark plug.
[0012]
According to the fifth aspect of the present invention, the opposing surface has a cross-section with a plane parallel to the cylinder central axis and perpendicular to the direction of air flow toward the spark plug, and both sides of the opposing surface are arcuate. As a result, the air can smoothly flow along the guide wall, and the fuel can be prevented from adhering to the guide wall.
According to the sixth aspect of the present invention, the fuel can be diffused by the facing surface of the guide wall and can stay in the vicinity of the spark plug, and the air can be smoothly flowed along the facing surface to prevent the fuel from adhering to the guide wall. Can be prevented.
According to the seventh aspect of the present invention, the guide wall is provided on the inner wall surface of the cylinder head between the intake port and the spark plug insertion hole, so that the fuel can be diffused and retained satisfactorily and a forward tumble flow is formed. When the air to flow flows into the cylinder, the guide wall does not hinder and can smoothly flow in.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of an automobile engine (hereinafter referred to as “engine”) 1 as a direct injection spark ignition engine according to an embodiment of the present invention, and shows a configuration of a combustion chamber C of the engine 1.
[0014]
A piston 3 is inserted into the cylinder block 2 of the engine 1, and a concave recess (hereinafter referred to as “bowl portion”) 31 is formed on the piston 3. A cylinder head 4 having a pent roof type inner wall surface 41 is fixed on the cylinder block 2, and two intake ports 42 and two exhaust ports 43 are formed on the cylinder head 4 side by side in the cylinder arrangement direction. Yes. Here, an intake valve 5 is interposed in the intake port 42, and an exhaust valve 6 is interposed in the exhaust port 43. Further, the cylinder head 4 is formed with a hole 44 extending vertically through the cylinder head 4 on the cylinder center axis Aa, and the spark plug 7 is inserted into the hole 44 (hereinafter referred to as “ignition plug insertion hole”). Is fixed. The spark plug 7 faces the upper center of the combustion chamber C formed between the piston crown surface and the cylinder head inner wall surface 41. The cylinder head 4 is fixed with a high-pressure injector 8 as fuel injection means. The injector 8 is inserted between two intake ports 42 and 42 into a hole 45 that penetrates the cylinder head side wall obliquely downward from the outside (hereinafter referred to as “injector insertion hole”). It faces the side of the combustion chamber C. Here, the guide wall 9 according to the present embodiment is provided between the opening ends of the injector insertion hole 45 and the spark plug insertion hole 44 on the inner wall surface of the cylinder head.
[0015]
FIG. 2 is an arrangement view of the injector 8, the guide wall 9, and the spark plug 7 when the cylinder head 4 of the engine 1 is viewed from below.
Thus, the guide wall 9 is provided on the inner wall surface of the cylinder head between the intake ports 42 and 42 and the spark plug insertion hole 44 (the spark plug 7) between the injector 8 and the spark plug 7. . That is, the guide wall 9 is substantially V-shaped when the cylinder head 4 is viewed from below when the engine is mounted (the shape will be described later). Each V-shaped wing extends from the space between the two intake ports 42, 42 onto the cylinder head inner wall surface 41 between the intake ports 42, 42 and the spark plug insertion hole 44, and the cylinder central axis. It terminates in a plane parallel to the cylinder arrangement direction including Aa and surrounds the half of the spark plug 7 on the injector 8 side. Here, the position of the guide wall 9 with respect to the spark plug 7 should be set in order to satisfactorily realize the diffusion and retention of fuel, which will be described later, but the inflow of air into the cylinder is not hindered. The spark plug insertion hole 44 is disposed as close as possible.
[0016]
FIG. 3 is a perspective view of the inner wall surface 41 of the cylinder head and shows an overview of the guide wall 9 according to the present embodiment.
FIG. 4 is a partially enlarged view of the cylinder head inner wall surface 41 showing the shape of the guide wall 9 in detail.
The structure of the guide wall 9 will be described specifically with reference mainly to FIG. Here, the center axis of the cylinder is again indicated by Aa, and an axis that is orthogonal to the cylinder center axis Aa and that is parallel to the cylinder arrangement direction (hereinafter referred to as “lateral axis”) is Ab, the cylinder center axis Aa, and the lateral direction. An axis orthogonal to any of the axes Ab (hereinafter referred to as “longitudinal axis”) is denoted by Ac. On the longitudinal axis Ac, the injector 8 side is defined as the front and the opposite side is defined as the rear with respect to the cylinder center axis Aa. As is apparent from FIGS. 3 and 4, the front-rear direction corresponds to the direction of the flow of air that forms a forward tumble flow toward the spark plug 7.
[0017]
In the present embodiment, the surface 91 of the guide wall 9 (corresponding to the “opposing surface”) 91 is substantially V-shaped when viewed along the cylinder center axis Aa from below the cylinder head 4, that is, from above in FIG. As described above, it is located between the two intake ports 42 and 42 and the spark plug insertion hole 44.
Here, the facing surface 91 has a substantially arc shape in a first cross section including the cylinder central axis Aa and the longitudinal axis Ac, and in this first cross section, continues smoothly from the inner wall surface 41 of the cylinder head. As the plug 7 is approached, the inclination with respect to the cylinder head inner wall surface 41 increases. In the second cross section perpendicular to the cylinder center axis Aa, the V-shaped facing surface 91 draws a streamlined and smooth curve from the front, and its wings 911a and 911b spread in an arc shape. (Fig. 2). In the present embodiment, the lateral width w of the guide wall 9 is set equal to the distance D between the inner ends of the intake ports 42 and 42, and the height h is set equal to the electrode position height of the spark plug 7. .
[0018]
5 is a cross-sectional view taken along line bb of FIG. In the present embodiment, the opposing surface 91 has an arc shape in this cross section (FIG. 5A). In addition to this, for example, as shown in FIG. It is also possible to extend it with a gentle inclination with respect to 41 and to curve it so as to follow the cylinder center axis Aa immediately before the spark plug 7 so as to form a dent on the entire facing surface 91. Moreover, although it is circular as a whole like the figure (c), you may form the hollow 912 in a part.
[0019]
6 is a cross-sectional view taken along the line cc of FIG. The wing portions 911a and 911b of the facing surface 91 are arc-shaped in this cross section, and increase in inclination with respect to the cylinder center axis Aa as they approach the cylinder head inner wall surface 41 downward from the upper end, that is, expand to the left and right.
FIG. 7 is an explanatory diagram of the air-fuel mixture formation in the engine 1 including the guide wall 9 described above.
[0020]
The engine 1 is provided with an engine controller (not shown) as control means, and this engine controller has a function of switching the combustion method between stratified combustion and homogeneous combustion in accordance with the operating state of the engine 1. is doing. In stratified combustion, the injector 8 injects fuel during the compression stroke based on a command from the engine controller. On the other hand, in homogeneous combustion, the injector 8 injects fuel during the intake stroke based on a command from the engine controller. The case of stratified combustion will be described below.
[0021]
During stratified combustion, in the intake stroke, as shown in FIG. 7A, air flows into the cylinder from the intake port 42 (arrow f1). At this time, the opposing surface 91 of the guide wall 9 has a shape that continues smoothly from the inner wall surface 41 of the cylinder head, and the height of the guide wall 9 in the vicinity of the intake port 42 is kept low, so that the inflow of air is hindered. There is nothing. Therefore, air flows with sufficient strength from the intake port 42 toward the center of the combustion chamber.
[0022]
In the compression step, as shown in FIG. 7B, the air flow is reversed by the bowl portion 31 of the piston 3 and fuel is injected from the injector 8. The injected fuel M is transported toward the spark plug 7 by the forward tumble flow (arrows f2 and f3) of the air thus formed. Then, as shown in FIG. 3C, the fuel M collides with the facing surface 91 of the guide wall 9 and is diffused (arrow f4) and stays in the vicinity of the spark plug 7.
[0023]
As described above, in this embodiment, in the guide wall 9 provided between the injector 8 and the spark plug 7, first, the facing surface 91 for the flow f3 of the forward tumble flow f2 and f3 toward the spark plug 7 is provided. The shape continued smoothly from the inner wall surface 41 of the cylinder head. For this reason, the fuel M injected from the injector 8 can be diffused by the facing surface 91 and can be retained in a good state in the vicinity of the spark plug 7. In a direct injection engine such as the engine 1, because of in-cylinder pressure, gas flow strength (tumble flow strength), fuel injection pressure, fuel injection amount, and injector injection port structure variations, there is always a constant spray form during stratified combustion. Not necessarily obtained, a good stratified mixture is not formed, combustion becomes unstable, and the fuel M adheres to the spark plug 7 to cause misfire and smoldering. In the engine 1 according to the present embodiment, the provision of the guide wall 9 reduces the influence of fluctuation factors such as the in-cylinder pressure, and a stable stratified mixture can be stably formed. Moreover, since the fuel M does not adhere directly to the spark plug 7, the occurrence of misfire or the like can be prevented.
[0024]
Secondly, the opposing surface 91 has an arc shape in a first cross section by a plane including the cylinder center axis Aa and the longitudinal axis Ac, and is substantially V-shaped when viewed from above in FIG. The V-shaped wing portions 911a and 911b are expanded in an arc shape in a second cross section orthogonal to the V. For this reason, the fuel M can be diffused in the lateral direction by the guide wall 9 and can be diffused strongly as a whole.
[0025]
Third, as shown in FIGS. 4 and 6, the wing portions 911 a and 911 b of the facing surface 91 are formed in a circular arc shape in the vertical direction and smoothly connected to the cylinder head inner wall surface 41 in the left-right direction. For this reason, it is possible to prevent the fuel M from diffusing and to smoothly pass through the guide wall 9 and adhere to the guide wall 9.
As shown in FIG. 5, by forming the recess 912 on the facing surface 91, the fuel M can be reliably captured by the recess 912, diffused appropriately, and retained in the vicinity of the spark plug 7. Is obtained. Even in the guide wall 9 with such a depression, the facing surface 91 may be smoothly connected to the cylinder inner wall surface 41 in the left-right direction.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an automobile engine as a direct-injection spark ignition engine according to an embodiment of the present invention. FIG. 2 is a layout diagram of an injector, a guide wall, and a spark plug in the engine. Overview of the inner wall of the head [FIG. 4] Partial enlarged view of the inner wall of the cylinder head. [FIG. 5] BB sectional view of FIG. 4 [FIG. 6] cc sectional view of FIG. Operation explanatory diagram of automobile engine according to the embodiment [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Automotive engine as a direct-injection spark ignition engine, 2 ... Cylinder block, 3 ... Piston, 4 ... Cylinder head, 41 ... Cylinder head inner wall surface, 42 ... Intake port, 43 ... Exhaust port, 44 ... Spark plug insertion hole 45 ... injector insertion hole, 7 ... spark plug, 8 ... injector, 9 ... guide wall, 91 ... facing surface, 912 ... depression, 911a, 911b ... wing on the facing surface, Aa ... cylinder central axis, C ... combustion chamber M ... fuel.

Claims (7)

A direct-injection spark ignition engine in which a stratified mixture is formed by a forward tumble flow of intake air,
Spark plugs,
An injector disposed upstream of the forward tumble flow with respect to the air flow toward the spark plug after reversing on the crown of the piston;
The provided injectors and on the cylinder head inner wall surface between the insertion hole of the spark plug, comprising: a guide wall projecting from the inner wall surface of the cylinder head into the combustion chamber, and
The guide wall is opposed surfaces to the flow of air toward the front Symbol point fire plugs, can smoothly continue from the inner wall surface the cylinder head is parallel to the cylinder center axis, and the direction of flow of the air toward the spark plug A direct-injection spark-ignition engine characterized by being arc-shaped in a cross section by a parallel plane . A direct-injection spark ignition engine in which a stratified mixture is formed by a forward tumble flow of intake air,
Spark plugs,
An injector disposed upstream of the forward tumble flow with respect to the air flow toward the spark plug after reversing on the crown of the piston;
A guide wall provided on the inner wall surface of the cylinder head between the insertion holes of the injector and the spark plug, and protruding from the inner wall surface of the cylinder head into the combustion chamber,
The direct injection spark ignition engine characterized in that the guide wall has a surface facing the air flow toward the spark plug that continues smoothly from the inner wall surface of the cylinder head and has a recess in the surface. The direct-injection spark ignition engine according to claim 1 or 2 , wherein the facing surface is a semi-elliptical or V-shaped cross section by a plane orthogonal to the cylinder central axis. The direct-injection spark-ignition engine according to claim 3 , wherein both the semi-elliptical or V-shaped wing parts are expanded in an arc shape. The facing surface is parallel to the cylinder center axis, and in a section along the plane orthogonal to the direction of flow of the air toward the ignition plug, according to claim 1-4 both sides is arcuate Direct-injection spark ignition engine. A direct-injection spark ignition engine in which a stratified mixture is formed by a forward tumble flow of intake air,
Spark plugs,
An injector disposed upstream of the forward tumble flow with respect to the air flow toward the spark plug after reversing on the crown of the piston;
A guide wall provided on the inner wall surface of the cylinder head between the insertion holes of the injector and the spark plug, and protruding from the inner wall surface of the cylinder head into the combustion chamber,
The guide wall has a plane facing the air flow toward the spark plug smoothly extending from the inner wall surface of the cylinder head , parallel to the cylinder central axis, and perpendicular to the direction of the air flow toward the spark plug. A direct-injection spark-ignition engine characterized by having a cross-section according to and having arcs on both sides.   The direct injection spark ignition engine according to any one of claims 1 to 6, wherein the guide wall is provided on an inner wall surface of the cylinder head between the intake port and the spark plug insertion hole.

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