JPH09317479A - Cylinder injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stratify fuel and improve the combustion performance of a cylinder injection engine in its lean-burn range by forming a guide groove in the top face of a piston, which extends from the intake side toward the piston center at the substantial same angle as the injection angle providing a projected body on the wall surface of the cylinder head constituting the combustion chamber, which prevents fuel from directly reaching the ignition plug. SOLUTION: In the compression stroke in a part load, fuel injected from a fuel injection valve 34 is directed to a spherical surface 44 of a guide groove 46 which is positioned on the substantial center axis 10c of a piston 10 and expands from the intake side toward the center O at the substantial same angle as the injection angle, and then converges near an ignition plug 32. Fuel particles flowing toward the exhaust side are directed together near the ignition plug 32 by squish flows on the exhaust side. Tumbles caused by the intake port converge in the spherical surface 44 without transversely diffusing by the guide groove 46 with its exhaust side groove end 46a formed higher than its intake side groove end 46b. As a result of which a richer mixture is stratified to improve the combustion performance in a lean-burn range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder injection engine, and more particularly to an in-cylinder injection engine capable of stabilizing combustion in a lean region and improving fuel consumption.

[0002]

2. Description of the Related Art As an engine, there is an in-cylinder injection type engine in which a spark plug is provided in a cylinder head at a substantially central portion of a combustion chamber and fuel is directly injected into the combustion chamber by a fuel injection valve.

In this in-cylinder injection engine, lean combustion is realized by injecting fuel during a compression process at a partial load and collecting a rich air-fuel mixture in the vicinity of the spark plug,
Improves fuel efficiency.

Further, such an in-cylinder injection type engine is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 1-219311 and 63-215816. JP 1
The one disclosed in Japanese Patent No. 219311 is defined between two squish part defining surfaces composed of a part of a piston top surface and a part of a cylinder head lower surface, has an open end and a closed end, and is open. A squish part whose end is enlarged to the vicinity of the point plug, and two or more squish part defining surfaces which are provided in the vicinity of the closed end of the squish part and partially or wholly injects fuel near the piston top dead center position By providing an injector that injects toward either one of the above, combustion is stabilized by the squish flow. JP-A-63-2
According to Japanese Patent No. 15816, the stratification is disturbed by providing a protrusion for directing the squish flow toward the ignition plug in the cavity on the top surface of the piston forming the combustion chamber with the lower surface of the cylinder head. The squish flow is directed to the spark plug in the direction to secure and promote the stratified state of the air-fuel mixture in the combustion chamber.

[0005]

However, in the conventional in-cylinder injection type engine, since combustion is performed with a uniform air-fuel mixture, a rich air-fuel mixture is stably collected in the vicinity of the spark plug, and the air-fuel mixture is mixed. However, it is difficult to stabilize combustion in a lean region, and it is not possible to sufficiently improve fuel efficiency.

[0006]

Therefore, in order to eliminate the above-mentioned inconvenience, the present invention provides an ignition plug in a cylinder head at a substantially central portion of a combustion chamber, and directly supplies fuel into the combustion chamber by a fuel injection valve. In an in-cylinder injection type engine for injecting, a guide having a spherical surface centered on the substantially central axis of the piston at the top of the piston in the cylinder and spreading from the intake side toward the center at an angle substantially equal to the injection angle A groove is provided, and an intake port is provided in the cylinder head so as to generate a vertical vortex flow in the intake air into the combustion chamber, and the fuel is discharged between the ignition plug and the intake valve on the combustion chamber wall surface of the cylinder head to the ignition plug. It is characterized in that a protrusion is provided so as to prevent it from reaching directly.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, during partial compression of the engine, during the compression process, the fuel injected by the fuel injection valve reaches the guide groove and the spherical surface while promoting atomization and reaches the spark plug. It is possible to gather in the vicinity and thus achieve stratification of the fuel, which stabilizes combustion in lean regions,
The lean limit is significantly extended, the specific heat ratio is increased, the pump loss is reduced, and the fuel loss is improved by reducing the heat loss.

[0008]

Embodiments of the present invention will be described in detail and specifically with reference to the drawings. 1 to 9 show an embodiment of the present invention. 1-3, 2 is an in-cylinder injection type 4-cylinder engine, 4 is a cylinder block, 6 is a cylinder head, 8 is a cylinder, 10 is a piston, 12 is a combustion chamber, 14 and 14 are intake ports, 16 16 is an exhaust port, 18 is an intake cam shaft, and 20 is an exhaust cam shaft.

The intake rocker arm 2 is attached to the intake camshaft 18.
An intake valve 24 that opens and closes the intake port 14 is provided so as to communicate therewith. An exhaust valve 28 for opening and closing the exhaust port 16 is provided in communication with the exhaust camshaft 20 via an exhaust rocker arm 26.

Further, as shown in FIG. 1, the cylinder head 6
A spark plug 32 housed in the spark plug hole 30 is provided at a substantially central portion of the combustion chamber 12.

Further, the cylinder head 6 has an intake port 14
A fuel injection valve 34 that injects fuel at an injection angle θ ₁ (see FIG. 6) between 14 is provided at an angle α with respect to the horizontal line.

An intake port 36 communicating with the intake port 14 is formed in the cylinder head 6.

The intake port 36, as shown in FIG.
In order to generate a longitudinal vortex flow in the intake air, one end side is open to the head upper surface 38 above the combustion chamber 12 and is inclined a little obliquely downward to the intake side, and the other end side is near the intake port 14 and the central axis 12c of the combustion chamber 12 is located. It is curved so as to face.

Further, the cylinder head 6 has an exhaust port 16
An exhaust port 40 communicating with the.

The top portion 42 of the piston 10 is shown in FIGS.
As shown in FIG. 5, a spherical surface 44 having a center O is formed on the substantially central axis 10c of the piston 10 which is aligned with the substantially central axis 12c of the combustion chamber 12, and the injection angle is increased from the intake (IN) side toward the center O. A guide groove 46 is formed which spreads at an angle θ ₂ substantially equal to θ ₁ .

Further, as shown in FIG. 5, the guide groove 46
, The height H1 of the groove end portion 46a of the exhaust (EX) side is larger in a predetermined than the height H ₂ of the groove end portions 46b of the intake (IN) side.

On the combustion chamber wall surface 48 forming the combustion chamber 12 of the cylinder head 6, as shown in FIGS.
Between the intake valve 24 and the intake valve 24, and on the side of the intake valve 24, 24 so as to prevent the fuel from directly reaching the spark plug 32. A body 50 is provided. This protrusion 50 is provided on the one side of the intake valve 2
4 and the intake valve 24 on the other side.
The other side protruding portion 50b is extended to the side, and the center side protruding portion 50c curved around the spark plug 32 so as to connect the one side and the other side protruding portions 50a, 50b.

Next, the operation of this embodiment will be described.

During partial compression of the engine 2 and during the compression stroke, the fuel injected from the fuel injection valve 34 reaches the spherical surface 44 of the guide groove 46 while promoting atomization, as shown in FIG. Collect near the stopper 32. Further, the fuel particles that are about to flow to the exhaust side are collected on the spark plug 32 side by the squish flow (arrow Q in FIG. 6) on the exhaust side. Further, a longitudinal vortex is generated by the intake port 36, and the longitudinal vortex of the intake air in the cylinder 8 is a guide groove in which the exhaust side groove end portion 46a is formed to have a height larger than that of the intake side groove end portion 46b. Due to 46, there is no lateral flow and the fuel particles collect on the flow and do not diffuse laterally and collect in the spherical surface 44.

As a result, when the engine 2 is partially loaded, the rich air-fuel mixture gathers in the spark plug 32 and the stratification of the fuel can be achieved. Therefore, the combustion in the lean region is stable, and the lean limit is the uniform air-fuel mixture. Compared with the above, it has been significantly extended, the specific heat ratio has been increased, pump loss has been reduced, heat loss has been reduced, and
Fuel efficiency can be improved.

Further, the combustion is stable in the lean region, and the lean limit is greatly extended compared to the normal homogeneous mixture, so that the fuel consumption can be improved.

Further, since the fuel does not reach the ignition plug 32 directly by the protrusion 50, it is possible to prevent fogging of the ignition plug 32, combustion fluctuations, and to reduce HC. Further, the fuel diffuses toward the protrusion 50 to promote atomization and improve combustion.

Further, due to the guide groove 46 formed so that the height H _{1 of the} exhaust side groove end 50a is larger than the height H _{2 of the} intake side groove end 50b, the fuel is not laterally diffused, and the fuel is fogged. While being promoted, it is flowed to the spherical surface 44 and efficiently gathered in the vicinity of the spark plug 32, and the presence of the projection 50 can restrict the flow of the intake port 36 on the spark plug 32 side. Therefore, that is, the central axis 1 of the combustion chamber 12
Since the inflow of the intake air from the 2c side is restricted, the longitudinal vortex of the intake air is strengthened, and the combustion can be promoted.

[0024]

As is apparent from the above detailed description, according to the present invention, the top of the piston in the cylinder has a spherical surface centered on the substantially central axis of the piston and extends from the intake side to the center. And a guide groove that spreads at an angle approximately equal to the injection angle,
An intake port is provided on the cylinder head so as to generate a longitudinal vortex flow in the intake air into the combustion chamber, and the fuel is prevented from directly reaching the ignition plug between the ignition plug and the intake valve on the combustion chamber wall surface of the cylinder head. By providing the protrusion, the fuel injected by the fuel injection valve during the compression process during the partial load of the engine reaches the guide groove and the spherical surface while promoting atomization and collects in the vicinity of the spark plug. Therefore, stratification of the fuel can be achieved, which stabilizes the combustion in the lean region, greatly extends the lean limit, increases the specific heat ratio, and further reduces the pump loss, and By reducing heat loss, fuel efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of one side of an engine.

FIG. 2 is a cross-sectional view of the other side of the engine.

FIG. 3 is a bottom view of the combustion chamber.

FIG. 4 is a plan view of a piston.

5 is a cross-sectional view taken along line 〓〓 of FIG.

FIG. 6 is a schematic diagram of an engine in a fuel injection state.

FIG. 7 is a bottom view of a combustion chamber provided with a protrusion.

FIG. 8 is a cross-sectional view taken along the line II-II of FIG.

FIG. 9 is a diagram showing an improved state of fuel efficiency.

[Explanation of symbols]

 2 engine 6 cylinder head 8 cylinder 10 piston 12 combustion chamber 24 intake valve 32 spark plug 34 fuel injection valve 36 intake port 44 spherical surface 46 guide groove 50 projecting body

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Claims (2)

[Claims] 1. An in-cylinder injection engine in which a spark plug is provided in a cylinder head in a substantially central portion of a combustion chamber, and fuel is directly injected into the combustion chamber by a fuel injection valve, and the piston is provided at the top of the piston in the cylinder. An induction groove having a spherical surface centered on the substantially central axis and extending from the intake side toward the center at an angle substantially equal to the injection angle is provided, and a vertical vortex flow is generated in the intake air into the combustion chamber. A port is provided in the cylinder head, and a projection is provided on a wall surface of the combustion chamber of the cylinder head so as to prevent fuel from directly reaching the ignition plug between the ignition plug and the intake valve. In-cylinder injection type engine. 2. The in-cylinder injection engine according to claim 1, wherein the guide groove is formed such that a height of a groove end portion on an exhaust side is larger than a height of a groove end portion on an intake side.