JPH10331639A - Cylinder direct injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote mixture of fuel and air by securing a swirl at the time of introducing intake air from both intake air ports. SOLUTION: This internal combustion engine not only directly injects fuel to a combustion chamber 4 but also ignites and burns injected fuel by an ignition plug 5. A pair of air intake valves 6a, etc., and a pair of intake air ports 10, 11 roughly in parallel with each other communicated to them are provided on a cylinder head 1. The one 10 of the intake air ports 10, 11 is formed on a low port, and the other 11 is formed on a high port, and a fuel injection valve 9 is arranged between these intake air ports 10, 11 and position below them. An intake air flow from the low port is stronger than an intake air flow from the high port, even when both of the intake air flows collide against each other, a swirl is maintained as a whole, and mixture of fuel and air is promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an internal combustion engine for directly injecting fuel into a cylinder, and more particularly to an improvement in an intake port.

[0002]

2. Description of the Related Art In a compression stroke of an internal combustion engine, fuel is directly injected into a combustion chamber to form a combustible air-fuel mixture layer around an ignition plug at the time of ignition. There is an in-cylinder direct injection type internal combustion engine capable of realizing stable combustion (see Japanese Patent Application Laid-Open No. 8-35429).

This internal combustion engine is configured as shown in FIGS.

1 is a piston, 2 is a cylinder head, 3 is a cylinder block, 4 is a combustion chamber, and an ignition plug 5 is mounted on the cylinder head 1 so as to be located at the center of the combustion chamber. 6a, 6b and exhaust valves 7a, 7
b is arranged.

[0005] The intake ports 8a and 8b are formed in parallel with each other, and are located between the intake ports 8a and 8b. The fuel injection valve is oblique to the piston axis and the fuel spray is directed toward the center of the combustion chamber. 9 is attached.

In an operation region where the engine load is relatively small, the fuel injection timing is set in the latter half of the compression stroke, thereby preventing the diffusion of the injected fuel and forming a combustible mixture layer near the ignition plug 5. By introducing the intake air only from the intake port 8a, swirl is generated, and stable stratified combustion can be achieved even with a lean mixture as a whole. Further, in the operation region where the engine load is large, fuel is injected in the intake stroke to promote mixing with the air taken in from both the intake ports 8a and 8b, thereby reliably burning the air-fuel mixture near the stoichiometric air-fuel ratio. Ensure high output.

[0007]

However, in this case,
In a high-load region where homogeneous mixture combustion is performed, if fuel and air are not sufficiently mixed, combustion deteriorates and unburned H
C may increase, or output and fuel economy characteristics may decrease.

However, intake air is introduced from both intake ports 8a and 8b, and the intake air flows collide with each other to weaken swirl, resulting in insufficient mixing of fuel and air.

On the other hand, if intake air is introduced only from one intake port so as to generate a strong swirl even in a high load region, the intake resistance becomes large and high output cannot be exhibited.

An object of the present invention is to solve such a problem.

[0011]

A first aspect of the present invention is a cylinder direct injection type internal combustion engine in which fuel is directly injected into a combustion chamber and the injected fuel is ignited and burned by an ignition plug. A pair of intake valves and a pair of substantially parallel intake ports connected thereto are formed, one of the intake ports is formed as a high port, the other is formed as a low port, and the fuel injection is located between and below these intake ports. The valve was located.

According to a second aspect of the present invention, a swirl control valve that closes at least in a partial load region is provided at the high port.

According to a third aspect of the present invention, the fuel injection valve is set at the height,
An offset is provided so as to be substantially parallel to the low port axis and approach the high port side.

In a fourth aspect, claims 1 and 2 are:
The fuel injection valve intersects with the high and low port axes and is arranged obliquely from the lower surface of the high port toward the low port so that the direction of fuel spray is adjusted to swirl.

[0015] In a fifth aspect, in claims 1 and 2,
The fuel injection valve is disposed substantially parallel to the high and low port axes, and the injection port of the fuel injection valve is deflected so that the direction of fuel spray is directed to the low port side.

[0016] In a sixth aspect, claims 1 to 5 are:
The opening timing of the intake valve provided at the low port is earlier than the opening timing of the intake valve provided at the high port.

[0017]

According to the first aspect of the present invention, in the partial load region of the engine in which stratified mixture combustion is performed, fuel is injected late in the compression stroke to prevent diffusion of the fuel and to prevent the fuel from being diffused near the spark plug. While forming a combustible mixture layer, the intake air flows into the combustion chamber from one of the intake ports to generate a strong swirl, thereby enabling stable combustion even with a lean mixture as a whole.

In an operation region where the engine load is large and homogeneous mixture combustion is performed, fuel is injected during an intake stroke, and at this time, intake air is introduced from both intake ports, so that the fuel is taken up until ignition. Can be sufficiently mixed and stirred. In this case, one intake port is formed as a high port and the other is formed as a low port, and the intake flow from the low port has a smaller inflow angle with respect to the cylinder axis than the intake flow from the high port,
The swirl momentum is strengthened. Therefore, even if both intake flows collide with each other, swirl from the low port direction is generally maintained, and even in a high load region, mixing of fuel and air is promoted, and a uniform mixture layer is formed. Unburned H
C can be reduced and high output can be maintained.

In the second invention, the swirl control valve which closes in the partial load region where the stratified mixture combustion is performed is on the high port side, and intake air is introduced from the low port, so that a strong swirl can be generated in the cylinder. The stability of stratified mixture combustion is improved.

In the third aspect, since the fuel injection valve is offset to the high port side, the inflow angle on the low port side can be set smaller, and the swirl can be strengthened.

In the fourth and fifth aspects, the fuel spray is put on the swirl to promote the vaporization of the fuel and to further improve the combustion.

According to the sixth aspect of the invention, since the opening timing of the intake port on the low port side is advanced, the swirl can be further enhanced, and the combustion can be further improved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described with reference to the drawings.

In FIGS. 1 and 2, 1 is a piston, 2 is a cylinder head, 3 is a cylinder block, and 4 is a combustion chamber defined by them.

The ignition plug 5 is disposed on the cylinder head 2 at a position substantially at the center of the combustion chamber when viewed in plan. The ignition plug 5 is substantially parallel to the cylinder line center line M including the cylinder center. A pair of intake valves 6a, 6b and an exhaust valve 7a, 7b are arranged to face each other with M interposed therebetween.

A pair of intake ports 10 and 11 are connected to the combustion chamber 4 via the intake valves 6a and 6b. These intake ports 10 and 11 are formed such that their port axes are substantially parallel to each other and are substantially perpendicular to the cylinder line center line M.

The one intake port 10 is formed as a low port having a small inclination angle with respect to a plane perpendicular to the piston axis (cylinder axis), that is, a small inflow angle into the cylinder. The intake port 11
It is formed at a high port with a large inclination angle so that intake air flows in from the piston axial direction.

Although not shown, a swirl control valve is provided at the intake port 11 serving as a high port, and the swirl control valve closes the intake port 11 in an engine partial load region where stratified mixture combustion is performed. The intake air flows into the cylinder only from the intake port 10 which generates a strong swirl.

A fuel injection valve 9 is provided between and below the intake ports 10 and 11. The fuel injection valve 9 is provided to be inclined with respect to the cylinder axis within a range that does not interfere with the intake ports 10 and 11, and is mounted so that the fuel spray is directed toward the center of the combustion chamber.

The operation will be described below.

First, in the operating region where the engine load is a partial load and stratified mixture combustion is performed, the swirl control valve of the intake port 11 is closed, and intake air is introduced only from the intake port 10 into the cylinder during the intake stroke. And a strong swirl is formed.

Fuel is injected from the fuel injection valve 6 in the latter half of the compression stroke. At the time of fuel injection, the piston 1 rises, and the fuel spray injected from the fuel injection valve 9 goes to the ignition plug 5 at the center of the combustion chamber.

Since the fuel injection timing is in the latter half of the compression stroke,
The time until the piston 1 reaches the compression top dead center is short, the fuel spray does not spread evenly in the combustion chamber, and a rich mixture layer in the flammable range is formed and maintained near the ignition plug 5 at the time of ignition. .

The flammable mixture layer is ignited by the ignition action of the ignition plug 5, and the combustion is propagated to the surrounding lean mixture layer by swirling the gas flow around this portion. Therefore, stable combustion is performed even with a lean mixture as a whole.

On the other hand, in the homogeneous mixture combustion operation region where the engine load is large, the fuel injection from the fuel injection valve 6 is advanced to the intake stroke, and the swirl control valve of the intake port 11 is fully opened.

For this reason, the intake air flows into the cylinder from both intake ports 10 and 11, and generates swirls in opposite directions. However, one intake port 10 is a low port, and the other intake port 11 is a high port. In the intake flow from a low port having a small inflow angle, swirl is less likely to be attenuated. The swirl is weak due to the large angle. Therefore, even if both intake air flows collide, the swirl indicated by the arrow on the low port side where the power is strong is maintained, and the mixing of fuel and air is promoted.

As a result, the mixture can be made uniform, and stable and stable combustion can be realized, and unburned HC can be reduced.

The present invention is more effective for a short stroke engine in which swirl is more likely to be attenuated than a long stroke engine having a large piston stroke.

Next, another embodiment shown in FIG. 3 will be described.

This means that the fuel injection valve 9 is connected to the intake ports 10 and 1
1 is parallel to, but offset (translated to) the high port side.

In this case, interference between the fuel injection valve 9 and the low-port intake port 10 can be avoided, so that the low-port can be made lower and the drop from the high-port side can be made large, and high-load operation can be performed. The swirl at the time can be further strengthened, contributing to improved combustion.

The embodiment shown in FIG. 4 will be described.

This means that the fuel injection valve 9 is connected to the intake ports 10, 1
The main body 9b of the fuel injection valve 9 is positioned below the high port intake port 11 so as to inject fuel toward the low port side while intersecting the port axis of the first port. Note that the fuel injection valve 9 is installed so that the injection portion 9 a of the fuel injection valve 9 is located between the intake ports 10 and 11 and at the periphery of the combustion chamber 4.

In this way, the fuel spray from the fuel injection valve 9 is put on the swirl mainly from the intake port 10 which is a low port, thereby promoting the mixing and vaporization of the fuel and the air, and further improving the combustion. I can do it.

The embodiment shown in FIG. 5 will be described.

This means that, similarly to the embodiment of FIG. 3, the fuel injection valve 9 is parallel to the port axes of the intake ports 10 and 11 and is offset toward the higher intake port 11 side.
The injection port 9c of the fuel injection valve 9 is deflected so that the fuel spray is directed to the swirl from the low port.

In this case, the structure of the fuel injection valve 9 needs to be changed, but the fuel spray can be swirled in the same manner as in the embodiment of FIG. 4 to promote the vaporization of the fuel. In addition, combustion can be improved.

Next, in the embodiment shown in FIG. 6, the intake port 1 which is a low port has the same configuration as the above-described embodiments.
The opening timing of the intake valve 6a on the 0 side is set earlier than the opening timing of the intake valve 6b on the intake port 11 side which is a high port.

As a result of the earlier opening timing of the low-port-side intake valve 6a, the intake air from the intake port 10 is introduced before the intake of the intake air from the opposite direction, and the intake swirl is increased accordingly. it can.

As a result, the swirl in the high load operation region is strengthened, and the combustion of the homogeneous mixture can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a plan view showing a second embodiment.

FIG. 4 is a plan view showing a third embodiment.

FIG. 5 is a plan view showing a fourth embodiment.

FIG. 6 is an explanatory diagram showing intake valve opening characteristics of a fifth embodiment.

FIG. 7 is a longitudinal sectional view of a conventional example.

FIG. 8 is a plan view of the same.

[Explanation of symbols]

 Reference Signs List 1 piston 2 cylinder head 3 cylinder block 4 combustion chamber 5 spark plug 6a intake valve 6b intake valve 9 fuel injection valve 10 intake port 11 intake port

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02B 31/02 F02B 31/02 J F02D 13/02 F02D 13/02 J F02F 1/42 F02F 1/42 F F02M 61/14 310 F02M 61/14 310A 69/00 360 69/00 360C 69/04 69/04 P

Claims (6)

[Claims] 1. Injecting fuel directly into a combustion chamber,
In a direct injection type internal combustion engine in which injected fuel is ignited and burned by an ignition plug, a pair of intake valves and a pair of substantially parallel intake ports connected to these are provided in a cylinder head, and one of the intake ports is set to a high port. A direct injection type internal combustion engine, wherein the other is formed as a low port, and a fuel injection valve is disposed between and below these intake ports. 2. The direct injection internal combustion engine according to claim 1, wherein a swirl control valve that closes at least in a partial load region is provided at the high port. 3. An in-cylinder direct injection internal combustion engine according to claim 1, wherein the fuel injection valve is provided substantially parallel to the high and low port axes and offset so as to approach the high port side. 4. The fuel injection valve according to claim 1, wherein the fuel injection valve intersects the high and low port axes and is arranged obliquely from a lower surface of the high port toward the low port so that the direction of fuel spray is adjusted to swirl. 3. A direct injection internal combustion engine according to item 2. 5. The fuel injection valve according to claim 1, wherein the fuel injection valve is disposed substantially parallel to the high and low port axes, and the injection port of the fuel injection valve is deflected so that the direction of fuel spray is directed to the low port side. An in-cylinder direct injection internal combustion engine. 6. An in-cylinder direct cylinder according to claim 1, wherein the opening timing of the intake valve provided at the low port is earlier than the opening timing of the intake valve provided at the high port. Injection type internal combustion engine.