JP2002021570A - Cylinder injection type gasoline engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form stratified air-fuel mixture by a simple-shaped combustion chamber without depending on strong air flow, and to restrain deposite of fuel drops onto a piston head part and a wall face thereof to the minimum. SOLUTION: Plural fuel injection valves 12, 13 are arranged in cylinder sidewalls 2b, 2c to be opposed, and fellow atomized fuels 15 injected from the injection nozzles 12, 13 and entrained air 16 are collided to form a vapor generating part 17 comprising the stratified air-fuel mixture in an inside of which a concentration is higher than that in an outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasoline direct injection engine and, more particularly, to a gasoline direct injection engine capable of stably achieving a lean air-fuel ratio combustion by forming a stratified mixture.

[0002]

2. Description of the Related Art Conventionally, in a gasoline in-cylinder injection engine, swirl (lateral vortex) or tumble (longitudinal vortex) is generated by air flow in order to realize lean air-fuel ratio combustion with a stratified mixture, and sprayed on the top of a piston. There is one in which a concave portion is formed to guide the fuel and the fuel collides with the top of the piston.

[0003]

The above-mentioned conventional apparatus has the following problems.

Since strong air flow is used, the air flow resistance increases, resulting in a loss horsepower, and the air flow is easily affected by cycle fluctuations of the air flow and engine speed fluctuations.

In order to form a recess at the top of the piston,
The shape of the piston becomes complicated due to its irregular shape,
The reliability is poor, the shape of the combustion chamber deteriorates, the output at the stoichiometric ratio decreases, and the piston weight increases, so that it is not suitable for high rotation.

[0006] Since fuel collides with the top of the piston, fuel droplets that do not evaporate remain, and unburned HC increases. In addition, since the time from injection to ignition is short during stratified combustion, fuel droplets that do not evaporate remain, and this also increases unburned HC.

The present invention has been made in view of the above-mentioned conventional problems, and a stratified air-fuel mixture can be formed by a combustion chamber having a simple shape without depending on a strong air flow. It is an object of the present invention to provide a gasoline in-cylinder injection engine capable of minimizing the adhesion of fuel droplets.

[0008]

According to a first aspect of the present invention, a plurality of fuel injection valves are arranged on a cylinder side wall so as to face each other,
A gasoline in-cylinder injection engine characterized by forming a steam generating portion made of a stratified mixture having a higher concentration than the outside by colliding the spray fuel and entrained air injected from each fuel injection valve. is there.

According to a second aspect of the present invention, in the first aspect, the steam generating portion formed by the collision has a substantially spherical shape and rises on the ceiling surface of the combustion chamber on the airflow rising after the collision. At the same time, the air-fuel mixture spreads along the ceiling surface, and a high concentration air-fuel mixture layer is formed along the ceiling surface.

According to a third aspect of the present invention, in the first or second aspect, the two fuel injection valves are opposed to each other on a straight line whose spray axis is orthogonal to the cylinder bore axis when viewed in the cylinder bore axis direction. It is characterized by being arranged at an angle of attack of 30 degrees.

[0011]

According to the first aspect of the present invention, a plurality of fuel injection valves are arranged on the cylinder side wall so as to face each other, and the fuel spray injected from each of the fuel injection valves is caused to collide. The atomized fuel and the entrained air engulfed by the atomized fuel collide with each other, thereby forming a steam generating portion in which the inside is composed of a stratified mixture having a higher concentration than the outside. Since the stratified mixture is thus formed, the lean air-fuel ratio combustion is performed stably.

According to the second aspect of the present invention, in the steam generating section, the residence time of the sprayed fuel is ensured and the evaporation is promoted, and the steam generating section rises on the air flow rising after the collision. Then it hits the ceiling of the combustion chamber and spreads further laterally. In this way, a stratified air-fuel mixture composed of a high-concentration air-fuel mixture is formed on the ceiling surface of the combustion chamber where the electrode of the ignition plug is located, and the lean air-fuel ratio combustion is performed stably.

According to the third aspect of the present invention, the two fuel injection valves are arranged so that the spray axes are opposed to each other and form an angle of attack of 10 to 30 degrees. The fuel that collided collides at the center of the cylinder bore and in the portion close to the combustion chamber, and the steam generation portion composed of the above-described stratified air-fuel mixture is reliably formed. Therefore, the lean air-fuel ratio combustion can be stably performed.

Further, since the present invention is a method of forming a stratified mixture by the collision of a spray fuel and entrapped air, the conventional method generates a loss horsepower by using a strong air flow, and forms a recess at the top of a piston. Therefore, problems such as complication of the piston shape, deterioration of durability, and the like, and increase of unburned HC due to collision of fuel with the piston top portion do not occur.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 12 are views for explaining a gasoline in-cylinder injection engine according to an embodiment of the present invention. FIG. 1 is a sectional side view of the engine, and FIGS.
FIG. 2 is a schematic diagram of a stratified mixture formation process.

In FIG. 1, reference numeral 1 denotes a gasoline in-cylinder injection type four-stroke engine, and the engine 1 has the following general structure. A cylinder block 2, a cylinder head 3, and a head cover 4 are stacked and fastened on a crankcase (not shown), and a piston 5 slidably inserted into a cylinder bore 2a of the cylinder block 2 is connected to a crankshaft 7 by a connecting rod 6. I have. Top surface 5 of the piston 5
a is formed flat, and the piston 5 is located at the bottom dead center in FIG. The piston 5 may be of a type in which a relief recess for preventing interference with the intake valve 8 and the exhaust valve 9 is formed on the top surface.

A combustion recess 3a, which forms a combustion chamber a with the top surface 5a of the piston 5 and the cylinder bore 2a, is provided on the lower mating surface of the cylinder head 3, and a ceiling surface of the combustion recess 3a. Although not shown, the electrode of the ignition plug is located at the center. An intake valve opening 3b and an exhaust valve opening 3c are formed in the ceiling surface.
3c is led out to the rear wall surface and the front wall surface of the cylinder head 3 by an intake port 3d and an exhaust port 3e.

Further, the intake valve opening 3b and the exhaust valve opening 3c can be opened and closed by an intake valve 8 and an exhaust valve 9. The intake valve 8 and the exhaust valve 9 are urged in the closing direction by an intake valve spring 8a and an exhaust valve spring 9a, and are opened and closed by an intake camshaft 10 and an exhaust camshaft 11 via an intake lifter 8b and an exhaust lifter 9b. Driven.

The front wall 2 of the cylinder block 2
b, front and rear fuel injection valves 12, 13 are disposed on the rear wall 2c. The spray nozzles 12a and 13a of the fuel injection valves 12 and 13 are of a type having a spray angle of 15 to 25 degrees, the injected fuel having a solid conical shape, and generating no swirl.

As shown in FIG. 2, the fuel injection valves 12 and 13 are arranged so that the respective injection axes f face each other on a straight line c passing through the axis b when viewed in the direction of the cylinder bore axis b. I have. The straight line c can be arbitrarily selected in the plane shown in FIG. In addition, each of the above fuel injection valves 12 and 13
As shown in FIG. 1, when viewed in the cam axis direction, the angle of attack θ between a straight line d perpendicular to the cylinder bore axis b and the injection axis f forms an angle of 10 to 30 degrees. Further, the injection nozzle 12 of each of the fuel injection valves 12 and 13 described above.
a, 13a are the top surface 5a of the piston 5 located at the bottom dead center.
From about 1/3 of the piston stroke. The injection nozzle position is approximately 100 degrees before the top dead center (BTDC) in terms of the rotation angle of the crankshaft.

Next, a stratified mixture forming process in the engine of the embodiment will be described.

In the stratified mixture formation process, the fuel injection valves 12 and 13 having a spray angle of 20 degrees are connected to the injection nozzles 12 and 13 thereof.
a, 13a are located at 100 degrees BTDC and the angle of attack is 3
Arranged at 0 degree, engine speed 3000
rpm, throttle opening (engine load) 25%, fuel pressure 3MP, and fuel injection start timing BTDC1
The fuel was injected at 70 degrees.

FIG. 3 shows the overall shape and the like of the non-evaporated droplets of the fuel injected from the fuel injection valve, and FIG. 4 shows the entrainment moving by being entrained by the injected fuel. 3 shows an air velocity vector. 5 to 10 simultaneously show the spray fuel and entrained air shown in FIGS. Further, FIG. 11 shows a state of a stratified mixture, and FIG. 12 schematically shows a stratified state of FIG.

As can be seen from FIG. 3, the fuel injection valves 12, 1
Spray fuel 15 injected around 3 to 170 BTDC,
15 collide near 140 BTDC. In the spray fuel 15, the portion 15a immediately after exiting the injection nozzles 12a and 13a has a particle diameter of 25 to 50 μm, and the collision point portion 15b has a particle diameter of 25 μm or less. Then, the spray fuel as a whole becomes substantially spherical and rises due to the collision (see 130 to 100 BTDC), and spreads laterally along the ceiling wall of the combustion recess 3 a (90 to 60 B).
See TDC).

4 to 10 accompanying the fuel injection.
As can be seen from the figure, the velocity energy of the spray fuel gives a velocity vector to the surrounding air, and the entrained air 1
As a result, a flow that follows the spray fuel is generated, and the entrained air 16 collides with each other near 140 BTDC, and the impinging air 16 'thereafter becomes an upward flow. In this way, the spray fuel 15 and the entrapped air 16 are mixed, and the above-mentioned liquid fuel in the form of droplets evaporates to become a gas, thereby forming a substantially spherical steam generating portion 17 (see FIG. 11) as a whole.

As shown at 130 to 100 BTDC in FIGS. 11 and 12, the steam generating section 17 rides on the upward flow of the entrained air after the collision of the atomized fuel and the entrained air toward the combustion recess 3a ceiling surface. As shown in 90 to 20 BTDC, the combustion recess 3a
Spreads along the ceiling surface and is ignited near the 20BTDC.

Here, the above-mentioned steam generating section 17 is provided in FIG.
As shown in FIG. 12, in the case of 130 to 100 BTDC, the inside is a stratified mixture having a higher concentration than the outside and a substantially spherical shape. Specifically, the center portion 17a has an air-fuel ratio of 20 to 30,
As the outer layers 17b, 17c, and 17d extend from the central portion 17a, the air-fuel ratio becomes 30 to 40, 40 to 60, and 60 to 80.
It has become.

The above substantially spherical steam generating section 17
Changes from 90 BTDC to 60 BTDC, and changes to a steam-generating portion 17 ′ having an upper portion along the ceiling surface and a lower portion pressing a sphere. In the steam generating portion 17 ', the portion 17f along the ceiling surface of the combustion recess 3a has an air-fuel ratio of 10 to 20, and the air-fuel ratio increases from the portion 17f to the lower layers 17a', 17b ', 17c', and 17d '. -30, 30-40, 40-60, 60
~ 80. In this way, the portion 17f along the ceiling surface becomes a stratified mixture having a high concentration, and 50 to 20 BT.
In DC, this stratified mixture is maintained.

As described above, in the present embodiment, the fuel spray from the two fuel injection valves 12 and 13 is caused to collide near the center of the cylinder bore and near the combustion chamber. The entrapped air forms a substantially spherical steam generating section 17 which is made of a stratified mixture having a higher concentration than the outside, thereby ensuring the residence time of the sprayed fuel and promoting the evaporation.

Further, the steam generating portion 17 rises on the rising air and hits the ceiling surface of the combustion chamber, and becomes a pressed steam generating portion 17 'spreading along the ceiling surface. The steam generating portion 17 'is provided with a portion 17f along the ceiling surface.
Is a stratified mixture having a high concentration (air-fuel ratio of 10 to 20). As a result, a high-concentration air-fuel mixture is located on the ceiling surface of the combustion chamber where the electrode of the ignition plug is located. As a result, stable combustion can be achieved while maintaining a lean air-fuel ratio as a whole, and exhaust gas can be purified. In addition, fuel efficiency can be improved.

In this embodiment, two fuel injection valves 1
2, 13 are arranged so that the spray axis f faces each other and form an angle of attack of 10 to 30 degrees, and the spray fuel injected from each of the fuel injection valves 12, 13 is provided at the center of the cylinder bore and near the combustion chamber. With a simple configuration in which collision occurs at a portion, a steam generating section 17 composed of a stratified mixture can be reliably formed, and the steam generating section 17 is formed as a steam generating section 17 ′ along the ceiling surface of the combustion chamber. The portion 17f along the line can be a stratified mixture having a high concentration, the high concentration mixture can be located near the electrode of the ignition plug, and the lean air-fuel ratio combustion can be stably performed.

Further, in the present embodiment, a stratified mixture is formed by the collision of the atomized fuel 15 and the entrapped air 16, so that there is no problem caused by the conventional method. That is, because it does not use strong airflow,
No loss horsepower is generated due to the increase in airflow resistance. Further, since no concave portion is formed at the top of the piston, problems such as complication of the piston shape, deterioration of durability and reliability are not caused. Further, since the fuel does not collide with the top of the piston, there is no problem that unburned HC increases.

[Brief description of the drawings]

FIG. 1 is a sectional side view of a gasoline in-cylinder injection engine according to an embodiment of the present invention.

FIG. 2 is a cross-sectional plan view showing a fuel injection valve arrangement state of the engine.

FIG. 3 is a stroke diagram showing a state of spray fuel in a mixture formation process in a combustion chamber of the engine.

FIG. 4 is a process chart showing a state of entrapped air in the air-fuel mixture forming process.

FIG. 5 is an enlarged stroke diagram showing the sprayed fuel and the entrained air in the above mixture formation process at the same time.

FIG. 6 is an enlarged stroke diagram showing the sprayed fuel and the entrapped air in the mixture formation process at the same time.

FIG. 7 is an enlarged stroke diagram simultaneously showing the spray fuel and the entrained air in the air-fuel mixture forming process.

FIG. 8 is an enlarged stroke diagram showing the spray fuel and the entrapped air in the mixture formation process at the same time.

FIG. 9 is an enlarged stroke diagram showing the sprayed fuel and the entrapped air in the air-fuel mixture forming process at the same time.

FIG. 10 is an enlarged stroke diagram showing the sprayed fuel and the entrained air in the air-fuel mixture forming process at the same time.

FIG. 11 is a diagram showing a stratified mixture generation state of a steam generation section in the mixture formation process.

FIG. 12 is a schematic diagram showing a stratified mixture generation state of a steam generation section in the mixture formation process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gasoline in-cylinder injection engine 2 Cylinder block 2b, 2c Cylinder side wall 12, 13 Fuel injection valve 15 Spray fuel 16 Entrained air 17 Steam generation part b Cylinder bore axis c Straight line orthogonal to cylinder bore axis f Injection axis θ Attack angle

Continued on the front page F term (reference) 3G023 AA02 AA04 AA07 AB01 AC05 AD03 AG01 AG02 3G024 AA22 AA32 BA00 DA01 FA00 3G066 AA02 AA04 AA05 AB02 AD12 BA02 BA17 BA26 CC06U CE21

Claims (3)

[Claims] A plurality of fuel injection valves are arranged on a side wall of a cylinder so as to face each other, and the sprayed fuel and entrained air injected from each of the fuel injection valves collide with each other, whereby the inside of the fuel tank is stratified with a higher concentration than the outside. An in-cylinder gasoline injection engine characterized by forming a steam generating section made of an air-fuel mixture. 2. The steam generating portion according to claim 1, wherein the steam generating portion formed by the collision has a substantially spherical shape, and rises to the combustion chamber ceiling surface along with the airflow rising after the collision and along the ceiling surface. A gasoline in-cylinder injection engine, characterized in that the gas mixture expands and forms a highly concentrated air-fuel mixture layer along the ceiling surface. 3. The fuel injection valve according to claim 1, wherein the two fuel injection valves face each other on a straight line perpendicular to the cylinder bore axis when the spray axis is viewed in the cylinder bore axis direction.
A gasoline in-cylinder injection engine, wherein the engine is disposed so as to form an attack angle of 0 degrees.