JP2001280139A - Intake stratification method in direct injection-type internal combustion engine and stratifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a combustion state by stratifying the intake of a combustion chamber onto the inside and outside of an approximately hemispherical face or approximately flat hemispherical face in starting the fuel combustion. SOLUTION: In this direct injection-type internal combustion engine for injecting the fuel to a combustion chamber 1 from a fuel injection valve 2, the combustion chamber 1 is provided with intakes 11 and 12 of different compositions on inside and outside regions of the approximately hemispherical face or the approximately flat hemispherical face 13 around a fuel injecting position in starting the fuel combustion near a final period of a compressing stroke. A stratification pattern and a stratification degree of the combustion chamber are changed corresponding to an operating condition of the direct injection-type internal combustion engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for stratifying intake air of a combustion chamber in a direct injection type internal combustion engine in which fuel is injected into a combustion chamber.

[0002]

2. Description of the Related Art In a direct injection compression ignition internal combustion engine equipped with an exhaust gas recirculation system, as disclosed in Japanese Patent Application Laid-Open No. H11-148429, the intake air of a combustion chamber is reduced in order to reduce harmful substances in the exhaust gas. Stratification techniques have been proposed.

[0003] The combustion chamber is provided with two intake ports for concentrically forming a swirl flow in the same direction. In the intake port on the upstream side of the swirl flow, a small-diameter swirl flow is provided at the center of the combustion chamber, A large-diameter swirl flow is formed at the periphery of the combustion chamber at the intake port.

[0004] The recirculated exhaust gas is mixed into the intake air passing through the upstream intake port, and the recirculated exhaust gas is not mixed into the intake air passing through the downstream intake port. The intake air mixed with the exhaust gas is disposed in the annular region around the combustion chamber, and the intake air is not mixed with the recirculated exhaust gas.

[0005]

However, in the above-mentioned prior art, a small-diameter swirl flow and a large-diameter swirl flow are formed inside and outside the combustion chamber. Therefore, the small-diameter swirl flow expands outward due to the centrifugal force, and collides and mixes with the large-diameter swirl flow whose diameter does not increase due to the peripheral wall of the combustion chamber. Therefore, it is difficult to arrange intake air having different compositions in the cylindrical region at the center of the combustion chamber and the annular region at the periphery.

Even if swirl flows of small diameter and large diameter are formed inside and outside of the combustion chamber in the intake stroke, in the next compression stroke, the intake air on the peripheral portion of the piston top surface becomes the center of the piston top surface. A large swirl flow around the combustion chamber is transported to the center of the combustion chamber by the squish flow, and collides with the small swirl flow at the center of the combustion chamber because a squish flow flows into the cavity of the combustion chamber. Will do. Therefore, it is difficult to maintain the stratified state inside and outside the intake formed in the intake stroke until the end of the compression stroke.

After all, at the time near the end of the compression stroke in which fuel is sprayed into the combustion chamber to start combustion, intake air having a different composition is arranged in the central cylindrical area and the peripheral annular area of the combustion chamber. Is not recognized.

[0008] Unless the intake air of the combustion chamber is stratified to a desired state at the start of fuel combustion, the combustion of fuel in the combustion chamber cannot be controlled as desired.

[0009]

1) In a direct-injection compression ignition internal combustion engine, the fuel flow injected from the fuel injection valve during intake of the combustion chamber uses the air around it at the base side as fuel. While entraining inside the flow, the surrounding air is entrained to the outer periphery of the fuel flow to induce an air flow accompanying the fuel flow.

Further, the fuel flow injected into the intake air of the combustion chamber flies at a high speed, is divided and atomized, becomes steam, and burns at a tip side portion where the steam is generated to generate a flame. In some cases, the fuel flow burns on the base side from the front end portion to generate a flame, but the portion where the high-temperature flame is generated on a large scale is the front end portion of the fuel flow.

In the combustion chamber, a fuel-air mixture region is formed at the base of the fuel flow to mix the fuel and air to form a fuel-air mixture while the fuel is being injected and combusted. At the front end side, a flame generation region where the air-fuel mixture burns violently and a high-temperature flame is generated on a large scale is formed, and is roughly divided into an air-fuel mixture formation region and a flame generation region.

The composition of the air-fuel mixture formed in the air-fuel mixture formation region of the combustion chamber is affected by the composition of the intake air present in the air-fuel mixture formation region at the time of fuel injection or at the start of combustion.

The air-fuel mixture formed in the air-fuel mixture formation region of the combustion chamber is carried to the flame generation region of the combustion chamber by a fuel flow or an air-fuel mixture flow. The flame generation region of the combustion chamber is composed of the mixture carried from the mixture formation region to the flame generation region, the intake air existing in the flame generation region before the start of combustion, and the gas generated by burning the fuel in the flame generation region. Therefore, the fuel is burned in a state in which they exist. The combustion state of the fuel in the combustion chamber is affected by the composition of the gas present in the flame generation region at the start of combustion.

In other words, a gas having a composition suitable for forming a desired air-fuel mixture is selected as the gas present in the air-fuel mixture forming region of the combustion chamber at the time of fuel injection or at the start of combustion. When a gas having a composition suitable for generating a desired combustion state is selected as the gas existing in the flame generation region, the combustion state of the fuel in the combustion chamber can be controlled as desired.

That is, the combustion state of the fuel in the combustion chamber can be controlled by stratifying the intake air of the combustion chamber into the mixture formation region and the flame generation region.

2) The flame generation start position at which the generation of a large-scale high-temperature flame at the front end portion of the fuel flow starts is defined as the distance from the injection port of the fuel injection valve to the position at which the fuel flow starts to be split. The position is about 1 to 1.5 times as long as the spray split distance from the injection valve orifice position. Note that the spray split distance = 15.8 (fuel density / air density) ^1/2 · (fuel injection nozzle diameter).

Further, the fuel injection valve has a large number of injection ports arranged at the center of the ceiling surface of the combustion chamber facing the top surface of the piston. It is inclined toward the top surface of the piston, and moves toward the periphery of the cavity at the center of the top surface of the piston near the end of the compression stroke.

Therefore, the flame generation region of the combustion chamber is a region which is separated from the position of the fuel injection valve orifice of the combustion chamber by about 1 to 1.5 times or more of the spray split distance in each fuel injection direction. It becomes almost symmetrical about the axis. The mixture formation region is a region within about 1 to 1.5 times the spray split distance from the fuel injection valve orifice position of the combustion chamber in each fuel injection direction, and is substantially symmetric with respect to the central axis of the combustion chamber. .

From these facts, in the vicinity of the end of the compression stroke in which the fuel starts burning, the region inside the substantially hemispherical surface or the approximately flat hemispherical surface centered on the center of the ceiling surface of the combustion chamber into which the fuel is injected. When the intake air of the combustion chamber can be stratified in the outer region, the combustion state of the fuel can be controlled by arranging the intake air having a desired composition in each of the inner region and the outer region.

3) A plurality of intake swirl flows in the same direction are formed in the combustion chamber by the plurality of intake ports, and the fuel is directed from the center of the ceiling surface of the combustion chamber toward the periphery of the cavity at the center of the piston top surface. In a direct injection compression ignition internal combustion engine that injects, if the intake stratification device is configured by selecting the shape of the combustion chamber and the intake port, and hence the flow characteristics of the intake squish flow and swirl flow, the intake stratification is performed as follows. Can be

In the intake stroke, as illustrated in FIG. 2, at the intake port 3 downstream of the swirl flow, the combustion chamber 1
The swirl flow of the first intake 11 along the peripheral wall at the top of
In the intake port 4 on the upstream side, a swirl flow of the second intake 12 along the peripheral wall is formed below the combustion chamber 1. As illustrated in FIGS. 4 and 5, the state in which the swirl flow of the first intake 11 and the swirl flow of the second intake 12 having different compositions are vertically arranged in the combustion chamber 1 is continued until the middle of the compression stroke. You.

In the latter half of the compression stroke in which the squish flow occurs, the swirl flow on the periphery of the piston top surface is carried by the squish flow into the cavity at the center of the piston top surface, and the swirl velocity along with the reduction of the diameter. Due to the centrifugal force caused by the increase in the flow rate, the fluid flows along the peripheral wall of the cavity without going to the center of the cavity and toward the bottom surface of the cavity. In the cavity, before the squish flow occurs, the second intake air exists in the entire region. However, when the squish flow occurs, as illustrated in FIGS. 6A, 6B, and 6C in the order of lapse of time,
The first intake air 11 flows into the central region, and the second intake air 12 exists only in the peripheral region and the bottom region.

In the vicinity of the end of the compression stroke in which fuel starts to burn, as shown in FIG. 1, the combustion chamber 1 has a substantially flat semispherical surface 13 centered on the center position of the ceiling surface where fuel is injected. The first intake air 11 mainly exists in the region, and the second intake air 12 mainly exists in the region outside the region. At the start of combustion of the fuel, the intakes 11 and 12 having different compositions are stratified in a region inside and outside a substantially hemispherical surface or a substantially flat hemispherical surface centered on a fuel injection position of the combustion chamber.

4) In a direct injection compression ignition internal combustion engine equipped with an exhaust gas recirculation device, during the combustion period, the recirculated exhaust gas is not distributed around the root side of the fuel flow injected from the fuel injection valve. When fresh air is distributed, fresh air is transported to the front end by the fuel flow or the mixed air flow, and oxygen is supplied to the front end of the fuel flow or the cavity valley burning in a state of insufficient oxygen, so that the oxygen concentration is soot. The soot generation is reduced by increasing to the generation suppression value or more. However, at this time, control is performed so that the oxygen concentration does not increase to the NOx (nitrogen oxide) generation value. In addition, when the intake air containing the recirculated exhaust gas is distributed in the squish area of the combustion chamber and the periphery of the cavity where NOx is generated by high-temperature combustion in the lean side region near the stoichiometric air-fuel ratio, the oxygen concentration and the combustion temperature decrease. ,
NOx formation is reduced.

When the load on the internal combustion engine is large and the fuel injection end timing is late, or when the rotation speed of the internal combustion engine is high and the reverse squish flow is strong, the proportion of fuel flowing out of the cavity of the combustion chamber is high. In other words, it burns outside the cavity in an oxygen-deficient state, and burns inside the cavity in an oxygen-excess state. Then, soot is mainly generated outside the cavity, and NOx is mainly generated inside the cavity.

In such a case, the stratification pattern of the combustion chamber is reversed, and the concentration of the intake or recirculated exhaust gas in which the recirculated exhaust gas is mixed in the region inside the approximate hemisphere or the approximately flat hemisphere centered on the fuel injection position. In the region outside the intake air, the intake air in which the recirculation exhaust gas is not mixed or the intake air in which the recirculation exhaust gas concentration is low is arranged. Then, in the squish area outside the cavity of the combustion chamber, the oxygen concentration increases, soot generation is suppressed, and at the same time, soot oxidation is promoted, and soot decreases. However, at this time, the oxygen concentration becomes N
Control is performed so as not to increase to the Ox generation value, thereby preventing NOx from increasing.

That is, it is necessary to change the stratification pattern of the combustion chamber 1 according to the operating conditions of the internal combustion engine. The stratification degree of the combustion chamber 1 also needs to be changed.

In the internal combustion engine illustrated in FIGS.
Depending on the operating conditions, the intake port 3 downstream of the swirl flow
When the amount of recirculated exhaust gas mixed into the first intake air passing through the intake port and the amount of recirculated exhaust gas mixed into the second intake air passing through the upstream intake port 4 are respectively increased or decreased, the stratification pattern of the combustion chamber 1 changes. Is done. A positive stratified pattern in which the concentration of the recirculated exhaust gas is lower in a region inside the substantially flat semi-spherical surface 13 of the combustion chamber 1 than in a region outside the flat hemisphere 13 is obtained. In addition, a reverse stratified pattern in which the concentration of the recirculated exhaust gas is higher in the region inside the substantially flat hemispherical surface 13 of the combustion chamber 1 than in the region outside the same. Furthermore, a homogeneous pattern is obtained in which the recirculation exhaust gas has the same concentration in the region inside the substantially flat hemispherical surface 13 of the combustion chamber 1 and in the region outside thereof.

Further, depending on the operating conditions of the internal combustion engine, the first
When the amount of the recirculated exhaust gas mixed into the intake air and the amount of the recirculated exhaust gas mixed into the second intake air are respectively increased or decreased, the stratification degree of the combustion chamber 1 is changed. The ratio of the recirculation exhaust gas concentration outside the approximately flat hemisphere 13 to the recirculation exhaust gas concentration in the approximately flat hemisphere 13;
Stratification increases or decreases.

[0030]

1) A direct injection type internal combustion engine in which fuel is injected into a combustion chamber or a fuel is injected into a combustion chamber from a center of a ceiling surface facing a piston top surface to a center of a piston top surface cavity. In a direct injection type internal combustion engine that injects fuel toward the periphery, at the start of combustion of fuel near the end of the compression stroke, the inside area of the roughly semispherical or roughly flat hemisphere centering on the fuel injection position of the combustion chamber and the outside area A method for stratifying intake air, comprising arranging intake air having different compositions in a region.

2) In the above-described method for stratifying the intake air, the stratification pattern of the combustion chamber is changed from the inner region to the concentration of a specific component of intake air from the outer region according to the operating conditions of the direct injection type internal combustion engine. Lower stratified pattern, reverse stratified pattern in which the concentration of the specific component of intake is higher in the inner region than in the outer region, or specific component of intake in the inner region and the outer region Characterized in that the density is changed to a uniform pattern in which the density becomes equal.

3) In the above-described method for stratifying the intake air, the degree of stratification of the combustion chamber is determined according to the operating conditions of the direct injection type internal combustion engine.
The ratio of the concentration of the specific component of the intake air in the outer region to the concentration of the specific component of the intake air in the inner region is changed.

4) A plurality of intake swirl flows in the same direction are formed in the combustion chamber by a plurality of intake ports, and fuel is supplied to the combustion chamber from the center of the ceiling facing the piston top surface to the center of the piston top surface. In the direct injection type internal combustion engine that injects fuel toward the peripheral portion, a swirl flow of the first intake air along the peripheral wall is formed at the upper part of the combustion chamber in the intake stroke, and the second intake air flows along the peripheral wall at the lower part of the combustion chamber. The swirl flow of the first intake air and the swirl flow of the second intake air continue in the combustion chamber up and down until the middle of the compression stroke, and the latter half of the compression stroke in which a squish flow occurs In the cavity at the center of the top surface of the piston, the first intake air flows into the central region, the second intake air remains in the peripheral region and the bottom region, and the combustion takes place in the vicinity of the end of the compression stroke in which fuel starts combustion. A first intake in the region inside the outline hemisphere to schematic flattened hemisphere around the fuel injection position,
An intake stratification device, wherein the second intake is mainly arranged in an outer region.

5) In the above-described intake stratification method or intake stratification device, a substantially hemispherical surface or a substantially flat hemispherical surface centered on a fuel injection position of the combustion chamber is a fuel injection position of the combustion chamber in a fuel injection direction. From about 1 to 1.5 times the spray split distance.

[0035]

At the start of the combustion of fuel near the end of the compression stroke, a desired composition is respectively added to the inner and outer regions of the substantially hemispherical surface or the approximately flat hemispherical surface centered on the fuel injection position of the combustion chamber. The intake air can be arranged to control the combustion state of the fuel.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment (see FIGS. 1 to 8)] A direct injection compression ignition internal combustion engine equipped with an intake stratification device according to the present embodiment, as shown in FIG. A large number of injection ports of the fuel injection valve 2 are arranged at the center of the ceiling surface, and two intake ports 3 and 4 and intake valves 5 and 6 are provided on one side of the ceiling surface of the combustion chamber 1.
Two exhaust ports 7 and an exhaust valve 8 are provided on the other side, a cavity 9 having a central axis symmetrical shape is formed at the center of the piston top surface, and a peak portion 10 is provided at the bottom center of the cavity 9.

Near the end of the compression stroke, the fuel injection valve 2 injects fuel from a number of injection ports in a radial direction toward the periphery of the cavity 9.

As shown in FIG. 2, the two intake ports 3 and 4 form swirl flows 11 and 12 of intake air in the same direction in the combustion chamber 1 during the intake stroke. The intake port 3 on the downstream side of the swirl flow has a helical port shape as shown in FIGS. 2 and 3, and the intake air flows out substantially along the ceiling surface of the combustion chamber 1. A strong first intake swirl flow 11 is formed along the peripheral wall at the upper part. The upstream intake port 4 has a tangential port shape,
In order to avoid a collision with the swirl flow 11 of the first intake air, the intake air flows obliquely downward and forms a swirl flow 12 of the second intake air along the peripheral wall of the lower part of the combustion chamber 1 on the top surface side of the piston.

In the intake stratification device of this embodiment, the swirl flow 11 of the first intake air and the second intake air along the peripheral wall of the upper and lower portions of the combustion chamber 1 during the intake stroke, as shown in FIG. Is formed, at the end of the intake stroke, the swirl flow 11 of the first intake air and the swirl flow 12 of the second intake air are vertically stratified in the combustion chamber 1 as shown in FIG. At the end of the intake stroke, the rear end portion of the second intake air 12 that has finally flowed in from the upstream intake port 4 exists above the combustion chamber 1, so that the boundary surface 13 between the first intake air 11 and the second intake air 12. Is not a plane parallel to the top surface of the piston, but an inclined concave and convex curved surface.

The first intake air 11 and the second intake air 12 having different compositions in the combustion chamber 1 mix with each other with the lapse of time, so that components contained only in one intake air are also included in the other intake air. Since the concentration of the component is continuously changed, the surface where the concentration of the component becomes almost an intermediate value is defined as the first surface.
The boundary surface 13 is between the intake air 11 and the second intake air 12.

In the compression stroke, the last part of the second intake air 12 moves to the lower part of the combustion chamber 1, and the mixing of the first intake air 11 and the second intake air 12 progresses. As shown in FIG. 5, an interface 13 between the first intake 11 and the second intake 12
Approaches a plane parallel to the piston top surface. The state in which the first intake swirl flow 11 and the second intake swirl flow 12 are vertically stratified in the combustion chamber 1 continues to the middle of the compression stroke.

In the latter half of the compression stroke in which the squish flow occurs, the swirl flow on the periphery of the piston top surface is carried by the squish flow into the cavity 9 at the center of the piston top surface, and the swirl flow accompanying the diameter reduction is generated. Due to the centrifugal force caused by the increase in the directional speed, the fluid flows along the peripheral wall of the cavity 9 without going to the center of the cavity 9 and goes to the bottom surface of the cavity 9. As shown in FIG. 6A, FIG. 6B, and FIG. 6C, the inside of the cavity 9 is filled with the second intake 12 at the lower part of the combustion chamber 1 and then the first intake at the upper part of the combustion chamber 1 is placed in the central region. 11 and the second intake 12 only in the peripheral area and the bottom area.
Remains.

In the vicinity of the end of the compression stroke in which fuel is injected from the fuel injection valve 2 to start combustion, as shown in FIG.
The first intake air 11 mainly exists in a region inside the roughly flat hemispherical surface 13 centered on the center of the ceiling surface where fuel in the combustion chamber 1 is injected, and the second intake air 12 Exists mainly. At the start of fuel combustion, the intake air 11 and 12 are stratified in a region inside and outside a substantially flat hemispherical surface 13 centered on the fuel injection position of the combustion chamber 1.

When the radius in the fuel injection direction is set to about 1 to 1.5 times the spray split distance, the above roughly flat hemispherical surface 13 forms the intake air 11, 1, 1
2 is stratified.

Near the end of the compression stroke, the first intake air 1
If the swirl flow 1 is too strong, as shown in FIG. 7A, when the first intake air 11 is carried to the bottom surface of the cavity 9 by the squish flow, it becomes an inverse toroidal flow down the peripheral wall of the cavity 9, and The second intake air 12 flowing into the bottom surface of the cavity 9 and present on the peripheral wall and the bottom surface of the cavity 9 is pushed away to the center of the cavity 9.

In this example, since the swirl flow and the squish flow of the intakes 11 and 12 are appropriate, as shown in FIG. 7B, the first intake 11 is located between the crest 10 of the cavity 9 and the peripheral wall. A toroidal flow descends, and the second intake air 12 existing in the middle part is pushed away to the peripheral area and the bottom area of the cavity 9, and the intake air flows into and out of the approximately flat hemispherical surface 13 centering on the fuel injection position of the combustion chamber 1. 11 and 12 are stratified.

The intake stratification device of the present embodiment
The combustion chamber 1 that determines the flow characteristics of the squish flow and swirl flow of the intake air 11 and 12 so that is stratified in this way.
And the shapes of the intake ports 3 and 4 are selected. By these shapes, the degree of stratification of the intake air 11 and 12 and the boundary 13
Can be controlled.

In the above-mentioned shape, the cavity 9 of the combustion chamber 1 is formed.
The shape, the distance between the periphery of the piston top surface and the periphery of the ceiling surface, and the amount of depression of the lower surface of the intake valves 5 and 6 from the ceiling surface are exemplified.

Simulated Experimental Example In the intake stratification device of this embodiment, the first intake air 11 flowing into the combustion chamber 1 from the downstream intake port 3 is supplied with fresh air 100.
%, The second intake air 1 flowing from the upstream intake port 4
2 was set to 50% of fresh air and 50% of recirculated exhaust gas, the distribution of the recirculated exhaust gas concentration in the combustion chamber 1 at the end of the compression stroke was obtained by numerical calculation.

FIG. 8 shows the result. FIG. 8 (b) is a central longitudinal section of the combustion chamber 1 passing between the downstream and upstream intake ports 3 and 4, and FIG. The distribution of the recirculated exhaust gas concentration (EGR rate) in the central longitudinal section perpendicular to the graph is shown by brightness.

As is apparent from these figures, at the end of the compression stroke, the contour surface of the recirculated exhaust gas concentration distribution of the combustion chamber 1 appears in a substantially flat hemispherical shape centering on the fuel injection position, and at the fuel injection position. The recirculation exhaust gas concentration becomes thinner as it approaches, and the distribution of the recirculation exhaust gas concentration becomes almost axially symmetric. The intake air of the combustion chamber 1 indicates that the intake air 11 and the intake air 12 are stratified inside and outside a substantially flat hemispherical surface centered on the fuel injection position.

[Second example (see FIG. 9)] In the intake stratification device of the first example, in order to increase the degree of stratification of intake air, the intake stratification device of the first example employs intake ports 3 and 4 on the downstream and upstream sides. Valve 5,
The opening period of 6 is shifted.

As shown in FIG. 9, at the downstream intake port 3 through which the first intake air 11 flows into the upper part of the combustion chamber 1, the intake valve 5 is opened at a later time and closed at a later time. Upstream intake port 4 for allowing second intake air 12 to flow into the lower part of combustion chamber 1
Then, the intake valve 6 is opened early and closed early.

In the first half of the intake stroke, only the intake valve 6 of the intake port 4 on the upstream side is opened, and only the second intake 12 disposed below the combustion chamber 1 flows into the combustion chamber 1. In the middle stage of the intake stroke, the intake valves 5, 6 of both intake ports 3, 4 are opened, and the first intake 11 and the second intake 12 flow into the combustion chamber 1. In the latter half of the intake stroke, only the intake valve 5 of the downstream intake port 3 opens, and only the first intake 11 arranged above the combustion chamber 1 flows into the combustion chamber 1.

At the end of the intake stroke, the first intake port 11 and the second intake port 12 are at the end of the intake stroke, as compared with the first example in which the opening periods of the intake valves 5 and 6 at the downstream and upstream intake ports 3 and 4 match. Is more or less stratified up and down, and at the end of the compression stroke, the degree of stratification of the intake air 11 and 12 inside and outside the roughly flat hemispherical surface 13 centered on the fuel injection position is increased.

The other points are the same as in the first example.

[Third Example (See FIG. 10)] In the intake stratification device of the first example, in order to increase the degree of stratification of the intake air in the first example, the second intake air is applied only from one side of the intake port 4 on the upstream side. 12 flows into the combustion chamber 1.

At the intake port 4 on the upstream side, the intake air flows obliquely downward and collides obliquely with the peripheral wall of the combustion chamber 1.
The swirl flows along the peripheral wall at the lower part of the combustion chamber 1. The intake air flowing out of the tangential port-shaped intake port 4 on the peripheral wall side of the combustion chamber 1 has a shorter distance until it collides with the peripheral wall of the combustion chamber 1 than the intake air flowing out of the central side part of the combustion chamber 1, and the combustion It easily flows into the lower part of the chamber 1.

Therefore, the intake port 4 on the upstream side is
As shown in the figure, the peripheral wall side portion and the central side portion of the combustion chamber 1
A partition wall 21 for dividing is provided, and the combustion chamber 1 of the intake port 4 is provided.
The second intake air 12 having a high concentration of a specific component such as the recirculated exhaust gas flows into the peripheral wall side portion, and the second intake air 12 flows into the lower portion of the combustion chamber 1 from the combustion chamber 1 peripheral wall side portion of the intake port 4. The first intake air 11 flows into the central portion of the combustion chamber 1 of the intake port 4 in the same manner as the intake port 3 on the upstream side, and the first intake air 11 flows into the combustion chamber 1 from the central portion of the combustion port 1 of the intake port 4. Let it.

The second intake air 12 flowing into the combustion chamber 1 from the portion of the intake port 4 on the peripheral wall side of the combustion chamber 1 has a narrow air flow,
Mixing with the first intake air 11 becomes difficult.

In comparison with the first example in which the second intake air 12 flows into the combustion chamber 1 from the entire intake port 4 on the upstream side,
At the end of the intake stroke, the degree of stratification of the first intake 11 and the second intake 12 in the vertical direction increases, and at the end of the compression stroke, the intakes 11 and 12 enter and exit the roughly flat hemispherical surface 13 centered on the fuel injection position. The degree of stratification increases.

The other points are the same as in the first example.

[Fourth Example] The intake stratification apparatus of the present example
In the example, in order to increase the degree of stratification of the intake air, a subport through which the intake air is easily introduced is provided at a lower portion or an upper portion of the combustion chamber 1.

In the third example, an auxiliary intake port similar to that of the intake port 4 on the peripheral wall side of the combustion chamber 1 of the intake port 4 where the intake air easily flows into the lower part of the combustion chamber 1 is provided. The second intake air 12 having a high component concentration is caused to flow.

[Fifth Example (see FIG. 11)] The intake stratification device of the present example is the same as that of the first example, except that the stratification pattern and stratification degree of the intake air in the combustion chamber 1 are determined according to the operating conditions of the internal combustion engine. change.

In the internal combustion engine of the first example, the first intake passage 23 connected to the intake port 3 on the downstream side of the swirl flow
As shown in FIG. 11, the first flow control valve 24
A second flow control valve 27 is connected to a second intake passage 26 connected to the exhaust gas recirculation passage 25 and to the intake port 4 on the upstream side.
Is connected to the second exhaust gas recirculation passage 28 via the second exhaust gas recirculation passage. A device 29 is provided for controlling the opening of the first flow control valve 24 and the opening of the second flow control valve 27 according to the operating conditions of the internal combustion engine.

When the opening degree of the first flow control valve 24 and the opening degree of the second flow control valve 27 are controlled in accordance with the operating conditions of the internal combustion engine, the opening degree of the first flow control valve 24 is mixed with the first intake air passing through the downstream intake port 3. The amount of recirculated exhaust gas and the amount of recirculated exhaust gas mixed into the second intake air passing through the upstream intake port 4 increase and decrease, respectively, and the stratification pattern of the combustion chamber 1 is changed. A positive stratified pattern in which the concentration of the recirculated exhaust gas is lower in a region inside the substantially flat semi-spherical surface 13 of the combustion chamber 1 than in a region outside the flat hemisphere 13 is obtained. In addition, a reverse stratified pattern in which the concentration of the recirculated exhaust gas is higher in the region inside the substantially flat hemispherical surface 13 of the combustion chamber 1 than in the region outside the same. Furthermore, a homogeneous pattern is obtained in which the recirculation exhaust gas has the same concentration in the region inside the substantially flat hemispherical surface 13 of the combustion chamber 1 and in the region outside thereof.

Further, depending on the operating conditions of the internal combustion engine, the first
When the opening of the flow control valve 24 and the opening of the second flow control valve 27 are controlled, the stratification of the combustion chamber 1 is changed. The ratio of the recirculation exhaust gas concentration outside the roughly flat hemisphere 13 to the recirculation exhaust gas concentration in the roughly flat hemisphere 13, specifically, the roughly flat hemisphere with respect to the recirculation exhaust gas concentration at the fuel injection position inside the roughly flat hemisphere 13. The ratio of the recirculated exhaust gas concentration and the degree of stratification in the peripheral region around the bottom of the cavity 13 increase or decrease.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a direct injection compression ignition internal combustion engine equipped with an intake stratification device in a first example of an embodiment of the present invention.

FIG. 2 is a schematic perspective view of a combustion chamber in the middle of an intake stroke in the internal combustion engine.

FIG. 3 is a schematic plan view of a combustion chamber in the internal combustion engine.

FIG. 4 is a schematic perspective view of a combustion chamber at the end of an intake stroke in the internal combustion engine.

FIG. 5 is a schematic perspective view of a combustion chamber in the middle of a compression stroke in the internal combustion engine.

FIG. 6 is a schematic longitudinal sectional view of a combustion chamber near the end of a compression stroke in the internal combustion engine, showing a flow state of intake air.

FIG. 7 is a schematic vertical sectional view of a combustion chamber at the end of a compression stroke in an internal combustion engine, showing a flow state of intake air.

FIG. 8 is a view showing a stratified state of intake air at the end of a compression stroke in a simulation test example of the internal combustion engine.

FIG. 9 is an intake valve lift diagram of a direct injection compression ignition internal combustion engine equipped with an intake stratification device according to a second example of the embodiment.

FIG. 10 is a schematic plan view of a combustion chamber of a direct injection compression ignition internal combustion engine equipped with an intake stratification device in a third example.

FIG. 11 is a schematic view of an intake passage portion of a direct injection compression ignition internal combustion engine equipped with an intake stratification device in a fifth example.

[Explanation of symbols]

 Reference Signs List 1 combustion chamber 2 fuel injection valve 3 intake port on the downstream side of swirl flow 4 intake port on the upstream side of swirl flow 5 intake valve on the downstream side of swirl flow 6 intake valve on the upstream side of swirl flow 9 cavity 11 first intake 12 Second intake 13 Boundary surface between first intake and second intake, roughly flat hemisphere

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02B 31/02 F02B 31/02 L F02D 13/02 F02D 13/02 H 41/04 370 41/04 370 F02F 3/26 F02F 3/26 C F02M 25/07 570 F02M 25/07 570A (72) Inventor Kazuhisa Inagaki 41-cho, Yokomichi, Oku-cho, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory, Inc. (72) Inventor Yoshihiro Hotta 41 Toyota Chuo R & D Co., Ltd., Aichi-cho, Nagakute-cho, Aichi-gun, Toyota-Chuo R & D Co., Ltd.

Claims (10)

[Claims] In a direct injection type internal combustion engine for injecting fuel into a combustion chamber, at the start of combustion of fuel near the end of a compression stroke, a substantially semispherical surface or a substantially flat semispherical surface centered on a fuel injection position of the combustion chamber. Characterized by arranging intake air having different compositions in a region outside and a region outside. 2. A stratified pattern of a combustion chamber according to operating conditions of a direct injection type internal combustion engine, wherein a concentration of a specific component of intake air is lower in the inner region than in the outer region. In a reverse stratification pattern in which the concentration of the specific component of the intake air is higher than the outer region in the inner region, or in a homogeneous pattern in which the concentration of the specific component of the intake air is equal in the inner region and the outer region. The method for stratifying intake air according to claim 1, wherein the method is changed. 3. The method according to claim 1, wherein a ratio of a concentration of the specific component of the intake air in the outer region to a concentration of the specific component of the intake air in the inner region is changed according to an operating condition of the direct injection internal combustion engine. The method for stratifying intake air according to claim 1 or 2, wherein 4. A direct injection type internal combustion engine is characterized in that fuel is injected into a combustion chamber from a central portion of a ceiling surface facing a piston top surface toward a peripheral portion of a cavity at a central portion of the piston top surface. The method for stratifying intake air according to claim 1, 2 or 3. 5. A substantially hemispherical surface or a substantially flat hemispherical surface centered on a fuel injection position of the combustion chamber is separated from the fuel injection position of the combustion chamber by about 1 to 1.5 times the spray split distance in the fuel injection direction. The method for stratifying intake air according to claim 1, wherein: 6. The method for stratifying intake air according to claim 1, wherein the direct injection internal combustion engine is a compression ignition internal combustion engine. 7. A plurality of intake swirl flows in the combustion chamber are formed in the combustion chamber by a plurality of intake ports, and fuel is supplied to the combustion chamber from a center of a ceiling surface facing the piston top surface to a center of the piston top surface. A direct injection internal combustion engine that injects fuel toward a peripheral portion of a combustion chamber, comprising:
A swirl flow of the intake air is formed, and a swirl flow of the second intake air is formed at a lower portion of the combustion chamber along a peripheral wall thereof. The swirl flow of the first intake air and the swirl flow of the second intake air in the combustion chamber until the middle of the compression stroke. In the latter half of the compression stroke in which squish flow is generated, the first intake air flows into the central region in the cavity at the center of the piston top surface, and the second intake air flows into the peripheral region and the bottom region. In the vicinity of the end of the compression stroke in which fuel starts burning, the first intake air is supplied to an area inside a substantially hemispherical surface or a substantially flat hemispherical surface around the fuel injection position of the combustion chamber, and the first intake air is supplied to an outer region. An intake stratification device, wherein two intakes are mainly arranged. 8. A substantially hemispherical surface or a substantially flat hemispherical surface centered on a fuel injection position of the combustion chamber is separated from the fuel injection position of the combustion chamber by about 1 to 1.5 times the spray split distance in the fuel injection direction. The intake stratification device according to claim 7, wherein: 9. The intake stratification device according to claim 7, wherein the direct injection internal combustion engine is a compression ignition internal combustion engine. 10. An intake port which forms a swirl flow of a first intake air in an upper part of a combustion chamber and a suction port which forms a swirl flow of a second intake air in a lower part of a combustion chamber, in which an opening period of an intake valve is shifted. In the first half of the stroke, only the intake valve of the latter intake port opens and only the second intake flows into the combustion chamber. In the middle of the intake stroke, the intake valves of both intake ports open and the first intake And the second intake air flows into the combustion chamber, and in the latter half of the intake stroke, only the intake valve of the former intake port is opened and only the first intake air flows into the combustion chamber. 10. The intake stratification device according to 7, 8, or 9.