JP2699722B2 - Stratified combustion internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of supplying an air-fuel mixture and air to a combustion chamber, respectively, and forming the air-fuel mixture in a stratified swirling flow in the combustion chamber. The present invention relates to a stratified combustion internal combustion engine that burns fuel.

[0002]

2. Description of the Related Art According to this type of stratified charge combustion type internal combustion engine, a rich mixture and air are supplied to a combustion chamber, and the rich mixture is ignited to complete combustion of the mixture. I try to make it. Therefore, in this type of internal combustion engine, even if the overall air-fuel ratio of the above-described air-fuel mixture and the air is higher than the stoichiometric air-fuel ratio, that is, even if the overall air-fuel mixture is lean, Combustion becomes possible. Therefore, not only can the fuel efficiency of the engine be improved, but also harmful emissions such as CO and NOx contained in the exhaust gas of the engine can be reduced, and knocking of the engine can be effectively prevented.

[0003] In a stratified combustion internal combustion engine, as described above, the combustion of an air-fuel mixture in a combustion chamber is performed in a unique process. The purpose is to generate a rich air-fuel mixture flow in the vicinity of the ignition plug in the combustion chamber, and secondly, to activate the air-fuel mixture flow in the combustion chamber. That is,
The main aim is to obtain stable combustion by increasing the combustion rate of the air-fuel mixture after ignition and to increase the combustion efficiency.

Therefore, in a conventional stratified combustion internal combustion engine, a rich mixture layer is formed on the spark plug side in the combustion chamber of one cylinder, whereas air, that is, on the piston side, is formed. Various means have been employed to create a lean mixture.

As one of the means, there is, for example, an internal combustion engine having two intake ports on one side of a combustion chamber per cylinder, which will be described below as an example.

[0006] As one example of such an internal combustion engine, an internal combustion engine described in Japanese Patent Application Laid-Open No. 3-23314 is known. In this internal combustion engine, a fuel injection valve is installed on one of the two intake ports, and a spark plug is positioned corresponding to the intake port on the side where the fuel is injected. Thus, the ignition was attempted with an appropriate mixture, and the overall combustion chamber was intended to be a lean mixture.

[0007]

There is no problem with the above-described internal combustion engine as long as it has a three-valve structure in which only one exhaust port is formed, but the performance of the internal combustion engine is further improved. Therefore, if a four-valve structure having two exhaust ports is used, it is difficult to properly arrange the ignition plug.

That is, in the case of the four-valve structure, a space is inevitably left only in the central part of the combustion chamber, so that the spark plug must be installed in the central part of the combustion chamber.
As a result, a rich air-fuel mixture flow cannot be created around the ignition plug, and it is not possible to reduce emissions such as CO and NOx and prevent knocking of the engine.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a combustion chamber having a rich air-fuel mixture layer and an air or lean air-fuel mixture layer with a simple structure. To provide a stratified combustion internal combustion engine that can perform fuel combustion in the combustion chamber satisfactorily, and can optimally supply the air-fuel mixture to the combustion chamber. is there.

[0010]

According to a first aspect of the present invention, there is provided a stratified combustion internal combustion engine having a combustion chamber defined by a cylinder bore and a piston fitted to the cylinder bore, and having a passage cross section changed according to an operation state of the engine. At least two intake ports that always open to the combustion chamber and always generate swirling flows in which air introduced into the combustion chamber in the intake step flows along the axial direction of the cylinder bore;
An ignition device which is located at the upper central portion of the combustion chamber and ignites an air-fuel mixture taken in from the intake port; and determines an injection direction so that fuel is injected toward the ignition device, and determines an injection direction to the intake port. Fuel injection means for producing a fuel-air mixture by the injected fuel, which is provided in the internal passage connected to the fuel cell.
At least when the engine is under a low load.
A rich mixture layer is formed on the sides and in other areas
By forming a layer of air or a lean mixture
And is characterized in the this <br/> be greater than the stoichiometric air-fuel ratio of the entire serial combustion chamber.

A stratified combustion internal combustion engine according to a second aspect is characterized in that the fuel injection means is installed in all the intake ports.

According to a third aspect of the present invention, there is provided a stratified combustion internal combustion engine, wherein an internal passage leading to an intake port has a substantially inverted triangular cross section.

[0013]

In the intake process, air flows from each intake port into the combustion chamber defined by the cylinder bore and the piston regardless of the operation state of the engine, and the swirling flow along the axial direction of the cylinder bore is reduced to the number of intake ports. Always generated according to
At this time, the flow of the air-fuel mixture is created in the combustion chamber by the fuel injection means injecting the fuel , and at least the engine
At low load, a rich mixture layer forms around the igniter
Air and lean mixing in other areas
A layer of gas is formed, and the air-fuel ratio of the entire combustion chamber is equal to the stoichiometric air-fuel ratio.
Also increase.

At this time, since the fuel injection direction is determined so that the fuel is injected toward the ignition device, a rich air-fuel mixture flow is created around the ignition device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A stratified combustion internal combustion engine according to a first embodiment of the present invention is shown in FIGS. 1 to 6, and this embodiment will be described with reference to these drawings.

As shown in FIG. 1, the engine 20 is an in-line four-cylinder gasoline engine. Where engine 2
Since the structure of each cylinder at 0 is the same, only one cylinder will be described below.

One cylinder has a cylinder bore 24 formed in a cylinder block 22, and a piston 26 is fitted in the cylinder bore 24 in a reciprocating manner. Here, as is clear from FIG. 1, the cylinder bores 24 of each cylinder are arranged without rows. As shown in FIG. 2, a cylinder head 28 is attached to the cylinder block 24 via a gasket (not shown) and covering the opening of the cylinder bore 24. A combustion chamber 30 is formed between 26 and the cylinder head 28.

Cylinder head 28 forming combustion chamber 30
A so-called pent roof 34 is formed at the center of the inner wall surface of the, and the ridge of the pent roof 34 is positioned on a vertical plane X (see FIG. 1) including the axis of each cylinder bore 24.

Two intake ports 36 and 38 are respectively opened on one side roof of the pent roof 34 in the combustion chamber 30. These intake ports 36 and 38 have
The introduction passages 40 and 42 are respectively connected. The introduction passages 40 and 42 include an internal passage 44 formed in the cylinder head 28 and communicating with a corresponding intake port, and a branch pipe 48 of an intake manifold 46 connected to the internal passage 44. The intake manifold 46 has a surge tank 50 to which a branch pipe line 48 is continuous. As shown in FIG. 1, the surge tank 50 has a row of cylinder bores 24 of each cylinder, It extends along X. At one end of the surge tank 50, an inlet opening 52 is formed.
An intake pipe (not shown) is connected via the throttle body 54. A throttle valve 56 is disposed in the throttle body 54, and the throttle valve 56
It is activated by depressing the accelerator pedal.

Further, poppet type intake valves 58 are disposed at the intake ports 36 and 38, respectively. These intake valves 58 open and close the corresponding intake ports by a mechanism not shown. FIG. 2 shows only the intake valve 58 paired with the intake port 38 in an open state.

The pent roof 34 in the combustion chamber 30
An intake port 60 is formed on the other one side roof, and an exhaust passage 62 is connected to the exhaust port 60. The exhaust port 60 is opened and closed by a poppet type exhaust valve 64. Here, the number of the exhaust valves 64 is two in accordance with the number of the intake valves 58.

Further, at least the straight portion of the internal passage 44 in the introduction passages 40 and 42 has an inverted triangular cross section as shown in FIG.
Moreover, the flow passage cross-sectional area has the same size along the axis of the straight portion. In this embodiment, one of the introduction passages 40 and 42 is provided with a fuel injection valve 66 as a fuel injection means in the introduction passage 42 located on the right side in FIG. This fuel injection valve 66 is
As shown in FIG. 2, the injection nozzle 68 is positioned in a straight portion of the internal passage 44 so as to face the intake port 38.

The fuel injection valve 66 is connected to a fuel injection pump. The fuel injection valve 66 is opened when high-pressure fuel is supplied from the fuel injection pump. Inject. Here, the fuel injected from the injection nozzle 68 forms a conical shape and travels toward the intake port 38, that is, the combustion chamber 30.

Therefore, since the fuel injection valve 66 is provided in the introduction passage 42 as described above, the introduction passage 42
By injecting fuel from the fuel injection valve 66 into the air to be supplied to the combustion chamber 30 through the, a mixture of air and fuel can be created.

An ignition plug 70 serving as an ignition device is provided on the cylinder head 28 so as to face the combustion chamber 30.
The ignition plug 70 is located at the upper central portion of the combustion chamber 30 as is apparent from FIGS. 1 and 2.

The same reference numerals in FIG. 1 denote the same parts of the other cylinders as those described above, and a description thereof will be omitted.

Next, the operation of the above-described internal combustion engine will be described. Since the operation of each cylinder is the same, the operation will be described focusing on one cylinder.

When one cylinder is in the intake stroke, the piston 26 moves in the direction of increasing the volume of the combustion chamber 30, that is,
It is moved downward as seen in FIG. Such a piston 26
As a result, the air and the air-fuel mixture are respectively introduced into the combustion chamber 30 from the intake ports 36 and 38 which are opened by the intake valve 58. That is, in the case of this embodiment, since the fuel injection valve 66 is provided in one of the introduction passages 42, the air flowing through the introduction passage 42
By injecting fuel from the fuel injection valve 66, the air-fuel mixture is supplied from the intake port 38 toward the combustion chamber 30, whereas only the air is supplied from the intake port 36 to the combustion chamber 30. .

The straight portion of the internal passage 44 in the introduction passages 40 and 42 has an inverted triangular cross section and is inclined at a predetermined inclination angle α with respect to the lateral surface Y. 38 are arranged symmetrically with respect to a plane orthogonal to the vertical plane X and including the axis of the cylinder bore 24, so that with the lowering of the piston 26,
It is introduced into the combustion chamber 30 from the intake ports 36 and 38, that is,
Most of the sucked air and air-fuel mixture
4 is guided to the inner wall of the swirl flow F as shown in FIG.
a and Fm.

Here, these swirl flows Fa and Fm are:
An ordered, barrel swirl flow that flows along the axis of the cylinder bore 24 and is layered from one another in the direction of the ridges of the pent roof 34. Therefore, in the internal combustion engine 20 of the present invention, during the intake process, the air and the air-fuel mixture can be simultaneously introduced from the two intake ports 36 and 38 into each combustion chamber 30 at the same time. Over time, it is possible to increase the volumetric efficiency.

Since the position of the ignition plug 70 is located at the center of the engine 20 due to the necessity of the four-valve engine 20, it has been considered to change the fuel injection direction of the fuel injection valve 66. The results of this study are shown in FIGS. 5 and 6 and are described below.

Here, as shown in FIG. 6, the test items are a combustion variation rate (SIGMA PMI), an average effective pressure (PMI), and a NOx emission amount, and the test conditions are as shown in FIG. In addition, the injection direction is parallel to the conventional internal passage 44, the injection direction is indicated by a curve B (indicated by a curve B), and the injection direction is inclined at an angle of 5 ° to the spark plug direction (indicated by a curve A in the drawing); Three conditions were set: one inclined at an angle of 5 ° in the opposite direction to the ignition plug (indicated by curve C in the figure).

As shown in the figure, it is confirmed that the curve A shows stable combustion on the lean side with respect to the curve A. In addition, the average effective pressure also shows a wide range of values from the rich side to the lean side of the curve A, confirming that high output is exhibited and fuel economy is good. Further, the emission amount of NOx is also represented by the curve A
Is particularly low on the lean side.

As described above, even in an internal combustion engine having a four-valve structure and in which ignition is performed at the center, the angle of the fuel injection direction by the fuel injection valve 66 is changed as shown in FIG.
By setting the angle toward the zero side, it is possible to obtain high performance as an engine while achieving stratified combustion.

A second embodiment of the present invention is shown in FIGS. 2, 3 and 7, and this embodiment will be described with reference to these figures. The same members as those described in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIG. 7, a pair of intake ports 3
Fuel injection valves 66 and 67 are installed in the internal passages 44 leading to the fuel injection valves 6 and 38, respectively. With such a structure, the spark plug 7
The concentration of the air-fuel mixture around 0 is further increased, and an effect equivalent to or greater than that of the first embodiment can be expected.

[0037]

According to the stratified combustion internal combustion engine of the present invention, at least two intake ports are always provided in the combustion chamber according to the number of the intake ports without changing the passage cross section in accordance with the operating state of the engine. In addition to generating a swirl flow, the fuel injection means is installed so that fuel is injected into the ignition device, and at least when the engine is under low load
Creates a rich mixture layer around the igniter
A layer of air or a lean mixture in other areas
And make the air-fuel ratio of the entire combustion chamber larger than the stoichiometric air-fuel ratio.
As a result, even if the mixture in the entire combustion chamber is lean, fuel is supplied to the periphery of the ignition device that requires a truly rich mixture flow.

Therefore, even if the mixture is lean as a whole, it can be stably burned, and both fuel consumption and CO emissions can be reduced.

[Brief description of the drawings]

FIG. 1 is a partially cutaway view of an entire internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing one cylinder of the internal combustion engine according to the embodiment of the present invention.

FIG. 3 is a sectional view taken along the line DD in FIG.

FIG. 4 is a perspective view schematically showing the cylinder of FIG. 2;

5A and 5B are diagrams showing test conditions of the internal combustion engine, wherein FIG. 5A is a plan view and FIG. 5B is a side view.

FIG. 6 is a diagram showing a graph of a test result.

FIG. 7 is a partially cutaway view of the entire internal combustion engine according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 20 engine 22 cylinder block 24 cylinder bore 26 piston 30 combustion chamber 36, 38 intake port 40, 42 introduction passage 44 internal passage 60 exhaust port 66, 67 fuel injection valve 70 spark plug

Claims (3)

(57) [Claims] A combustion chamber defined by a cylinder bore and a piston fitted into the cylinder bore; and a combustion chamber which opens into the combustion chamber without changing a passage cross section in accordance with an operation state of an engine, and which performs combustion in an intake process. At least two intake ports each of which constantly generates a swirling flow in which air introduced into the chamber flows along the axial direction of the cylinder bore; and mixing located at an upper central portion of the combustion chamber and sucked from the intake port. An igniter for igniting air, and a fuel injection which is installed in an internal passage leading to the intake port by deciding an injection direction so as to inject fuel toward the igniter and produces a mixture by the injected fuel. possess the means,
At least around the ignition device when the engine is under low load
Form a rich mixture layer and air in other areas
Or by forming a lean mixture layer
A stratified combustion internal combustion engine characterized in that the air-fuel ratio of the entire firing chamber is made larger than the stoichiometric air-fuel ratio . 2. The stratified combustion internal combustion engine according to claim 1, wherein the fuel injection means is provided in all intake ports. 3. A stratified combustion internal combustion engine according to claim 1, wherein the cross section of the internal passage leading to the intake port has a substantially inverted triangular shape.