JP4379370B2 - Combustion chamber structure of internal combustion engine - Google Patents

Description

  The present invention relates to a combustion chamber structure of an internal combustion engine suitable for use in an in-cylinder injection (or direct injection) internal combustion engine.

  Conventionally, an in-cylinder injection type (direct injection type) gasoline engine capable of stratified lean combustion operation has been put into practical use. Generally, in such an in-cylinder injection type gasoline engine, a recess is formed on the upper surface of the piston, and when the piston is located near the top dead center, fuel can be injected toward the recess on the upper surface of the piston. In addition, an injector is disposed, and a spark plug is disposed so that the tip of the spark plug is positioned in the recess on the upper surface of the piston.

  As a result, the fuel injected into the combustion chamber can have a relatively rich air-fuel ratio around the spark plug, and on the other hand, a super-lean atmosphere is formed at a location away from the spark plug, thereby burning the fuel. By forming a stratified lean state in the chamber and igniting the spark plug in this state, a lean air-fuel ratio is formed in the entire combustion chamber, but it is possible to operate stably.

On the other hand, in addition to the above-described general in-cylinder injection type engine, an in-cylinder injection type gasoline engine (hereinafter referred to as “spray guide direct injection engine”) called a spray guide system has been developed.
This spray guide direct injection engine is an in-cylinder injection type gasoline engine that can form a layered lean state in a combustion chamber by directly injecting fuel toward an ignition plug. Patent Document 1 discloses the technique.
Japanese Patent Laid-Open No. 10-54246

  However, as described above, the spray guide direct injection engine is different from the general port injection type engine and the general in-cylinder injection type engine, so that the fuel is directly injected into the spark plug. When the atomization of the fuel is not sufficient, the dropletized fuel adheres to the spark plug to become carbon, and the combustion stability is impaired. In particular, when the injector and the spark plug are close to each other, the fuel vaporization time cannot be obtained, and the combustion stability tends to deteriorate.

Further, in order to improve the combustion stability in the spray guide direct injection engine, it is necessary to tune the spark plug and the fuel injection device comprehensively. This point will be described with reference to FIGS.
FIG. 8 is a schematic cross-sectional view mainly showing a combustion chamber 101 of a general spray guide type direct injection engine (hereinafter referred to as “spray guide direct injection engine”) 100.

The combustion chamber 101 is formed by being surrounded by a lower surface 102A of the cylinder head 102, a cylinder liner 104 of the cylinder block 103, and an upper surface 105A of the piston 105.
The cylinder head 102 is provided with an intake valve 107 that opens and closes an intake port 106 and an exhaust valve 109 that opens and closes an exhaust port 108. The cylinder head 102 further includes an intake port 106 and an exhaust port 108. An ignition plug 110 and an injector 111 are provided so as to protrude into the combustion chamber 101 between them.

The injector 111 injects gasoline toward the lower end 110a of the spark plug 110. The injector 111 forms an atmosphere close to stoichiometric around the spark plug 110 and is lean at a location away from the spark plug 110. By forming this atmosphere, a layered lean atmosphere can be formed in the combustion chamber 101.
A center electrode 112 and a side electrode 113 are provided on the lower end 110 a side of the spark plug 110, and a spark is generated between the center electrode 112 and the side electrode 113.

However, it is difficult to always keep the position of the side electrode 113 with respect to the direction of fuel injection from the injector 111, which causes a problem in that the combustion stability varies.
That is, the spark plug 110 has a male screw portion 110 b, and the male screw portion 110 b is screwed into a female screw portion 102 b formed in the cylinder head 102, whereby the spark plug 110 is fixed to the cylinder head 102. However, when the screwing of the male screw portion 110b and the female screw portion 102b is completed, the tip of the side electrode 113 (that is, one end of the spark plug 110) 110a is arranged in any direction. Whether it is provided depends on the male screw part 110 b of the spark plug 110 and the female screw part 102 b of the cylinder head 102.

  This point will be described in more detail. For example, as shown in FIG. 9, when the tip 110a of the side electrode 113 is disposed so as to be opposite to the fuel injection direction from the injector 111, FIG. As shown in FIG. 11, when the tip 110a of the side electrode 113 is disposed so as to be orthogonal to the fuel injection direction, as shown in FIG. 11, the tip 110a of the side electrode 113 is the same as the fuel injection direction. The combustion characteristics are different from the case where they are arranged as described above. This difference in combustion characteristics is shown in FIG. The description will be made assuming that the attachment angle of the spark plug 110 in the case shown in FIG. 9 is a reference (0 degree), the case shown in FIG. 10 is 90 degrees or 270 degrees, and the case shown in FIG. 11 is 180 degrees.

In FIG. 12, the region indicated by reference numeral A ₁₀₁ indicates a combination of fuel injection timing and ignition timing at which stable combustion is established when the spark plug 107 mounting angle is 0 degrees as shown in FIG.
Further, a region denoted by reference numeral A ₁₀₂ indicates a fuel injection timing at which combustion is stabilized when the attachment angle of the spark plug 107 is 90 degrees or 270 degrees as shown in FIG.

The region indicated by reference symbol A ₁₀₃ indicates the fuel injection timing and ignition timing at which combustion is stabilized when the spark plug attachment angle is 180 degrees as shown in FIG.
That is, in consideration of the fact that the mounting angle of the spark plug 110 is not constant, in order to ensure the combustion stability of the engine 100, the region A _{101 to} A ₁₀₃ are within the region A ₁₀₀ where they overlap. This means that the fuel injection timing and ignition timing can only be controlled.

It is not realistic to control the fuel injection timing and the ignition timing only within such a narrow area A ₁₀₀ , and actually, the engine is operated outside such a narrow area A _100. There is a case where it must be done, and there is a problem that combustion stability has been impaired.
The present invention has been devised in view of such problems, and an object of the present invention is to provide a combustion chamber structure of a direct injection internal combustion engine that can prevent a situation in which combustion stability is impaired.

In order to achieve the above object, a combustion chamber structure of a direct injection internal combustion engine according to the present invention (Claim 1) includes a central electrode on one end side projecting toward the combustion chamber of the direct injection internal combustion engine. A combustion chamber structure of a cylinder injection type internal combustion engine having a spark plug and a fuel injection valve that injects fuel toward the one end side of the spark plug, on the one end side of the spark plug An injection target portion which is formed between the central electrode and the fuel injection valve and receives fuel injected from the fuel injection valve, and the central electrode except for a tip portion of the central electrode A central electrode insulating portion that covers the inner electrode, and a communication portion that is formed in the injected portion and that communicates the central electrode side and the fuel injection valve side, and the communication portion is located at a position excluding the tip portion of the central electrode and characterized in that it is formed in the position opposite to the central electrode insulating portion comprising a To have.

The combustion chamber structure for a direct injection type internal combustion engine of the present invention according to claim 2, in the context of claim 1, wherein the該被injector is formed surrounding the entire periphery of said center electrode It is characterized by .

Further, the combustion chamber structure of the direct injection internal combustion engine of the present invention according to claim 3 is the content of claim 1 or 2 , wherein the ignition plug is formed on the outer periphery of the side surface of the spark plug with respect to the combustion chamber. A case portion for fixing the case is provided, and the injected portion is formed integrally with the case portion.
The combustion chamber structure for a direct injection type internal combustion engine of the present invention described in claim 4, in the context according to what Re one of claim 1 to 3 that the communicating portion is provided with a plurality of It is a feature.

The combustion chamber structure for a direct injection type internal combustion engine of the present invention of claim 5, wherein, in the content according to what Re one of claims 1-4, the side poles located opposite the said center electrode Is provided in the to-be-injected part.

According to the cylinder injection type internal combustion engine of the present invention, the fuel injected from the fuel injection valve is received by the injected portion formed on one end side of the spark plug, so that the fuel that is not sufficiently atomized is directly It is possible to prevent contact with the center electrode and to prevent a situation in which combustion stability is impaired .
In addition, even if the insulator part (insulating part) is contaminated with carbon, the flame generated in the combustion chamber reaches the insulator part through the communicating part, so that the attached carbon can be burned out. Thereby, the fall of the spark performance of a spark plug can be prevented and the fall of combustion stability can be prevented.

In addition, although the injected portion formed close to the center electrode is hot, the fuel is received by the high-temperature injected portion, so that it is sufficiently atomized as well as the atomized fuel. Even fuel that has not been vaporized can be vaporized, and furthermore, since this vaporized fuel can reach the vicinity of the center electrode through the communicating portion, it is possible to prevent a situation in which combustion stability is impaired .
Further, the central electrode is covered with the central electrode insulating portion except for the front end portion thereof, and a communicating portion is formed at a position facing the central electrode insulating portion, and the position does not include the front end portion of the central electrode. Therefore, even if fuel that is not sufficiently atomized passes through the communicating portion, this fuel can be prevented from reaching the center electrode (claim 1).
Further, since the injected portion is formed so as to surround the entire circumference of the center electrode, stable combustion can be ensured regardless of the attachment angle of the spark plug.

Also, by forming integrally with the casing part to be injection portion, it is possible to enhance the productivity of the spark plug (claim 3).

Further, by providing a plurality of communication portions, the fuel vaporized by being received by the injected portion can easily reach the vicinity of the center electrode .
Further, by providing the side electrode in the injected portion, the productivity of the spark plug is improved and the side electrode does not hinder the communicating portion (Claim 5).

  Hereinafter, a combustion chamber structure of a direct injection internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the overall configuration, and FIG. FIGS. 3A to 3C are schematic views showing an ignition plug provided with a portion to be injected, and FIG. 4 is a schematic view showing a lower surface of a cylinder head in a combustion chamber. FIG. 5 is a diagram showing the case where the plug attachment angle is 0 degrees, FIG. 5 is a schematic view showing the lower surface of the cylinder head of the combustion chamber, and shows the case where the ignition plug attachment angle is 90 degrees, and FIG. FIG. 7 is a schematic diagram showing the lower surface of the cylinder head, showing a case where the attachment angle of the spark plug is 180 degrees, and FIG. 7 is a schematic graph showing combustion stability according to the attachment angle of the plug.

As shown in FIG. 1, a combustion chamber 11 of a spray guide type direct injection engine (hereinafter referred to as a “spray guide direct injection engine”) 10 includes a lower surface 12 </ b> A of a cylinder head 12, a cylinder liner 13 </ b> A of a cylinder block 13, The upper surface 14A of the piston 14 is surrounded and formed.
The cylinder head 12 is provided with an intake valve 16 that opens and closes the intake port 15 and an exhaust valve 18 that opens and closes the exhaust port 17, and is connected to the combustion chamber 11 between the intake port 15 and the exhaust port 17. The spark plug 20 and the injector 19 are provided close to each other so as to protrude.

  The injector 19 injects gasoline (fuel) toward a shroud 23 (described later) of the spark plug 20. The injector 19 forms an atmosphere close to stoichiometric around the spark plug 20, and the spark plug 20. A lean atmosphere can be formed in the combustion chamber 11 by forming a lean atmosphere at a location away from the combustion chamber 11.

A center electrode 21 and a side electrode 22 are provided at one end of the spark plug 20, and a spark is generated between the center electrode 21 and the side electrode 22. Further, as shown in FIGS. 2 and 3A to 3C, an insulator portion (center electrode insulating portion) 24 that covers the center electrode 21 except for the tip portion of the center electrode 21 is provided.
Further, the spark plug 20 is provided with a metal case portion 25 formed with a male screw so that it can be screwed into a female screw portion 12A formed on the cylinder head 12.

Further, the spark plug 20 is formed on the side of the center electrode 21 (one end side) so as to surround the entire circumference of the center electrode 21 between the center electrode 21 and the injector 19 and between the center electrode 21 and the injector 19. A shroud (injected part) 23 for receiving gasoline injected from the injector 19 is formed.
The shroud 23 is formed so as to surround the entire circumference of the center electrode 21, and is formed integrally with the case portion 25.

The shroud 23 is formed with four circular hole portions (communication portions) 26. In addition, when the phase to which the side pole 22 is fixed in the shroud 23 is 0 degree, these hole portions 26 are formed at positions of 0 degree, 90 degrees, 180 degrees, and 270 degrees, respectively. Further, these hole portions 26 are formed at positions facing the insulator portion 24.
Since the combustion chamber structure of the direct injection internal combustion engine according to the embodiment of the present invention is configured as described above, the following operations and effects are achieved.

  When gasoline is injected from the injector 19, the gasoline is received by a shroud 23 formed at one end of the spark plug 20. As a result, gasoline that is not sufficiently atomized can be prevented from directly adhering to the center electrode 21, and the combustion stability of the spray guide direct injection engine 10 can be improved. In particular, when the injector 19 and the center electrode 21 are close to each other as in this embodiment and the fuel vaporization time cannot be taken, the shroud 23 can promote the vaporization of the fuel and improve the combustion stability.

In addition, even if gasoline that is not sufficiently atomized adheres to the insulator part 24 and becomes carbon, the flame generated in the combustion chamber 11 reaches the insulator part 24 through the hole part 26. Therefore, it is possible to burn off the attached carbon. Thereby, the fall of the spark performance of the spark plug 20 can be prevented, and the fall of combustion stability can be prevented.
Further, since the shroud 23 formed close to the center electrode 21 is at a high temperature, the high-temperature shroud 23 receives the gasoline injected from the injector 19 so that the atomized gasoline as well as the atomized gasoline can be used. Even the gasoline that has not been sufficiently atomized can be vaporized, and further, this vaporized gasoline can reach the vicinity of the center electrode 21 through the hole 26, so that the spray guide direct injection engine 10 can be stably combusted. Can be improved.

Further, since the shroud 23 is formed so as to surround the entire circumference of the center electrode 21, stable combustion can be ensured regardless of the mounting angle of the spark plug 20.
This point will be described with reference to FIGS. 4 to 6. For example, as shown in FIG. 4, when the tip 22 a of the side electrode 22 is disposed opposite to the injection direction of the gasoline G from the injector 19 ( When the spark plug 20 mounting angle is 0 degree and the tip 22a of the side pole 22 is disposed so as to be orthogonal to the gasoline G injection direction as shown in FIG. 5 (the spark plug 20 mounting angle = 90). Or 270 degrees), and when the tip 22a of the side pole 22 is disposed in the same direction as the gasoline G injection direction (ignition plug 20 mounting angle = 180 degrees) as shown in FIG. Even when the mounting angle of the plug 20 varies, substantially the same combustion characteristics can be obtained.

That is, as shown in FIG. 7, the region indicated by reference sign A ₁ indicates the fuel injection timing and the ignition timing at which combustion is stable when the mounting angle of the spark plug 20 is 0 degree (see FIG. 4). The region indicated by symbol A ₂ indicates the fuel injection timing and ignition timing at which the combustion is stabilized when the mounting angle of the spark plug 20 is 90 ° or 270 ° (see FIG. 5), and further indicated by symbol A ₃ . The region indicates the fuel injection timing and ignition timing at which combustion is stable when the attachment angle of the spark plug 20 is 180 degrees (see FIG. 6).

As can be seen from FIG. 7, even if the mounting angle of the spark plug 20 varies, the region A ₀ in which these n regions A _{1 to} A ₃ overlap (that is, the fuel injection timing and the ignition timing can be controlled). Area) can be secured widely. In this respect, it is obvious that the overlapping area A _{0 of} the present invention can be secured larger than the area A ₁₀₀ in FIG. 12 showing the conventional combustion characteristics.

Therefore, it is possible to freely control the fuel injection timing and the ignition timing within such a wide range A ₀ , and to prevent a situation in which the combustion stability is impaired.
Further, since the center electrode 21 is covered with the insulator part 24 except for the tip part, and the hole part 26 is formed at a position opposite to the insulator part 24, the gasoline that is not sufficiently atomized should be used. Even if it passes through the hole 26, this gasoline can be prevented from reaching the center electrode 21.

Moreover, since the shroud 23 is formed integrally with the case portion 25, the productivity of the spark plug 20 can be improved.
Further, by providing a plurality of holes 26, the gasoline that is received by the shroud 23 and vaporized can easily reach the vicinity 21 of the center electrode.
Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and various modifications can be made without departing from the spirit of the present invention.

In the above-described embodiment, the case where four holes 26 are formed has been described as an example. However, for example, fewer than four holes may be formed, or more than four holes may be formed. A part may be formed.
In the above-described embodiment, the case where the hole portion 26 is circular has been described as an example. However, the hole portion 26 is not limited to a circular shape, and may be, for example, an elliptical or polygonal hole or slit.

It is typical sectional drawing which shows the whole structure of the combustion chamber structure of the cylinder injection type internal combustion engine which concerns on one Embodiment of this invention. 1 is a schematic perspective view showing a spark plug of a combustion chamber structure of a direct injection internal combustion engine according to an embodiment of the present invention. It is a figure which shows the ignition plug of the combustion chamber structure of the direct injection internal combustion engine which concerns on one Embodiment of this invention, Comprising: (A) is the typical top view, (B) is the typical front view, (C) is the typical side view. It is a schematic diagram which shows the relationship between the fuel injection valve of the combustion chamber structure of the direct injection internal combustion engine which concerns on one Embodiment of this invention, and a spark plug. It is a schematic diagram which shows the relationship between the fuel injection valve of the combustion chamber structure of the direct injection internal combustion engine which concerns on one Embodiment of this invention, and a spark plug. It is a schematic diagram which shows the relationship between the fuel injection valve of the combustion chamber structure of the direct injection internal combustion engine which concerns on one Embodiment of this invention, and a spark plug. 4 is a schematic graph showing the relationship between the ignition timing and the fuel injection timing according to the arrangement angle of the ignition plug in the combustion chamber structure of the direct injection internal combustion engine according to the embodiment of the present invention. It is typical sectional drawing which shows the whole structure of the combustion chamber structure of the conventional cylinder injection type internal combustion engine. It is a schematic diagram which shows the relationship between a fuel injection valve and a spark plug in the combustion chamber structure of the conventional cylinder injection type internal combustion engine. It is a schematic diagram which shows the relationship between a fuel injection valve and a spark plug in the combustion chamber structure of the conventional cylinder injection type internal combustion engine. It is a schematic diagram which shows the relationship between a fuel injection valve and a spark plug in the combustion chamber structure of the conventional cylinder injection type internal combustion engine. 6 is a schematic graph showing a relationship between an ignition timing and a fuel injection timing according to an arrangement angle of an ignition plug in a conventional combustion chamber structure of a cylinder injection internal combustion engine.

Explanation of symbols

10 Engine (Cylinder injection type internal combustion engine)
11 Combustion chamber 19 Injector (fuel injection valve)
20 Spark plug 21 Center electrode 23 Shroud (injected part)
24 Insulator (center electrode insulation)
25 Case 26 Hole

Claims (5)

An ignition plug provided with a center electrode on one end projecting toward a combustion chamber of a direct injection internal combustion engine, and a fuel injection valve for injecting fuel toward the one end of the ignition plug A combustion chamber structure of a cylinder injection internal combustion engine,
An injectable portion that is formed between the center electrode and the fuel injection valve on the one end side of the spark plug and receives fuel injected from the fuel injection valve;
A center electrode insulating portion covering the center electrode except for the tip of the center electrode;
A communication portion formed in the injected portion and communicating between the central electrode side and the fuel injection valve side ;
The in-cylinder injection internal combustion engine according to claim 1, wherein the communication portion is formed at a position excluding a tip portion of the center electrode and facing the center electrode insulating portion . Combustion chamber structure. 2. The combustion chamber structure of a direct injection internal combustion engine according to claim 1, wherein the injected portion is formed so as to surround the entire circumference of the center electrode. A case portion is provided on the outer periphery of the side surface of the spark plug to fix the spark plug to the combustion chamber,
The combustion chamber structure of a direct injection internal combustion engine according to claim 1 or 2 , wherein the injected portion is formed integrally with the case portion. Characterized in that the communicating portion is provided with a plurality of combustion chamber structure for a direct injection type internal combustion engine according to what Re one of claims 1-3. Said center electrode and opposite to the side electrode is located, characterized in that provided to said injection portion, of the cylinder injection type internal combustion engine according to what Re or one of 請 Motomeko 1-4 Combustion chamber structure.

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