JPH0748982Y2 - Combustion device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a combustion device of an internal combustion engine for a low cetane number fuel, which prevents a temperature decrease of a glow plug which assists ignition of fuel and realizes a stable combustion state. .

<Prior Art> In recent years, alternative fuels for gasoline have been studied due to concerns about crude oil supply, and fuels containing alcohol such as ethanol or methanol have come to be widely used. Engines (low cetane number fuel engines) are also emerging. Current,
The most promising alcohol fuel is methanol. Alcohol fuel can be roughly divided into two types, that is, a mixed use with a conventional fuel and so-called straight use.

In a diesel type alcohol engine that uses an alcohol fuel having a low cetane number and a poor ignitability, a fuel injection nozzle for injecting fuel into a combustion chamber is provided in a cylinder head of the engine and ejects from the fuel injection nozzle. A glow plug for heating the atomized fuel to promote ignition and combustion is disposed on the downstream side in the fuel ejection direction. A heat generating portion having a heat source such as a nichrome wire that can be energized is built in at the tip of the glow plug that protrudes into the combustion chamber. Ignition and combustion are promoted while maintaining the above high temperature condition.
That is, in such an engine, the air in the combustion chamber is compressed into a high temperature and high pressure state by the piston compression process,
The piston is slid by injecting fuel from the fuel injection nozzle and igniting and burning by the above-mentioned glow plug heating action to generate a driving force.

<Problems to be solved by the invention> In order to keep ignition and combustion of a diesel engine or the like in a suitable state, the glow plug must be energized at the same time as the engine is started and always kept at a predetermined temperature during operation. There is. However, this glow plug is cooled by a violent gas flow such as a swirl flow in the combustion chamber, and at the same time, mist-like fuel ejected from the fuel injection nozzle adheres to the glow plug and a large amount of this fuel is heated and vaporized. The heat is taken away. If a glow plug is installed on the downstream side in the direction of fuel injection in order to further improve the ignitability, atomized fuel will be directly injected to the glow plug, and the temperature of the glow plug will be reduced. The decrease is significant. For this reason, there is a problem in that it is difficult to achieve a stable combustion state because sufficient heating is not performed by the glow plug.

<Means for Solving the Problems> A combustion device for an internal combustion engine according to the present invention includes a fuel injection nozzle for injecting fuel into an air flow formed around a cylinder axis in a combustion chamber, and an injection by the fuel injection nozzle. In a combustion device for an internal combustion engine, comprising: a glow plug that heats the fuel and accelerates combustion of the fuel; and a plug cover that surrounds a heat generating portion of the glow plug,
Penetration that penetrates only two side surfaces, a side surface intersecting the flow direction of the air flow and a side surface on the downstream side in the flow direction of the air flow with the glow plug as a reference, to communicate the inside of the plug cover with the combustion chamber. A hole is provided in the plug cover.

<Operation> The fuel is injected from the fuel injection nozzle into the air flow formed in the combustion chamber, and a part of the fuel reaches the glow plug that promotes combustion of the fuel. Only the required amount reaches the heat generating portion and is burned by being blocked by the plug cover surrounding the heat generating portion. That is, the flow direction of the air flow is on the side portion of the plug cover located on the downstream side in the flow direction of the air flow with reference to the through hole or the glow plug provided in the plug cover penetrating in the direction intersecting the flow direction of the air flow. Through a through hole provided in parallel with
Only the required amount of fuel or air flow flows into the plug cover, is heated by the glow plug and burns, and its flame propagates through the through hole into the combustion chamber.

<Embodiment> An embodiment in which a combustion apparatus for an internal combustion engine according to the present invention is applied to an alcohol engine will be described in detail below with reference to the drawings.

As shown in FIG. 1 which is a schematic sectional view of a cylinder head portion of an engine according to this embodiment, a cylinder head 13 is attached to an upper portion of a cylinder block 12 having a piston 11 therein. , This cylinder head
A fuel injection nozzle 16 for injecting fuel into a combustion chamber 14 formed at the top of the piston 11 is provided at 13 so as to project into the combustion chamber 14. A plurality of injection holes (not shown) are bored in the tip portion 17 of the fuel injection nozzle 16, and the fuel is injected radially from these injection holes. Therefore, the outside air introduced into the cylinder 18 through the intake port (not shown) becomes high temperature and high pressure in accordance with the compression process due to the rise of the piston 11, and the combustion chamber 14
By injecting the fuel from the fuel injection nozzle 16 into the inside, the fuel is spontaneously ignited and burned.

However, in an engine using a low cetane number fuel having poor ignitability, a sufficient temperature state cannot be achieved only by the heat generated by the compression process described above, so that it is difficult to realize smooth ignition and combustion of the injected fuel. Therefore, in the cylinder head 13, a glow plug 19 for heating the atomized fuel and its mixture injected from the fuel injection nozzle 16 to facilitate ignition is injected into the combustion chamber 14 and the fuel is injected. It is provided close to the nozzle 16. The glow plug 19 has the following configuration. That is, in the cylinder head 13, the cylindrical plug holder 20 is attached to the combustion chamber 14
A nut 21 that is fitted in a state of penetrating inside, is positioned by a knock pin 22 that is interposed between the side surface of the plug holder 20 and the cylinder head 13, and is provided at one end of the plug holder 20. By cylinder head 13
It is fixed to. Inside the plug holder 20, a plug main body 24 having a heat generating portion 23 formed at the end projecting into the combustion chamber 14
However, it is detachably fitted, and the heat generated by the heat generating portion 23 heats the fuel to improve the ignitability. Further, the heat generating portion 23 is arranged on the downstream side of the fuel injection flow from the fuel injection nozzle 16 to further improve the ignitability. Heating part 23
Has a structure in which a nichrome wire (not shown) is built in a cap made of, for example, a heat-resistant material, and heat is generated by energizing the nichrome wire.

By the way, in the combustion chamber 14 in the process where fuel is injected from the fuel injection nozzle 16 and combustion is performed, a swirl flow generated by the shape of the intake port (not shown) or a squish flow generated by the compression process of the piston 11 is formed. There is a characteristic and violent air stream 25 that Therefore, such an air flow 25 or the fuel injected from the fuel injection nozzle 16 is blown to the heat generating portion 23 of the plug body 24, whereby a large amount of heat is taken from the heat generating portion 23. It becomes impossible to maintain a constant high temperature state, and the suitable ignition assist function is lost. Therefore, at the end of the plug holder 20 on the combustion chamber 14 side, in order to prevent the temperature drop of the heat generating part 23 by appropriately blocking the airflow 25 and the fuel blown to the heat generating part 23 of the plug body 24, A pod-like plug cover 26 surrounding 23 is attached. That is, as shown in FIG. 2 which is a perspective view of the main part of the combustion chamber 14 and in FIG. 3 which is a transverse cross section of the plug cover 26 (AA cross section in FIG. 1), the plug cover 26 is described above. The atomized fuel flow 27 injected from the injection hole (not shown) of the fuel injection nozzle 16 is supplied to the heat generating portion 23 of the glow plug 19 on the left side portion in the drawing where the air flow 25 is not directly blown. An introduction hole 28 for guiding is formed so as to cross the flow direction of the air flow 25 so as to communicate the space 29 between the plug cover 26 and the heat generating portion 23 with the downstream side of the fuel flow 27.
Furthermore, on the lower side in the figure of the plug cover 26 where the above-mentioned air flow 25 does not directly blow, the combustion chamber 14 is provided with a flame that is introduced from the introduction hole 28 and heated by the heat generating portion 23 and ignited.
A propagating hole 30 for propagating inside penetrates in parallel with the flow direction of the air flow 25 so as to connect the void 29 and the combustion chamber 14 to each other.

Therefore, only the required amount of fuel injected from the fuel injection nozzle 16 and the outside air introduced from the intake port (not shown) is
It penetrates into the plug cover 26 through the introduction hole 28 and is ignited and burned by the heat generating portion 23. The flame associated with this combustion is
Alternatively, the stable combustion state is maintained by propagating through the introduction hole 28 into the combustion chamber 15. As described above, the heat generating portion 23 of the glow plug 19 has the plug cover in which the introduction hole 28 and the propagation hole 30 are formed.
By 26, the above-mentioned air flow 25 is not directly exposed and only the required amount of fuel is delivered to the heat generating portion 23, so that the temperature decrease of the heat generating portion 23 can be minimized.

<Effect of the Invention> According to the combustion apparatus for an internal combustion engine of the present invention, the plug cover surrounding the heat generating portion of the glow plug is provided with a cover side surface that intersects the air flow direction and a downstream side surface of the air flow. ,
Since the through holes are provided only on the two side surfaces, the following effects can be obtained.

The required amount of fuel is supplied to the glow plug from the through hole on the side of the cover that intersects the air flow direction, and the upstream side in the flow direction affected by the swirl flow is covered by the cover, so vaporization of the deposited fuel It is possible to reduce the cooling effect due to the swirl flow or to keep the temperature of the glow plug high at all times, and improve the ignition performance and the glow plug durability.

Since the flame ignited by the glow plug propagates to the combustion chamber through the through hole on the side surface on the downstream side of the air flow, the flame is propagated on the swirl flow in the combustion chamber to promote combustion.

[Brief description of drawings]

FIG. 1 is a schematic structural sectional view showing an embodiment of a combustion apparatus for an internal combustion engine according to the present invention, FIG. 2 is a perspective view of a main part according to this embodiment, and FIG. 3 is an AA line in FIG. FIG. In the drawing, 11 is a piston, 12 is a cylinder block, 13 is a cylinder head, 14 is a combustion chamber, 16 is a fuel injection nozzle, 19 is a glow plug, 20 is a plug holder, 23 is a heat generating part, 25 is an air flow, and 26 is Plug cover, 27 is fuel flow, 28 is inlet hole, 30
Is a transmission hole.

Claims (1)

[Scope of utility model registration request] 1. A fuel injection nozzle for injecting fuel into an air flow formed around a cylinder axis in a combustion chamber, and heating the fuel injected by the fuel injection nozzle to promote combustion of the fuel. In a combustion device for an internal combustion engine including a glow plug, a plug cover surrounding a heat generating portion of the glow plug is provided, and a side surface intersecting with a flow direction of the air flow and the air flow of the glow plug are used as a reference. A combustion device for an internal combustion engine, wherein the plug cover is provided with a through hole penetrating only two side faces, i.e., a downstream side face in the flow direction, for communicating the inside of the plug cover with the combustion chamber.