JP4972030B2 - Engine and spark plug for engine - Google Patents

Description

  In the present invention, an ignition plug having an ignition chamber formed in a plug cover covering an ignition point is mounted on a cylinder head, and a plurality of nozzle holes communicating the ignition chamber and a combustion chamber facing a piston are provided in the plug cover. The present invention relates to an engine for spark-igniting an air-fuel mixture flowing from a combustion chamber through an injection hole into an ignition chamber using an ignition plug, and an ignition plug used in the engine.

  The engine as described above compresses the air-fuel mixture sucked into the combustion chamber by the piston ascending, and the compressed air-fuel mixture passes through the injection hole provided in the plug cover of the spark plug. Then, the air-fuel mixture that has flowed into the ignition chamber is ignited by a spark plug and burned, and a combustion flame is injected into the combustion chamber through the nozzle hole (for example, (See Patent Document 1).

JP 2007-0797902

In the engine ignition chamber described in Patent Document 1, the flow of the air-fuel mixture flowing from the combustion chamber through the nozzle holes is a fast gas flow. That is, the air-fuel mixture that has flowed into the ignition chamber from the combustion chamber through the nozzle hole proceeds on the extension line of the nozzle hole in the ignition chamber and collides with the air-fuel mixture and the wall surface of the ignition chamber. Form a stable gas flow.
Thus, if the gas flow in the ignition chamber becomes unstable without regularity, the mixture concentration of the air-fuel mixture in the ignition chamber becomes non-uniform, and there may be local unburned residual gas after combustion. is there. If unburned residual gas remains in the vicinity of the ignition point of the ignition plug in the ignition chamber, there is a high risk of misfiring that cannot be spark-ignited in the air-fuel mixture containing the unburned residual gas when spark ignition is performed at the ignition point. It becomes difficult to form a stable combustion flame.

  The present invention has been made in view of the above problems, and an object of the present invention is to mount an ignition plug, in which an ignition chamber is formed in a plug cover covering an ignition point, to a cylinder head, and to face the ignition chamber and the piston. In an engine in which a plurality of nozzle holes communicating with the combustion chamber are provided in the plug cover, and the air-fuel mixture flowing into the ignition chamber from the combustion chamber via the nozzle holes is spark-ignited by an ignition plug at the ignition point, the air-fuel mixture is reliably Therefore, it is possible to provide a technology that can lead to an ignition point to suppress the occurrence of misfire, obtain a stable combustion flame, and realize a stable operation.

In order to achieve the above object, a spark plug in which an ignition chamber is formed in a plug cover covering an ignition point according to the present invention is mounted on a cylinder head, and a plurality of communication chambers that communicate the ignition chamber and a combustion chamber facing a piston are provided. The first characteristic configuration of the engine in which the nozzle hole is provided in the plug cover is as follows.
The ignition chamber is composed of a throat space provided with the nozzle hole, and an ignition space provided with the ignition point while extending to the cylinder head side in a state communicating with the throat space,
The inner diameter of the throat space portion is smaller than the inner diameter of the ignition space portion, and the central axis of the throat space portion is set to intersect the central axis of the ignition space portion.

According to the first characteristic configuration, the air-fuel mixture that has flowed into the ignition chamber from the combustion chamber via the nozzle hole is first allowed to flow into the throat space having a relatively small inner diameter, and then the ignition space having a relatively large inner diameter. Since the air-fuel mixture that has flowed from the nozzle hole is guided in the throat space portion so as to be directed to the communication direction of the throat space portion (the axial direction of the central axis of the throat space portion), It is possible to flow into the ignition space while maintaining that direction.
Since the central axis of the throat space is set to intersect the central axis of the ignition space, the air-fuel mixture has a certain directionality flowing from the throat space to the lower part of the ignition space. Forms a tumble flow (vertical vortex) extending in the vertical direction of the central axis in a cross-sectional view parallel to the central axis of the ignition space, and in the entire ignition space, particularly near the upper part in the ignition space Generate a relatively regular gas flow. Therefore, the air-fuel mixture is guided to the vicinity of the ignition point provided in the ignition space to mix the air-fuel mixture well, and at least the mixture concentration of the air-fuel mixture on the ignition point side is ensured to be the concentration of the newly introduced air-fuel mixture. In this state, the influence of unburned residual gas can be eliminated, the spark can be stably ignited by the spark plug, and misfire can be prevented well. Thereby, a stable combustion flame can be formed and a stable operation of the engine can be realized.

According to a second characteristic configuration of the engine according to the present invention, in addition to the first characteristic configuration, the ignition point is an upper portion in the ignition space portion and is disposed on a central axis of the ignition space portion. It is in.

According to the second characteristic configuration, since the ignition point is disposed on the central axis at the upper part in the ignition space, the air-fuel mixture sufficiently mixed by the tumble flow formed in the ignition space is obtained. Thus, it is almost surely guided in the vicinity of the ignition point, and a spark is reliably ignited at the ignition point to obtain a good combustion state of the air-fuel mixture.

According to a third characteristic configuration of the engine according to the present invention, in addition to the first or second characteristic configuration , a recess is formed on the top surface of the piston facing the cylinder head, and the piston is at a top dead center. In a state where the plug cover is positioned, at least the plug cover is disposed so as to enter the recess, and the ignition point is disposed on the side entering the recess from the top surface.

According to the third characteristic configuration, the air-fuel mixture can be concentrated in the recess, and the distance from each part of the combustion chamber to the ignition point in the ignition chamber can be shortened through the injection hole. After the air-fuel mixture flowing into the ignition chamber via the gas flows into the ignition chamber, it can immediately reach the ignition point, and stable ignition can be performed relatively easily and a good combustion state can be obtained.
In addition, after the mixture is spark-ignited and burned, a combustion flame can be immediately injected from the nozzle hole into the combustion chamber, and even in the case of lean combustion, the mixture is reliably burned in the combustion chamber. Thus, the combustion efficiency can be increased.

A plug body having an ignition point according to the present invention for achieving the above object, and a plug cover provided on the plug body so as to cover the ignition point, in a state of being mounted on a cylinder head of an engine, A first characteristic configuration of an engine ignition plug in which a plurality of injection holes communicating with a combustion chamber facing a piston and an ignition chamber formed in the plug cover are formed in the plug cover,
The ignition chamber is composed of a throat space provided with the nozzle hole, and an ignition space provided with the ignition point while extending to the cylinder head side in a state communicating with the throat space,
The inner diameter of the throat space portion is smaller than the inner diameter of the ignition space portion, and the central axis of the throat space portion is set to intersect the central axis of the ignition space portion.

According to the first characteristic configuration of the engine spark plug, the air-fuel mixture flowing from the combustion chamber into the ignition chamber through the nozzle hole is first compared by attaching the engine spark plug to the cylinder head of the engine. In the throat space with a small inner diameter, and subsequently into the ignition space with a relatively large inner diameter. It can be made to flow while being guided in the direction of the central axis, and can be allowed to flow into the ignition space while maintaining that direction.
Since the central axis of the throat space is set to intersect the central axis of the ignition space, the air-fuel mixture has a certain directionality flowing from the throat space to the lower part of the ignition space. Forms a tumble flow (vertical vortex) extending in the vertical direction of the central axis in a cross-sectional view parallel to the central axis of the ignition space, and in the entire ignition space, particularly near the upper part in the ignition space Generate a relatively regular gas flow. Therefore, the air-fuel mixture is guided to the vicinity of the ignition point provided in the ignition space to mix the air-fuel mixture well, and at least the mixture concentration of the air-fuel mixture on the ignition point side is ensured to be the concentration of the newly introduced air-fuel mixture. In this state, the influence of unburned residual gas can be eliminated, the spark can be stably ignited by the spark plug, and misfire can be prevented well. Thereby, a stable combustion flame can be formed and a stable operation of the engine can be realized.

The second characteristic feature of the engine spark plug according to the present invention, in addition to the first feature structure of the spark plug for the engine, the plug cover lies in comprising integrally formed on the plug body.

According to the second characteristic configuration of the engine ignition plug, since the plug cover that forms the ignition chamber is formed integrally with the ignition plug body, the ignition chamber (throat space portion, ignition space portion), ignition The position of the point and nozzle hole can be set in a predetermined positional relationship, and the desired ignition chamber, ignition point, and nozzle hole can be easily positioned in the engine simply by attaching a spark plug to the cylinder head of the engine. Can be realized. Therefore, it is not necessary to confirm the troublesome ignition chamber and the arrangement of the ignition point every time it is mounted, and it is possible to simply mount the spark plug and ensure a good combustion state.

[Implementation Embodiment
For implementation form of engine according to the present invention will be described with reference to FIGS. 1-3.
Here, FIG. 1 is a longitudinal sectional view of a plane parallel to the central axis Y of the ignition space 8b around the cylinder 3 upper part and the cylinder head 6 lower part of the engine 100, and FIG. FIG. 3 is a plan sectional view of the II-II plane orthogonal to the central axis X of the throat space 8a in the vicinity, and FIG. 3 is an enlarged longitudinal sectional view of the vicinity of the ignition chamber 8 in FIG.

〔engine〕
As shown in FIG. 1, an engine 100 forms a combustion chamber 1 by a piston 2, a cylinder 3 that houses the piston 2, and a top surface H of the piston 2 and an inner side surface of the cylinder 3 that are provided on the top of the cylinder 3. And a spark plug 7 for spark-igniting the air-fuel mixture M below the cylinder head 6. Then, the piston 2 is reciprocated in the cylinder 3 and the intake valve 4 and the exhaust valve (not shown) are opened and closed to perform intake, compression, combustion / expansion, and exhaust strokes in the combustion chamber 1. The reciprocating motion of the piston 2 is output as a rotational motion of a crankshaft (not shown) by a connecting rod (not shown), and such a configuration is not different from a normal 4-stroke internal combustion engine. The engine 100 is, for example, a two-valve engine provided with one intake valve 4 and one exhaust valve.

  The engine 100 uses city gas (13A), which is a gaseous fuel, as the fuel G. The intake valve 4 is opened in the intake stroke, and the air A and the fuel G are supplied from the intake port 5 to the combustion chamber 1. The air-fuel mixture M (preferably a lean air-fuel mixture) is sucked, the intake valve 4 and the exhaust valve are closed in the compression and combustion / expansion strokes, the sucked air-fuel mixture M is compressed, and spark ignition is performed by the spark plug 7. Then, the fuel G is combusted and expanded, and the exhaust valve is opened in the exhaust stroke so that the exhaust gas is discharged from the combustion chamber 1 to the exhaust port (not shown).

〔piston〕
As shown in FIG. 1, a so-called depth is formed at the center of the top surface H of the piston 2 facing the cylinder head 6 described later (the head surface of the piston 2 and the uppermost surface in the case of a longitudinal engine). A dish-shaped recess 2a is formed. Thereby, the combustion chamber 1 is comprised from the space formed in the recessed part 2a in addition to the space between the top | upper surface H of the piston 2, and the inner surface of the cylinder 3. FIG. By forming the combustion chamber 1 in this way, when the piston 2 rises in the compression stroke, a vortex flow from the periphery of the recess 2a toward the center of the recess 2a, so-called squish is generated.

〔cylinder head〕
The cylinder head 6 of the engine 100 is provided with an intake port 5 so that the air-fuel mixture M can be supplied to the combustion chamber 1 via the intake valve 4, and from a fuel supply valve 9 disposed in the intake port 5. The supplied fuel G and air A are appropriately mixed to form an air-fuel mixture M. The mixing ratio of the air-fuel mixture M is set so that it can be changed as appropriate according to the operating state of the engine 100. An air-fuel mixture M supplied to an ignition chamber 8 of an ignition plug 7 to be described later is supplied from the intake port 5 to the combustion chamber 1 via the intake valve 4, and from the combustion chamber 1 to the ignition chamber via the injection hole 10. Therefore, the fuel G and the mixture M are not directly supplied to the ignition chamber 8 of the ignition plug 7 via the injection hole 10.

(Ignition plug)
As shown in FIG. 1, a spark plug 7 that sparks and ignites the air-fuel mixture M is attached to a portion (the lowermost surface of the cylinder head 6) facing the concave portion 2 a of the piston 2 at the bottom of the cylinder head 6. The lowermost part of the spark plug 7 (the lowermost part of a plug cover 7b described later) is located below the lowermost surface of the cylinder head 6 and the top surface H of the piston 2, that is, in a state where the piston 2 is located at the top dead center. It is arranged so as to enter at least the recess 2a of the piston 2, and an ignition point P of a spark plug 7 to be described later is also below the lowermost surface of the cylinder head 6 and the top surface H of the piston 2, that is, the piston 2 is It arrange | positions so that it may penetrate | invade at least the recessed part 2a of the piston 2 in the state located in a top dead center. The lowermost portion of the plug cover 7b is set so as not to contact the bottom surface of the recess 2a of the piston 2. That is, the depth from the top surface H of the piston 2 to the bottom surface of the recess 2a is set to be greater than the length from the lowermost surface of the cylinder head 6 to the lowermost portion of the plug cover 7b of the spark plug 7. The ignition point P of the spark plug 7 is disposed on the central axis Y of the ignition space 8b formed by the plug cover 7b described later.

  As shown in FIGS. 1 and 3, the spark plug 7 is composed of a plug body 7a that forms an ignition point P at the tip and a plug cover 7b that is formed so as to cover the ignition point P. The cover 7b is provided on the plug body 7a, and an ignition chamber 8 having the ignition point P is formed inside the plug cover 7b. The spark plug 7 can be attached to the cylinder head 6 by screwing a screw portion provided on the outer periphery of the plug cover 7 b into the cylinder head 6.

Further, the plug cover 7b is formed with a plurality of injection holes 10 communicating between the ignition chamber 8 and the combustion chamber 1 facing the piston 2, and the ignition cover 8 is attached to the cylinder head 6. The air-fuel mixture M is configured to flow between the combustion chamber 1 and the combustion chamber 1.
That is, although details will be described later, by providing a plurality of injection holes 10 in the plug cover 7b, the air-fuel mixture M existing in the combustion chamber 1 in the compression stroke is transferred to the ignition chamber 8 through the plurality of injection holes 10. In addition, the combustion flame formed in the ignition chamber 8 in the combustion / expansion stroke can be injected into the combustion chamber 1 through the plurality of injection holes 10.
Here, the plug main body 7a and the plug cover 7b are integrally formed so as to cover the lower portion of the plug main body 7a and the ignition point P to constitute the ignition plug 7, and the ignition chamber 8, the ignition point P, The ignition plug 7 can be formed after appropriately setting the relative positional relationship of the nozzle hole 10 with respect to the plug body 7a and the plug cover 7b in advance, and is easily mounted on the engine 100.
The thickness of the plug cover 7b is not particularly limited as long as it can secure sufficient thermal durability and strength and can set the inflow direction of the air-fuel mixture M into the ignition chamber 8 with certainty. For example, the thickness can be about 1.5 to 3 mm. The plug cover 7b can be made of a material such as SUS (stainless steel).

[Engine operation]
The engine 100 employs the above-described configuration, thereby compressing the air-fuel mixture M sucked into the combustion chamber 1 by the ascending of the piston 2, and the compressed air-fuel mixture M from the combustion chamber 1 to the plug cover 7b. The air-fuel mixture M that has flowed into the ignition chamber 8 through the provided nozzle hole 10 and sparked into the ignition chamber 8 is ignited and burned by the spark plug 7 in the ignition chamber 8. It is comprised so that a combustion flame may be injected into the combustion chamber 1 via this. Hereinafter, the operation state of one cycle in the engine 100 will be described.

In the engine 100, first, the intake valve 4 is opened, and an intake stroke in which the air-fuel mixture M is drawn from the intake port 5 into the combustion chamber 1 is performed as the piston 2 descends from TDC (top dead center).
Later, the intake valve 4 is closed, and a so-called compression stroke is performed in which the air-fuel mixture M sucked into the combustion chamber 1 is compressed by the rise of the piston 2.
In the compression stroke, the air-fuel mixture M in the combustion chamber 1 flows into the ignition chamber 8 through the nozzle holes 10 due to the volume decrease of the combustion chamber 1 due to the piston 2 rising, and the air-fuel mixture M enters the ignition chamber 8. When the gas mixture M and the unburned residual gas already exist, the unburned residual gas is mixed with the unburned residual gas and the equivalent within the spark ignition possible range (for example, about 1). A mixture M of the ratio is formed.

  Then, the engine 100 operates the spark plug 7 immediately before top dead center, for example, near 8 ° BTDC, and sparks and burns at the ignition point P formed in the ignition chamber 8. Then, combustion proceeds in the ignition chamber 8, and a combustion flame is ejected to the combustion chamber 1 through the nozzle hole 10. That is, the combustion flames are radially injected into the combustion chamber 1 from a plurality of nozzle holes 10 that communicate the ignition chamber 8 and the combustion chamber 1.

  On the other hand, in the combustion chamber 1, the air-fuel mixture M is stably combusted by the combustion flames injected from the respective injection holes 10, so that combustion that achieves high efficiency and low NOx is performed without causing a rapid pressure increase. .

  The above is the description of the basic configuration and operation of the engine 100.

  In the engine 100 of the present application, the plug cover 7b (ignition chamber 8) of the spark plug 7 has a characteristic structure, so that the gas flow generated in the ignition chamber 8 is appropriately and relatively regular, and the mixture M The structure of such a characteristic plug cover 7b (ignition chamber 8) will be described below. The structure of the plug cover 7b (ignition chamber 8) is as follows. explain.

[Plug cover (ignition chamber)]
In the engine 100 of the present application, in particular, the plug cover 7b of the spark plug 7 of the present application is configured to flow the gas mixture (ignition gas) that guides the air-fuel mixture M from the combustion chamber 1 to the ignition point P in the ignition chamber 8 in the compression stroke. A tumble flow (longitudinal vortex) T) extending in the vertical direction of the chamber 8 can be generated. Here, the tumble flow refers to a vertical (rotating) vortex that rotates in the vertical direction of the ignition chamber 8.

  Specifically, as shown in FIGS. 1, 2, and 3, the plug cover 7 b is formed in a bottomed cylindrical shape so that an ignition chamber 8 can be formed on the inner side. The throat space 8a has a relatively small inner diameter, and the ignition space 8b has a relatively large inner diameter provided on the throat space 8a.

The throat space 8a has a bottom portion having a substantially spherical bottom and a cylindrical portion (center axis is X) at the top, and the combustion chamber 1 and the ignition chamber 8 are located at the bottom of the bottom portion. Are formed so that the air-fuel mixture M can flow between the ignition chamber 8 and the combustion chamber 1 while being attached to the cylinder head 6.
Specifically, as shown in FIG. 2 and FIG. 3, the plurality of nozzle holes 10 includes a plurality of (for example, four) nozzle holes 10 at equal intervals in the circumferential direction at the bottom of the substantially spherical bottomed portion. 2 and the inflow direction of each air-fuel mixture M flowing into the throat space 8a from the combustion chamber 1 through the nozzle hole 10 is perpendicular to the central axis X of the throat space 8a as shown in FIG. (Fig. 1, Fig. 3, top, II-II cross section)
All are formed so as to be in the direction of the central axis X. That is, the inflow direction of the nozzle hole 10 is formed in a linear direction in which the ignition chamber side end L and the central axis X are connected. Here, the ignition chamber side end L of the injection hole 10 refers to the innermost part where the injection hole 10 is in contact with the throat space 8a in a cross section orthogonal to the central axis X of the throat space 8a. 2 and 3, the plurality of nozzle holes 10 are arranged so as to be symmetric with respect to the central axis X.
Therefore, in the compression stroke, the air-fuel mixture M that has flowed into the ignition chamber 8 from the combustion chamber 1 through the nozzle hole 10 is connected to the central axis X along a linear path connecting the ignition chamber side end L and the central axis X. To each of the air-fuel mixtures M and in the vicinity of the central axis X

In addition, as shown in FIG. 3, these nozzle holes 10 are arranged such that the inflow direction of each air-fuel mixture M flowing from the combustion chamber 1 through the nozzle holes 10 into the throat space 8 a is the central axis X of the throat space 8 a. , With respect to the straight line connecting the ignition chamber side end L and the central axis X of the nozzle hole 10 along the direction orthogonal to the central axis X, with the ignition chamber side end L as the axis. It is formed on the side approaching the ignition point P (in FIG. 3, above the central axis X) by a predetermined angle β. Therefore, in the compression stroke, the air-fuel mixture M flowing into the ignition chamber 8 from the combustion chamber 1 through the nozzle hole 10 is in the vicinity of the central axis X along a path on an extension line shifted upward from the ignition chamber side end L by an angle β. And merges with each air-fuel mixture M in the vicinity of the central axis X. In FIG. 3, the predetermined angle β is the same angle at each nozzle hole 10, and the angle β = 45 degrees is exemplified.
Therefore, each air-fuel mixture M that has flowed into the throat space 8a having a relatively small inner diameter merges in the vicinity of the central axis X of the throat space 8a, and is along the central axis X of the throat space 8a. It is guided in the direction and flows upward, and flows into the ignition space 8b while maintaining this direction.

Next, as shown in FIG. 3, the ignition space portion 8 b includes a bottom portion having a substantially spherical shape and a cylindrical portion having a cylindrical shape (the center axis is Y) at the upper portion. The bottom portion of the bottomed portion communicates with the throat space portion 8a, and communicates with the air-fuel mixture M from the throat space portion 8a so that it can flow in. The cylindrical portion of the bottomed portion is configured to extend toward the cylinder head 6 (upper side in FIG. 3). Note that an ignition point P for spark-igniting the air-fuel mixture M is disposed on the central axis Y above the ignition space 8b.
In addition, the center axis Y of the ignition space portion 8b and the center axis X of the throat space portion 8a are set so as to intersect at a predetermined angle α as shown in FIG. The throat space 8a forms the ignition chamber 8 in an inclined state.
Therefore, as described above, the air-fuel mixture M flowing in the direction of the central axis X of the throat space 8a and flowing into the ignition space 8b has an angle α (in FIG. 3) with respect to the central axis Y, as shown in FIG. , Α = about 10 degrees) and flow through the ignition space 8b. As a result, the air-fuel mixture M has a certain directionality, and in the ignition space portion, a tumble flow (vertical direction) extending in the vertical direction of the central axis Y in a sectional view parallel to the central axis Y of the ignition space portion 8b. A vortex) T is formed, and a relatively regular gas flow is generated in the entire ignition space portion 8b, particularly in the vicinity of the upper portion in the ignition space portion 8b. 1 to 3, the central axis of the combustion chamber 1 is the same axis as the central axis Y of the ignition space portion 8 b of the spark plug 7, and furthermore, the same as the central axes of the piston 2 and the cylinder 3. It is the axis.

  Therefore, in the compression stroke, as shown in FIG. 3, the air-fuel mixture M is guided to the vicinity of the ignition point P arranged on the central axis Y in the upper part of the ignition space portion 8b, and the air-fuel mixture M is mixed well. Thus, at least the mixture concentration of the air-fuel mixture on the ignition point side can be secured to the concentration of the newly introduced air-fuel mixture, and unburned residual gas exists in the ignition space 8b of the spark plug 7. In particular, even when there is a large amount of unburned residual gas having a relatively low oxygen concentration in the vicinity of the central axis Y of the ignition space portion 8b or in the vicinity of the upper portion of the ignition space portion 8b, the gas flow of the mixture M Mixing of the air-fuel mixture M can be promoted by (tumble flow T) to eliminate the presence of local unburned residual gas.

  The predetermined angle α is the vertical direction of the central axis Y in the ignition space portion 8b due to the air-fuel mixture M having a certain directionality flowing from the throat space portion 8a to the lower portion of the ignition space portion 8b. Any angle that can form a tumble flow (vertical vortex) T can be selected as appropriate. For example, when the angle is about 5 degrees or more and 45 degrees or less, the tumble flow T can be accurately formed, and mixing of the entire ignition chamber 8, particularly the entire ignition space 8 b can be promoted. Incidentally, if the angle is too small, it is difficult to form a larger tumble flow T by causing the air-fuel mixture M flowing in from the nozzle holes 10 to collide only with the ceiling surface of the ignition space 8b. If the angle is increased too much, each air-fuel mixture M flowing in from each nozzle hole 10 collides only with the lower part of the side wall surface of the ignition space 8b, and guides the air-fuel mixture M upward (in the vicinity of the ignition point P). It becomes difficult to form a larger tumble flow T. That is, it is preferable to promote mixing by forming a larger tumble flow T and to prevent the unburned residual gas from staying locally in the ignition space 8b as much as possible.

  In addition, the predetermined angle β is appropriately determined as long as the air-fuel mixture M can be guided in the direction along the central axis X of the throat space 8a in the throat space 8a in the direction in which the ignition point P exists. You can choose. For example, when the number of nozzle holes is four, the air-fuel mixture M can be accurately guided in the direction in which the ignition point P exists if the angle is set to about 30 ° to 75 °. Incidentally, if the angle is made too small, the momentum of each air-fuel mixture M flowing from each nozzle hole 10 is attenuated, and it becomes difficult to form a large tumble flow T, and the ignition space 8b, particularly in the vicinity of the ignition point P, becomes difficult. Mixing may be difficult, and if the angle is too large, the air-fuel mixtures M do not merge in the vicinity of the central axis X, and a tumble flow T in the direction along the central axis X may be formed. This may make it difficult to promote mixing in the ignition space 8b, particularly in the vicinity of the ignition point P. Note that the angle β can be different for each nozzle hole 10 or can be set to the same angle.

  Therefore, the air-fuel mixture M having a certain directionality that has flowed into the ignition chamber 8 while generating a relatively regular gas flow (tumble flow T) from the combustion chamber 1 via the nozzle hole 10 has not been obtained. Even when the combustion residual gas exists in the ignition chamber 8, the mixing can be favorably promoted. In particular, the tumble flow T can sufficiently promote mixing even in the vicinity of the central axis Y where unburned residual gas tends to stay, particularly in the vicinity of the ignition point P at the top of the ignition space portion 8b. Thereby, the air-fuel mixture M can be stably ignited by the ignition point P of the spark plug 7 arranged on the central axis Y, and the occurrence of misfire can be prevented.

  Similarly, in the ignition chamber 8, the homogeneous air-fuel mixture M is combusted while generating a relatively regular gas flow (tumble flow T), so that the ignition chamber 8 (particularly, the ignition space portion 8b) at the time of combustion. The temperature distribution is in a substantially uniform state, generation of unburned residual gas after combustion can be sufficiently suppressed, and good combustion can be realized.

〔simulation result〕
Hereinafter, the simulation result about the gas flow (tumble flow T) in the ignition chamber 8 will be described with reference to FIGS. 4 and 9.
Embodiment
4 (a) is a longitudinal cross-sectional view showing the concentration distribution of the fuel G of the mixture M of the ignition chamber 8 according to the present embodiment, FIG. 4 (b), the ignition space 8b in FIGS. 4 (a) FIG. 9A is a longitudinal sectional view showing the concentration distribution of the fuel G of the air-fuel mixture M in the ignition chamber according to the comparative example, and FIG. 9B is a sectional view showing the concentration distribution of FIG. 9A. It is a plane sectional view showing concentration distribution of an ignition chamber in.
In the figure, in the air-fuel mixture M, the portion where the concentration of the fuel G is dark is shown in black, and the thin portion is shown in white, and the black region shows that there are many unburned residual gases having a lower oxygen concentration.

In the case of using the spark plug 7 having a plurality of injection holes 10 according to the implementation mode of the present application, as shown in FIGS. 4 (a), injection from the combustion chamber 1 is a lower FIGS. 4 (a) The air-fuel mixture M (shown in FIG. 4A as a white area where the concentration of the fuel G is relatively low, that is, the concentration of the air A is relatively high) passes through the holes 10 in the throat space 8a of the ignition chamber 8. It can be seen that it flows in, flows in the direction along the central axis X of the throat space 8a, and flows into the ignition space 8b whose diameter has been expanded in this direction. The air-fuel mixture M flowing in the direction along the central axis X forms a tumble flow T extending in the vertical direction of the ignition space portion 8b in the ignition space portion 8b. Accordingly, a tumble flow T is formed in the ignition space portion 8b, and the tumble flow T is guided in the vicinity of the ignition point P. The mixing is promoted in the vicinity of the upper portion of the ignition space portion 8b, and on the central axis Y. It can also be seen that the region where the concentration of the fuel G is relatively light is formed even at the ignition point P arranged at. That is, it can be confirmed that there is almost no unburned residual gas in the vicinity of the ignition point P (see FIG. 4B).
Therefore, in the present embodiment, it is possible to prevent a region where the concentration of fuel G is relatively high (region where the concentration of air A is relatively low) from being formed in the upper portion of the ignition space 8a, particularly in the vicinity of the ignition point P. A misfire at the ignition point P of the spark plug 7 can be prevented.
In the spark plug 7, the thickness of the plug cover 7b near the nozzle hole 10 is 1.5 mm, the inner diameter of the throat space 8a is 3.5 mm, the length of the cylinder is 11 mm, and the inner diameter of the ignition space 8b. The angle (α) at which the central axis X of the throat space 8a and the central axis Y of the ignition space 8b intersect is 10 degrees, the inflow direction of the nozzle hole 10 is an angle (β1) 55 degrees, and an angle (β2 ) The simulation was performed at 35 degrees with the number of nozzle holes 10 set to four. In this embodiment , since the plurality of nozzle holes 10 are arranged so as to be symmetric with respect to the central axis Y (see FIG. 4), the angle β in the two opposing nozzle holes 10 corresponding to FIG. As described above, the simulation is performed with two different angles β1 (β on the left side in FIG. 3) and β2 (β on the right side in FIG. 3).

[Comparative Example]
On the other hand, as a comparative example, the ignition chamber is not divided into the throat space portion 8a and the ignition space portion 8b, and is formed as one bottomed cylindrical ignition chamber. Further, the inflow direction of the plurality of nozzle holes is set in a substantially tangential direction from the ignition chamber side end of one nozzle hole to the ignition chamber side end of another nozzle hole adjacent in the same rotation direction, that is, the center of the ignition chamber In a cross-sectional view orthogonal to the axis, the angle between the ignition chamber side end and the central axis is shifted by about 90 degrees in the same rotation direction with the ignition chamber side end as the axis. A spark plug having a cross-sectional view parallel to the central axis and an angle β = 45 degrees shifted from the ignition chamber side end to the ignition point P with respect to a straight line connecting the ignition chamber side end and the central axis 9A, as shown in FIG. 9A, the air-fuel mixture M flows from the combustion chamber below the FIG. 9A through the nozzle hole, and the rotational flow having the center axis as the center of rotation. In practice, however, the air-fuel mixture M flows only in the vicinity of the outermost periphery in the ignition chamber, and in the vicinity of the central axis, particularly The upper and lower firebox it can be seen that does not exist mostly gas flow. That is, in the vicinity of the central axis, the fuel G concentration is relatively high over the upper and lower sides of the ignition chamber (FIG. 9 (a), the fuel G concentration is relatively high, that is, the air A concentration is relatively low. (Black area shown) is formed, and it can be confirmed that a large amount of unburned residual gas exists in the vicinity of the ignition point P (see FIG. 9B).

  Therefore, by setting the shape of the plug cover 7b (the throat space 8a and the ignition space 8b of the ignition chamber 8) appropriately as in the present application, a relatively regular gas flow (tumble flow T) is generated. As a result, it was confirmed that an excellent mixed state could be obtained by eliminating the influence of the unburned residual gas in the ignition chamber 8 (particularly in the ignition space 8b) as compared with the comparative example.

[ Reference example ]
Above you facilities embodiment, the ignition chamber 8 is constituted by a throat space 8a and the ignition space 8b, constituting the plug cover 7b and these central axis X and the center axis Y so as to intersect at a predetermined angle α However, the configuration is not limited to the above as long as the tumble flow T is formed in the ignition chamber 8 (particularly the ignition space portion 8b) and the inside of the ignition chamber 8 can be sufficiently mixed. The plug cover 7b may be configured such that the central axis X and the central axis Y are positioned in parallel at a predetermined distance D.
The engine 200 using the plug cover 7b in which the central axis X and the central axis Y are arranged in parallel at a predetermined distance D will be described below as reference examples based on FIG. 5, FIG. 6, and FIG. explain. Incidentally, for the points as above you facilities embodiment will be omitted as appropriate for the sake of simplicity.
Here, FIG. 5 is a longitudinal sectional view of a plane parallel to the central axis Y of the ignition space portion 8b around the cylinder 3 upper portion and the cylinder head 6 lower portion of the engine 200. FIG. FIG. 7 is a plan sectional view of the VI-VI plane perpendicular to the central axis X of the throat space 8a in the vicinity, and FIG. 7 is an enlarged longitudinal sectional view of the vicinity of the ignition chamber 8 in FIG.

The engine 200 of the reference example is different in the configuration of the plug cover 7b (ignition chamber 8) of the ignition plug 7 as described above.

[Plug cover (ignition chamber)]
In engine 200, in particular, the plug cover 7b of point fire plugs 7, in the compression stroke, the gas flow so as to guide the air-fuel mixture M from the combustion chamber 1 to the ignition point P of the ignition chamber 8 (ignition chamber 8 The tumble flow (longitudinal vortex) T) extending in the vertical direction is generated. Here, the tumble flow refers to a longitudinal (swirl) vortex that rotates in the vertical direction of the ignition chamber.

  Specifically, as shown in FIGS. 5, 6, and 7, the plug cover 7 b is formed in a bottomed cylindrical shape so that the ignition chamber 8 can be formed on the inner side. The throat space 8a has a relatively small inner diameter, and the ignition space 8b has a relatively large inner diameter provided at the top of the throat space 8a.

The throat space 8a has a bottom portion having a substantially spherical bottom and a cylindrical portion (center axis is X) at the top, and the combustion chamber 1 and the ignition chamber 8 are located at the bottom of the bottom portion. Are formed so that the air-fuel mixture M can flow between the ignition chamber 8 and the combustion chamber 1 while being attached to the cylinder head 6.
Specifically, as shown in FIGS. 6 and 7, the plurality of nozzle holes 10 are a plurality of (for example, four) nozzle holes 10 at equal intervals in the circumferential direction at the bottom of the substantially spherical bottomed portion. 6 and the inflow direction of each air-fuel mixture M flowing into the throat space 8a from the combustion chamber 1 through the nozzle hole 10 is perpendicular to the central axis X of the throat space 8a as shown in FIG. (Fig. 5, Fig. 7, top, VI-VI cross section)
All are formed so as to be in the direction of the central axis X. That is, the inflow direction of the nozzle hole 10 is formed in a linear direction in which the ignition chamber side end L and the central axis X are connected. Here, the ignition chamber side end L of the injection hole 10 refers to the innermost part where the injection hole 10 is in contact with the throat space 8a in a cross section orthogonal to the central axis X of the throat space 8a.
Therefore, in the compression stroke, the air-fuel mixture M that has flowed into the ignition chamber 8 from the combustion chamber 1 through the nozzle hole 10 is connected to the central axis X along a linear path connecting the ignition chamber side end L and the central axis X. To each of the air-fuel mixtures M and in the vicinity of the central axis X.

In addition, as shown in FIG. 7, the injection holes 10 are arranged such that the inflow direction of each air-fuel mixture M flowing from the combustion chamber 1 through the injection holes 10 into the throat space 8 a is the central axis X of the throat space 8 a. , With respect to the straight line connecting the ignition chamber side end L and the central axis X of the nozzle hole 10 along the direction orthogonal to the central axis X, with the ignition chamber side end L as the axis. A predetermined angle β (about 45 degrees in FIG. 7) is shifted to the side approaching the ignition point P (above the central axis X in FIG. 7). Therefore, in the compression stroke, the air-fuel mixture M flowing into the ignition chamber 8 from the combustion chamber 1 through the nozzle hole 10 is in the vicinity of the central axis X along a path on an extension line shifted upward from the ignition chamber side end L by an angle β. And merges with each air-fuel mixture M in the vicinity of the central axis X.
Therefore, each air-fuel mixture M that has flowed into the throat space 8a having a relatively small inner diameter merges in the vicinity of the central axis X of the throat space 8a, and is along the central axis X of the throat space 8a. It is guided in the direction and flows upward, and flows into the ignition space 8b while maintaining this direction.

Next, as shown in FIG. 7, the ignition space portion 8 b includes a bottom portion having a substantially spherical shape and a cylindrical portion having a cylindrical shape (the center axis is Y) at the upper portion. The bottom portion of the bottomed portion communicates with the throat space portion 8a, and communicates with the air-fuel mixture M from the throat space portion 8a so that it can flow in. Further, the cylindrical portion of the bottomed portion is configured to extend to the cylinder head 6 side (upper side in FIG. 7). Note that an ignition point P for spark-igniting the air-fuel mixture M is disposed on the central axis Y above the ignition space 8b.
In addition, as shown in FIG. 7, the central axis Y of the ignition space portion 8b and the central axis X of the throat space portion 8a are arranged in parallel and shifted by a predetermined distance D, and the center of the ignition space portion 8b is arranged. One end portion (radial end portion) of the throat space portion 8a is arranged at one end portion (radial end portion) of the ignition space portion 8b in a direction orthogonal to the axis Y. . That is, the central axis Y and the central axis X are set to be parallel at a predetermined distance D, and the cylindrical portion of the ignition space portion 8b and the cylindrical portion of the throat space portion 8a are parallel to each other. And one end of these cylindrical portions share the side wall surface (constituted by the same side wall surface) to form the ignition chamber 8.
Therefore, the air-fuel mixture M that flows in the direction of the central axis X of the throat space 8a and flows into the ignition space 8b as described above is parallel to the central axis Y and the central axis as shown in FIG. Since the gas flows through the ignition space portion 8b with a distance D on average from Y, the air-fuel mixture M has a certain directionality, and the ignition space portion 8b has an ignition space portion 8b. A tumble flow (longitudinal vortex) T extending in the vertical direction of the central axis Y is formed in a cross-sectional view parallel to the central axis Y, and is relatively regular in the entire ignition space portion 8b, particularly in the vicinity of the upper portion in the ignition space portion 8b. Gas flow is generated. At this time, since the throat space 8a is provided at one end of the ignition space 8b, the air-fuel mixture M is added to the ignition space 8b in the vertical direction while maintaining a certain directionality. The tumble flow T flows greatly in the left-right direction, and the tumble flow T becomes a large gas flow not only in the vertical direction of the ignition space portion 8b but also in the left-right direction, resulting in a larger tumble flow T and further promoting mixing. 5, 6, and 7, the center axis of the combustion chamber 1 is the same axis as the center axis Y of the ignition space portion 8 b of the spark plug 7, and further, the center of the piston 2 and the cylinder 3 is used. The axis is the same axis.

  Therefore, in the compression stroke, as shown in FIG. 7, the air-fuel mixture M is guided to the vicinity of the ignition point P disposed on the central axis Y at the upper part in the ignition space portion 8b, and the air-fuel mixture M is mixed well. Thus, at least the mixture concentration of the air-fuel mixture on the ignition point side can be secured to the concentration of the newly introduced air-fuel mixture, and unburned residual gas exists in the ignition space 8b of the spark plug 7. In particular, even when there is a large amount of unburned residual gas having a relatively low oxygen concentration in the vicinity of the central axis Y of the ignition space portion 8b or in the vicinity of the upper portion of the ignition space portion 8b, the gas flow of the mixture M Mixing of the air-fuel mixture M can be promoted by (tumble flow T) to eliminate the presence of local unburned residual gas.

  The predetermined distance D can be appropriately selected as long as the tumble flow (vertical vortex) T extending in the vertical direction of the central axis Y can be formed in the ignition space 8b. For example, when the ratio D / R between the diameter (R) of the inner diameter of the ignition space 8b and the distance (D) is about 0.125 or more and 0.25 or less, the tumble flow T can be accurately formed, Mixing in the entire ignition chamber 8, particularly in the entire ignition space 8b, can be promoted. Incidentally, if the ratio is too small, it is difficult to form a larger tumble flow T by causing each air-fuel mixture M flowing in from each nozzle hole 10 to collide only with the ceiling surface near the central axis Y of the ignition space 8b. If the ratio is increased too much, the radial end portion of the throat space portion 8a becomes outside the radial end portion of the ignition space portion 8b, and the air-fuel mixture M becomes a side wall surface of the ignition space portion 8b. There is a risk that it will be difficult to form the tumble flow T well. That is, it is preferable to promote mixing by forming a larger tumble flow T and to prevent the unburned residual gas from staying locally in the ignition space 8b as much as possible.

  Further, the predetermined angle β may be appropriately selected as long as it can be guided in the direction along the central axis X of the throat space 8a in the throat space 8a in the direction in which the ignition point P exists. it can. For example, when the angle is about 30 degrees or more and 75 degrees or less, the air-fuel mixture M can be accurately guided in the direction in which the ignition point P exists. Incidentally, if the angle is made too small, the momentum of each air-fuel mixture M flowing from each nozzle hole 10 is attenuated, and it becomes difficult to form a large tumble flow T, and the ignition space 8b, particularly in the vicinity of the ignition point P, becomes difficult. Mixing may be difficult, and if the angle is increased too much, the air-fuel mixture M does not merge in the vicinity of the central axis X, and a tumble flow T may be formed in the direction along the central axis X. This may make it difficult to promote mixing in the ignition space 8b, particularly in the vicinity of the ignition point P.

  Therefore, the air-fuel mixture M having a certain directionality that has flowed into the ignition chamber 8 while generating a relatively regular gas flow (tumble flow T) from the combustion chamber 1 via the nozzle hole 10 has not been obtained. Even when the combustion residual gas exists in the ignition chamber 8, the mixing can be favorably promoted. In particular, the tumble flow T can sufficiently promote mixing even in the vicinity of the central axis Y where unburned residual gas tends to stay, particularly in the vicinity of the ignition point P at the top of the ignition space portion 8b. Thereby, the air-fuel mixture M can be stably ignited by the ignition point P of the spark plug 7 arranged on the central axis Y, and the occurrence of misfire can be prevented.

  Similarly, in the ignition chamber 8, the homogeneous air-fuel mixture M is combusted while generating a relatively regular gas flow (tumble flow T), so that the ignition chamber 8 (particularly, the ignition space portion 8b) at the time of combustion. The temperature distribution is in a substantially uniform state, generation of unburned residual gas after combustion can be sufficiently suppressed, and good combustion can be realized.

〔simulation result〕
Hereinafter, the simulation result about the gas flow (tumble flow T) in the ignition chamber 8 will be described with reference to FIG.
[ Reference example ]
FIG. 8A is a longitudinal sectional view (corresponding to the concentration distribution in the ignition chamber 8 in FIG. 7) showing the concentration distribution of the fuel G of the air-fuel mixture M in the ignition chamber 8 according to the reference example , FIG. FIG. 8B is a cross-sectional plan view showing the concentration distribution in the ignition space portion in FIG.
In the figure, in the air-fuel mixture M, the portion where the concentration of the fuel G is dark is shown in black, and the thin portion is shown in white, and the black region shows that there are many unburned residual gases having a lower oxygen concentration.

When the spark plug 7 having the plurality of injection holes 10 according to the reference example is used, as shown in FIG. 8 (a), the injection holes 10 are moved from the combustion chamber 1 below the FIG. 8 (a). The air-fuel mixture M (shown in FIG. 8 (a) as a white region where the concentration of the fuel G is relatively low, ie, the concentration of the air A is relatively high) flows into the throat space 8a of the ignition chamber 8, It turns out that it flows in the direction along the central axis X of this throat space part 8a, and flows in into the ignition space part 8b expanded in diameter in this direction. The air-fuel mixture M flows in a direction along the side wall surface, which is the radial end of the throat space 8a and the ignition space 8b, and forms a tumble flow T extending in the vertical direction in the ignition space 8b. Yes. In particular, the tumble flow T has a large gas flow not only in the vertical direction but also in the horizontal direction of the ignition space 8b, resulting in a larger tumble flow T. Therefore, a larger tumble flow T is formed in the ignition space portion 8b, and the tumble flow T is guided in the vicinity of the ignition point P, and further promotes mixing in the vicinity of the upper portion of the ignition space portion 8b. It can be seen that even at the ignition point P arranged on the central axis Y, an area where the concentration of the fuel G is relatively thin is formed. That is, it can be confirmed that there is almost no unburned residual gas in the vicinity of the ignition point P (see FIG. 8B).
Therefore , in the reference example , an area where the concentration of the fuel G is relatively high (an area where the concentration of the air A is relatively low) is prevented from being formed in the upper portion of the ignition space 8a, particularly in the vicinity of the ignition point P. Misfire at the ignition point P of the spark plug 7 can be prevented.
In the spark plug 7, the thickness of the plug cover 7b near the nozzle hole 10 is 1.5 mm, the inner diameter (diameter) of the throat space 8a is 4 mm, the length of the cylinder is 11 mm, and the inner diameter of the ignition space 8b. (Diameter) is 9 mm, and the distance D between the central axis Y of the throat space 8a and the central axis X of the ignition space 8b is 0.5 mm (the ratio D / of the inner diameter (diameter R) of the ignition space and the distance D) The simulation was performed by setting R to 0.2), the inflow direction of the nozzle hole 10 to an angle (β) of 45 degrees, and the number of nozzle holes 10 to four .

[Another embodiment]
(1) In the above-described embodiment, city gas is used as the fuel G. However, the present invention is not limited to this, and gaseous fuel other than hydrocarbons mainly composed of CO and H ₂ such as hydrogen and propane other than city gas is used. Even if it is a case, the outstanding effect can be exhibited. Moreover, fuel other than gaseous fuel can also be utilized as the fuel G, for example, arbitrary fuels, such as gasoline, alcohol, methanol, ethanol, can be used.

(2) In the above embodiment, as shown in FIG. 3, the ignition point P of the spark plug 7 is disposed on the central axis Y of the ignition space 8b. It is also possible to arrange the ignition point P at a location that is well performed.

(3) In the above embodiment, as shown in FIG. 3 , the angle β is set upward with respect to the straight line connecting the ignition chamber side end L and the central axis X in the inflow direction of the plurality of injection holes 10. When the ignition point P is below the ignition chamber side end L of the hole 10, the ignition chamber side end L and the central axis X are connected so that the air-fuel mixture M can be guided to the ignition point P satisfactorily. The angle β may be set downward with respect to the straight line.

(4) In the above embodiment, the four nozzle holes 10 are provided in the plug cover 7 b as the plurality of nozzle holes 10, but the ignition chamber 8 (the throat space 8 a and the ignition space from the combustion chamber 1 through the nozzle hole 10. If the air-fuel mixture M can be satisfactorily introduced into the portion 8b), the number of nozzle holes may be changed as appropriate.

(5) In the above embodiment, when the plurality of injection holes 10 are formed in the plug cover 7b, the spherical bottomed portion formed in the bottomed cylindrical shape of the throat space 8a formed by the plug cover 7b is used. Although arranged at equal intervals on the same circumference, if the gas flow flowing along the central axis X can be formed in the ignition chamber 8, the same circle is not given on the same circumference. A plurality of nozzle holes can be arranged at different intervals on the circumference. In addition, in the spherical bottomed portion formed in the bottomed cylindrical shape of the throat space 8a formed by the plug cover 7b, not only in the same circumferential direction but also on a plurality of circumferences at different positions in the radial direction It is also possible to arrange a plurality of nozzle holes at regular intervals or at different intervals.

(6) In the above embodiment, the spark plug 7 is configured by integrally configuring the plug body 7a and the plug cover 7b. However, the present invention is not limited thereto, and the plug body 7a and the plug cover 7b are used as separate members. It is also possible to configure the spark plug 7 by combining them.

(7) In the above embodiment, the cylinder head 6 is provided with two valves of the intake valve 4 and the exhaust valve to form a two-valve engine, but the number of valves is not particularly limited, and the four-valve type It is possible to use the engine of the present application by appropriately changing the number of change valves, such as an 8-valve or the like.

(8) In the above-described embodiment, the ignition chamber side end portion L is set to the straight direction in which the ignition chamber side end portion L and the central axis X are connected in the cross section orthogonal to the central axis X of the throat space portion 8a. Although the shaft is set to deviate by a predetermined angle β toward the side closer to the ignition point P, the angle β is not limited to this as long as the tumble flow T can be satisfactorily formed in the ignition space 8b. In the cross section perpendicular to the central axis Y of the ignition space 8b, with respect to the direction of the straight line connecting the ignition chamber side end L and the central axis Y to the ignition point P with the ignition chamber side end L as an axis. It may be set on the approaching side.

  The engine according to the present invention is an engine in which the air-fuel mixture flowing from the combustion chamber into the ignition chamber through the injection hole is spark-ignited at the ignition point by the ignition plug, and the misfire is surely guided to the ignition point. It can be effectively used as an engine that can suppress and obtain a stable combustion flame and realize stable operation.

Longitudinal sectional view of a plane parallel to the central axis Y of the ignition space of the cylinder top and the cylinder head lower periphery of an engine according to implementation embodiments of the present application Top sectional view of the II-II plane perpendicular to the central axis X of the throat space near the ignition chamber in FIG. Fig. 1 is an enlarged longitudinal sectional view of the vicinity of the ignition chamber (A) Longitudinal sectional view showing the concentration distribution of fuel in the air-fuel mixture in the ignition chamber according to the embodiment of the present application, (b) Flat sectional view showing the concentration distribution in the ignition space portion in FIG. Vertical sectional view of a plane parallel to the central axis Y of the ignition space in the periphery of the cylinder upper portion and the cylinder head lower portion of the engine according to the reference example 5 is a cross-sectional plan view of the VI-VI plane perpendicular to the central axis X of the throat space near the ignition chamber. FIG. 5 is an enlarged longitudinal sectional view in the vicinity of the ignition chamber. (A ) Longitudinal sectional view showing fuel concentration distribution of air-fuel mixture in ignition chamber according to reference example , (b) Flat sectional view showing concentration distribution in ignition space in FIG. 8 (a) (A) Longitudinal sectional view showing fuel concentration distribution of air-fuel mixture in ignition chamber according to comparative example, (b) Flat sectional view showing concentration distribution in ignition space in FIG. 9 (a)

Explanation of symbols

1: Combustion chamber 2: Piston 2a: Recessed portion 3: Cylinder 6: Cylinder head 7: Spark plug 7a: Plug body 7b: Plug cover 8: Ignition chamber 8a: Throat space 8b: Ignition space 10: Injection hole 100, 200 : Engine G: Fuel A: Air M: Air-fuel mixture X: Center axis Y of throat space portion: Center axis of ignition space portion P: Ignition point T: Tumble flow L: Ignition chamber side end α: Angle

Claims (5)

A spark plug in which an ignition chamber is formed in a plug cover that covers the ignition point is mounted on the cylinder head, and a plurality of nozzle holes that communicate the ignition chamber and the combustion chamber facing the piston are provided in the plug cover. An engine,
The ignition chamber is composed of a throat space provided with the nozzle hole, and an ignition space provided with the ignition point while extending to the cylinder head side in a state communicating with the throat space,
An engine in which an inner diameter of the throat space is smaller than an inner diameter of the ignition space, and a center axis of the throat space is set to intersect with a center axis of the ignition space.   The engine according to claim 1, wherein the ignition point is arranged on an upper portion in the ignition space portion and on a central axis of the ignition space portion. A concave portion is formed on the top surface of the piston facing the cylinder head, and at least the plug cover is disposed so as to enter the concave portion in a state where the piston is located at a top dead center. The engine according to claim 1, wherein the engine is disposed on a side entering the concave portion from a top surface.   A plug body having an ignition point; and a plug cover provided on the plug body so as to cover the ignition point;
  An engine ignition plug in which a plurality of injection holes communicating with a combustion chamber facing a piston and an ignition chamber formed in the plug cover are formed in the plug cover in a state of being mounted on a cylinder head of the engine Because
  The ignition chamber is composed of a throat space provided with the nozzle hole, and an ignition space provided with the ignition point while extending to the cylinder head side in a state communicating with the throat space,
  An engine ignition plug in which an inner diameter of the throat space portion is formed smaller than an inner diameter of the ignition space portion, and a central axis of the throat space portion is set to intersect with a central axis of the ignition space portion . The engine spark plug according to claim 4, wherein the plug cover is formed integrally with the plug body.