JP7226638B2 - pre-chamber engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-chamber engine having a system for igniting an air-fuel mixture in a main chamber by ejecting a flame formed by igniting an air-fuel mixture in the pre-chamber into the main chamber.

In an engine, a sub-combustion chamber (also referred to as a sub-chamber) separated from a main combustion chamber (also referred to as a main chamber) by a partition is provided, and a communication passage that communicates the main chamber and the sub-chamber with each other is formed in the partition, Equipped with a system (also called a jet ignition system) that ignites the air-fuel mixture in the pre-chamber and ignites the air-fuel mixture in the main chamber so that the flame formed in the pre-chamber at this time jets out into the main chamber through a communication passage. A pre-chamber type engine is also known (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-204835

By the way, the fuel supply mode of the jet ignition system as described above includes a passive system in which fuel is supplied into the pre-chamber via the main chamber and an active system in which fuel is supplied directly into the pre-chamber.

In the devising process of this case, the configuration shown in FIG. 7 was conceived as a pre-chamber engine equipped with a passive jet ignition system. That is, as shown in FIG. 7, a partition wall 123 is arranged in a region including the central axis of the bore in the upper part of the main chamber 121 (the ceiling wall portion on the side of the cylinder head 103) to partition and form the sub chamber 122 therein. The injector 117 is arranged on the side wall portion 111a of 121 . A plurality of communication passages 124 are formed in the partition wall 123 to communicate the main chamber 121 and the sub chamber 122, and one of the communication passages 124 is used as a fuel supply passage 124a. The injector 117 is arranged so that the direction of fuel injection is toward the fuel supply passage 124a.

In the case of such a passive system, fuel can be easily supplied to the pre-chamber by injecting fuel at the timing of the compression stroke. However, as shown in FIG. 7, part of the fuel injected from the injector 117 does not enter the sub-chamber 122, but passes along the outer surface of the partition wall 123 (the wall of the sub-chamber 122) and reaches the center of the bore. It reaches the opposite side of the injector 117 across the axis and forms a rich air-fuel mixture. When this rich air-fuel mixture becomes close to the stoichiometric mixture ratio, a large amount of NOx is generated, which poses a problem.

The present invention was devised with a focus on such problems. In a pre-chamber type engine equipped with a passive jet ignition system, the fuel can be easily introduced into the pre-chamber, especially near the cylinder head, to reduce NOx emissions. One of the purposes is to be able to suppress the generation. In addition to this purpose, it is also another object of the present invention to achieve functions and effects that are derived from each configuration shown in the embodiments for carrying out the invention described later and that cannot be obtained by the conventional technology. be.

The present pre-chamber type engine includes a main chamber, a pre-chamber separated from the main chamber by a partition provided in a cylinder head, and a plurality of connections provided in the partition for communicating the main chamber and the pre-chamber. a passage, a fuel injection valve mounted on the wall of the main chamber for injecting fuel into the main chamber; and a fuel inflow communicating passage for introducing fuel into the pre-chamber, wherein the flame formed in the pre-chamber by the ignition of the air-fuel mixture in the pre-chamber is jetted into the main chamber through the communication passage to cause the flame to flow into the main chamber. A pre-chamber engine that ignites an air-fuel mixture, wherein the partition has an outer partition wall surface on the side of the main chamber and an inner partition wall surface on the side of the auxiliary chamber, and the fuel inflow at the outer surface of the partition wall A concave portion having a receiving surface against which the directly injected fuel from the fuel injection valve collides is formed around the opening of the communicating passage, and the intersection of the axis of the fuel inflow communicating passage and the inner surface of the partition wall is the fuel It is characterized by being closer to the cylinder head than the intersection of the axial center line of the directly injected fuel from the injection valve and the surface of the inner surface of the partition wall facing the fuel injection valve.

It is preferable that the fuel inflow communication passage is inclined from the opening into the auxiliary chamber toward the cylinder head as it approaches an axial center in the auxiliary chamber.
It is preferable that the recess is formed in a shape that gradually decreases in diameter in a direction from the outside to the inside of the pre-chamber.
The opening is preferably arranged at a position offset from the center of the receiving surface.
In this case, the recess extends in a first direction along the axial direction of the pre-chamber. The distance from the other end to the communication path is set to be different from the other end side portion, and the one end side portion and the other end side portion are formed into curved surfaces with different curvatures in the first direction. It is preferable that
The recess extends in a first direction along the axial direction of the pre-chamber and in a second direction perpendicular to the first direction, and the fuel injected from the fuel injection valve reaches the recess. It is preferable that the maximum spread width of the fuel in the second direction at is set smaller than the external width of the pre-chamber in the second direction.

According to this invention, since the fuel injected into the main chamber collides with the receiving surface of the recess on the outer side of the pre-chamber, the splitting and vaporization of the fuel can be promoted, and the fuel flows from the fuel inflow communication passage into the pre-chamber through the recess. Can promote adoption. In addition, since the intersection of the axis of the fuel inflow communication passage and the inner surface of the pre-chamber is closer to the cylinder head than the intersection of the axis of the direct injection fuel and the inner surface of the pre-chamber, It becomes easier to introduce fuel near the cylinder head in the auxiliary chamber.

1A to 1C are diagrams showing the configuration of a combustion chamber of one cylinder of a pre-combustion chamber engine according to an embodiment, FIG. 1A being a longitudinal sectional view thereof, FIG. 1B being a top view thereof, and FIG. 1C being a partition wall thereof. 1 is an enlarged vertical cross-sectional view of FIG. 2 is a partial cross-sectional view of the pre-chamber of the pre-chamber engine shown in FIG. 1. FIG. 3A and 3B are perspective views showing modifications of the shape of the recess of the pre-chamber of the pre-chamber type engine shown in FIGS. 1A to 1C, FIG. 3A showing the first modification, and FIG. A modification is shown. 4A to 4C are diagrams showing the shape of a third modification of the concave portion of the pre-chamber of the pre-chamber type engine shown in FIGS. 1A to 1C, FIG. FIG. 4C is a longitudinal cross-sectional view of the recess (enlarged view of essential parts in FIG. 4A), and FIG. 4C is a front view of the recess. 1C is a cross-sectional view showing the relationship between the pre-chamber, its recessed portion, and the fuel injection range of the pre-chamber engine shown in FIGS. 1A to 1C. FIG. 6A to 6C are vertical cross-sectional views of the combustion chamber showing the fuel injection mode of the pre-chamber engine shown in FIGS. 1A to 1C in the order of strokes shown in FIGS. 6A to 6C. FIG. 7 is a vertical cross-sectional view of a combustion chamber for explaining the subject of this case.

A pre-chamber engine as an embodiment will be described below with reference to the drawings. The embodiments shown below are merely examples, and are not intended to exclude various modifications and application of techniques not explicitly described in the embodiments below. Each configuration of this embodiment can be modified in various ways without departing from the gist thereof. Also, they can be selected or combined as needed.

[overall structure]
A pre-chamber engine (an internal combustion engine including a gasoline engine and a diesel engine; hereinafter also simply referred to as "engine") 1 according to the present embodiment is a multi-cylinder engine, and each cylinder is shown in FIG. 1A. , a cylinder 11 formed in the cylinder block 2, a piston 12 reciprocating in the cylinder 11, an intake port 13 and an exhaust port 14 formed in the cylinder head 3, and an intake valve provided in the intake port 13. 15 and an exhaust valve 16 attached to the exhaust port 14 .
In this embodiment, as shown in FIG. 1B, two each of the intake ports 13 (intake valves 15) and the exhaust ports 14 (exhaust valves 16) are provided. ) and the number of exhaust ports (the number of exhaust valves) are not limited to these.

A combustion chamber 20 is defined by the inner wall of the cylinder 11 , the top surface 12 a of the piston 12 , and the cylinder head 3 on the cylinder head 3 side (upper part in the figure) in the cylinder 11 . An intake port 13 that is opened and closed by an intake valve 15 and an exhaust port 14 that is opened and closed by an exhaust valve 16 are connected to the combustion chamber 20 so as to be able to communicate with each other. Here, the top portion of the combustion chamber 20 is formed in a pent roof shape having an intake slope on which the intake valve 15 is provided and an exhaust slope on which the exhaust valve 16 is provided.

A fuel injection valve 17 is provided on a peripheral wall 11a at the top (upper portion in FIG. 1A) of the cylinder 11, and the engine of the present embodiment is a direct injection engine (1) that directly injects fuel into the cylinder 11 ( It is configured as a direct injection engine). In this embodiment, only the fuel injection valve 17 that directly injects fuel into the cylinder 11 is provided, but in addition to this, a fuel injection valve for port injection that injects fuel into the intake port 13 may be added. .

The engine according to the present embodiment is a spark ignition engine, and at the top (here, the top of the pent roof shape) 20a of the combustion chamber 20, which is a part of the cylinder head 3, the bore center axis or the vicinity of the bore center axis. A spark plug 18 is provided in the combustion chamber 20 with a spark discharge portion 18a exposed. However, the engine according to this case also includes a compression ignition engine without the spark plug 16 . When the spark plug 18 ignites the air-fuel mixture, it is usually called "ignite", but here, the term "ignite" or "ignite" is used in the sense of including compression ignition.

[Configuration of main room and auxiliary room]
A top portion 20 a of the combustion chamber 20 is provided with a partition wall 23 that partitions the internal space of the combustion chamber 20 into a main chamber (main combustion chamber) 21 and a sub chamber (sub combustion chamber) 22 . The partition 23 is arranged to cover the space where the spark discharge portion 18a of the spark plug 18 is exposed, and the internal space (space including the spark discharge portion 18a) covered by the partition 23 in the combustion chamber 20 is the auxiliary chamber 22. The space outside the partition wall 23 in the combustion chamber 20 serves as the main chamber 21 .

As shown in FIG. 1C, the partition wall 23 is formed with a plurality (seven in the present embodiment) of communication passages (also referred to as “nozzles”) 24 that communicate with the main chamber 21 and the sub chamber 22 . A part (here, one) of the plurality of communicating passages 24 is a fuel inflow communicating passage for introducing fuel injected into the main chamber 21 from the fuel injection valve 17 into the auxiliary chamber 22. 24a.
The fuel injection valve 17 has an injection port for supplying fuel into the auxiliary chamber 22 .

In the pre-chamber 22, the air-fuel mixture containing the fuel introduced through the fuel inflow communication passage 24a is ignited at a predetermined timing by the spark plug 18, and a plurality of flames are formed in the pre-chamber 22 by this ignition. The air-fuel mixture is jetted into the main chamber 21 through the communication passage 24 to ignite the air-fuel mixture in the main chamber 21 and promote combustion. Such an ignition system, also called a jet ignition system, is effective in igniting a lean air-fuel mixture and promoting combustion, and can be applied during lean burn and large EGR in the main chamber 21, thereby improving fuel efficiency. Become.

By the way, in the main chamber 21 side surface (partition wall outer surface) 23a of the partition wall 23, the axis of the sub chamber 22 in which the main chamber 21 and the sub chamber 22 are formed is formed around the opening 24b through which the fuel inflow communication passage 24a opens. A concave curved surface 30CF curved along a direction (first direction) D1 along the direction and a direction (second direction) D2 perpendicular to the first direction D1, and a fuel injection valve formed in the concave curved surface 30CF A concave portion 30 having a receiving surface 30F against which the direct injection fuel from 17 collides is formed. The wall surface (inner wall surface) of the recess 30 of the present embodiment includes a concave curved surface 30CF, and is formed in a mortar shape with a smooth curved surface that gradually decreases in diameter from the outside to the inside of the auxiliary chamber 22. However, the shape of the recess 30 is not limited to this. The opening 24b is arranged at or near the bottom of the mortar-shaped recess 30 .

Further, the axial center line FL2 of the fuel inflow communicating passage 24a (that is, the flow channel center line of the fuel inflow communicating passage 24a) is different from the axial center line FL1 of the fuel directly injected from the fuel injection valve 17, The intersection point P1 with the chamber 22 side surface (partition wall inner surface) 23b is positioned closer to the cylinder head 3 than the intersection point P2 between the axial center line FL1 of the directly injected fuel and the surface of the partition wall inner surface 23b facing the fuel injection valve 17. is formed in When the axis FL2 of the fuel inflow communication passage 24a coincides or substantially coincides with the axis FL1 of the directly injected fuel from the fuel injection valve 17, the directly injected fuel directly enters the auxiliary chamber 22 through the fuel inflow communication passage 24a. Therefore, the fuel enters the pre-chamber 22 in a state of insufficient splitting and vaporization, which is disadvantageous for subsequent mixing with air in the pre-chamber 22 . However, if the axis FL2 of the fuel inflow communication passage 24a and the axis FL1 of the directly injected fuel from the fuel injection valve 17 are not aligned, the directly injected fuel is directly injected into the auxiliary chamber 22 through the fuel inflow communication passage 24a. The fuel enters the pre-chamber 22 in a not a little split or vaporized state, and contributes to subsequent mixing with air in the pre-chamber 22 . Here, the axis FL2 is not parallel to the axis FL1 (that is, the angle is different), but even if the axis FL2 and the axis FL1 are parallel, the fuel inflow communication passage 24a The intersection point P1 between the axis FL2 and the partition wall inner surface 23b is formed to be closer to the cylinder head 3 than the intersection point P2 between the axis FL1 of the direct injection fuel and the surface of the partition wall inner surface 23b facing the fuel injection valve 17. It is good if it is.

In this embodiment, the upper portion of the partition wall 23 (the upper portion in FIG. 1C (that is, the ignition plug side)) is formed in a cylindrical shape, and the lower portion of the partition wall 23 (the lower portion in FIG. 1C (that is, the piston 12 side)) is formed in a substantially hemispherical shape. formed. Moreover, the partition 23 is formed in the shape of a body of revolution centered on the position of the spark discharge portion 18a of the spark plug 18 (that is, the bore central axis or a position in the vicinity of the bore central axis), except for a part. However, the shape of the partition 23 is not limited to this. The upper portion preferably has a cylindrical shape centered on the spark discharge portion 18a of the spark plug 18, but the lower portion may be continuous with the upper cylindrical shape, and may have a shape in which the diameter decreases as it goes downward and the cross-sectional area gradually decreases. .

[Structure of concave part of pre-chamber]
In this embodiment, the recessed portion 30 is formed on a sloped portion of the substantially hemispherical portion of the lower portion of the partition wall 23 that is deviated from the pre-chamber center axis CL. Therefore, the lower portion of the partition wall 23 is formed in a substantially hemispherical shape, except for the portion where the recess 30 is formed.

Further, in this embodiment, the recesses 30 are formed in the lower portions of the partition walls 23 while keeping the thickness substantially uniform. A convex portion 31 corresponding to is formed. However, the recessed portion 30 may be formed by cutting the outer surface (outer partition wall surface) 23a of the auxiliary chamber 22. For example, the recessed portion 30 is formed in the outer partition wall surface 23a while the inner surface of the partition wall 23 maintains a substantially hemispherical shape. You may In this case, the thickness of the portion where the concave portion 30 is formed is reduced.

FIG. 2 is a partial cross-sectional view (part of the cross section taken along a plane perpendicular to the center axis CL of the pre-chamber) of the pre-chamber 22 where the recess 30 is formed. , and the fuel is injected from the top in the drawing. As indicated by arrows A1 to A3 in FIG. 2, the shape of the inner wall surface of the recess 30 here is such that the diameter gradually decreases in the direction from the outside to the inside of the pre-chamber 22 . In other words, as indicated by arrows A4 to A7 in FIG. 2, the depth of the recess 30 in the cross section from the center CL1 toward the center axis CL of the pre-chamber gradually decreases outward.

In the present embodiment, as shown in FIGS. 1C and 2 , with respect to the face center (geometric center in front view) GL of the recess 30 in front view (see FIG. 1C ), It is formed in a symmetrical or substantially symmetrical curved surface shape both in the direction (first direction) D1 and in the direction (second direction) D2 perpendicular to the first direction D1 (the direction perpendicular to the pre-chamber central axis CL). .

However, the shape of the wall surface of the recess 30 is not limited to this. It may be (funnel) shaped. That is, it may be formed using a conical surface like the recessed portion 30A shown as a modified example in FIG. 3A, or may be formed using a pyramidal surface like the recessed portion 30B shown as a modified example in FIG. 3B. Although the example shown in FIG. 3C uses a square pyramidal surface, other pyramidal surfaces are also applicable. Further, it is more preferable if the shape includes the concave curved surface 30CF curved along the first direction D1.

Also, when a conical surface is used as the shape of the wall surface of the recess 30, the wide side B of the conical surface (corresponding to the opening of the recess 30) and the narrow side T of the conical surface (corresponding to the bottom surface of the recess 30) are It is not limited to circles and regular polygons, and may be ellipses or other polygons.
Furthermore, like the recesses 30A and 30B shown in FIGS. 3A and 3B, lines (L1 and L2 in FIGS. 3A and 3B) connecting the center of the wide side B and the center of the narrow side T of the conical surface are An inner surface shape of a frustum that is inclined with respect to the bottom surface B and the top surface T of the frustum (that is, a frustum in which the top surface T is laterally displaced with respect to the bottom surface B) may be applied. In FIGS. 3A and 3B, recesses 30A and 30B are shown obliquely downward in correspondence with FIGS. 1A and 1B.

In the modification shown in FIGS. 3A and 3B, the opening 24b of the fuel inflow communication passage 24a is arranged at the deepest portion (bottom portion) of the recesses 30A and 30B, but the arrangement of the opening 24b is limited to this. do not have. Also, the number of openings 24b (the number of fuel inflow communication passages 24a) is not limited to one. A plurality of (here, two) openings 24b may be provided like the recess 30B shown in FIG. 3B. In this case, the direction in which the openings 24b are arranged may be the first direction D1 or the second direction D2.

A receiving surface 30F is formed at the center of the fuel injection range from the fuel injection valve 17, and in the present embodiment, the opening 24b extends in a first direction along the axial direction of the pre-chamber 22, as shown in FIG. 1C. At D 1 , it is arranged at a position shifted from the center of the fuel injection range from the fuel injection valve 17 . In this embodiment, as shown in FIG. 2, the opening 24b is positioned substantially along the center of the fuel injection range from the fuel injection valve 17 in the second direction D2 perpendicular to the first direction D1. are placed. As a result, the fuel injected from the fuel injection valve 17 does not directly enter the opening 24b, but enters the opening 24b after being temporarily received by the receiving surface 30F.

When the center of the fuel injection range is at the center (geometric center in front view) GL of the recess 30 in front view, the opening 24b is arranged at a position shifted from the center GL in front view. In this embodiment, the center of the fuel injection range is slightly shifted downward (that is, toward the piston 12) in FIG. It is slightly shifted upward (that is, toward the cylinder head 3) in FIG. 1C with respect to the visual center GL. The direction in which the opening 24b deviates from the center of the fuel injection range is not limited to this. For example, as shown in FIG. 3B, when a plurality of openings 24b are provided, the openings 24b may be arranged around the center of the fuel injection range so as to surround the center of the fuel injection range.

The axis FL2 of the fuel inflow communication passage 24a is indicated by a dashed line, but the axis FL2 of the fuel inflow communication passage 24a extends from the opening 24b into the sub chamber 22 toward the sub chamber central axis in the sub chamber 22. As it approaches CL, it is inclined upward (that is, toward the cylinder head 3 side) in FIG. 1C. The inflow direction of the fuel in the fuel inflow communication passage 24a is the direction in which the spark discharge portion 18a of the upper spark plug 18 in the auxiliary chamber 22 is approached.

The recess 30 extends in a first direction D1 along the axial direction of the pre-chamber 22 and in a second direction D2 perpendicular to the first direction D1. Like 30C, in the first direction D1, a distance (wall length) of a portion (one end side portion) P1 from one end of the recess 30 (lower end in FIGS. 4A to 4C) to the fuel inflow communication passage 24a d1 and the distance (wall length) d2 of the portion (the other end side portion) P2 from the other end of the recess 30 [upper end in FIGS. In the first direction D1, the one end portion P1 and the other end portion P2 may be formed into curved surfaces having different curvatures.

In this modification, as shown in FIGS. 4B and 4C, the opening 24b of the fuel inflow communication passage 24a is arranged at a position displaced upward (that is, toward the cylinder head 3) from the front view center GL of the recess 30. be. In other words, of the distances from the opening 24b to various parts of the periphery of the recess 30, the distance d1 of the one end side portion P1 having the receiving surface 30F from the opening 24b to one end of the recess 30 is the maximum. The distance d2 of the other end side portion P2 to the other end of the recess 30 is set to the minimum.

Further, the center of the range of fuel injection into the recess 30 is set at a position deviated downward (that is, toward the piston 12) from the center GL of the recess 30 in a front view.
Further, as shown in FIG. 4B, the curved surface forming the concave portion 30 has a larger curvature 1/R2 at the other end portion P2 than the curvature 1/R1 at the one end portion P1 having the receiving surface 30F ( That is, the radius of curvature R2 of the portion P2 on the other end side is smaller than the radius of curvature R1 of the portion P1 on the one end side. The curvature of the one end portion P1 and the curvature of the other end portion P2 may be uniform, but the curvature may vary partially or entirely, for example, from one end of the recess 30 to the other end. You may form so that a curvature may become large gradually (curvature radius becomes small) toward it.

As shown in FIG. 5, the fuel injected from the fuel injection valve 17 gradually diffuses at a predetermined angle α. The spread width (maximum spread width) W1 in the two directions D2 is set smaller than the external width W2 of the pre-chamber 22 in the second direction D2 (that is, W2>W1).

[Fuel injection and combustion]
In this embodiment, fuel is injected from the fuel injection valve 17 into the main chamber 21 at the beginning of the intake stroke (see FIG. 6A), and then from the fuel injection valve 17 into the sub chamber 22 via the main chamber 21 at the end of the compression stroke. is injected [see FIG. 6B]. When the port injection is employed, the port injection is performed in the exhaust stroke or the intake stroke, and the fuel is supplied into the main chamber 21 together with the intake air in the intake stroke. At the end of the compression stroke, the air-fuel mixture formed in the pre-chamber 22 is ignited, and the flame formed in the pre-chamber 22 by this ignition is jetted into the main chamber 21 through a plurality of communication passages 24. to ignite and burn the air-fuel mixture in the main chamber 21 (see FIG. 6C).

[Action and effect]
According to the pre-chamber engine according to the present embodiment, when fuel is injected from the fuel injection valve 17 into the pre-chamber 22 through the main chamber 21 at the end of the compression stroke, the injected fuel is injected into the opening 24b. Without direct entry, or with direct entry suppressed, it collides with the receiving surface 30F in the concave curved surface 30CF of the recess 30 and is received. Therefore, the direct-injected fuel is accelerated to split and vaporize while staying in and near the recess 30, and then introduced into the auxiliary chamber 22 from the opening 24b through the fuel inflow communication passage 24a. The splitting and vaporization of the fuel in this recess 30 contributes to the promotion of subsequent mixing with air in the pre-chamber 22 . Further, if the fuel enters directly into the opening 24b, the splitting and vaporization of the fuel may become insufficient, but this is also avoided.

Furthermore, the intersection point P1 between the axis FL2 of the fuel inflow communication passage 24a and the partition wall inner surface 23b is located closer to the cylinder than the intersection point P2 between the axis FL1 of the direct injection fuel and the surface of the partition wall inner surface 23b facing the fuel injection valve 17. Since it is formed on the head 3 side, it becomes easier to introduce the fuel into the auxiliary chamber 22 closer to the cylinder head 3 . In other words, it becomes easy to form a fuel-rich air-fuel mixture intensively in the vicinity of the spark discharge portion 18a in the upper portion of the auxiliary chamber 22 . As a result, the ignition by the spark plug 18 and the subsequent flame formation in the pre-chamber 22 are enhanced.

Further, when the axial direction of the pre-chamber 22 (the direction of the pre-chamber center axis CL) coincides with the axial direction of the bore center axis (the axial direction of the cylinder), the concave curved surface 30CF is aligned with the axis of the pre-chamber 22. The first direction D1 along the direction, that is, the axial direction of the cylinder (the direction of the bore center axis) is curved. Directly injected fuel that has collided with 30F can be guided along the concave curved surface 30CF from the opening 24b to the fuel inflow communication passage 24a.

Further, as shown in FIG. 4C, if the distance d1 of the one end side portion P1 having the receiving surface 30F is set to the maximum in the first direction D1 along the axial direction of the pre-chamber 22, the receiving surface 30F is increased. In addition, when the curvature of the end side portion P1 is set small, the direct injection fuel is further promoted to split and vaporize while staying in and near the recess 30, and the subsequent fuel in the pre-chamber 22 is accelerated. Contributes to promoting mixing with air.

In this manner, the directly injected fuel is caught in the recess 30 and proceeds from the opening 24b to the fuel inflow communication passage 24a. Therefore, as shown in FIG. It is suppressed from passing along the outer surface of the partition wall 23 (the wall of the sub chamber 12) without entering inside, and it is avoided or suppressed from reaching the opposite side of the injector 17 and forming a rich air-fuel mixture. . Therefore, generation of a large amount of NOx due to a rich air-fuel mixture is avoided or suppressed.

In addition, since the opening 24b of the fuel inflow communication passage 24a is arranged at or near the bottom of the recess 30, the fuel that has collided with the receiving surface 30F and has been accelerated to split or vaporize will reach the inner wall surface of the recess 30. Along the way, the fuel smoothly flows into the auxiliary chamber 22 from the opening 24b through the fuel inflow communicating passage 24a.

Since the fuel inflow communication passage 24a is inclined in a direction toward the spark discharge portion 18a of the spark plug 18, the fuel passing through the fuel inflow communication passage 24a flows toward the spark discharge portion 18a above the auxiliary chamber 22, and flows toward the spark discharge portion 18a. A fuel-rich air-fuel mixture is concentrated in the vicinity of 18a. Therefore, the ignition by the ignition plug 18 and the flame formed in the pre-chamber 22 thereafter can be strengthened, and a strong jet is ejected into the main chamber 21 through the plurality of communication passages 24 to mix the fuel in the main chamber 21. It can ignite air and promote combustion.

Further, as shown in FIG. 5, the fuel injected from the fuel injection valve 17 gradually diffuses at a predetermined angle α. The spread width W1 in the second direction D2 of the pre-chamber 22 is set smaller than the external width W2 in the second direction D2 of the pre-chamber 22. can be suppressed, contributing to the effect of reducing NOx emissions.

[others]
The configuration of the pre-chamber engine described above is an example. For example, the arrangement of the pre-chamber 22, that is, the partition wall 23 that partitions the pre-chamber 22 is not necessarily limited to the bore center axis CL of the top portion 20a of the combustion chamber 20 or the vicinity of the bore center axis CL. is also not limited to
Further, the fuel injection valve 17 may have an injection port for supplying fuel to the main chamber 21 in addition to the injection port for supplying fuel to the sub chamber 22 .
Further, although only one fuel inflow communication passage 24a is provided in the above embodiment, a plurality of fuel inflow communication passages 24a may be provided in the recess 30. FIG.

In the above-described embodiment, the concave portion 30 has a mortar shape formed with a smooth curved surface or a funnel shape using a conical surface, but the shape of the concave portion 30 is not limited to this.
Furthermore, in the above-described embodiment, the opening 24b is arranged at or near the bottom of the recess 30, but if the inner surface shape of the recess 30 is a shape that can guide the fuel received by the receiving surface 30F to the opening 24b, , the opening 24b may be arranged at or near the bottom of the recess 30 .

1 pre-chamber engine (engine)
2 Cylinder Block 3 Cylinder Head 11 Cylinder 12 Piston 13 Intake Port 14 Exhaust Port 15 Intake Valve 16 Exhaust Valve 17 Fuel Injection Valve 18 Spark Plug 18a Spark Discharge Unit 20 Combustion Chamber 20a Top of Combustion Chamber 20 21 Main Chamber (Main Combustion Chamber)
22 sub-chamber (sub-combustion chamber)
23 partition wall 23a partition wall outer surface 23b partition wall inner surface 24 communication path (nozzle)
24a Fuel inflow communication passage (nozzle)
24b Openings of fuel inflow communication passage 24a 30, 30A, 30B, 30C Concave portion 30CF Concave curved surface 30F Receiving surface 31 Convex portion CL Pre-chamber central axis FL1 Axis of direct injection fuel FL2 Axis of fuel inflow communication passage 24a P1 Intersection point of the axis FL2 of the fuel inflow communication passage 24a and the partition wall inner surface 23b P2 Intersection point of the direct injection fuel axis FL1 and the surface of the partition wall inner surface 23b facing the fuel injection valve 17

Claims (6)

a main chamber, an auxiliary chamber separated from the main chamber by a partition provided in a cylinder head, a plurality of communication passages provided in the partition and communicating the main chamber and the auxiliary chamber, and a wall of the main chamber a fuel injection valve that injects fuel into the main chamber; and a fuel inflow connection that is a part of the plurality of communication passages and introduces the fuel injected from the fuel injection valve into the sub chamber. a passageway;
A pre-chamber engine that ignites the air-fuel mixture in the main chamber by ejecting a flame formed in the pre-chamber by the ignition of the air-fuel mixture in the pre-chamber into the main chamber through the communication passage,
The partition wall has an outer partition wall surface on the main chamber side and an inner partition wall surface on the sub chamber side,
A concave portion having a receiving surface against which the directly injected fuel from the fuel injection valve collides is formed around the opening of the fuel inflow communication passage in the outer surface of the partition wall,
The intersection of the axis of the fuel inflow communication passage and the inner surface of the partition wall is located above the intersection of the axis of the fuel directly injected from the fuel injection valve and the surface of the inner surface of the partition facing the fuel injection valve. A pre-chamber engine characterized by being on the cylinder head side. 2. The fuel inflow communication passage is slanted from the opening into the auxiliary chamber toward the cylinder head as it approaches the axial center of the auxiliary chamber. pre-chamber engine. 3. The pre-chamber type engine according to claim 1, wherein said recess is formed in a shape that gradually decreases in diameter in a direction from the outside to the inside of said pre-chamber. The pre-chamber engine according to any one of claims 1 to 3, wherein the opening is located at a position offset from the center of the receiving surface. the recess extends in a first direction along the axial direction of the pre-chamber;
In the first direction, a distance from one end of the recess to the communication path and a distance of the other end from the other end of the recess to the communication path are set to different sizes,
The pre-chamber according to any one of claims 1 to 4, wherein in the first direction, the one end side portion and the other end side portion are formed into curved surfaces with different curvatures. formula engine. the recess extends in a first direction along the axial direction of the pre-chamber and in a second direction perpendicular to the first direction;
When the fuel injected from the fuel injection valve reaches the recess, the spread width of the fuel in the second direction is set smaller than the outer width of the pre-chamber in the second direction. The pre-chamber engine according to any one of claims 1 to 5, characterized in that:

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