WO2021161553A1

WO2021161553A1 - Sub-chamber spark ignition engine

Info

Publication number: WO2021161553A1
Application number: PCT/JP2020/025900
Authority: WO
Inventors: 山田　敏之; 欣也井上; 貴之城田; 一成野中; 晃弘津田
Original assignee: 三菱自動車工業株式会社
Priority date: 2020-02-10
Filing date: 2020-07-01
Publication date: 2021-08-19
Also published as: JP7226639B2; JPWO2021161553A1

Abstract

This sub-chamber spark ignition engine comprises a main chamber (21), a sub-chamber (22) sectioned by the main chamber (21) and a dividing wall (23), a plurality of communication paths (24) provided to the dividing wall (23), a fuel injection valve furnished in a wall section of the main chamber (21), and a spark plug (18) that ignites an air-fuel mixture in the sub-chamber (22), the flames formed in the sub-chamber (22) by the ignition of the air-fuel mixture in the sub-chamber (22) being emitted into the main chamber (21) via the communication paths (24) to ignite the air-fuel mixture in the main chamber (21), wherein the communication paths (24) include swirl-flow-generating communication paths (24c) that are formed at an angle inclined relative to the center direction of the sub-chamber (22) and that generate a swirl flow in the sub-chamber (22) through compressed air from the main chamber (21), and a fuel inflow communication path (24a) that is formed at a different angle than the swirl-flow-generating communication paths (24c) in relation to the center direction of the sub-chamber (22) and that supplies fuel into the sub-chamber (22) from the main chamber (21) side.

Description

Sub-chamber spark ignition engine

The present invention relates to a sub-chamber type spark ignition engine provided with a system for igniting the air-fuel mixture in the main chamber by ejecting a flame formed by igniting the air-fuel mixture in the sub-chamber into the main chamber.

In the spark ignition engine, a sub-combustion chamber (also called a sub-chamber) separated from the main combustion chamber (also called a main chamber) by a partition is provided, and a communication passage connecting these main chamber and the sub-chamber to each other is formed in the partition. Then, the air-fuel mixture in the sub-chamber is ignited, and the flame formed in the sub-chamber at this time is ejected into the main room through the communication passage to ignite the air-fuel mixture in the main room (also called a jet ignition system). A sub-chamber spark ignition engine is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-204835

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

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

In the case of such a passive method, it is possible to easily supply fuel to the sub-chamber by injecting fuel at the timing of the compression stroke. However, since the time interval between the fuel supply into the sub chamber 122 and the ignition timing is short, as schematically shown in FIG. 7, the equivalent ratio in the sub chamber 122 becomes light and shade, and the ignition becomes unstable. There is a problem.

This case was created by paying attention to such issues, and enables stable ignition in the sub-chamber in a sub-chamber spark ignition engine equipped with a passive jet ignition system. That is one of the purposes. Not limited to this purpose, it is also an action and effect derived by each configuration shown in the embodiment for carrying out the invention described later, and it is also for another purpose of this case to exert an action and effect that cannot be obtained by the conventional technique. be.

The sub-chamber spark ignition engine of the present invention includes a main chamber, a sub-chamber partitioned by the main chamber and a partition wall, a plurality of passages provided in the partition wall and communicating the main chamber and the sub-chamber, and the above-mentioned A spark plug provided in the central axis of the sub-chamber or in the vicinity of the central axis to ignite the air-fuel mixture in the sub-chamber is provided, and a flame formed in the sub-chamber by ignition of the air-fuel mixture in the sub-chamber is provided. , A sub-chamber type spark ignition engine that is ejected into the main chamber through the continuous passage to ignite the air-fuel mixture in the main chamber, and the continuous passage is directed toward the central axis of the sub-chamber. A swirl flow generation passage that is formed at an inclined angle with respect to the main chamber and generates a swirl flow in the sub chamber by compressed air from the main chamber, and the swirl flow generation in a direction toward the central axis of the sub chamber. It is characterized in that it is formed at an angle different from that of the communication passage, and includes a fuel inflow communication passage for supplying fuel from the main chamber side to the sub chamber.

The swirl flow generation passage and the fuel inflow passage are formed on one end side of the sub chamber, and the spark plug is formed on the other end side of the sub chamber, and the swirl flow generation passage and the fuel inflow passage are formed. The passage is formed so as to be inclined from one end side toward the other end side as it goes from the main chamber to the sub chamber, and an extension line of the fuel inflow communication passage is a surface of the partition wall on the sub chamber side. The position to reach the wall surface of the sub-chamber is preferably the other end side of the position where the extension line of the swirl flow generation communication passage reaches the wall surface of the sub-chamber.
It is preferable that the other end side of the sub-chamber wall surface is a cylindrical inner wall surface formed in a cylindrical shape, and the extension line of the fuel inflow communication passage reaches the cylindrical inner wall surface.
It is preferable that the one end side of the sub-chamber wall surface is formed with a reduced diameter inner wall surface whose cross-sectional area gradually decreases from the other end side toward the one end side.
It is preferable that the one end side recess is formed on the surface of the partition wall on the main chamber side, and the fuel inflow communication passage is formed in the recess.
It is preferable that the main chamber is provided with a fuel injection valve for injecting fuel, and the recess is provided with a receiving surface on which the direct injection fuel from the fuel injection valve collides.

According to this case, the fuel injected into the main chamber can concentrate the rich mixture of fuel around the spark plug in the sub chamber by the swirl flow generated in the sub chamber. As a result, stable ignition can be realized, and the amount of fuel supplied to the sub-chamber can be suppressed.

1A and 1B are views showing the configuration of a combustion chamber of one cylinder of the subchamber type spark ignition engine according to the embodiment, FIG. 1A is a vertical sectional view thereof, and FIG. 1B is a top view thereof. 2A and 2B are views for explaining the characteristics of the communication passage formed in the partition wall of the sub-chamber type spark ignition engine shown in FIGS. 1A and 1B, and FIG. 2A is a main part of the sub-chamber showing the orientation of the communication passage. 2B is a schematic cross-sectional view of the above, and FIG. 2B is a vertical cross-sectional view of the sub chamber. 3A and 3B are perspective views showing the shape of a modified example of the concave portion of the sub chamber of the subchamber type spark ignition engine shown in FIGS. 1A and 1B. FIG. 3A shows the first modified example, and FIG. 3B shows the first modified example. A second modification is shown. 4A and 4B are schematic perspective views for explaining the state of gas flow in the sub-chamber of the sub-chamber type spark ignition engine shown in FIGS. 1A and 1B, and FIG. 4A shows the protrusion of the recess into the sub-chamber. A case where no consideration is given is shown, and FIG. 4B shows a case where the protrusion of the recess into the sub-chamber is taken into consideration. 5A to 5C are vertical cross-sectional views of the combustion chamber showing the fuel injection modes of the sub-chamber spark ignition engine shown in FIGS. 1A and 1B in the order of strokes in FIGS. 5A to 5C. FIG. 6 is a diagram showing a modified example of the sub chamber of the sub chamber type spark ignition engine shown in FIGS. 1A and 1B. FIG. 7 is a vertical cross-sectional view of the combustion chamber for explaining the problem of this case.

Hereinafter, the sub-chamber type spark ignition engine as an embodiment will be described with reference to the drawings. The embodiments shown below are merely examples, and there is no intention of excluding the application of various modifications and techniques not specified in the following embodiments. Each configuration of the present embodiment can be variously modified and implemented without departing from the gist thereof. In addition, it can be selected as needed, or can be combined as appropriate.

[overall structure]
The sub-chamber type spark ignition engine (which is a spark ignition type internal combustion engine and includes a gasoline 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. As shown in 1A, the cylinder 11 formed in the cylinder block 2, the piston 12 reciprocating in the cylinder 11, the intake port 13 and the exhaust port 14 formed in the cylinder head 3, and the intake port 13 are equipped. The intake valve 15 and the exhaust valve 16 provided in the exhaust port 14 are provided.
In the present embodiment, as shown in FIG. 1B, two intake ports 13 (15 intake valves) and two exhaust ports 14 (exhaust valves 16) are provided, but the number of intake ports (number of intake valves). ) And the number of exhaust ports (the number of exhaust valves) are not limited to this.

On the cylinder head 2 side (upper middle of FIG. 1A) in the cylinder 11, the combustion chamber 20 is partitioned by the inner wall of the cylinder 11, the top surface 12a of the piston 12, and the cylinder head 2. An intake port 13 opened and closed by an intake valve 15 and an exhaust port 14 opened and closed by an exhaust valve 16 are connected to the combustion chamber 20 so as to communicate with each other. Here, the top of the combustion chamber 20 is formed in a pent roof shape having an intake slope provided with the intake valve 15 and an exhaust slope provided with the exhaust valve 16.

A fuel injection valve 17 is provided on the peripheral wall 11a at the top of the cylinder 11 (upper part in FIG. 1A). It is configured as a direct injection engine). In the present embodiment, only the fuel injection valve 17 that injects fuel directly 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 type engine, and is a spark-ignition engine in the combustion chamber 20 at the top of the combustion chamber 20 (here, the top of the pent roof shape) 20a, in the vicinity of the bore central axis or the bore central axis. The ignition plug 18 is equipped with the 18a exposed.

[Composition of main room and sub room]
The top 20a of the combustion chamber 20 is provided with a partition wall 23 that divides 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 so as to cover the space where the spark discharge portion 18a of the spark plug 18 is exposed, and the internal space (the space including the spark discharge portion 18a) covered by the partition 23 in the combustion chamber 20 is the sub chamber 22. The external space of the partition wall 23 in the combustion chamber 20 is the main chamber 21. The sub chamber 22 is formed in a rotating body shape except for a part.

As shown in FIGS. 2A and 2B, the partition wall 23 is formed with a plurality of (six in this embodiment) communication passages (also referred to as “nozzles”) 24 that communicate the main chamber 21 and the sub chamber 22. There is. A plurality of (six in this embodiment) communication passages 24 are used to allow the inflow of the air-fuel mixture from the main chamber 21 side to the sub-chamber 22 and the outflow of flame from the sub-chamber 22 side to the main chamber 21 side. It is provided.
A part (here, one) of the plurality of communication passages 24 functions as a fuel inflow communication passage 24a for introducing the fuel injected into the main chamber 21 from the fuel injection valve 17 into the sub chamber 22, and the other passages 24. The communication passage 24 functions as an air inflow communication passage for introducing the air in the main chamber 21 (strictly speaking, an air-fuel mixture leaning fuel) into the sub chamber 22.
The fuel injection valve 17 includes an injection port for supplying fuel into the sub chamber 22.

In the sub-chamber 22, the fuel (air-fuel mixture containing a large amount of fuel) introduced through the fuel inflow passage 24a is ignited by the ignition plug 18 at a predetermined timing in the compression stroke, and the sub-chamber 22 is ignited by this ignition. The flame formed inside is jetted into the main chamber 21 through a plurality of communication passages 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 dilute mixture and promoting combustion, and can be applied to lean burn in the main chamber 21 or a large amount of EGR, thereby improving fuel efficiency. Become.

Further, in the present embodiment, the direct injection fuel from the fuel injection valve 17 collides with the outer surface of the sub chamber 22 (that is, the outer surface of the partition wall 23) around the opening 24b where the fuel inflow communication passage 24a opens. A recess 30 having a receiving surface 30a is formed. The recess 30 of the present embodiment is formed in the shape of a mortar formed by a smooth curved surface. The opening 24b is arranged at or near the bottom of the mortar-shaped recess 30.

However, the shape of the recess 30 is not limited to this, and it is sufficient that the diameter of the recess 30 is gradually reduced from the outside to the inside of the sub chamber 22, for example, a funnel (funnel) using a conical surface such as a conical surface. ) May be in shape. That is, it may be formed by using a conical surface like the concave portion 30A shown as a modified example in FIG. 3A, or may be formed by using a pyramidal surface like the concave portion 30B shown as a modified example in FIG. 3B. In the example shown in FIG. 3B, a quadrangular pyramid surface is used, but other pyramid surfaces can also be applied.

Further, even when a conical surface is used for the wall surface shape of the concave portion 30, the wide side B (corresponding to the opening of the concave portion 30) and the narrow side T (corresponding to the bottom surface portion of the concave portion 30) of the conical surface are circular. And regular polygons, but may be ellipses and other polygons.
Further, as shown in the

recesses

30A and 30B shown in FIGS. 3A and 3B, the lines (L1 and L2 in FIG. 3) connecting the center of the wide side B of the conical surface and the center of the narrow side T of the conical surface are the lines of the frustum. An inner surface shape of a frustum inclined with respect to the bottom surface B or the top surface T (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, the

recesses

30A and 30B are shown obliquely downward in correspondence with FIGS. 1A and 1B.

In the modified examples shown in FIGS. 3A and 3B, the opening 24b of the fuel inflow passage 24a is arranged at the deepest part (bottom) of the

recesses

30A and 30B, but the arrangement of the opening 24b is limited to this. No. Further, the number of openings 24b (the number of fuel inflow communication passages 24a) is not limited to one. A plurality (here, two) openings 24b may be provided as in the recess 30B shown in FIG. 3B. In this case, the direction in which the openings 24b are lined up may be either the first direction D1 or the second direction D2.

In the present embodiment, the upper part of the partition wall 23 [the upper part in FIG. 2B (that is, the spark plug 18 side)] is formed in a cylindrical shape, and the lower part of the partition wall 23 [the lower part in FIG. 2B (that is, the piston 12 side) goes downward. It is formed in a shape whose diameter is reduced accordingly (here, a substantially hemispherical shape). Further, the partition wall 23 is formed in a rotating body shape centered on the position of the spark discharge portion 18a of the spark plug 18 (that is, the position near the sub chamber central axis CL or the sub chamber central axis CL), except for a part. Has been done. However, the shape of the partition wall 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 have a shape that is continuous with the cylindrical shape of the upper portion and whose diameter decreases as it goes downward and the cross-sectional area gradually decreases. ..
In addition, each of the communication passages 24 is arranged in a portion (diameter-reduced portion) having a shape in which the cross-sectional area gradually decreases in the lower part of the sub chamber 22. Further, the direction of the auxiliary chamber central axis CL and the direction of the bore central axis do not necessarily have to be the same, and the auxiliary chamber central axis CL may be provided so as to be inclined with respect to the bore central axis.

Therefore, as shown in FIGS. 4A and 4B, the inner wall surface of the sub chamber 22 (the sub chamber wall surface 22W) has a cylindrical inner wall surface 22W1 and a lower portion (that is, the ignition plug 18 side) formed in a cylindrical shape at the upper portion (that is, the ignition plug 18 side). That is, it is provided with a diameter-reduced inner wall surface 22W2 formed in a shape in which the diameter is reduced toward the bottom on the piston 12 side). Each of the communication passages 24 is formed on the reduced diameter inner wall surface 22W2 at the lower part of the sub chamber 22. Further, the recess 30 is also formed in the reduced diameter inner wall surface 22W2 at the lower part of the sub chamber 22, and as shown in FIG. 4B, the portion where the recess 30 is formed in the inner wall surface of the sub chamber 22 is formed in the sub chamber 22. It is a convex inner wall portion 22W3 formed in a convex shape toward the surface.

By the way, in the compression stroke, fuel is mainly introduced into the sub-chamber 22 through the fuel inflow communication passage 24a, and air is mainly introduced into the sub-chamber 22 through the other communication passage 24.
As shown in FIG. 2A, the fuel inflow passage 24a is in the direction toward the central axis CL of the sub chamber 22 and upward (that is, on the spark plug 18 side) when viewed from the axial direction (direction in which the central axis of the bore extends). ) Is oriented toward. As a result, the fuel introduced from the outside to the inside of the sub chamber 22 tends to approach the spark discharge portion 18a of the spark plug 18.

On the other hand, among the communication passages 24 that function as the air inflow communication passages, all of the communication passages 24c except for one located at the center of the sub chamber 22 (here, coincident with the bore central axis) are shown in the figure. As shown in 2B, when viewed from the axial direction (the direction in which the central axis of the bore extends), the direction is inclined with respect to the direction (central direction) toward the central axis CL of the sub chamber 22 and upward (that is, the spark plug). It is oriented toward (18 side).
In the present embodiment, each of the communication passages 24c is oriented in a direction in which the passages 24c are inclined to the left at the same angle in a plan view with respect to the direction toward the center of the sub chamber 22. As a result, the air introduced from the outside to the inside of the sub chamber 22 through the plurality of communication passages 24c generates a swirl flow in the sub chamber 22 as shown by arrows in FIGS. 2A and 2B. Therefore, these communication passages 24c function as swirl flow generation communication passages. The inclination direction of the plurality of swirl flow generation passages 24c may be to the right with respect to the direction of the central axis of the sub chamber 22, and the inclination angles of the swirl flow generation passages 24c do not necessarily have to be the same. good.

Further, as shown by the arrow of the alternate long and short dash line in FIG. 2B, in the side view (viewed from the direction perpendicular to the central axis of the sub chamber 22), the fuel inflow communication passage 24a and the swirl flow generation communication passage 24c are any of them. Is also oriented in an inclined direction from one end side [lower piston 12 side in FIG. 2B] to the other end side [upper spark plug 18 side in FIG. 2B] of the sub chamber 22.
The position P1 at which the extension line of the fuel inflow passage 24a into the sub chamber 22 reaches the sub chamber wall surface 22W, which is the surface of the partition wall 23 on the sub chamber 22 side (inner surface of the partition wall 23), is the swirl flow generation continuous passage 24b. Is located in the cylindrical inner wall surface 22W1 on the other end side [the upper ignition plug 18 side in FIG. 2 (b)] from the position P2 where the extension line into the sub chamber 22 reaches the sub chamber wall surface 22W. ing.
Further, the extension line of the fuel inflow passage 24a to the sub chamber wall surface 22W is arranged so as to reach the cylindrical inner wall surface (cylindrical inner wall surface) 22W1 in the upper part of the sub chamber 22.

The recess 30 is formed on a slope portion deviated from the auxiliary chamber central axis CL in a substantially hemispherical portion (a shape in which the diameter is reduced toward the lower side and the cross-sectional area is gradually reduced) in the lower part of the partition wall 23. 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 the present embodiment, a recess 30 is formed in a part of the lower portion of the partition wall 23 while maintaining a substantially uniform thickness, and the recess 30 is formed on the outer surface of the partition wall 23 and on the inner surface of the partition wall 23. A convex portion 31 corresponding to the concave portion 30 is formed. However, the recess 30 may have a shape in which the outer surface of the sub chamber 22 (outer surface of the partition wall 23) is cut out. For example, the recess 30 is formed in the outer surface of the partition wall 23 while maintaining a substantially hemispherical shape on the inner surface of the partition wall 23. May be formed. In this case, the thickness of the portion where the recess 30 is formed decreases.

The receiving surface 30a is formed at the center of the fuel injection range from the fuel injection valve 17, and the opening 24b is arranged at a position deviated from the center of the fuel injection range from the fuel injection valve 17. When the center of the fuel injection range is the face center (center of the front view) of the recess 30 in the front view, the opening 24b is arranged at a position deviated from the center of the front view. In the present embodiment, the center of the fuel injection range is slightly shifted downward in FIG. 2B (that is, the piston 12 side), and the opening 24b is upward (that is, the cylinder head) in FIG. 2B. There is a slight shift to the 3rd side). The direction in which the opening 24b deviates from the center of the fuel injection range is not limited to this.

Further, the fuel inflow passage 24a is closer to the axis in the sub chamber 22 (near the sub chamber central axis CL or the sub chamber central axis CL) from the opening 24b toward the inside of the sub chamber 22, and is upward in FIG. 2B. It is inclined toward (that is, the cylinder head 3 side). The fuel inflow direction in the fuel inflow passage 24a is a direction approaching the spark discharge portion 18a of the upper spark plug 18 in the sub chamber 22.

[Fuel injection and combustion]
In the present embodiment, fuel is injected from the fuel injection valve 17 into the main chamber 21 at the beginning of the intake stroke [see FIG. 5A], and at the end of the subsequent compression stroke, the fuel injection valve 17 enters the sub chamber 22 via the main chamber 21. Fuel is injected into (see FIG. 5B). When port injection is adopted, port injection is performed in the exhaust stroke, and fuel is supplied into the main chamber 21 together with the intake air in the intake stroke. Then, at the end of the compression stroke, the air-fuel mixture formed in the sub chamber 22 by the spark plug 18 is ignited, and the flame formed in the sub chamber 22 by this ignition is transmitted to the main chamber through the plurality of communication passages 24. A jet is ejected into the main chamber 21 to ignite the air-fuel mixture in the main chamber 21 and burn it [see FIG. 5C].

[Action and effect]
According to the sub-chamber type spark ignition engine according to the present embodiment, the pressurized air (fuel-lean air-fuel mixture) in the main chamber 21 enters the sub-chamber 22 through the communication passage 24 in the compression stroke. .. Then, the air entering the sub-chamber 22 through the swirl flow generation communication passage 24c generates a swirl flow in the sub-chamber 22 as shown in FIGS. 2A and 2B. As shown in FIGS. 4A and 4B, this swirl flow rises toward the spark plug 18 while developing in the sub-chamber 22.

On the other hand, at the end of the compression stroke, fuel is injected from the fuel injection valve 17 into the sub chamber 22 via the main chamber 21, and is introduced into the sub chamber 22 from the opening 24b via the fuel inflow communication passage 24a.
The swirl flow generated in the sub-chamber 22 collects fuel in the vicinity of the spark discharge portion 18a of the spark plug 18 near the center of the swirl because the swirling flow velocity is slow, and the air of the fuel because the swirling flow velocity is fast near the outside of the swirl. Mixing with is promoted.

Therefore, even if the time interval between the fuel supply into the chamber 22 and the ignition timing is short, the air-fuel mixture having a high fuel concentration near the spark discharge portion 18a of the spark plug 18 will be ignited, and the ignition will be performed reliably. be able to. By this ignition, a flame can be surely formed in the sub chamber 22, and the flame is jetted into the main chamber 21 through the plurality of passages 24 to ignite and burn the air-fuel mixture in the main chamber 21. be able to.
Further, since the air-fuel mixture having a high fuel concentration is generated only in the vicinity of the spark discharge portion 18a, it is possible to reduce the amount of direct injection fuel.

A convex inner wall surface 22W3 corresponding to the recess 30 is formed on the inner surface of the partition wall 23 (inner wall surface of the sub chamber 22), and the air entering the sub chamber 22 through the swirl flow generation communication passage 24c is convex. By colliding with the shaped inner wall portion 22W3, a turbulent flow is generated to promote mixing of the fuel with air, and then, while rising, along the cylindrical inner wall surface (cylindrical inner wall surface) in the upper part of the sub chamber 22. It is rectified and develops into a high-speed swirl flow.
Therefore, the convex inner wall portion 22W3 corresponding to the concave portion 30 contributes to the uniformization of the equivalent ratio in the sub chamber 22.

Further, the fuel (fuel-rich air-fuel mixture) introduced into the sub chamber 22 through the fuel inflow passage 24a is a cylinder close to the spark discharge portion 18a of the spark plug 18 from the reduced diameter inner wall surface 22W2 in the sub chamber 22. By moving toward the position P1 on the inner wall surface 22W1, it becomes easier to generate a rich air-fuel mixture in the vicinity of the spark discharge portion 18a.
However, as shown in FIG. 4A, when a swirl flow is generated on the reduced diameter inner wall surface 22W2, the swirl flow may hinder the progress of the fuel. In this respect, in the present embodiment, as described above, the convex inner wall portion 22W3 is formed on the reduced diameter inner wall surface 22W2, so that the air entering the sub chamber 22 is convex as shown in FIG. 4B. Since turbulence is generated by colliding with the inner wall portion 22W3, it is difficult to generate a swirl flow on the reduced diameter inner wall surface 22W2. Therefore, the progress of the fuel is less likely to be hindered, and a rich air-fuel mixture is likely to be generated in the vicinity of the spark discharge portion 18a.

However, even if a swirl flow is generated on the reduced diameter inner wall surface 22W2, the swirl flow is not strong at this stage. Therefore, if the fuel velocity toward the position P1 is high, even if the convex inner wall portion 22W3 is not formed, the swirl flow is not formed. It is also conceivable that a rich air-fuel mixture can be generated in the vicinity of the spark discharge unit 18a without any trouble.

Further, in the present embodiment, the fuel injected from the fuel injection valve 17 first collides with the receiving surface 30a of the recess 30. Therefore, the direct-injection fuel is promoted to split and vaporize while staying in the recess 30 and its vicinity, and is introduced into the sub-chamber 22 from the opening 24b via the fuel inflow communication passage 24a. The splitting and vaporization in the recess 30 contributes to the subsequent promotion of mixing with air in the sub chamber 22.

In this way, the direct-injection fuel is caught in the recess 30 and proceeds from the opening 24b to the fuel inflow passage 24a, so that a part of the fuel injected from the injector 17 does not enter the sub-chamber 22 and the partition wall. Passing along the outer surface of 23 (the wall portion of the sub chamber 22) is suppressed, and reaching the opposite side of the injector 17 to form a rich air-fuel mixture is avoided or suppressed. Therefore, it is possible to avoid or suppress the generation of a large amount of NOx due to the rich air-fuel mixture.

Further, since the opening 24b of the fuel inflow passage 24a is arranged at the bottom of the recess 30 or near the bottom, the fuel that collides with the receiving surface 30a and is promoted to split or vaporize is along the wall surface of the recess 30. The fuel smoothly flows into the sub chamber 22 from the opening 24b through the fuel inflow passage 24a.

Since the fuel inflow communication passage 24a is inclined in a direction approaching the spark discharge portion 18a of the spark plug 18, the fuel passing through the fuel inflow communication passage 24a goes toward the spark discharge portion 18a in the upper part of the sub chamber 22 and is directed to the spark discharge portion 18a. A rich fuel mixture is concentrated in the vicinity of 18a. Therefore, the ignition by the spark plug 18 and the flame formed in the sub chamber 22 after that can be strengthened, and a strong jet is ejected into the main chamber 21 through the plurality of communication passages 24 to mix in the main chamber 21. It can ignite the qi and promote combustion.

[others]
The configuration of the sub-chamber spark ignition engine described above is an example. For example, the arrangement of the sub chamber 22, that is, the partition wall 23 for partitioning the sub chamber 22, is not necessarily limited to the bore central axis of the top 20a of the combustion chamber 20 or the vicinity of the bore central axis, and also the top 20a of the combustion chamber 20. Not limited.
Further, in the above embodiment, only one fuel inflow communication passage 24a is provided, but a plurality of fuel inflow communication passages 24a may be provided in the recess 30.
Further, the fuel injection valve 17 may be provided with an injection port for supplying fuel into the main chamber 21 in addition to the injection port for supplying fuel into the sub chamber 22.

Further, in the above embodiment, the recess 30 is formed, but this is not essential, and the shape of the sub chamber 22, that is, the partition wall 23 for partitioning the sub chamber 22, is shown in the fuel inflow chain as shown in FIG. It may have a perfect rotating body shape except for the passage 24a.
Further, when the recess 30 is also provided, the recess 30 has a funnel shape using a mortar-shaped or conical surface formed by a smooth curved surface, but the shape of the recess 30 is not limited to this.
Further, in the above embodiment, the opening 24b is arranged at the bottom of the recess 30 or near the bottom, but if the inner surface shape of the recess 30 is a shape that can guide the fuel received by the receiving portion 30a to the opening 24b. , The opening 24b may be arranged at the bottom of the recess 30 or near the bottom.

1 Sub-chamber spark ignition 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 part 20 Combustion chamber 20a Top of combustion chamber 20 CL Sub-chamber Central shaft 21 Main room (Main combustion chamber)
22 Sub-chamber (sub-combustion chamber)
22W Sub-indoor wall surface 22W1 Cylindrical inner wall surface 22W2 Reduced diameter inner wall surface 22W3 Convex inner wall part 23 Partition wall 24 consecutive passages (nozzles)
24a Fuel inflow passage (nozzle)
24b Opening of fuel inflow passage 24a 24c Swirl flow formation passage (nozzle)
30, 30A, 30B Recessed surface 30a Receiving surface 31 Convex part

Claims

A main room, a sub-chamber partitioned by the main room and a partition wall, a plurality of communication passages provided in the partition wall and communicating the main room and the sub-chamber, and a central axis of the sub-chamber or the central axis of the sub-chamber. An ignition plug provided in the vicinity for igniting the air-fuel mixture in the sub-chamber is provided, and a flame formed in the sub-chamber by ignition of the air-fuel mixture in the sub-chamber is transmitted to the main chamber via the communication passage. It is a sub-chamber type spark ignition engine that ignites the air-fuel mixture in the main chamber.
The passageway
A swirl flow generation communication passage formed at an angle inclined with respect to the central axis of the sub chamber and generating a swirl flow in the sub chamber by compressed air from the main chamber.
A fuel inflow passage that is formed at an angle different from that of the swirl flow generation passage with respect to the direction toward the central axis of the sub chamber and supplies fuel from the main chamber side to the sub chamber is included. A sub-chamber spark ignition engine that features this.
The swirl flow generation passage and the fuel inflow passage are formed on one end side of the sub chamber, and the spark plug is formed on the other end side of the sub chamber.
The swirl flow generation communication passage and the fuel inflow communication passage are formed so as to be inclined from one end side toward the other end side as the main chamber toward the sub chamber, and the fuel inflow communication passage is extended. The position where the line reaches the sub-chamber wall surface, which is the surface of the partition wall on the sub-chamber side, is on the other end side of the position where the extension line of the swirl flow generation continuous passage reaches the sub-chamber wall surface. The sub-chamber spark ignition engine according to claim 1.
The other end side of the sub-chamber wall surface is a cylindrical inner wall surface formed in a cylindrical shape.
The sub-chamber spark ignition engine according to claim 2, wherein the extension line of the fuel inflow passage reaches the cylindrical inner wall surface.
A reduced-diameter inner wall surface is formed on one end side of the sub-chamber wall surface with respect to the cylindrical inner wall surface so that the cross-sectional area gradually decreases from the other end side toward the one end side. The sub-chamber spark ignition engine according to claim 3.
The aspect according to any one of claims 2 to 4, wherein a recess is formed on one end side of the surface of the partition wall on the main chamber side, and the fuel inflow passage is formed in the recess. Sub-chamber spark ignition engine.
A fuel injection valve for injecting fuel into the main chamber is provided.
The sub-chamber spark ignition engine according to claim 5, wherein the recess is provided with a receiving surface on which direct-injection fuel from the fuel injection valve collides.