JP7632367B2 - engine - Google Patents

Description

This disclosure relates to engines.

Patent Document 1 discloses an engine equipped with a main chamber, an auxiliary chamber separated from the main chamber by a partition, multiple communication passages provided in the partition that connect the main chamber to the auxiliary chamber, and a spark plug provided on or near the central axis of the auxiliary chamber to ignite the mixture in the auxiliary chamber. The multiple communication passages are provided for the inflow of the mixture from the main chamber side to the auxiliary chamber and for the outflow of flame from the auxiliary chamber side to the main chamber side. The multiple communication passages include a swirl flow generating communication passage formed at an angle inclined to the direction toward the central axis of the auxiliary chamber and generating a swirl flow in the auxiliary chamber by compressed air from the main chamber, and a fuel inflow communication passage formed at an angle different from the swirl flow generating communication passage with respect to the direction toward the central axis of the auxiliary chamber and supplying fuel from the main chamber side to the auxiliary chamber.

International Publication No. 2021/161553

In the engine disclosed in Patent Document 1, one fuel inflow passage is oriented in a direction toward the central axis of the auxiliary chamber when viewed from the axial direction, and the multiple swirl flow generating passages are oriented so as to be inclined at the same angle with respect to the central axis of the auxiliary chamber when viewed from the axial direction. For this reason, if the fuel inflow passages and the swirl flow generating passages are arranged at equal intervals around the partition without distinguishing between them, the flame flow injected from one of the swirl flow generating passages adjacent to the fuel inflow passage will move away from the flame flow injected from the fuel inflow passage, while the flame flow injected from the other swirl flow generating passage adjacent to the fuel inflow passage will approach the flame flow injected from the fuel inflow passage, making it impossible to inject the flame flow evenly in the circumferential direction of the main chamber. In addition, if there are a large number of swirl flow generating passages, the fuel inflow passages and the swirl flow generating passages will interfere with each other, making it impossible to arrange the fuel inflow passages and the swirl flow generating passages around the partition so that the flame flow is injected evenly in the circumferential direction of the main chamber.

In view of the above, at least one embodiment of the present invention aims to provide an engine that can inject flame flows from at least one fuel inlet passage and at least two or more swirl flow generating passages evenly in the circumferential direction of the main chamber.

(1) An engine according to at least one embodiment of the present invention includes a piston, a cylinder block in which a cylinder in which the piston reciprocates is provided, a cylinder head fixed to the cylinder block and forming a main chamber between the piston and the cylinder block, a partition wall provided on the main chamber side of the cylinder head and forming a sub-chamber within the main chamber, an injection nozzle for injecting fuel into the main chamber, and an ignition plug installed in the sub-chamber, the partition wall includes at least one fuel inflow communication passage that is provided straight toward the center of the sub-chamber in the circumferential direction of the cylinder and leads from the main chamber to the sub-chamber, and at least two or more swirl flow generating communication passages that are provided inclined with respect to the direction toward the center of the sub-chamber in the circumferential direction of the cylinder and lead from the main chamber to the sub-chamber, and among the two or more swirl flow generating communication passages, the swirl flow generating communication passage that is downstream in the circumferential flow of gas generated in the sub-chamber starting from the fuel inflow communication passage has a smaller angle of inclination with respect to the direction toward the center of the sub-chamber.

According to the above configuration (1), the swirl flow generating passage on the downstream side in the circumferential flow of gas generated in the auxiliary chamber starting from the fuel inflow passage is inclined at a smaller angle toward the center of the auxiliary chamber than the swirl flow generating passage on the upstream side, so the downstream swirl flow generating passage can be positioned closer to the fuel inflow passage. This allows the flame flows injected from at least one fuel inflow passage and at least two or more swirl flow generating passages to be injected evenly in the circumferential direction of the main chamber.

(2) In some embodiments, in the configuration of (1) above, the minimum flow passage cross-sectional area of the upstream swirl flow generating passage is larger than that of the downstream swirl flow generating passage.

According to the above configuration (2), the minimum flow path cross-sectional area of the upstream swirl flow generating passage is larger than that of the downstream swirl flow generating passage in the circumferential flow of gas generated in the auxiliary chamber starting from the fuel inflow passage, so the effective diameter of the upstream swirl flow generating passage can be made closer to that of the downstream swirl flow generating passage. This makes it possible to make the momentum of the flame flow injected from the upstream swirl flow generating passage closer to that of the downstream swirl flow generating passage.

(3) In some embodiments, in the configuration described above in (1) or (2), the opening of the upstream swirl flow generating passage on the auxiliary chamber side is larger than that of the downstream swirl flow generating passage.

According to the above configuration (3), the opening of the upstream swirl flow generating passage on the auxiliary chamber side is larger than that of the downstream swirl flow generating passage in the circumferential flow of gas flowing into the auxiliary chamber starting from the fuel inflow passage, so that the effective diameter of the upstream swirl flow generating passage can be made closer to that of the downstream swirl flow generating passage, thereby making it possible to make the momentum of the flame flow injected from the upstream swirl flow generating passage closer to that of the downstream swirl flow generating passage.

(4) In some embodiments, in any one of the configurations (1) to (3) above, the flow path cross-sectional area of each of the at least two or more swirl flow generating passages expands from the opening on the main chamber side toward the opening on the auxiliary chamber side, and the expansion ratio of the flow path cross-sectional area of the swirl flow generating passage on the upstream side is greater than that of the swirl flow generating passage on the downstream side.

According to the above configuration (4), the expansion ratio of the flow passage cross-sectional area of the upstream swirl flow generating passage is greater than that of the downstream swirl flow generating passage in the circumferential flow of gas flowing into the auxiliary chamber starting from the fuel inflow passage, so the effective diameter of the upstream swirl flow generating passage can be made closer to that of the downstream swirl flow generating passage. This makes it possible to make the momentum of the flame flow injected from the upstream swirl flow generating passage closer to that of the downstream swirl flow generating passage.

(5) In some embodiments, in any one of the configurations (1) to (4) above, the partition wall is provided with an auxiliary chamber tip portion to which the at least two swirl flow generating communication passages communicate, an auxiliary chamber base portion provided on the cylinder head side of the auxiliary chamber tip portion, and a step surface provided between the auxiliary chamber tip portion and the auxiliary chamber base, and the maximum cross-sectional area of the auxiliary chamber tip portion is smaller than the minimum cross-sectional area of the auxiliary chamber base.

According to the above configuration (5), by making the maximum cross-sectional area of the pre-chamber tip smaller than the minimum cross-sectional area of the pre-chamber base, a strong swirl flow can be generated at the pre-chamber tip. In addition, the flame flow ignited at the pre-chamber base separates at the step surface, allowing the flame flow to be ejected simultaneously from two or more swirl flow generating passages.

According to at least one embodiment of the present invention, the flame flow injected from at least one fuel inlet passage and at least two or more swirl flow generating passages can be injected evenly in the circumferential direction of the main chamber.

1 is a cross-sectional view showing a schematic overall configuration of an engine according to an embodiment; FIG. 2 is a side cross-sectional view conceptually showing the cylinder and the partition wall shown in FIG. 1 . FIG. 2 is a cross-sectional plan view conceptually showing a cylinder and a partition wall shown in FIG. 1 . FIG. 11 is a cross-sectional view of a partition wall according to a second embodiment. FIG. 11 is a cross-sectional view of a partition wall according to a third embodiment. FIG. 11 is a cross-sectional view of a partition wall according to a fourth embodiment. FIG. 13 is a cross-sectional view of a partition wall according to a fifth embodiment.

The following describes an embodiment of the present invention with reference to the attached drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described as the embodiment or shown in the drawings are not intended to limit the scope of the present invention and are merely illustrative examples.

[Embodiment 1]
[Overall engine configuration]
FIG. 1 is a cross-sectional view showing a schematic overall configuration of an engine 1 according to an embodiment. As shown in FIG. 1, the engine 1 according to an embodiment includes a piston 10, a cylinder block 12, a cylinder head 14, a partition wall 16, an injection nozzle 18, and an ignition plug 20. The cylinder block 12 includes a cylinder 22 in which the piston 10 reciprocates. The cylinder head 14 is fixed to the cylinder block 12, and forms a main chamber (combustion chamber) 24 between the cylinder head 14 and the piston 10. The cylinder head 14 includes an intake port 26 and an exhaust port 28. For example, two intake ports 26 and two exhaust ports 28 are provided for each main chamber 24, but this is not limited to this. The intake port 26 includes an intake valve 30 for opening and closing the intake port 26, and the exhaust port 28 includes an exhaust valve 32 for opening and closing the exhaust port 28. For example, the intake port 26 includes an injection nozzle 34 (hereinafter referred to as a "port injector 34") for injecting fuel, but the port injector 34 is not essential. The partition wall 16 is provided on the main chamber side of the cylinder head 14, and defines an auxiliary chamber (pre-combustion chamber) 36 within the main chamber. The injection nozzle 18 (hereinafter referred to as a "direct injector 18") injects fuel into the main chamber. The ignition plug 20 is provided in the auxiliary chamber and is capable of igniting the air-fuel mixture that flows into the auxiliary chamber.

[Overall operation of engine 1]
In the engine 1 according to the embodiment, the port injector 34 injects fuel during the intake stroke when the intake valve 30 opens the intake port 26 and the piston 10 descends. As a result, an air-fuel mixture is supplied from the intake port 26 to the main chamber 24. In the engine 1 according to the embodiment, the air-fuel mixture in the main chamber becomes a lean mixture that is leaner than the theoretical air-fuel ratio.

During the compression stroke when the intake valve 30 closes the intake port 26 and the piston 10 rises, the direct injector 18 injects fuel. As a result, the fuel injected from the direct injector 18 is supplied to the auxiliary chamber 36 together with the mixture in the main chamber. The mixture in the auxiliary chamber is then ignited by the spark plug 20. In the engine 1 according to the embodiment, the mixture in the auxiliary chamber has an air-fuel ratio equivalent to the theoretical air-fuel ratio.

During the expansion stroke, which causes the piston 10 to descend, the mixture in the auxiliary chamber is ignited by the spark plug 20 and becomes a flame stream that is injected into the main chamber, combusting the mixture in the main chamber.

During the exhaust stroke, when the exhaust valve 32 opens the exhaust port 28 and the piston 10 rises, the combustion gas in the main chamber is discharged. The engine 1 operates by repeating the intake stroke, compression stroke, expansion stroke, and exhaust stroke. In the engine 1 according to the embodiment, the port injector 34 injects fuel during the intake stroke, but it may also be configured to inject fuel during the exhaust stroke. In this case, fuel is supplied to the main chamber 24 during the intake stroke.

[Partition wall details]
FIG. 2 is a side cross-sectional view conceptually showing the cylinder 22 and the partition wall 16 shown in FIG. 1, and FIG. 3 is a plan cross-sectional view conceptually showing the cylinder 22 and the partition wall 16 shown in FIG. 1. As shown in FIG. 2, the partition wall 16 has an external shape in the form of a combination of a cylinder and a hemisphere. A flange 38 is provided at the end of the partition wall 16 on the cylinder side, and the partition wall 16 is fixed to the main chamber side of the cylinder head 14 by this flange 38. As a result, the cylinder side of the partition wall 16 becomes the base end side fixed to the cylinder head 14, and the hemisphere side becomes the tip end side located on the piston side. As shown in FIG. 2, the partition wall 16 has an auxiliary chamber 36 inside thereof, which has a shape in the form of a combination of a cylinder and a hemisphere. The cylinder side of the auxiliary chamber 36 constitutes an auxiliary chamber base part 40 located on the cylinder head side, and the hemisphere side constitutes an auxiliary chamber tip part 42 located on the piston side.

The partition 16 has a fuel inlet passage 44 and a swirl flow generating passage 46 at its tip end that connect from the main chamber 24 to the auxiliary chamber 36 (auxiliary chamber tip 42).

As shown in FIG. 3, at least one fuel inflow communication passage 44 is provided on the direct injector side in the circumferential direction of the cylinder 22. The fuel inflow communication passage 44 is preferably provided in the injection range RG of the direct injector 18 in the circumferential direction of the cylinder 22, more preferably in a position directly opposite the injection direction of the direct injector 18 in the circumferential direction of the cylinder 22. When the fuel inflow communication passage 44 is provided in a position directly opposite the injection direction of the direct injector 18 in the circumferential direction of the cylinder 22, the fuel inflow communication passage 44 is provided on an extension line of the injection direction of the direct injector 18 and extends straight toward the center of the auxiliary chamber 36. As shown in FIG. 2, the fuel inflow communication passage 44 is provided at an angle so as to approach the cylinder head 14 as it moves toward the inside (center) of the auxiliary chamber 36, so that the fuel FE injected from the direct injector 18 during the compression stroke of the engine 1 flows into the fuel inflow communication passage 44, and is more preferably provided along the injection direction of the direct injector 18. There is at least one fuel inflow passage 44, but this is not limited to one and may be two or more.

As shown in FIG. 3, there are at least two swirl flow generating passages 46, which are provided at positions different from the fuel inflow passages 44 in the circumferential direction of the cylinder 22. The swirl flow generating passages are provided at an angle to the direction toward the center of the auxiliary chamber 36 in the circumferential direction of the cylinder. As shown in FIG. 2, the swirl flow generating passages 46 are provided horizontally or at an angle to the horizontal direction. The swirl flow generating passages 46 are preferably provided at an angle to approach the cylinder head 14 as they move toward the inside of the auxiliary chamber 36, so that the mixture in the main chamber flows into the auxiliary chamber during the compression stroke of the engine 1. The number of swirl flow generating passages 46 is, for example, seven, but is not limited to seven as long as there are two or more.

As shown in Fig. 3, the auxiliary chamber side wall surface 16a of the partition 16 is circular in a cross section passing through the auxiliary chamber side openings (auxiliary chamber side openings) 46a of the two or more swirl flow generating communication passages 46. Note that in Fig. 3, the swirl flow generating communication passages 46 are shown diagrammatically and as being provided in a horizontal direction, but as described above, this is not limited to this and the passages may be provided at an angle so as to approach the cylinder head 14 as they move toward the inside of the auxiliary chamber 36.

Of the two or more swirl flow generating passages 46, the swirl flow generating passage 46 that is downstream in the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44 has a smaller angle of inclination toward the center of the auxiliary chamber than the swirl flow generating passage 46 that is upstream.

In the example shown in FIG. 3, the partition 16 has seven swirl flow generating communication passages 46 (46p to 46v), but the angle of inclination of the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44 toward the auxiliary chamber center gradually decreases from the upstream side to the downstream side (46p → 46q → 46r → 46s → 46t → 46u → 46v) (θ1>θ2>θ3>θ4>θ5>θ6>θ7).

[Engine 1 Operation]
In the engine 1 according to the first embodiment described above, the fuel injected from the direct injector 18 collides with the main chamber side wall surface 16b of the partition wall 16 during the compression stroke of the engine 1, and a fuel-rich mixture is generated around the main chamber side opening 44b of the fuel inflow communication passage 44. Then, the mixture is supplied from the main chamber 24 to the auxiliary chamber 36 during the compression stroke of the engine 1. A rich fuel mixture is supplied from the fuel inflow communication passage 44, and the mixture supplied from the swirl flow generating communication passage 46 swirls in the auxiliary chamber to generate a swirl flow. The rich fuel mixture also swirls due to this swirl flow, but since the mixture continues to be supplied to the auxiliary chamber through the swirl flow generating communication passage 46 even after the fuel injection from the direct injector 18 is finished, the lean fuel mixture supplied to the auxiliary chamber later swirls in the auxiliary chamber (outer periphery), and the rich fuel mixture supplied to the auxiliary chamber earlier gathers at the center of the auxiliary chamber. This allows a swirl flow of the lean fuel mixture to be formed around the rich fuel mixture (stratification).

Next, during the compression stroke of the engine 1, the spark plug 20 ignites the rich fuel mixture in the auxiliary chamber. The mixture in the auxiliary chamber then becomes a flame flow FF and is injected into the main chamber through the fuel inflow passage 44 and the swirl flow generating passage 46, combusting the mixture in the main chamber.

[effect]
According to the engine 1 of the first embodiment described above, the downstream swirl flow generating communication passage 46 has a smaller angle of inclination with respect to the direction toward the center of the auxiliary chamber 36 than the upstream swirl flow generating communication passage 46 in the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44, so that the downstream swirl flow generating communication passage 46 (46v) can be disposed closer to the fuel inflow communication passage 44. This allows the flame flows FF injected from at least one fuel inflow communication passage 44 and at least two or more swirl flow generating communication passages 46 to be injected evenly in the circumferential direction of the main chamber 24.

[Embodiment 2]
The overall configuration and the overall operation of the engine 1 according to the second embodiment are the same as the overall configuration and the overall operation of the engine 1 according to the first embodiment.

[Partition wall details]
FIG. 4 is a cross-sectional view of the partition wall 16 according to the second embodiment, and corresponds to the plan cross-sectional view (FIG. 3) of the partition wall 16 according to the first embodiment described above.

The outer shape of the partition 16 and the shape of the auxiliary chamber 36 are the same as those of the partition 16 and the auxiliary chamber 36 in the first embodiment described above. The configuration of the fuel inflow passage 44 provided in the partition 16 is also the same.

As shown in FIG. 4, of the two or more swirl flow generating communication passages 46, the flow path cross-sectional areas A1 to A7 of the swirl flow generating communication passages 46 located upstream are larger than those of the swirl flow generating communication passages 46 located downstream in the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44.

In the example shown in FIG. 4, the partition 16 has seven swirl flow generating communication passages 46 (46p to 46v), but in the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44, the minimum flow passage cross-sectional areas A1 to A7 gradually increase from downstream to upstream (46v → 46u → 46t → 46s → 46r → 46q → 46p) (A7<A6<A5<A4<A3<A2<A1).

For example, as shown in FIG. 4, when the flow passage diameters D1 to D7 of the seven swirl flow generating passages 46 (46p to 46v) are constant, the flow passage diameters D1 to D7 gradually increase from the downstream side to the upstream side (46v → 46u → 46t → 46s → 46r → 46q → 46p) in the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44 (D7<D6<D5<D4<D3<D2<D1). The other configurations of the swirl flow generating communication passages 46 are the same as the configuration of the swirl flow generating communication passages 46 in the first embodiment. In addition, the operation of the engine 1 in the second embodiment described above is the same as the operation of the engine 1 in the first embodiment described above.

[effect]
According to the engine 1 of the second embodiment described above, the minimum flow passage cross-sectional areas A1 to A7 of the upstream swirl flow generating passage 46 are larger than the downstream swirl flow generating passage 46 in the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44, so that the effective diameter of the upstream swirl flow generating passage 46 can be made closer to the effective diameter of the downstream swirl flow generating passage 46. This makes it possible to make the momentum of the flame flow FF injected from the upstream swirl flow generating passage 46 closer to the momentum of the flame flow FF injected from the downstream swirl flow generating passage 46.

[Embodiment 3]
The overall configuration and the overall operation of the engine 1 according to the third embodiment are the same as the overall configuration and the overall operation of the engine 1 according to the first embodiment.

[Partition wall details]
FIG. 5 is a cross-sectional view of the partition wall 16 according to the second embodiment, and corresponds to the plan cross-sectional view (FIG. 3) of the partition wall 16 according to the first embodiment described above.

The outer shape of the partition 16 and the shape of the auxiliary chamber 36 are the same as those of the partition 16 and the auxiliary chamber 36 in the first embodiment described above. The configuration of the fuel inflow passage 44 provided in the partition 16 is also the same.

As shown in FIG. 5, of the two or more swirl flow generating communication passages 46, the swirl flow generating communication passage 46 located upstream of the swirl flow generating communication passage 46 located downstream of the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44 has a larger opening 46a on the auxiliary chamber side.

In the example shown in FIG. 5, the partition 16 has seven swirl flow generating passages 46 (46p-46v), but in the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow passage 44, the auxiliary chamber side opening 46a becomes gradually larger from downstream to upstream (46v→46u→46t→46s→46r→46q→46p) (B7<B6<B5<B4<B3<B2<B1).

For example, as shown in FIG. 5, the seven swirl flow generating communication passages 46 (46p to 46v) have gradually increasing radii of curvature on the upstream side of the auxiliary chamber opening 46a from downstream to upstream in the circumferential flow SF of gas generated in the auxiliary chamber 36 with the fuel inflow communication passage 44 as the base point (r7<r6<r6<r5<r6<r7). The rest of the configuration of the swirl flow generating communication passages 46 is the same as the configuration of the swirl flow generating communication passages 46 in embodiment 1. Furthermore, the operation of the engine 1 in embodiment 3 described above is the same as the operation of the engine 1 in embodiment 1 described above.

[effect]
According to the engine 1 of the third embodiment described above, the auxiliary chamber side opening 46a of the upstream swirl flow generating passage 46 is larger than that of the downstream swirl flow generating passage 46 in the circumferential flow SF of gas flowing into the auxiliary chamber starting from the fuel inflow passage 44, so that the effective diameter of the upstream swirl flow generating passage 46 can be made closer to that of the downstream swirl flow generating passage 46. This makes it possible to make the momentum of the flame flow FF injected from the upstream swirl flow generating passage 46 closer to that of the downstream swirl flow generating passage 46.

In addition, the upstream swirl flow generating passage 46 has a larger radius of curvature upstream than the downstream swirl flow generating passage 46 in the circumferential flow SF of gas flowing into the auxiliary chamber starting from the fuel inflow passage 44, so separation of the flame flow FF from the inner wall surface of the swirl flow generating passage 46 is suppressed, and the effective diameter of the upstream swirl flow generating passage 46 can be made closer to the effective diameter of the downstream swirl flow generating passage 46. This allows the momentum of the flame flow FF injected from the upstream swirl flow generating passage 46 to be made closer to the momentum of the flame flow FF injected from the downstream swirl flow generating passage 46.

[Embodiment 4]
The overall configuration and the overall operation of the engine 1 according to the fourth embodiment are the same as the overall configuration and the overall operation of the engine 1 according to the first embodiment.

[Partition wall details]
FIG. 6 is a cross-sectional view of the partition wall 16 according to the fourth embodiment, and corresponds to the plan cross-sectional view (FIG. 3) of the partition wall 16 according to the first embodiment described above.

The outer shape of the partition 16 and the shape of the auxiliary chamber 36 are the same as those of the partition 16 and the auxiliary chamber 36 in the first embodiment described above. The configuration of the fuel inflow passage 44 provided in the partition 16 is also the same.

6, the flow passage cross-sectional area of each of the two or more swirl flow generating communication passages 46 increases from the main chamber side opening 46b toward the auxiliary chamber side opening 46a. The expansion ratio of the flow passage cross-sectional area of the upstream swirl flow generating communication passage 46 is greater than that of the downstream swirl flow generating communication passage 46.

In the example shown in FIG. 6, the partition wall 16 has seven swirl flow generating communication passages 46 (46p to 46v), and in the circumferential flow SF of gas generated in the auxiliary chamber starting from the fuel inflow communication passage 44, the expansion ratio of the flow passage cross-sectional area gradually increases from the downstream side to the upstream side (46v → 46u → 46t → 46s → 46r → 46q → 46p). The other configurations of the swirl flow generating communication passages 46 are the same as the configuration of the swirl flow generating communication passages 46 in embodiment 1. The operation of the engine 1 in embodiment 2 described above is the same as the operation of the engine 1 in embodiment 1 described above.

[effect]
According to the engine 1 of the above-described fourth embodiment, the flow passage cross-sectional area of the upstream swirl flow generating passage 46 is larger than that of the downstream swirl flow generating passage 46 in the circumferential flow SF of gas flowing into the auxiliary chamber starting from the fuel inflow communication passage 44, so that the effective diameter of the upstream swirl flow generating passage 46 can be made closer to that of the downstream swirl flow generating passage 46. This makes it possible to make the momentum of the flame flow FF injected from the upstream swirl flow generating passage 46 closer to that of the downstream swirl flow generating passage 46.

[Embodiment 5]
The overall configuration and the overall operation of the engine 1 according to the above-described fifth embodiment are the same as the overall configuration and the overall operation of the engine 1 according to the first embodiment.

[Partition wall details]
FIG. 7 is a cross-sectional view of the partition wall 16 according to the fifth embodiment, and corresponds to the side cross-sectional view (FIG. 2) of the partition wall 16 according to the first embodiment. As shown in FIG. 7, the partition wall 16 has an auxiliary chamber 36 having a shape in which a cylinder and a truncated cone are combined. The cylinder side of the auxiliary chamber 36 constitutes the auxiliary chamber base 40 located on the cylinder head side, and the truncated cone side constitutes the auxiliary chamber tip 42 located on the piston side. The maximum cross-sectional area of the auxiliary chamber tip 42 is smaller than the minimum cross-sectional area of the auxiliary chamber base 40, and a step surface 48 is provided between the auxiliary chamber base 40 and the auxiliary chamber tip 42. The step surface 48 is provided so as to gradually narrow from the auxiliary chamber base 40 toward the auxiliary chamber tip 42, but is not limited to this, and may be provided so as to form a flat surface. The other configurations are the same as those of the partition wall 16 according to the first embodiment.

[effect]
According to the engine 1 of the above-mentioned fifth embodiment, by making the maximum cross-sectional area of the pre-chamber tip 42 smaller than the minimum cross-sectional area of the pre-chamber base 40, a strong swirl flow can be generated at the pre-chamber tip 42. In addition, the flame flow FF ignited at the pre-chamber base 40 separates at the step surface 48, so that the flame flow FF can be ejected from two or more swirl flow generating communication passages 46 simultaneously.

1 Engine 10 Piston 12 Cylinder block 14 Cylinder head 16 Partition wall 16a Sub-chamber side wall surface 16b Main chamber side wall surface 18 Injection nozzle (direct injector)
20 Spark plug 22 Cylinder 24 Main chamber 26 Intake port 28 Exhaust port 30 Intake valve 32 Exhaust valve 34 Injection nozzle (port injector)
36 Auxiliary chamber 38 Flange 40 Auxiliary chamber base 42 Auxiliary chamber tip 44 Fuel inflow passage 44b Main chamber side opening 46, 46p to 46v Swirl flow generating passage 46a Auxiliary chamber side opening 46b Main chamber side opening 48 Step surface FE Fuel FF Flame flow RG Injection range SF of direct injector Circumferential flow of gas generated in the auxiliary chamber θ1 to θ7 Angle of inclination A1 to A7 of the swirl flow generating passage with respect to the direction toward the center of the auxiliary chamber Minimum flow path cross-sectional area of the swirl flow generating passage

Claims (5)

The piston and
a cylinder block provided with a cylinder in which the piston reciprocates;
a cylinder head fixed to the cylinder block and defining a main chamber between the cylinder head and the piston;
a partition wall provided on the main chamber side of the cylinder head and defining an auxiliary chamber within the main chamber;
an injection nozzle that injects fuel into the main chamber;
A spark plug disposed in the sub-chamber;
Equipped with
The partition wall is
at least one fuel inflow communication passage that is provided straight toward the center of the auxiliary chamber in the circumferential direction of the cylinder and leads from the main chamber to the auxiliary chamber;
at least two swirl flow generating communication passages inclined with respect to a direction toward a center of the auxiliary chamber in a circumferential direction of the cylinder, the swirl flow generating communication passages leading from the main chamber to the auxiliary chamber;
Including,
a swirl flow generating passage located downstream of the at least two swirl flow generating passages has a smaller inclination angle with respect to a direction toward a center of the auxiliary chamber than a swirl flow generating passage located upstream in a circumferential flow of gas generated in the auxiliary chamber starting from the fuel inflow communication passage,
engine. The engine of claim 1, wherein the minimum flow passage cross-sectional area of the upstream swirl flow generating passage is greater than that of the downstream swirl flow generating passage. the upstream swirl flow generating communication passage has a larger opening on the auxiliary chamber side than the downstream swirl flow generating communication passage;
An engine as claimed in claim 1 or 2. a flow passage cross-sectional area of each of the at least two swirl flow generating communication passages increases from an opening on the main chamber side toward an opening on the auxiliary chamber side ,
an expansion ratio of the flow passage cross-sectional area of the upstream swirl flow generating communication passage is larger than that of the downstream swirl flow generating communication passage;
An engine according to any one of claims 1 to 3. The partition wall has:
a tip portion of the auxiliary chamber to which the at least two swirl flow generating communication passages communicate;
an auxiliary chamber base portion provided closer to the cylinder head than the auxiliary chamber tip portion;
a step surface provided between the auxiliary chamber tip portion and the auxiliary chamber base portion;
was established,
The maximum cross-sectional area of the pre-chamber tip is smaller than the minimum cross-sectional area of the pre-chamber base.
An engine according to any one of claims 1 to 4.

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