engine

Abstract

This engine comprises: a piston; a cylinder block having a cylinder in which the piston reciprocates; a cylinder head that is secured to the cylinder block, and forms a main chamber between the piston and the cylinder head; a partition wall that is provided on the main chamber side of the cylinder head, and forms a sub-chamber in 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 has a fuel inflow communication passage that is provided on the injection nozzle side in a circumferential direction of the cylinder, and leads from the main chamber to the sub-chamber, and a protruding wall protruding from a main chamber-side wall surface of the partition wall. The protruding wall surrounds a main chamber-side opening of the fuel inflow communication passage, and forms a receiving surface that is flat or recessed from an outer peripheral edge of the protruding wall toward an outside opening of the fuel flow communication passage.

Description

[Technical Field]

[0001] The present disclosure relates to engines. [Background technology]

[0002] Patent Document 1 discloses an internal combustion engine in which an auxiliary chamber is provided separated from a main chamber by a partition wall, a communication passage is formed in the partition wall to connect the main chamber and the auxiliary chamber, an ignition plug is disposed in the auxiliary chamber, the air-fuel mixture in the auxiliary chamber is ignited by the ignition plug, and the flame formed in the auxiliary chamber at this time is ejected into the main chamber via the communication passage. In this internal combustion engine, a recessed groove is formed in the outer wall surface of the partition wall, and a communication passage is formed in the recessed groove, and fuel is injected toward the recessed groove from a fuel injection valve disposed in the main chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-204835 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the internal combustion engine disclosed in Patent Document 1, when the fuel injected by the fuel injection valve (injection nozzle) deviates from the groove, it flows around to the other side of the partition wall, and a fuel-rich mixture is generated in the main chamber. If a fuel-rich mixture is generated in a part of the main chamber in this way, it is undesirable because it generates a large amount of nitrogen oxides (NOx).

[0005] In view of the above circumstances, at least one embodiment of the present invention has an object to provide an engine that can prevent fuel injected from an injection nozzle from flowing around to the opposite side of a partition wall. [Means for solving the problem]

[0006] BookAn engine according to at least one embodiment of the present invention comprises a cylinder block provided with a piston and a cylinder in which the piston reciprocates, a cylinder head fixed to the cylinder block and defining a main chamber between the cylinder block 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 for injecting fuel into the main chamber, and an ignition plug installed in the auxiliary chamber, the partition wall being provided on the injection nozzle side in the circumferential direction of the cylinder and including a fuel inflow communication passage leading from the main chamber to the auxiliary chamber, at least one swirl flow generating communication passage provided at a position different from the fuel inflow communication passage in the circumferential direction of the cylinder and obliquely provided with respect to a direction toward the center of the auxiliary chamber in the circumferential direction of the cylinder; a convex wall protruding from the main chamber side wall surface of the partition wall; a recessed portion recessed toward the partition wall from a line connecting an outer peripheral edge of the convex wall and a portion of the at least one swirl flow generating communication passage adjacent to the convex wall, the portion having a main chamber side opening; The convex wall surrounds the main chamber side opening of the fuel inflow communication passage and forms a receiving surface that is flat or recessed from the outer circumferential edge of the convex wall toward the main chamber side opening of the fuel inflow communication passage.

[0007] above The With this configuration, the convex wall protrudes from the main chamber side wall surface of the partition, so the convex wall does not affect the shape of the auxiliary chamber side wall surface, and it is possible to prevent fuel injected from the injection nozzle from flowing around to the side of the partition opposite the fuel inflow communicating passage, thereby preventing a fuel-rich mixture from being generated on the side of the partition opposite the fuel inflow communicating passage. Also, The air-fuel mixture that flows into the pre-chamber through at least one swirl flow generating communication generates a swirl flow in the pre-chamber, so that a fuel-rich air-fuel mixture and a fuel-lean air-fuel mixture can be stratified in the pre-chamber. Also, The air-fuel mixture that has passed over the outer periphery of the convex wall is more likely to separate from the main-chamber-side wall surface of the partition, making it easier for the air-fuel mixture that has passed over the outer periphery of the convex wall to enter through the swirl flow generating passage. Furthermore, the air-fuel mixture that has passed over the main-chamber-side wall surface becomes a vortex, generating negative pressure, causing the air-fuel mixture that has passed over the outer periphery of the convex wall to stagnate. This allows the air-fuel mixture that has passed over the outer periphery of the convex wall to be effectively introduced into the pre-chamber. [Effects of the Invention]

[0008] According to at least one embodiment of the present invention, it is possible to prevent fuel injected from the injection nozzle from flowing around to the opposite side of the partition wall. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically showing the overall configuration of an engine according to an embodiment. [Figure 2] FIG. 2 is a perspective view schematically illustrating the partition wall shown in FIG. [Figure 3] 3 is a cross-sectional view of the partition wall shown in FIG. 2 taken along line III-III. [Figure 4] 4 is a cross-sectional view of the partition wall shown in FIG. 2 taken along line IV-IV. [Figure 5] FIG. 2 is a diagram showing the flow of a fuel-rich mixture injected from an injection nozzle. [Figure 6] FIG. 10 is a diagram showing the flow of a swirl flow that separates at a step surface. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative positions, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0011] [Overall engine configuration] FIG. 1 is a cross-sectional view schematically illustrating the overall configuration of an engine 1 according to an embodiment. As shown in FIG. 1, the engine 1 according to the 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 defines a main chamber (combustion chamber) 24 between the piston 10 and the cylinder head 14. 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 is provided with an intake valve 30 that opens and closes the intake port 26, and the exhaust port 28 is provided with an exhaust valve 32 that opens and closes the exhaust port 28. For example, the intake port 26 is provided with an injection nozzle 34 (hereinafter referred to as a "port injector 34") that injects 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 the "direct injector 18") injects fuel into the main chamber. The spark plug 20 is installed in the auxiliary chamber and is capable of igniting the air-fuel mixture that flows into the auxiliary chamber.

[0012] [Engine 1 overall operation] In the engine 1 according to this 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. This causes an air-fuel mixture to be supplied from the intake port 26 to the main combustion chamber 24. In the engine 1 according to this embodiment, the air-fuel mixture in the main combustion chamber becomes leaner than the stoichiometric air-fuel ratio.

[0013] The direct injector 18 injects fuel during the compression stroke when the intake valve 30 closes the intake port 26 and the piston 10 rises. As a result, the fuel injected from the direct injector 18 is supplied to the pre-chamber 36 together with the air-fuel mixture in the main chamber. The air-fuel mixture in the pre-chamber is then ignited by the spark plug 20. In the engine 1 according to this embodiment, the air-fuel mixture in the pre-chamber has an air-fuel ratio equivalent to the stoichiometric air-fuel ratio.

[0014] During the expansion stroke when the piston 10 is moved down, the air-fuel mixture in the auxiliary chamber is ignited by the spark plug 20 and injected into the main chamber as a flame current, causing the air-fuel mixture in the main chamber to combust.

[0015] 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 combustion 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 this embodiment, the port injector 34 injects fuel during the intake stroke, but it may also inject fuel during the exhaust stroke. In this case, fuel is supplied to the main combustion chamber 24 during the intake stroke.

[0016] [Configuration of bulkhead 16] FIG. 2 is a perspective view schematically illustrating the partition wall 16 shown in FIG. 1. FIG. 3 is a cross-sectional view of the partition wall 16 shown in FIG. 2 taken along line III-III, and FIG. 4 is a cross-sectional view of the partition wall 16 taken along line IV-IV. As shown in FIG. 2, the partition wall 16 has an external shape that resembles a combination of a cylinder and a truncated cone. A flange 38 is provided at the cylindrical end of the partition wall 16, and this flange 38 secures the partition wall 16 to the main chamber side of the cylinder head 14. As a result, the cylindrical side of the partition wall 16 forms the base end that is secured to the cylinder head 14, and the truncated cone side forms the tip end that faces the piston. As shown in FIG. 3, the partition wall 16 contains an auxiliary chamber 36 that resembles a combination of a cylinder and a truncated cone. The cylindrical side of the auxiliary chamber 36 forms an auxiliary chamber base 40 that faces the cylinder head, and the truncated cone side forms an auxiliary chamber tip 42 that faces the piston. The maximum cross-sectional area of ​​the pre-chamber tip 42 is smaller than the minimum cross-sectional area of ​​the pre-chamber base 40, and a step surface 44 is provided between the pre-chamber base 40 and the pre-chamber tip 42. The step surface 44 is provided so as to gradually narrow from the pre-chamber base 40 towards the pre-chamber tip 42, but is not limited to this and may be provided so as to form a flat surface.

[0017] The partition wall 16 has a fuel inflow communicating passage 46 at its tip end that connects the main chamber 24 to the auxiliary chamber 36 (auxiliary chamber tip end 42). As shown in Fig. 4, the fuel inflow communicating passage 46 is provided on the direct injector side in the circumferential direction of the cylinder 22. The fuel inflow communicating passage 46 is preferably provided within the injection range RG of the direct injector 18 in the circumferential direction of the cylinder 22, and more preferably at a position directly opposite the injection direction of the direct injector 18 in the circumferential direction of the cylinder 22. When the fuel inflow communicating passage 46 is provided at a position directly opposite the injection direction of the direct injector 18 in the circumferential direction of the cylinder 22, the fuel inflow communicating passage 46 is provided on an extension of the injection direction of the direct injector 18 and extends straight toward the center of the auxiliary chamber 36. 3, the fuel inflow communication passage 46 is inclined toward the cylinder head 14 as it moves toward the inside (center) of the sub chamber 36 so that fuel injected from the direct injector 18 flows into the fuel inflow communication passage 46 during the compression stroke of the engine 1, and more preferably is provided along the injection direction of the direct injector 18. Although the number of fuel inflow communication passages 46 is, for example, one, the number is not limited to one and may be two or more.

[0018] As shown in FIG. 2 , the partition 16 has a protruding wall 48 protruding from the main-chamber-side wall surface 16 a of the partition 16 on the tip side thereof. The protruding wall 48 surrounds the main-chamber-side opening 46 a of the fuel inflow communicating passage 46 and, as shown in FIGS. 3 and 4 , forms a receiving surface 50 that is recessed from the outer circumferential edge 48 a of the protruding wall 48 toward the main-chamber-side opening 46 a of the fuel inflow communicating passage 46. The receiving surface 50 does not necessarily have to be recessed from the outer circumferential edge 48 a of the protruding wall 48 toward the main-chamber-side opening 46 a of the fuel inflow communicating passage 46, but may be flat. The receiving surface 50 that is recessed from the outer circumferential edge 48 a of the protruding wall 48 toward the main-chamber-side opening 46 a of the fuel inflow communicating passage 46 is a curved surface whose periphery is the outer circumferential edge 48 a of the protruding wall 48, and the main-chamber-side opening 46 a of the fuel inflow communicating passage 46 is, for example, provided at its most recessed position.

[0019] As shown in FIG. 4, the partition wall 16 has at least one swirl flow generating communication passage 52 on its tip side. Like the fuel inflow communication passage 46, the at least one swirl flow generating communication passage 52 is a communication passage that leads from the main combustion chamber 24 to the auxiliary combustion chamber 36, and is located at a different position in the circumferential direction of the cylinder 22 from the fuel inflow communication passage 46. The at least one swirl flow generating communication passage 52 is located at an angle with respect to the direction toward the center of the auxiliary combustion chamber 36 in the circumferential direction of the cylinder 22. Also, as shown in FIG. 3, the at least one swirl flow generating communication passage 52 is located horizontally or at an angle with respect to the horizontal. The swirl flow generating communication passage 52 is preferably located at an angle so that it approaches the cylinder head 14 as it moves inward of the auxiliary combustion chamber 36, so that the air-fuel mixture in the main combustion chamber flows into the auxiliary combustion chamber during the compression stroke of the engine 1.

[0020] At least one swirl flow generating communication passage 52 is two or more swirl flow generating communication passages 52. For example, the partition 16 shown in Fig. 4 has five swirl flow generating communication passages 52, but is not limited to this. In a cross section passing through the auxiliary chamber side openings 52a of the two or more swirl flow generating communication passages 52, the auxiliary chamber side wall surface 16b of the partition 16 is circular.

[0021] Furthermore, the thickness t1 of the partition wall 16 at the portion where the fuel inflow communication passage 46 is provided is the same as the thickness t2 of the portion where at least one swirl flow generating communication passage 52 is provided.

[0022] 3 and 4, the partition wall 16 has a communication passage 54 at its tip. The communication passage 54 is a communication passage that leads from the main chamber 24 to the auxiliary chamber 36. The communication passage 54 is provided, for example, along the central axis of the auxiliary chamber 36.

[0023] As shown in FIG. 4, the partition wall 16 has a recess 56 that is recessed toward the partition wall from a straight line LN that connects the outer peripheral edge 48a of the convex wall 48 and the portion of at least one swirl flow generating communication passage 52 adjacent to the convex wall 48 where the main chamber side opening 52b is provided.

[0024] [Engine 1 Operation] In the engine 1 described above, fuel injected from the direct injector 18 collides with the receiving surface 50 during the compression stroke of the engine 1, generating a fuel-rich mixture around the main-chamber-side opening 46a of the fuel inlet communicating passage 46. Then, during the compression stroke of the engine 1, the mixture is supplied from the main combustion chamber 24 to the auxiliary combustion chamber 36. A rich mixture is supplied from the fuel inlet communicating passage 46, and the mixture supplied from the swirl flow generating communicating passage 52 swirls within the auxiliary combustion chamber, generating a swirl flow. This swirl flow also swirls the rich mixture. Even after fuel injection from the direct injector 18 is completed, the mixture continues to be supplied to the auxiliary combustion chamber through the swirl flow generating communicating passage 52. Therefore, the lean mixture supplied later swirls within the auxiliary combustion chamber (on the outer periphery), causing the rich mixture supplied earlier to gather toward the center of the auxiliary combustion chamber. This results in a swirling flow of the lean mixture around the rich mixture (stratification).

[0025] Next, the spark plug 20 ignites the rich fuel mixture in the pre-chamber during the compression stroke of the engine 1. The mixture in the pre-chamber then turns into a flame, which passes through the fuel inflow communicating passage 46 and the swirl flow generating communicating passage 52 and is injected into the main chamber, combusting the mixture in the main chamber.

[0026] [effect] According to the engine 1 described above, the convex wall 48 protrudes from the main-chamber-side wall surface 16a of the partition 16, so the convex wall 48 does not affect the shape of the auxiliary-chamber-side wall surface, and it is possible to prevent the fuel injected from the direct injector 18 from flowing around to the side of the partition 16 opposite the fuel inflow communicating passage 46. This makes it possible to prevent a fuel-rich mixture from being generated on the side of the partition 16 opposite the fuel inflow communicating passage 46.

[0027] Furthermore, the air-fuel mixture that flows into the pre-chamber through at least one swirl flow generating communication passage 52 generates a swirl flow in the pre-chamber, so that a swirl flow of a lean air-fuel mixture can be formed around a rich air-fuel mixture in the pre-chamber (stratification).

[0028] Furthermore, in a cross section passing through two or more swirl flow generating communication passages 52, the pre-chamber side wall surface 16b of the partition 16 has a circular shape, so the air-fuel mixture that flows in through the swirl flow generating communication passages 52 swirls along the pre-chamber side wall surface 16b, generating a strong swirl flow in the pre-chamber.

[0029] Furthermore, since the thickness t2 of the partition wall 16 where the fuel inflow communicating passage 46 is provided is the same as the thickness t1 of the portion where at least one swirl flow generating communicating passage 52 is provided, the length L1 of the swirl flow generating communicating passage 52 can be made close to the length L2 of the fuel inflow communicating passage 46. This makes it possible to achieve a balance between the flame that is ignited in the pre-chamber and ejected from the fuel inflow communicating passage 46 and the flame that is ejected from the swirl flow generating communicating passage 52.

[0030] Furthermore, the partition wall 16 has a recess 56 that is recessed toward the partition wall 16 relative to a straight line LN that connects the outer peripheral edge 48a of the convex wall 48 and the portion of at least one swirl flow generating communicating passage 52 adjacent to the convex wall 48 where the main-chamber-side opening 52b is provided. As a result, as shown in FIG. 5 , the air-fuel mixture that has passed over the outer peripheral edge 48a of the convex wall 48 is easily separated from the main-chamber-side wall surface 16a of the partition wall 16, and is easily able to enter the swirl flow generating communicating passage 52 through the outer peripheral edge 48a of the convex wall 48. Furthermore, the air-fuel mixture that has passed over the main-chamber-side wall surface 16a forms a vortex, generating negative pressure, causing the air-fuel mixture that has passed over the outer peripheral edge 48a of the convex wall 48 to stagnate. This allows the air-fuel mixture that has passed over the outer peripheral edge 48a of the convex wall 48 to be effectively introduced into the pre-chamber.

[0031] Furthermore, by making the maximum cross-sectional area of ​​the pre-chamber tip 42 of the partition wall 16 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. As shown in Figure 6, the swirl flow separates at the step surface 44, thinning the fuel at the step surface 44. Since the flame travels through a fuel-rich region, it moves toward the center, and when at least one swirl flow generating passage is two or more swirl flow generating communicating passages 52, it is possible to eject the flame from two or more swirl flow generating communicating passages 52 simultaneously. [Explanation of symbols]

[0032] 1 engine 10 pistons 12 Cylinder block 14 Cylinder head 16 Bulkhead 16a Main room side wall 16b Side wall of the antechamber 18 Injection nozzle (direct injector) 20 Spark plug 22 cylinders 24 Main chamber (combustion chamber) 26 Intake port 28 Exhaust port 30 Intake valve 32 Exhaust valve 34 Injection nozzle (port injector) 36 Pre-combustion chamber (pre-combustion chamber) 38 flange 40 Subventricular base 42 Tip of subchamber 44 Step surface 46 Fuel inflow passage 46a Main room side opening 48 Convex Wall 48a outer edge 50 Receiving surface 52 Swirl flow generation communication passage 52a Antechamber side opening 52b Main room side opening 54 Communication path 56 Recess RG Direct Injector Injection Range

Claims

1. 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 installed in the sub-chamber; Equipped with The partition wall is a fuel inflow communication passage provided on the injection nozzle side in the circumferential direction of the cylinder and communicating from the main chamber to the sub chamber; at least one swirl flow generating communication passage provided at a position different from the fuel inflow communication passage in the circumferential direction of the cylinder and obliquely provided with respect to a direction toward the center of the auxiliary chamber in the circumferential direction of the cylinder; a convex wall protruding from a main chamber side wall surface of the partition wall; a recessed portion recessed toward the partition wall relative to a line connecting an outer peripheral edge of the convex wall and a portion of the at least one swirl flow generating communication passage adjacent to the convex wall, the portion having a main chamber side opening; and the protruding wall surrounds the main chamber side opening of the fuel inflow communication passage and forms a receiving surface that is flat or recessed from an outer circumferential edge of the protruding wall toward the main chamber side opening of the fuel inflow communication passage. engine.

2. The at least one swirl flow generating passage is two or more swirl flow generating passages, In a cross section passing through the auxiliary chamber side openings of the two or more swirl flow generating communication passages, the auxiliary chamber side wall surface of the partition wall has a circular shape.

10. The engine of claim 1.

3. a wall thickness of the partition wall at a portion where the fuel inflow communication passage is provided is the same as a wall thickness of a portion where the at least one swirl flow generating communication passage is provided; 3. An engine according to claim 1 or 2.

4. The partition wall has: a tip end of the auxiliary chamber to which the at least one swirl flow generating communication passage communicates; 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 end and the auxiliary chamber base; is established, The maximum cross-sectional area of ​​the antechamber tip portion is smaller than the minimum cross-sectional area of ​​the antechamber base portion. An engine according to any one of claims 1 to 3.

Images