JP7768352B2 - engine - Google Patents

Description

This disclosure relates to engines.

Patent Document 1 discloses an internal combustion engine that has an auxiliary chamber separated from a main chamber by a partition wall, a communication passage formed within the partition wall that connects the main and auxiliary chambers, an ignition plug disposed within the auxiliary chamber, and an air-fuel mixture ignited by the spark plug, with the flame formed within the auxiliary chamber ejected into the main chamber via the communication passage. In this internal combustion engine, a groove is formed in the outer wall surface of the partition wall, and a communication passage is formed within the groove, and fuel is injected toward the groove from a fuel injection valve disposed within the main chamber.

Japanese Patent Application Laid-Open No. 2004-204835

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

In view of the above, at least one embodiment of the present invention aims to provide an engine that can prevent fuel injected from the injection nozzle from flowing around to the other side of the partition.

An engine according to at least one embodiment of the present invention includes 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 piston and the cylinder block, 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 a fuel inflow communication passage leading from the main chamber to the auxiliary chamber, and a fuel inflow communication passage extending in the circumferential direction of the cylinder the partition wall has at least one swirl flow generating communication passage provided at a position different from the fuel inflow communication passage and tilted in the circumferential direction of the cylinder toward the center of the auxiliary chamber; a convex wall protruding from the main chamber side wall surface of the partition wall ; and a recessed portion recessed toward the partition wall from a line connecting the outer circumferential edge of the convex wall and a portion where the main chamber side opening of the at least one swirl flow generating communication passage adjacent to the convex wall is provided, wherein 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.

According to the above configuration, the convex wall protrudes from the main-chamber-side wall surface of the partition wall. Therefore, the convex wall does not affect the shape of the pre-chamber-side wall surface, and fuel injected from the injection nozzle is prevented from flowing around to the side opposite the fuel inflow communication passage of the partition wall. This prevents a fuel-rich mixture from being generated on the side opposite the fuel inflow communication passage of the partition wall. Furthermore, the mixture that flows into the pre-chamber through at least one swirl flow generating passage generates a swirl flow in the pre-chamber, thereby stratifying a fuel-rich mixture and a fuel-lean mixture in the pre-chamber. Furthermore, the mixture that has passed over the outer peripheral edge of the convex wall is more likely to separate from the main-chamber-side wall surface of the partition wall, making it easier for the mixture that has passed over the outer peripheral edge of the convex wall to enter through the swirl flow generating communication passage. Furthermore, the mixture that has passed over the main-chamber-side wall surface forms a vortex, generating negative pressure, which causes the mixture that has passed over the outer peripheral edge of the convex wall to stagnate. This allows the mixture that has passed over the outer peripheral edge of the convex wall to be effectively introduced into the pre-chamber.

At least one embodiment of the present invention can prevent fuel injected from the injection nozzle from flowing around to the opposite side of the partition wall.

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

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

[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 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 defines a main 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 combustion chamber 24, but this is not a limitation. 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 combustion 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 spark plug 20 is installed 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 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, thereby supplying an air-fuel mixture 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.

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 this embodiment, the mixture in the auxiliary chamber has an air-fuel ratio equivalent to the stoichiometric air-fuel ratio.

During the expansion stroke, when the piston 10 descends, the mixture in the auxiliary chamber is ignited by the spark plug 20, forming a flame stream that is injected into the main chamber, combusting the mixture in the main chamber.

During the exhaust stroke, the exhaust valve 32 opens the exhaust port 28 and the piston 10 rises, expelling the combustion gases from the main chamber. 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 still supplied to the main chamber 24 during the intake stroke.

[Configuration of partition wall 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 auxiliary chamber tip 42 is smaller than the minimum cross-sectional area of the auxiliary chamber base 40, and a step surface 44 is provided between the auxiliary chamber base 40 and the auxiliary chamber tip 42. The step surface 44 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 partition wall 16 has a fuel inflow communication passage 46 at its tip end that connects the main chamber 24 to the auxiliary chamber 36 (auxiliary chamber tip 42). As shown in FIG. 4, the fuel inflow communication passage 46 is located on the direct injector side in the circumferential direction of the cylinder 22. The fuel inflow communication passage 46 is preferably located within the injection range RG of the direct injector 18 in the circumferential direction of the cylinder 22, and more preferably directly opposite the injection direction of the direct injector 18 in the circumferential direction of the cylinder 22. When the fuel inflow communication passage 46 is located directly opposite the injection direction of the direct injector 18 in the circumferential direction of the cylinder 22, the fuel inflow communication passage 46 is located on an extension of the injection direction of the direct injector 18 and extends straight toward the center of the auxiliary chamber 36. As shown in FIG. 3, the fuel inflow communication passage 46 is inclined toward the cylinder head 14 as it moves toward the inside (center) of the auxiliary 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 arranged along the injection direction of the direct injector 18. For example, there is one fuel inflow communication passage 46, but this is not limited to one and there may be two or more.

As shown in FIG. 2, the partition wall 16 has a convex wall 48 protruding from the main chamber-side wall surface 16a of the partition wall 16 at its tip end. The convex wall 48 surrounds the main chamber-side opening 46a 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 peripheral edge 48a of the convex wall 48 toward the main chamber-side opening 46a of the fuel inflow communicating passage 46. The receiving surface 50 does not necessarily have to be recessed from the outer peripheral edge 48a of the convex wall 48 toward the main chamber-side opening 46a of the fuel inflow communicating passage 46, but may be flat. The receiving surface 50 that is recessed from the outer peripheral edge 48a of the convex wall 48 toward the main chamber-side opening 46a of the fuel inflow communicating passage 46 is a curved surface whose periphery is the outer peripheral edge 48a of the convex wall 48. For example, the main chamber-side opening 46a of the fuel inflow communicating passage 46 is located at its most recessed position.

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 connects the main chamber 24 to the auxiliary 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 relative to the direction toward the center of the auxiliary 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 relative to the horizontal. The swirl flow generating communication passage 52 is preferably located at an angle toward the cylinder head 14 as it moves inward toward the auxiliary chamber 36, so that the air-fuel mixture in the main chamber flows into the auxiliary chamber during the compression stroke of the engine 1.

At least one swirl flow generating communication passage 52 is two or more swirl flow generating communication passages 52. For example, the partition wall 16 shown in FIG. 4 has five swirl flow generating communication passages 52, but this 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 wall 16 is circular.

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

As shown in Figures 3 and 4, the partition wall 16 has a communication passage 54 at its tip. The communication passage 54 is a communication passage that connects 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.

Furthermore, 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 connecting 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.

[Engine 1 Operation]
In the engine 1 described above, fuel injected from the direct injector 18 strikes 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 communication passage 46. Then, the mixture is supplied from the main combustion chamber 24 to the auxiliary combustion chamber 36 during the compression stroke of the engine 1. A rich mixture is supplied from the fuel inlet communication passage 46, and the mixture supplied from the swirl flow generating communication passage 52 swirls within the auxiliary combustion chamber, generating a swirl flow. This swirl flow also swirls the rich mixture. Since the mixture continues to be supplied to the auxiliary combustion chamber through the swirl flow generating communication passage 52 even after fuel injection from the direct injector 18 is terminated, 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 creates a swirl flow of the lean mixture around the rich mixture (stratification).

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

[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 communication 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 communication passage 46.

In addition, the air-fuel mixture that flows into the pre-chamber through at least one swirl flow generating communication passage 52 generates a swirl flow within the pre-chamber, creating a swirl flow of lean air-fuel mixture around a rich air-fuel mixture within the pre-chamber (stratification).

In addition, 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 wall 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 within the pre-chamber.

In addition, because the thickness t2 of the partition wall 16 where the fuel inflow communication passage 46 is provided is the same as the thickness t1 of the portion where at least one swirl flow generating communication passage 52 is provided, the length L1 of the swirl flow generating communication passage 52 can be made closer to the length L2 of the fuel inflow communication passage 46. This makes it possible to achieve a balance between the flame ignited in the auxiliary chamber and ejected from the fuel inflow communication passage 46 and the flame ejected from the swirl flow generating communication passage 52.

The partition wall 16 also has a recess 56 that is recessed toward the partition wall 16 from the straight line LN connecting 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. As a result, as shown in FIG. 5 , the mixture gas that has passed over the outer peripheral edge 48a of the convex wall 48 is more likely to separate from the main chamber side wall surface 16a of the partition wall 16, making it easier for the mixture gas that has passed over the outer peripheral edge 48a of the convex wall 48 to enter the swirl flow generating communication passage 52. Furthermore, the mixture gas that has passed over the main chamber side wall surface 16a forms a vortex, generating negative pressure, causing the mixture gas that has passed over the outer peripheral edge 48a of the convex wall 48 to stagnate. This allows the mixture gas that has passed over the outer peripheral edge 48a of the convex wall 48 to be effectively introduced into the auxiliary chamber.

Furthermore, 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, the partition 16 can generate a strong swirl flow at the pre-chamber tip 42. Furthermore, as shown in Figure 6, the swirl flow separates at the step surface 44, thinning the fuel at the step surface 44. Because the flame travels through a fuel-rich region, it moves toward the center, and when at least one swirl flow generating passage is made up of two or more swirl flow generating communication passages 52, it is possible to eject the flame from two or more swirl flow generating communication passages 52 simultaneously.

1 Engine 10 Piston 12 Cylinder block 14 Cylinder head 16 Partition wall 16a Main chamber side wall surface 16b Sub chamber side wall surface 18 Injection nozzle (direct injector)
20 Spark plug 22 Cylinder 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 Pre-chamber base 42 Pre-chamber tip 44 Step surface 46 Fuel inlet communication passage 46a Main chamber side opening 48 Convex wall 48a Outer periphery 50 Receiving surface 52 Swirl flow generating communication passage 52a Pre-chamber side opening 52b Main chamber side opening 54 Communication passage 56 Recess RG Injection range of direct injector

Claims (4)

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,
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. 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 . 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 . 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 portion and the auxiliary chamber base portion,
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 .