Direct injection-type internal combustion engine

Abstract

This direct injection-type internal combustion engine includes, in a combustion chamber, a spark plug and a fuel injection nozzle. The fuel injection nozzle injects fuel toward the spark plug. Formed on a top surface are: an inclined surface that extends along the fuel injection direction as viewed in the cylinder axial direction and is inclined on the cylinder head side toward the fuel injection nozzle; and a pair of side guides that are disposed so as to sandwich the inclined surface in a direction orthogonal to the fuel injection direction. The width of the inclined surface in the crankshaft direction orthogonal to the fuel injection direction is set so as to narrow toward the fuel injection nozzle as viewed in the cylinder axial direction.

Description

direct injection internal combustion engine

[0001] The present invention relates to a direct injection type internal combustion engine equipped with a fuel injection nozzle that injects fuel into a combustion chamber.

[0002] A direct-injection internal combustion engine has been proposed, which includes a combustion chamber formed by a cylinder, a cylinder head, and a piston, an ignition plug located in the center of the cylinder head, and a fuel injection nozzle provided in the combustion chamber for supplying fuel. In such a direct-injection internal combustion engine, an air-fuel mixture is formed in the combustion chamber using intake air supplied into the combustion chamber through an intake port during the intake stroke and fuel supplied by the fuel injection nozzle, and the compressed air-fuel mixture is ignited by the spark plug during the compression stroke.

[0003] During the intake stroke and compression stroke of a direct injection internal combustion engine, a mixture is efficiently formed by a tumble flow formed by the intake air supplied to the combustion chamber.

[0004] To efficiently form such a tumble flow, a direct-injection internal combustion engine is proposed, as described in Patent Document 1, in which the piston top surface is provided with a central raised portion having a cylindrical surface that curves upward toward the intake direction, and outer raised portions that also have cylindrical surfaces and are located on both sides of the central raised portion in the cylinder row direction.

[0005] Japanese Patent Application Publication No. 2000-154724

[0006] In the direct-injection internal combustion engine described in Patent Document 1, multiple independent tumble flows are formed by the central raised portion and the outer raised portion. Therefore, when the engine speed increases, the airflow formed by the central raised portion, which is the mainstream depending on the combustion cycle, becomes weaker, and the balance with the tumble flow caused by the outer raised portion is lost, which can cause significant disruption to the airflow in the combustion chamber.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide a direct injection type internal combustion engine that further stabilizes the tumble flow formed during the compression stroke.

[0008] The above object of the present invention can be achieved by the following configuration. a cylinder head covering one end of the cylinder; a piston having a top surface facing the cylinder head and reciprocating within the cylinder; an ignition plug arranged in the center of the cylinder head within a combustion chamber formed between the cylinder, the cylinder head, and the piston; a fuel injection nozzle arranged within the combustion chamber; and an intake port and an exhaust port provided in the cylinder head on either side of the spark plug, wherein the fuel injection nozzle is arranged on one side of an intake and exhaust direction connecting the intake port and the exhaust port, and injects fuel toward the spark plug, and the top surface of the piston is formed with an inclined surface that extends along the intake and exhaust direction and inclined toward the cylinder head as it approaches the one side, and a pair of side guide portions that are arranged to sandwich the inclined surface in the crankshaft direction that is perpendicular to the intake and exhaust direction and the cylinder axial direction that is the reciprocating direction of the cylinder, and the width of the inclined surface in the crankshaft direction is formed to narrow as it approaches the one side. [2] The direct-injection internal combustion engine according to [1], wherein the inclined surface is formed so that the angle of inclination toward the cylinder head increases stepwise toward the one side. [3] The side guide portion has a side guide surface that inclines toward the cylinder head as it approaches the one side, and the top surface is formed with a downward surface that inclines toward the cylinder head as it approaches from the top of the inclined surface to the one side, and a lateral extension surface that extends from the top of the side guide surface to the one side, and the inclined surface is formed so that the angle formed between an extension line of the inclined surface and the downward surface is larger than the angle formed between an extension line of the side guide surface and the lateral extension surface. [4] The direct-injection internal combustion engine according to [1], wherein the width of the side guide portion in the crankshaft direction is widest at a part corresponding to a center of the piston in the intake / exhaust direction, and is approximately constant from the widest part to the one side.[5] A direct-injection internal combustion engine according to any one of [1] to [4], wherein an auxiliary chamber is provided in the combustion chamber to accommodate the ignition plug, the auxiliary chamber is formed with an injection port that connects the combustion chamber and the auxiliary chamber and injects flame from the auxiliary chamber into the combustion chamber, the side guide portion is formed with a passage portion that extends in the crankshaft direction and connects the inner surface and outer surface of the side guide portion, and the passage portion is formed on an extension line of the injection port.

[0009] According to the direct injection internal combustion engine of the present invention, by narrowing the width of the inclined surface in the direction of fuel injection, the tumble flow formed during the compression stroke can be made more stable.

[0010] FIG. 1 is a cross-sectional view of a main portion showing a schematic configuration of an internal combustion engine according to an embodiment of the present disclosure. FIG. 2 is a plan view in the cylinder axial direction showing a schematic configuration of the internal combustion engine. FIG. 3 is a perspective view of a piston showing the shape of the piston top surface. FIG. 4 is a central cross-sectional view of a piston. FIG. 5(A) is a cross-sectional view of a main portion of the internal combustion engine showing a state in which the piston has risen to the midpoint during the compression stroke, and FIG. 5(B) is a cross-sectional view of a main portion of the internal combustion engine showing a state in which the piston has risen to top dead center during the compression stroke. FIG. 6 is a perspective view of a main portion of the piston showing the flow of airflow guided by the piston top surface. FIG. 7 is a plan view in the cylinder axial direction of the piston top surface showing a flame ejected from the auxiliary chamber. FIG. 8 is a perspective view of the piston top surface showing grooves provided in the side guide portions. FIGS. 9(A) and 9(B) are perspective views of the piston top surface showing alternative examples 1 and 2 of the protrusions.

[0011] A pre-chamber internal combustion engine (hereinafter also simply referred to as "internal combustion engine") employing a direct-injection internal combustion engine according to one embodiment of the present invention will be described with reference to FIGS. 1 to 8. Note that the present invention is not limited to the embodiment described below, and various modifications are possible as long as they have substantially the same configuration as this embodiment and provide similar operational effects.

[0012] In this specification, with respect to the internal combustion engine 1, the cylinder axis direction Z refers to the direction in which a piston slides along a cylinder. When referring to the up-down direction, this refers to the cylinder axis direction Z, with the cylinder head side being "up" and the crankshaft side being "down." This configuration can be seen in FIG. 1 . The intake / exhaust direction X refers to the direction connecting the intake port and the exhaust port. The "intake side" refers to the intake port side of the intake / exhaust direction X, and the "exhaust side" refers to the exhaust port side of the intake / exhaust direction X. The intake / exhaust direction X is also the direction of fuel injection by the fuel injection nozzle. The crankshaft direction Y refers to the extension direction of the crankshaft, and is a direction perpendicular to the cylinder axis direction Z and the intake / exhaust direction X. The crankshaft direction Y is also the direction in which the cylinders are lined up along the crankshaft. This configuration can be seen in FIG. 2 .

[0013] (Overall Configuration) Fig. 1 is a cross-sectional view of a main portion showing a schematic configuration of an internal combustion engine according to an embodiment of the present disclosure, and Fig. 2 is a plan view in the cylinder axis direction Z showing the schematic configuration of the internal combustion engine. The internal combustion engine 1 includes a main combustion chamber 10 and an auxiliary combustion chamber 20 that form combustion chambers, an ignition plug 4, and a fuel injection nozzle 5. The internal combustion engine 1 of this embodiment is an in-line internal combustion engine in which a plurality of cylinders, each including the main combustion chamber 10 and the auxiliary combustion chamber 20, are arranged in line along the crankshaft 2. The cylinders may be arranged in a V-type or horizontal type.

[0014] The main chamber 10 is a space defined by a cylinder block 11 that forms a cylindrical cylinder 11a extending vertically, a cylinder head 12 that covers the upper end of the cylinder 11a, and a piston 13 that reciprocates within the cylinder 11a. The auxiliary chamber 20 is a space defined by an auxiliary chamber wall 21 provided in the cylinder head 12. The auxiliary chamber 20 has the auxiliary chamber wall 21 and a communication passage 22 (injection port) that connects the main chamber 10 and the auxiliary chamber 20. The spark plug 4 is supported in the center of the cylinder head 12, and its tip side is located within the auxiliary chamber 20, separated by the auxiliary chamber wall 21.

[0015] A pair of intake ports 15 that are opened and closed by intake valves 14 are connected to one side of the cylinder head 12 in the intake / exhaust direction X, and a pair of exhaust ports 17 that are opened and closed via exhaust valves 16 are connected to the other side. A fuel supply nozzle 18 is disposed within the intake port 15. The fuel supply nozzle 18 can supply fuel into the main combustion chamber 10 when the intake valve 14 opens. This configuration can be seen in Figures 1 and 2. The intake port 15 is connected to an intake passage (not shown). The exhaust port 17 is connected to an exhaust passage (not shown).

[0016] The piston 13 has a piston top surface 30 that faces the cylinder head 12 and thereby forms the lower part of the main chamber 10, and a pin hole 13a that is connected to the upper end of the connecting rod 3 via a piston pin 19, and is connected to the crankshaft 2 via the connecting rod 3. This allows the piston 13 to reciprocate between bottom dead center and top dead center in the cylinder 11a in the vertical direction. This configuration can be seen in Figure 1.

[0017] The sub-chamber wall 21 has a circular cross section centered on the cylinder axis (an axis passing through the center of the piston 13 and extending in the cylinder axis direction Z) when viewed from above in the cylinder axis direction Z. This configuration can be seen in Figure 2. The sub-chamber wall 21 has a hemispherical lower portion when viewed in the intake / exhaust direction X and the crankshaft direction Y. This configuration can be seen in Figure 1.

[0018] A plurality of communication passages 22 are formed along the circumferential direction of the sub-chamber wall 21 in a plan view in the cylinder axial direction Z, and connect the main chamber 10 and the sub-chamber 20 to each other.

[0019] The fuel injection nozzle 5 is located outside the auxiliary combustion chamber 20, on the periphery of the cylinder head 12. The fuel injection nozzle 5 is located on the intake valve 14 side in the intake / exhaust direction X, more specifically, between the pair of intake valves 14. This configuration can be seen in FIG. 2 . The fuel injection nozzle 5 injects fuel directly toward the spark plug 4 in the auxiliary combustion chamber 20. A first communication passage 22A, one of the multiple communication passages 22, is located on the ray of fuel injection from the fuel injection nozzle 5, i.e., on an extension of the fuel injection port of the fuel injection nozzle 5. Therefore, fuel injected from the fuel injection nozzle 5 can be directly supplied to the auxiliary combustion chamber 20 via the first communication passage 22A. The extension of the first communication passage 22A also passes below the fuel injection nozzle 5. This configuration can be seen in FIGS. 1 and 5A . The amount of fuel injected by the fuel injection nozzle 5 and the timing of fuel injection are controlled by a control unit (not shown).

[0020] The internal combustion engine 1 described above repeats an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke to reciprocate the piston 13 along the cylinder 11a, thereby outputting power from the crankshaft 2. In the internal combustion engine 1 described above, fuel is supplied into the main combustion chamber 10 from a fuel supply nozzle 18 in the intake port 15 during the intake stroke.

[0021] At this time, intake air introduced into the main combustion chamber 10 from the intake port 15 during the intake stroke is guided by the piston top surface 30, forming a tumble flow, which is a vortex airflow in the vertical direction (rotating around the crankshaft direction Y), within the main combustion chamber 10. In this embodiment, the shape of the piston top surface 30 makes it possible to stably form a tumble flow that does not interfere with fuel injection from the fuel injection nozzle 5 to the spark plug 4 when the piston 13 rises during the compression stroke. The specific shape of the piston top surface 30 will be described later.

[0022] During the compression stroke, while the piston 13 is ascending, fuel is injected from the fuel injection nozzle 5 toward the spark plug 4 in the auxiliary combustion chamber 20 at a predetermined timing, filling the auxiliary combustion chamber 20 with fuel. This configuration can be seen in FIG. 5(A).

[0023] During the compression stroke, the fuel and air-fuel mixture supplied into the auxiliary combustion chamber 20 is ignited by the spark plug 4 and combusted within the auxiliary combustion chamber 20. As a result, a flame F generated within the auxiliary combustion chamber 20 is injected from the communication passage 22 toward the main combustion chamber 10. This configuration can be seen in Figure 7. The flame F injected from the auxiliary combustion chamber 20 toward the main combustion chamber 10 combusts the air-fuel mixture formed within the main combustion chamber 10.

[0024] Next, the specific shape of the piston top surface will be described with reference to Figures 2 to 7. Figure 3 is a perspective view of a piston showing the shape of the piston top surface, Figure 4 is a central cross-sectional view of the piston, Figure 5(A) is a cross-sectional view of a main part of an internal combustion engine showing a state in which the piston has risen to an intermediate point described below during the compression stroke, Figure 5(B) is a cross-sectional view of a main part of an internal combustion engine showing a state in which the piston has risen to top dead center during the compression stroke, Figure 6 is a perspective view of a main part of a piston showing the flow of airflow guided by the piston top surface, and Figure 7 is a plan view of the piston top surface in the cylinder axial direction Z, showing a flame ejected from the sub-chamber.

[0025] In a plan view in the cylinder axial direction Z, the circular piston top surface 30 has an inclined surface 31 and a flat surface 32 that are provided toward the center in the crankshaft direction Y and extend along the intake / exhaust direction X, a pair of lateral guide portions 33, 33 provided on both sides of the inclined surface 31 and the flat surface 32 in the crankshaft direction Y, and a protrusion portion 34 and a valve recess 39 provided on the intake side of the inclined surface 31.

[0026] The inclined surface 31 is formed on the intake port 15 side (intake side) in the intake / exhaust direction X, that is, on the side where the fuel injection nozzle 5 is arranged.

[0027] The inclined surface 31 extends in the intake / exhaust direction X and inclines toward the cylinder head 12 as it approaches the fuel injection nozzle 5. In other words, the inclined surface 31 inclines upward toward the intake side. Specifically, the inclined surface 31 includes a first inclined surface 31a and a second inclined surface 31b that are continuously formed in this order from the exhaust side (the side opposite the fuel injection nozzle 5) along the intake / exhaust direction X. Of the first inclined surface 31a and the second inclined surface 31b, the second inclined surface 31b, which is located on the intake side, has a shorter length in the intake / exhaust direction X and a steeper angle of upward inclination toward the cylinder head 12. This configuration can be seen in FIG. 4 . In the example shown in Figure 4, the inclined surface 31 is formed by the first inclined surface 31a and the second inclined surface 31b having different angles, but the inclined surface 31 may have an inclination angle such that the angle of the upward inclination becomes steeper in multiple stages as it approaches the intake side (the fuel injection nozzle 5 side), and the inclined surface 31 may be formed by three or more inclined surfaces having different angles.

[0028] The angle of the top of the inclined surface 31 (in this embodiment, the angle of the second inclined surface 31b) is set so that, when the vertical position of the piston 13 is within a predetermined range, the position where an extension of the second inclined surface 31b parallel to the intake / exhaust direction X (hereinafter simply referred to as the extension of the inclined surface 31) intersects with the wall surface of the cylinder 11a is lower (closer to the piston) in the cylinder axial direction Z than the fuel injection nozzle 5. In this case, the intersection of the extension of the inclined surface 31 and the wall surface of the cylinder 11a is defined as a first contact point H1. For details of this configuration, see FIG. 4. Specifically, the inclined surface 31 is formed so that, when the piston 13 is located closer to the bottom dead center than the midpoint between the top dead center and the bottom dead center, the extension of the inclined surface 31 intersects with the wall surface of the cylinder 11a at the first contact point H1. For details of this configuration, see FIG. 5A. On the other hand, the inclined surface 31 is formed so that, when the piston 13 is at top dead center, an extension of the inclined surface 31 passes between the fuel injection nozzle 5 and the spark plug 4 and intersects with the lower surface of the cylinder head 12. This configuration can be seen in FIG. 5(B).

[0029] 5A, the inclined surface 31 is preferably formed so that an extension of the inclined surface 31 intersects with the wall surface of the cylinder 11a at the first contact point H1 when fuel is injected from the fuel injection nozzle 5. In this case, the higher the engine speed, the closer the vertical position of the piston 13 is to the bottom dead center when fuel is injected from the fuel injection nozzle 5. For this reason, it is preferable to set the inclined surface 31 so that an extension of the inclined surface 31 intersects with the wall surface of the cylinder 11a when fuel is injected when the engine speed is high, around 5,000 rpm.

[0030] Furthermore, the inclined surface 31 is formed so that when the piston 13 reaches top dead center, its top is located below the center line extending from the injection port 22a of the first communication passage 22A of the auxiliary combustion chamber 20, as viewed in the crankshaft direction Y. This configuration can be seen in Figure 5(B) . This configuration prevents the inclined surface 31 from being directly hit by the flame F ejected from the auxiliary combustion chamber 20 toward the main combustion chamber 10, and thereby preventing deterioration of the inclined surface 31.

[0031] Further, on the intake side of the inclined surface 31, a downwardly sloping surface 36 is formed, which slopes downward as it approaches the intake side. The downwardly sloping surface 36 is connected to the top of the inclined surface 31.

[0032] The flat surface 32 extends from the exhaust-side end of the piston top surface 30 toward the intake side in the intake / exhaust direction X and is continuous with the inclined surface 31. In this embodiment, the flat surface 32 is formed as a plane extending parallel to the intake / exhaust direction X and the crankshaft direction Y so as to be perpendicular to the cylinder axial direction Z. This configuration can be seen in FIG. 4 . The flat surface 32 may be any smooth surface capable of guiding the airflow toward the inclined surface, and is not limited to a plane perpendicular to the cylinder axial direction Z. For example, the flat surface 32 may be a gently inclined surface forming an angle with the inclined surface 31. When the flat surface 32 is inclined in the same direction as the inclined surface 31, the inclined surface 31 is defined as the portion on the intake side of the center of the piston 13. By forming the flat surface 32 on the exhaust side of the inclined surface 31, the airflow flowing along the piston top surface 30 can be prevented from separating from the piston top surface 30 on the exhaust side of the inclined surface 31.

[0033] The lateral guide portion 33 has a lateral guide surface 33a that slopes from the exhaust-side end toward the cylinder head 12, a lateral extension surface 33b that extends from the intake-side end of the lateral guide surface 33a substantially parallel to the piston top surface 30, and a lateral downward-sloping surface 33c that slopes downward from the intake-side end of the lateral extension surface 33b toward the piston top surface 30. That is, as viewed in the crankshaft direction Y, the lateral guide portion 33 protrudes toward the cylinder head 12 in the cylinder axis direction Z and extends along the intake / exhaust direction X, forming a substantially mountain-like shape with the intake-side end of the lateral guide surface 33a as its apex. For this configuration, see FIG. 4 . The lateral extension surface 33b of the lateral guide portion 33 may be sloped in the same manner as the lateral downward-sloping surface 33c. In this case, the lateral extension surface 33b and the lateral downward-sloping surface 33c are located in the same location.

[0034] The angle of the lateral guide surface 33a is set so that, when the vertical position of the piston 13 is within a predetermined range, the position where an extension of the lateral guide surface 33a parallel to the intake / exhaust direction X (hereinafter simply referred to as the extension of the lateral guide surface 33a) intersects with the wall surface of the cylinder 11a is lower (closer to the piston) in the cylinder axial direction Z than the first contact point H1. In this case, the intersection point of the extension of the lateral guide surface 33a and the wall surface of the cylinder 11a is defined as the second contact point H2. The lateral guide surface 33a is formed with a gentler inclination than the inclined surface 31. This is because the top of the lateral guide surface 33a is positioned closer to the wall surface of the cylinder 11a in the intake / exhaust direction X than the top of the inclined surface 31. By forming the lateral guide surface 33a with a gentler inclination than the inclined surface 31, the second contact point H2 is located lower in the cylinder axial direction Z than the first contact point H1, and is closer to the exhaust side in the intake / exhaust direction X. 6, the side guide surface 33a is formed so that, when an extension line of the side guide surface 33a is extended along the inner wall of the cylinder 11a toward the intake side in the intake / exhaust direction X while maintaining the vertical angle from the second contact point H2, the extension line reaches a third contact point H3 below the first contact point H1 below the fuel injection nozzle 5 (a position overlapping with the fuel injection nozzle 5 as viewed in the cylinder axial direction Z). This configuration can be seen in FIGS. 4 and 6.

[0035] The lateral downward surface 33c slopes downward from the lateral extension surface 33b toward the intake side and smoothly connects to the downward surface 36 located on the intake side of the inclined surface 31. That is, the lateral downward surface 33c and the downward surface 36 are flush with each other. This configuration can prevent turbulence on the intake side of the piston top surface 30 of the airflow that flows in the intake / exhaust direction X along the inclined surface 31 and the flat surface 32, including the airflow that does not separate from the inclined surface 31 and the airflow that does not separate from the lateral guide surface 33a. For this configuration, refer to Figures 2 and 6.

[0036] As described above, the first separation angle α formed between the extension line of the inclined surface 31 and the downward surface 36 is set larger than the second separation angle β formed between the extension line of the lateral guide surface 33a and the lateral extension surface 33b. With this configuration, the airflow guided by the inclined surface 31, where the flow is strongest, is more likely to separate from the top of the inclined surface 31, thereby making the tumble flow guided by the piston top surface 30 more stable. For this configuration, see FIG. 4. Note that even when the lateral extension surface 33b is inclined, it is preferable that the first separation angle α be larger than the second separation angle β.

[0037] The guide width, which is the width of the inclined surface 31 and the flat surface 32 in the crankshaft direction Y, is gradually narrowed toward the intake side in the intake / exhaust direction X. Specifically, the inner surfaces of the side guide portions 33 (surfaces facing the cylinder axis) are inclined in the crankshaft direction Y so as to approach each other toward the intake side. The outer surfaces of the side guide portions 33 (surfaces facing the wall surface of the cylinder 11a) are formed in an arc shape along the wall surface of the cylinder 11a in the intake / exhaust direction X. The side guide portions 33 extend from the exhaust side to the intake side of the cylinder axis in the intake / exhaust direction X. Therefore, the width of each side guide portion 33 in the crankshaft direction Y is greatest at a point located at the center of the piston 13 in the intake / exhaust direction X. The inclination angle of the inner surfaces of the side guide portions 33 is determined so that the width of each side guide portion 33 in the crankshaft direction Y on the intake side of the point located at the center of the piston 13 in the intake / exhaust direction X is approximately constant.

[0038] The protrusion 34 is a protrusion formed on the downward surface 36 facing upward. The protrusion 34 is formed so that its width in the crankshaft direction Y decreases toward the exhaust side in the intake / exhaust direction X. The width of the intake-side end of the protrusion 34 in the crankshaft direction Y is greater than the width of the tip of the fuel injection nozzle 5 in the crankshaft direction Y. This configuration can be seen in FIG. 2 . In this embodiment, the protrusion 34 is located between the pair of intake valves 14. Specifically, the protrusion 34 is formed by utilizing a trapezoidal portion, as viewed from the cylinder axis direction Z, between a pair of recesses corresponding to the intake valves 14 of a valve recess 39, which is a recess formed to match the shape of the pair of intake valves 14. In other words, the valve recess 39 is formed flush with the downward surface 36 and the lateral downward surface 33c, and the protrusion 34 protrudes upward from the downward surface 36. The protrusion 34 may have a surface in the crankshaft direction Y that slopes upward as it approaches the center of the protrusion 34 when viewed in the intake / exhaust direction X. This configuration can be seen in FIG. 9A. This configuration allows the airflow flowing along the downward surface 36 and the side downward surface 33c to be guided upward. The shape of the protrusion 34 may be a diamond shape or other shape in addition to a trapezoidal shape when viewed in the cylinder axial direction Z as shown in FIG. 2. That is, it is sufficient that the width of the exhaust-side end of the protrusion 34 in the crankshaft direction Y decreases as it approaches the exhaust side. This configuration can be seen in FIG. 9B.

[0039] (Operation and Effect) Next, the operation and effect of the shape of the piston top surface 30 will be described. As shown in Figure 5(A), when the piston 13 is located closer to bottom dead center than the midpoint of the cylinder 11a during the compression stroke of the internal combustion engine 1, the inclined surface 31 described above can guide the airflow flowing over the piston top surface 30 toward the fuel injection nozzle 5 so that it contacts the intake-side wall surface of the cylinder 11a at a first contact point H1 below the fuel injection nozzle 5. This causes a tumble flow generated in the main combustion chamber 10 to flow the fuel injected from the fuel injection nozzle 5 toward the spark plug 4 toward the cylinder head 12, preventing the injection position from shifting upward.

[0040] Furthermore, by gradually narrowing the guide width of the inclined surface 31 toward the fuel injection nozzle 5, the flow velocity of the airflow on the fuel injection nozzle 5 side of the inclined surface 31 increases, making the tumble flow more stable. Furthermore, by gradually increasing the inclination angle of the inclined surface 31 toward the fuel injection nozzle 5, the airflow guided by the inclined surface 31 is more likely to separate smoothly at the end of the inclined surface 31. This makes the tumble flow formed by the inclined surface 31 more stable.

[0041] According to the above-mentioned flat surface 32, the downstream side of the airflow flowing along the piston top surface 30 is made flat, so that the airflow flowing toward the inclined surface 31 can be prevented from separating from the piston top surface 30, thereby making the tumble flow more stable.

[0042] As shown in FIG. 6 , the above-described lateral guide portion 33 can guide the airflow flowing along the outer edge of the piston top surface 30 toward the fuel injection nozzle 5 to a second contact point H2 below the first contact point H1. This prevents the airflow guided by the lateral guide portion 33 from disrupting the airflow guided by the inclined surface 31. This further stabilizes the tumble flow formed in the main combustion chamber 10 by the piston top surface 30. Furthermore, the lateral guide portion 33 is formed so that when the extension line of the lateral guide surface 33a is extended toward the fuel injection nozzle 5 along the inner wall of the cylinder 11a while maintaining the vertical angle from the second contact point H2, it reaches the third contact point H3 below the first contact point H1. Therefore, the airflow guided by the lateral guide portion 33 can push up the airflow guided by the inclined surface 31, further stabilizing the tumble flow. Moreover, since the side guide portion 33 is formed so that the side downward surface 33c and the downward surface 36 are flush with each other, the airflow flowing along the side downward surface 33c and the downward surface 36 can be prevented from being turbulent without peeling off from the side guide surface 33a and the inclined surface 31, and the tumble flow can be made more stable. Furthermore, by making the width of the side guide portion 33 from its widest point in the crankshaft direction Y to the fuel injection nozzle 5 side approximately constant, the airflow flowing along the side guide portion 33 can be prevented from being turbulent in the crankshaft direction Y, and the tumble flow can be made more stable.

[0043] 7 , in a plan view in the cylinder axial direction Z, the above-described protrusion 34 allows the flame F1, which is part of the flame F injected from the auxiliary combustion chamber 20 toward the main combustion chamber 10 and is injected from the first communication passage 22A toward the fuel injection nozzle 5, to be divided in the crankshaft direction Y and deflected away from the fuel injection nozzle 5. This reduces the effect of the flame F1 injected from the first communication passage 22A on the fuel injection nozzle 5.

[0044] Another embodiment Next, the configuration of the grooves provided in the side guide portions 33 will be described with reference to Fig. 8. Fig. 8 is a perspective view of the top surface of the piston showing the grooves provided in the side guide portions 33. In this manner, the side guide portions 33 may be configured to extend in a direction intersecting the extending direction of the side guide portions 33 and to have grooves 35 provided as passages connecting the inside and outside of the side guide portions 33.

[0045] The grooves 35 are recessed in the cylinder axial direction Z, extend in a direction intersecting the extension direction of the side guide portions 33, i.e., in the crankshaft direction Y, and are open on the inner and outer surfaces of the side guide portions 33. The depth of the grooves 35 in the up-down direction (cylinder axial direction Z) gradually increases from the outer side (toward the center of the piston 13) in the extension direction of the grooves 35 toward the inner side. The width of the grooves 35 in the extension direction of the side guide portions 33 (intake / exhaust direction X) gradually increases from the inner side toward the outer side in the extension direction of the grooves 35.

[0046] With the groove 35 configured as described above, by providing a pair of side guide portions 33 on the edge of the piston top surface 30, the flame F injected from the auxiliary combustion chamber 20 can be efficiently propagated through the gap formed between the outer sides of the side guide portions 33 in the width direction (crankshaft direction Y) and the wall surface of the cylinder 11a. Therefore, the side guide portions 33 provided on the piston top surface 30 can prevent the spread of combustion of the mixture outside the side guide portions 33 from being hindered. Furthermore, the vertical depth of the groove 35 increases toward the inside in the extension direction of the groove 35, which facilitates the flame F injected from the auxiliary combustion chamber 20 to be guided to the groove 35. Furthermore, the width of the groove 35 increases from the inside toward the outside in the extension direction of the groove 35, which facilitates the propagation of the flame F over a wider area outside the width direction of the side guide portions 33. This facilitates the combustion of the mixture outside the side guide portions 33.

[0047] Note that the grooves 35 are grooves for guiding the flame F injected from the nozzles 22a of the auxiliary chamber 20 from the inside to the outside of the side guide portion 33, and are therefore not limited to the position shown in Figure 8. Specifically, the grooves 35 only need to be provided at positions where extensions from the nozzles 22a of the auxiliary chamber 20 intersect with the side guide portion 33 in a plan view in the cylinder axial direction Z, and extend along the extensions from the nozzles 22a. A configuration in which multiple grooves 35 are provided is also possible. However, the grooves 35 should not be provided at positions adjacent to the tops of the inclined surfaces 31 of the side guide portions 33. This prevents the grooves 35 from disrupting the flow of the airflow guided along the inclined surfaces 31.

[0048] The side guide portions 33 may be configured such that the width in the crankshaft direction Y on the exhaust side of the groove portions 35 is larger than the width in the crankshaft direction Y on the intake side of the groove portions 35. This makes it possible to suppress turbulence in the airflow caused by the airflow along the side guide portions 33 passing through the groove portions 35.

[0049] The grooves 35 are not limited to grooves recessed into the upper surfaces of the side guide portions 33, but may be through-holes drilled in a direction intersecting the direction in which the side guide portions 33 extend.

[0050] It should be noted that this embodiment shows only one example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention. For example, the features of the present invention are not limited to an internal combustion engine 1 using an auxiliary combustion chamber 20 that houses an ignition plug 4 within a main combustion chamber 10, and similar effects can be expected in any internal combustion engine that is provided with a fuel injection nozzle 5 that injects fuel toward the ignition plug 4. Furthermore, although the internal combustion engine of the present disclosure uses gasoline, the present invention is not limited to this, and other fuels such as alcohol may also be used.

[0051] As described above, the present specification discloses the following: (1) A cylinder injection type internal combustion engine comprising: a cylinder formed by a cylinder block; a cylinder head covering one end of the cylinder; a piston having a top surface facing the cylinder head and reciprocating within the cylinder; an ignition plug arranged in the center of the cylinder head within a combustion chamber formed between the cylinder, the cylinder head, and the piston; a fuel injection nozzle arranged within the combustion chamber; and an intake port and an exhaust port provided in the cylinder head on either side of the spark plug, wherein the fuel injection nozzle is arranged on one side of the intake and exhaust direction connecting the intake port and the exhaust port, and injects fuel toward the spark plug, and the top surface of the piston is formed with an inclined surface that extends along the intake and exhaust direction and inclined toward the cylinder head as it approaches the one side, and a pair of side guide portions that are arranged to sandwich the inclined surface in the crankshaft direction that is perpendicular to the intake and exhaust direction and the cylinder axial direction that is the reciprocating direction of the cylinder, and the width of the inclined surface in the crankshaft direction is formed to narrow as it approaches the one side. According to this configuration, the airflow guided by the inclined surface 31 gradually converges toward the top of the inclined surface 31, so that the tumble flow formed by the inclined surface 31 becomes more stable.

[0052] (2) The direct injection internal combustion engine according to (1), wherein the inclined surface is formed so that the angle of inclination toward the cylinder head increases stepwise toward the one side. With this configuration, the airflow guided by the inclined surface 31 is more likely to separate from the top of the inclined surface 31. Furthermore, compared to when the angle of the inclined surface 31 is made steep from the beginning, the inclined surface 31 can be prevented from acting as a resistance to the airflow.

[0053] (3) The direct injection internal combustion engine according to (1) or (2), wherein the lateral guide portion has a lateral guide surface that slopes toward the cylinder head as it approaches the one side, and the top surface is formed with a downward surface that slopes toward the cylinder head as it approaches the one side from the top of the slant surface, and a lateral extension surface that extends from the top of the lateral guide surface to the one side, and the slant surface is formed such that an angle formed between an extension line of the slant surface and the downward surface is larger than an angle formed between an extension line of the lateral guide surface and the lateral extension surface. With this configuration, the airflow separating from the main slant surface separates more easily than the airflow separating from the lateral guide surface 33 a, thereby making the tumble flow formed on the piston top surface 30 more stable.

[0054] (4) The direct injection internal combustion engine according to any one of (1) to (3), wherein the width of the side guide portion in the crankshaft direction is widest at a portion corresponding to a center of the piston in the intake / exhaust direction and is formed so as to be substantially constant on the one side from the widest portion. With this configuration, the airflow flowing over the side guide portion 33 is less likely to be disturbed.

[0055] (5) A direct-injection internal combustion engine according to any one of (1) to (4), wherein an auxiliary chamber is provided in the combustion chamber to accommodate the spark plug, the auxiliary chamber is formed with an injection port that connects the combustion chamber and the auxiliary chamber and injects flame from the auxiliary chamber into the combustion chamber, the side guide portion is formed with a passage portion that extends in the crankshaft direction and connects the inner surface and outer surface of the side guide portion, the passage portion being formed on an extension of the injection port. With this configuration, the flame injected from the auxiliary chamber can be efficiently guided into the gap between the side guide portion 33 and the wall surface of the cylinder 11a, thereby achieving both the formation of a stable tumble flow and combustion efficiency.

[0056] REFERENCE SIGNS LIST 1 internal combustion engine 2 crankshaft 3 connecting rod 4 spark plug 5 fuel injection nozzle 10 main chamber 11a cylinder 11 cylinder block 12 cylinder head 13a pin hole 13 piston 14 intake valve 15 intake port 16 exhaust valve 17 exhaust port 18 fuel supply nozzle 19 piston pin 20 auxiliary chamber 21 auxiliary chamber wall 22A first communication passage (injection port) 22 communication passage (injection port) 30 piston top surface 31a first inclined surface 31b second inclined surface 31 inclined surface 32 flat surface 33a lateral guide surface 33b lateral extension surface 33c lateral downward surface 33 lateral guide portion 34, 41 protruding portion 35 groove portion 36 downward surface 39 valve recess H1 first contact point H2 Second contact point H H3 Third contact point H

Claims

1. a cylinder formed by a cylinder block; a cylinder head covering one end of the cylinder; a piston having a top surface facing the cylinder head and reciprocating within the cylinder; a spark plug disposed in a center portion of the cylinder head in a combustion chamber formed between the cylinder, the cylinder head, and the piston; a fuel injection nozzle disposed within the combustion chamber; an intake port and an exhaust port provided in the cylinder head on either side of the spark plug; A direct injection internal combustion engine comprising: the fuel injection nozzle is disposed on one side in an intake / exhaust direction connecting the intake port and the exhaust port, and injects fuel toward the spark plug; the top surface of the piston is formed with an inclined surface that extends along the intake / exhaust direction and inclines toward the cylinder head as it approaches the one side, and a pair of side guide portions that are arranged to sandwich the inclined surface in a crankshaft direction that is perpendicular to the intake / exhaust direction and a cylinder axial direction that is a reciprocating direction of the cylinder, a width of the inclined surfaces in the crankshaft direction is formed to be narrower toward the one side by inclining with respect to the crankshaft direction such that inner sides of the side guide portions approach each other toward the one side, an apex of the one end of the inclined surface extends in the crankshaft direction; Direct injection internal combustion engine.

2. The inclined surface is formed so that the inclination angle toward the cylinder head side increases stepwise toward the one side.

2. The direct injection internal combustion engine according to claim 1.

3. the side guide portion has a side guide surface that slopes toward the cylinder head as it approaches the one side, The top surface is formed with a downward surface that slopes toward the cylinder head from the top of the inclined surface toward the one side, and a lateral extension surface that extends from the top of the side guide surface to the one side, The inclined surface is formed so that an angle formed between an extension line of the inclined surface and the downward surface is larger than an angle formed between an extension line of the side guide surface and the side extension surface, The position where an extension line of the side guide surface intersects with the wall surface of the cylinder is closer to the piston than the position where an extension line of the inclined surface intersects with the wall surface of the cylinder.

2. The direct injection internal combustion engine according to claim 1.

4. The width of the side guide portion in the crankshaft direction is widest at a portion corresponding to a center of the piston in the intake / exhaust direction, and is formed to be substantially constant on the one side from the widest portion.

2. The direct injection internal combustion engine according to claim 1.

5. a sub-chamber for accommodating the spark plug is provided within the combustion chamber; The auxiliary chamber is formed with an injection port that communicates the combustion chamber with the auxiliary chamber and injects flames from the auxiliary chamber into the combustion chamber, a passage portion extending in the crankshaft direction and communicating with an inner surface and an outer surface of the side guide portion is formed in the side guide portion; The passage portion is formed on an extension line of the injection port.

5. A direct injection internal combustion engine according to claim 1.