engine

Abstract

To strengthen a tumble flow in a combustion chamber.SOLUTION: An engine of one embodiment, being an engine having a cylinder main body has a cylinder head which is attached to the cylinder head, and in which an intake port and an exhaust port are formed, and a piston accommodated in a cylinder bore of the cylinder main body, and defining a combustion chamber between the cylinder head and itself. The piston comprises a first piston inclination face which is formed at an external peripheral edge part of a piston crown face, and inclines while approaching the cylinder head as approaching an outer edge of the piston crown face. The piston comprises a second inclination face which is formed at the external peripheral edge part of the piston crown face, and inclines while separating from the cylinder head as approaching the outer edge of the piston crown face.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to an engine. [Background technology]

[0002] In order to improve the thermal efficiency of an engine, it is important to generate a vertical vortex tumble flow within the combustion chamber. Also, a squish clearance is often provided between the piston and the cylinder head to generate a squish flow that flows from the outer edge of the combustion chamber toward the center (see Patent Documents 1 to 3). In this way, by strengthening the flow of the air-fuel mixture within the combustion chamber, the combustion speed can be increased, improving combustion efficiency and the thermal efficiency of the engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-190166 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-152825 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-19596 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, further improvements in engine thermal efficiency are being demanded, and further strengthening of the tumble flow in the combustion chamber is also being demanded.

[0005] An object of the present invention is to enhance the tumble flow within the combustion chamber. [Means for solving the problem]

[0006] An engine according to one embodiment is an engine including a cylinder body, the engine including a cylinder head attached to the cylinder body and having an intake port and an exhaust port formed therein, and a piston housed in a cylinder bore of the cylinder body and defining a combustion chamber between the piston and the cylinder head. do. The piston includes a first inclined surface formed on an outer peripheral edge of a piston crown surface, the first inclined surface inclining toward the cylinder head as it approaches the outer edge of the piston crown surface, and a second inclined surface formed on the outer peripheral edge of the piston crown surface, the second inclined surface inclining away from the cylinder head as it approaches the outer edge of the piston crown surface. The first piston inclined surface is formed at a position point-symmetrical to the second piston inclined surface with respect to the center of the piston. [Effects of the Invention]

[0007] According to one aspect of the present invention, the piston includes a first inclined piston surface that is inclined closer to the cylinder head as it approaches the outer edge of the piston crown surface, and a second inclined piston surface that is inclined away from the cylinder head as it approaches the outer edge of the piston crown surface, thereby enhancing the tumble flow in the combustion chamber. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing an example of a vehicle equipped with an engine according to an embodiment of the present invention; [Figure 2] 1 is a diagram showing an engine according to an embodiment of the present invention; [Figure 3] FIG. 1 is a simplified diagram showing a combustion chamber of an engine and its vicinity. [Figure 4] 4 is a view showing the piston as viewed from the direction of arrow α in FIG. 3. FIG. [Figure 5] FIG. [Figure 6] FIG. 4 is a view showing the cylinder head as seen from the direction of arrow β in FIG. 3. [Figure 7] FIG. 2 is a cross-sectional view showing a cylinder head. [Figure 8] FIG. 2 is a cross-sectional view showing a cylinder head and a piston. [Figure 9]FIG. 2 is a diagram showing the flow direction of intake air in a combustion chamber. [Figure 10] FIG. 2 is a diagram showing the flow direction of intake air in a combustion chamber. [Figure 11] FIG. 4 is a cross-sectional view showing an engine according to another embodiment of the present invention. [Figure 12] FIG. 4 is a cross-sectional view showing an engine according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. In the following description, identical or substantially identical configurations and elements are designated by the same reference numerals and will not be described repeatedly.

[0010] [vehicle] FIG. 1 is a diagram showing an example of a vehicle 11 equipped with an engine 10 according to an embodiment of the present invention. As shown in FIG. 1, the vehicle 11 is equipped with a powertrain 12 including the engine 10. Wheels 16 are connected to an output shaft 13 of the powertrain 12 via a propeller shaft 14 and a differential mechanism 15. The illustrated powertrain 12 is a rear-wheel drive powertrain, but is not limited thereto and may be a front-wheel drive or all-wheel drive powertrain. Furthermore, as will be described later, the illustrated engine 10 is a horizontally opposed engine, but is not limited thereto and may be, for example, an in-line engine, a V-type engine, or a single-cylinder engine.

[0011] [engine] FIG. 2 is a diagram showing an engine 10 according to one embodiment of the present invention. As shown in FIG. 2, the engine 10 includes a cylinder block (cylinder body) 20 constituting one cylinder bank, a cylinder block (cylinder body) 21 constituting the other cylinder bank, and a crankshaft 22 supported by the pair of cylinder blocks 20, 21. A cylinder head 24 equipped with a valve train 23 and other components is attached to each of the cylinder blocks 20, 21. Each of the cylinder heads 24 is formed with an intake port 26 communicating with a combustion chamber 25, and is fitted with an intake valve 27 that opens and closes the intake port 26. The cylinder head 24 is also formed with an exhaust port 28 communicating with the combustion chamber 25, and is fitted with an exhaust valve 29 that opens and closes the exhaust port 28. The cylinder head 24 is provided with a spark plug (not shown) that ignites the air-fuel mixture in the combustion chamber 25, and is also provided with an injector (not shown) that injects fuel toward the intake air.

[0012] Each cylinder block 20, 21 is formed with a cylinder bore 30, and each cylinder bore 30 houses a piston 31. A piston pin 32 is attached to the piston 31, and a small end 34 of a connecting rod 33 is connected to the piston pin 32. The crankshaft 22 is provided with a crank pin 36 that is eccentric with respect to a crank journal 35, and a big end 37 of the connecting rod 33 is connected to the crank pin 36. In this way, the crankshaft 22 and the piston 31 are connected to each other via the connecting rod 33.

[0013] [piston] FIG. 3 is a simplified diagram showing the combustion chamber 25 of the engine 10 and its vicinity. FIG. 4 is a diagram showing the piston 31 from the direction of arrow α in FIG. 3, and FIG. 5 is a cross-sectional view of the piston 31. FIG. 5 shows a cross-sectional view of the piston 31 taken along line A1-A1 in FIG. 4, and a cross-sectional view of the piston 31 taken along line A2-A2 in FIG. 4. In the following description, the piston center C1a is the center of the piston crown surface 40 through which the center line C2a of the piston 31 passes. The center line C2a of the piston 31 coincides with the center line C3 of the cylinder bore 30.

[0014] As shown in FIG. 3 , the cylinder bore 30, the piston 31, and the cylinder head 24 define a combustion chamber 25. That is, the combustion chamber 25, in which an air-fuel mixture is combusted, is defined between the cylinder head 24 and the piston 31. As shown in FIGS. 4 and 5 , the piston 31 has a head portion 41 with a piston crown surface 40 facing the combustion chamber 25 and a land portion 43 to which a piston ring 42 is attached. The piston 31 also has a pin boss portion 45 with a pin hole 44 into which the piston pin 32 is inserted and a skirt portion 46 that slidably contacts the inner circumferential surface of the cylinder bore 30. Note that the piston crown surface 40 shown in the figure is formed in a concave shape, but is not limited thereto. For example, the piston crown surface 40 may be formed in a convex shape, or the piston crown surface 40 may be formed using a plane perpendicular to the center line C2a of the piston 31.

[0015] A first piston inclined surface 51 is formed on an annular outer peripheral edge 50 constituting a part of the piston crown surface 40, and is positioned closer to the exhaust port 28 than the piston center C1a. The first piston inclined surface 51 is an inclined surface that inclines toward the cylinder head 24 as it approaches the outer edge 40o of the piston crown surface 40. A second piston inclined surface 52 is formed on the outer peripheral edge 50 of the piston crown surface 40, and is positioned closer to the intake port 26 than the piston center C1a. The second piston inclined surface 52 is an inclined surface that inclines away from the cylinder head 24 as it approaches the outer edge 40o of the piston crown surface 40. The first and second piston inclined surfaces 51, 52 are inclined surfaces inclined with respect to the center line C3 of the cylinder bore 30. The first and second piston inclined surfaces 51, 52 are inclined surfaces inclined with respect to an imaginary plane perpendicular to the center line C3 of the cylinder bore 30.

[0016] [Cylinder head] Fig. 6 is a view showing the cylinder head 24 from the direction of arrow β in Fig. 3, and Fig. 7 is a cross-sectional view showing the cylinder head 24. Fig. 7 shows a cross-sectional view of the cylinder head 24 taken along line B1-B1 in Fig. 6, and a cross-sectional view of the cylinder head 24 taken along line B2-B2 in Fig. 6. In the following description, the combustion chamber center C1b is the center of the combustion chamber surface 59 through which the center line C2b of the combustion chamber 25 passes. The center line C2b of the combustion chamber 25 coincides with the center line C3 of the cylinder bore 30.

[0017] As shown in FIG. 3 , the cylinder head 24 is formed with a combustion chamber surface 59 facing the combustion chamber 25, i.e., the combustion chamber surface 59 opposing the piston crown surface 40. As shown in FIGS. 6 and 7 , an annular outer peripheral edge 60 constituting a part of the combustion chamber surface 59 is formed with a first head inclined surface 61 positioned closer to the exhaust port 28 than the combustion chamber center C1b. That is, the outer peripheral edge 60 of the combustion chamber surface 59 is formed with the first head inclined surface 61 opposing the first piston inclined surface 51. This first head inclined surface 61 is an inclined surface that inclines away from the piston crown surface 40 as it approaches the outer edge 25o of the combustion chamber 25, i.e., the outer edge 59o of the combustion chamber surface 59. In addition, the outer peripheral edge 60 of the combustion chamber surface 59 is formed with a second head inclined surface 62 positioned closer to the intake port 26 than the combustion chamber center C1b. That is, the outer peripheral edge 60 of the combustion chamber surface 59 is formed with the second head inclined surface 62 opposing the second piston inclined surface 52. The second head inclined surface 62 is an inclined surface that inclines toward the piston crown surface 40 as it approaches the outer edge 25o of the combustion chamber 25, i.e., the outer edge 59o of the combustion chamber surface 59. The first and second head inclined surfaces 61, 62 are inclined surfaces that are inclined with respect to the center line C3 of the cylinder bore 30. The first and second head inclined surfaces 61, 62 are also inclined surfaces that are inclined with respect to an imaginary plane that is perpendicular to the center line C3 of the cylinder bore 30.

[0018] [Squish Area] Next, squish areas S1 and S2 defined between the cylinder head 24 and the piston 31 will be described. That is, squish area S1 defined between the first head inclined surface 61 and the first piston inclined surface 51, and squish area S2 defined between the second head inclined surface 62 and the second piston inclined surface 52 will be described. FIG. 8 is a cross-sectional view showing the cylinder head 24 and the piston 31. FIG. 8 shows a cross-sectional view of the cylinder head 24 taken along line B3-B3 in FIG. 6 and a cross-sectional view of the piston 31 taken along line A3-A3 in FIG. 4. FIGS. 9 and 10 also show the flow direction of intake air within the combustion chamber 25. For convenience, in FIGS. 9 and 10, the reciprocating direction of the piston 31 is defined as the up-down direction. In the following description, the cylinder head 24 side will be referred to as the upper side, and the piston 31 side will be referred to as the lower side.

[0019] As shown in FIGS. 3 and 8 , the cylinder head 24 is formed with first and second head inclined surfaces 61, 62, and the piston 31 is formed with first and second piston inclined surfaces 51, 52. The first head inclined surface 61 and the first piston inclined surface 51 face each other, and the second head inclined surface 62 and the second piston inclined surface 52 face each other. The first piston inclined surface 51 and the second piston inclined surface 52 face each other across the center line C3 of the cylinder bore 30, and the first head inclined surface 61 and the second piston inclined surface 62 face each other across the center line C3 of the cylinder bore 30. That is, in FIG. 4 , the positions where the first piston inclined surface 51 and the second piston inclined surface 52 are formed are point-symmetrical with respect to the piston center C1a. In addition, in FIG. 6 , the positions where the first head inclined surface 61 and the second piston inclined surface 62 are formed are point-symmetrical with respect to the combustion chamber center C1b.

[0020] In other words, the positions where the first piston inclined surface 51, the second piston inclined surface 52, the first head inclined surface 61, and the second head inclined surface 62 are formed can be defined as follows. That is, as shown in FIGS. 4 and 6 , a virtual plane that includes the center line C3 of the cylinder bore 30 and is perpendicular to the center line C4 of the piston pin 32 is set as a reference plane PL1. In this case, the first piston inclined surface 51, the second piston inclined surface 52, the first head inclined surface 61, and the second head inclined surface 62 are formed at positions that intersect with the reference plane PL1. The center line C4 of the piston pin 32 coincides with the center line of the pin hole 44 formed in the pin boss portion 45. As described above, by forming the piston inclined surfaces 51, 52 and the head inclined surfaces 61, 62, the tumble flow Ft can be strengthened by the jet flows Fs1, Fs2 from the squish areas S1, S2, as shown in FIG. 10 .

[0021] That is, as shown by arrows Fa in Figure 9, from the intake stroke to the compression stroke of the engine 10, much of the intake air flows into the gap G between the intake port 26 and the intake valve 27, generating a tumble flow Ft, which is a vertical vortex air flow, within the cylinder bore 30. Then, as shown in Figure 10, when the piston 31 reaches near top dead center at the end of the compression stroke, an injection flow Fs1 toward the intake port 26 is injected obliquely downward from the squish area S1 defined between the first head inclined surface 61 and the first piston inclined surface 51. Similarly, when the piston 31 reaches near top dead center at the end of the compression stroke, an injection flow Fs2 toward the exhaust port 28 is injected obliquely upward from the squish area S2 defined between the second head inclined surface 62 and the second piston inclined surface 52.

[0022] At this time, within the combustion chamber 25, a flow Ft1 directed toward the intake port 26 is formed in the lower part of the combustion chamber 25, and a flow Ft2 directed toward the exhaust port 28 is formed in the upper part of the combustion chamber 25 as the tumble flow Ft. In other words, the injection flow Fs1 directed obliquely downward from the squish area S1 can strengthen the flow component Ft1 of the tumble flow Ft directed toward the intake port 26. Furthermore, the injection flow Fs2 directed obliquely upward from the squish area S2 can strengthen the flow component Ft2 of the tumble flow Ft directed toward the exhaust port 28. This makes it possible to generate a strong tumble flow Ft in the combustion chamber 25 at the end of the compression stroke, thereby increasing the combustion efficiency of the air-fuel mixture and improving the thermal efficiency of the engine 10.

[0023] [Other embodiments] In the above description, the first piston inclined surface 51 is located closer to the exhaust port 28 than the piston center C1a, and the second piston inclined surface 52 is located closer to the intake port 26 than the piston center C1a. However, this is not limited to this. That is, the first piston inclined surface 51 may be located closer to the intake port 26 than the piston center C1a, and the second piston inclined surface 52 may be located closer to the exhaust port 28 than the piston center C1a. Here, FIGS. 11 and 12 are cross-sectional views of an engine 70 according to another embodiment of the present invention. FIGS. 11 and 12 show the same cross section as FIG. 3 and the flow direction of intake air within the combustion chamber 25. In FIGS. 11 and 12, parts and portions similar to those shown in FIGS. 9 and 10 are designated by the same reference numerals, and their description will be omitted.

[0024] As shown in FIG. 11 , the engine 70 includes a piston 71 and a cylinder head 72. The engine 70 defines a combustion chamber 25 by the cylinder bore 30, the piston 71, and the cylinder head 72. The piston 71 includes a piston crown surface 73 that faces the combustion chamber 25. A first piston inclined surface 81 is formed on an annular outer peripheral edge 80 that constitutes part of the piston crown surface 73 and is positioned closer to the intake port 26 than the piston center C1a. The first piston inclined surface 81 is an inclined surface that approaches the cylinder head 72 as it approaches the outer edge 73o of the piston crown surface 73. The second piston inclined surface 82 is formed on the outer peripheral edge 80 of the piston crown surface 73 and is positioned closer to the exhaust port 28 than the piston center C1a. The second piston inclined surface 82 is an inclined surface that inclines away from the cylinder head 72 as it approaches the outer edge 73o of the piston crown surface 73.

[0025] The cylinder head 72 is formed with a combustion chamber surface 74 facing the combustion chamber 25, i.e., the combustion chamber surface 74 opposing the piston crown surface 73. An annular outer peripheral edge 90 constituting a part of the combustion chamber surface 74 is formed with a first head inclined surface 91 positioned closer to the intake port 26 than the combustion chamber center C1b. That is, the outer peripheral edge 90 of the combustion chamber surface 74 is formed with a first head inclined surface 91 opposing the first piston inclined surface 81. This first head inclined surface 91 is an inclined surface that inclines away from the piston crown surface 73 as it approaches the outer edge 25o of the combustion chamber 25, i.e., the outer edge 74o of the combustion chamber surface 74. In addition, the outer peripheral edge 90 of the combustion chamber surface 74 is formed with a second head inclined surface 92 positioned closer to the exhaust port 28 than the combustion chamber center C1b. That is, the outer peripheral edge 90 of the combustion chamber surface 74 is formed with a second head inclined surface 92 opposing the second piston inclined surface 82. The second head inclined surface 92 is an inclined surface that approaches the piston crown surface 73 as it approaches the outer edge 25 o of the combustion chamber 25 , that is, the outer edge 74 o of the combustion chamber surface 74 .

[0026] 12, a squish area S1x is defined between the first head inclined surface 91 and the first piston inclined surface 81, and a squish area S2x is defined between the second head inclined surface 92 and the second piston inclined surface 82. This makes it possible to strengthen the tumble flow Ft by the jet flows Fs1 and Fs2 from the squish areas S1x and S2x.

[0027] 11, from the intake stroke to the compression stroke of the engine 70, much of the intake air flows into the gap Gx between the intake port 26 and the intake valve 27, generating a tumble flow Ft, which is a vertical vortex air flow, within the cylinder bore 30. Then, as shown in FIG. 12, when the piston 71 reaches near top dead center at the end of the compression stroke, a jet flow Fs1 is jetted obliquely downward from the squish area S1x defined between the first head inclined surface 91 and the first piston inclined surface 81 toward the exhaust port 28. Similarly, when the piston 71 reaches near top dead center at the end of the compression stroke, a jet flow Fs2 is jetted obliquely upward from the squish area S2x defined between the second head inclined surface 92 and the second piston inclined surface 82 toward the intake port 26.

[0028] At this time, within the combustion chamber 25, a flow Ft1 directed toward the exhaust port 28 is formed in the lower part of the combustion chamber 25, and a flow Ft2 directed toward the intake port 26 is formed in the upper part of the combustion chamber 25 as the tumble flow Ft. In other words, the jet flow Fs1 directed obliquely downward from the squish area S1x can strengthen the flow component Ft1 of the tumble flow Ft directed toward the exhaust port 28. Furthermore, the jet flow Fs2 directed obliquely upward from the squish area S2x can strengthen the flow component Ft2 of the tumble flow Ft directed toward the intake port 26. This makes it possible to generate a strong tumble flow Ft in the combustion chamber 25 at the end of the compression stroke, thereby increasing the combustion efficiency of the air-fuel mixture and improving the thermal efficiency of the engine 70.

[0029] The present invention is not limited to the above-described embodiment and may be modified in various ways without departing from the spirit and scope of the present invention. In the illustrated example, the first piston inclined surface 51 and the first head inclined surface 61 are parallel to each other, and the second piston inclined surface 52 and the second head inclined surface 62 are parallel to each other. However, this is not limiting. The inclination angles of the first piston inclined surface 51 and the first head inclined surface 61 relative to the center line C3 may be different from each other, and the inclination angles of the second piston inclined surface 52 and the second head inclined surface 62 relative to the center line C3 may be different from each other. Furthermore, the inclination angles of the first piston inclined surface 51 and the second piston inclined surface 52 relative to the center line C3 may be the same or different from each other. Similarly, the inclination angles of the first head inclined surface 61 and the second head inclined surface 62 relative to the center line C3 may be the same or different from each other. In the example shown in Figure 11, the first piston inclined surface 81 and the first head inclined surface 91 are formed parallel to each other, and the second piston inclined surface 82 and the second head inclined surface 92 are formed parallel to each other, but this is not limited to this.

[0030] The inclination angles of the first piston inclined surface 51, the second piston inclined surface 52, the first head inclined surface 61, and the second head inclined surface 62 relative to the center line C3 may be constant in the circumferential direction of the circular piston crown surface 40 and the combustion chamber surface 59, or may vary in the circumferential direction of the piston crown surface 40 and the combustion chamber surface 59. In the example shown in FIG. 4, the circumferential lengths of the first piston inclined surface 51 and the second piston inclined surface 52 are the same, but this is not limited thereto, and the circumferential lengths of the first piston inclined surface 51 and the second piston inclined surface 52 may be different from each other. Similarly, in the example shown in FIG. 6, the circumferential lengths of the first head inclined surface 61 and the second head inclined surface 62 are the same, but this is not limited thereto, and the circumferential lengths of the first head inclined surface 61 and the second head inclined surface 62 may be different from each other. 11 , the inclination angles of the first piston inclined surface 81, the second piston inclined surface 82, the first head inclined surface 91, and the second head inclined surface 92 relative to the center line C3 may be constant in the circumferential direction of the circular piston crown surface 73 and the combustion chamber surface 74, or may vary in the circumferential direction of the piston crown surface 73 and the combustion chamber surface 74. The circumferential lengths of the first piston inclined surface 81 and the second piston inclined surface 82 may be the same or different. Furthermore, the circumferential lengths of the first head inclined surface 91 and the second head inclined surface 92 may be the same or different.

[0031] The illustrated engines 10, 70 are engines mounted on a vehicle 11, but the present invention is not limited to this and may be applied to engines used as power sources for other devices, etc. Furthermore, the illustrated engines 10, 70 are gasoline engines that use gasoline as fuel, but the present invention is not limited to this and may be applied to engines that use diesel, hydrogen, or other fuels. Furthermore, to further strengthen the tumble flow in the combustion chamber 25, a tumble valve such as a TGV (Tumble Generation Valve) that controls the flow direction of intake air may be attached to the cylinder heads 24, 72. [Explanation of symbols]

[0032] 10 Engine 20,21 Cylinder block (cylinder body) 24 Cylinder head 25 Combustion chamber 25o outer edge 26 Intake port 28 Exhaust port 30 cylinder bore 31 Piston 32 Piston pin 40 Piston crown surface 40o outer edge 50 outer edge 51 First piston inclined surface 52 Second piston inclined surface 59 Combustion chamber surface 59o outer edge 60 outer edge 61 First head inclined surface 62 Second head inclined surface 70 Engine 71 Piston 72 Cylinder head 73 Piston crown surface 73o outer edge 74 Combustion chamber surface 74o outer edge 80 outer edge 81 First piston inclined surface 82 Second piston inclined surface 90 outer edge 91 First head inclined surface 92 Second head inclined surface C1a Piston center C3 Cylinder bore centerline C4 Piston pin centerline PL1 Reference plane

Claims

1. An engine having a cylinder body, a cylinder head attached to the cylinder body and having an intake port and an exhaust port formed therein; a piston accommodated in a cylinder bore of the cylinder body and defining a combustion chamber between the piston and the cylinder head; and The piston is a first piston inclined surface formed on an outer peripheral edge of a piston crown surface, the first inclined surface inclining toward the cylinder head as it approaches the outer edge of the piston crown surface; a second piston inclined surface formed on the outer peripheral edge of the piston crown surface, the second piston inclined surface inclined away from the cylinder head as it approaches the outer edge of the piston crown surface; Equipped with The first piston inclined surface is formed at a position point-symmetrical to the second piston inclined surface with respect to the center of the piston. engine.

2. 2. The engine of claim 1, The cylinder head a first inclined face facing the first inclined face and inclined away from the piston crown face as it approaches the outer edge of the combustion chamber; a second head inclined surface that faces the second piston inclined surface and is inclined so as to approach the piston crown surface as it approaches the outer edge of the combustion chamber; Equipped with engine.

3. 3. The engine of claim 2, When a virtual plane that includes the center line of the cylinder bore and is perpendicular to the center line of the piston pin is defined as a reference plane, the first piston inclined surface, the second piston inclined surface, the first head inclined surface, and the second head inclined surface intersect with the reference plane; engine.

4. In the engine according to any one of claims 1 to 3, the first piston inclined surface is located closer to the exhaust port than the center of the piston, The second piston inclined surface is located closer to the intake port than the center of the piston. engine.

5. In the engine according to any one of claims 1 to 3, the first piston inclined surface is located closer to the intake port than the center of the piston, The second piston inclined surface is located closer to the exhaust port than the center of the piston. engine.

6. In the engine according to claim 1, The width of the first piston inclined surface and the width of the second piston inclined surface are the same. engine.

7. In the engine according to claim 1, The inclination angle of the first piston inclined surface and the inclination angle of the second piston inclined surface are the same. engine.

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