2-stroke engine

Abstract

To provide a two-stroke engine capable of enhancing a scavenging effect.SOLUTION: A two-stroke engine E according to an embodiment includes an intake port 16 which is provided on a top wall 12a of a combustion chamber 12, an exhaust port 18 which is provided on a side of a crankshaft 2 in a cylinder axial direction AX1 of a peripheral wall 12b of the combustion chamber 12, an intake valve 24 which is driven by a valve train 25 interlocking with the crankshaft 2 and opens / closes the intake port 16, and an offset wall 42 which is formed on the top wall 12a and covers a part of an opening of the intake valve 24 at the initial stage of opening of the intake valve 24.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application relates to a two-stroke engine.

Background Art

[0002] In some two-stroke engines, fresh air for scavenging combustion gases is guided to the periphery of the inner wall surface of the cylinder head located on the side opposite to the exhaust valve (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Depending on various situations such as the required output, displacement, and operating speed, further improvement of the scavenging effect may be required.

[0005] The disclosure of this application provides a two-stroke engine capable of enhancing the scavenging effect.

Means for Solving the Problems

[0006] A two-stroke engine according to one embodiment of the present disclosure includes an intake port provided in the top wall of a combustion chamber, an exhaust port provided on the crankshaft side with respect to the axial direction of the cylinder among the peripheral walls of the combustion chamber, an intake valve driven by a valve operating mechanism interlocked with the crankshaft to open and close the intake port, and an offset wall formed on the top wall to cover a part of the opening of the intake valve at the initial stage of opening of the intake valve.

[0007] A two-stroke engine according to another embodiment of the present disclosure includes an intake port provided in the top wall of a combustion chamber, a plurality of injectors provided in the top wall, an exhaust port provided on the crankshaft side with respect to the cylinder axis direction of the circumferential wall of the combustion chamber, and an intake valve driven by a valve train mechanism linked to the crankshaft to open and close the intake port. [Effects of the Invention]

[0008] According to one embodiment of the two-stroke engine of this disclosure, in the initial stage of intake valve opening, the offset wall partially blocks the gap to the combustion chamber. As a result, intake air is concentrated into the combustion chamber from the opposite side of the offset wall. Consequently, an intake airflow can be formed that flows from the intake port toward the circumferential wall of the combustion chamber and along the circumferential wall in the direction of the cylinder axis. The burnt gases are pushed out by the intake airflow and discharged from an exhaust port located on the crankshaft side of the circumferential wall of the combustion chamber. This concentrated and strong intake airflow pushes the burnt gases toward the crankshaft, thereby enhancing the scavenging effect of the burnt gases. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a two-stroke engine according to the first embodiment of this disclosure. [Figure 2] This is a simplified perspective view showing the intake airflow of the engine. [Figure 3] This is a simplified perspective view showing the fuel injection state of the engine. [Figure 4] This is a cross-sectional view along the line IV-IV in Figure 1. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present disclosure will be described below with reference to the drawings. Figure 1 is a cross-sectional view showing an engine according to the first embodiment of the present disclosure. The engine E of the present disclosure is a two-stroke engine in which, when the crankshaft 2 rotates once, the piston 4 connected to it moves two strokes, or one reciprocating motion, during which one cycle from intake, compression, combustion, to exhaust is completed. The engine E of this embodiment is a single-cylinder engine, but the engine E of the present disclosure may have two or more cylinders. The fuel for the engine E of the present disclosure may be a vaporized fuel containing hydrogen gas or hydrocarbons. In addition, the fuel may be a liquid fuel containing hydrocarbons, such as gasoline fuel, diesel fuel, or alcohol fuel.

[0011] In the following description, engine E is described as being positioned with its top dead center located on the upper side and its cylinder axis AX1 aligned vertically. In this case, "upper" refers to the side opposite the crankshaft axis along the cylinder axis AX1, i.e., the side of the piston's top dead center, and "lower" refers to the side of the crankshaft axis 2a along the cylinder axis AX1, i.e., the side of the piston's bottom dead center. In other words, "upper" is the direction from bottom dead center to top dead center along the cylinder axis AX1. Similarly, "lower" is the direction from top dead center to bottom dead center along the cylinder axis AX1. Furthermore, "upstream" refers to the "upstream side" in the direction of intake airflow, and "downstream" refers to the "downstream side" in the direction of intake airflow.

[0012] Engine E comprises a crankcase supporting a crankshaft 2 to which the piston 4 is connected, a cylinder 8 protruding upward from the crankcase, and a cylinder head 10 attached to the upper end of the cylinder 8. The cylinder 8 has a cylindrical internal space formed inside it. The piston 4 is formed in a cylindrical shape and is housed in the internal space of the cylinder 8. The piston 4 reciprocates along the cylinder axis AX1 as the crankshaft 2 rotates.

[0013] The combustion chamber 12 is formed by the cylinder head 10, the cylinder 8, and the piston 4. In other words, the combustion chamber 12 defines the combustion space where fuel burns. The combustion space is formed in a cylindrical shape coaxial with the cylinder axis AX1. Specifically, the cylinder head 10 constitutes the top wall 12a of the combustion chamber 12, the cylinder 8 constitutes the peripheral wall 12b of the combustion chamber 12, and the upper surface of the piston 4 constitutes the bottom wall 12c of the combustion chamber 12. Here, "top wall 12a of the combustion chamber 12" refers to the wall on the side where the intake port and injector, described later, are formed. In this embodiment, the top wall 12a refers to the upper wall of the combustion chamber 12, that is, the wall on the piston top dead center side.

[0014] A spark plug 15 is mounted on the top wall 12a of the combustion chamber 12. In this embodiment, the spark plug 15 is positioned coaxially with the cylinder axis AX1. The cylinder head 10 has an intake port 16 on one side (left side in Figure 1) of the cylinder axis AX1. In other words, the intake port 16 is positioned on one side (left side in Figure 1) of the direction perpendicular to the cylinder axis AX1 with respect to the orthogonal direction D1 perpendicular to the cylinder axis AX1. The intake port 16 is a passage formed inside the cylinder head 10.

[0015] The upstream end 16a of the intake port 16 in the direction of intake airflow opens to the outside of the cylinder head 10, i.e., outside the combustion chamber 12. The downstream end 16b of the intake port 16 in the direction of intake airflow opens into the combustion chamber 12.

[0016] Furthermore, an exhaust port 18 is formed in the peripheral wall 12b of the cylinder head 10. The exhaust port 18 is a passage formed inside the cylinder 8. The exhaust port 18 is located on the crankshaft side (lower side in Figure 1) with respect to the cylinder axis direction AX1 of the peripheral wall 12b of the combustion chamber 12. Also, the exhaust port 18 is located on the opposite side of the intake port 16 across the cylinder axis AX1, that is, on the other side in the orthogonal direction D1 (right side in Figure 1).

[0017] The exhaust port 18 is arranged at a position adjacent to the piston 4 when the piston 4 reaches the bottom dead center. The exhaust port 18 is arranged at a position blocked by the piston 4 when the piston 4 moves from the bottom dead center toward the top dead center.

[0018] The engine E of the present embodiment is a direct injection engine in which the fuel injector 22 has its injection port 22a opening into the combustion chamber 12 and fuel is directly injected into the combustion chamber 12. Details such as the arrangement of the injector 22 and the orientation of the injection port 22a will be described later.

[0019] Air A is supplied into the combustion chamber 12 from the intake port 16. This air A and the fuel F sprayed from the injector 22 are mixed in the combustion chamber 12 to generate an air-fuel mixture. This air-fuel mixture is compressed by the upward movement of the piston 4, ignited by the ignition plug 15, and burns. The combustion gas G is exhausted from the combustion chamber 12 through the exhaust port 18.

[0020] The engine E of the present disclosure includes a supercharger 20 that pressurizes the intake air (air) A supplied to the combustion chamber 12. In the present embodiment, the supercharger 20 is a mechanical supercharger that is rotationally driven by the crankshaft 2. However, the supercharger 20 is not limited to this, and for example, it may be a turbocharger that is rotationally driven by utilizing the exhaust flow.

[0021] The intake port 16 is opened and closed by the intake valve 24. Specifically, the downstream end 16b of the intake port 16 is opened and closed by the reciprocating motion of the intake valve 24. In FIG. 1, the intake valve 24 in the open valve state is shown by a solid line, and the intake valve 24 in the closed valve state is shown by a two-dot chain line.

[0022] In the present embodiment, no exhaust valve is provided in the exhaust port 18. The upstream end 18a of the exhaust port 18 is opened and closed by the reciprocating motion of the piston 4. Specifically, the exhaust port 18 is blocked when the piston 4 moves upward, and the exhaust port 18 is opened when the piston 4 moves downward.

[0023] The intake valve 24 has a valve body 24a that opens and closes the intake port 16, and a valve stem 24b that connects the valve body 24a to the valve train 25. The axis AX2 of the valve stem 24b of the intake valve 24 is inclined toward the intake side with respect to the cylinder axis AX1.

[0024] The valve body 24a of the intake valve 24 has a low truncated cone shape with its lower base facing the combustion chamber 12. The intake port 16 has a valve seat 28 on which the valve body 24a of the intake valve 24 sits. When the intake valve 24 moves upward, the outer surface of the valve body 24a sits on the valve seat 28, closing the intake port 16, and when the intake valve 24 moves downward, the valve body 24a moves away from the valve seat 28, opening the intake port 16.

[0025] The intake valve 24 is driven by a valve train 25 that is linked to the crankshaft 2. The valve train 25 causes the intake valve 24 to reciprocate once during one rotation of the crankshaft 2. The valve train 25 in this embodiment includes a camshaft 26 that rotates in conjunction with the crankshaft 2, and a rocker arm 27 that transmits the rotational motion of the camshaft 26 to open and close the valve.

[0026] Engine E of the present disclosure is an overhead valve engine in which the intake valve 24 is located on the top wall 12a of the fuel chamber 12. More specifically, Engine E of the present disclosure is an overhead valve engine in which the camshaft 26 is located on the cylinder head side camshaft It is an overhead valve (OHC) type. The rotation of the crankshaft 2 is transmitted to the camshaft 26 by, for example, a chain, belt, or gear. However, the engine E of this disclosure is not limited thereto and may be an overhead valve (OHV) type where the camshaft 26 is located on the cylinder side.

[0027] As shown in Figure 2, the engine E of this embodiment has two intake valves 24. However, the engine E of this disclosure is not limited to this, and for example, it may have one intake valve 24 or three or more. Note that the injector 22 is omitted in Figure 2.

[0028] As shown in Figure 1, the injector 22 is located on the opposite side of the intake port 16 (right side in Figure 1) across the cylinder axis AX1 at the top wall 12a of the combustion chamber 12. In other words, the injector 22 is located on the other side (right side in Figure 1) in the direction D1 perpendicular to the cylinder axis AX1.

[0029] The injector 22 is located on the opposite side of the intake port 16, with the spark plug 15 in between, and injects fuel F toward the peripheral wall 12b opposite the exhaust port 18. The injection axis AX3 of the injector 22 extends in a direction that is a combination of the direction along the cylinder axis AX1 and the direction toward the peripheral surface on the intake port 16 side. In this embodiment, the injector 22 is located in the cylinder head 10, but it may also be located in the cylinder block 8.

[0030] The injection axis AX3 of the injector 22 extends from the injection port 22a of the injector 22 toward the crankshaft 2 side (lower side in Figure 1) of the cylinder axis AX1, and is inclined toward the intake port valve 24 side (left side in Figure 1), which is one side of the perpendicular direction D. More specifically, the injection axis AX3 of the injector 22 extends toward the upper surface 12c of the piston 4 when the exhaust port 18 is blocked.

[0031] As shown in Figure 3, the engine E of this disclosure has a plurality of injectors 22. In this embodiment, two injectors 22 are provided. However, the number of injectors 22 is not limited to this, and may be one, three or more.

[0032] In this embodiment, the two injectors 22 are arranged such that their injection axes AX3 approach each other downstream. More specifically, the injection axes AX3 of the two injectors 22 intersect downstream. However, the injection axes AX3 of the multiple injectors 22 may be parallel or separated downstream.

[0033] All of the multiple injectors 22 may inject a fuel F such as hydrogen or gasoline. Furthermore, if the fuel F is hydrogen, the multiple injectors 22 may include injectors that inject hydrogen fuel F and injectors that inject water.

[0034] As shown in Figure 1, the intake valve 24 is offset above, i.e., upstream of, the injection port 22a of the injector 22. Specifically, the valve seat 28 on the intake port side is located above the injection port 22a of the injector 22. In other words, a step 32 is formed between the intake port 16 on the top wall 12a and the portion where the injection port 22a of the injector 22 is provided.

[0035] The step 32 is the portion of the intake valve 24a in the open state, shown by the solid line, that faces the intake valve 24 in a direction perpendicular to the axis AX2 of the intake valve 24. In other words, the valve seat 28 on the intake port side is positioned higher and further away from the portion of the top wall 12a on the cylinder axis AX1, which in this embodiment is the mounting portion of the spark plug 15. As a result, a step 32 is formed in the vertical direction between the lower surface of the valve seat 28 on the intake port side and the portion of the top wall 12a on the cylinder axis AX1.

[0036] When the intake valve 24 is fully open, i.e., moved to its lowest position in Figure 1, the portion of the top wall 12a above the cylinder axis AX1 is located above the valve body 24a of the intake valve 24. In other words, the valve body 24a of the fully open intake valve 24 and the portion of the top wall 12a above the cylinder axis AX1 are spaced apart in the vertical direction. This means that in the fully open state, intake air flows into the combustion space from the entire circumference of the intake port 16. Furthermore, the vertical gap between the top wall 12a and the valve body 24a of the fully open intake valve 24 is larger on the intake side (left side of Figure 1) than on the injector side (right side of Figure 1).

[0037] As shown in Figure 4, the step 32 is formed along the intake port 16, i.e., the valve body 24a of the intake valve 24, in a substantially concentric manner. The concentric formation occurs in the region of the intake port 16 adjacent to the injector 22 and in the region close to the peripheral wall 12b of the cylinder 8. The step 32 is formed in the top wall 12a, excluding the region on the opposite side of the intake port 16 from the injector 22, i.e., the intake-side region R1. In other words, the step 32 is not formed in the intake-side region R1.

[0038] Since no step 32 is formed in the intake region R1, when the intake valve 24, shown by the solid line in Figure 1, is open, a vertical intake flow Av along the cylinder axis AX1 is created from the gap between the top wall 12a and the valve body 24a of the intake valve 24.

[0039] In detail, when the intake valve 24 opens, a larger vertical gap is formed between the valve body 24a and the top wall 12a in the intake-side region R1 (Figure 4) than in the injector-side region R2 (Figure 4). In other words, the intake air flow rate is greater in the intake-side region R1. Furthermore, the intake air is more easily guided along the intake-side peripheral wall 12b in the combustion space. In addition, the vertical intake air flow Av is guided by the inclination of the valve body 24a and flows towards the peripheral wall 12b, then collides with the peripheral wall 12b and flows downward along the peripheral wall 12b.

[0040] As shown in Figure 1, an offset wall 42 is formed on the top wall 12a of the combustion chamber 12. The offset wall 42 covers a portion of the opening of the intake valve 24 when the intake valve 24 is initially open. More specifically, the offset wall 42 is located radially around the intake port 16, formed concentrically with the intake port 16, and is the portion that faces the valve body 24a of the intake valve 24 when the intake port 16 is open. In this embodiment, the step 32 constitutes the offset wall 42.

[0041] The offset wall 42 prevents intake air from flowing from the intake port 16 to the injection nozzle 22a of the injector 22 when the intake valve 24 is just beginning to open. In other words, a portion of the intake air flowing from the intake port 16 into the combustion chamber 12 is guided by the offset wall 42 and led into the combustion chamber 12, as shown by the solid arrow Ar in Figure 1.

[0042] Next, the intake flow of engine E in this embodiment will be explained. When engine E in Figure 1 is started, the crankshaft 2 rotates. In conjunction with the rotation of the crankshaft 2, the piston 4 moves up and down, and the intake valve 24 opens and closes. Specifically, near top dead center, the spark plug 15 ignites and an explosion occurs (explosion stroke), and as the piston 4 moves downward from top dead center, the exhaust port 18 opens and then the intake valve 24 opens (scavenging stroke). When scavenging is complete, intake air is introduced (intake stroke). Before reaching top dead center again, the intake valve 24 and exhaust port 18 close, the piston 4 rises and is compressed, and fuel is injected (compression stroke). In other words, after the piston 4 blocks the exhaust port 18, fuel F is injected by the injector 22. Thereafter, the explosion stroke, scavenging stroke, intake stroke and compression stroke are repeated.

[0043] In the engine E of this disclosure, there is a state in which both the intake port 16 and the exhaust port 18 are open. Specifically, the intake valve 24 begins to open just before the end of the scavenging stroke of the engine E, that is, before the piston 4 in Figure 1 closes the exhaust port 18. This allows intake and exhaust to be performed simultaneously, and the combustible gases in the cylinder can be scavenged with the fresh air taken in, so improvements in intake charging efficiency and improved scavenging effect of combustion gases can be expected. Furthermore, since the engine E of this disclosure has a supercharger 20 and the intake air from the intake port 16 is pressurized, scavenging from the intake port 16 to the exhaust port 18 can be achieved even when both the intake port 16 and the exhaust port 18 are open.

[0044] When the intake valve 24 opens during the scavenging stroke, a strong longitudinal intake airflow Av is created along the cylinder axis AX1 through the gap between the top wall 12a and the valve body 24a of the intake valve 24. Next, a portion of the intake air from the intake port 16 flows along the offset wall 42 (a weak intake airflow As).

[0045] In this way, a strong downward intake airflow Av along the cylinder axis AX1 and a weak swirling airflow As near the cylinder axis AX1 are created. By creating intake air that flows along the inner surface of different parts, unburned gases can be pushed out to the exhaust port 18 over a wide area.

[0046] On the other hand, the strong vertical intake airflow Av, as shown in Figure 2, flows downward along the inner wall surface of the cylinder 8, then hits the upper surface 12c of the piston 4, and flows along the upper surface 12c of the piston 4 towards the exhaust port 18. At this time, the intake air from the weak intake airflow As is pushed towards the exhaust port 18 by the strong intake airflow Av.

[0047] During the compression stroke, as shown in Figure 3, the strong intake airflow Av collapses, increasing the turbulence strength At within the combustion chamber 12. When the turbulence strength At within the combustion chamber 12 increases, fuel F is injected from the injector 22. This promotes the mixing of intake air (air A) and fuel F.

[0048] Furthermore, two injectors 22 are provided, and by colliding the fuel F jets from the two injectors 22, the fuel F jets are dispersed, making it easier for the intake air (air A) and fuel F to mix.

[0049] With the above configuration, when the intake valve 24 is initially open, the offset wall 42 partially blocks the gap to the combustion chamber 12. As a result, intake air is concentratedly introduced into the combustion chamber 12 from the opposite side of the offset wall 42. Consequently, a strong intake airflow Av is formed, flowing from the intake port 16 towards the peripheral wall 12b of the combustion chamber 12, and along the peripheral wall 12b in the cylinder axial direction AX1. The post-combustion gas is pushed out by the intake airflow Av and discharged from the exhaust port 18 located on the lower side of the peripheral wall 12b of the combustion chamber 12. By pushing the post-combustion gas to the exhaust port 18 with this concentrated, strong intake airflow Av, the scavenging effect of the post-combustion gas can be enhanced.

[0050] In this embodiment, the system includes an injector 22 for injecting fuel F, and the injection axis AX3 of the injector 22 may extend from the injection port 22a of the injector 22 toward the peripheral wall 12ba on the opposite side of the offset wall 42, with the intake valve 24 in between. With this configuration, the turbulence At strength after the collapse of the strong intake air A is more likely to cause the fuel F to collide with the intake air, which has a large turbulence strength, thus promoting the diffusion of the fuel F.

[0051] In this case, the injection axis AX3 of the injector 22 may extend toward the upper surface 12c of the piston 4 when the exhaust port 18 is blocked. With this configuration, the fuel F injected from the injector 22 is more likely to collide with the highly turbulent intake air At at the upper surface 12c of the piston 4 when the exhaust port 18 is blocked, further promoting the diffusion of the fuel F.

[0052] In this embodiment, the exhaust port 18 may be located on the peripheral wall 12b opposite the intake valve 24, straddling the cylinder axis AX1. With this configuration, the strong intake airflow A is more likely to flow along the upper surface 12c of the piston 4 and towards the exhaust port 18. This makes it easier to further enhance the scavenging effect.

[0053] In this embodiment, multiple injectors 22 may be provided. With this configuration, since the exhaust valve is omitted, it is easy to arrange multiple injectors 22 on the top wall 12a of the combustion chamber 22.

[0054] In this case, the injection axes AX3 of the multiple injectors 22 may approach each other downstream. Alternatively, the injection axes AX3 of the multiple injectors 22 may intersect downstream. With this configuration, the jets are dispersed by causing the ejected materials from the multiple injectors 22 to collide within the cylinder, thereby promoting the mixing of air and fuel F.

[0055] Furthermore, multiple injectors 22 may inject hydrogen fuel. In a hydrogen engine, there is a risk of pre-ignition, where hydrogen spontaneously ignites before being ignited by the spark plug, due to contact with the exhaust valve, which tends to become hot. With the above configuration, the exhaust valve is omitted, thus preventing pre-ignition.

[0056] Furthermore, the multiple injectors 22 may include injectors that inject hydrogen fuel and injectors that inject water. With this configuration, the temperature rise in the combustion chamber 12 is suppressed by injecting water, thus preventing pre-ignition.

[0057] In this embodiment, there are two intake ports 16, but this is not limited to one, and there may be one or three or more. Similarly, the exhaust ports 18 are not limited to one as in this embodiment, and multiple ports may be provided. It is preferable that the exhaust ports 18 are located on the opposite side of the cylinder AX1 axis from the intake ports 16.

[0058] The arrangement of the multiple injectors 22 at which the injection axis AX3 intersects can be selected as appropriate. For example, if there are two intake ports 16, the injectors 22 may be arranged parallel to them, or they may be arranged non-parallel to the intake ports 16, for example, perpendicular to them. Alternatively, the injectors 22 may be arranged in a plane perpendicular to the cylinder axis AX1, in the direction connecting the intake port 16 and the exhaust port 18. The two injectors 22 may have different injection timings.

[0059] This disclosure is not limited to the forms described above, and various additions, modifications, or deletions are permitted as long as they do not deviate from the gist of this disclosure. Therefore, such additions, modifications, or deletions are also included within the scope of this disclosure. [Explanation of Symbols]

[0060] 2 Crankshafts 4 pistons 12 Combustion chamber 12a Top wall 12b Surrounding wall 16 intake ports 18 exhaust ports 22 Injectors 22a Injector nozzle 24 Intake valves 25 Valve train 42 Offset Wall AX1 Cylinder Axis AX3 Injector Injection Axis E-engine

Claims

1. An intake port located on the top wall of the combustion chamber, Of the peripheral wall of the combustion chamber, the exhaust port provided on the crankshaft side with respect to the cylinder axis direction, An intake valve that is driven by a valve train mechanism linked to the crankshaft to open and close the intake port, An offset wall formed on the top wall covers a portion of the opening of the intake valve when the intake valve is initially open, An injector that injects fuel, Equipped with, The offset wall is a step formed between the intake port on the top wall and the portion where the injection port of the injector is provided. A two-stroke engine in which both ends of the aforementioned step are connected to the periphery of the top wall.

2. A two-stroke engine according to claim 1, wherein the injection axis of the injector extends from the injection port of the injector toward the peripheral wall opposite to the offset wall, with the intake valve in between.

3. A two-stroke engine according to claim 1, wherein the injection axis of the injector extends toward the upper surface of the piston when the exhaust port is blocked.

4. A two-stroke engine according to claim 1 or 2, wherein the exhaust port is located on the circumferential wall opposite to the intake valve, straddling the cylinder axis.

5. A two-stroke engine according to claim 1 or 2, wherein the vertical gap between the top wall and the valve body of the intake valve in the fully open state is formed to be larger on the intake side than on the injector side.

6. A two-stroke engine according to claim 1 or 2, wherein the offset wall is located around the radial circumference of the intake port and is formed along the intake port.

7. A two-stroke engine according to claim 1 or 2, wherein the intake port is provided only on the top wall of the combustion chamber.

8. A two-stroke engine according to claim 1 or 2, wherein the portion of the top wall on the intake side below the valve seat of the intake valve is inclined downward toward the intake side.

9. A two-stroke engine according to claim 1 or 2, wherein the valve seat on the intake port side of the intake valve is located above the injection port of the injector.

10. An intake port located on the top wall of the combustion chamber, Multiple injectors provided on the top wall, Of the peripheral wall of the combustion chamber, the exhaust port provided on the crankshaft side with respect to the cylinder axis direction, An intake valve that is driven by a valve train mechanism linked to the crankshaft to open and close the intake port, Equipped with, In a two-stroke engine, the intake valve, when blocked, is located above the nozzle of the injector.

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