Two-cycle engine

Abstract

To provide a two-cycle engine capable of achieving stable operation even when hydrogen fuel is used.SOLUTION: In a two-cycle engine 1, a cylinder 2 includes an intake hole 12 communicating with a crank chamber 6a through a bore 3, an exhaust hole 13 communicating with the bore 3 and arranged to face the intake hole 12 in the radial direction of the bore 3, an intake side scavenging hole 14 and an exhaust side scavenging hole 16 communicating the bore 3 with the crank chamber 6a, and an injector 30 having an injection hole 31 communicating with the bore 3 and injecting fuel containing hydrogen into the bore 3. The injector 30 injects the fuel into the bore 3 at timing when the exhaust hole 13 is closed in a rising process in which a piston 4 moves from a bottom dead center to a top dead center.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a two-stroke engine that runs on hydrogen as fuel. [Background technology]

[0002] As described in Patent Document 1, a two-stroke engine is known in which the hydrogen passage of a hydrogen injector is connected to the fuel passage of a fuel injector, and fuel and hydrogen are injected at a predetermined timing. In this engine, hydrogen is injected after the scavenging passage opens, and the injection of hydrogen is terminated before the scavenging passage closes. Fuel stored in the fuel passage is supplied to the combustion chamber through the scavenging passage by the injection of hydrogen. The mixing of hydrogen improves the ignition ability of the fuel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-18664 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned two-stroke engine, there is a possibility of a phenomenon called "preignition" occurring, in which fuel containing hydrogen ignites before the spark (discharge) of the ignition plug. Normally, the spark of the ignition plug ignites the mixture at the appropriate time. However, when hydrogen fuel is included, the highly ignitable hydrogen fuel causes the mixture to ignite naturally (self-ignition phenomenon). This type of preignition can lead to malfunctions such as engine stalls, unstable or reverse rotation of the engine, or engine damage. It has been difficult to achieve stable operation in a two-stroke engine that runs on hydrogen fuel.

[0005] An object of the present invention is to provide a two-stroke engine that can achieve stable operation even when using hydrogen fuel. [Means for solving the problem]

[0006] [1] One aspect of the present disclosure is a two-stroke engine (1) including: a cylinder (2) provided with a bore portion (3) and a combustion chamber (11) connected to one side of the bore portion (3) in an axial (L) direction; a crankcase (6) disposed on the other side of the cylinder (2) in the axial (L) direction and provided with a crank chamber (6a) connected to the other side of the bore portion (3); a piston (4) disposed in the bore portion (3) and capable of reciprocating along the axial (L) direction between the combustion chamber (11) and the crank chamber (6a); and a connecting rod (10) connecting the piston (4) to a crankshaft (7a) disposed in the crank chamber (6a), The piston (2) is provided with an intake hole (12) communicating with the crank chamber (6a) via the bore portion (3), an exhaust hole (13) communicating with the bore portion (3) and arranged so as to face the intake hole (12) in the radial direction of the bore portion (3), at least one scavenging hole (14, 16) communicating between the bore portion (3) and the crank chamber (6a), and an injector (30) having an injection hole (31) communicating with the bore portion (3) and for injecting fuel containing hydrogen into the bore portion (3). The injector (30) injects fuel into the bore portion (3) in accordance with the timing at which the exhaust hole (13) is closed during the upward stroke in which the piston (4) moves from the bottom dead center to the top dead center.

[0007] According to the two-stroke engine (1) of [1], fuel containing hydrogen is injected by the injector (30) into the bore portion (3) in synchronization with the closing of the exhaust hole (13). During the ascending stroke of the piston (4), the scavenging stroke in which fresh air (air) is introduced is completed, and then the exhaust hole (13) is also closed. High-temperature exhaust gas is discharged from the exhaust hole (13), and fuel is injected in synchronization with the closing of the exhaust hole (13) (i.e., the completion timing of the exhaust stroke). At this point, the discharge of high-temperature burned exhaust gas is completed, and the temperature inside the cylinder (2) has been reduced by the introduction of low-temperature fresh air (air) in the scavenging stroke. Therefore, the fuel can be introduced into the combustion chamber (11) in an environment below the self-ignition temperature of the fuel. As a result, the self-ignition phenomenon can be prevented from occurring before the timing of the spark (discharge) of the ignition plug, and stable operation can be achieved.

[0008] [2] In the two-stroke engine (1) of [1] above, the injection hole (31) of the injector (30) may open into the bore portion (3) at a position equal to or slightly higher than one edge of the exhaust hole (13) in the axial direction (L). The temperature of the fresh air becomes high due to compression, but according to this configuration, the fuel injection position can be as close as possible to the exhaust hole (13) in the axial direction (L) so that the fresh air can be placed in a low-temperature environment at the same time as the fresh air starts to be compressed. In other words, the fuel injection position can be moved away from a position close to the combustion chamber (11) which becomes high-pressure and high-temperature. This allows low-temperature hydrogen to be introduced into the bore portion (3) which is in a low-temperature environment, preventing the temperature from increasing due to compression and more reliably preventing the self-ignition phenomenon.

[0009] [3] In the two-stroke engine (1) of [1] or [2] above, the injector (30) may be attached to the cylinder (2) at a position adjacent to one side of the intake hole (12) in the direction of the axis (L). With this configuration, the injector (30) can be attached at a position far from the combustion chamber (11) (i.e., at a position in the bore portion (3) at the start of compression where there is no pressure increase), so that an inexpensive injector (30) for low pressure can be used. An injector that can withstand high pressure and high temperature is expensive, but the above configuration makes it possible to suppress the increase in cost.

[0010] [4] In the two-stroke engine (1) of any one of the above [1] to [3], the connection position (C) of the piston (4) with the connecting rod (10) may be offset toward the intake hole (12) with respect to a straight line (A1) that passes through the rotation center (R) of the crankshaft (7a) and is parallel to the reciprocating direction of the piston (4). By offsetting the connection position (C), the exhaust hole (13) can be opened at an earlier crank angle. Since the opening timing of the exhaust hole (13) is earlier, high-temperature exhaust gas can be discharged earlier, so that high-temperature burnt gas can be reliably discharged with high exhaust efficiency, and the self-ignition phenomenon can be more reliably prevented. Effect of the Invention

[0011] According to the present invention, even when hydrogen fuel is used, the spontaneous ignition phenomenon can be prevented and stable operation can be achieved. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a side view of a two-stroke engine according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a vertical cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a block diagram showing a schematic configuration related to fuel injection control. [Figure 4] FIG. 4 is a vertical sectional view showing a state in which the piston is located at the bottom dead center. [Diagram 5] FIG. 5 is a vertical cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a vertical cross-sectional view showing a state in which the exhaust hole is closed in the ascending stroke (at the completion timing of the exhaust stroke). [Figure 7] FIG. 7 is an enlarged cross-sectional view showing a part of FIG. [Figure 8] FIG. 8 is a vertical cross-sectional view taken along line VIII-VIII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted. In the following description, when "upper and lower" are used, it is based on the case where the cylinder body 2a is erected so that the bore portion 3 of the cylinder 2 extends vertically with the opening into which the piston 4 is inserted facing downward. "Upward" corresponds to one side in the axial L direction of the bore portion 3, and "downward" corresponds to the lower side in the axial L direction.

[0014] As shown in Figs. 1 and 2, the engine (two-stroke engine) 1 is a two-stroke engine that employs a sinule system as a scavenging method, and is installed in, for example, a brush cutter or a backpack power sprayer. The engine 1 includes a cylinder 2, a piston 4 that reciprocates in a bore portion 3 in the cylinder 2, a crankcase 6 that is connected to the lower side of the cylinder 2 and has a crank chamber 6a that is connected to the bore portion 3, and a crank mechanism 7 that is disposed in the crank chamber 6a of the crankcase 6. A piston pin 8 that is disposed in the piston 4 and a crank pin 9 of the crank mechanism 7 that is disposed in the crankcase 6 are connected by a connecting rod 10. As a result, the connecting rod 10 connects the piston 4 to a crankshaft 7a that is disposed in the crank chamber 6a. The piston 4 is disposed in the bore portion 3, and is capable of reciprocating along the axis L direction between a combustion chamber 11 and the crank chamber 6a. In the following description, the connecting rod 10 will be referred to as a connecting rod 10.

[0015] The cylinder 2 is formed with a combustion chamber 11, a cylindrical bore portion 3 connected to the combustion chamber 11 and into which a piston 4 is inserted, an intake hole 12 and an exhaust hole 13 communicating with the bore portion 3, a pair of intake side scavenging holes 14, and a pair of exhaust side scavenging holes 16. The cylinder 2 has a cylinder body 2a and a pair of scavenging cassettes 2b fitted into the lower portion of the cylinder body 2a. The pair of scavenging cassettes 2b are fitted and fixed in two openings formed so as to face each other in the radial direction of the bore portion 3. The pair of intake side scavenging holes 14 and the pair of exhaust side scavenging holes 16 are formed, for example, by the cylinder body 2a and the pair of scavenging cassettes 2b (see FIG. 2).

[0016] The bore 3 has a cylindrical bore surface 3a and extends along the axis L inside the cylinder 2. The bore 3 is open on its bottom dead center side (the lower side in FIG. 2) and communicates with the crank chamber 6a. A recessed combustion chamber 11 is formed at the end of the bore 3 on the top dead center side, and a discharge electrode 18a of an ignition plug 18 is disposed inside the combustion chamber 11. An ignition plug mounting hole 19 into which the ignition plug 18 is mounted is provided near the combustion chamber 11 in the cylinder body 2a.

[0017] The intake hole 12 and the exhaust hole 13 are each communicated with the bore portion 3, and the exhaust hole 13 is disposed slightly closer to the top dead center than the intake hole 12 in the direction of the axis L. The intake hole 12 and the exhaust hole 13 are disposed to face each other in the radial direction of the bore portion 3. In other words, the intake hole 12 and the exhaust hole 13 are disposed to be shifted from each other by approximately 180° in the circumferential direction of the bore portion 3.

[0018] The intake side scavenging holes 14 are for introducing fresh air into the bore portion 3 and the combustion chamber 11 in the scavenging process, and extend along the axis L inside the side wall of the cylinder 2. In this embodiment, the fresh air is only air taken in through an air cleaner (not shown) or the like. The top dead center end of the intake side scavenging holes 14 communicates with the bore portion 3 at substantially the same position as the exhaust hole 13 in the axis L direction. The intake side scavenging holes 14 are arranged spaced apart from each other in the circumferential direction of the bore portion 3. More specifically, the intake side scavenging holes 14 are arranged substantially symmetrically with respect to a virtual line connecting the intake hole 12 and the exhaust hole 13 in the radial direction. The intake side scavenging holes 14 are provided so that the fresh air introduced into the bore portion 3 is directed toward the intake hole 12. The bottom dead center end of the intake side scavenging holes 14 communicates with the above-mentioned crank chamber 6a.

[0019] As shown in FIG. 2, the crank mechanism 7 has a crankshaft 7a, a pair of crank webs 7b connected to the crankshaft 7a, and a pair of connecting portions 7c (see also FIG. 5) provided on the radially opposite sides of the crank webs 7b. The connecting rod 10 has a small end 21 disposed in the bore portion 3, a big end 22 disposed in the crank chamber 6a, and a rod body 23 connecting the small end 21 and the big end 22. A piston pin 8 is inserted into the small end 21 of the connecting rod 10, and the small end 21 is rotatably connected to the piston 4 via the piston pin 8. A crank pin 9 is inserted into the big end 22 of the connecting rod 10, and the big end 22 is rotatably connected to the connecting portion 7c of the crank mechanism 7 via the crank pin 9. When the crankshaft 7a is driven to rotate around the rotation center R, the connecting center P of the connecting rod 10 relative to the crankshaft 7a moves circularly around the rotation center R of the crankshaft 7a.

[0020] Next, the position of the piston 4 will be described in detail with reference to FIG. 6. FIG. 6 is a vertical cross-sectional view showing a state in which the exhaust hole 13 is closed (i.e., a closed hole state) during the upward stroke of the piston 4. As shown in FIG. 6, the connection position C of the piston 4 with the connecting rod 10 is offset toward the intake hole 12 side with respect to a straight line A1 that passes through the rotation center R of the crankshaft 7a (see FIG. 8) and is parallel to the reciprocating direction of the piston 4 (i.e., parallel to the axis L of the bore portion 3) (see the offset distance D shown in the figure). From another perspective, the connection position C is on the central axis A2 of the piston 4, and the exhaust hole 13 is provided on the opposite side of the straight line A1 to the offset side of the connection position C. The central axis A2 of the piston 4 coincides with the axis L of the bore portion 3. The axis L of the bore portion 3 may be located at any position in the circumferential direction (any position within a range of 360°) as long as the position of the exhaust hole 13 in the height direction is maintained.

[0021] The engine 1 is a piston valve type two-stroke engine in which an intake port 12 is opened and closed by a piston 4 reciprocating in a bore portion 3. In the engine 1, air taken in through the intake port 12 passes through a crank chamber 6a and is introduced into the bore portion 3 through a pair of intake side scavenging holes 14 and a pair of exhaust side scavenging holes 16. The engine 1 of this embodiment uses hydrogen fuel. The hydrogen fuel is injected (introduced) into the bore portion 3 from a fuel source F (see FIG. 3). That is, the hydrogen fuel is directly injected into the bore portion 3 without passing through the crank chamber 6a, the pair of intake side scavenging holes 14, or the pair of exhaust side scavenging holes 16.

[0022] As shown in Figs. 1 and 2, the cylinder 2 is provided with an injector 30 that injects hydrogen fuel into the bore portion 3. The injector 30 is attached to the cylinder 2 at a position adjacent to the upper side (one side) of the intake port 12 in the direction of the axis L. The injector 30 is fixed to the cylinder 2 by an appropriate fastening member or the like. The injector 30 has an injection hole 31 that communicates with the bore portion 3. A center line 31L (see Fig. 7) of the injection hole 31 is oriented in a position and direction perpendicular to the axis L of the bore portion 3 (i.e., in the radial direction), for example. The injector 30 has a built-in valve such as a coil-type solenoid valve (not shown). The valve opens and closes a fuel flow path connected to the injection hole 31.

[0023] As shown in FIG. 7, the injection hole 31 extends toward the center (axis L) of the bore portion 3. The injection hole 31 opens into the bore portion 3 at a position slightly higher than the upper end (edge) 13b of the opening 13a of the exhaust hole 13 in the axial direction. More specifically, the center line 31L of the injection hole 31 is located at a position slightly higher than the upper end 13b of the opening 13a. To explain the matter of "located at a slightly higher position" in more detail, for example, it is preferable that the difference (distance) in the position in the axial direction L between the upper end 13b of the opening 13a and the center line 31L of the injection hole 31 is within a range of 20% or less of the distance from the closed hole position of the exhaust hole 13 (i.e., the above-mentioned upper end 13b) to the top dead center. The injection hole 31 may open into the bore portion 3 at the same position as the upper end (edge) 13b of the opening 13a of the exhaust hole 13 in the axial direction L. In this case, the center line 31L of the injection hole 31 may coincide with the position of the upper end 13b of the opening 13a.

[0024] In this embodiment, hydrogen fuel is used. The hydrogen fuel is filled in a compressed gas state in a fuel source F constituted by a pressure tank or the like. A mixed gas of hydrogen and other fuels may be used in the engine 1. In this specification, "fuel containing hydrogen" includes both hydrogen fuel consisting of only hydrogen (100% hydrogen) and mixed fuel of hydrogen and other fuels. According to the engine 1 of this embodiment, which solves the problem of the self-ignition phenomenon (preignition) when hydrogen fuel is used, the problem of the self-ignition phenomenon is easily solved and normal operation is possible even when a mixed fuel containing hydrogen is used.

[0025] FIG. 3 is a block diagram showing a schematic configuration related to fuel injection control. As shown in FIG. 3, in the engine 1, only air not containing hydrogen fuel is taken in through the intake port 12. An ECU (engine control unit) 40 controls the engine 1. The ECU 40 controls the amount of air by adjusting the opening of a throttle valve (not shown), and also controls the injector 30. The ECU 40 controls the timing at which hydrogen fuel is injected by the injector 30. A pressure control valve (regulator) (not shown) is provided between the fuel source F and the injector 30. The pressure control valve keeps the pressure of hydrogen fuel applied to the injector 30 constant at all times. The ECU 40 can precisely control the injection timing and injection time (opening time of the injector 30) of the fuel by the injector 30. This allows precise control of the supply amount of hydrogen introduced. The exhaust gas discharged from the exhaust port 13 is released into the atmosphere through the muffler 5.

[0026] In this embodiment, the injector 30 is controlled by the ECU 40 to inject hydrogen fuel into the bore 3 in accordance with the timing at which the exhaust hole 13 is closed during the upward stroke in which the piston 4 moves from the bottom dead center to the top dead center. The injector 30 needs to be able to inject fuel at a pressure higher than the internal pressure of the bore 3, but since the internal pressure of the bore 3 is approximately the same as atmospheric pressure at the above-mentioned timing at which the exhaust hole 13 is closed, it is sufficient for the injector 30 to inject hydrogen fuel at a low pressure. A general-purpose injector can be used as the injector 30.

[0027] Next, the operation of the engine 1 will be described. As shown in Fig. 2, when the piston 4 reaches the vicinity of the top dead center, the mixture explodes in the combustion chamber 11, and the piston 4 descends toward the bottom dead center. As the piston 4 continues to descend, the exhaust hole 13 opens and the combustion gas is exhausted. Then, slightly after the exhaust hole 13 opens, the intake side scavenging hole 14 and the exhaust side scavenging hole 16 are exposed in the bore portion 3, and the scavenging stroke begins (see Figs. 4 and 5).

[0028] Next, as the piston 4 rises from the bottom dead center to the top dead center, the intake side scavenging port 14 and the exhaust side scavenging port 16 are closed by the piston 4. The exhaust port 13 is also closed by the piston 4. As shown in Figs. 6 and 8, the injector 30 is controlled by the ECU 40 to inject hydrogen fuel into the bore 3 at the timing when the exhaust port 13 is closed during the upward stroke of the piston 4. This causes air and hydrogen fuel to mix, generating an air-fuel mixture. As shown in Figs. 6, 7, and 8, when hydrogen fuel is injected, the opening 13a of the exhaust port 13 is closed, but the opening 31a of the injection port 31 is open. The top 4a of the piston 4 is slightly raised above the peripheral end 4b of the piston 4. At this time, as shown in FIG. 8, when viewed from a direction perpendicular to the axis L (the direction facing the injector 30), the opening 31a of the injection hole 31 appears to protrude slightly from the top 4a of the piston 4 or is hidden by the top 4a of the piston 4.

[0029] The injection timing of the hydrogen fuel may be when the upper end 13b of the opening 13a of the exhaust hole 13 is closed by the piston 4, or may be slightly before or after that. Specifically, the timing that is permitted "before" the exhaust hole 13 is closed is, for example, a timing that does not cause "blow-by" in which the hydrogen fuel introduced into the bore portion 3 escapes directly to the exhaust hole 13. The timing that is permitted "after" the exhaust hole 13 is closed is, for example, a timing at which the internal pressure of the bore portion 3 begins to rise due to compression after the exhaust hole 13 is closed. In this way, the injector 30 injects the hydrogen fuel into the bore portion 3 in accordance with the timing at which the exhaust hole 13 is closed during the upward stroke of the piston 4. From another perspective, the injector 30 injects the hydrogen fuel into the bore portion 3 at least before the peripheral end portion 4b of the piston 4 completely closes the opening 31a of the injection hole 31.

[0030] As the piston 4 moves further upward, the mixture in the combustion chamber 11 is compressed. As the piston 4 moves further upward, the intake port 12 communicates with the crank chamber 6a through the bore portion 3, and fresh air is introduced into the crank chamber 6a (see FIG. 2).

[0031] According to the engine 1 of this embodiment, fuel containing hydrogen is injected into the bore portion 3 by the injector 30 in synchronization with the timing at which the exhaust hole 13 is closed. During the ascending stroke of the piston 4, the scavenging stroke in which fresh air (air) is introduced is completed, and then the exhaust hole 13 is also closed. High-temperature exhaust gas is discharged from the exhaust hole 13, and fuel is injected in synchronization with the timing at which the exhaust hole 13 is closed (i.e., the timing at which the exhaust stroke is completed). At this point, the discharge of high-temperature burned exhaust gas is completed, and the temperature inside the cylinder 2 is reduced by the introduction of low-temperature fresh air (air) in the scavenging stroke. Therefore, the fuel can be introduced into the combustion chamber 11 in an environment below the self-ignition temperature of the fuel. As a result, it is possible to prevent the self-ignition phenomenon from occurring before the timing of the spark (discharge) of the ignition plug, and stable operation can be achieved.

[0032] The injection hole 31 of the injector 30 opens into the bore portion 3 at a position equal to or slightly higher than one edge of the exhaust hole 13 in the direction of the axis L. This allows the fuel injection position to be as close as possible to the position of the exhaust hole 13 in the direction of the axis L. In other words, the fuel injection position can be moved away from a position close to the combustion chamber 11, which becomes high pressure and high temperature. This allows low-temperature hydrogen to be introduced into the bore portion 3, which has a low-temperature environment, preventing the hydrogen from becoming hot due to compression and more reliably preventing the self-ignition phenomenon.

[0033] The injector 30 is attached to the cylinder 2 at a position adjacent to one side of the intake hole 12 in the direction of the axis L. This allows the injector (30) to be attached at a position far from the combustion chamber (11) (i.e., a position in the bore 3 at the start of compression where there is no pressure increase), making it possible to use a low-cost, normal-specification, low-pressure injector (30). An injector that can withstand high pressure and high temperature incurs high costs, but the above-mentioned configuration makes it possible to suppress the increase in costs.

[0034] The connecting position C of the piston 4 with the connecting rod 10 is offset toward the intake port 12 with respect to a straight line A1 that passes through the rotation center R of the crankshaft 7a and is parallel to the reciprocating direction of the piston 4. By offsetting the connecting position C, the exhaust port 13 can be opened at an earlier crank angle. The earlier opening timing of the exhaust port 13 allows high-temperature exhaust gas to be discharged earlier, so that the self-ignition phenomenon can be more reliably prevented. In addition, since the exhaust port 13 is closed at an earlier crank angle due to the offset, a decrease in the compression ratio can be prevented by the early closing of the exhaust port 13 while maintaining high exhaust efficiency due to the early opening of the exhaust port 13. A decrease in output due to a decrease in compression ratio can be prevented.

[0035] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the injector 30 may be attached at a position away from the cylinder 2. The position of the injection hole 31 may be closer to the combustion chamber 11 than the injection hole 31 in the above embodiment.

[0036] The piston 4 may not be offset, and the connecting position C may be located on the straight line A1.

[0037] The present invention is not limited to the case where four scavenging holes, i.e., a pair of intake side scavenging holes 14 and a pair of exhaust side scavenging holes 16, are provided in the cylinder 2, but may be configured with one intake side scavenging hole 14 and one exhaust side scavenging hole 16. The present invention is also applicable to a stratified scavenging engine that uses air. Also, only a pair of scavenging holes facing each other in the radial direction may be provided between the intake hole 12 and the exhaust hole 13. Only one scavenging hole may be provided for the cylinder 2. [Explanation of symbols]

[0038] DESCRIPTION OF THE SYMBOLS 1...engine (two-stroke engine), 2...cylinder, 3...bore portion, 4...piston, 6...crankcase, 6a...crank chamber, 7...crank mechanism, 11...combustion chamber, 12...intake hole, 13...exhaust hole, 13a...opening, 13b...upper end, 14...intake side scavenging hole (scavenging hole), 16...exhaust side scavenging hole (scavenging hole), 30...injector, 31...injection hole, A1...straight line, A2...central axis, C...connection position, D...offset distance, L...axis (of bore portion), P...connection center, R...center of rotation.

Claims

1. A two-stroke engine (1) comprising: a cylinder (2) provided with a bore portion (3) and a combustion chamber (11) connected to one side of the bore portion (3) in an axial (L) direction; a crankcase (6) disposed on the other side of the cylinder (2) in the axial (L) direction and provided with a crank chamber (6a) connected to the other side of the bore portion (3); a piston (4) disposed in the bore portion (3) and capable of reciprocating along the axial (L) direction between the combustion chamber (11) and the crank chamber (6a); and a connecting rod (10) connecting the piston (4) to a crankshaft (7a) disposed in the crank chamber (6a), The cylinder (2) has: an intake hole (12) communicating with the crank chamber (6a) via the bore portion (3); an exhaust hole (13) communicating with the bore portion (3) and arranged to face the intake hole (12) in the radial direction of the bore portion (3); At least one scavenging hole (14, 16) communicating between the bore portion (3) and the crank chamber (6a); an injector (30) having an injection hole (31) communicating with the bore portion (3) and injecting fuel containing hydrogen into the bore portion (3), The injector (30) injects the fuel into the bore portion (3) in synchronization with the timing at which the exhaust hole (13) is closed during an upward stroke in which the piston (4) moves from the bottom dead center to the top dead center. Two-stroke engine.

2. The injection hole (31) of the injector (30) opens into the bore portion (3) at a position equal to or slightly higher than an edge on one side of the exhaust hole (13) in the axial direction (L).

2. The two-stroke engine according to claim 1.

3. The injector (30) is attached to the cylinder (2) at a position adjacent to one side of the intake hole (12) in the axial direction (L).

3. A two-stroke engine according to claim 1 or 2.

4. a connecting position (C) of the piston (4) with the connecting rod (10) is offset toward the intake hole (12) with respect to a straight line (A1) that passes through a rotation center (R) of the crankshaft (7a) and is parallel to a reciprocating direction of the piston (4); 3. A two-stroke engine according to claim 1 or 2.

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