2-cycle engine

Abstract

A two-cycle engine (1) comprises a cylinder (2) and a piston (4) that reciprocates along the axial direction within a bore (3). An intake port (12) is opened and closed by the piston (4). The two-cycle engine (1) comprises a crankcase (6) connected to the cylinder (2) and including a crank chamber (6a), a crank mechanism (7) disposed in the crank chamber (6a) and rotating around a crank shaft (7a), a connecting rod (10) including a small end (21) connected to the piston (4) and a large end (22) connected to the crank mechanism (7), and a fuel injector (30) mounted on the crankcase (6) that sprays mixed fuel onto the large end (22) by injecting mixed fuel in the tangential direction of the circumferential track of the large end (22).

Description

Technology Field

[0001] The present disclosure relates to a piston valve type two-cycle engine. Background Technology

[0002] Conventionally, as described in Patent Document 1, a fuel injection 2-cycle engine is known in which a main scavenging passage and an auxiliary scavenging passage are formed in the cylinder block. In this 2-cycle engine, a fuel injection device is mounted on the crankcase. The fuel injection device is directed to inject fuel toward the scavenging inlet of the auxiliary scavenging passage. Other fuel injection methods are known, such as a method of injecting fuel into the intake path leading to the crankcase or a method of directly injecting fuel into the combustion chamber. Prior art literature

[0003] Japanese Patent Publication No. Hei 7-224741 The problem to be solved

[0004] According to the injection method described in the aforementioned Patent Document 1, a two-cycle engine with excellent starting performance and responsiveness is provided. However, the supply of lubricating oil to the crankshaft or bearing parts has not been specifically considered. Conventionally, in order to lubricate the crankshaft or bearing parts, it was necessary to provide a separate passage for lubricating oil or to equip an oil pump. If lubrication is insufficient, there is a risk of problems such as seizure occurring.

[0005] The inventors have discovered that in a piston valve type 2-cycle engine, lubrication and cooling at the large end of the connecting rod placed inside the crankcase is a significant issue. Fuel such as gasoline is mixed with oil and supplied (injected) as a mixed fuel. From the perspective of fuel efficiency and environmental friendliness, a 2-cycle engine capable of performing lubrication and cooling with a small amount of mixed fuel is desired.

[0006] The present disclosure describes a two-cycle engine capable of lubricating and cooling the large end with a small amount of mixed fuel. means of solving the problem

[0007] One embodiment of the present disclosure comprises a piston valve type 2-cycle engine (1) in which an intake port is opened and closed by a piston (4) that reciprocates along an axial direction within a bore portion (3) of a cylinder (2), a crankcase connected to the cylinder (2) and including a crankcase (6a), a crank mechanism (7) disposed in the crankcase (6a) and rotating around a crankshaft (7a), a connecting rod including a small end portion (21) connected to the piston (4) and a large end portion (22) connected to the crank mechanism (7), and a fuel injector (30) mounted on the crankcase and spraying mixed fuel onto the large end portion (22) by injecting mixed fuel in a tangential direction of a circumferential track of the large end portion (22).

[0008] According to this 2-cycle engine (1), a fuel injector (30) mounted on the crankcase sprays a mixture of fuel onto the large end (22) of the connecting rod. At this time, the fuel injector (30) sprays the mixture of fuel in a tangential direction toward the circumferential track of the large end (22). The oil contained in the mixture of fuel lubricates and cools the large end (22). The fuel (gasoline, etc.) contained in the mixture of fuel also cools the large end (22). As a result, lubrication and cooling of the large end (22) can be performed with a small amount of mixture of fuel. Furthermore, since the mixture of fuel is injected into the crankcase rather than into the combustion chamber or bore (3), there is no need to consider pressure resistance and heat resistance regarding the surrounding components of the fuel injector (30).

[0009] The nozzle (31) of the fuel injector (30) may protrude into the crankcase (6a). With this configuration, since the mixed fuel can be injected from a position closer to the large end (22), it becomes easier to obtain the desired lubrication and cooling effects mentioned above.

[0010] The crank mechanism (7) includes a pair of crank webs (7b) connected to a crank shaft (7a) and separated in the axial direction of the crank shaft (7a), and the nozzle (31) of the fuel injector (30) may be positioned to pass through the gap (G) between the pair of crank webs (7b). With this configuration, the nozzle (31) can be positioned closer to the large end (22), thereby allowing the large end (22) to be cooled more reliably and effectively.

[0011] The fuel injector (30) may be configured to inject mixed fuel into the large end (22) when at least the piston (4) is at top dead center. With this configuration, since the injection of fuel is timed to the desired timing, it is easy to introduce the fuel sprayed into the large end (22) into the small hole.

[0012] A scavenging hole (14) is formed in the cylinder (2), and the inlet (14a) of the scavenging hole (14), which opens toward the crankcase (6a), may be located at the same height as the nozzle (31) of the fuel injector (30) in the axial direction. With this configuration, it is easy to introduce fuel sprayed into the large end (22) into the scavenging hole (14). Since the mixed fuel remains near the inlet (14a) of the scavenging hole (14), fuel is easily introduced into the scavenging hole (14). As a result, the amount of wasted fuel not introduced into the scavenging hole (14) can be reduced, and the effect of reducing fuel consumption can also be obtained. In addition, transient responsiveness and starting performance are improved. Effects of the invention

[0013] According to the present disclosure, lubrication and cooling at the large end can be performed with a small amount of mixed fuel. Brief explanation of the drawing

[0014] FIG. 1 is a longitudinal cross-sectional view of a two-cycle engine according to an embodiment of the present disclosure. Figure 2 is a cross-sectional view along line II-II of Figure 1. Figure 3 is a cross-sectional view showing the state where the piston is located at the bottom dead center. Figure 4 is a cross-sectional view along line IV-IV of Figure 1. FIG. 5(a) is an exploded perspective view showing the crank mechanism and connecting rod, and FIG. 5(b) is a side view showing the crank mechanism and connecting rod. Figure 6 is a block diagram showing a schematic configuration according to the injection control of a mixed fuel in a fuel injector. Figure 7(a) is a figure showing the injection timing of a mixed fuel in a two-cycle engine of Figure 1, and Figure 7(b) is a figure showing the injection timing of a mixed fuel in a two-cycle engine according to a modified example. Specific details for implementing the invention

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In addition, in the description of the drawings, the same reference numerals are assigned to identical elements, and redundant descriptions are omitted. In the following description, when "up and down" is used, the cylinder body (2a) is set up so that the bore portion (3) of the cylinder (2) extends in a vertical direction with the opening into which the piston (4) is inserted facing downward. "Up" corresponds to one side of the axis (L) direction of the bore portion (3), and "down" corresponds to the lower side of the axis (L) direction.

[0016] As shown in FIGS. 1, 2 and 3, the engine (2-cycle engine) (1) is a 2-cycle engine that employs a Schnuerle method as a scavenging method and is equipped, for example, in a mower or a power sprayer. The engine (1) comprises a cylinder (2), a piston (4) that reciprocates within a bore (3) inside the cylinder (2), a crankcase (6) connected to the lower end of the cylinder (2) and including a crank chamber (6a), and a crank mechanism (7) disposed in the crank chamber (6a) of the crankcase (6). A piston pin (8) provided in the piston (4) and a crank pin (9) of the crank mechanism (7) provided in the crankcase (6) are connected by a connecting rod (10). The piston (4) is disposed within the bore (3) and is capable of reciprocating along the axis (L) direction between the combustion chamber (11) and the crank chamber (6a). In the following description, the connecting rod (10) is referred to as the connecting rod (10).

[0017] In the cylinder (2), 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 port (12) and an exhaust port (13) communicating with the bore portion (3), a pair of intake-side scavenging holes (14), and a pair of exhaust-side scavenging holes (16) are formed. The cylinder (2) includes a cylinder body (2a) and a pair of scavenging cassettes (2b) fitted into the lower part of the cylinder body (2a). The pair of scavenging cassettes (2b) are fitted and fixed within two openings formed to face each other in the diameter 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).

[0018] The bore section (3) includes a cylindrical bore surface (3a) and extends along the axis (L) direction within the cylinder (2). The bore section (3) has its bottom dead center side (the lower side shown) open and is in communication with the crankcase (6a). A concave combustion chamber (11) is formed at the end of the bore section (3) on the top dead center side, and a discharge electrode, such as a spark plug (18), is placed inside the combustion chamber (11). Near the combustion chamber (11) of the cylinder body (2a), a spark plug mounting hole (19) is provided for mounting the spark plug (18).

[0019] The intake port (12) and the exhaust port (13) are each connected to the bore portion (3), and in the direction of the axis (L), the exhaust port (13) is positioned slightly closer to the top dead center than the intake port (12). The intake port (12) and the exhaust port (13) are positioned approximately 180° apart from each other in the circumferential direction of the bore portion (3) so as to face each other in the diameter direction of the bore portion (3).

[0020] The intake side scavenging port (14) is intended to introduce a fresh gas containing fuel into the bore section (3) and the combustion chamber (11) during the scavenging process, and runs along the axial direction (L) inside the side wall of the cylinder (2). The fresh gas is a fuel mixture for engine operation consisting of a mixed fuel made of gasoline and oil mixed with air. The end of the intake side scavenging port (14) on the top dead center side is connected to the bore section (3) at a position approximately similar to the exhaust port (13) in the axial direction (L). The intake side scavenging port (14) is spaced apart from each other in the main direction of the bore section (3). More specifically, the intake side scavenging port (14) is arranged approximately symmetrically with respect to the virtual line connecting the intake port (12) and the exhaust port (13) in the diameter direction. The intake side intake port (14) is provided so that the fresh gas introduced into the bore (3) is directed toward the intake port (12).

[0021] The end of the intake side scavenger port (14) on the bottom dead center side (inlet (14a) described later) is in communication with the crankcase (6a). The end of the exhaust side scavenger port (16) on the bottom dead center side (not shown) is in communication with the crankcase (6a) described above.

[0022] The exhaust side scavenging port (16) is intended to introduce EGR (Exhaust Gas Recirculation) gas, which is exhaust gas after combustion with a fuel content lower than that of the working gas, into the bore section (3) and the combustion chamber (11) during the scavenging process, and runs along the axis (L) direction inside the side wall of the cylinder (2). The end of the exhaust side scavenging port (16) on the top dead center side is connected to the bore section (3) at a position approximately similar to the exhaust port (13) in the axis (L) direction. The exhaust side scavenging port (16) is spaced apart from one another in the main direction of the bore section (3). More specifically, the exhaust side scavenging port (16) is arranged approximately symmetrically with respect to a virtual line connecting the intake port (12) and the exhaust port (13) in the diameter direction. The exhaust side scavenging port (16) is provided so that the EGR gas introduced into the bore section (3) is directed toward the intake port (12). For example, the piston (4) may be provided with a passage connecting the exhaust port (13) and the exhaust side scavenging port (16) when the piston (4) is near the top dead center, and allowing the exhaust gas after combustion to be blown from the exhaust port (13) to the exhaust side scavenging port (16) as EGR gas.

[0023] As described above, the engine (1) is a piston valve type 2-cycle engine in which the intake port (12) is opened and closed by a piston (4) that reciprocates within the bore (3). In the engine (1), among the components constituting the fresh gas, air is introduced from the intake port (12), while a mixed fuel including gasoline and oil is injected into the crankcase (6a) to cool the large end (22) of the connecting rod (10). As a result, the air and the mixed fuel are mixed within the crankcase (6a) of the crankcase (6), thereby creating the fuel mixture.

[0024] With reference to FIG. 5(a) and FIG. 5(b), the configuration of the crank mechanism (7) and the connecting rod (10) will be described. As shown in FIG. 5(a), the crank mechanism (7) includes a crank shaft (7a), a pair of crank webs (7b) connected to the crank shaft (7a), and a pair of connecting parts (7c) provided on the opposite side of the crank webs (7b) in the radial direction. The connecting rod (10) includes a small end (21) which is rotatably connected to a piston (4) through a piston pin (8) by inserting a piston pin (8) into a pin insertion hole (21a), a large end (22) which is rotatably connected to a connecting part (7c) of a crank mechanism (7) through a crank pin (9) by inserting a crank pin (9) into a pin insertion hole (22a), and a rod body (23) connecting the small end (21) and the large end (22).

[0025] The crank web (7b), connecting part (7c), and crank shaft (7a) are formed as a single unit. A crank pin (9) inserted into a pair of connecting parts (7c) is joined and fixed to these connecting parts (7c), and the entire crank mechanism (7) forms a rigid body. A pair of crank webs (7b) form a fan shape centered on the crank shaft (7a), are guided by the cylindrical wall of the crank chamber (6a), and rotate around the crank shaft (7a). When the connecting rod (10) moves up and down in conjunction with the reciprocating motion of the piston (4), the large end (22) of the connecting rod (10) moves (rotates) along a circumferential track together with the crank pin (9) and connecting part (7c), and the reciprocating motion of the piston (4) is converted into the rotational motion of the crank shaft (7a).

[0026] As shown in FIG. 5(b), a pair of crank webs (7b) are arranged in parallel to each other and are spaced apart in the axial direction of the crank shaft (7a). A gap (G) is formed between the pair of crank webs (7b). During the rotation of the crank mechanism (7), the gap (G) between the large end (22) of the connecting rod (10) and the crank web (7b) is always located on opposite sides in the radial direction. The circumferential trajectory of the large end (22) and the circumferential trajectory of the gap (G) are superimposed.

[0027] As shown in FIG. 1, the engine (1) is equipped with a fuel injection nozzle (fuel injector) (30) that sprays mixed fuel toward the large end (22) of the connecting rod (10). The fuel injection nozzle (30) is mounted on the upper part of the crankcase (6) near the connection position with the cylinder body (2a). The tip portion of the fuel injection nozzle (30), which includes an injection port (31) into which the mixed fuel is injected, is fitted from the outside to the inside of the crankcase (6). The injection port (31) of the fuel injection nozzle (30) is oriented in a direction that intersects, for example, the axis (L) direction of the bore portion (3) and the axis direction of the crankshaft (7a). More specifically, the injection port (31) of the fuel injection nozzle (30) is oriented in a direction that is orthogonal to both the axis (L) direction of the bore portion (3) and the axis direction of the crankshaft (7a).

[0028] FIG. 4 is a cross-sectional view along line IV-IV of FIG. 1. As shown in FIG. 4, the fuel injection nozzle (30) is positioned in a planar view facing the diameter direction of the bore portion (3) (bore surface (3a)). The injection port (31) of the fuel injection nozzle (30) protrudes slightly into the crankcase (6a). The injection port (31) is positioned to pass through the gap (G) (see FIG. 5 (b)) between a pair of crank webs (7b) during the rotation of the crank mechanism (7). In this way, the injection port (31) faces the gap (G), so there is no other member between the injection port (31) and the pin insertion hole (22a).

[0029] Also, as shown in FIGS. 1 and 4, the inlet (14a) of a pair of intake-side scavenging holes (14) is located near the side of the nozzle (31). The pair of inlets (14a) are open toward the crankcase (6a). Additionally, the pair of inlets (14a) are also connected to a pair of exhaust-side scavenging holes (16). The distance along the main direction between the nozzle (31) and the inlet (14a) is shorter than one-fourth of the length of the main surface of the bore surface (3a) (the inner surface of the bore section (3)). That is, the nozzle (31) and one intake-side scavenging hole (14) are arranged within a range of 90° from the center angle with respect to the axis (L) of the bore section (3). A nozzle (31) and an intake side scavenging port (14) on the other side are arranged within a range of 90° from the center angle with respect to the axis (L) of the bore section (3). The inlet (14a) of the intake side scavenging port (14) is located at the same height as the nozzle (31) of the fuel injection nozzle (30) in the direction of the axis (L). In other words, the nozzle (31) of the fuel injection nozzle (30) is located at a height position at the top of the crankcase (6).

[0030] As shown in FIG. 1 and FIG. 7 (a), the fuel injection nozzle (30) injects mixed fuel in a tangential direction of the circumferential orbit of the large end (22). The period during which mixed fuel is injected from the fuel injection nozzle (30) includes, at least, when the piston (4) is at top dead center (at which time the large end (22) of the pin is also at its highest point). The injection of mixed fuel from the fuel injection nozzle (30) may continue, for example, until 30° after top dead center. In other words, the period during which mixed fuel is injected from the fuel injection nozzle (30) may begin when the piston (4) is at top dead center (at 0°) or slightly ahead of it (a few° to about 15° ahead), and may end at 30° after top dead center. The fuel injection nozzle (30) is configured to spray mixed fuel onto the large end (22) of the connecting rod (10). The fuel injection nozzle (30) injects mixed fuel while the large portion (22) passes in front of the injection port (31).

[0031] The injection timing of the mixed fuel at the fuel injection nozzle (30) is controlled by an ECU (40) that controls the engine (1), as shown in FIG. 6. The ECU (40) controls the valve (50) that opens and closes the intake path to the intake port (12) and the fuel injection nozzle (30) based on throttle opening information input from the throttle sensor (S1) and rotation angle information of the crank mechanism (7) input from the angle sensor (S2). The above injection timing (injection period) can be appropriately adjusted by the ECU (40) based on the state of the engine (1). The fuel injection nozzle (30) is an electronically controlled injector and can adjust the injection amount of the mixed fuel with high precision. For example, even when the required mixed fuel (amount of gasoline) is minimal, the ECU (40) injects a mixed fuel equivalent to a controllable limit value (minimum amount) from the fuel injection nozzle (30). In this embodiment, the fuel injection nozzle (30) is configured to spray mixed fuel onto the large end (22) when at least the piston (4) is at the top dead center. Also, in FIG. 6, the line (path) of the mixed fuel connected to the fuel injection nozzle (30) is omitted.

[0032] The mixed fuel injected from the injection port (31) may be radial or linear. The type of nozzle may be appropriately selected. The injection direction (the direction of the injection center axis) of the fuel injection nozzle (30) intersects the axis (L) and crosses the bore portion (3) in a planar view. The injection center axis direction of the fuel injection nozzle (30) is, for example, perpendicular to the axis (L). The injection center axis direction of the fuel injection nozzle (30) is, for example, perpendicular to the axial direction of the crankshaft (7a).

[0033] Next, the operation of the engine (1) is described. First, as the piston (4) rises from the bottom dead center toward the top dead center, the intake side scavenger port (14), the exhaust side scavenger port (16), and the exhaust port (13) are closed by the piston (4), and the fresh gas in the combustion chamber (11) is compressed. With the further rise of the piston (4), the intake port (12) communicates with the crankcase (6a) through the bore (3), and air is introduced into the crankcase (6a) (see FIGS. 1 and 2).

[0034] When the piston (4) reaches near the top dead center, the mixture explodes in the combustion chamber (11), and the piston (4) descends toward the bottom dead center. Meanwhile, within the crankcase (6a), when the piston (4) is located near the top dead center, the mixed fuel is injected from the fuel injection nozzle (30) under the control of the ECU (40). The mixed fuel is sprayed onto the large end (22) of the connecting rod (10), thereby lubricating and cooling the large end (22). The injection of the mixed fuel is stopped immediately after the piston (4) begins to descend (at the latest by the point 30° after the top dead center mentioned above). Air and the mixed fuel are mixed within the crankcase (6a), and fresh gas is generated.

[0035] When the piston (4) descends further, the exhaust port (13) opens and the combustion gas is exhausted (see FIG. 3). Then, slightly later than the opening of the exhaust port (13), the intake side scavenging port (14) and the exhaust side scavenging port (16) are exposed into the bore section (3), and the scavenging stroke begins. The injection of the mixed fuel is close to the timing of the start of the scavenging process. Also, the distance from the injection port (31) to the inlet (14a) of the intake side scavenging port (14) is short. The mixed fuel (fresh gas) is introduced into the intake side scavenging port (14) reliably and easily. Throughout the scavenging process, the exhaust side scavenging port (16) is filled with EGR gas, and the intake side scavenging port (14) is filled with fresh gas.

[0036] When the intake side scavenging port (14) opens into the bore section (3), the introduction of fresh gas from the intake side scavenging port (14) into the bore section (3) begins. As the piston (4) descends, fresh gas flows from the intake side scavenging port (14) into the bore section (3). At the same time, the exhaust side scavenging port (16) opens, and the EGR gas and fresh gas flow in this order from the exhaust side scavenging port (16). As a result, layered scavenging is performed.

[0037] During the process in which the piston (4) reaches the bottom dead center, a pair of crank webs (7b) of the crank mechanism (7) pass near the fuel injection nozzle (30), but the injection port (31) passes through the gap (G) between the pair of crank webs (7b), so they do not interfere.

[0038] According to the engine (1) of the present embodiment, a fuel injection nozzle (30) mounted on the crankcase (6) sprays a mixed fuel onto the large end (22) of the connecting rod (10). At this time, the fuel injection nozzle (30) sprays the mixed fuel in a tangential direction toward the circumferential track of the large end (22). The oil contained in the mixed fuel lubricates and cools the large end (22). Additionally, the gasoline contained in the mixed fuel also cools the large end (22). As a result, lubrication and cooling of the large end (22) can be performed with a small amount of mixed fuel. Furthermore, since the mixed fuel is injected into the crankcase (6) rather than into the combustion chamber (11) or bore (3), there is no need to consider pressure resistance and heat resistance regarding the surrounding configuration of the fuel injection nozzle (30).

[0039] The injection port (31) of the fuel injection nozzle (30) protrudes into the crankcase (6a). As a result, since the mixed fuel can be injected from a position closer to the large end (22), it becomes easier to obtain the desired lubrication and cooling effects mentioned above.

[0040] The injection port (31) of the fuel injection nozzle (30) is positioned to pass through the gap (G) between a pair of crank webs (7b). This allows the injection port (31) to be positioned closer to the large end (22), thereby enabling the large end to be cooled more effectively and reliably.

[0041] The fuel injection nozzle (30) is configured to inject mixed fuel into the large end (22) when at least the piston (4) is at top dead center. As a result, since the fuel injection is synchronized with the desired timing, it is easy to introduce the fuel sprayed into the large end (22) into the intake side scavenging port (14).

[0042] The inlet (14a) of the intake side scavenging port (14) is located at the same height as the injection port (31) of the fuel injection nozzle (30) in the direction of the axis (L). As a result, it is easy to introduce the fuel sprayed into the large end (22) into the intake side scavenging port (14). Since the mixed fuel remains near the inlet (14a) of the intake side scavenging port (14), the fuel is easily introduced into the intake side scavenging port (14). As a result, the amount of wasted fuel not introduced into the intake side scavenging port (14) can be reduced, and the effect of reducing fuel consumption can also be obtained. In addition, transient responsiveness and starting performance are improved.

[0043] Although embodiments of the present disclosure have been described above, the present invention is not limited to the above embodiments. For example, the fuel injection nozzle (30) is not limited to a configuration in which the mixed fuel is injected into the large end (22) when at least the piston (4) is at top dead center. For example, as shown in FIG. 7 (b), the fuel injection nozzle (30) may inject the mixed fuel into the large end (22) of the connecting rod (10) while the piston (4) is moving toward top dead center. The fuel injection nozzle (30) may be mounted, for example, on the lower part of the crankcase (6) to inject the mixed fuel in the tangential direction of the circumferential track of the large end (22). The injection port (31) may be directed upward.

[0044] The cylinder (2) is not limited to a configuration in which four scavenging holes, a pair of intake-side scavenging holes (14) and a pair of exhaust-side scavenging holes (16), are provided, and may be configured to have one intake-side scavenging hole (14) and one exhaust-side scavenging hole (16). It is not limited to a configuration in which the intake-side scavenging hole (14) introduces fresh gas and the exhaust-side scavenging hole (16) introduces EGR gas. The present invention can also be applied to a layered scavenging engine of the air-using type. In addition, only a pair of scavenging holes facing each other in the diameter direction may be provided between the intake port (12) and the exhaust port (13). Only one scavenging hole may be provided for the cylinder (2). Explanation of the symbols

[0045] 1: Engine (2-cycle engine) 2: Cylinder 3: Boeobu 4: Piston 6: Crankcase 6a: Crankroom 7: Crank mechanism 7a: Crankshaft 7b: Crank Web 9: Crank pin 11: Combustion chamber 12: Air intake 13: Exhaust pipe 14: Intake side scavenger (scavenger) 16: Exhaust side scavenger (scavenger) 21: Small section 22: The Great Division 30: Fuel injection nozzle (fuel injector) 31: Nozzle G: Gap L: Axis (of the bore)

Claims

Claim 1 A two-cycle engine (1) of a piston valve type having a cylinder (2) and a piston (4) that reciprocates along an axial direction within a bore (3) of the cylinder (2), wherein an intake port is opened and closed by the piston (4); a crankcase (6) connected to the cylinder (2) and including a crankcase (6a); a crank mechanism (7) disposed in the crankcase (6a) and rotating around a crankshaft (7a); a connecting rod including a small end (21) connected to the piston (4) and a large end (22) connected to the crank mechanism (7); and a fuel injector (30) mounted on the crankcase (6) and spraying the mixed fuel toward the tangential direction of a circumferential track of the large end (22) to spray the mixed fuel onto the large end (22), wherein the fuel injector (30) is mounted near the connection position with the cylinder (2) in the crankcase (6), and the fuel The nozzle (31) of the injector (30) is a two-cycle engine that protrudes toward the inside of the crankcase (6a) more than the bore surface (3a) of the bore part (3) when viewed from the axial direction of the bore part (3). Claim 2 In claim 1, the crank mechanism (7) comprises a pair of crank webs (7b) connected to the crank shaft (7a) and spaced apart in the axial direction of the crank shaft (7a), and the nozzle (31) of the fuel injector (30) is positioned to pass through the gap (G) between the pair of crank webs (7b), in a two-cycle engine. Claim 3 A two-cycle engine according to claim 1 or 2, wherein the fuel injector (30) is configured to spray the mixed fuel onto the large end (22) when at least the piston (4) is at top dead center. Claim 4 A two-cycle engine according to claim 1 or 2, wherein a scavenging hole (14) is formed in the cylinder (2), and the inlet (14a) of the scavenging hole (14), which opens toward the crankcase (6a), is located at the same height as the nozzle (31) of the fuel injector (30) in the axial direction. Claim 5 delete

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