Engine

Abstract

Provided is an air-cooled engine that has increased cooling efficiency.　An engine 10 has an engine block 11, a valve positioning hole 21, a plug positioning hole 23, and a vent hole 30. The engine block 11 has a cylinder bore 12 formed therein. The valve positioning hole 21 connects to a side surface of the cylinder bore 12, and has a valve 25 positioned therein. The plug positioning hole 23 connects to the side surface of the cylinder bore 12, and has a spark plug 22 positioned therein. The vent hole 30 penetrates through the engine block 11 in the vicinity of the valve positioning hole 21 or the plug positioning hole 23.

Description

Engine

[0009] , ,

[0010]

[0001] The present invention relates to an engine, and more particularly to an air-cooled engine.

[0002] Engines can be broadly classified into air-cooled engines and water-cooled engines. An air-cooled engine prevents overheating of the engine by transmitting the heat generated from the engine during operation to the outside through air. On the other hand, a water-cooled engine prevents overheating of the engine by absorbing the operating heat of the engine with water and radiating the water after heat absorption to the atmosphere by a radiator.

[0003] In recent years, water-cooled engines are more frequently used because they can cool the engine more effectively than air-cooled engines.

[0004] On the other hand, in a flying device also called a drone, an air-cooled engine may be adopted as a driving source. A drone equipped with an air-cooled engine is described in, for example, Patent Document 1.

[0005] Japanese Unexamined Patent Application Publication No. 2021-167198

[0006] However, in the above-described engine, there is room for improvement from the viewpoints of the configuration of the entire engine and the application fields specific to it. <000^013>

[0007] In an air-cooled engine, there is a problem from the viewpoint of heat dissipation of the engine because the specific heat of air as a heat medium is small. On the other hand, a water-cooled engine requires a radiator, connecting pipes, a pump, cooling water, etc., and thus there is a problem that the entire water-cooled engine becomes large and heavy.

[0008] In particular, when an engine is adopted in a flying device such as a drone, since the weight limit of the drone is strict, it is considered that problems such as enlargement become prominent when a water-cooled engine is adopted as the engine.

[0009] The present invention has been made in view of such problems, and an object of the present invention is to provide a compact and highly efficient air-cooled engine.

[0010] An engine according to an embodiment of the present invention is characterized by comprising: an engine block having a cylinder bore formed inside it; a valve mounting hole connected to the side surface of the cylinder bore and having a valve arranged inside it; a plug mounting hole connected to the side surface of the cylinder bore and having a spark plug arranged inside it; and a ventilation hole penetrating the engine block near the valve mounting hole or the plug mounting hole.

[0011] According to the engine of the present invention, outside air circulates through the vent holes inside the engine block, effectively dissipating heat generated near the combustion chamber to the outside, thereby improving the engine's cooling efficiency. Therefore, it is possible to provide a compact air-cooled engine with enhanced cooling efficiency.

[0012] This is a perspective view showing an engine according to the first embodiment of the present invention. This is a perspective view showing the engine according to the first embodiment of the present invention from a different angle. This is an exploded perspective view showing the engine block of the engine according to the first embodiment of the present invention. This is an exploded perspective view showing the engine block of the engine according to the first embodiment of the present invention from a different angle. This is a cross-sectional view showing the internal configuration of the engine according to the first embodiment of the present invention. This is a side view showing the internal configuration of the engine according to the first embodiment of the present invention. This is a perspective view showing the internal configuration of the engine according to the first embodiment of the present invention. This is a perspective view showing the second engine block of the engine according to the first embodiment of the present invention. This is a side view showing the second engine block of the engine according to the first embodiment of the present invention. This is a cutaway perspective view showing the first valve vent of the engine according to the first embodiment of the present invention. This is a perspective view showing the first engine block of the engine according to the first embodiment of the present invention. This is an exploded perspective view showing the first engine block of the engine according to the first embodiment of the present invention. This is a perspective view showing the engine according to the first embodiment of the present invention. This is an exploded perspective view showing the engine according to the first embodiment of the present invention. This is an exploded perspective view showing the air guide section of the engine according to the first embodiment of the present invention from a different angle. This is a perspective view showing an aircraft equipped with the engine according to the first embodiment of the present invention. This is a plan view showing an aircraft equipped with the engine according to the first embodiment of the present invention. This is a side view showing an aircraft equipped with the engine according to the first embodiment of the present invention. This is a perspective view showing an engine according to another embodiment of the present invention. This is a perspective view showing an engine according to another embodiment of the present invention in part. This is a cross-sectional perspective view showing an engine according to another embodiment of the present invention. This is a front perspective view of the engine and fan cover, etc., according to the second embodiment of the present invention. This is a rear perspective view of the engine and fan cover, etc., according to the second embodiment of the present invention. This is a front view of the engine and fan cover, etc., according to the second embodiment of the present invention. This is a rear view of the engine and fan cover, etc., according to the second embodiment of the present invention. This is a bottom view of the engine and fan cover, etc., according to the second embodiment of the present invention. This is a left side view of the engine and fan cover, etc., according to the second embodiment of the present invention. This is a front perspective view of the engine according to the second embodiment of the present invention.This is a rearward perspective view of the engine according to the second embodiment of the present invention. This is a front view of the engine according to the second embodiment of the present invention. This is a rear view of the engine according to the second embodiment of the present invention. This is a bottom view of the engine according to the second embodiment of the present invention. This is a left side view of the engine according to the second embodiment of the present invention. This is a diagram showing the second engine block of the engine according to the second embodiment of the present invention, with a front view shown in the upper left portion, a rear view shown in the upper right portion, and a cutaway perspective view shown in the lower portion. This is a frontward perspective view of the first engine block of the engine according to the second embodiment of the present invention. This is a front view showing the first engine block of the engine according to the second embodiment of the present invention. This is a diagram showing the engine and fan cover, etc., according to the second embodiment of the present invention, with an exploded perspective view showing the fan cover and blower fan, etc., disassembled from the front. This is a diagram showing the engine and fan cover, etc., according to the second embodiment of the present invention, with an exploded perspective view showing the fan cover and blower fan, etc., disassembled from the rear. This is a diagram showing the second embodiment of the present invention, with a frontward perspective view of the front fan cover. This is a diagram showing the second embodiment of the present invention, with a rearward perspective view of the front fan cover. This is a diagram showing the second embodiment of the present invention, with a rearward perspective view of the rear fan cover. This is a front view of the engine and cover member according to a second embodiment of the present invention. This is a rear view of the engine and cover member according to a second embodiment of the present invention. This is a diagram showing a second embodiment of the present invention, a perspective view of the cover member covering the central part of the engine block, viewed from the front. This is a diagram showing a second embodiment of the present invention, a perspective view of the cover member covering the central part of the engine block, viewed from the rear. This is a diagram showing a second embodiment of the present invention, a front view of the cover member covering the central part of the engine block. This is a diagram showing a second embodiment of the present invention, a rear view of the cover member covering the central part of the engine block.

[0013] [First Embodiment] Hereinafter, an engine 10 according to the first embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the front-rear direction is the direction in which the first crankshaft 143 and the second crankshaft 153, which will be described later, extend. The front-rear direction is also the direction in which air flows to cool the engine 10. The left-right direction is the direction perpendicular to the front-rear direction and is the direction in which the first piston 141 and the second piston 151, which will be described later, reciprocate. In the following description, the same reference numerals are used for the same components in principle, and repeated explanations are omitted. Furthermore, in this embodiment, the configuration described in the claims will be mainly illustrated and described. Therefore, parts of the engine 10 other than the said configuration, such as the lubrication oil supply mechanism, fuel supply mechanism, and various electrical components, are not shown, but these are provided in the engine 10.

[0014] Furthermore, in the following description, members indicating predetermined spaces such as the cylinder bore 12 and valve mounting holes 21 may also include parts of the engine block 11 and other components that constitute the thickness portion that demarcates the cylinder bore 12, valve mounting holes 21, etc.

[0015] Figure 1 is a perspective view showing engine 10. Figure 2 is a perspective view showing engine 10 from a different angle.

[0016] Referring to Figures 1 and 2, engine 10 is an opposed-piston type engine having multiple pistons arranged opposite each other. The internal configuration and operation of engine 10 will be described later with reference to Figures 3 and onward.

[0017] Engine 10 is configured to operate using gasoline, diesel fuel, hydrogen, etc. Engine 10 can be used as a power source for various devices. Engine 10 can be used as a power source for vehicles, generators, water heaters, flying devices, drones, series hybrid drones, parallel hybrid drones, etc. A series hybrid drone is a drone in which engine 10 drives a generator, the electricity generated from the generator rotates a motor, the motor rotates a rotor, and the lift generated by the rotation of the rotor makes the drone float in the air. A parallel hybrid drone is a drone in which engine 10 mechanically rotates a main rotor, and the lift generated by the rotation of the main rotor makes the drone float. In addition, a parallel hybrid drone has a sub-rotor that rotates with a motor to control the attitude of the drone, separate from the main rotor which is mechanically driven by engine 10. The engine 10 of this embodiment is an opposed-piston type engine, and because it is lightweight and has low vibration, it is suitable as a power source for series hybrid drones, parallel hybrid drones, etc.

[0018] In this embodiment, the engine 10 mainly comprises an engine block 11, a valve mounting hole 21 (see Figure 7A), a spark plug mounting hole 23 (see Figure 9B), and a ventilation hole 30 (see Figure 1). As shown in Figure 5, the engine block 11 has a cylinder bore 12 inside. As shown in Figure 7A, the valve mounting hole 21 is connected to the side of the cylinder bore 12, and a valve 25 (Figure 6A) is arranged inside it. As shown in Figure 9B, the spark plug mounting hole 23 is connected to the side of the cylinder bore 12, and a spark plug 22 is arranged inside it. As shown in Figures 7A to 9A, the ventilation hole 30 is an air tunnel that penetrates the engine block 11 near the valve mounting hole 21 or the spark plug mounting hole 23. According to the engine 10 of this embodiment, the portion of the engine block 11 where the valve mounting hole 21 or the spark plug mounting hole 23 is formed can be cooled particularly actively.

[0019] Specifically, the engine 10 has an engine block 11, which is the main body. The engine block 11 is made of, for example, a cast aluminum alloy. As will be described later, the engine block 11 is made up of multiple engine blocks. These parts are fastened together by fastening members, for example, bolts.

[0020] The first crankshaft 143 and the second crankshaft 153 are routed out from the front side of the engine block 11. Rotational driving force can be extracted to the outside from the first crankshaft 143 and the second crankshaft 153. Also, as shown in Figure 2, the first crankshaft 143 and the camshaft 27 are routed out from the rear side of the engine block 11 toward the rear. The first crankshaft 143 and the second crankshaft 153 are equipped with a reversing synchronous mechanism consisting of gears and belts. This reversing synchronous mechanism reverses the rotation of the second crankshaft 153 relative to the first crankshaft 143 and equalizes the rotational speeds of the first crankshaft 143 and the second crankshaft 153. In addition, the rotational driving force of the camshaft 27 controls the reciprocating motion of the valve 25, which will be described later. The engine 10 is equipped with a gear train (not shown) that reverses the rotation of the camshaft 27 relative to the second crankshaft 153 and reduces its rotational speed to half.

[0021] The engine 10 is a so-called air-cooled engine that uses air for cooling during operation. The engine 10 has a number of fins 115 to increase its surface area in order to promote cooling by air. The fins 115 extend along the front-rear direction, which is parallel to the direction in which the cooling air flows. The fins 115 are formed on the upper, lower, front, and rear surfaces of the engine block 11.

[0022] The engine 10 has ventilation holes 30 to further improve the cooling efficiency by air cooling. As shown in Figures 1 and 2, the ventilation holes 30 have a fourth opening 396 in the main body and a plug ventilation hole 34. Furthermore, the fourth opening 396 in the main body has a first valve ventilation hole 32 and a second valve ventilation hole 33. The first valve ventilation hole 32 and the second valve ventilation hole 33 are separate ventilation holes that do not communicate with each other. The fourth opening 396 in the main body and the plug ventilation hole 34 form an air passage that penetrates the engine block 11 along the front-rear direction. When the engine 10 is in operation, air passes through the inside of the fourth opening 396 in the main body and the plug ventilation hole 34 at high speed, allowing the air to absorb the operating heat generated during the operation of the engine 10, thereby preventing the engine 10 from overheating. Each part constituting the ventilation holes 30 will be described later with reference to Figures 7A and later.

[0023] Figure 3 is an exploded perspective view showing the engine block 11 of engine 10. Figure 4 is an exploded perspective view showing the engine block 11 of engine 10 from a different angle.

[0024] Referring to Figures 3 and 4, the engine block 11 has, from right to left, a third engine block 113, a first engine block 111, a second engine block 112, and a fourth engine block 114. The first to fourth engine blocks 111 to 114 are fastened together by fastening members, such as bolts.

[0025] The first engine block 111 has a first cylinder bore 121 formed inside it, which is part of the cylinder bore 12. As shown in Figure 3, a first extension forming surface 171 is formed from the upper end of the first cylinder bore 121. The first extension forming surface 171 is a wall-like portion that constitutes the extension space 24, which will be described later. The plug vent hole 34 is configured to penetrate the first engine block 111 along the front-rear direction.

[0026] Referring to Figure 4, the second engine block 112 has a second cylinder bore 122 formed inside it, which is part of the cylinder bore 12. A second extension forming surface 172 is formed from the upper end of the second cylinder bore 122. The second extension forming surface 172 is a wall-like portion that constitutes an extension space 24, which will be described later. The first valve vent hole 32 and the second valve vent hole 33 are formed to penetrate the second engine block 112 in the front-rear direction.

[0027] The detailed configurations of the first engine block 111 and the second engine block 112 will be described later with reference to Figures 7A and later.

[0028] The third engine block 113 houses the first crankshaft 143, which will be described later. The first crankshaft 143 is held in a rotatable state by a semicircular crankshaft holder 164 formed on the left side of the third engine block 113 and a semicircular crankshaft holder 163 formed on the right side of the first engine block 111. A bearing is also provided between the two.

[0029] The fourth engine block 114 houses the second crankshaft 153, which will be described later. The second crankshaft 153 is held in a rotatable state by a semicircular crankshaft holder 161 formed on the right side of the fourth engine block 114 and a semicircular crankshaft holder 162 formed on the left side of the second engine block 112. A bearing is also provided between the two.

[0030] Figure 5 is a cross-sectional view along the A-A line in Figure 1, showing the wall portion of the engine block 11 that forms the cylinder bore 12 and extension space 24. The A-A line is a cross-section that includes both the vertical and horizontal directions.

[0031] The cylinder bore 12 is a space that is substantially cylindrical in shape. The cylinder bore 12 has a first cylinder bore 121 on the right side and a second cylinder bore 122 connected to the left end of the first cylinder bore 121. Approximately in the center of the cylinder bore 12 in the front-rear direction, an extension space 24 protrudes upward from the upper surface of the cylinder bore 12. The first cylinder bore 121, the second cylinder bore 122, and the extension space 24 are in communication. As will be described later, the extension space 24 is the space in which the tip of the valve 25 and the spark plug 22 are arranged. Therefore, intake, exhaust, and ignition are performed through the extension space 24.

[0032] The cylinder bore 12 and extension space 24 in this configuration are spaces surrounded by walls formed inside the engine block 11.

[0033] Specifically, the first cylinder bore 121 is a substantially cylindrical space surrounded by the first cylinder wall 181. The first cylinder wall 181 is a cylindrical wall formed inside the first engine block 111. The right and left ends of the first cylinder wall 181 are open.

[0034] The second cylinder bore 122 is a substantially cylindrical space surrounded by the second cylinder wall 191. The second cylinder wall 191 is a cylindrical wall formed inside the second engine block 112. The right and left ends of the second cylinder wall 191 are open.

[0035] The extension space 24 is the space enclosed by the first extension wall portion 182 and the second extension wall portion 192. The first extension wall portion 182 is a roughly tongue-shaped portion that extends upward from the upper end of the first cylinder wall portion 181 at the right end of the first cylinder wall portion 181. The second extension wall portion 192 is a roughly tongue-shaped portion that extends upward from the upper end of the second cylinder wall portion 191 at the left end of the second cylinder wall portion 191.

[0036] The cylinder bore 12 is a substantially cylindrical space having a central axis 20 extending along the left-right direction. The cylinder bore 12 has an inner surface 28. The inner surface 28 is a surface formed by the inner surfaces of the first cylinder wall portion 181 and the second cylinder wall portion 191. An extension space 24 extends from the inner surface 28. Specifically, the extension space 24 is a space that extends upward in a direction perpendicular to the central axis 20 of the cylinder bore 12. The extension space 24 communicates with the cylinder bore 12.

[0037] The engine 10 includes a first engine section 14 and a second engine section 15.

[0038] The first engine section 14 includes a first piston 141, a first connecting rod 142, and a first crankshaft 143. The first connecting rod 142 rotatably connects the first piston 141 and the first crankshaft 143.

[0039] The second engine section 15 is positioned opposite the first engine section 14. The second engine section 15 includes a second piston 151, a second connecting rod 152, and a second crankshaft 153. The second connecting rod 152 rotatably connects the second piston 151 and the second crankshaft 153.

[0040] The first engine part 14 and the second engine part 15 of the engine 10 configured as described above operate as follows. First, in the intake stroke, the first piston 141 and the second piston 151 move outward from the central part inside the cylinder bore 12, whereby an air-fuel mixture is introduced into the cylinder bore 12. The air-fuel mixture is introduced via the extension space 24. Next, in the compression stroke, due to the inertia of the rotating first crankshaft 143 and second crankshaft 153, the first piston 141 and the second piston 151 are pushed toward the central part, and the air-fuel mixture is compressed inside the cylinder bore 12. Next, in the combustion stroke, the air-fuel mixture burns inside the cylinder bore 12 when a spark plug, which will be described later, ignites in the extension space 24. As a result, the first piston 141 and the second piston 151 are pushed to the outer end, which is the bottom dead center. Thereafter, in the exhaust stroke, due to the inertia of the rotating first crankshaft 143 and second crankshaft 153, the first piston 141 and the second piston 151 are pushed inward, and the post-combustion gas present inside the cylinder bore 12 is discharged to the outside via the extension space 24.

[0041] FIG. 6A is a side view showing the internal configuration of the engine 10. FIG. 6B is a perspective view showing the internal configuration of the engine 10.

[0042] As shown in FIGS. 6A and 6B, the valve 25 is provided so as to be able to advance and retreat with respect to the extension space 24 from the left side.

[0043] Here, two valves 25 are provided, which include an intake valve 251 and an exhaust valve 252.

[0044] The intake valve 251 is disposed in an intake valve arrangement hole 211, which will be described later with reference to FIG. 7A and the like. The exhaust valve 252 is disposed in an exhaust valve arrangement hole 212, which will be described later with reference to FIG. 7A and the like. The intake valve 25 and the exhaust valve 25 are each biased toward the left by a spring (not shown).

[0045] As a mechanism for advancing and retreating each valve 25, a camshaft 27, an intake cam 261, and an exhaust cam 262 are disposed.

[0046] The camshaft 27 is a steel bar extending along the front-rear direction. An intake cam 261 and an exhaust cam 262 are provided on the camshaft 27 in a non-rotatable relative manner.

[0047] The intake cam 261 is disposed in the immediate vicinity of the left-side end portion of the intake valve 251 and is configured to move the intake valve 251 forward and backward. When the intake cam 261 pushes the intake valve 251 toward the right, a gap is formed between the intake valve arrangement hole 211 shown in FIG. 7A and the intake cam 261, and the air-fuel mixture is supplied to the extension space 24 and the cylinder bore 12 through this gap.

[0048] The exhaust cam 262 is disposed in the immediate vicinity of the left-side end portion of the exhaust valve 252 and is configured to move the exhaust valve 252 forward and backward. The exhaust cam 262 is disposed with a predetermined phase difference with respect to the intake cam 261 around the axis of the camshaft 27. When the exhaust cam 262 pushes the exhaust valve 252 toward the right, a gap is formed between the exhaust valve arrangement hole 212 shown in FIG. 7A and the exhaust cam 262, and the post-combustion gas is discharged from the extension space 24 and the cylinder bore 12 to the outside through this gap.

[0049] When no pressing force is applied, the intake valve 251 and the exhaust valve 252 close the extension space 24 by the biasing force of a spring (not shown). That is, the intake valve 251 closes the extension space 24 by the biasing force of a spring (not shown) while not being pushed by the intake cam 261. The exhaust valve 252 closes the extension space 24 by the biasing force of a spring (not shown) while not being pushed by the exhaust cam 262.

[0050] The spark plug 22 is disposed on the right side of the extension space 24. The tip of the spark plug 22 is disposed inside the extension space 24. Further, the tip portion of the spark plug 22 is inserted into a plug arrangement hole 23, which will be described later with reference to FIG. 9B.

[0051] FIG. 7A is a perspective view showing the second engine block 112 of the engine 10. FIG. 7B is a side view showing the second engine block 112 of the engine 10.

[0052] As described above, intake valve mounting holes 211 and exhaust valve mounting holes 212 are formed in the second engine block 112. The intake valve mounting hole 211 is a space that communicates from the front side of the upper surface of the second engine block 112 to the front side of the second extension forming surface 172. The exhaust valve mounting hole 212 is a space that communicates from the rear side of the upper surface of the second engine block 112 to the rear side of the second extension forming surface 172.

[0053] As described above, the second engine block 112 has a first valve vent 32 and a second valve vent 33. The first valve vent 32 and the second valve vent 33 are air passages that penetrate the space between the second cylinder bore 122 and the outer skin of the engine block 11, i.e., the thick portion, along the front-rear direction. Referring to Figure 7A, the upper portion of the right end of the second engine block 112 has an inner wall portion 1121 and an outer wall portion 1122. The inner wall portion 1121 is a wall in which the second cylinder bore 122 and the second extension forming surface 172 are formed. The outer wall portion 1122 is a surface disposed outside the inner wall portion 1121 and forming a decorative surface. A part of the second valve vent 33 is formed between the inner wall portion 1121 and the outer wall portion 1122.

[0054] Referring to Figure 7B, the second valve vent hole 33 is formed in the engine block 11 between the valve mounting hole 21 and the outer surface of the engine block 11. In other words, the intake valve mounting hole 211 and the exhaust valve mounting hole 212 are separated by an inner wall portion 1121, and the second valve vent hole 33 is formed outside the inner wall portion 1121. Specifically, the second valve vent hole 33 has a second front opening 331, a second internal passage 332, and a second rear opening 333 from the front side. When the engine 10 is running, air flows in the order of the second front opening 331, the second internal passage 332, and the second rear opening 333.

[0055] The second front opening 331 is the front end of the second valve vent hole 33 and is a substantially circular opening formed on the front surface of the outer wall portion 1122.

[0056] The second internal passage 332 is located in the middle of the second valve vent hole 33 and is a cavity formed between the inner wall portion 1121 and the outer wall portion 1122. The second internal passage 332 is formed to enclose the inner wall portion 1121, which forms the second extension forming surface 172, from the outside. The second internal passage 332 is formed continuously from the front end to the rear end of the second engine block 112. In other words, the second internal passage 332 is a cooling passage for cooling the intake valve mounting hole 211 and the exhaust valve mounting hole 212 from the outside. In particular, the exhaust valve mounting hole 212 is a path through which high-temperature exhaust gas after combustion flows. Therefore, by forming the second internal passage 332 near the exhaust valve mounting hole 212, overheating of the exhaust valve mounting hole 212 and its vicinity can be suppressed. In the second internal passage 332, the air flowing through the second internal passage 332 receives heat via the inner wall portion 1121. Here, the heat generated from the intake valve mounting hole 211 and the exhaust valve mounting hole 212 is conducted to the air flowing through the second internal passage 332.

[0057] The second rear opening 333 is a portion that protrudes from the outer wall portion 1122 in a roughly cylindrical shape toward the rear. The inside of the second rear opening 333 is connected to the second internal passage 332. The air that has cooled the second engine block 112 is discharged toward the rear through the second rear opening 333.

[0058] Referring to Figures 7A and 7B, a substantially cylindrical projection 41 can also be provided on the side surface of the second engine block 112 facing the second internal passage 332. Multiple projections 41 can also be formed. Furthermore, the projection 41 can be formed on the portion of the second engine block 112 facing the second internal passage 332, above and near the exhaust valve mounting hole 212. This increases the surface area of ​​the second engine block 112 facing the second internal passage 332 in the vicinity of the exhaust valve mounting hole 212. Therefore, during engine 10 operation, the heat generated through the exhaust valve mounting hole 212 can be efficiently dissipated within the second internal passage 332 via the projection 41.

[0059] Figure 8 is a cross-sectional perspective view showing the first valve vent 32 of the engine 10. Figure 8 is a cross-section along the B-B cross-section line in Figure 7A. The B-B cross-section line is a cross-section that includes the vertical and horizontal directions.

[0060] The first valve vent 32 is an air passage formed continuously from the front side to the rear side of the second engine block 112. The first valve vent 32 is formed between the valve mounting hole 21 and the second cylinder bore 122. Specifically, the first valve vent 32 is formed immediately above the second cylinder bore 122. Furthermore, the first valve vent 32 is formed below the intake valve mounting hole 211 and the exhaust valve mounting hole 212. In this way, the air passing through the first valve vent 32 receives heat from the second cylinder bore 122 side. In addition, the air passing through the first valve vent 32 receives heat from the plug cap 221 and the exhaust valve mounting hole 212. In particular, since the exhaust valve mounting hole 212 is through which the air after combustion passes, the heat generated from the exhaust valve mounting hole 212 is absorbed by the air passing through the first valve vent hole 32, thereby preventing the exhaust valve mounting hole 212 from overheating.

[0061] Referring to Figure 7A, in this embodiment, the intake valve mounting hole 211 and the exhaust valve mounting hole 212 are sandwiched between the first valve vent hole 32 and the second valve vent hole 33. That is, the first valve vent hole 32 is located to the left of the intake valve mounting hole 211 and the exhaust valve mounting hole 212. The second valve vent hole 33 is located to the right of the intake valve mounting hole 211 and the exhaust valve mounting hole 212. With this configuration, the intake valve mounting hole 211 and the exhaust valve mounting hole 212 can be effectively cooled by the air flowing inside the first valve vent hole 32 and the second valve vent hole 33.

[0062] Figure 9A is a perspective view showing the first engine block 111 of engine 10. Figure 9B is an exploded perspective view showing the first engine block 111 of engine 10.

[0063] Referring to Figure 9A, a plug vent 34 is formed in the first engine block 111. The plug vent 34 is an air passage formed to penetrate the first engine block 111 in the front-rear direction. The plug vent 34 is formed near the upper surface of the first engine block 111. The plug vent 34 opens to the front and rear surfaces of the first engine block 111.

[0064] The intermediate portion of the plug vent hole 34 in the front-rear direction is covered by a vent hole protection portion 35 made of a metal plate or the like. The spark plug 22 is positioned in the intermediate portion of the plug vent hole 34 in the front-rear direction. The spark plug 22 is inserted toward the engine block 11 through a notch 351 formed in the vent hole protection portion 35.

[0065] Referring to Figure 9B, the plug vent 34 has, from the front side, a front vent portion 341, a middle vent portion 342, and a rear vent portion 343. When the engine 10 is running, air flows in the order of front vent portion 341, middle vent portion 342, and rear vent portion 343. The plug vent 34 is an air passage formed near the spark plug 22. The air flowing through the plug vent 34 effectively cools the vicinity of the plug mounting hole 23 and the spark plug 22.

[0066] The front part 341 of the ventilation hole is a conduit located at the front. When viewed from the front, the front part 341 of the ventilation hole has a roughly rectangular shape with its longitudinal direction in the left-right direction.

[0067] The intermediate vent portion 342 is the intermediate part of the plug vent 34 and is an open portion. Furthermore, the intermediate vent portion 342 is the portion in the first engine block 111 where the plug mounting hole 23 is located.

[0068] The rear vent portion 343 is a conduit located at the rear. When viewed from the front, the rear vent portion 343 has a roughly rectangular shape with its longitudinal direction in the left-right direction.

[0069] The ventilation hole protection part 35 is positioned to cover the intermediate portion 342 of the ventilation hole. By covering the intermediate portion 342 of the ventilation hole with the ventilation hole protection part 35, the intermediate portion 342 of the ventilation hole acts like a closed pipe. In addition, a roughly cylindrical plug cap 221 made of resin, which covers the spark plug 22, is positioned in the notch 351.

[0070] The plug mounting hole 23 is a through-hole that penetrates the thick portion of the engine block 11, and is a through-hole that connects the extension space 24 shown in Figure 5 to the outside of the first engine block 111. The tip of the spark plug 22 is inserted into the plug mounting hole 23. The tip of the spark plug 22 is positioned in the extension space 24 shown in Figure 5.

[0071] Figure 10 is a perspective view showing the engine 10. Figure 11 is an exploded perspective view showing the engine 10.

[0072] The engine 10 has an engine block 11, and various devices are attached to the engine block 11 to improve the efficiency of cooling the engine 10 during operation.

[0073] In this configuration, the engine block 11 is fitted with a first blower fan 361, a second blower fan 362, a first air guide 371, a second air guide 372, an upper cover 391, and a lower cover 392.

[0074] Referring to Figure 11, a generator (not shown) that generates electricity using the rotational driving force of the first crankshaft 143 shown in Figure 1 may be installed between the first blower fan 361 and the engine block 11. Similarly, a generator (not shown) that generates electricity using the rotational driving force of the second crankshaft 153 shown in Figure 1 may be installed between the second blower fan 362 and the engine block 11.

[0075] The first blower fan 361 is a blower that is rotated by the first crankshaft 143 shown in Figure 1. As shown in Figure 11, the first blower fan 361 is equipped with multiple rotating blades. When the first blower fan 361 rotates, an airflow is generated that follows a counterclockwise direction when viewed from the front.

[0076] The second blower fan 362 is a blower that is rotated by the second crankshaft 153 shown in Figure 1. As shown in Figure 11, the second blower fan 362 is equipped with multiple rotating blades. When the second blower fan 362 rotates, an airflow is generated that follows a clockwise direction when viewed from the front.

[0077] The first air guide section 371 is a cover attached to the engine block 11 so as to cover the first blower fan 361. The first air guide section 371 is a component that constitutes an air tunnel that guides the airflow generated by the rotation of the first blower fan 361 to the plug vent hole 34. The first connecting section 381 is fitted into the end opening of the first air guide section 371. The first connecting section 381 is a relay member that connects the opening located at the left end of the first air guide section 371 to the plug vent hole 34.

[0078] The second air guide section 372 is a cover attached to the engine block 11 so as to cover the second blower fan 362. The second air guide section 372 is a component that constitutes an air tunnel that guides the airflow generated by the rotation of the second blower fan 362 to the first valve vent 32 and the second valve vent 33. The second connecting section 382 is fitted into the end opening of the second air guide section 372. The second connecting section 382 is a relay member that connects the opening located at the right end of the second air guide section 372 to the first valve vent 32 and the second valve vent 33.

[0079] The upper cover 391 is a member that covers the upper surface of the engine block 11, specifically the portion where the first engine block 111 and the second engine block 112 described above are arranged. As will be described later, when the engine 10 is mounted on the aircraft 50, the aircraft 50 flies forward, generating a flight airflow that flows from front to rear relative to the engine 10. A portion of this flight airflow passes between the upper cover 391 and the upper surface of the engine block 11. Numerous fins 115 extending in the front-to-back direction are formed on the upper surface of the first engine block 111. Therefore, a portion of the flight airflow passes between the upper cover 391 and the engine block 11, effectively cooling the upper portion of the engine block 11.

[0080] The lower cover 392 is a member that covers the lower surface of the engine block 11, specifically the lower surface of the portion where the first engine block 111 and the second engine block 112 described above are arranged. As described above, a portion of the airflow generated when the aircraft 50 is in flight passes between the lower cover 392 and the lower surface of the engine block 11. Numerous fins 115 extending in the front-rear direction are formed on the lower surface of the first engine block 111. Therefore, a portion of the airflow passes between the lower cover 392 and the lower surface of the engine block 11, thereby effectively cooling the lower portion of the engine block 11.

[0081] Figure 12A is an exploded perspective view showing the second air guide section 372. Figure 12B is an exploded perspective view showing the second air guide section 372 from a different angle.

[0082] Referring to Figure 12A, the second air guide section 372 has a front air guide section 3721, a rear air guide section 3722, and a connection port 3723. The second air guide section 372 is an air passage component that guides the airflow generated by the rotation of the second blower fan 362 to the first valve vent hole 32. The second air guide section 372 has an opening in its center for taking in air from the front. In addition, an air passage is formed around the periphery of the second air guide section 372 that directs the airflow generated by the rotation of the second blower fan 362 in a predetermined direction.

[0083] The forward air guide portion 3721 is a component that constitutes the front portion of the second air guide portion 372. As shown in Figure 12B, the outer peripheral recess portion 3724 is formed by recessing the peripheral edge of the outer peripheral recess portion 3724 toward the front. When viewed from the rear, the outer peripheral recess portion 3724 is a concave groove that gradually deepens in a clockwise direction. The shape of the outer peripheral recess portion 3724 allows the airflow generated by the rotation of the second blower fan 362 to flow more effectively toward the connection port 3723.

[0084] The configuration of the first air guide section 371 is the same as that of the second air guide section 372 described above.

[0085] The second connecting portion 382 is a substantially cylindrical member. As shown in Figure 12A, the front end of the second connecting portion 382 is connected by being inserted into a connection port 3723 formed at the air passage end of the rear air guide portion 3722. On the other hand, the rear end of the second connecting portion 382 is connected to the first valve vent 32 and the second valve vent 33 of the engine block 11, as shown in Figure 11. Therefore, the airflow generated by the rotation of the second blower fan 362 is blown through the second air guide portion 372 and the second connecting portion 382 to the first valve vent 32 and the second valve vent 33, cooling the engine block 11.

[0086] Similarly, referring to Figure 11, the airflow generated by the rotation of the first blower fan 361 is blown to the plug vent 34 via the first air guide 371 and the first connection 381, cooling the engine block 11.

[0087] As described above, the exterior and interior of the engine block 11 are effectively cooled, thereby effectively preventing overheating of the engine 10 during operation. Specifically, referring to Figure 3, the first engine block 111 and the second engine block 112 become particularly hot during operation because the explosion stroke takes place inside them. Therefore, cooling the first engine block 111 and the second engine block 112 is essential to prevent overheating of the engine 10.

[0088] Therefore, in this embodiment, as shown in Figure 7A and the like, a first valve vent 32 and a second valve vent 33 are formed in the second engine block 112. Also, as shown in Figure 8 and the like, a plug vent 34 is formed in the first engine block 111. By blowing air into the first valve vent 32, the second valve vent 33, and the plug vent 34, the vicinity of the valve mounting hole 21 and the vicinity of the plug mounting hole 23, which generate a lot of heat when the engine 10 is running, can be actively cooled. Here, the air may be the airflow generated by the flight of the aircraft 50, which will be described later, or the airflow generated by the rotation of the first blower fan 361, etc.

[0089] Referring to Figure 11, the system includes a first blower fan 361 and a first air guide 371 to actively supply air to the fourth opening 396 of the main body and the plug vent 34. The airflow generated by the rotation of the first blower fan 361 is supplied to the plug vent 34 via the first air guide 371. The airflow generated by the rotation of the second blower fan 362 is supplied to the first valve vent 32 and the second valve vent 33 via the second air guide 372. In this way, a large flow rate of air can be supplied to the first valve vent 32, the second valve vent 33 and the plug vent 34, allowing for more active cooling of the first engine block 111 and the second engine block 112. Furthermore, the first air guide 371 and the second air guide 372 have a substantially circular opening in their center that takes in air from the front. During the flight of the aircraft 50, which will be described later, airflow from the aircraft is supplied to this opening. This also allows for an increase in the air velocity of the air blown into the plug mounting holes 23, the second valve vent holes 33, and the plug vent holes 34, thereby improving the cooling efficiency of the engine block 11.

[0090] Furthermore, fins 115 are formed on the surfaces (front, rear, bottom, and top) of the first engine block 111 and the second engine block 112, extending along the front-to-back direction. The top surfaces of the first engine block 111 and the second engine block 112 are covered by an upper cover 391. During flight of the aircraft 50, which will be described later, airflow circulates between the top surfaces of the first engine block 111 and the second engine block 112 and the upper cover 391. The bottom surfaces of the first engine block 111 and the second engine block 112 are covered by a lower cover 392. During flight of the aircraft 50, which will be described later, airflow circulates between the bottom surfaces of the first engine block 111 and the second engine block 112 and the lower cover 392. In this way, the first engine block 111 and the second engine block 112 are cooled from the outside as well.

[0091] Based on the above, the engine 10 effectively prevents overheating during operation by effectively cooling the first engine block 111 and the second engine block 112 from both the inside and the outside.

[0092] Figure 13 is a perspective view showing the flying device 50 equipped with the engine 10. Figure 14 is a plan view showing the flying device 50 equipped with the engine 10. Figure 15 is a side view showing the flying device 50 equipped with the engine 10. Here, the up, down, front, back, left, and right directions shown in Figure 1, etc., correspond to the up, down, front, back, left, and right directions in the description of the flying device 50.

[0093] The flight device 50 is equipped with the aforementioned engine 10. More specifically, the flight device 50 is a series hybrid drone that flies by rotating a rotor 54 using electricity generated by the engine 10.

[0094] Specifically, the flying device 50 includes an engine 10, a main body 53, an arm 51, a motor 55, a rotor 54, and skids 52.

[0095] The engine 10 is a power source that generates the driving force necessary for the flight device 50 to fly. The configuration of the engine 10 is as described above.

[0096] The main body 53 is made up of rod-shaped members assembled into a roughly rectangular parallelepiped, and houses the various components that make up the flight device 50. For example, the engine 10, various electrical equipment, fuel tanks, etc., are housed in the main body 53.

[0097] The arms 51 are roughly rod-shaped members that extend outward from the corners of the main body 53. In this case, four arms 51 extend outward from the corners of the main body 53.

[0098] The motor 55 is located at the outer end of the arm 51. The motor 55 is powered by a generator driven by the engine 10. The motor 55 generates the driving force necessary for the rotor 54 to rotate.

[0099] The rotor 54 is positioned at the outer end of the arm 51 and is rotated by the motor 55. As the rotor 54 rotates, the entire flight device 50 floats, allowing its position and attitude to be controlled in the air.

[0100] The skid 52 is a member that extends downward from the lower end of the main body 53. When the flying device 50 lands, the skid 52 makes contact with the landing surface. As a result, when landing, the main body 53 and the like are supported at a position above the landing surface.

[0101] As the flying device 50 moves forward in the air, a flight airflow is generated. This flight airflow can effectively cool the engine 10.

[0102] The configuration of the engine 10 in other configurations will be described with reference to Figures 16 to 17B. The configuration and operation of the engine 10 in other configurations are, in principle, the same as the engine 10 described above with reference to Figure 1, etc. In the engine 10 described below, the configuration of the plug vent hole 34 and its surrounding area formed in the first engine block 111 differs from the configuration shown in Figure 1, etc. The following will focus on explaining these differences.

[0103] Figure 16 is a perspective view showing an engine 10 in another configuration.

[0104] Referring to Figure 16, a ventilation hole 30 is formed in the engine block 11 of the engine 10. As mentioned above, the ventilation hole 30 is a through-hole through which air passes to cool the engine block 11. The ventilation hole 30 has a main body fourth opening 396, a first valve ventilation hole 32, a second valve ventilation hole 33, and a plug ventilation hole 34.

[0105] The plug vents 34 shown in other embodiments have a different shape from those described above. Specifically, the plug vents 34 in a front view have a roughly rectangular shape with a longitudinal direction along the vertical direction. Furthermore, the plug vents 34 are through-holes that continuously penetrate the first engine block 111 from the front to the rear.

[0106] Figure 17A is a perspective view partially showing an engine 10 according to another embodiment. Figure 17B is a cutaway perspective view showing an engine 10 according to another embodiment. Figure 17B is a cross-section along the C-C cutting plane line in Figure 17A. The C-C cutting plane is a cross-section that includes the vertical and horizontal directions.

[0107] Referring to Figure 17A, the plug mounting hole 23 is configured to penetrate the lower end of the plug ventilation hole 34. The plug mounting hole 23 is the hole into which the portion near the tip of the spark plug 22 described above is inserted.

[0108] Fastening holes 40 are formed in the plug vent hole 34. The fastening holes 40 are through holes that penetrate the plug vent hole 34 in the left-right direction. The fastening holes 40 have a substantially cylindrical shape. The fastening holes 40 are through holes through which bolts pass for fastening the first engine block 111 to the fourth engine block 114, which constitute the engine block 11, to each other, as described above. Multiple fastening holes 40 are formed in the plug vent hole 34.

[0109] Referring to Figure 17B, a protrusion 41 is formed inside the plug vent hole 34. The protrusion 41 is a portion that protrudes to the right in a substantially cylindrical shape from the left side surface of the plug vent hole 34. The protrusion 41 is formed collectively by casting together with the main body of the first engine block 111. Multiple protrusions 41 are arranged so as to surround the plug mounting hole 23. By forming the protrusion 41, the surface area of ​​the heat dissipation area around the plug mounting hole 23 can be increased. Therefore, the air passing inside the plug vent hole 34 actively exchanges heat with the protrusion 41, thereby effectively cooling the area around the plug mounting hole 23. In addition, a fastening hole 40 is also exposed inside the plug vent hole 34. Since the fastening hole 40 is also part of the first engine block 111, the fastening hole 40 is exposed inside the plug vent hole 34, and the air flowing through the plug vent hole 34 from front to rear absorbs heat from the fastening hole 40, thereby effectively cooling the first engine block 111.

[0110] [Second Embodiment] The configuration and operation of the engine 10 according to the second embodiment will be described below with reference to Figures 18A and later. The configuration and operation of the engine 10 according to the second embodiment are basically the same as those of the engine 10 shown in the first embodiment, so the explanation of the configuration of the same or similar parts will be omitted and the information will be used as is. The engine 10 according to the second embodiment differs from the engine 10 according to the first embodiment in the configuration of the members that cool the engine block 11. The description of the second embodiment will focus on these differences.

[0111] Figure 18A is a front perspective view of the engine 10 and fan cover 42, etc., according to the second embodiment. Figure 18B is a rear perspective view of the engine 10 and fan cover 42, etc., according to the second embodiment. Figure 19A is a front view of the engine 10 and fan cover 42, etc., according to the second embodiment. Figure 19B is a rear view of the engine 10 and fan cover 42, etc., according to the second embodiment. Figure 20A is a bottom view of the engine 10 and fan cover 42, etc., according to the second embodiment. Figure 20B is a left side view of the engine 10 and fan cover 42, etc., according to the second embodiment.

[0112] Referring to Figures 18A to 20B, a fan cover 42 is assembled to the front of the engine 10.

[0113] The engine 10 is a so-called opposed engine, and the structure of the engine 10, which has engine sections facing each other along the left-right direction, is as described with reference to Figure 5, etc.

[0114] The engine 10 has an engine block 11, and the central portion of the engine block 11 in the left-right direction, that is, the portion where the aforementioned cylinder bore 12 is formed, is covered by a main body cover 39. The main body cover 39 is made of a resin plate or a metal plate or the like. As will be described later, the main body cover 39 has a plurality of openings for circulating air.

[0115] Referring to Figures 18A to 20B, the fan cover 42 is a cover member assembled to the front of the engine 10. As will be described later, the fan cover 42 has a front fan cover 421 and a rear fan cover 422. A substantially circular front first opening 431 and a front second opening 432 are formed on the front of the fan cover 42. The front first opening 431 and the front second opening 432 are openings for taking in air from the outside. Inside the fan cover 42, a first blower fan 361 and a second blower fan 362 are arranged. The first blower fan 361 is arranged behind the front part 341 of the ventilation hole, and the second blower fan 362 is arranged behind the front second opening 432.

[0116] Referring to Figure 18B, the first crankshaft 143 and camshaft 27 are arranged on the rear side of the engine 10. The rear surface of the main body cover 39 has a fourth opening 396 and a third opening 395. The lower left part of the engine block 11 is the crankcase 62. In this embodiment, the crankcase 62 is part of the fourth engine block 114 in the first embodiment. An oil reservoir is formed spanning the lower part of the engine block 11 and the crankcase 62. The oil reservoir functions as a reservoir that receives and temporarily stores oil that circulates through each lubrication point such as the cylinder block and falls down due to its own weight. The oil reservoir, which is part of the crankcase 62, maintains a liquid level that allows the slinger provided on the connecting rod to pass through its trajectory and stably scoop up oil. Furthermore, since the crankcase 62 is usually located in a position that receives airflow while driving, such as under the floor of the vehicle, it performs the function of cooling the oil, which has become hot from heat absorption from inside the engine, by heat exchange with the outside air through its walls. This cooling function will be described later. In addition, the oil reservoir, which is part of the crankcase 62, has a cleaning function that utilizes its volume to separate and settle wear particles, combustion products, and air bubbles that have been mixed into the oil during the circulation process by gravity.

[0117] Referring to Figures 18B, 19B, 20A, 20B, etc., the cooling duct 66 is part of the main body cover 39 and is a component that constitutes an air passage arranged along the lower surface and side surface of the crankcase 62.

[0118] In this embodiment, when the engine 10 is running, the first blower fan 361 and the second blower fan 362 are rotated to generate cooling air, which is then effectively blown onto the engine block 11 and other components to cool the engine block 11.

[0119] As described in the first embodiment, the engine 10 is mounted on the aircraft 50. When the aircraft 50 hovers in windless conditions, the engine 10 is not naturally supplied with air, making heat dissipation of the engine 10 difficult. Referring to Figures 18A, 19A, etc., in this embodiment, in order to effectively cool the engine 10 even in such situations, the engine 10 is operated while the first blower fan 361 and the second blower fan 362 are rotated. When the first blower fan 361 and the second blower fan 362 are rotated by the engine's driving force, air is drawn into the fan cover 42 from the front first opening 431 and the front second opening 432. Referring to Figures 18B, 19B, etc., the drawn-in air effectively exchanges heat with the engine block 11 and is then discharged to the outside from the main body fourth opening 396, the main body third opening 395, and the upper end opening of the cooling duct 66. In this way, the engine 10 can be effectively cooled even when the aircraft 50 is hovering. The cooling structure and other components of the engine 10 will be explained with reference to Figures 21A and later.

[0120] Figure 21A is a front perspective view of the engine 10 according to the second embodiment. Figure 21B is a rear perspective view of the engine 10 according to the second embodiment. Figure 22A is a front view of the engine 10 according to the second embodiment. Figure 22B is a rear view of the engine 10 according to the second embodiment. Figure 23A is a bottom view of the engine 10 according to the second embodiment. Figure 23B is a left side view of the engine 10 according to the second embodiment.

[0121] Referring to Figures 21A and 21B, fins 115 are formed in the central part of the engine block 11 in the left-right direction, that is, in the part where the cylinder bore 12 shown in Figure 5 is formed. As mentioned above, fins 115 are parts that are raised outward in a roughly wall-like manner on the outer surface of the engine block 11. Multiple fins 115 are formed at roughly equal intervals along the left-right direction.

[0122] Referring to Figures 21B, 22A, 22B, 23B, etc., the fins 63 are formed along the surface of the crankcase 62. The fins 63 are raised sections that extend across the lower and left sides of the crankcase 62, with some parts forming a wall-like structure. Multiple fins 63 are formed at approximately equal intervals along the front-rear direction. Referring to Figure 21B, the fins 63 are formed near the lower end of the lower and right sides of the second engine block 112, and on the lower and left sides of the fourth engine block 114. When the engine 10 is running, air is blown along the fins 63, which allows for active cooling of the crankcase 62 and the oil inside it via the fins 63.

[0123] Referring to Figures 22A and 22B, etc., a configuration in which fins 115 are formed inside the ventilation hole 30 will be described.

[0124] As explained in the first embodiment, intake valve mounting holes 211 and exhaust valve mounting holes 212 are formed above the cylinder bore 12 as valve mounting holes 21. A ventilation hole 30 is formed between the cylinder bore 12 and the valve mounting holes 21. The ventilation hole 30 is a through hole that penetrates the engine block 11 in the front-rear direction. The valve mounting holes 21, especially the exhaust valve mounting hole 212, become hot during engine 10 operation because exhaust gas after combustion flows through their interior. Therefore, by forming a ventilation hole 30 between the valve mounting holes 21 and the cylinder bore 12 and allowing air to circulate through the ventilation hole 30, the valve mounting holes 21 and their vicinity can be effectively cooled, preventing overheating.

[0125] In this embodiment, fins 115 are formed inside the ventilation hole 30 with the above configuration. Even if fins 115 are not formed inside the ventilation hole 30, the valve installation hole 21 and the like can be effectively cooled by blowing air into the ventilation hole 30. In this embodiment, a portion of the fins 115 is formed inside the ventilation hole 30. With this configuration, heat exchange between the valve installation hole 21, particularly the exhaust valve installation hole 212, and the air can be performed more actively inside the ventilation hole 30.

[0126] Figure 24 shows the second engine block 112 of the engine 10 according to the second embodiment, with a front view shown in the upper left, a rear view in the upper right, and a cross-sectional perspective view in the lower part. Here, the cross-sectional perspective view shown at the bottom of Figure 24 is a cross-sectional view along the A10-A10 cross-section line in the front view shown in the upper left of Figure 24. The A10-A10 cross-section is a cross-section that includes the front-rear direction and the up-down direction.

[0127] Referring to the cross-sectional view shown at the bottom of Figure 24, the valve mounting hole 21 has an intake valve mounting hole 211 and an exhaust valve mounting hole 212. The intake valve mounting hole 211 is located on the front side, and the exhaust valve mounting hole 212 is located on the rear side. The intake valve mounting hole 211 and the exhaust valve mounting hole 212 are spaced apart in the front-rear direction. A valve intermediate vent hole 60 is formed between the intake valve mounting hole 211 and the exhaust valve mounting hole 212. The valve intermediate vent hole 60 is a space connected to the aforementioned vent hole 30. The valve intermediate vent hole 60 connects the intermediate part of the vent hole 30 to the outside. By forming an intermediate valve vent 60 between the intake valve mounting hole 211 and the exhaust valve mounting hole 212, the air flowing through the intermediate valve vent 60 exchanges heat with the intake valve mounting hole 211 and the exhaust valve mounting hole 212, thereby more effectively cooling the intake valve mounting hole 211 and the exhaust valve mounting hole 212.

[0128] A fin-free region 61 is formed inside the fin 115. The fin-free region 61 is a region between the intake valve mounting hole 211 and the exhaust valve mounting hole 212 where no fins 115 exist. Air can be smoothly circulated from the vent hole 30 to the valve intermediate vent hole 60 via the fin-free region 61. Therefore, the portion of the second engine block 112 near the intake valve mounting hole 211 and the exhaust valve mounting hole 212 can be effectively cooled. The fin-free region 61 may be formed in part of the fin 115 formed inside the vent hole 30, or it may be formed in all of it.

[0129] Figure 25A is a perspective view of the first engine block 111 of the engine 10 according to the second embodiment, viewed from the front. Figure 25B is a front view showing the first engine block 111 of the engine 10 according to the second embodiment.

[0130] As mentioned above, the first engine block 111 has fins 115 that extend outward in a wall-like manner from the main body of the engine block 11. Specifically, referring to Figure 25B, multiple fins 115 are formed in the portion of the first engine block 111 that forms the cylinder bore 12.

[0131] The fin 115 has a first fin 1151 and a second fin 1152. The first fin 1151 is formed near the left end of the first engine block 111, that is, in and around the area where the top dead center of the first piston 141 shown in Figure 5 is located. The first fin 1151 has a relatively large area. The second fin 1152 is formed to the right of the first fin 1151, that is, in a location further away from the top dead center of the first piston 141 shown in Figure 5. When the first fin 1151 and the second fin 1152 are viewed from the left, the area of ​​the second fin 1152 is smaller than the area of ​​the first fin 1151. The reason the area of ​​the second fin 1152 is small is that it is positioned to avoid the spark plug, etc., as shown in Figure 21A, etc. Furthermore, in order to ensure tool clearance for the nuts that fasten the first engine block 111 and the second engine block 112 together, as shown in Figure 21, the area of ​​the second fin 1152 is made smaller than the area of ​​the first fin 1151.

[0132] The fin connecting portion 65 is a part that connects adjacent fins 115. Specifically, the fin connecting portion 65 is formed to penetrate the first fin 1151 and the second fin 1152. In the vertical direction, the fin connecting portion 65 is provided to penetrate and connect the middle part of the first fin 1151 and the vicinity of the upper end of the second fin 1152. Multiple fin connecting portions 65 are formed here. The fin connecting portion 65 is located on the upper side of the part that constitutes the cylinder bore 12 of the first engine block 111. The fin connecting portion 65 is a part that is cast integrally with other parts of the first engine block 111. The fin connecting portion 65 is a solid, substantially cylindrical shape with a central axis along the left-right direction. In this embodiment, the heat generated around the combustion chamber is mainly dissipated by the first fin 1151. Since it is possible that the amount of heat dissipated may be insufficient, the second fin 1152 is provided. Furthermore, in this embodiment, the fins 115 can be thermally coupled to each other by physically connecting the first fin 1151 and the second fin 1152 with the fin coupling portion 65. Therefore, even if the size of the fins 115 and the amount of heat transferred are uneven, heat can be actively dissipated as a whole through the multiple fins 115 that are thermally coupled by the fin coupling portion 65. Specifically, a portion of the heat generated from the first engine block 111 in the part constituting the combustion chamber (extension space 24) and conducted to the first fin 1151 can be further conducted to the 12th fin 1152 via the fin coupling portion 65, allowing the heat to escape into the air.

[0133] Figure 26 is a diagram showing the engine 10 and fan cover 42 etc. according to the second embodiment, and is an exploded perspective view showing the fan cover 42 and blower fan etc. disassembled from the front. Figure 27 is a diagram showing the engine 10 and fan cover 42 etc. according to the second embodiment, and is an exploded perspective view showing the fan cover 42 and blower fan etc. disassembled from the rear.

[0134] Referring to Figures 26 and 27, a fan cover 42, a first blower fan 361, and a second blower fan 362 are arranged on the front of the engine block 11. Also on the front of the engine block 11 are thin generators that generate electricity when rotated by the first crankshaft 143 and the second crankshaft 153, respectively. A portion of the airflow generated by the rotation of the first blower fan 361 and the second blower fan 362 is blown to these generators. In this way, the generators can be adequately cooled during power generation.

[0135] The fan cover 42 has a front fan cover 421 and a rear fan cover 422. The fan cover 42 is constructed by assembling the front fan cover 421 to the front fan cover 421 from the rear and fastening the two together. The fan cover 42 is provided on the front part of the engine block 11 by fastening or other fastening means. Inside the fan cover 42, a first blower fan 361 and a second blower fan 362 are housed in a rotatable state.

[0136] The first blower fan 361 and the second blower fan 362 are devices that generate airflow to cool the engine block 11 and the like by rotating. The first blower fan 361 is rotated by the first crankshaft 143. The first blower fan 361 is connected to the first crankshaft 143 so as not to rotate relative to it and is rotated by the first crankshaft 143. The second blower fan 362 is connected to the second crankshaft 153 so as not to rotate relative to it and is rotated by the second crankshaft 153. When the first blower fan 361 is viewed from the front, it rotates counterclockwise, thereby blowing air radially outward. When the second blower fan 362 is viewed from the front, it rotates clockwise, thereby blowing air radially outward.

[0137] As described above, the front fan cover 421 has a front first opening 431 and a front second opening 432. The front first opening 431 is located on the front side of the first blower fan 361, and the front second opening 432 is located on the front side of the second blower fan 362.

[0138] The rear fan cover 422 is a roughly plate-shaped member that is paired with the front fan cover 421. The rear fan cover 422 has a rear first opening 433, a rear second opening 434, a rear third opening 435, and a rear fourth opening 436. Each of the openings in the rear fan cover 422 will be described later with reference to Figure 29A, etc.

[0139] A first main body opening 393 and a second main body opening 394 are formed on the front surface of the main body cover 39 that covers the engine block 11. Each of the openings provided in the main body cover 39 will be described later with reference to Figure 31A, etc.

[0140] When the engine 10 is in operation, the cooling air flows as follows: Specifically, as the first blower fan 361 and the second blower fan 362 rotate, the air taken in from the front first opening 431 and the front second opening 432 is blown radially outward from the first blower fan 361 and the second blower fan 362. Most of the blown air is blown backward through the rear third opening 435 and the rear fourth opening 436. In addition, a portion of the air blown by the first blower fan 361 and the second blower fan 362 is blown to the generator located behind the first blower fan 361 and the second blower fan 362 to cool the generator.

[0141] Air blown to the rear through the rear third opening 435 is then blown into the main body cover 39 through the main body first opening 393. The air blown into the main body cover 39 cools the engine block 11 near the cylinder bore 12 and valve mounting holes 21 by exchanging heat with the fins 115 and the like. After that, the air that has become hot due to heat exchange inside the main body cover 39 is released to the outside through the main body fourth opening 396 shown in Figure 18B.

[0142] Meanwhile, the air that flows into the main body cover 39 from the main body second opening 394 via the rear fourth opening 436 circulates inside the cooling duct 66 shown in Figure 18B and is discharged to the outside from the upper end of the cooling duct 66. At that time, it exchanges heat with the fins 63 shown in Figure 21B, thereby cooling the crankcase 62 and the oil stored therein.

[0143] Figure 28A is a perspective view of the front fan cover 421 from the front. Figure 28B is a perspective view of the front fan cover 421 from the rear.

[0144] Referring to Figures 28A and 28B, the front fan cover 421 has a front first opening 431 and a front second opening 432. As mentioned above, the front first opening 431 and the front second opening 432 are substantially circular openings through which air is taken in to cool the engine 10.

[0145] Referring to Figure 28B, a first air guide wall 451, a second air guide wall 452, a third air guide wall 453, and a fourth air guide wall 454 are formed on the rear surface of the front fan cover 421. These wall-like portions are for guiding the airflow generated by the rotation of the first blower fan 361 and the second blower fan 362 in a predetermined direction. In Figure 28B, the direction of the airflow generated by the rotation of the first blower fan 361 and the second blower fan 362 is indicated by arrows.

[0146] The first air guide wall 451 is a wall-like portion of the front fan cover 421 between the front first opening 431 and the front second opening 432, recessed toward the rear. When viewed from the rear, the first air guide wall 451 is an arch-shaped portion whose central part curves downward. The shape of the first air guide wall 451 allows it to effectively receive the airflow generated by the rotation of the first blower fan 361 and the second blower fan 362 and guide it toward the rear third opening 435 shown in Figure 27.

[0147] The second air guide wall 452 is a plate-like projection extending rearward from the rear surface of the front fan cover 421. The second air guide wall 452 is positioned below the first air guide wall 451. When viewed from the rear, the second air guide wall 452 has a curved shape with its central portion curving downward. Generally speaking, the second air guide wall 452 has a roughly V-shape or U-shape. Because the second air guide wall 452 has this shape, the airflow generated by the rotation of the first blower fan 361 and the second blower fan 362 is guided to the second air guide wall 452 and introduced into the rear fourth opening 436 shown in Figure 27.

[0148] The third air guide wall 453 is a plate-shaped portion located on the lower left side of the front first opening 431 when the front fan cover 421 is viewed from the rear. When the front fan cover 421 is viewed from the rear, the third air guide wall 453 is configured to slope downward toward the right. The third air guide wall 453 can rectify the airflow generated by the rotation of the aforementioned first blower fan 361.

[0149] The fourth air guide wall 454 is a plate-shaped portion located to the lower right of the front second opening 432 when the front fan cover 421 is viewed from the rear. When the front fan cover 421 is viewed from the rear, the fourth air guide wall 454 is configured to slope downward toward the left. The fourth air guide wall 454 can rectify the airflow generated by the rotation of the aforementioned second blower fan 362.

[0150] Figure 29A is a perspective view of the rear fan cover 422 from the front. Figure 29B is a perspective view of the rear fan cover 422 from the rear.

[0151] Referring to Figures 29A and 29B, the rear fan cover 422 has a rear first opening 433, a rear second opening 434, a rear third opening 435, and a rear fourth opening 436.

[0152] The rear first opening 433 and the rear second opening 434 are openings for housing the first blower fan 361 and the second blower fan 362 described above.

[0153] The rear third opening 435 is an opening formed in the upper part of the rear fan cover 422 between the rear first opening 433 and the rear second opening 434. As shown in Figure 29B, the periphery of the rear third opening 435 has a flange shape that curves toward the rear. The rear end of the rear third opening 435 connects to the main body first opening 393 shown in Figure 26. Therefore, when viewed from the front, the rear third opening 435 of the rear fan cover 422 and the main body first opening 393 of the main body cover 39 are substantially the same in shape and size.

[0154] The rear fourth opening 436 is an opening formed in the lower part of the rear fan cover 422, between the rear first opening 433 and the rear second opening 434. As shown in Figure 29B, the rear fourth opening 436 has a substantially duct shape that extends downward toward the rear. The rear end of the rear fourth opening 436 connects to the main body second opening 394 of the main body cover 39 shown in Figure 26. Therefore, when viewed from the front, the main body second opening 394 of the main body cover 39 and the rear fourth opening 436 of the rear fan cover 422 are substantially the same in shape and size.

[0155] Figure 30A is a front view of the engine 10 and cover member according to the second embodiment. Figure 30B is a rear view of the engine 10 and cover member according to the second embodiment.

[0156] Referring to Figures 30A and 30B, the central part of the engine block 11 in the left-right direction is covered by a main body cover 39. The main body cover 39 covers the engine block 11 and is a member that forms an air passage around the engine block 11 for cooling the engine block 11. As shown in Figure 30A, a first main body opening 393 and a second main body opening 394 are formed on the front surface of the main body cover 39. The first main body opening 393 takes in air to cool the vicinity of the cylinder bore 12 and valve mounting holes 21 of the engine block 11. As shown in Figure 30B, a fourth main body opening 396 and a third main body opening 395 are formed on the rear surface of the main body cover 39. The third main body opening 395 is an opening formed near the lower end of the rear surface of the main body cover 39, and is an opening through which air that has exchanged heat with most of the fins 115 is released to the outside. The fourth opening 396 of the main body is an opening formed on the left side of the rear surface of the main body cover 39, and is an opening through which air that has passed through the aforementioned ventilation holes 30 of the engine block 11 is released to the outside. When the engine 10 is viewed from the rear, the fourth opening 396 of the main body and the ventilation holes 30 overlap.

[0157] Figure 31A is a front perspective view of the cover member covering the central part of the engine block 11. Figure 31B is a rear perspective view of the cover member covering the central part of the engine block 11. Figure 32A is a front view of the cover member covering the central part of the engine block 11. Figure 32B is a rear view of the cover member covering the central part of the engine block 11.

[0158] Referring to Figures 31A to 32B, the main body cover 39 is a component that covers the engine block 11 and guides air to cool the engine block 11. The main body cover 39 has a cooling duct 66 at its lower part. The cooling duct 66 communicates with the internal space of the main body cover 39. When viewed from the front, the cooling duct 66 has a roughly L-shape (see Figure 32A in particular). The cooling duct 66 also forms a groove-shaped member with an opening on its upper surface. The opening on the upper surface of the cooling duct 66 abuts against or approaches the bottom surface and left side surface of the crankcase 62 shown in Figure 21B. The upper end of the cooling duct 66 is open. This open shape allows air that has passed through the inside of the cooling duct 66 to be discharged upward from the upper end of the cooling duct 66.

[0159] As shown in Figures 31A and 32A, the internal region of the cooling duct 66 is continuous with the second opening 394 of the main body. Therefore, under the operating conditions of the engine 10, the air flowing into the cooling duct 66 from the second opening 394 of the main body travels to the left inside the cooling duct 66, then travels upward, and is discharged to the outside from the upper end of the cooling duct 66. The air circulating inside the cooling duct 66 exchanges heat with the fins 63 shown in Figure 21B, thereby effectively cooling the crankcase 62.

[0160] Although embodiments of the present invention have been described above, the present invention is not limited thereto, and modifications are possible without departing from the spirit of the invention. Furthermore, the above-described embodiments can be combined with each other.

[0161] The inventions that can be understood from the embodiments described above, along with their effects, are described below.

[0162] An engine according to an embodiment of the present invention is characterized by comprising: an engine block having a cylinder bore formed therein; a valve mounting hole connected to the side surface of the cylinder bore and having a valve arranged therein; a plug mounting hole connected to the side surface of the cylinder bore and having a spark plug arranged therein; and a ventilation hole penetrating the engine block near the valve mounting hole or the plug mounting hole. According to the engine of the present invention, the portion of the engine block in which the valve mounting hole or the plug mounting hole is formed can be actively cooled.

[0163] Furthermore, in the engine according to the embodiment of the present invention, the vent hole has a valve vent hole, and the valve vent hole is formed in the engine block near the valve mounting hole. According to the engine of the present invention, the portion of the engine block in which the valve mounting hole is formed can be actively cooled.

[0164] Furthermore, in the engine according to an embodiment of the present invention, the valve vent hole has a first valve vent hole, and the first valve vent hole is formed in the engine block between the valve mounting hole and the cylinder bore. According to the engine of the present invention, the space between the valve mounting hole and the cylinder bore can be effectively cooled.

[0165] Furthermore, in the engine according to an embodiment of the present invention, the valve vent hole has a second valve vent hole, and the second valve vent hole is formed in the engine block between the valve mounting hole and the outer surface of the engine block. According to the engine of the present invention, the space between the valve mounting hole and the outer surface of the engine block can be effectively cooled.

[0166] Furthermore, in the engine according to an embodiment of the present invention, the vent hole has a plug vent hole, and the plug vent hole is formed in the engine block near the plug mounting hole. According to the engine of the present invention, the plug mounting hole and its vicinity can be effectively cooled.

[0167] Furthermore, in the engine according to an embodiment of the present invention, the plug vent hole has an open intermediate vent hole portion in its middle section, the spark plug is disposed in the engine block in the portion where the intermediate vent hole portion is located, and the intermediate vent hole portion is covered by a vent hole protection portion. According to the engine of the present invention, the spark plug can be disposed in the intermediate vent hole portion, which is the middle part of the plug vent hole. Also, by covering the intermediate vent hole portion with a vent hole protection portion, the plug vent hole functions as a closed pipe as a whole. As a result, when the engine is running, air can circulate well inside the plug vent hole, and the engine block near the spark plug can be effectively cooled.

[0168] Furthermore, the engine according to the embodiment of the present invention is characterized by forming a protrusion inside the vent hole. According to the engine of the present invention, the effect of heat dissipation inside the vent hole can be significantly improved.

[0169] Furthermore, in the engine according to the embodiment of the present invention, fins are formed inside the valve vent hole. According to the engine of the present invention, the air flowing inside the valve vent hole comes into contact with the fins, thereby further improving heat dissipation between the valve mounting hole and the cylinder bore.

[0170] Furthermore, in the engine according to an embodiment of the present invention, the valve mounting hole has an intake valve mounting hole and an exhaust valve mounting hole, and further comprises a valve intermediate vent hole, the valve intermediate vent hole is characterized in that it connects the intermediate part of the vent hole to the outside and is formed between the intake valve mounting hole and the exhaust valve mounting hole. According to the engine of the present invention, by forming a valve intermediate vent hole between the intake valve mounting hole and the exhaust valve mounting hole, the intake valve mounting hole and the exhaust valve mounting hole can be cooled more effectively by exchanging heat with the intake valve mounting hole and the exhaust valve mounting hole through the air flowing through the valve intermediate vent hole.

[0171] Furthermore, the engine according to the embodiment of the present invention is characterized in that there is a fin-free region inside the vent hole, which is a region where the fins are not present. According to the engine of the present invention, air can be smoothly circulated from the valve vent hole to the intermediate valve vent hole via the fin-free region.

[0172] Furthermore, the engine according to the embodiment of the present invention is characterized by having fins that extend outward in a wall-like manner from the engine block body and having fin connecting portions that connect adjacent fins. According to the engine of the present invention, by connecting adjacent fins with the fin connecting portions, the fins can be thermally bonded to each other. Therefore, even if the size of the fins or the amount of heat generated is uneven, heat can be actively dissipated through the multiple fins that are thermally bonded by the fin connecting portions.

[0173] Furthermore, in the engine according to an embodiment of the present invention, the engine block has a crankcase, and fins are formed along the surface of the crankcase. According to the engine of the present invention, fins are formed along the surface of the crankcase, and by allowing air to pass along these fins, the crankcase can be cooled via the fins.

[0174] 10 Engine 11 Engine Block 111 First Engine Block 112 Second Engine Block 113 Third Engine Block 114 Fourth Engine Block 115 Fin 1151 First Fin 1152 Second Fin 1121 Inner Wall 1122 Outer Wall 12 Cylinder Bore 121 First Cylinder Bore 122 Second Cylinder Bore 13 Engine Section 14 First Engine Section 141 First Piston 142 First Connecting Rod 143 First Crankshaft 15 Second Engine Section 151 Second Piston 152 Second Connecting Rod 153 Second Crankshaft 161 Crank Holder 162 Crank Holder 163 Crank Holder 164 Crank Holder 171 First Extension Forming Surface 172 Second Extension Forming Surface 181 First cylinder wall 182 First extension wall 191 Second cylinder wall 192 Second extension wall 20 Central axis 21 Valve mounting hole 211 Intake valve mounting hole 212 Exhaust valve mounting hole 22 Spark plug 221 Plug cap 23 Plug mounting hole 24 Extension space 25 Valve 251 Intake valve 252 Exhaust valve 261 Intake cam 262 Exhaust cam 27 Camshaft 28 Inner surface 30 Ventilation hole 31 Valve vent hole 32 First valve vent hole 33 Second valve vent hole 331 Second front opening 332 Second internal passage 333 Second rear opening 34 Plug vent hole 341 Front part of vent hole 342 Middle part of vent hole 343 Rear part of vent hole 35 Ventilation hole protection part 351 Notch part 361 First blower fan 362 Second blower fan 371 First air guide part 372 Second air guide part 3721 Front air guide part 3722 Rear air guide part 3723 Connection port 3724 Outer circumference concave part 381 First connection part 382 Second connection part 39 Main body cover 391 Upper cover 392 Lower cover 393 Main body first opening 394 Main body second opening 395 Main body third opening 396 Main body fourth opening 40 Fastening hole 41 Protruding part 42 Fan cover 421 Front fan cover 422 Rear fan cover 431 Front first opening 432 Front second opening 433 Rear first opening 434 Rear second opening 435 Rear third opening 436 Rear fourth opening 44 Lower ventilation hole451 First air guide wall 452 Second air guide wall 453 Third air guide wall 454 Fourth air guide wall 50 Flight device 51 Arm 52 Skid 53 Main body 54 Rotor 55 Motor 60 Valve intermediate vent 61 Finless area 62 Crankcase 63 Fin 65 Fin connection part 66 Cooling duct

Claims

1. An engine comprising: an engine block having a cylinder bore formed inside it; a valve mounting hole connected to the side surface of the cylinder bore and having a valve positioned inside it; a plug mounting hole connected to the side surface of the cylinder bore and having a spark plug positioned inside it; and a vent hole penetrating the engine block near the valve mounting hole or the plug mounting hole.

2. The engine according to claim 1, wherein the vent hole has a valve vent hole, and the valve vent hole is formed in the engine block near the valve mounting hole.

3. The engine according to claim 2, wherein the valve vent hole has a first valve vent hole, and the first valve vent hole is formed in the engine block between the valve mounting hole and the cylinder bore.

4. The engine according to claim 2, wherein the valve vent hole has a second valve vent hole, and the second valve vent hole is formed in the engine block between the valve mounting hole and the outer surface of the engine block.

5. The engine according to claim 1, wherein the ventilation hole has a plug ventilation hole, and the plug ventilation hole is formed in the engine block near the plug mounting hole.

6. The engine according to claim 5, characterized in that the plug vent hole has an open intermediate vent hole portion in its middle, the spark plug is disposed in the portion of the engine block where the intermediate vent hole portion is disposed, and the intermediate vent hole portion is covered by a vent hole protective portion.

7. The engine according to claim 1, characterized in that a protrusion is formed inside the ventilation hole.

8. The engine according to claim 1, characterized in that fins are formed inside the ventilation holes.

9. The engine according to claim 1, wherein the valve mounting hole has an intake valve mounting hole and an exhaust valve mounting hole, and further comprises a valve intermediate vent hole, the valve intermediate vent hole communicates the intermediate portion of the vent hole with the outside, and is formed between the intake valve mounting hole and the exhaust valve mounting hole.

10. The engine according to claim 8, characterized in that a finless region exists inside the vent hole, which is a region where the fins are not present.

11. The engine according to claim 1, characterized in that it has fins that extend outward in a wall-like manner from the engine block body, and fin connecting portions that connect adjacent fins.

12. The engine according to claim 1, wherein the engine block has a crankcase, and fins are formed along the surface of the crankcase.

Images