Engine

Abstract

Provided is an engine with which complication of a fastening configuration of an engine block can be suppressed.　An engine 10 is provided with: a cylinder chamber 12 composed of a plurality of engine blocks 11; and a cooling flow path 24 formed in the vicinity of the cylinder chamber 12 and through which a cooling fluid 23 flows. A part of a fastening member 18 for fastening the engine blocks 11 to each other is arranged in the cooling flow path 24. In this way, since a part of the fastening member 18 for fastening the engine block 11 is arranged in the cooling flow path 24, the cooling flow path 24 also serves as a region for arranging the fastening member 18, so that the engine 10 can be miniaturized.

Description

engine

[0001] The present invention relates to engines, and more particularly to opposed-piston engines.

[0002] Conventionally, opposed-piston engines have generally been structured so that pistons with opposing piston heads move linearly within a single horizontally arranged cylinder, as shown in Patent Documents 1 and 2. Within this cylinder, the area where the piston heads face each other functions as a combustion chamber, and a gas mixture of fuel and air ignites and explodes, moving the piston and supplying power to an external actuator such as a generator.

[0003] However, the engine described in the patent document has a small combustion chamber volume, making it difficult to achieve a high compression ratio, and there are also issues with insulating the combustion chamber. Also, the intake and exhaust valves of conventional opposed-piston engines open directly into the combustion chamber, which has the drawback of increasing the volume of the combustion chamber.

[0004] To solve this problem, the engine described in Patent Document 3 below was invented. In the engine described in Patent Document 3, independent left and right pistons are arranged facing each other inside a horizontal cylinder. A combustion chamber is formed between the left and right piston heads and communicates with the outside of the horizontal cylinder. Furthermore, the engine described in Patent Document 3 has an extension portion that extends laterally from the combustion chamber. A plug is provided in the extension portion.

[0005] JP 2007-46534 A JP 8-93498 A Patent No. 5508604

[0006] The opposed-piston engines described in the aforementioned patent documents have one combustion chamber, and two pistons reciprocate within the combustion chamber to generate kinetic energy. However, if the combustion chamber is enlarged or multiple combustion chambers are added for the purpose of improving the output of the opposed-piston engine, the engine configuration becomes more complex. For example, since the engine is constructed by fastening multiple engine blocks together, the number of fastening members required to fasten the engine blocks together increases, which could result in a more complex or larger configuration for arranging the fastening members.

[0007] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an engine that can suppress the complexity of the fastening configuration of the engine block.

[0008] The engine of the present invention comprises a cylinder chamber formed by a plurality of engine blocks, and a cooling flow path formed near the cylinder chamber and through which a cooling fluid flows, and is characterized in that a portion of the fastening members that fasten the engine blocks together are arranged in the cooling flow path.

[0009] In addition, in the engine of the present invention, the engine block has a first engine block and a second engine block fastened to the first engine block by the fastening members, the cylinder chamber has a first cylinder chamber and a second cylinder chamber adjacent to the first cylinder chamber, pistons arranged opposite each other are arranged to reciprocate inside the first cylinder chamber, and pistons arranged opposite each other are arranged to reciprocate inside the second cylinder chamber, the cooling flow path is configured to cool the first cylinder chamber and the second cylinder chamber, the first cylinder chamber and the second cylinder chamber are spaces formed by joining the first engine block and the second engine block, and a portion of the fastening member is arranged in the cooling flow path.

[0010] In the engine of the present invention, a seal member is interposed between the fastening member and the engine block.

[0011] In the engine of the present invention, a seal member is interposed between the fastening member and the first engine block and between the fastening member and the second engine block.

[0012] In addition, in the engine of the present invention, the first engine block includes a first cooling flow path that is a part of the cooling flow path and a first fastening hole that communicates with the first cooling flow path and is a hole through which the fastening member is inserted; the second engine block includes a second cooling flow path that is another part of the cooling flow path and a second fastening hole that communicates with the second cooling flow path and is a hole through which the fastening member is inserted; the sealing member includes a first sealing member and a second sealing member, the first sealing member being interposed between the fastening member and the first fastening hole, and the second sealing member being interposed between the fastening member and the second fastening hole.

[0013] In the engine of the present invention, the cooling flow passage in the portion where the fastening member is disposed is formed between the first cylinder chamber and the second cylinder chamber.

[0014] In the engine of the present invention, the fastening member is a stud bolt, and the sealing member is an O-ring.

[0015] The engine of the present invention comprises a cylinder chamber formed by a plurality of engine blocks, and a cooling passage formed near the cylinder chamber and through which a cooling fluid flows, and is characterized in that some of the fastening members that fasten the engine blocks together are disposed in the cooling passage. According to the engine of the present invention, by disposing some of the fastening members that fasten the engine blocks in the cooling passage, the cooling passage also serves as an area for disposing the fastening members, thereby realizing a compact engine.

[0016] In the engine of the present invention, the engine block includes a first engine block and a second engine block fastened to the first engine block by the fastening members, the cylinder chamber includes a first cylinder chamber and a second cylinder chamber adjacent to the first cylinder chamber, opposing pistons are arranged to reciprocate within the first cylinder chamber, opposing pistons are arranged to reciprocate within the second cylinder chamber, the cooling channel is configured to cool the first cylinder chamber and the second cylinder chamber, the first cylinder chamber and the second cylinder chamber are spaces formed by joining the first engine block and the second engine block, and a part of the fastening members is disposed in the cooling channel. According to the engine of the present invention, the cooling channel also serves as an area for arranging the fastening members, thereby allowing the first cylinder chamber and the second cylinder chamber to be closer to each other and achieving a compact engine.

[0017] In addition, the engine of the present invention is characterized in that a seal member is interposed between the fastening member and the engine block. According to the engine of the present invention, by interposing a seal member between the fastening member and the engine block, it is possible to prevent the cooling fluid from leaking out of the cooling flow path to the outside.

[0018] In the engine of the present invention, a seal is interposed between the fastening member and the first and second engine blocks. By interposing the seal between the fastening member and the first and second engine blocks, the engine of the present invention can prevent the cooling fluid from leaking out of the cooling passages.

[0019] In the engine of the present invention, the first engine block includes a first cooling passage that is a part of the cooling passage and a first fastening hole that communicates with the first cooling passage and through which the fastener is inserted, the second engine block includes a second cooling passage that is another part of the cooling passage and a second fastening hole that communicates with the second cooling passage and through which the fastener is inserted, the seal members include a first seal member and a second seal member, the first seal member is interposed between the fastener and the first fastening hole, and the second seal member is interposed between the fastener and the second fastening hole. This engine can prevent cooling fluid from leaking to the outside from between the fastener and the first fastening hole and between the fastener and the second fastening hole.

[0020] In the engine of the present invention, the cooling passage in the portion where the fastening member is disposed is formed between the first cylinder chamber and the second cylinder chamber. According to the engine of the present invention, the fastening member can be disposed in the space formed between the first cylinder chamber and the second cylinder chamber, thereby making it possible to make the entire engine smaller.

[0021] In the engine of the present invention, the fastening member is a stud bolt and the sealing member is an O-ring. With the engine of the present invention, leakage of cooling fluid from between the stud bolt and the engine block can be suppressed.

[0022] FIG. 1 is a perspective view of an engine according to an embodiment of the present invention; FIG. 1 is an exploded perspective view of an engine block as seen from the front; FIG. 2 is an exploded perspective view of an engine according to an embodiment of the present invention, as seen from the rear; FIG. 3 is a perspective view of an engine part; FIG. 4 is a cross-sectional view of a wall portion of the engine block that forms a cylinder chamber and an extension space; FIG. 5 is an exploded perspective view of an engine according to an embodiment of the present invention, as seen from the rear, showing a fastening structure between a first engine block and a second engine block; FIG. 6 is an exploded perspective view of an engine according to an embodiment of the present invention, as seen from the front, showing a fastening structure between a first engine block and a second engine block; FIG. 7 is an exploded perspective view of an engine according to an embodiment of the present invention, as seen from the front; FIG. 8 is a cross-sectional view of an engine according to an embodiment of the present invention, as seen from the front; Fig. 1 is a view showing an engine according to an embodiment of the present invention, and is a cross-sectional view showing the relative configuration between a first fastening hole and a stud bolt; Fig. 2 is a view showing an engine according to an embodiment of the present invention, and is a cross-sectional view showing the relative configuration between a second fastening hole and a stud bolt; Fig. 3 is a view showing an engine according to an embodiment of the present invention, and is a perspective view showing a stud bolt and a cooling flow passage from the rear; Fig. 4 is a view showing an engine according to an embodiment of the present invention, and is a perspective view showing a stud bolt and a cooling flow passage from the front.

[0023] An engine 10 according to an embodiment of the present invention will be described in detail below with reference to the drawings. In the following description, the longitudinal direction refers to the direction in which pistons, described below, reciprocate. The left-right direction refers to the direction in which cylinder spaces, described below, are arranged. In the following description, the same components are generally designated by the same reference numerals, and repeated description will be omitted. Furthermore, in this embodiment, the configuration recited in the claims will be mainly illustrated and described. Therefore, parts of the engine 10 other than the relevant components, such as a spark plug, a crankshaft rotation synchronization mechanism, a lubricating oil supply mechanism, a fuel supply mechanism, and electrical components, are not illustrated.

[0024] FIG. 1 is a perspective view showing an engine 10. As shown in FIG.

[0025] The engine 10 is an opposed-piston engine having a plurality of pistons arranged in opposition to each other. The internal configuration and operation of the engine 10 will be described later with reference to Figure 2 and subsequent figures.

[0026] The engine 10 is configured to operate using gasoline, diesel, hydrogen, or the like as fuel. The engine 10 can be used as a drive source for various devices. The engine 10 is used as a drive source for vehicles, generators, water heaters, flight devices, drones, series hybrid drones, parallel hybrid drones, and the like. A series hybrid drone is a drone in which a generator is driven by the engine 10, and the power generated by the generator is used to rotate a motor, which in turn rotates a rotor, causing the aircraft to levitate in the air by the lift generated by the rotor rotation. A parallel hybrid drone is a drone in which a main rotor is mechanically rotated by the engine, causing the aircraft to levitate by the lift generated by the main rotor rotation. The engine 10 of this embodiment is an opposed-piston engine, and is lightweight and low-vibration, making it suitable as a drive source for series hybrid drones, parallel hybrid drones, and the like.

[0027] Specifically, the engine 10 has an engine block 11, which is a main body of the engine. The engine block 11 is made of, for example, a cast aluminum alloy. The engine block 11 is made up of a first engine block 111, a second engine block 112, a third engine block 113, and a fourth engine block 114. These components are fastened to one another by fastening members 18, which will be described later.

[0028] A third crankshaft 163 and a fourth crankshaft 173 extend from the right side of the engine 10. Rotational power can be extracted to the outside from the third crankshaft 163 and the fourth crankshaft 173. Shafts can also be extended from the left side of the engine 10 to extract power to the outside from these shafts.

[0029] 2 and 3 are exploded perspective views of the engine block 11 as seen from the front and rear, respectively.

[0030] 2 and 3, the engine block 11 has, from the front side, a third engine block 113, a first engine block 111, a second engine block 112, and a fourth engine block 114. The first engine block 111 to the fourth engine block 114 are fastened to one another by fastening members 18, which will be described later.

[0031] The first engine block 111 and the second engine block 112 have a first cylinder chamber 121 and a second cylinder chamber 122 formed therein, which are cylinder chambers 12. The configurations of the first engine block 111 and the second engine block 112 will be described later with reference to Figures 6 and 7, etc.

[0032] The third engine block 113 houses the third crankshaft 163 and other components. The third crankshaft 163 and other components are rotatably held by a semicircular crank holder 30 formed at the rear of the third engine block 113 and a semicircular crank holder 31 formed at the front of the first engine block 111.

[0033] The fourth engine block 114 houses the fourth crankshaft 173 and other components. The fourth crankshaft 173 and other components are rotatably held by a semicircular crank holder 33 formed in the front of the fourth engine block 114 and a semicircular crank holder 32 formed in the rear of the second engine block 112.

[0034] FIG. 4 is a perspective view of the engine section 13 housed in the engine block 11 as seen from the front.

[0035] The engine section 13 has a first engine section 14, a second engine section 15, a third engine section 16, and a fourth engine section 17. The first engine section 14 and the second engine section 15 form one opposing engine section. The third engine section 16 and the fourth engine section 17 form one opposing engine section. By having multiple opposing engine sections in the engine 10, it is possible to increase the output while ensuring the lightweight and low vibration characteristics of the engine 10.

[0036] The cylinder chamber 12 includes a first cylinder chamber 121 and a second cylinder chamber 122 adjacent to the first cylinder chamber 121. The first cylinder chamber 121 and the second cylinder chamber 122 are adjacent to each other in the left-right direction. In FIG. 4 , the first cylinder chamber 121 and the second cylinder chamber 122 are indicated by dotted lines. A first piston 141 and a second piston 151 are disposed in the first cylinder chamber 121 so as to reciprocate, and are opposed to each other. A third piston 161 and a fourth piston 171 are disposed in the second cylinder chamber 122 so as to reciprocate, and are opposed to each other.

[0037] The first engine section 14 has 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.

[0038] The second engine section 15 is disposed opposite the first engine section 14. The second engine section 15 has 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.

[0039] The third engine section 16 has a third piston 161, a third connecting rod 162, and a third crankshaft 163. The third connecting rod 162 rotatably connects the third piston 161 and the third crankshaft 163.

[0040] The fourth engine section 17 is disposed to face the third engine section 16. The fourth engine section 17 has a fourth piston 171, a fourth connecting rod 172, and a fourth crankshaft 173. The fourth connecting rod 172 rotatably connects the fourth piston 171 and the fourth crankshaft 173.

[0041] The first crankshaft 143 of the first engine section 14 and the third crankshaft 163 of the third engine section 16 are integrally connected to each other. Therefore, the first piston 141 of the first engine section 14 and the third piston 161 of the third engine section 16 reciprocate simultaneously.

[0042] Similarly, the second crankshaft 153 of the second engine section 15 and the fourth crankshaft 173 of the fourth engine section 17 are integrally continuous. Therefore, the second piston 151 of the second crankshaft 153 and the fourth piston 171 of the fourth engine section 17 reciprocate simultaneously.

[0043] The engine section 13 is configured such that an opposed engine section consisting of a first engine section 14 and a second engine section 15 and an opposed engine section consisting of a third engine section 16 and a fourth engine section 17 are arranged side by side in the left-right direction. Furthermore, the first engine section 14 and the third engine section 16 rotate a first crankshaft 143 and a third crankshaft 163. Furthermore, the second engine section 15 and the fourth engine section 17 rotate a second crankshaft 153 and a fourth crankshaft 173. With this configuration, a large amount of power can be generated even in a compact configuration.

[0044] The first engine section 14 and the second engine section 15 of the engine section 13 configured as described above operate as follows. First, during the intake stroke, the first piston 141 and the second piston 151 move from the center toward the outside inside the first cylinder chamber 121, introducing a mixture of fuel and air into the first cylinder chamber 121. Next, during the compression stroke, the inertia of the rotating first crankshaft 143 and the second crankshaft 153 pushes the first piston 141 and the second piston 151 toward the center, compressing the mixture inside the first cylinder chamber 121. Next, during the combustion stroke, an ignition plug (not shown) ignites in the first cylinder chamber 121, burning the mixture inside the first cylinder chamber 121, thereby pushing the first piston 141 and the second piston 151 to the outer ends, which are at bottom dead center. Then, during the exhaust stroke, the inertia of the rotating first crankshaft 143 and second crankshaft 153 pushes the first piston 141 and second piston 151 inward, and the burned gas present inside the first cylinder chamber 121 is expelled to the outside.

[0045] The same operation is performed for the third engine section 16 and the fourth engine section 17 .

[0046] In the engine section 13, the stroke can be divided between the two pistons, the first piston 141 and the second piston 151, which reciprocate within the single first cylinder chamber 121. This allows for a higher compression ratio of the mixed gas compared to conventional engines. Furthermore, because the first piston 141 and the second piston 151 face each other within the first cylinder chamber 121, the cylinder head required in conventional engines is unnecessary, resulting in a simple and lightweight configuration of the engine section 13. Furthermore, the components constituting the engine section 13, i.e., the first piston 141 and the second piston 151, the first crankshaft 143 and the second crankshaft 153, etc., are arranged opposite each other and operate in an opposing manner. This cancels out vibrations generated by the components of the engine section 13, thereby reducing external vibrations generated by the engine section 13 as a whole. Therefore, by incorporating an engine section 13 having such a structure into a flight device, the flight device can be made smaller, lighter, and with less vibration. In particular, the reduced vibration can prevent adverse effects on precision equipment such as attitude control, motor output control, and other arithmetic and control devices, GPS sensors, etc. It can also prevent damage to delivery packages transported by the flight device due to vibration.

[0047] The engine unit 13 is equipped with a reverse synchronization mechanism (not shown). The reverse synchronization mechanism reverses the rotational directions of the first crankshaft 143 and the second crankshaft 153. Furthermore, the reverse synchronization mechanism synchronizes the reciprocating motion of the first piston 141 and the second piston 151. Therefore, in the engine unit 13, the first crankshaft 143 and the second crankshaft 153 have opposite rotational directions.

[0048] FIG. 5 is a cross-sectional view taken along the line BB in FIG. 4, showing the wall portion of the engine block 11 that defines the first cylinder chamber 121 and the first extension space 331. As shown in FIG.

[0049] As described above, the first cylinder chamber 121 is a substantially cylindrical space. The first cylinder chamber 121 has a first cylinder chamber front portion 1211 on the front side and a first cylinder chamber rear portion 1212 connected to the rear end of the first cylinder chamber front portion 1211. A first extension space 331 protrudes upward from the top surface of the first cylinder chamber 121 at approximately the center of the first cylinder chamber 121 in the front-to-rear direction. The first cylinder chamber front portion 1211, the first cylinder chamber rear portion 1212, and the first extension space 331 are in communication with each other.

[0050] The first cylinder chamber 121 and the first extension space 331 configured as described above are spaces surrounded by walls formed inside the engine block 11 .

[0051] Specifically, first cylinder chamber front portion 1211 is a substantially cylindrical space surrounded by first cylinder wall portion 1281. First cylinder wall portion 1281 is a cylindrical wall formed inside first engine block 111. The front and rear ends of first cylinder wall portion 1281 are open.

[0052] First cylinder chamber rear portion 1212 is a substantially cylindrical space surrounded by second cylinder wall portion 2282. Second cylinder wall portion 2282 is a cylindrical wall formed inside second engine block 112. The front and rear ends of second cylinder wall portion 2282 are open.

[0053] The first extension space 331 is a space surrounded by the first extension wall portion 1291 and the second extension wall portion 2292. The first extension wall portion 1291 is a generally tongue-shaped portion that extends upward from the upper end portion of the first cylinder wall portion 1281 at the rear end of the first cylinder wall portion 1281. The second extension wall portion 2292 is a generally tongue-shaped portion that extends upward from the upper end portion of the second cylinder wall portion 2282 at the front end of the second cylinder wall portion 2282.

[0054] The first cylinder chamber 121 is a substantially cylindrical space having a first central axis 1213 extending along the front-rear direction. The first cylinder chamber 121 has a first side surface 1214. The first side surface 1214 is a surface formed by the inner surfaces of the first cylinder wall portion 1281 and the second cylinder wall portion 2282. A first extension space 331 extends from the first side surface 1214. Specifically, the first extension space 331 is a space that extends upward in a direction perpendicular to the first central axis 1213 of the first cylinder chamber 121. The first extension space 331 communicates with the first cylinder chamber 121.

[0055] The same applies to the second cylinder chamber 122 described above.

[0056] Fig. 6 is an exploded perspective view showing the fastening structure between the first engine block 111 and the second engine block 112 from the rear. Fig. 7 is an exploded perspective view showing the fastening structure between the first engine block 111 and the second engine block 112 from the front.

[0057] The first cylinder chamber 121 and the second cylinder chamber 122 described above are formed as internal spaces in the first engine block 111 and the second engine block 112. The first engine block 111 and the second engine block 112 are fastened together by fastening members 18. The fastening members 18 are, for example, stud bolts 191 to 199. The stud bolts 191 and the like are steel rods made of metal. The material used for the stud bolts 191 and the like is a metal with sufficient strength, such as iron, stainless steel, titanium, or an alloy thereof.

[0058] Specifically, stud bolts 191, stud bolts 192, stud bolts 193, stud bolts 194, stud bolts 195, stud bolts 196, stud bolts 197, stud bolts 198 and stud bolts 199 are employed as fastening members 18 that fasten first engine block 111 and second engine block 112 together.

[0059] The stud bolt 195 is longer than the stud bolt 191 and the like, which are the other fastening members 18. The lengths of the stud bolts 191 to 199, excluding the stud bolt 195, are approximately the same. The stud bolts 191 to 199, excluding the stud bolt 195, are fastening members that fasten the first engine block 111 and the second engine block 112 together. On the other hand, the stud bolt 195 is a fastening member that fastens the first engine block 111 and the fourth engine block 114 together.

[0060] Referring to Figure 6, the front ends of the stud bolts 191 to 199 are formed with threads, which are screwed into threads formed on the first engine block 111. The threads on the first engine block 111 may be threads formed on the first engine block 111 itself, or may be separately prepared nuts or the like. This also applies to the other engine blocks. First fastening holes 281 to 289 are formed on the rear surface of the first engine block 111, into which the front ends of the stud bolts 191 to 199 are inserted. The configuration of the first fastening holes 281 to 289 will be described below with reference to Figure 8A.

[0061] 7, the rear ends of the stud bolts 191 to 199 are threaded and are screwed into threads formed on the second engine block 112. The threads on the second engine block 112 may be threads formed on the second engine block 112 itself, or may be separately prepared nuts or the like. Second fastening holes 291 to 299 are formed on the front surface of the second engine block 112, into which the rear ends of the stud bolts 191 to 199 are inserted. The configuration of the second fastening holes 291 to 299 will be described below with reference to FIG. 8B.

[0062] FIG. 8A is a diagram showing the contact surface, which is the rear surface of the first engine block 111.

[0063] As described above, the first engine block 111 has a cavity formed in front of the first cylinder chamber 121 and the second cylinder chamber 122. The rear surface of the first engine block 111 has first fastening holes 281 to 289 formed therein, into which the stud bolts 191 to 199 described above are inserted.

[0064] The first fastening holes 281, 282, and 283 are formed on the left side of the first cylinder chamber 121 and are arranged in this order from above. The first fastening holes 284, 285, and 286 are arranged between the first cylinder chamber 121 and the second cylinder chamber 122 in the left-right direction and are arranged in this order from above. In particular, the first fastening hole 285 is also arranged between the first cylinder chamber 121 and the second cylinder chamber 122 in the up-down direction. The first fastening holes 287, 288, and 289 are formed on the right side of the first cylinder chamber 121 and the second cylinder chamber 122 and are arranged in this order from above.

[0065] A connecting passage 243 opens into the rear surface of the first engine block 111. A plurality of connecting passages 243 are formed on the periphery of the rear surface of the first engine block 111 so as to surround the first cylinder chamber 121 and the second cylinder chamber 122. As will be described later, the connecting passages 243 are part of the cooling passages 24 formed inside the engine block 11.

[0066] The first cooling flow path 241 is part of the cooling flow path 24 described below, and is formed between the first cylinder chamber 121 and the second cylinder chamber 122 in the left-right direction. The first cooling flow path 241 is formed to be elongated in the up-down direction. The upper and lower ends of the first cooling flow path 241 are wide. The middle portion of the first cooling flow path 241 is narrower than the upper and lower ends. This allows for effective heat exchange between the first cylinder chamber 121 and the second cylinder chamber 122 and the first cooling flow path 241 when the engine 10 is operating.

[0067] A first fastening hole 285 is disposed inside the first cooling flow passage 241. That is, the first cooling flow passage 241, in which the stud bolt 195, which is the fastening member 18 described above, is disposed, is formed between the first cylinder chamber 121 and the second cylinder chamber 122. Specifically, the first fastening hole 285 is formed inside the first cooling flow passage 241, on the far side (front side).

[0068] 8B is a diagram showing the contact surface, which is the front surface of the second engine block 112. The front surface of the second engine block 112 comes into close contact with the rear surface of the first engine block 111 described above.

[0069] The second engine block 112 has a cavity formed at the rear of the first cylinder chamber 121 and the second cylinder chamber 122. The front surface of the second engine block 112 has second fastening holes 291 to 299 formed therein, into which the stud bolts 191 to 199 are inserted.

[0070] The second fastening holes 291, 292, and 293 are formed on the left side of the first cylinder chamber 121 and are arranged in this order from above. The second fastening holes 294, 295, and 296 are arranged between the first cylinder chamber 121 and the second cylinder chamber 122 in the left-right direction and are arranged in this order from above. In particular, the second fastening hole 295 is also arranged between the first cylinder chamber 121 and the second cylinder chamber 122 in the up-down direction. The second fastening holes 297, 298, and 299 are formed on the right side of the first cylinder chamber 121 and the second cylinder chamber 122 and are arranged in this order from above.

[0071] A connecting passage 243 opens into the front surface of the second engine block 112. As will be described later, the connecting passage 243 is part of the cooling passage 24 formed inside the engine block 11. A plurality of connecting passages 243 are formed on the periphery of the front surface of the second engine block 112 so as to surround the first cylinder chamber 121 and the second cylinder chamber 122.

[0072] The second cooling flow path 242 is part of the cooling flow path 24 described below, and is formed between the first cylinder chamber 121 and the second cylinder chamber 122 in the left-right direction. The second cooling flow path 242 is formed to be elongated in the up-down direction. The upper and lower ends of the second cooling flow path 242 are wide. The middle portion of the second cooling flow path 242 is narrower than the upper and lower ends. This allows for effective heat exchange between the first cylinder chamber 121 and the second cylinder chamber 122 and the second cooling flow path 242 when the engine 10 is operating.

[0073] A second fastening hole 295 is disposed inside the second cooling flow passage 242. That is, the portion of the second cooling flow passage 242 where the stud bolt 195, which is the fastening member 18 described above, is disposed is formed between the first cylinder chamber 121 and the second cylinder chamber 122. Specifically, the second fastening hole 295 is formed inside the second fastening hole 292, on the far side (rear side).

[0074] 9A is a perspective view showing the stud bolt 195 and the O-ring 21 from the front. Here, a first O-ring 211 is shown as the first seal member, and a second O-ring 212 is shown as the second seal member.

[0075] As described above, threads are formed on the front and rear ends of the stud bolt 195. Additionally, an O-ring 21 serving as a seal member 20 is attached to the front end of the stud bolt 195. The O-rings 21 include a first O-ring 211 and a second O-ring 212. The first O-ring 211 and the second O-ring 212 are made of synthetic resin or rubber molded into a ring shape and function to prevent the intrusion of the cooling fluid 23, which will be described later.

[0076] FIG. 9B is an exploded perspective view showing the stud bolt 195 and the O-ring 21 from the front.

[0077] A first enlarged diameter portion 26 and a second enlarged diameter portion 27 are formed on the front end side of the stud bolt 195. The first enlarged diameter portion 26 and the second enlarged diameter portion 27 are portions of the stud bolt 195 that are partially raised radially outward. The first enlarged diameter portion 26 and the second enlarged diameter portion 27 are formed in a roughly ring shape around the stud bolt 195.

[0078] The first enlarged diameter portions 26 are formed in pairs close to each other. A first O-ring 211 is fitted between the first enlarged diameter portions 26.

[0079] The second enlarged diameter portions 27 are formed close to each other. A second O-ring 212 is fitted between the second enlarged diameter portions 27.

[0080] 10 is a cross-sectional view showing a schematic configuration of the cooling flow passage 24, etc. Here, the boundary 25 between the first engine block 111 and the second engine block 112 is shown by a dotted line.

[0081] As described above, the engine block 11 includes a first engine block 111 , a second engine block 112 , a third engine block 113 , and a fourth engine block 114 .

[0082] The second cylinder chamber 122 is a space formed by joining the first engine block 111 and the second engine block 112. As described above, while the engine 10 is operating, the third piston 161 and the fourth piston 171 reciprocate inside the second cylinder chamber 122. Here, the third piston 161 and the fourth piston 171 reach their inner dead centers, thereby compressing the combustion chamber 34 formed inside the second cylinder chamber 122.

[0083] The cooling flow path 24 is a space formed near the cylinder chamber 12 and through which the cooling fluid 23 flows. The cooling flow path 24 is configured to cool the first cylinder chamber 121 and the second cylinder chamber 122. Here, a configuration is illustrated in which the cooling flow path 24 surrounds the second cylinder chamber 122. Similarly, the first cylinder chamber 121 described above is also surrounded by the cooling flow path 24.

[0084] The cooling flow path 24 includes a first cooling flow path 241 , a second cooling flow path 242 , and a connecting flow path 243 .

[0085] The first cooling channel 241 is a cavity formed in a thick portion of the first engine block 111. The first cooling channel 241 is formed to surround the front portion of the second cylinder chamber 122. The first cooling channel 241 communicates with the outside via an outlet portion 245.

[0086] The second cooling flow path 242 is a cavity formed in a thick portion of the second engine block 112. The second cooling flow path 242 is formed to surround the rear portion of the second cylinder chamber 122. The second cooling flow path 242 communicates with the outside via an inlet 244.

[0087] The connection flow path 243 is a space that communicates with the first cooling flow path 241 and the second cooling flow path 242 at the boundary 25 .

[0088] When the engine 10 is operating, the cooling fluid 23 is introduced through the inlet 244, flows through the second cooling passage 242, the connecting passage 243, and the first cooling passage 241, receives heat from the second cylinder chamber 122, and is discharged to the outside through the outlet 245. As the cooling fluid 23, a fluid with a high specific heat capacity, such as water, can be used.

[0089] Here, with respect to the second cylinder chamber 122 described above, a first cooling flow path 241, a second cooling flow path 242, and a connecting flow path 243 are formed so as to surround the second cylinder chamber 122 described above in the same manner as above.

[0090] 11 is a cross-sectional view showing a configuration in which the stud bolt 195 penetrates the cooling flow passage 24. This cross-sectional view is taken along the line AA shown in FIG.

[0091] As described above, a first cooling passage 241 is formed inside the first engine block 111, and a second cooling passage 242 is formed inside the second cylinder chamber 122, and the first cooling passage 241 and the second cooling passage 242 are connected by a connecting passage 243.

[0092] The stud bolt 195 is disposed to pass through the first cooling passage 241, the second cooling passage 242, and the connecting passage 243. The front end of the stud bolt 195 is disposed inside the first fastening hole 285 of the first engine block 111. The middle portion of the stud bolt 195 is disposed in the second fastening hole 295 of the second cylinder chamber 122.

[0093] In this configuration, the first and second fastening holes 285, 295 communicate with the cooling flow passage 24. A gap, even if small, is formed between the first and second fastening holes 285, 295 and the stud bolt 195. Therefore, unless some countermeasure is taken, there is a risk that the cooling fluid 23 present inside the cooling flow passage 24 will leak to the outside through the gap.

[0094] In this embodiment, the aforementioned seal member 20 prevents the cooling fluid 23 from leaking out. Specifically, the seal member 20 is disposed on the stud bolt 195 in areas A and B shown in Figure 11. This will be described later with reference to Figures 12A and 12B.

[0095] 12A is a cross-sectional view showing the relationship between the first fastening hole 285 and the stud bolt 195. FIG. 12A shows area A in FIG.

[0096] A first O-ring 211 is interposed in the gap between the stud bolt 195 and the first fastening hole 285. As described above, the stud bolt 195 has first enlarged diameter portions 26, and the first O-ring 211 is formed between the first enlarged diameter portions 26. The diameter of the first O-ring 211 in an uncompressed state is longer than the protruding height of the first enlarged diameter portions 26. Therefore, when the stud bolt 195 where the first O-ring 211 is located is inserted into the first fastening hole 285, the first O-ring 211 is compressed between the stud bolt 195 and the inner wall of the first fastening hole 285. This seals the gap between the stud bolt 195 and the first fastening hole 285. Therefore, the first O-ring 211 prevents the cooling fluid 23 from entering from the first cooling flow path 241 between the stud bolt 195 and the first fastening hole 285. Additionally, the first fastening hole 285 has an expanded diameter near the rear of the first engine block 111. The first expanded diameter portion 26 and the first O-ring 211 are disposed in the expanded diameter portion of the first fastening hole 285.

[0097] 12B is a cross-sectional view showing the relationship between the second fastening hole 295 and the stud bolt 195. FIG. 12B shows region B in FIG.

[0098] A second O-ring 212 is interposed in the gap between the stud bolt 195 and the second engine block 112. As described above, the stud bolt 195 has second enlarged diameter portions 27, and the second O-ring 212 is formed between the second enlarged diameter portions 27. The diameter of the second O-ring 212 in an uncompressed state is longer than the protruding height of the second enlarged diameter portions 27. Therefore, when the stud bolt 195 where the second O-ring 212 is located is inserted into the second fastening hole 295, the second O-ring 212 is compressed between the stud bolt 195 and the inner wall of the second fastening hole 295. This seals the gap between the stud bolt 195 and the second fastening hole 295. Therefore, the second O-ring 212 prevents the cooling fluid 23 from entering from the second cooling flow path 242 between the stud bolt 195 and the second fastening hole 295. Additionally, the second fastening hole 295 has an increased diameter near the front of the second engine block 112. The second increased diameter portion 27 and the second O-ring 212 are disposed in the increased diameter portion of the second fastening hole 295.

[0099] Fig. 13A is a perspective view showing the stud bolt 195 and the cooling flow passage 24 from the rear. Fig. 13B is a perspective view showing the stud bolt 195 and the cooling flow passage 24 from the front.

[0100] 13A and 13B, a first cooling flow path 241, a second cooling flow path 242, and a part of a connecting flow path 243 are disposed between a first cylinder chamber 121 and a second cylinder chamber 122.

[0101] The stud bolt 195 is disposed between the first cylinder chamber 121 and the second cylinder chamber 122, penetrating the first cooling flow path 241, the second cooling flow path 242, and the connecting flow path 243. In this manner, the cooling flow path 24 also serves as an area for arranging the stud bolt 195. This allows the first cylinder chamber 121 and the second cylinder chamber 122 to be closer to each other, thereby achieving a more compact engine 10. As described above, the first O-ring 211 and the second O-ring 212 are attached to the stud bolt 195. Therefore, even though the stud bolt 195 is configured to penetrate the cooling flow path 24, the cooling fluid 23 flowing through the cooling flow path 24 is prevented from leaking out along the stud bolt 195 to the outside.

[0102] Although the embodiments of the present invention have been described above, the present invention is not limited to these and can be modified within the scope of the present invention. In addition, the above-described embodiments can be combined with each other.

[0103] For example, although the engine 10 described above has a plurality of cylinder chambers 12, the number of cylinder chambers 12 may be one.

[0104] 10 Engine 11 Engine block 111 First engine block 112 Second engine block 113 Third engine block 114 Fourth engine block 12 Cylinder chamber 121 First cylinder chamber 122 Second cylinder chamber 1213 First central axis 1214 First side surface 1291 First extending wall portion 1281 First cylinder wall portion 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 16 Third engine section 161 Third piston 162 Third connecting rod 163 Third crankshaft 17 Fourth engine section 171 Fourth piston 172 Fourth connecting rod 173 Fourth crankshaft 18 Fastening member 191 Stud bolt 192 Stud bolt 193 Stud bolt 194 Stud bolt 195 Stud bolt 196 Stud bolt 197 Stud bolt 198 Stud bolt 199 Stud bolt 20 Sealing member 21 O-ring 211 First O-ring 212 Second O-ring 2282 Second cylinder wall portion 2292 Second extension wall portion 23 Cooling fluid 24 Cooling flow path 241 First cooling flow path 242 Second cooling flow path 243 Connecting flow path 244 Inlet portion 245 Outlet portion 25 Boundary 26 First enlarged diameter portion 27 Second enlarged diameter portion 281 First fastening hole 282 First fastening hole 283 First fastening hole 284 First fastening hole 285 First fastening hole 286 First fastening hole 287 First fastening hole 288 First fastening hole 289 First fastening hole 291 Second fastening hole 292 Second fastening hole 293 Second fastening hole 294 Second fastening hole 295 Second fastening hole 296 Second fastening hole 297 Second fastening hole 298 Second fastening hole 299 Second fastening hole 30 Crank holder 31 Crank holder 32 Crank holder 33 Crank holder 34 Combustion chamber

Claims

1. An engine comprising a cylinder chamber formed by multiple engine blocks, and a cooling flow passage formed near the cylinder chamber through which a cooling fluid flows, wherein a part of a fastening member that fastens the engine blocks together is disposed in the cooling flow passage.

2. The engine described in claim 1, wherein the engine block has a first engine block and a second engine block fastened to the first engine block by the fastening members, the cylinder chamber has a first cylinder chamber and a second cylinder chamber adjacent to the first cylinder chamber, pistons arranged opposite to each other are arranged to reciprocate inside the first cylinder chamber, and pistons arranged opposite to each other are arranged to reciprocate inside the second cylinder chamber, the cooling flow path is configured to cool the first cylinder chamber and the second cylinder chamber, the first cylinder chamber and the second cylinder chamber are spaces formed by joining the first engine block and the second engine block, and a part of the fastening members is disposed in the cooling flow path.

3. The engine according to claim 1, further comprising a seal member interposed between said fastening member and said engine block.

4. The engine according to claim 2, wherein a seal member is interposed between the fastening member and the first engine block and between the fastening member and the second engine block.

5. The engine described in claim 4, characterized in that the first engine block has a first cooling flow passage that is a part of the cooling flow passage, and a first fastening hole that is connected to the first cooling flow passage and through which the fastening member is inserted; the second engine block has a second cooling flow passage that is another part of the cooling flow passage, and a second fastening hole that is connected to the second cooling flow passage and through which the fastening member is inserted; the sealing member has a first sealing member and a second sealing member, the first sealing member is interposed between the fastening member and the first fastening hole, and the second sealing member is interposed between the fastening member and the second fastening hole.

6. The engine according to claim 2, wherein the cooling passage in the portion where the fastening member is disposed is formed between the first cylinder chamber and the second cylinder chamber.

7. An engine according to claim 3 or 4, characterized in that the fastening member is a stud bolt, and the sealing member is an O-ring.

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