Engine

Abstract

Provided is an engine in which it is possible to optimize valves in the vicinity of cylinder chambers and an advancing and retracting mechanism of the valves.　An engine 10 comprises cylinder chambers 12, intake valves 18, exhaust valves 19, and an advancing and retracting mechanism 20 for advancing and retracting the intake valves 18 and the exhaust valves 19. The advancing and retracting mechanism 20 has a camshaft 21, exhaust cams 22, intake cams 23, pushrods 24, and rocker arms 25. The intake cams 23 are fixed to the camshaft 21 and are configured to advance and retract the intake valves 18. The exhaust cams 22 are configured to advance and retract the pushrods 24. The rocker arms 25 are rotated by the pushrods 24 and are configured to advance and retract the exhaust valves 19.

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 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 that extends laterally from the combustion chamber. A spark plug is provided in this extension.

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

[0006] However, the opposed-piston engines described in the aforementioned patent documents have room for improvement in terms of optimizing the advancing and retreating mechanism that controls the advancing and retreating movement of the valves.

[0007] Specifically, in the opposed-piston engine described in Patent Document 3, when the pistons reciprocate in the front-to-rear direction, the intake valves and exhaust valves are arranged in a concentrated manner in front of or behind the extension portion. Furthermore, the advancing and retracting mechanisms for the intake valves and exhaust valves are also arranged near the intake valves and exhaust valves. This creates a problem of a complex mechanical configuration around the extension portion.

[0008] Furthermore, if an opposed-piston engine is provided with a plurality of cylinder chambers in order to increase power output, the above-mentioned problems become more apparent.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide an engine in which the valve and its advance / retract mechanism in the vicinity of the cylinder chamber can be optimized.

[0010] The engine of the present invention comprises a cylinder chamber, an intake valve, an exhaust valve, and an advancing / retracting mechanism that advances and retracts the intake valve and the exhaust valve, the advancing / retracting mechanism having a camshaft, a first cam, a second cam, a push rod, and a rocker arm, the first cam is fixed to the camshaft and configured to advance and retract either the intake valve or the exhaust valve, the second cam is separate from the first cam and configured to advance and retract the push rod, and the rocker arm is rotated by the push rod and configured to advance and retract the other of the intake valve and the exhaust valve.

[0011] In the engine of the present invention, the first cam advances and retracts the intake valves, and the second cam advances and retracts the exhaust valves via the push rod.

[0012] In addition, in the engine of the present invention, when the axial direction of the cylinder chamber is the front-to-rear direction, pistons arranged opposite each other along the front-to-rear direction are arranged so as to reciprocate inside the cylinder chamber, and an extension space is provided extending laterally from the middle of the cylinder chamber in the front-to-rear direction, and the intake valve is arranged so as to be able to move forward and backward into the extension space from the front side, and the exhaust valve is arranged so as to be able to move forward and backward into the extension space from the rear side.

[0013] In the engine of the present invention, the cylinder chamber has a first cylinder chamber and a second cylinder chamber adjacent to the first cylinder chamber, a first piston and a second piston are housed in the first cylinder chamber so as to reciprocate, a third piston and a fourth piston are housed in the second cylinder chamber so as to reciprocate, a first extension space is provided extending laterally from a middle portion of the first cylinder chamber in the front-rear direction, and a second extension space is provided extending laterally from a middle portion of the second cylinder chamber in the front-rear direction. The exhaust valve has a first exhaust valve and a second exhaust valve, the first intake valve being movable forward and backward into the first extension space from the front side, the first exhaust valve being movable forward and backward into the first extension space from the rear side, the second intake valve being movable forward and backward into the second extension space from the front side, and the second exhaust valve being movable forward and backward into the second extension space from the rear side.

[0014] In addition, in the engine of the present invention, the number of intake valves is greater than the number of exhaust valves, and the spark plug is arranged so as to be exposed on the side of the extension space where the exhaust valve is provided.

[0015] The present invention relates to an engine including a cylinder chamber, an intake valve, an exhaust valve, and an advancing / retracting mechanism for advancing and retracting the intake valve and the exhaust valve, the advancing / retracting mechanism including a camshaft, a first cam, a second cam, a pushrod, and a rocker arm, the first cam being fixed to the camshaft and configured to advance and retract either the intake valve or the exhaust valve, the second cam being separate from the first cam and configured to advance and retract the pushrod, and the rocker arm being rotated by the pushrod to advance and retract the other of the intake valve and the exhaust valve. According to the engine of the present invention, by advancing and retracting either the intake valve or the exhaust valve with the first cam and advancing and retracting the other of the intake valve and the exhaust valve with the pushrod, the advancing / retracting mechanism can be located near the cylinder even when there are strict geometric constraints near the cylinder. Furthermore, the use of push rods reduces the number of camshafts, thereby simplifying the engine configuration.

[0016] In the engine of the present invention, the first cam advances and retracts the intake valves, and the second cam advances and retracts the exhaust valve via the push rod. According to the engine of the present invention, the advance / retract mechanisms for advancing and retracting the intake valves and the exhaust valves can be integrated into a limited space.

[0017] In the engine of the present invention, when the axial direction of the cylinder chamber is defined as the front-rear direction, pistons arranged opposite each other along the front-rear direction are arranged so as to reciprocate inside the cylinder chamber, an extension space is provided extending laterally from a middle portion of the cylinder chamber in the front-rear direction, the intake valve is provided so as to be able to advance and retreat into the extension space from the front side, and the exhaust valve is provided so as to be able to advance and retreat into the extension space from the rear side. According to the engine of the present invention, the intake valve and the exhaust valve are arranged on either side of the extension space, so that the intake valve and the exhaust valve are closely arranged, but because the intake valve or the exhaust valve is advanced and retreated via a push rod, the configuration around the extension space can be simplified.

[0018] In the engine of the present invention, the cylinder chamber has a first cylinder chamber and a second cylinder chamber adjacent to the first cylinder chamber, a first piston and a second piston are housed in the first cylinder chamber so as to reciprocate, a third piston and a fourth piston are housed in the second cylinder chamber so as to reciprocate, a first extension space is provided extending laterally from a middle portion of the first cylinder chamber in the front-rear direction, and a second extension space is provided extending laterally from a middle portion of the second cylinder chamber in the front-rear direction. The engine of the present invention has two extension spaces, the intake valves have a first intake valve and a second intake valve, and the exhaust valves have a first exhaust valve and a second exhaust valve, the first intake valve is movable forward and backward into the first extension space from a front side, the first exhaust valve is movable forward and backward into the first extension space from a rear side, the second intake valve is movable forward and backward into the second extension space from a front side, and the second exhaust valve is movable forward and backward into the second extension space from a rear side. According to the engine of the present invention, even when a plurality of cylinder chambers are adjacent to each other and a large number of intake valves and exhaust valves are arranged, the overall configuration of the engine can be simplified by optimizing the configuration of the camshaft and push rod.

[0019] In the engine of the present invention, the number of intake valves is greater than the number of exhaust valves, and the spark plug is disposed so as to be exposed on the side of the extension space where the exhaust valves are provided. According to the engine of the present invention, the spark plug is exposed to the extension space from the side where the fewer exhaust valves are provided, thereby making effective use of the space around the extension space.

[0020] FIG. 1 is a perspective view of an engine according to an embodiment of the present invention. FIG. 1 is a perspective view of an engine according to an embodiment of the present invention, showing a first engine block. FIG. 2 is a perspective view of an engine according to an embodiment of the present invention, showing a second engine block. FIG. 3 is a perspective view of an engine according to an embodiment of the present invention, showing a first abutment surface of a first engine block. FIG. 4 is a perspective view of an engine according to an embodiment of the present invention, showing a second abutment surface of a second engine block. FIG. 5 is a perspective view of an engine according to an embodiment of the present invention, showing engine parts, etc. FIG. 6 is a perspective view of an engine according to an embodiment of the present invention, showing a valve and an advancing / retracting mechanism. FIG. 7 is an exploded perspective view of an engine according to an embodiment of the present invention, showing a valve and an advancing / retracting mechanism. FIG. 8 is a perspective view of an engine according to an embodiment of the present invention, showing a second cylinder chamber, a second extension space, etc., as viewed from the rear. FIG. 9 is a perspective view of an engine according to an embodiment of the present invention, showing a second cylinder chamber, a second extension space, etc., as viewed from the front. FIG. 10 is a cross-sectional view of an engine according to an embodiment of the present invention, showing a wall portion of the engine block that forms the cylinder chamber and the extension space.

[0021] 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 a piston (described later) reciprocates along the axial direction of a cylinder chamber (described later). The left-right direction refers to the direction in which cylinder spaces (described later) are arranged. In the following description, identical 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 configuration, such as a crankshaft rotation synchronization mechanism, a lubricating oil supply mechanism, a fuel supply mechanism, and electrical components, are not illustrated.

[0022] FIG. 1 is a perspective view showing an engine 10. As shown in FIG.

[0023] The engine 10 is an opposed-piston engine having a plurality of pistons arranged in opposing positions. The internal configuration and operation of the engine 10 will be described later with reference to Figure 2A and subsequent figures.

[0024] 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 drives a motor, which in turn drives a rotor, thereby generating lift to keep the drone afloat. A parallel hybrid drone is a drone in which a main rotor is mechanically rotated by the engine 10, and the lift generated by the rotation of the main rotor keeps the drone afloat. The engine 10 of this embodiment is an opposed-piston engine, and is lightweight and low-vibration, making it particularly suitable as a drive source for series hybrid drones, parallel hybrid drones, and the like.

[0025] Specifically, engine 10 includes a cylinder chamber 12, an intake valve 18, an exhaust valve 19, and an advance / retract mechanism 20. These components of engine 10 are housed in an engine block 11. The configuration of cylinder chamber 12 will be described with reference to Figure 4 and other figures. The intake valve 18, exhaust valve 19, and advance / retract mechanism 20 will be described with reference to Figure 5 and other figures.

[0026] The engine 10 also has an engine block 11, which is its main body. 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 such as stud bolts (not shown).

[0027] 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.

[0028] A second spark plug 262 is attached to the right side of the engine block 11. Similarly, a first spark plug 261 (not shown) is attached to the left side of the engine block 11. Furthermore, a belt 32 and a driven gear 30 for driving a reciprocating mechanism 20 (described later) are disposed on the left side of the engine block 11. These devices will be described later with reference to Figure 5 and subsequent figures.

[0029] FIG. 2A is a perspective view showing the first engine block 111.

[0030] 2A, the rearward facing surface of the first engine block 111 is defined as a first contact surface 40. The first contact surface 40 is a flat surface that comes into contact with a second contact surface 41 of the second engine block 112, which will be described later.

[0031] The first engine block 111 has a first cylinder chamber front portion 1211 and a second cylinder chamber front portion 1221 formed forward from the first abutment surface 40. The first cylinder chamber front portion 1211 and the second cylinder chamber front portion 1221 are adjacent to each other in the left-right direction. The first cylinder chamber front portion 1211 is a substantially cylindrical space and forms the front portion of the first cylinder chamber 121, which will be described later. The second cylinder chamber front portion 1221 is a substantially cylindrical space and forms the front portion of the second cylinder chamber 122, which will be described later.

[0032] The first extension space front portion 3311 is a portion of the first contact surface 40 recessed forward, and is continuous with the upper end of the first cylinder chamber front portion 1211. The first extension space front portion 3311 constitutes a first extension space 331, which will be described later.

[0033] The second extension space front portion 3321 is a portion of the first contact surface 40 recessed forward, and is continuous with the upper end of the second cylinder chamber front portion 1221. The second extension space front portion 3321 constitutes a second extension space 332, which will be described later.

[0034] 2B , the surface of the second engine block 112 facing forward is the second abutment surface 41. The second abutment surface 41 is a flat surface that abuts against the first abutment surface 40 of the first engine block 111 described above.

[0035] The second engine block 112 has a first cylinder chamber rear portion 1212 and a second cylinder chamber rear portion 1222 formed rearward from the second abutment surface 41. The first cylinder chamber rear portion 1212 and the second cylinder chamber rear portion 1222 are adjacent to each other in the left-right direction. The first cylinder chamber rear portion 1212 is a substantially cylindrical space and forms the rear portion of the first cylinder chamber 121, which will be described later. The second cylinder chamber rear portion 1222 is a substantially cylindrical space and forms the rear portion of the second cylinder chamber 122, which will be described later.

[0036] The first extension space rear portion 3312 is a portion of the second abutment surface 41 recessed rearward, and is continuous with the upper end of the first cylinder chamber rear portion 1212. The first extension space rear portion 3312, together with the first extension space front portion 3311 described above, constitutes the first extension space 331, which will be described later.

[0037] The second extension space rear portion 3322 is a portion where the second abutment surface 41 is recessed rearward, and is continuous with the upper end of the second cylinder chamber rear portion 1222. The second extension space rear portion 3322, together with the second extension space front portion 3321 described above, constitutes the second extension space 332, which will be described later.

[0038] 3A is a diagram showing the first contact surface 40 of the first engine block 111. The first contact surface 40 is formed with an intake valve mounting hole 35. The intake valve mounting hole 35 has a first intake valve mounting hole 351 and a second intake valve mounting hole 352.

[0039] Two first intake valve mounting holes 351 are formed inside the first extension space front portion 3311. The first intake valve mounting holes 351 are circular through-holes that penetrate the wall portion of the first engine block 111 in the front-to-rear direction. A first intake valve 181 (described later) is disposed in each of the first intake valve mounting holes 351.

[0040] Two second intake valve mounting holes 352 are formed inside the second extension space front portion 3321. The second intake valve mounting holes 352 are circular through-holes that penetrate a wall formed inside the first engine block 111. A second intake valve 182, which will be described later, is disposed in each of the second intake valve mounting holes 352.

[0041] 3B is a diagram showing the second contact surface 41 of the second engine block 112. The second contact surface 41 is formed with an exhaust valve mounting hole 36 and a plug mounting hole 37. The exhaust valve mounting hole 36 has a first exhaust valve mounting hole 361 and a second exhaust valve mounting hole 362. The plug mounting hole 37 has a first plug mounting hole 371 and a second plug mounting hole 372.

[0042] The first exhaust valve installation hole 361 is a hole formed in the first extension space rear portion 3312. The first exhaust valve installation hole 361 passes through a circular wall formed inside the second engine block 112. A first exhaust valve 191, which will be described later, is disposed in the first exhaust valve installation hole 361.

[0043] The first plug installation hole 371 is a through-hole formed inside the rear portion of the first extension space 3312. The first plug installation hole 371 is a through-hole that penetrates the left side surface of the second engine block 112. That is, the front end of the first plug installation hole 371 opens into the rear portion of the first extension space 3312. The rear end of the first plug installation hole 371 opens to the outside from the left side surface of the second engine block 112. A front end of a first spark plug 261 (described later) is inserted into the first plug installation hole 371.

[0044] The second exhaust valve installation hole 362 is a hole formed in the second extension space rear portion 3322. The second exhaust valve installation hole 362 passes through a circular wall formed inside the second engine block 112. A second exhaust valve 192, which will be described later, is disposed in the second exhaust valve installation hole 362.

[0045] The second plug installation hole 372 is a through-hole formed inside the second extension space rear portion 3322. The second plug installation hole 372 is a through-hole that penetrates the right side surface of the second engine block 112. That is, the front end of the second plug installation hole 372 opens into the second extension space rear portion 3322. The rear end of the second plug installation hole 372 opens to the outside from the right side surface of the second engine block 112. The front end of a second spark plug 262, which will be described later, is inserted into the second plug installation hole 372.

[0046] FIG. 4 is a perspective view of the engine section 13 built into the engine block 11 as viewed from above on the front side.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Similarly, the second crankshaft 153 of the second engine section 15 and the fourth crankshaft 173 of the fourth engine section 17 are integrally connected. Therefore, the second piston 151 of the second engine section 15 and the fourth piston 171 of the fourth engine section 17 reciprocate simultaneously.

[0055] 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.

[0056] The extension space 33 is a space that extends upward, i.e., laterally, from a central portion of the cylinder chamber 12 in the front-to-rear direction. The extension space 33 has a first extension space 331 and a second extension space 332. The first extension space 331 is a space that extends upward from a central portion of the first cylinder chamber 121 in the front-to-rear direction. The second extension space 332 is a space that extends upward from a central portion of the second cylinder chamber 122 in the front-to-rear direction. The first extension space 331 and the second extension space 332 are portions in which various valves and plugs are installed, as described below. The specific shape of the extension space 33 is shown in FIG. 7A etc.

[0057] The combustion chamber 34 is a space sandwiched between the pistons inside the cylinder chamber 12. The combustion chamber 34 has a first combustion chamber 341 and a second combustion chamber 342. The first combustion chamber 341 is a space sandwiched between the first piston 141 and the second piston 151 inside the first cylinder chamber 121, where the air-fuel mixture is burned. The first combustion chamber 341 is continuous with the first extension space 331. The second combustion chamber 342 is a space sandwiched between the third piston 161 and the fourth piston 171 inside the second cylinder chamber 122, where the air-fuel mixture is burned. The second combustion chamber 342 is continuous with the second extension space 332.

[0058] Fig. 5 is a perspective view showing the valves and the advancing / retracting mechanism 20. Fig. 6 is an exploded perspective view showing the valves and the advancing / retracting mechanism 20.

[0059] 5 and 6, the advancing / retreating mechanism 20 is a mechanism for advancing and retracting the intake valve 18 and the exhaust valve 19 arranged near the extension space 33 described above.

[0060] The intake valve 18 includes a first intake valve 181 and a second intake valve 182 .

[0061] The first intake valves 181 are provided so as to be movable forward and backward relative to the first extension space 331 from the front side. Two first intake valves 181 are provided here. Each first intake valve 181 is attached to a first intake valve installation hole 351 shown in FIG. 3A. The first intake valves 181 are used to draw an air-fuel mixture into the first cylinder chamber 121 shown in FIG. 4. A spring 381 is attached to each first intake valve 181. The spring 381 biases the first intake valve 181 forward.

[0062] The second intake valves 182 are provided so as to be movable forward and backward relative to the second extension space 332 from the front side. Two second intake valves 182 are provided here. Each second intake valve 182 is attached to a second intake valve installation hole 352 shown in FIG. 3A. The second intake valves 182 are used to draw an air-fuel mixture into the second cylinder chamber 122 shown in FIG. 4. A spring 382 is attached to each second intake valve 182. The spring 382 biases the second intake valve 182 forward.

[0063] The exhaust valve 19 includes a first exhaust valve 191 and a second exhaust valve 192 .

[0064] The first exhaust valve 191 is provided so as to be movable toward and away from the first extension space 331 from the rear side. One first exhaust valve 191 is provided here. The first exhaust valve 191 is attached to the first exhaust valve installation hole 361 shown in FIG. 3B. The first exhaust valve 191 is for exhausting the air-fuel mixture from the first cylinder chamber 121 shown in FIG. 4. A spring 383 is provided in the first exhaust valve 191. The spring 383 biases the first exhaust valve 191 rearward.

[0065] The second exhaust valve 192 is provided so as to be movable toward and away from the second extension space 332 from the rear side. One second exhaust valve 192 is provided here. The second exhaust valve 192 is attached to the second exhaust valve installation hole 362 shown in FIG. 3B. The second exhaust valve 192 is for exhausting the air-fuel mixture from the second cylinder chamber 122 shown in FIG. 4. A spring 384 is provided in the second exhaust valve 192. The spring 384 biases the second exhaust valve 192 rearward.

[0066] The number of intake valves 18 is greater than the number of exhaust valves 19. For example, for the first extension space 331, the number of exhaust valves 19 is one and the number of intake valves 18 is two. According to this embodiment, the spark plug 26 is exposed to the extension space 33 from the side of the exhaust valves 19, which has fewer numbers, so that the space around the extension space 33 can be used effectively.

[0067] The forward / backward movement mechanism 20 mainly includes a camshaft 21, a first cam, a second cam, a push rod 24, and a rocker arm 25. The first cam is, for example, an intake cam 23. The second cam is separate from the first cam and is, for example, an exhaust cam 22.

[0068] The camshaft 21 is a steel rod extending in the left-right direction. A driven gear 30 is connected to the left end of the camshaft 21 so as to be non-rotatable relative to the second crankshaft 153. A crank gear 31 is disposed rearward of the driven gear 30. The crank gear 31 is connected to the second crankshaft 153 so as to be non-rotatable relative to the second crankshaft 153. A belt 32 is stretched between the driven gear 30 and the crank gear 31. Therefore, when the second crankshaft 153 rotates as a result of the engine unit 13 shown in FIG. 4 operating, the camshaft 21 rotates via the belt 32. This allows the intake valve 18 and the exhaust valve 19 to advance and retract at a predetermined timing.

[0069] The intake cam 23 is attached to the camshaft 21 so as to be non-rotatable relative to the camshaft 21, and is configured to move the intake valve 18 forward and backward. The intake cam 23 includes a first intake cam 231 and a second intake cam 232.

[0070] The first intake cam 231 is disposed in front of the first intake valve 181. When the first intake cam 231 rotates, the first intake valve 181 is pushed by the first intake cam 231 and moves forward and backward.

[0071] The second intake cam 232 is disposed in front of the second intake valve 182. When the second intake cam 232 rotates, the second intake valve 182 is pushed by the second intake cam 232 and moves forward and backward.

[0072] The exhaust cam 22 is configured to move the exhaust valve 19 forward and backward via a push rod 24. The exhaust cam 22 has a first exhaust cam 221 and a second exhaust cam 222. The exhaust cam 22 is disposed outward of the intake cam 23 in the left-right direction.

[0073] The first exhaust cam 221 is disposed on the camshaft 21 to the left of the first intake cam 231. As will be described later, the rotation of the first exhaust cam 221 causes the first exhaust valve 191 to advance and retreat via the first push rod 241 and the first rocker arm 251.

[0074] The second exhaust cam 222 is disposed on the camshaft 21 to the right of the second intake cam 232. As will be described later, the rotation of the second exhaust cam 222 causes the second exhaust valve 192 to advance and retreat via the second push rod 242 and the second rocker arm 252.

[0075] The push rod 24 is a steel rod extending in the front-rear direction. The push rod 24 includes a first push rod 241 and a second push rod 242. The push rod 24 is disposed at an end of the advancing / retreating mechanism 20 in the left-right direction.

[0076] The first push rod 241 is disposed to the left of the intake valve 18, the exhaust valve 19, and the extension space 33. The front end of the first push rod 241 abuts against the first exhaust cam 221. The rear end of the first push rod 241 abuts against the upper end of the first rocker arm 251. The first push rod 241 is a member that transmits power generated by the rotation of the first exhaust cam 221 to the first rocker arm 251.

[0077] The second push rod 242 is disposed to the right of the intake valve 18, the exhaust valve 19, and the extension space 33. The front end of the second push rod 242 abuts against the second exhaust cam 222. The rear end of the second push rod 242 abuts against the upper end of the second rocker arm 252. The second push rod 242 is a member that transmits power generated by the rotation of the second exhaust cam 222 to the second rocker arm 252.

[0078] The rocker arm 25 is configured to rotate by the push rod 24 to advance and retract the exhaust valve 19. The rocker arm 25 has a first rocker arm 251 and a second rocker arm 252.

[0079] Referring to Figure 6, the first rocker arm 251 is disposed to be rotatable around its vertically intermediate portion. The upper end of the first rocker arm 251 abuts against the rear end of the first push rod 241. The lower end of the first rocker arm 251 abuts against the rear end of the first exhaust valve 191. The first rocker arm 251 is disposed so as to tilt upward toward the left, which is the outer side in the width direction. This allows the first push rod 241 to be disposed on the left, which is the outer side in the width direction. Therefore, the intake valve 18, the exhaust valve 19, and the spark plug 26 can be disposed in the center of the advancing and retracting mechanism 20 in the width direction.

[0080] The second rocker arm 252 is disposed so as to be rotatable around its vertical middle portion. The upper end of the second rocker arm 252 abuts against the rear end of the second push rod 242. The lower end of the second rocker arm 252 abuts against the rear end of the second exhaust valve 192. The second rocker arm 252 is disposed so as to tilt upward toward the right, which is the outer side in the width direction. In this manner, the second push rod 242 can be disposed to the right, which is the outer side in the width direction.

[0081] The spark plug 26 is disposed on the side where the exhaust valve 19 is provided, i.e., on the rear side of the extension space 33. The tip of the spark plug 26 is disposed inside the extension space 33. The spark plug 26 has a first spark plug 261 and a second spark plug 262.

[0082] The first spark plug 261 is disposed on the left side of the first exhaust valve 191. The front end of the first spark plug 261 is disposed inside the first extension space 331. Referring to FIG. 2B , the first spark plug 261 penetrates the left side wall of the first engine block 111 and is inserted into the rear portion 3312 of the first extension space from the first plug installation hole 371. That is, the rear portion of the first spark plug 261 is exposed to the outside from the left side wall of the first engine block 111. Here, a plurality of first spark plugs 261 may be disposed in the first extension space 331.

[0083] The second spark plug 262 is disposed to the right of the second exhaust valve 192. The front end of the second spark plug 262 is disposed inside the second extension space 332. Referring to FIG. 2B , the second spark plug 262 penetrates the right side wall of the first engine block 111 and is inserted into the rear portion 3322 of the second extension space through the second plug installation hole 372. That is, the rear portion of the second spark plug 262 is exposed to the outside from the right side wall of the first engine block 111. Here, a plurality of second spark plugs 262 may be disposed in the second extension space 332.

[0084] Referring to Figure 6, the first arm 271 is disposed between the first intake valve 181 and the first intake cam 231. The front surface of the lower part of the first arm 271 abuts against the first intake cam 231. The rear surfaces of the lower part of the first arm 271 abut against the front ends of the two first intake valves 181. The upper end of the first arm 271 is inserted into the arm shaft 29. With this configuration, the first arm 271 is disposed to be rotatable around the arm shaft 29.

[0085] The second arm 272 is disposed between the second intake valve 182 and the second intake cam 232. The front surface of the lower part of the second arm 272 abuts against the second intake cam 232. The rear surfaces of the lower part of the second arm 272 abut against the front ends of the two second intake valves 182. The upper end of the second arm 272 is inserted into the arm shaft 29. With this configuration, the second arm 272 is disposed to be rotatable around the arm shaft 29.

[0086] The intake valve 18 and the exhaust valve 19 close the extension space 33 when no driving force is applied by the advancing / retreating mechanism 20. That is, when the first intake valve 181 is not pressed by the first intake cam 231 and the first arm 271, the first intake valve 181 closes the first extension space 331 by the biasing force of the spring 381. When the first exhaust valve 191 is not pressed by the first exhaust cam 221, the first push rod 241, and the first rocker arm 251, the first exhaust valve 191 closes the first extension space 331 by the biasing force of the spring 383. When the second intake valve 182 is not pressed by the second intake cam 232 and the second arm 272, the second intake valve 182 closes the second extension space 332 by the biasing force of the spring 382. When the second exhaust valve 192 is not being pushed by the second exhaust cam 222 , the second push rod 242 , and the second rocker arm 252 , the second exhaust valve 192 closes the second extension space 332 due to the biasing force of the spring 384 .

[0087] 7A is a perspective view of the second cylinder chamber 122, the second extension space 332, etc., as seen from above and rearward. Here, the second cylinder chamber 122 and the second extension space 332 are indicated by dotted lines. The second extension space 332 is a space that extends upward from the center of the second cylinder chamber 122 in the front-to-rear direction. The second exhaust valve 192 and the second spark plug 262 are disposed on the rear side of the second extension space 332.

[0088] 7B is a perspective view of the second cylinder chamber 122, the second extension space 332, etc., as seen from above the front side. Here, the second cylinder chamber 122 and the second extension space 332 are indicated by dotted lines. Two second intake valves 182 are connected to the front side surface of the second extension space 332.

[0089] The engine section 13, first engine section 14, second engine section 15 and reciprocating mechanism 20 configured as described above operate by repeating an intake stroke, a compression stroke, a combustion stroke and an exhaust stroke as follows.

[0090] During the intake stroke, as shown in FIG. 4 , the first piston 141 and the second piston 151 move from the center toward the outside within the first cylinder chamber 121, causing a mixture of fuel and air to be drawn into the first cylinder chamber 121. At the same time, the first crankshaft 143 and the second crankshaft 153 rotate. As shown in FIG. 5 , during the intake stroke, in the reciprocating mechanism 20, the first intake valve 181 opens the first extension space 331, while the first exhaust valve 191 closes the first extension space 331. Specifically, the crank gear 31 rotates, and the driven gear 30 around which the belt 32 is mounted also rotates. This causes the camshaft 21 connected to the driven gear 30 to rotate together with the first intake cam 231. The rotation of the first intake cam 231 pushes the first arm 271 and the first intake valve 181 rearward. As a result, the front end portion of the first intake valve 181 is pushed into the first extension space 331, and the first intake valve installation hole 351 shown in Fig. 3A opens. Therefore, the air-fuel mixture can be drawn into the first cylinder chamber 121 via the first intake valve installation hole 351 and the first extension space 331 shown in Fig. 3A.

[0091] 4, during the compression stroke, the inertia of the rotating first crankshaft 143 and second crankshaft 153 pushes the first piston 141 and the second piston 151 toward the center, compressing the air-fuel mixture inside the first cylinder chamber 121. Referring to FIG. 5, in the advancing and retracting mechanism 20, the first intake valve 181 closes the first extension space 331, and the first exhaust valve 191 closes the first extension space 331. Specifically, as the camshaft 21 rotates further, the first intake cam 231 no longer presses the first intake valve 181 via the first arm 271. As a result, the first intake valve 181 is displaced forward by the biasing force of the spring 381, and the first intake valve mounting hole 351 shown in FIG. 3A is closed. On the other hand, the first exhaust cam 221 does not push the first exhaust valve 191 via the first push rod 241 and the first rocker arm 251. Therefore, the first exhaust valve 191 is positioned rearward by the biasing force of the spring 383, and closes the first extension space 331. Therefore, the first extension space 331 and the first cylinder chamber 121 are in a closed state, and the air-fuel mixture can be compressed inside the first cylinder chamber 121.

[0092] During the combustion stroke, the first spark plug 261 shown in Fig. 5 ignites in the first extension space 331, causing the air-fuel mixture to combust inside the first extension space 331 and the first cylinder chamber 121 shown in Fig. 4, thereby pushing the first piston 141 and the second piston 151 to their outer ends, which are bottom dead center. Referring to Fig. 5, in the advancing and retracting mechanism 20, the first intake valve 181 closes the first extension space 331, and the first exhaust valve 191 closes the first extension space 331, as in the compression stroke. That is, the states of the first intake valve 181 and the first exhaust valve 191 are the same as those in the compression stroke described above.

[0093] During the exhaust stroke, as shown in Fig. 4, the inertia of the rotating first crankshaft 143 and second crankshaft 153 pushes the first piston 141 and the second piston 151 inward, and the burned gas present inside the first cylinder chamber 121 is exhausted to the outside. As shown in Fig. 5, the reciprocating mechanism 20 causes the first intake valve 181 to close the first extension space 331, while the first exhaust valve 191 to open the first extension space 331. Specifically, when the first intake cam 231 does not press the first intake valve 181 via the first arm 271, the first intake valve 181 closes the first extension space 331 due to the biasing force of the spring 381. Meanwhile, the first exhaust cam 221 pushes the push rod 24 rearward, causing the first rocker arm 251 to rotate and push the first exhaust valve 191 forward. As a result, the first exhaust valve 191 opens the first extension space 331. As a result, the post-combustion gas inside the first cylinder chamber 121 is released to the outside through the first exhaust valve installation hole 361 shown in FIG.

[0094] The same operation is performed for the third engine section 16, the fourth engine section 17, the second intake valve 182, and the second exhaust valve 192.

[0095] 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.

[0096] 5, according to this embodiment, the intake valve 18 is advanced and retracted by the intake cam 23, and the exhaust valve 19 is advanced and retracted by the push rod 24, so that the advancing and retracting mechanism 20 can be disposed near the cylinder chamber 12 even when there are strict geometric constraints near the cylinder chamber 12. Furthermore, the use of the push rod 24 reduces the number of camshafts 21, thereby simplifying the configuration of the engine 10.

[0097] Furthermore, according to this embodiment, the intake valve 18 and the exhaust valve 19 are arranged on either side of the extension space 33, so the intake valve 18 and the exhaust valve 19 are arranged closely together, but because the intake valve 18 or the exhaust valve 19 is moved back and forth via a push rod, the configuration around the extension space 33 can be simplified.

[0098] Furthermore, according to this embodiment, even when multiple cylinder chambers 12 are adjacent to each other and a large number of intake valves 18 and exhaust valves 19 are arranged, the overall configuration of the engine 10 can be simplified by optimizing the configuration of the camshaft 21 and the push rod.

[0099] FIG. 8 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.

[0100] 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.

[0101] 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 .

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] The same applies to the second cylinder chamber 122 described above.

[0107] 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.

[0108] For example, referring to FIG. 5, the exhaust valve 19 is advanced and retracted by the push rod 24, but it is also possible to configure the intake valve 18 to be advanced and retracted by the push rod 24, and the exhaust valve 19 to be advanced and retracted without using the push rod 24.

[0109] Furthermore, although the engine 10 described above has a plurality of cylinder chambers 12, the number of cylinder chambers 12 may be one.

[0110] 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 1211 First cylinder chamber front portion 1212 First cylinder chamber rear portion 122 Second cylinder chamber 1221 Second cylinder chamber front portion 1222 Second cylinder chamber rear portion 1213 First central axis 1214 First side surface 1291 First extending 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 Intake valve 181 First intake valve 182 Second intake valve 19 Exhaust valve 191 First exhaust valve 192 Second exhaust valve 20 Advance / retreat mechanism 21 Camshaft 22 Exhaust cam 221 First exhaust cam 222 Second exhaust cam 1281 First cylinder wall portion 2282 Second cylinder wall portion 2292 Second extension wall portion 23 Intake cam 231 First intake cam 232 Second intake cam 24 Push rod 241 First push rod 242 Second push rod 25 Rocker arm 251 First rocker arm 252 Second rocker arm 26 Spark plug 261 First spark plug 262 Second spark plug 271 First arm 272 Second arm 29 Arm shaft 30 Driven gear 31 Crank gear 32 Belt 33 Extension space 331 First extension space 3311 Front portion of first extension space 3312 Rear portion of first extension space 332 Second extension space 3321 Front portion of second extension space 3322 Rear portion of second extension space 34 Combustion chamber341 First combustion chamber 342 Second combustion chamber 35 Intake valve mounting hole 351 First intake valve mounting hole 352 Second intake valve mounting hole 36 Exhaust valve mounting hole 361 First exhaust valve mounting hole 362 Second exhaust valve mounting hole 37 Plug mounting hole 371 First plug mounting hole 372 Second plug mounting hole 381 Spring 382 Spring 383 Spring 384 Spring 40 First contact surface 41 Second contact surface

Claims

1. An engine comprising: a cylinder chamber, an intake valve, an exhaust valve, and an advance / retract mechanism for advancing and retracting the intake valve and the exhaust valve, the advance / retract mechanism having a camshaft, a first cam, a second cam, a push rod, and a rocker arm, the first cam is fixed to the camshaft and configured to advance and retract either the intake valve or the exhaust valve, the second cam is separate from the first cam and configured to advance and retract the push rod, and the rocker arm is rotated by the push rod and configured to advance and retract the other of the intake valve and the exhaust valve.

2. The engine according to claim 1, wherein the first cam advances and retreats a plurality of the intake valves, and the second cam advances and retreats the exhaust valve via the push rod.

3. An engine as described in claim 2, characterized in that within the cylinder chamber, pistons arranged opposite each other along the fore-and-aft direction are arranged so as to reciprocate when the axial direction of the cylinder chamber is taken as the fore-and-aft direction, an extension space is provided extending laterally from a middle part of the cylinder chamber in the fore-and-aft direction, the intake valve is provided so as to be able to advance and retreat into the extension space from the front side, and the exhaust valve is provided so as to be able to advance and retreat into the extension space from the rear side.

4. The cylinder chamber has a first cylinder chamber and a second cylinder chamber adjacent to the first cylinder chamber, a first piston and a second piston are housed inside the first cylinder chamber so as to reciprocate, and a third piston and a fourth piston are housed inside the second cylinder chamber so as to reciprocate, the cylinder chamber has a first extension space extending laterally from a middle part of the first cylinder chamber in the front-to-rear direction, and a second extension space extending laterally from a middle part of the second cylinder chamber in the front-to-rear direction, the intake valve has a first intake valve and a second intake valve, the exhaust valve has a first exhaust valve and a second exhaust valve, the first intake valve is provided so as to be able to advance and retreat into the first extension space from a front side, the first exhaust valve is provided so as to be able to advance and retreat into the first extension space from a rear side, and the second intake valve is provided so as to be able to advance and retreat into the second extension space from a front side, The engine according to claim 3 , wherein the second exhaust valve is provided so as to be movable forward and backward from a rear side of the second extension space.

5. An engine as described in claim 3, characterized in that the number of said intake valves is greater than the number of said exhaust valves, and a spark plug is disposed so as to be exposed on the side of said extension space where said exhaust valves are provided.

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