Opposed-piston type engine

Abstract

Provided is an opposed-piston type engine capable of downsizing a mechanism for transmitting rotational power of a crankshaft to a valve.　An opposed-piston type engine (1) is provided with: a cylinder (4); a first piston (8A) which is disposed in the cylinder; a second piston (8B) which is disposed in the cylinder so as to be opposing the first piston; a first crankshaft (9A) which rotates in association with reciprocation of the first piston; a second crankshaft (9B) which rotates in association with reciprocation of the second piston; a valve (13) which operates with respect to the cylinder so as to perform intake or exhaust; and a power transmission mechanism (20) which transmits the rotational power of the first crankshaft to the valve so as to cause the valve to operate. The first crankshaft and the second crankshaft are disposed apart from each other in the arrangement direction of the first piston and the second piston, and the power transmission mechanism is disposed across the first crankshaft and the second crankshaft in the arrangement direction.

Description

opposed-piston engine

[0001] The present invention relates to an opposed-piston engine in which two pistons are arranged opposite each other.

[0002] A conventional opposed-piston engine is disclosed in Patent Document 1. The opposed-piston engine disclosed in Patent Document 1 includes two pistons arranged opposite each other, two crankshafts that rotate in conjunction with the reciprocating motion of each piston, and a valve drive mechanism that controls the operation of intake valves and exhaust valves.

[0003] Japanese Patent Publication No. 2019-90424

[0004] The valve drive mechanism for an opposed-piston engine disclosed in Patent Document 1 includes a crank pulley, a cam pulley, and a timing belt stretched between the crank pulley and the cam pulley. In this valve drive mechanism, a timing belt is stretched around each of the crank pulleys of the two crankshafts. This makes it difficult to miniaturize the mechanism that transmits the rotational power of the crankshafts to the valves.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide an opposed-piston engine in which the mechanism for transmitting the rotational power of the crankshaft to the valves can be made smaller.

[0006] The technical means adopted by the present invention to solve the above problems are characterized as follows.

[0007] An opposed-piston engine according to one aspect of the present invention comprises a cylinder, a first piston disposed in the cylinder, a second piston disposed in the cylinder opposite the first piston, a first crankshaft that rotates with the reciprocating motion of the first piston, a second crankshaft that rotates with the reciprocating motion of the second piston, a valve that operates relative to the cylinder to perform intake or exhaust, and a power transmission mechanism that transmits the rotational power of the first crankshaft to the valve to operate the valve, wherein the first crankshaft and the second crankshaft are disposed at an interval in the alignment direction of the first piston and the second piston, and the power transmission mechanism is provided across the first crankshaft and the second crankshaft in the alignment direction.

[0008] The power transmission mechanism may include a camshaft that rotates in conjunction with rotation of the first crankshaft, a push rod that reciprocates in conjunction with rotation of the camshaft, and a rocker arm that links the push rod and the valve, wherein one end of the push rod is disposed on the first crankshaft side and the other end of the push rod is disposed on the second crankshaft side, and the rocker arm links the other end of the push rod and the valve on the second crankshaft side.

[0009] The camshaft may be configured to include a single camshaft that is disposed on the first crankshaft side in the arrangement direction.

[0010] The valves may include an intake valve and an exhaust valve, and the intake valve and the exhaust valve may be configured to operate in accordance with the rotation of the one camshaft.

[0011] The camshaft may have a shaft and a cam provided on the shaft, and one end of the push rod may be disposed in contact with the cam.

[0012] The base end of one of the intake valve and the exhaust valve may be in contact with the rocker arm, and the base end of the other valve may be in contact with a swinging member that moves in conjunction with the cam.

[0013] The one valve may be the exhaust valve, and the other valve may be the intake valve.

[0014] The first piston and the second piston may be arranged side by side in a horizontal direction, and the camshaft may be arranged above the first crankshaft.

[0015] The push rod may include a first push rod and a second push rod, the cam may include a first cam and a second cam spaced apart in the extension direction of the camshaft, and one end of the first push rod may be arranged in contact with the first cam, and one end of the second push rod may be arranged in contact with the second cam.

[0016] In the opposed-piston engine according to the present invention, the power transmission mechanism that transmits the rotational power of the crankshaft to the valves to operate the valves is provided across the first crankshaft and the second crankshaft in the alignment direction of the first piston and the second piston, so that the power transmission mechanism for transmitting the rotational power of the crankshaft to the valves can be made smaller.

[0017] 1 is a perspective view of an engine according to one embodiment of the present invention, as seen from the front left; FIG. 2 is a perspective view of an engine according to one embodiment of the present invention, as seen from the rear right; FIG. 3 is a side view of an engine according to one embodiment of the present invention, as seen from the right; FIG. 4 is a front view of an engine according to one embodiment of the present invention, as seen from the front left; FIG. 5 is a longitudinal section view of an engine according to one embodiment of the present invention, cut vertically at the position of an intake passage; FIG. 6 is a longitudinal section view of an engine according to one embodiment of the present invention, cut vertically at the position of an exhaust passage; FIG. 7 is a transverse section view of an engine according to one embodiment of the present invention, cut horizontally; FIG. 8 is a perspective view showing the internal structure of an engine according to one embodiment of the present invention; FIG. 9 is a plan view showing the internal structure of an engine according to one embodiment of the present invention; FIG. 10 is a front view showing the internal structure of an engine according to one embodiment of the present invention; FIG. 11 is a right side view showing the internal structure of an engine according to one embodiment of the present invention; FIG. 12 is a left side view showing the internal structure of an engine according to one embodiment of the present invention; FIG. 13 is a perspective view showing a power transmission mechanism that operates an intake valve and an exhaust valve; FIG. 14 is a perspective view showing a power transmission mechanism that operates an exhaust valve; FIG. 15 is a right side view showing a power transmission mechanism that operates an intake valve; FIG. 16 is a perspective view showing a decompression device; FIG. 17 is a view from below and front of an engine according to one embodiment of the present invention; FIG. 18 is a perspective section view of an engine according to one embodiment of the present invention, cut horizontally at the position of an oil pan and an inclined portion; FIG. 19 is a plan view of a flying device according to one embodiment of the present invention. Fig. 1 is a perspective view showing a flying device according to one embodiment of the present invention. Fig. 2 is a front view showing a flying device according to one embodiment of the present invention. Fig. 3 is a rear view showing a flying device according to one embodiment of the present invention. Fig. 4 is a rear view showing an enlarged view of a portion of a flying device according to one embodiment of the present invention. Fig. 5 is a plan view showing an enlarged view of a portion of a flying device according to one embodiment of the present invention where an engine is mounted. Fig. 6 is a right side view showing an enlarged view of a portion of a flying device according to a first embodiment of the present invention.

[0018] A preferred embodiment of an engine 1 according to the present invention and a flight device 101 equipped with this engine 1 will be described below with reference to the drawings. For ease of explanation, the direction indicated by arrow F in the drawings will be referred to as forward, the direction indicated by arrow B as backward, the direction indicated by arrow L as left, and the direction indicated by arrow R as right. Additionally, the direction indicated by arrow U will be referred to as upward, and the direction indicated by arrow D as downward.

[0019] The engine 1 of the embodiment described below is an opposed-piston engine 1 in which two pistons are arranged facing each other inside a cylinder. As shown in Figures 1 to 4, the opposed-piston engine 1 includes an engine block 2 and an output shaft 3 protruding from the engine block 2. As shown in Figures 5 and 6, a cylinder 4, as well as an intake passage 5 and an exhaust passage 6 communicating with the cylinder 4, are formed inside the engine block 2.

[0020] As shown in FIGS. 1 to 3 , the engine block 2 is formed by combining multiple blocks. In this embodiment, the engine block 2 is formed by a first block 2A, a second block 2B, and a third block 2C. The first block 2A is located at the rear of the engine block 2. The third block 2C is located at the front of the engine block 2. The second block 2B is disposed between the first block 2A and the second block 2B. The first block 2A and the second block 2B are connected by a bolt BL1. The second block 2B and the third block 2C are connected by a bolt BL2. Therefore, the engine block 2 can be separated into multiple blocks (the first block 2A, the second block 2B, and the third block 2C) by removing the bolts BL1 and BL2.

[0021] As shown in Figures 5 and 6, the cylinders 4 are arranged inside the engine block 2 with their axes oriented horizontally (front-to-rear). The cylinders 4 include a first cylinder 4A and a second cylinder 4B. The first cylinder 4A is formed inside the first block 2A. The second cylinder 4B is formed inside the second block 2B. The first cylinder 4A and the second cylinder 4B are arranged side by side in the horizontal direction (front-to-rear direction). The front end of the first cylinder 4A and the rear end of the second cylinder 4B are arranged butted against each other (in contact). The central axes of the first cylinder 4A and the second cylinder 4B are on the same straight line. The interiors of the first cylinder 4A and the second cylinder 4B are connected to each other.

[0022] 5 and 6, an opening 7 is formed above the boundary between the first cylinder 4A and the second cylinder 4B. The intake passage 5 and the exhaust passage 6 communicate with the interior of the cylinder 4 through the opening 7. The intake passage 5 is opened and closed by an intake valve 14. The exhaust passage 6 is opened and closed by an exhaust valve 15.

[0023] A piston 8 and a crankshaft 9 are housed inside the engine block 2. The piston 8 is disposed inside the cylinder 4. The piston 8 includes a first piston 8A and a second piston 8B. The first piston 8A is disposed inside the first cylinder 4A. The second piston 8B is disposed inside the second cylinder 4B. The first piston 8A and the second piston 8B are disposed side by side in the horizontal direction (front-to-rear direction). The first piston 8A and the second piston 8B are disposed opposite each other.

[0024] The first piston 8A reciprocates horizontally (front-to-back) within the first cylinder 4A. The second piston 8B reciprocates horizontally (front-to-back) within the second cylinder 4B. The first piston 8A and the second piston 8B move in directions away from or toward each other. Hereinafter, the first piston 8A and the second piston 8B will be collectively referred to as a "piston pair."

[0025] 5 and 6 , the upper portion (upper front portion) of the first piston 8A facing the second piston 8B curves away from the second piston 8B. The upper portion (upper rear portion) of the second piston 8B facing the first piston 8A curves away from the first piston 8A. As a result, when the first piston 8A and the second piston 8B are close to each other, a space S1 is formed between the upper front portion of the first piston 8A and the upper rear portion of the second piston 8B. The space S1 communicates with the intake passage 5 and the exhaust passage 6 via the opening 7.

[0026] As shown in Figure 7, the opposed-piston engine 1 has two piston pairs, each consisting of a first piston 8A and a second piston 8B. Hereinafter, the two piston pairs will be referred to as a first piston pair 81 and a second piston pair 82, respectively. The first piston pair 81 and the second piston pair 82 are arranged side by side in the horizontal direction. Specifically, the first piston pair 81 and the second piston pair 82 are arranged side by side in the left-right direction. More specifically, the first piston pair 81 is arranged on the left side, and the second piston pair 82 is arranged on the right side.

[0027] Hereinafter, for convenience of explanation, the first piston 8A constituting the first piston pair 81 will be referred to as the "first piston 81A," and the second piston 8B constituting the first piston pair 81 will be referred to as the "second piston 81B." Furthermore, the first piston 8A constituting the second piston pair 82 will be referred to as the "first piston 82A," and the second piston 8B constituting the second piston pair 82 will be referred to as the "second piston 82B."

[0028] In other words, the opposed-piston engine 1 of this embodiment has two piston pairs, and therefore four pistons (first piston 81A, second piston 81B, first piston 82A, second piston 82B). However, the number of piston pairs is not limited to two, and may be one, or three or more. Therefore, the number of pistons 8 is not limited to four, and may be two, or six or more.

[0029] As shown in FIG. 7 , the first cylinder 4A includes a first cylinder 4A1 that houses a first piston 81A and a first cylinder 4A2 that houses a first piston 82A. The second cylinder 4B includes a second cylinder 4B1 that houses a second piston 81B and a second cylinder 4B2 that houses a second piston 82B. In this manner, the opposed-piston engine 1 includes four cylinders (first cylinder 4A1, second cylinder 4B1, first cylinder 4A2, and second cylinder 4B2) that each house four pistons. In other words, the opposed-piston engine 1 of this embodiment is a four-cylinder engine. However, the number of cylinders 4 is set according to the number of pistons 8 and is not limited to four.

[0030] As shown in FIG. 7 , the front end of the first cylinder 4A1 and the rear end of the second cylinder 4B1 are arranged in abutting relation to each other. The interiors of the first cylinder 4A1 and the second cylinder 4B1 are connected to each other. Hereinafter, the first cylinder 4A1 and the second cylinder 4B1 will be collectively referred to as the "first cylinder structure 41." The front end of the first cylinder 4A2 and the rear end of the second cylinder 4B2 are arranged in abutting relation to each other. The interiors of the first cylinder 4A2 and the second cylinder 4B2 are connected to each other. Hereinafter, the first cylinder 4A2 and the second cylinder 4B2 will be collectively referred to as the "second cylinder structure 42." The first cylinder structure 41 and the second cylinder structure 42 are arranged side by side in the left-right direction.

[0031] As described above, the intake passage 5 (see FIG. 5) and the exhaust passage 6 (see FIG. 6) communicate with the interior of the cylinder 4. Although not shown in FIG. 7, the intake passage 5 and the exhaust passage 6 are provided in the first cylinder structure 41 and the second cylinder structure 42, respectively.

[0032] The intake passage 5 includes a first intake passage that communicates with the interior of the first cylinder structure 41 and a second intake passage that communicates with the interior of the second cylinder structure 42. Two first intake passages and two second intake passages are provided. That is, two first intake passages are provided in the first cylinder structure 41. Two second intake passages are also provided in the second cylinder structure 42. An intake valve 14 is disposed in each of the two first intake passages and the two second intake passages.

[0033] The exhaust passage 6 includes a first exhaust passage that communicates with the interior of the first cylinder structure 41 and a second exhaust passage that communicates with the interior of the second cylinder structure 42. One first exhaust passage and one second exhaust passage are provided. An exhaust valve 15 is disposed in each of the first exhaust passage and the second exhaust passage.

[0034] In this way, one cylinder structure is provided with two intake valves 14 and one exhaust valve 15 in the opposed-piston engine 1. The opposed-piston engine 1 has two cylinder structures (a first cylinder structure 41 and a second cylinder structure 42), and therefore has four intake valves 14 (see reference numerals 14A, 14B, 14C, and 14D in FIG. 9 ) and two exhaust valves 15 (see reference numerals 15A and 15B in FIG. 9 ).

[0035] As shown in Figures 5 and 6, the crankshaft 9 is connected to the piston 8 by a connecting rod 10. As shown in Figures 8, 9, and 7, the crankshaft 9 has a crank pin 91, a crank journal 92, a crank arm 93, a main shaft 94, and a counterweight 95. The crank pin 91 is connected to the connecting rod 10. The crank pin 91 and the crank journal 92 are connected by the crank arm 93. The main shaft 94 is connected to the output shaft 3.

[0036] As shown in Figures 8 and 9, the crankshaft 9 includes a first crankshaft 9A and a second crankshaft 9B. The first crankshaft 9A and the second crankshaft 9B are arranged at an interval in the direction in which the first piston 8A and the second piston 8B are arranged. The first crankshaft 9A and the second crankshaft 9B extend parallel to each other. The first crankshaft 9A and the second crankshaft 9B extend in a direction perpendicular to the direction in which the first piston 8A and the second piston 8B are arranged.

[0037] In this embodiment, the first piston 8A and the second piston 8B are aligned in the front-to-rear direction. Therefore, the first crankshaft 9A and the second crankshaft 9B are spaced apart in the front-to-rear direction. The first crankshaft 9A and the second crankshaft 9B also extend in the left-to-right direction. However, the front-to-rear and left-to-right directions change depending on the orientation of the opposed-piston engine 1 when it is installed.

[0038] As shown in Figure 7, the first crankshaft 9A is connected to the first piston 8A by a first connecting rod 10A. The second crankshaft 9B is connected to the second piston 8B by a second connecting rod 10B. The first crankshaft 9A rotates in conjunction with the reciprocating motion of the first piston 8A. The second crankshaft 9B rotates in conjunction with the reciprocating motion of the second piston 8B.

[0039] The rotational power of the crankshaft 9 is extracted from the output shaft 3 connected to the main shaft 94. The output shaft 3 includes a first output shaft 3A and a second output shaft 3B. The first output shaft 3A and the second output shaft 3B are arranged parallel to each other. The first output shaft 3A and the second output shaft 3B extend in opposite directions.

[0040] As shown in Fig. 7, the first output shaft 3A is connected to the main shaft 94 of the first crankshaft 9A via a first coupling 11A. The second output shaft 3B is connected to the main shaft 94 of the second crankshaft 9B via a second coupling 11B. As a result, the rotational power of the first crankshaft 9A is extracted from the first output shaft 3A. The rotational power of the second crankshaft 9B is extracted from the second output shaft 3B.

[0041] As shown in Figures 1, 2, and 7, the opposed-piston engine 1 is equipped with a generator 12. The generator 12 includes a first generator 12A and a second generator 12B. The first generator 12A is attached to the first crankshaft 9A. The second generator 12B is attached to the second crankshaft 9B. Specifically, the first generator 12A is attached to the end of the first crankshaft 9A, opposite the first output shaft 3A. The second generator 12B is attached to the end of the second crankshaft 9B, opposite the second output shaft 3B. The first generator 12A is driven by the rotation of the first crankshaft 9A to generate electric power. The second generator 12B is driven by the rotation of the second crankshaft 9B to generate electric power.

[0042] As shown in Figures 5 and 6, the opposed-piston engine 1 is equipped with valves 13 for intake or exhaust. The valves 13 operate relative to the cylinders 4 to intake or exhaust air. The valves 13 include the intake valves 14 and exhaust valves 15 described above. The intake valves 14 are disposed in the intake passages 5 that communicate with the interiors of the cylinders 4. The exhaust valves 15 are disposed in the exhaust passages 6 that communicate with the interiors of the cylinders 4. The intake valves 14 are disposed on the first crankshaft 9A side. The exhaust valves 15 are disposed on the second crankshaft 9B side. However, the intake valves 14 may be disposed on the second crankshaft 9B side, and the exhaust valves 15 may be disposed on the first crankshaft 9A side.

[0043] 8 and 9, the opposed-piston engine 1 is equipped with a power transmission mechanism 20 that transmits the rotational power of the first crankshaft 9A to the valves 13 to operate the valves 13. Figure 13 is a diagram showing the configuration of the power transmission mechanism 20. The power transmission mechanism 20 transmits the rotational power of the first crankshaft 9A to the exhaust valves 15 and the intake valves 14 to operate the exhaust valves 15 and the intake valves 14.

[0044] As shown in Figures 13, 8, and 9, the power transmission mechanism 20 includes a camshaft 21, a push rod 22, and a rocker arm 23. The camshaft 21 is composed of a single camshaft located on the first crankshaft 9A side (rear side) in the arrangement direction (front-rear direction) of the first piston 8A and the second piston 8B. In other words, the camshaft 21 is located on the first crankshaft 9A side, but not on the second crankshaft 9B side. The camshaft 21 extends parallel to the first crankshaft 9A. The camshaft 21 is located above the first crankshaft 9A.

[0045] However, the camshaft 21 may be disposed at a position other than above the first crankshaft 9A (for example, at a position shifted forward or rearward from above the first crankshaft 9A). Also, the camshaft 21 may be disposed on the second crankshaft 9B side instead of the first crankshaft 9A side. In this case, the camshaft 21 is disposed above the second crankshaft 9B, etc.

[0046] As shown in Figures 8 and 9, a first gear 25 is attached to the first crankshaft 9A. A second gear 26 is attached to the camshaft 21. The first gear 25 and the second gear 26 are in mesh with each other. When the first gear 25 rotates in conjunction with the rotation of the first crankshaft 9A, the camshaft 21 rotates together with the second gear 26 that is in mesh with the first gear 25. In this way, the camshaft 21 rotates in conjunction with the rotation of the first crankshaft 9A. The rotation direction of the camshaft 21 is opposite to the rotation direction of the first crankshaft 9A.

[0047] As shown in FIGS. 1, 8, and 9, a third gear 27 is attached to the camshaft 21. A fourth gear 28 is attached to the second crankshaft 9B. An endless (loop-shaped) belt 29 is wound around the third gear 27 and the fourth gear 28. As a result, the rotation of the camshaft 21 is transmitted to the second crankshaft 9B. The rotation direction of the camshaft 21 and the rotation direction of the second crankshaft 9B are the same. Because the rotation direction of the camshaft 21 is opposite to the rotation direction of the first crankshaft 9A, the rotation directions of the first crankshaft 9A and the second crankshaft 9B are opposite to each other. Therefore, the first output shaft 3A and the second output shaft 3B rotate in opposite directions.

[0048] As shown in Figure 13, the camshaft 21 has a shaft 30 and cams 31 provided on the shaft 30. A plurality of cams 31 are provided at intervals along the length of the shaft 30 (left-right direction). The plurality of cams 31 include a first cam 31A, a second cam 31B, a third cam 31C, and a fourth cam 31D (see also Figure 8). The four cams (first cam 31A, second cam 31B, third cam 31C, and fourth cam 31D) are provided at intervals along the extension direction of the camshaft 21.

[0049] The first cam 31A and the second cam 31B are provided near both ends of the camshaft 21, spaced apart from each other. The first cam 31A is provided near one end (left portion) of the shaft 30. The second cam 31B is provided near the other end (right portion) of the shaft 30. The third cam 31C and the fourth cam 31D are provided between the first cam 31A and the second cam 31B. The third cam 31C is provided next to the first cam 31A. The fourth cam 31D is provided next to the second cam 31B.

[0050] The first cam 31A and the second cam 31B are arranged with a phase difference of 180 degrees around the axis of the shaft 30. The third cam 31C and the fourth cam 31D are arranged with a phase difference of 180 degrees around the axis of the shaft 30. The third cam 31C and the first cam 31A are arranged with a phase difference of 90 degrees around the axis of the shaft 30. The fourth cam 31D and the second cam 31B are arranged with a phase difference of 90 degrees around the axis of the shaft 30.

[0051] As shown in Figures 8, 9, 11, and 12, the push rod 22 extends from the first crankshaft 9A side to the second crankshaft 9B side. One end 22a (see Figure 11) of the push rod 22 is disposed on the first crankshaft 9A side (rear side). The other end 22b (see Figure 11) of the push rod 22 is disposed on the second crankshaft 9B side (front side). The one end 22a of the push rod 22 is disposed in contact with the cam 31 (first cam 31A or second cam 31B) of the camshaft 21. The other end 22b of the push rod 22 is connected to the rocker arm 23.

[0052] As shown in Figures 8 to 10, the push rod 22 includes a first push rod 22A and a second push rod 22B. The first push rod 22A and the second push rod 22B are arranged at an interval in the extension direction (left-right direction) of the camshaft 21. The first push rod 22A and the second push rod 22B are arranged parallel to each other. The first push rod 22A extends in the front-rear direction at one end (left side) of the camshaft 21. The second push rod 22B extends in the front-rear direction at the other end (right side) of the camshaft 21.

[0053] One end of the first push rod 22A is disposed in contact with the first cam 31A. One end of the second push rod 22B is disposed in contact with the second cam 31B. The first cam 31A and the second cam 31B rotate together with the camshaft 21. When the first cam 31A rotates together with the camshaft 21, the first push rod 22A reciprocates. When the second cam 31B rotates together with the camshaft 21, the second push rod 22B reciprocates. In this way, the push rods 22 (the first push rod 22A and the second push rod 22B) reciprocate in accordance with the rotation of the single camshaft 21.

[0054] The rocker arm 23 connects the push rod 22 and the valve 13. More specifically, the rocker arm 23 connects the other end 22b (see FIG. 11 ) of the push rod 22 and the valve 13 on the second crankshaft 9B side. The rocker arm 23 connects the other end 22b of the push rod 22 and one of the intake valve 14 and the exhaust valve 15. In this embodiment, the rocker arm 23 connects the other end 22b of the push rod 22 and the exhaust valve 15.

[0055] In another embodiment, the intake valve 14 may be disposed on the second crankshaft 9B side, and the other end 22b of the push rod 22 may be connected to the intake valve 14. In this case, the exhaust valve 15 is disposed on the first crankshaft 9A side.

[0056] As shown in Figures 8, 9, and 13, the rocker arm 23 includes a first rocker arm 23A and a second rocker arm 23B. The first rocker arm 23A is linked to the first push rod 22A. The second rocker arm 23B is linked to the second push rod 22B. Specifically, the first rocker arm 23A links the other end of the first push rod 22A with the exhaust valve 15 (first exhaust valve 15A, described below). The second rocker arm 23B links the other end of the second push rod 22B with the exhaust valve 15 (second exhaust valve 15B, described below).

[0057] As shown in Figures 13 and 14, the rocker arm 23 has a cylindrical portion 23a and an arc-shaped portion 23b. A shaft 23c is inserted into the cylindrical portion 23a. A fixing plate 23d is attached to the end of the shaft 23c. As shown in Figure 2, the fixing plate 23d is fixed to the engine block 2. As a result, the shaft 23c is positioned and supported relative to the engine block 2.

[0058] As shown in Figure 14, the arc-shaped portion 23b has a first portion 23b1 and a second portion 23b2. The first portion 23b1 and the second portion 23b2 are located on opposite sides of the cylindrical portion 23a. The arc-shaped portion 23b swings around the shaft body 23c as the push rod 22 reciprocates. When the arc-shaped portion 23b swings, the first portion 23b1 and the second portion 23b2 rotate in opposite directions around the cylindrical portion 23a.

[0059] A first portion 23b1 of the arc-shaped portion 23b is connected to the other end 22b of the push rod 22. A second portion 23b2 abuts against a base end portion of one of the intake valve 14 and the exhaust valve 15. In the present embodiment, the one valve is the exhaust valve 15, and the other valve is the intake valve 14. Therefore, in the present embodiment, the second portion 23b2 of the arc-shaped portion 23b of the rocker arm 23 abuts against a base end portion 151c of the exhaust valve 15.

[0060] In this way, the base end 151c of the exhaust valve 15, which is one of the intake valve 14 and exhaust valve 15, abuts against the rocker arm 23. In contrast, as shown in Figures 13 and 15, the base end of the intake valve 14, which is the other valve, abuts against a swinging member 47 (described later) that moves in conjunction with the cam 31. The cams 31 that move in conjunction with the swinging member 47 are the third cam 31C and the fourth cam 31D.

[0061] As shown in Figures 13, 15, etc., the linkage mechanism 45 has a support shaft 46 and a swinging member 47. As shown in Figure 9, the support shaft 46 extends parallel to the camshaft 21 and the crankshaft 9. The support shaft 46 is supported by the engine block 2. The support shaft 46 is disposed on the first crankshaft 9A side (rear side) in the arrangement direction (front-rear direction) of the first piston 8A and the second piston 8B. As shown in Figure 11, the support shaft 46 is disposed above the first crankshaft 9A and near the camshaft 21.

[0062] As shown in Figure 15, the swinging member 47 is attached to the support shaft 46. The swinging member 47 is swingable around the axis of the support shaft 46. As shown in Figures 15 and 16, the swinging member 47 has a cylindrical portion 47a and an arc-shaped portion 47b. The support shaft 46 is inserted into the cylindrical portion 47a. The arc-shaped portion 47b extends downward in an arc shape from the cylindrical portion 47a. The arc-shaped portion 47b has a first abutment portion 47b1 that abuts against the cam 31 and a second abutment portion 47b2 that abuts against the stem 141b (described later) of the intake valve 14.

[0063] As shown in FIG. 15 , the swinging member 47 includes a first swinging member 47A and a second swinging member 47B. The first swinging member 47A and the second swinging member 47B have the same shape. The first swinging member 47A has two cylindrical portions 47a and two arc-shaped portions 47b. Therefore, the first swinging member 47A has two first contact portions 47b1 and two second contact portions 47b2. The second swinging member 47B also has two cylindrical portions 47a and two arc-shaped portions 47b. Therefore, the second swinging member 47B also has two first contact portions 47b1 and two second contact portions 47b2.

[0064] 11, 15, and 16, the intake valve 14 includes a valve body 141 having an umbrella portion 141a and a stem 141b, and a spring 142 that biases the valve body 141. The umbrella portion 141a is provided at the tip of the stem 141b (the tip of the intake valve 14). The second abutment portion 47b2 of the swinging member 47 can abut against the base end of the stem 141b. The spring 142 biases the valve body 141 in the direction that closes the intake valve 14 (the direction that closes the intake passage 5).

[0065] 11 and 14, the exhaust valve 15 has a valve body 151 having an umbrella portion 151a and a stem 151b, and a spring 152 that biases the valve body 151. The umbrella portion 151a is provided at the tip of the stem 151b (the tip of the exhaust valve 15). The spring 152 biases the valve body 151 in the direction that closes the exhaust valve 15 (the direction that closes the exhaust passage 6).

[0066] The intake valve 14 and the exhaust valve 15 operate in accordance with the rotation of one camshaft 21. The operation of the intake valve 14 and the exhaust valve 15 in accordance with the rotation of one camshaft 21 will now be described.

[0067] 16 , the base end of the intake valve 14 (base end 141d of the stem 141b) is positioned so as to come into contact with the second contact portion 47b2 of the swinging member 47 when the swinging member 47 swings. Furthermore, the cam 31 (third cam 31C or fourth cam 31D) of the camshaft 21 can come into contact with the first contact portion 47b1 of the swinging member 47 by rotating. Therefore, the base end of the intake valve 14 (base end of the stem 141b) can come into contact with the cam 31 (third cam 31C or fourth cam 31D) via the swinging member 47.

[0068] When the cam 31 rotates together with the camshaft 21, the first abutment portion 47b1 abuts against the cam 31, and the first abutment portion 47b1 is pushed by the cam 31 toward the intake valve 14. This causes the swinging member 47 to swing toward the intake valve 14, with the support shaft 46 as a fulcrum, and the base end portion 141d of the stem 141b is pushed by the second abutment portion 47b2 of the swinging member 47. When the stem 141b is pushed, the spring 142 contracts, and the valve body 141 moves. This moves the umbrella portion 141a (see FIG. 5), which had been closing the intake passage 5, and the intake valve 14 opens (the intake passage 5 is opened).

[0069] As shown in FIG. 14 , the base end of the exhaust valve 15 (the base end 151c of the stem 151b) abuts against the rocker arm 23. One end 22a of the push rod 22 is disposed in contact with the cam 31 (the first cam 31A or the second cam 31B). Therefore, when the cam 31 rotates together with the camshaft 21, the one end 22a of the push rod 22, which abuts against the cam 31, is pushed by the cam 31. This causes the push rod 22 to move toward the second crankshaft 9B (the right side in FIG. 14 ). Then, the arc-shaped portion 23b of the rocker arm 23 swings about the shaft 23c as a fulcrum, and the base end 151c of the stem 151b, which abuts against the second portion 23b2, is pushed by the second portion 23b2. When the stem 151b is pushed, the spring 152 contracts, causing the valve body 151 to move. As a result, the umbrella portion 151a that had been closing the exhaust passage 6 moves, and the exhaust valve 15 opens (the exhaust passage 6 is opened).

[0070] As shown in Figures 9, 13, etc., the exhaust valve 15 includes a first exhaust valve 15A and a second exhaust valve 15B. The first exhaust valve 15A and the second exhaust valve 15B are arranged at an interval in the extension direction of the camshaft 21. The exhaust valves 15 (first exhaust valve 15A, second exhaust valve 15B) are arranged between the first push rod 22A and the second push rod 22B in the extension direction of the camshaft 21. The first exhaust valve 15A is arranged on the first push rod 22A side. The second exhaust valve 15B is arranged on the second push rod 22B side.

[0071] 9, 13, etc., the intake valve 14 includes a first intake valve 14A, a second intake valve 14B, a third intake valve 14C, and a fourth intake valve 14D. The first intake valve 14A, the second intake valve 14B, the third intake valve 14C, and the fourth intake valve 14D are arranged at intervals from one another in the extension direction of the camshaft 21.

[0072] As shown in Figures 9, 13, etc., the intake valves 14 (first intake valve 14A, second intake valve 14B, third intake valve 14C, and fourth intake valve 14D) are arranged between the first push rod 22A and the second push rod 22B in the extension direction of the camshaft 21. The first intake valve 14A and the second intake valve 14B are arranged on the first push rod 22A side. The third intake valve 14C and the fourth intake valve 14D are arranged on the second push rod 22B side.

[0073] 9 and other figures, the first intake valve 14A, second intake valve 14B, third intake valve 14C, and fourth intake valve 14D are arranged in this order from the first push rod 22A side toward the second push rod 22B side. The first intake valve 14A and second intake valve 14B face the first exhaust valve 15A. The third intake valve 14C and fourth intake valve 14D face the second exhaust valve 15B.

[0074] As described above, the intake valves 14 abut against the swing member 47 (see FIG. 15, etc.). More specifically, of the four intake valves 14, two abut against the first swing member 47A, and the remaining two abut against the second abutment portion 47b2. Specifically, as shown in FIG. 13, the first intake valve 14A and the second intake valve 14B abut against the second abutment portion 47b2 of the first swing member 47A. The third intake valve 14C and the fourth intake valve 14D abut against the second abutment portion 47b2 of the second swing member 47B.

[0075] The first intake valve 14A abuts against one of the two second abutment portions 47b2 of the first swing member 47A. The second intake valve 14B abuts against the other of the two second abutment portions 47b2 of the first swing member 47A. This allows the first intake valve 14A and the second intake valve 14B to operate simultaneously in response to the swing of the single first swing member 47A.

[0076] The third intake valve 14C abuts against one of the two second abutment portions 47b2 of the second pivoting member 47B. The fourth intake valve 14D abuts against the other of the two second abutment portions 47b2 of the second pivoting member 47B. This allows the third intake valve 14C and the fourth intake valve 14D to operate simultaneously in response to the pivoting of one second pivoting member 47B.

[0077] The first intake valve 14A and the second intake valve 14B are respectively arranged in two first intake passages that communicate with the interior of the above-mentioned first cylinder structure 41. The third intake valve 14C and the fourth intake valve 14D are respectively arranged in two second intake passages that communicate with the interior of the above-mentioned second cylinder structure 42.

[0078] The first exhaust valve 15A is arranged in a first exhaust passage that communicates with the interior of the above-mentioned first cylinder structure 41. The second exhaust valve 15B is arranged in a second exhaust passage that communicates with the interior of the above-mentioned second cylinder structure 42.

[0079] In this way, two intake valves 14 and one exhaust valve 15 are provided for each cylinder structure in the opposed-piston engine 1. Specifically, two intake valves (first intake valve 14A and second intake valve 14B) and one exhaust valve (first exhaust valve 15A) are provided for the first cylinder structure 41. Also, two intake valves (third intake valve 14C and fourth intake valve 14D) and one exhaust valve (second exhaust valve 15B) are provided for the second cylinder structure 42.

[0080] In the above embodiment, the case where one valve is the intake valve 14 and the other valve is the exhaust valve 15 has been described, but one valve may be the intake valve 14 and the other valve may be the exhaust valve 15. In this case, the base end of the exhaust valve 15 is able to abut against the second abutment portion 47b2 of the swinging member 47, and the exhaust valve 15 operates in conjunction with the swinging member 47. In addition, the base end of the intake valve 14 abuts against the rocker arm 23, and the intake valve 14 operates in conjunction with the rocker arm 23.

[0081] 9, 11, and 12, the power transmission mechanism 20 is provided across the first crankshaft 9A and the second crankshaft 9B in the arrangement direction of the first piston 8A and the second piston 8B. In other words, the power transmission mechanism 20 overlaps with the first crankshaft 9A and the second crankshaft 9B in the arrangement direction of the first piston 8A and the second piston 8B. More specifically, one end (front end) of the power transmission mechanism 20 in the arrangement direction (front-rear direction) of the first piston 8A and the second piston 8B overlaps with the first crankshaft 9A. Furthermore, the other end (rear end) of the power transmission mechanism 20 in the arrangement direction (front-rear direction) of the first piston 8A and the second piston 8B overlaps with the second crankshaft 9B.

[0082] Specifically, the rocker arm 23 of the power transmission mechanism 20 overlaps with the second crankshaft 9B in the arrangement direction of the first piston 8A and the second piston 8B. The camshaft 21 of the power transmission mechanism 20 overlaps with the first crankshaft 9A in the arrangement direction of the first piston 8A and the second piston 8B. Furthermore, one end 22a (front end) of the push rod 22 of the power transmission mechanism 20 overlaps with the first crankshaft 9A in the arrangement direction of the first piston 8A and the second piston 8B. The other end 22b (rear end) of the push rod 22 of the power transmission mechanism 20 overlaps with the second crankshaft 9B in the arrangement direction of the first piston 8A and the second piston 8B.

[0083] As shown in Figures 8, 9, 11, and 12, when the first piston 8A and the second piston 8B are at their closest positions, the power transmission mechanism 20 is such that the positions of the first piston 8A and the second piston 8B in the alignment direction overlap with the crank arm 93 and crank pin 91 of the first crankshaft 9A and also overlap with the crank arm 93 and crank pin 91 of the second crankshaft 9B.

[0084] As shown in Figures 9, 11, and 12, the opposed-piston engine 1 is equipped with a spark plug 50. The spark plug 50 is disposed near a space S1 (see Figures 11 and 12) formed between the front upper portion of the first piston 8A and the rear upper portion of the second piston 8B when the first piston 8A and the second piston 8B are in close proximity to each other. The spark plug 50 includes a first spark plug 50A and a second spark plug 50B. The first spark plug 50A is provided at a position corresponding to the first piston pair 81 (see Figure 7). The second spark plug 50B is provided at a position corresponding to the second piston pair 82 (see Figure 7).

[0085] As shown in Figures 9 to 12, the opposed-piston engine 1 includes an injection nozzle 51. The injection nozzle 51 is disposed above the first crankshaft 9A. The injection nozzle 51 injects fuel toward a space S1 (see Figures 11 and 12) formed between the front upper portion of the first piston 8A and the rear upper portion of the second piston 8B when the first piston 8A and the second piston 8B are in close proximity to each other. The injection nozzle 51 includes a first injection nozzle 51A and a second injection nozzle 51B. The first injection nozzle 51A is provided corresponding to the first piston pair 81. The second injection nozzle 51B is provided corresponding to the second piston pair 82. The first injection nozzle 51A and the second injection nozzle 51B are connected by a connecting member 52.

[0086] The opposed-piston engine 1 is a four-stroke engine that operates by repeating an intake stroke, compression stroke, combustion stroke, and exhaust stroke. During the intake stroke, the intake valve 14 opens just before the first piston 8A and the second piston 8B move away from each other, and an air-fuel mixture is drawn into the cylinder 4 through the injection nozzle 51. After the intake of the mixture is completed (when the first piston 8A and the second piston 8B are at their furthest positions), the intake valve 14 closes. During the compression stroke, the first piston 8A and the second piston 8B move toward each other, compressing the mixture drawn into the cylinder 4. During the combustion stroke, a spark generated by the spark plug 50 ignites the compressed mixture, and the first piston 8A and the second piston 8B move away from each other due to the combustion of the mixture. During the exhaust stroke, the exhaust valve 15 opens just before the first piston 8A and the second piston 8B start moving toward each other, and the combustion gas is discharged from the cylinder 4. Immediately after the exhaust of the combustion gas is completed (when the first piston 8A and the second piston 8B are at their closest positions), the exhaust valve 15 closes.

[0087] By repeating the above four steps, the opposed-piston engine 1 causes the first crankshaft 9A and the second crankshaft 9B to rotate in opposite directions. The rotational power of the first crankshaft 9A is taken from the first output shaft 3A. The rotational power of the second crankshaft 9B is taken from the second output shaft 3B. As a result, the first output shaft 3A and the second output shaft 3B of the opposed-piston engine 1 rotate in opposite directions.

[0088] As shown in Figures 8 to 12, the opposed-piston engine 1 is equipped with a decompression device 60. The decompression device 60 reduces the pressure in the cylinder 4 when the opposed-piston engine 1 is started. More specifically, the decompression device 60 reduces the pressure in the cylinder 4 by releasing the air compressed in the cylinder 4 to the outside of the cylinder 4 when the opposed-piston engine 1 is started (or immediately before starting). The air released by the decompression device 60 is discharged to the outside of the engine block 2 through the exhaust passage 6.

[0089] In this way, by using the decompression device 60 to reduce the pressure in the cylinder 4 when the opposed-piston engine 1 is started, the load on the starter (cell motor) of the opposed-piston engine 1 mounted on the flight device 101 can be reduced.

[0090] As shown in Figure 17, the decompression device 60 has a decompression valve 61. The decompression valve 61 moves relative to the cylinder 4 to allow air compressed in the cylinder 4 to escape from the cylinder 4. The decompression valve 61 has a decompression valve body 61a and a spring 61b that biases the decompression valve body 61a. The spring 61b biases the decompression valve body 61a in the direction that closes the decompression valve 61. The decompression valve body 61a of the decompression valve 61 moves relative to the cylinder 4 against the biasing force of the spring 61b by being driven by an actuator 65, which will be described later.

[0091] The decompression valve 61 includes a first decompression valve 61A and a second decompression valve 61B. As shown in Figure 9, the first decompression valve 61A and the second decompression valve 61B are arranged parallel to each other and spaced apart in the extension direction (left-right direction) of the camshaft 21. The first decompression valve 61A allows air within the first cylinder structure 41 (see Figure 7) to escape to the outside. The second decompression valve 61B allows air within the second cylinder structure 42 (see Figure 7) to escape to the outside.

[0092] As shown in FIG. 17 , the decompression device 60 further includes a connecting member 62, a shaft 63, a rocker cam 64, and an actuator 65. The connecting member 62 connects the decompression valve body 61a of the first decompression valve 61A (hereinafter referred to as the “first decompression valve body 61a1”) to the decompression valve body 61a of the second decompression valve 61B (hereinafter referred to as the “second decompression valve body 61a2”). A cam surface 64a of the rocker cam 64 abuts the connecting member 62. The cam surface 64a is formed into a substantially arc shape in a plan view. The rocker cam 64 is fixed to a shaft 63 extending in the vertical direction. The shaft 63 rotates around its vertical axis. A lower portion of the shaft 63 is disposed inside the engine block 2, and an upper portion of the shaft 63 is disposed outside the engine block 2 (see FIG. 2 ).

[0093] The cam surface 64a is not an arcuate surface at a constant distance from the shaft body 63, but rather the distance from the shaft body 63 gradually increases from one end 64b to the other end 64c along the arc. The oscillating cam 64 oscillates in conjunction with the rotation of the shaft body 63 and presses the decompression valve 61. More specifically, when the oscillating cam 64 oscillates in one direction (the direction of arrow A3) in conjunction with the rotation of the shaft body 63, it presses the decompression valve 61 via the connecting member 62.

[0094] The actuator 65 is an electric actuator. More specifically, the actuator 65 is an electric cylinder device. The operation of the actuator 65 is controlled by a control device (not shown) that controls the operation of the engine 1. As shown in FIGS. 9, 11, and 12, the actuator 65 is disposed above the second crankshaft 9B. As shown in FIGS. 1 and 2, the actuator 65 is disposed outside the engine block 2.

[0095] As shown in FIG. 17 , the actuator 65 has a rod 65a. The rod 65a is extendable in a direction toward (rearward) and away from (forward) the decompression valve 61. As shown in FIG. 9 , the rod 65a extends in the direction in which the first piston 8A and the second piston 8B are aligned (front-rear direction). One end of a connecting member 66 is attached to the tip of the rod 65a. The other end of the connecting member 66 is attached to a rocking plate 67. The rocking plate 67 is attached to the upper part of the shaft body 63. The rocking plate 67 has a first attachment portion 67a attached to the connecting member 66 and a second attachment portion 67b attached to the rocking plate 67.

[0096] 9 and 17 show the state in which the rod 65a of the actuator 65 is extended. In this state, the decompression valve 61 is closed. When the rod 65a is retracted from this state, the oscillating plate 67 oscillates in the direction of arrow A1, with the second mounting portion 67b as the fulcrum. This causes the shaft 63 to rotate around its axis in the direction of arrow A2, and the oscillating cam 64 to oscillate in the direction of arrow A3. This causes the cam surface 64a of the oscillating cam 64 to press the connecting member 62. When the connecting member 62 is pressed, the decompression valve body 61a is pressed. This causes the decompression valve body 61a to move in the direction of arrow A4 against the biasing force of the spring 61b, opening the decompression valve 61.

[0097] When the rod 65a extends from an open state of the decompression valve 61, the rocker plate 67 rocks in the direction opposite to the arrow A1, with the second mounting portion 67b as the fulcrum. This causes the shaft 63 to rotate around its axis in the direction opposite to the arrow A2, and the rocker cam 64 rocks in the direction opposite to the arrow A3. This releases the cam surface 64a of the rocker cam 64 from pressing against the connecting member 62. The decompression valve body 61a then moves in the direction opposite to the arrow A4 due to the biasing force of the spring 61b, and the decompression valve 61 closes.

[0098] Here, the first decompression valve body 61a1 and the second decompression valve body 61a2 are connected by the connecting member 62, so the first decompression valve body 61a1 and the second decompression valve body 61a2 move integrally, which allows the single actuator 65 to operate (open and close) the two decompression valves 61 simultaneously.

[0099] Note that, instead of the above-described configuration (in which the decompression valve 61 opens when the rod 65a contracts and closes when the rod 65a expands), the decompression device 60 may be configured so that the decompression valve 61 opens when the rod 65a expands and closes when the rod 65a contracts. Such a configuration can be realized, for example, by making the distance of the cam surface 64a from the shaft 63 gradually smaller from one end 64b to the other end 64c in the direction along the arc.

[0100] As shown in Figures 8, 9, 11, and 12, in the arrangement direction of the first piston 8A and the second piston 8B, at least a portion of the power transmission mechanism 20 is disposed on the first crankshaft 9A side, and the decompression device 60 is disposed on the second crankshaft 9B side. In other words, at least a portion of the power transmission mechanism 20 and the decompression device 60 are disposed separately on the first crankshaft 9A side and the second crankshaft 9B side. In this embodiment, "at least a portion of the power transmission mechanism 20" includes the camshaft 21. Therefore, the camshaft 21 and the decompression device 60 are disposed separately on the first crankshaft 9A side and the second crankshaft 9B side.

[0101] Specifically, "at least a part of the power transmission mechanism 20" is the camshaft 21 and one end 22a of the push rod 22. Therefore, the camshaft 21, one end 22a of the push rod 22, and the decompression device 60 are arranged separately on the first crankshaft 9A side and the second crankshaft 9B side.

[0102] 9, the decompression valve 61 is disposed between the first push rod 22A and the second push rod 22B in the extension direction (left-right direction) of the camshaft 21. The decompression valve 61 is also disposed between the first exhaust valve 15A and the second exhaust valve 15B in the extension direction of the camshaft 21. The decompression valve 61 is also disposed between the first crankshaft 9A and the second crankshaft 9B in the arrangement direction (front-rear direction) of the first piston 8A and the second piston 8B, and is disposed closer to the second crankshaft 9B than the first crankshaft 9A.

[0103] As shown in Figure 10, the shaft 63 of the decompression device 60 is disposed between the first rocker arm 23A and the second rocker arm 23B. The shaft 63 extends in the up-down direction, passing between the first rocker arm 23A and the second rocker arm 23B. The shaft 63 is disposed above the first crankshaft 9A. As shown in Figures 11 and 12, the shaft 63 is disposed in a position overlapping with the second crankshaft 9B in the arrangement direction (front-rear direction) of the first piston 8A and the second piston 8B.

[0104] As shown in Figures 1 to 6 and 18, an oil pan 70 is provided below the engine block 2. The oil pan 70 is provided on only one of the two sides in the width direction (front-rear direction) of the engine block 2 (the left side of the paper in Figure 3). As a result, in the opposed-piston engine 1, the side where the oil pan 70 is provided (the left side of the paper in Figure 3) protrudes downward further than the side where the oil pan 70 is not provided (the right side of the paper in Figure 3). In other words, in the opposed-piston engine 1, the lower end (bottom surface) of the side where the oil pan 70 is provided is lower than the lower end (bottom surface) of the side where the oil pan 70 is not provided.

[0105] In this embodiment, the "width direction of the engine block 2" is the direction in which the first piston 8A and the second piston 8B are arranged (front-to-rear direction). Furthermore, "one side in the width direction of the engine block 2" is the rear side of the engine block 2. "The other side in the width direction of the engine block 2" is the front side of the engine block 2. In other words, the oil pan 70 is provided only in the rear part of the engine block 2.

[0106] However, "one side in the width direction of the engine block 2" may be the front side of the engine block 2. In this case, the oil pan 70 is provided only in the front part of the front and rear parts of the engine block 2. Furthermore, the "width direction of the engine block 2" is not limited to the direction in which the first piston 8A and the second piston 8B are arranged, and may be, for example, a direction perpendicular to the arrangement direction (left-right direction). In this case, the oil pan 70 is provided only in the left part or only in the right part of the left and right parts of the engine block 2.

[0107] As described above, the first crankshaft 9A and the second crankshaft 9B are arranged parallel to each other and spaced apart in the alignment direction of the first piston 8A and the second piston 8B (see FIG. 9 , etc.). In this embodiment, the alignment direction of the first piston 8A and the second piston 8B is the width direction of the engine block 2. Therefore, the first crankshaft 9A and the second crankshaft 9B are arranged parallel to each other and spaced apart in the width direction of the engine block 2. The first crankshaft 9A is arranged on one side of the engine block 2 in the width direction. The second crankshaft 9B is arranged on the other side of the engine block 2 in the width direction. Therefore, the oil pan 70 is provided only on the first crankshaft 9A side of the first crankshaft 9A and the second crankshaft 9B.

[0108] As described above, the camshaft 21 is disposed only on the first crankshaft 9A side in the direction in which the first piston 8A and the second piston 8B are aligned. Therefore, the oil pan 70 is disposed on the camshaft 21 side in the direction in which the first piston 8A and the second piston 8B are aligned. The oil pan 70 is disposed in a position overlapping and below the camshaft 21. In other words, the camshaft 21 is disposed above the oil pan 70.

[0109] In this embodiment, the oil pan 70 is integrated with the engine block 2. In other words, the oil pan 70 is made of the same material as the engine block 2. This same material is a member that integrally includes a portion (upper portion) that constitutes the engine block 2 and a portion (lower portion) that constitutes the oil pan 70. However, the oil pan 70 and the engine block 2 may be made of separate members, and the member that constitutes the oil pan 70 may be connected to the lower portion of the member that constitutes the engine block 2.

[0110] In this embodiment, the oil pan 70 is integrated with the first block 2A of the engine block 2. In other words, the oil pan 70 is made of the same material (single material) as the first block 2A. Of the three blocks (first block 2A, second block 2B, and third block 2C) that make up the engine block 2, the oil pan 70 is only located below the first block 2A.

[0111] As shown in Figures 3, 18, etc., the engine block 2 has an inclined portion 71. The inclined portion 71 is formed in the lower portion of the engine block 2. Of the multiple blocks that make up the engine block 2, the inclined portion 71 is formed in a block that is different from the block (first block 2A) on which the oil pan 70 is disposed (integrated with the lower portion). More specifically, the inclined portion 71 is formed in a block that is adjacent to the block (first block 2A) on which the oil pan 70 is disposed (integrated with the lower portion). Specifically, the inclined portion 71 is formed in the lower portion of the second block 2B among the first block 2A, second block 2B, and third block 2C.

[0112] As described above, the oil pan 70 is disposed below (integrated with) one of the blocks (first block 2A). The inclined portion 71 is formed below another block (second block 2B) adjacent to the one of the blocks (first block 2A).

[0113] As shown in Figure 5, the inner bottom surface 72 of the inclined portion 71 is inclined so as to become lower from the other side (front side) to one side (rear side) in the width direction of the engine block 2. The inner bottom surface 72 of the inclined portion 71 is also connected to an inner wall surface 70b that rises from the inner bottom surface 70a of the oil pan 70. As a result, oil (lubricating oil) that has accumulated on the inner bottom surface on the other side in the width direction of the engine block 2 flows along the inner bottom surface 72 of the inclined portion 71 toward one side in the width direction of the engine block 2 (see arrow C1 in Figure 5), flows down into the oil pan 70, and accumulates inside the oil pan 70.

[0114] As described above, the inclined portion 71 is provided in the second block 2B of the engine block 2. As shown in FIG. 5 , the inner bottom surface of the third block 2C of the engine block 2 is located higher than the inner bottom surface of the second block 2B. The inner bottom surface 72 of the inclined portion 71 slopes downward from the third block 2C side of the second block 2B toward the first block 2A side. The height of the upper end of the inner bottom surface 72 of the inclined portion 71 is equal to the height of the inner bottom surface of the third block 2C. The height of the lower end of the inner bottom surface 72 of the inclined portion 71 is equal to the height of the upper end of the oil pan 70 on the inclined portion 71 side (front side). As a result, oil accumulated on the inner bottom surfaces of the second block 2B and the third block 2C flows from the third block 2C side toward the first block 2A side and down into the oil pan 70.

[0115] 5 and 19 , a protruding plate 70c is provided on an inner wall surface 70b that rises from the inner bottom surface 70a of the oil pan 70. Specifically, the protruding plate 70c is provided on the inner wall surface 70b on the front side of the oil pan 70 (the other side in the width direction of the engine block 2). The protruding plate 70c is provided to protrude from the inner wall surface 70b of the oil pan 70.

[0116] As shown in Fig. 5, the protruding plate 70c extends in a direction (rearward) away from the inner wall surface 70b. In this embodiment, the protruding plate 70c extends horizontally, but may also be inclined downward as it moves away from the inner wall surface 70b. As shown in Fig. 19, the protruding plate 70c is provided over the entire length in the depth direction (left-right direction) perpendicular to the width direction of the engine block 2. This improves the strength of the oil pan 70.

[0117] As shown in FIG. 5 , the protruding plate 70c is provided on the upper portion of the inner wall surface 70b of the oil pan 70. The upper surface of the protruding plate 70c is provided at a height slightly lower than the lower end of the inner bottom surface 72 of the inclined portion 71. The oil flowing along the inner bottom surface 72 of the inclined portion 71 first flows down onto the upper surface of the protruding plate 70c and then flows down from the protruding plate 70c toward the inner bottom surface 70a of the oil pan 70. This allows the protruding plate 70c to reduce the momentum (flow rate) of the oil flowing down along the inclined portion 71 toward the oil pan 70. Furthermore, the oil flowing down along the inclined portion 71 toward the oil pan 70 can be dispersed in the depth direction of the engine block 2 before flowing down.

[0118] 4, 18, and 19, the inclined portion 71 is provided only on a portion of the depth direction (left-right direction) of the engine block 2. Specifically, the inclined portion 71 is provided on one side in the depth direction perpendicular to the width direction of the engine block 2. In this embodiment, the inclined portion 71 is provided on the left side of the engine block 2.

[0119] The width W1 of the inclined portion 71 in the depth direction (left-right direction) of the engine block 2 is smaller than the overall width of the engine block 2. Furthermore, the width W1 of the inclined portion 71 in the depth direction (left-right direction) of the engine block 2 is smaller than the overall width of the oil pan 70. As shown in Figures 4 and 19, the inclined portion 71 is formed to have a U-shaped cross section. As a result, the inner bottom surface 72 of the inclined portion 71 is located lower than the inner bottom surface of the portion of the second block 2B where the inclined portion 71 is not provided.

[0120] In this way, by forming the inclined portion 71 with a narrow width and a U-shaped cross section, oil that has accumulated inside the inclined portion 71 can be quickly and reliably discharged toward the oil pan 70. Furthermore, compared to when the inclined portion 71 is provided across the entire width of the engine block 2 in the depth direction, the engine block 2 can be made more compact.

[0121] In the above embodiment, a configuration in which the oil pan 70 is provided on only one of the widthwise sides of the engine block 2 has been described as being applied to the opposed-piston engine 1. However, the above-described configuration in which the oil pan 70 is provided on only one of the widthwise sides of the engine block 2 can also be applied to engines other than opposed-piston engines.

[0122] The opposed-piston engine 1 according to the above-described embodiment can be used, for example, as a driving source for a flying device. The opposed-piston engine 1 can also be used as a driving source for devices other than flying devices, such as automobiles (including work vehicles), ships, and other industrial machinery.

[0123] Below, a flying device 101 equipped with the opposed-piston engine 1 will be described as an example of a suitable application of the opposed-piston engine 1. The flying device 101 is an unmanned flying device. More specifically, the flying device 101 is a multicopter known as a drone. The flying device 101 may fly by remote control using wireless or wired communication, or it may fly by autonomous control without relying on a remote device.

[0124] 20 to 26 are diagrams showing an example of a flying device 101 equipped with the above-mentioned opposed-piston engine 1. As shown in Figures 20 to 23, the flying device 101 comprises an airframe 102 and a rotor 103 attached to the airframe 102. The airframe 102 has a main body 106 and a plurality of arms 107 extending from the main body 106.

[0125] The main body 106 is formed by combining a plurality of frame members. As shown in Figures 20 to 26, the opposed-piston engine 1 is mounted on the main body 106. A skid 110 is attached to the lower part of the main body 106. The skid 110 comes into contact with the ground when the flight device 101 lands, and supports the airframe 102 by floating it above a landing surface such as the ground.

[0126] 20 , the arms 107 extend in a direction away from the main body 106 in a plan view. In the present embodiment, there are four arms 107. A rotor 103 and a motor 105 are attached to each of the arms 107.

[0127] The rotor 103 includes a main rotor 103A and a sub-rotor 103B. The main rotor 103A is a rotor for generating lift to lift the airframe 102. The sub-rotor 103B is a rotor for controlling the attitude of the airframe 102. The main rotor 103A is attached to the main body 106. The sub-rotor 103B is attached to an arm 107. The main rotor 103A rotates by a driving force supplied from the opposed-piston engine 1. The sub-rotor 103B rotates by a driving force supplied from the motor 105.

[0128] 20 , two main rotors 103A are arranged around the airframe 102 in a plan view. Hereinafter, the two main rotors 103A will be referred to as the first main rotor 103A1 and the second main rotor 103A2, respectively. The first main rotor 103A1 and the second main rotor 103A2 are arranged symmetrically across the center of the airframe 102. The first main rotor 103A1 and the second main rotor 103A2 rotate in opposite directions.

[0129] As shown in Figure 20, four sub-rotors 103B are arranged at equal distances from the center of the airframe 102 in a plan view. The sub-rotors 103B are attached to each of the multiple (four) arms 107. As shown in Figures 21 to 23, two sub-rotors 103B are attached to each arm 107. Each sub-rotor 103B has an upper rotor 103BU and a lower rotor 103BL.

[0130] The motor 105 that supplies driving force to the sub-rotor 103B is an electric motor that is driven by power supplied from a battery 146 (described later). The motor 105 includes a first motor 105A and a second motor 105B. The first motor 105A supplies driving force to the upper rotor 103BU. The second motor 105B supplies driving force to the lower rotor 103BL.

[0131] The first output shaft 3A and the second output shaft 3B of the opposed-piston engine 1 extend from the main body 106. The first output shaft 3A supplies driving force to the first main rotor 103A1. The second output shaft 3B supplies driving force to the second main rotor 103A2. The rotation of the first output shaft 3A is transmitted to the first main rotor 103A1 via a first power transmission unit 138 (see FIGS. 22 and 23) consisting of a gear mechanism or the like. This causes the first main rotor 103A1 to rotate. The rotation of the second output shaft 3B is transmitted to the second main rotor 103A2 via a second power transmission unit 139 (see FIGS. 22 and 23) consisting of a gear mechanism or the like. This causes the second main rotor 103A2 to rotate. In this way, the two main rotors (the first main rotor 103A1 and the second main rotor 103A2) are driven by the two output shafts (the first output shaft 3A and the second output shaft 3B) of one opposed-piston engine 1.

[0132] The flying device 101 is equipped with a radiator 140 as a cooling device that water-cools the engine 1. The radiator 140 is disposed on the sides (left and right) of the main body 106. The flying device 101 also has air guide members 144 that guide the downward airflow generated by the rotation of the main rotor 103A toward the radiator 140.

[0133] As shown in Figures 22 to 25, the flight device 101 is equipped with a battery 146 that stores power supplied to the motor 105. As shown in Figure 25, the battery 146 includes a first battery 146A and a second battery 146B. The first battery 146A is disposed on one side (left) of the opposed-piston engine 1 in a plan view. The second battery 146B is disposed on the other side (right) of the opposed-piston engine 1 in a plan view. In this way, the two batteries 146 (first battery 146A, second battery 146B) are disposed so as to sandwich the opposed-piston engine 1 in a plan view.

[0134] The first battery 146A stores the electric power generated by the first generator 12A, and the second battery 146B stores the electric power generated by the second generator 12B.

[0135] As shown in Figures 24 and 26, the batteries 146 (first battery 146A, second battery 146B) are located on either side of the oil pan 70. The two batteries 146 are disposed on one side (left) and the other side (right) of the oil pan 70, respectively. Note that Figure 26 only shows the battery (first battery 146A) disposed on one side (left) of the oil pan 70. Also, the radiator 140 and the air guide member 144 are omitted from Figure 26.

[0136] 24 and 26 , the battery 146 is vertically positioned so as to overlap the oil pan 70. In other words, the height of the bottom end of the oil pan 70 is lower than the height of the top end of the battery 146, but higher than the height of the bottom end of the battery 146.

[0137] As shown in Figure 26, the main body 106 of the flight device 101 is equipped with electrical equipment 120. In this embodiment, the electrical equipment 120 is a battery controller that controls the battery 146. The battery controller controls, for example, the current and voltage when charging the battery 146. However, the electrical equipment 120 is not limited to a battery controller. For example, the electrical equipment 120 may be a control device that controls the drive of the opposed-piston engine 1 or a control device that controls the drive of the motor 105. Alternatively, the electrical equipment 120 may be an electrical device other than a control device.

[0138] 26 , the electrical equipment (battery controller) 120 is disposed below the opposed-piston engine 1 and on the other widthwise side (front side) of the engine block 2. The electrical equipment 120 also overlaps the oil pan 70 in the vertical direction. In other words, the height of the upper end of the electrical equipment 120 is higher than the height of the lower end of the oil pan 70, but lower than the height of the upper end of the oil pan 70.

[0139] As described above, the oil pan 70 of the opposed-piston engine 1 is provided on only one of the widthwise sides of the engine block 2. Therefore, a space S2 is created below the other widthwise side of the engine block 2 (the side where the oil pan 70 is not provided), and the electrical equipment 120 is disposed in this space S2. In this way, in the opposed-piston engine 1, because the oil pan 70 is provided only on one widthwise side of the engine block 2, a space for disposing the electrical equipment 120 can be secured below the other widthwise side of the engine block 2.

[0140] 26 , the oil pan 70 of the opposed-piston engine 1 is positioned offset to one side in the horizontal direction (rearward) from the vertical central axis CL1 of the main body 106 on which the engine 1 is mounted. In other words, the opposed-piston engine 1 is positioned such that the vertical central axis CL2 of the oil pan 70 is eccentric to the vertical central axis CL1 of the main body 106. This ensures that the space S2 formed below the other widthwise side of the engine block 2 within the interior space of the main body 106 is wide in the horizontal direction, making it possible to easily arrange devices including electrical equipment 120 in this space.

[0141] The main configurations and effects of the opposed-piston engine 1 and the flight device 101 equipped with this engine according to the above-described embodiment will be briefly summarized below.

[0142] The opposed-piston engine 1 comprises a cylinder 4, a first piston 8A arranged in the cylinder 4, a second piston 8B arranged in the cylinder 4 opposite the first piston 8A, a first crankshaft 9A that rotates with the reciprocating motion of the first piston 8A, a second crankshaft 9B that rotates with the reciprocating motion of the second piston 8B, a valve 13 that operates relative to the cylinder 4 to perform intake or exhaust, and a power transmission mechanism 20 that transmits the rotational power of the first crankshaft 9A to the valve 13 to operate the valve 13, the first crankshaft 9A and the second crankshaft 9B being arranged at an interval in the alignment direction of the first piston 8A and the second piston 8B, and the power transmission mechanism 20 being provided across the first crankshaft 9A and the second crankshaft 9B in the alignment direction.

[0143] With this configuration, the power transmission mechanism 20 that transmits the rotational power of the first crankshaft 9A to the valves 13 to operate them is provided across the first crankshaft 9A and the second crankshaft 9B in the alignment direction of the first piston 8A and the second piston 8B, so that the power transmission mechanism 20 that transmits the rotational power of the crankshaft 9 to the valves can be made smaller. For example, the power transmission mechanism 20 can be made smaller than in the case of a valve drive mechanism in which timing belts are wound around the crank pulleys of the two crankshafts.

[0144] The power transmission mechanism 20 also has a camshaft 21 that rotates in conjunction with the rotation of the first crankshaft 9A, a push rod 22 that reciprocates in conjunction with the rotation of the camshaft 21, and a rocker arm 23 that connects the push rod 22 to the valve 13, with one end 22a of the push rod 22 being arranged on the first crankshaft 9A side and the other end 22b of the push rod 22 being arranged on the second crankshaft 9B side, and the rocker arm 23 connecting the other end 22b to the valve 13 on the second crankshaft 9B side.

[0145] With this configuration, the mechanism that cooperates with one end 22a of the push rod 22 and the mechanism that cooperates with the other end 22b of the push rod 22 can be separately arranged on the first crankshaft 9A side and the second crankshaft 9B side. Also, because the rocker arm 23 that constitutes the mechanism that cooperates with the other end 22b of the push rod 22 is arranged on the second crankshaft 9B side, space for arranging the camshaft 21 can be secured on the first crankshaft 9A side.

[0146] The camshaft 21 is composed of a single camshaft that is disposed on the first crankshaft 9A side in the arrangement direction.

[0147] This configuration reduces the space required for arranging the camshaft 21 compared to arranging the camshaft 21 on both the first crankshaft 9A side and the second crankshaft 9B side. Furthermore, by arranging the rocker arm 23 on the second crankshaft 9B side and then arranging the camshaft 21 on the first crankshaft 9A side, the components of the power transmission mechanism can be distributed and arranged in a balanced manner between the first crankshaft 9A side and the second crankshaft 9B side. This allows the opposed-piston engine 1 to be made more compact.

[0148] The valves 13 include an intake valve 14 and an exhaust valve 15 , and the intake valve 14 and the exhaust valve 15 operate in accordance with the rotation of a single camshaft 21 .

[0149] With this configuration, the intake valve 14 and the exhaust valve 15 can be operated in conjunction with the rotation of a single camshaft 21, so the operating mechanisms for the intake valve 14 and the exhaust valve 15 can be configured compactly.

[0150] The camshaft 21 has a shaft 30 and a cam 31 provided on the shaft 30 , and one end of the push rod 22 is disposed in contact with the cam 31 .

[0151] According to this configuration, one end of the push rod 22 is positioned in contact with the cam 31 of the camshaft 21, so that the cam 31 of the camshaft 21, which is a mechanism that works in conjunction with one end 22a of the push rod 22, and the rocker arm 23, which is a mechanism that works in conjunction with the other end 22b of the push rod 22, can be distributed and positioned in a balanced manner on the first crankshaft 9A side and the second crankshaft 9B side.

[0152] Furthermore, the base end of one of the intake valves 14 and exhaust valves 15 is in contact with the rocker arm 23 , and the base end of the other valve is positioned so as to be pressed by the cam 31 .

[0153] According to this configuration, one of the intake valve 14 and the exhaust valve 15 can be linked to the rocker arm 23 and the other valve can be linked to the camshaft 21.

[0154] One valve is an exhaust valve 15 and the other valve is an intake valve 14 .

[0155] With this configuration, the exhaust valve 15 can be linked to the rocker arm 23 and the intake valve 14 can be linked to the camshaft 21.

[0156] The first piston 8A and the second piston 8B are arranged side by side in the horizontal direction, and the camshaft 21 is arranged above the first crankshaft 9A.

[0157] With this configuration, the first piston 8A and the second piston 8B are arranged side by side in the horizontal direction, thereby reducing the height of the opposed-piston engine 1. Furthermore, by locating the camshaft 21 above the first crankshaft 9A, power can be transmitted smoothly from the first crankshaft 9A to the camshaft 21 over a short distance.

[0158] In addition, the push rod 22 includes a first push rod 22A and a second push rod 22B, and the cam 31 includes a first cam 31A and a second cam 31B spaced apart in the extension direction of the camshaft 21, with one end of the first push rod 22A being positioned in contact with the first cam 31A and one end of the second push rod 22B being positioned in contact with the second cam 31B.

[0159] According to this configuration, rotation of the single camshaft 21 can cause both the first push rod 22A and the second push rod 22B to reciprocate.

[0160] The opposed-piston engine 1 also includes a cylinder 4, a first piston 8A disposed in the cylinder 4, a second piston 8B disposed in the cylinder 4 opposite the first piston 8A, a first crankshaft 9A that rotates with the reciprocating motion of the first piston 8A, a second crankshaft 9B that rotates with the reciprocating motion of the second piston 8B, a valve 13 that operates relative to the cylinder 4 to perform intake or exhaust, a power transmission mechanism 20 that transmits the rotational power of the first crankshaft 9A to the valve 13 to operate the valve 13, and a decompression device 60 that reduces the pressure in the cylinder 4 when the engine 1 is started. The first crankshaft 9A and the second crankshaft 9B are arranged at an interval in the alignment direction of the first piston 8A and the second piston 8B, and in the alignment direction, at least a portion of the power transmission mechanism 20 is arranged on the first crankshaft 9A side, and the decompression device 60 is arranged on the second crankshaft 9B side.

[0161] With this configuration, at least a portion of the power transmission mechanism 20, which transmits the rotational power of the first crankshaft 9A to the valves 13 to operate them, is located at a distance from the decompression device 60, making it possible to reduce the size of the opposed-piston engine 1 equipped with the decompression device 60. More specifically, by distributing at least a portion of the power transmission mechanism 20 and the decompression device 60 between the first crankshaft 9A side and the second crankshaft 9B side, the components of the opposed-piston engine 1 are arranged in a balanced manner, making it possible to make the opposed-piston engine 1 more compact.

[0162] The power transmission mechanism 20 also has a camshaft 21 that rotates in conjunction with the rotation of the first crankshaft 9A, a push rod 22 that reciprocates in conjunction with the rotation of the camshaft 21, and a rocker arm 23 that connects the push rod 22 to the valve 13.

[0163] With this configuration, the rotational power of the first crankshaft 9A can be transmitted to the valve 13 via the camshaft 21, the push rod 22, and the rocker arm 23.

[0164] Furthermore, one end of the push rod 22 and the camshaft 21 are disposed on the first crankshaft 9A side.

[0165] With this configuration, the decompression device 60 is disposed on the second crankshaft 9B side, and one end of the push rod 22 and the camshaft 21 are disposed on the first crankshaft 9A side. This allows the decompression device 60 and the camshaft 21 to be distributed and positioned in a balanced manner between the first crankshaft 9A side and the second crankshaft 9B side. This allows the opposed-piston engine 1 to be made more compact.

[0166] The other end of the push rod 22 is disposed on the second crankshaft 9B side, and the rocker arm 23 connects the other end to the valve 13 on the second crankshaft 9B side.

[0167] With this configuration, one end of the push rod 22 and the camshaft 21 can be disposed on the first crankshaft 9A side, and the other end of the push rod 22 and the rocker arm 23 can be disposed on the second crankshaft 9B side. Therefore, the camshaft 21 and the rocker arm 23 can be disposed in a well-balanced manner between the first crankshaft 9A side and the second crankshaft 9B side.

[0168] The camshaft 21 is made up of a single camshaft, and the valves 13 include an intake valve 14 and an exhaust valve 15, which operate in conjunction with the rotation of the single camshaft 21.

[0169] With this configuration, the intake valve 14 and the exhaust valve 15 can be operated in conjunction with the rotation of a single camshaft 21, so the operating mechanisms for the intake valve 14 and the exhaust valve 15 can be configured compactly.

[0170] The push rod 22 also includes a first push rod 22A and a second push rod 22B that are spaced apart from each other in the extension direction of the camshaft 21, and the decompression device 60 has a decompression valve 61 that moves relative to the cylinder 4, and the decompression valve 61 is arranged between the first push rod 22A and the second push rod 22B in the extension direction.

[0171] According to this configuration, the decompression valve 61 is disposed between the first push rod 22A and the second push rod 22B in the extension direction of the camshaft 21, so that the operating mechanism of the decompression valve 61 can be disposed without being obstructed by the push rods 22. Furthermore, the space formed between the first push rod 22A and the second push rod 22B can be effectively utilized (used for disposing the decompression valve 61) without being wasted, allowing the opposed-piston engine 1 to be made more compact.

[0172] In addition, the exhaust valve 15 includes a first exhaust valve 15A and a second exhaust valve 15B that are spaced apart from each other in the extension direction, and the decompression valve 61 is disposed between the first exhaust valve 15A and the second exhaust valve 15B in the extension direction.

[0173] According to this configuration, the decompression valve 61 is disposed between the first exhaust valve 15A and the second exhaust valve 15B in the extension direction of the camshaft 21, so that the operating mechanism of the decompression valve 61 can be disposed without being obstructed by the exhaust valves 15. Furthermore, the space formed between the first exhaust valve 15A and the second exhaust valve 15B can be effectively utilized (used for arranging the decompression valve 61) without being wasted, allowing the opposed-piston engine 1 to be made more compact.

[0174] The decompression valve 61 is disposed between the first crankshaft 9A and the second crankshaft 9B in the arrangement direction, and closer to the second crankshaft 9B than the first crankshaft 9A.

[0175] According to this configuration, the decompression valve 61 can be arranged without interfering with the power transmission mechanism 20 arranged on the first crankshaft 9A side.

[0176] The rocker arm 23 also includes a first rocker arm 23A connected to the first push rod 22A and a second rocker arm 23B connected to the second push rod 22B, and the decompression device 60 has a shaft body 63 that extends in the vertical direction and rotates around its axis, and an oscillating cam 64 that oscillates in conjunction with the rotation of the shaft body 63 and presses the decompression valve 61, and the shaft body 63 is arranged between the first rocker arm 23A and the second rocker arm 23B.

[0177] According to this configuration, the operating mechanism of the decompression valve 61 can be placed using the space between the first rocker arm 23A and the second rocker arm 23B, so a large space is not required for placing the decompression device 60.

[0178] Although the embodiments of the present invention have been described above, the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0179] REFERENCE SIGNS LIST 1 opposed piston engine 4 cylinder 8A first piston 8B second piston 9A first crankshaft 9B second crankshaft 13 valve 14 intake valve 15 exhaust valve 20 power transmission mechanism 21 camshaft 22 push rod 22A first push rod 22B second push rod 22a one end of push rod 22b other end of push rod 23 rocker arm 30 shaft 31 cam 31A first cam 31B second cam

Claims

1. An opposed piston engine comprising: a cylinder; a first piston disposed within the cylinder; a second piston disposed within the cylinder opposite the first piston; a first crankshaft rotating with the reciprocating motion of the first piston; a second crankshaft rotating with the reciprocating motion of the second piston; a valve operating relative to the cylinder to perform intake or exhaust; and a power transmission mechanism transmitting the rotational power of the first crankshaft to the valve to operate the valve, wherein the first crankshaft and the second crankshaft are disposed at an interval in the arrangement direction of the first piston and the second piston, and the power transmission mechanism is provided across the first crankshaft and the second crankshaft in the arrangement direction.

2. An opposed-piston engine as described in claim 1, wherein the power transmission mechanism comprises a camshaft that rotates with the rotation of the first crankshaft, a push rod that reciprocates with the rotation of the camshaft, and a rocker arm that connects the push rod and the valve, one end of the push rod is disposed on the first crankshaft side, the other end of the push rod is disposed on the second crankshaft side, and the rocker arm connects the other end and the valve on the second crankshaft side.

3. An opposed-piston engine according to claim 2, wherein the camshaft is constituted by a single camshaft arranged on the first crankshaft side in the arrangement direction.

4. An opposed piston engine according to claim 3, wherein the valves include an intake valve and an exhaust valve, and the intake valve and the exhaust valve operate in accordance with the rotation of the single camshaft.

5. An opposed piston type engine according to any one of claims 2 to 4, wherein the camshaft has a shaft and a cam provided on the shaft, and one end of the push rod is disposed in contact with the cam.

6. An opposed-piston engine as set forth in claim 5 which recites claim 4, wherein the base end of one of the intake valves and the exhaust valve abuts against the rocker arm, and the base end of the other valve abuts against a swinging member which moves in conjunction with the cam.

7. An opposed piston engine as claimed in claim 6, wherein said one valve is said exhaust valve and said other valve is said intake valve.

8. An opposed piston type engine according to any one of claims 2 to 7, wherein the first piston and the second piston are arranged side by side in the horizontal direction, and the camshaft is arranged above the first crankshaft.

9. An opposed piston type engine as claimed in any one of claims 5 to 7, wherein the push rods include a first push rod and a second push rod, the cams include a first cam and a second cam spaced apart in the extension direction of the camshaft, one end of the first push rod is disposed in contact with the first cam, and one end of the second push rod is disposed in contact with the second cam.

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