Crank device

Abstract

To provide a crank device that is resistant against an explosive force of a large exhaust engine.SOLUTION: In a crank device 1, a cylindrical hole 4a in a piston 4 covers a third rotational shaft 6c by 360°, and planetary gear 3 is provided on each of peripheral surfaces 6f, 6g of a first rotational shaft 6a and a second rotational shaft 6b. On an inner peripheral surface of holes 2a, 2b of the crank case, outer peripheral faces 7c, 7d of a columnar eccentric cams 7a, 7b face each other, and through holes 7g, 7h (engagement parts) are provided at a position close to the outer peripheral faces 7c, 7d on plane parts 7e, 7f of the columnar eccentric cams 7a, 7b. The first rotational shaft 6a and the second rotational shaft 6b (separate engagement parts) are then inserted into and engages with the through holes 7g, 7h, respectively.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a crank device. [Background technology]

[0002] Conventionally, technologies have been proposed to reduce vibrations in crank devices and further improve quietness. Such crank devices include a mechanism with an internal sun gear and planetary gears, and an operating part that moves linearly back and forth in response to the rotation and revolution of the planetary gears (Patent Document 1).

[0003] According to Patent Document 1, the crank device 100 moves as shown in Figures 17, 18, 19, and 20, which are schematic longitudinal cross-sectional views, in that order. The internal sun gear 101 has a gear on its inner periphery, which meshes with a gear on the outer periphery of the planetary gear 102. The internal sun gear 101 has an inner periphery that is approximately twice as large as the outer periphery of the planetary gear 102. One end of the piston 103 is rotatably fixed to a position very close to an end face of the disk surface of the planetary gear 102, excluding an end face (same as the outer periphery) of the planetary gear 102. The other end of the piston 103 is inserted through a hole 101a in the internal sun gear 101.

[0004] First, as shown in FIG. 17, planetary gears 102 are positioned above internal sun gear 101. Then, with the inner gear of internal sun gear 101 meshing with the outer gear of planetary gear 102, planetary gear 102 is rotated in the direction of the arrow. This moves planetary gear 102 to the position shown in FIG. 18. At the same time, piston 103 enters the inside of internal sun gear 101. When planetary gear 102 is rotated further in the direction of the arrow, planetary gear 102 moves to the position shown in FIG. 19. At the same time, piston 103 enters further inside internal sun gear 101. When planetary gear 102 is rotated further in the direction of the arrow, planetary gear 102 moves to the position shown in FIG. 20. At the same time, piston 103 moves to the position shown in FIG. 18. When planetary gear 102 is rotated further in the direction of the arrow, planetary gear 102 moves to the position shown in FIG. 17. By repeating these steps, the crank device 100 can be operated, allowing the piston 103 to reciprocate approximately up and down. By allowing the piston 103 to reciprocate approximately up and down, it is possible to reduce vibrations of the crank device 100 and further improve quietness. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-114959 Summary of the Invention [Problem to be solved by the invention]

[0006] The crank device 100 of Patent Document 1 employs the structure shown in the schematic longitudinal cross-sectional view of FIG. 21 to realize the operations shown in FIGS. 17, 18, 19, and 20. In this structure, when the piston 103 moves downward, the first crank 110 is pushed down, and the second crank 111 receives the pushing force. However, the second crank 111 is structurally weak to withstand the pushing force of the first crank 110. For example, the second crank 111 cannot support the area directly below the first crank 110, which weakens the entire crank device 100. As a result, when an engine is operated, the crank device 100 cannot withstand the explosive force of the engine, making it unsuitable for use in large-displacement engines, thereby limiting its range of application.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a crank device that can withstand the explosive force of a large displacement engine. [Means for solving the problem]

[0008] To achieve the above object, the crank device comprises a pair of opposing internal sun gears arranged on the inner peripheral surface of a hole drilled in a crankcase, planetary gears that rotate and revolve while meshing with the internal sun gear, a crank member that supports the planetary gears so that they can rotate and revolve, and a piston that moves back and forth linearly by rotating and revolving the planetary gears while meshing with the internal sun gear, and the crank member has a first rotation shaft and a second rotation shaft that share a common rotation axis at both ends, and a piston that moves back and forth linearly by rotating and revolving with the first rotation shaft and the second rotation shaft. Between them, there is a third rotating shaft having a rotation axis different from that of the first rotating shaft and the second rotating shaft, a first handle connecting the first rotating shaft and the third rotating shaft, and a second handle connecting the second rotating shaft and the third rotating shaft. The piston is slidable in the circumferential direction of the third rotating shaft. The planetary gears are respectively arranged on the circumferential surfaces of the first rotating shaft and the second rotating shaft, and the outer surface of the plate-shaped member faces the inner circumferential surface of the hole in the crankcase. An engaging portion is provided at a position close to the outer circumferential surface of the flat portion of the plate-shaped member, and the engaging portion engages with another engaging portion provided on the first rotating shaft and the second rotating shaft, respectively. [Effects of the Invention]

[0009] The present invention can provide a crank device that can withstand the explosive force of a large displacement engine. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is an exploded perspective view of the crank device according to the embodiment. [Figure 2] FIG. 2 is a right side view of the crank device according to the present embodiment. [Figure 3] 3 is a cross-sectional view taken along the line AA in FIG. 2. [Figure 4] FIG. 2 is a front view of the present embodiment. [Figure 5] 11. FIG. 11 is a cross-sectional view taken along the line BB in FIG. 4 showing the crank device of the present embodiment, and is one of the views showing the manner in which the crank device operates as shown in the order of FIGS. [Figure 6] FIG. 2 is a front view of the crank device according to the embodiment. [Figure 7] 11. FIG. 11 is a cross-sectional view taken along the line BB in FIG. 6 showing the crank device of the present embodiment, and is one of the views showing the operation shown in the order of FIGS. [Figure 8] FIG. 2 is a front view of the crank device according to the embodiment. [Figure 9] 11. FIG. 11 is a cross-sectional view taken along the line BB in FIG. 8 showing the crank device of the present embodiment, and is one of the views showing the manner in which the crank device operates as shown in the order of FIGS. [Figure 10] FIG. 2 is a front view of the crank device according to the embodiment. [Figure 11] 11. FIG. 12 is a cross-sectional view taken along the line BB in FIG. 10 showing the crank device of the present embodiment, and is one of the views showing the manner in which the crank device operates as shown in the order of FIGS. 5, 7, 9, and 11. [Figure 12] FIG. 10 is an exploded perspective view of a crank device having a cantilever structure, which is a modified example of the present embodiment. [Figure 13] FIG. 2 is a left side view of the crank device according to the present embodiment. [Figure 14] 14 is a cross-sectional view taken along CC in FIG. 13. [Figure 15]FIG. 2 is a front view of the crank device according to the embodiment. [Figure 16] FIG. 2 is a right side view of the crank device according to the present embodiment. [Figure 17] 21 is a schematic longitudinal sectional view of a conventional crank device, and is one of the views showing the operation shown in the order of FIGS. 17, 18, 19, and 20. FIG. [Figure 18] 21 is a schematic longitudinal sectional view of a conventional crank device, and is one of the views showing the operation shown in the order of FIGS. 17, 18, 19, and 20. FIG. [Figure 19] 21 is a schematic longitudinal sectional view of a conventional crank device, and is one of the views showing the operation shown in the order of FIGS. 17, 18, 19, and 20. FIG. [Figure 20] 21 is a schematic longitudinal sectional view of a conventional crank device, and is one of the views showing the operation shown in the order of FIGS. 17, 18, 19, and 20. FIG. [Figure 21] FIG. 1 is a schematic vertical cross-sectional view illustrating a structure adopted by a conventional crank device. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Configuration of crank device) The crank device of this embodiment will be described below with reference to Figures 1, 2, and 3. Crank device 1 has holes 2a1 and 2b1 drilled in crankcases 2a and 2b that constitute it. A pair of opposed inner sun gears 2a2 and 2b2 are disposed on the inner circumferential surfaces of holes 2a1 and 2b1. Needless to say, this "pair of opposed" does not refer to the state shown in the exploded perspective view of Figure 1, but rather refers to the state in which the crank device 1 is formed by assembling the various components.

[0012] The crank device 1 also has planetary gear units 3a1 and 3a2 that rotate and revolve around the planetary gear 3 while meshing with the internal sun gears 2a2 and 2b2. The planetary gear units 3a1 and 3a2 are gears that rotate and revolve around the planetary gear 3 while meshing with the internal sun gears 2a2 and 2b2. The piston 4 also makes linear reciprocating motion by rotating and revolving around the planetary gear 3 while meshing with the internal sun gears 2a2 and 2b2.

[0013] The crank member 5 has a first rotating shaft 6a and a second rotating shaft 6b at both ends, which share a common rotation axis. Between the first rotating shaft 6a and the second rotating shaft 6b, there is a third rotating shaft 6c, which has a different rotation axis from the first rotating shaft 6a and the second rotating shaft 6b. Furthermore, a first handle 6d connects the first rotating shaft 6a and the third rotating shaft 6c. Furthermore, a second handle 6e connects the second rotating shaft 6b and the third rotating shaft 6c.

[0014] The planetary gear 3 and planetary gear portion 3a1 are cylindrical, and are inserted into and fixed to the first handle 6d on the first rotating shaft 6a side until the planetary gear 3 contacts the first handle 6d. The planetary gear 3 and planetary gear portion 3a2 are cylindrical, and are inserted into and fixed to the second handle 6e on the second rotating shaft 6b side until the planetary gear 3 contacts the second handle 6e. As a result, the two planetary gears 3 are arranged outside the first handle 6d and the second handle 6e (on the first rotating shaft 6a side and the second rotating shaft 6b side).

[0015] The piston 4 is slidable in the circumferential direction of the third rotating shaft 6c. More specifically, the cylindrical hole 4a of the piston 4 covers the circumferential surface of the third rotating shaft 6c 360°. The planetary gears 3 are disposed on the circumferential surfaces 6f, 6g of the first rotating shaft 6a and the second rotating shaft 6b, respectively. The outer peripheral surface 7c of a cylindrical eccentric cam 7a (plate-shaped member) faces the inner peripheral surface of the hole 2a1 of the crankcase 2a, and a through hole 7g (engagement portion) is provided on the flat surface 7e of the cylindrical eccentric cam 7a at a position close to the outer peripheral surface 7c. The outer peripheral surface 7d of the cylindrical eccentric cam 7b faces the inner peripheral surface of the hole 2b1 of the crankcase 2b, and a through hole 7h (engagement portion) is provided on the flat surface 7f of the cylindrical eccentric cam 7b at a position close to the outer peripheral surface 7d. The first rotating shaft 6a (another engaging portion) is inserted into and engaged with the through-hole 7h, and the second rotating shaft 6b (another engaging portion) is inserted into and engaged with the through-hole 7g. This engagement must not interfere with the rotation and revolution of the planetary gear 3 while meshing with the internal sun gears 2a2, 2b2.

[0016] Here, the outer peripheral surface 7c of the cylindrical eccentric cam 7a and the outer peripheral surface 7d of the cylindrical eccentric cam 7b are divided into gear portions 7c1 and 7d1 that are continuously formed in the circumferential direction and non-gear portions 7c2 and 7d2 that are not continuously formed in the circumferential direction. The gear portions 7c1 and 7d1 do not mesh with the inner sun gears 2a2 and 2b2. The gear portions 7c1 and 7d1 are positioned toward the outside of the holes 2a1 and 2b1 of the crankcases 2a and 2b. The non-gear portions 7c2 and 7d2 are positioned toward the inside of the holes 2a1 and 2b1 of the crankcases 2a and 2b. Of course, even when the cylindrical eccentric cams 7a and 7b are inserted into the holes 2a1 and 2b1 of the crankcases 2a and 2b, the inner sun gears 2a2 and 2b2 are exposed.

[0017] Ideally, the positions of the flat surface 7e of the cylindrical eccentric cam 7a near the outer peripheral surface 7c and the flat surface 7f of the cylindrical eccentric cam 7b near the outer peripheral surface 7d are positions spaced from the cam rotation center axis (the centers of the flat surfaces 7e and 7f of the cylindrical eccentric cams 7a and 7b) by a distance equal to the eccentricity between the first and second rotary shafts 6a and 6b and the third rotary shaft 6c. Positioning the centers of the through holes 7g and 7h at these positions allows the piston 4 to move completely linearly. However, even if the piston 4 does not move completely linearly, allowing the piston 4 to move substantially linearly can sufficiently reduce vibration and improve quietness of the crank mechanism 1. Therefore, the term "near positions" used above refers to both the ideal positions and positions deviated from them.

[0018] The drive unit 8 will now be described. The drive unit 8 has a base 9, a cylindrical rod 10, and handles 11a and 11b for rotating the cylindrical rod 10. The base 9 has two opposing raised portions 9a and 9b. Approximately in the center of the top surfaces 9a1 and 9b1 of the raised portions 9a and 9b, there are cylindrical circumferential recesses 9a2 and 9b2 that can tightly accommodate the cylindrical rod 10. The cylindrical rod 10 is arranged so as to fit into the cylindrical circumferential recesses 9a2 and 9b2. The cylindrical rod 10 can rotate in the circumferential direction while fitted into the cylindrical circumferential recesses 9a2 and 9b2.

[0019] Handles 11a and 11b are fixed to both ends of the cylindrical rod 10. Handles 11a and 11b are flattened cylinders, with gears 11a1 and 11b1 formed along the outer circumferential surface on one of the cylinder's flat surfaces. Handles 11a and 11b have handle portions 11a2 and 11b2 on the other of the cylinder's flat surfaces. Handles 11a and 11b have the same shape, with gears 11a1 and 11b1 facing each other. By rotating handle portions 11a2 and 11b2 in the circumferential direction of cylindrical handles 11a and 11b, the cylindrical rod 10 can be rotated in the circumferential direction while fitted into cylindrical circumferential surface recesses 9a2 and 9b2, and the gears 11a1 and 11b1 can also be rotated. Furthermore, the handles 11a and 11b have their upper portions holding down the cylindrical eccentric cams 7a and 7b to prevent them from shifting out of the holes 2a1 and 2b1 to the outside of the crankcases 2a and 2b (for example, as shown in FIG. 2).

[0020] (Assembly of crankcase 2a and crankcase 2b) Crankcase 2a has screw holes 2a5, 2a6, 2a7, and 2a8. Crankcase 2b has screw holes 2b5, 2b6, 2b7, and 2b8. All of these screw holes are through holes. Screw holes 2a5 and 2b5 are fastened together with a screw (not shown), screw holes 2a6 and 2b6 are fastened together with a screw (not shown), screw holes 2a7 and 2b7 are fastened together with a screw (not shown), and screw holes 2a8 and 2b58 are fastened together with a screw (not shown). This completes the assembly of crankcase 2a and crankcase 2b.

[0021] (Assembly of crankcases 2a, 2b and base 9) The four corners of the top surfaces 9a1 and 9b1 of the raised portions 9a and 9b of the base 9 have through-holes 9a3, 9a3, 9b3, and 9b3. The undersides of the crankcases 2a and 2b (not shown in FIG. 1) have threaded holes aligned with the threaded holes 9a3, 9a3, 9b3, and 9b3, allowing these threaded holes to be screwed together. When screwed together, the gears 11a1 and 11b1 of the handles 11a and 11b can mesh with the gear portions 7c1 and 7d1 of the cylindrical eccentric cams 7a and 7b, respectively.

[0022] (Operation of crank device 1) When the gears 11a1 and 11b1 of the handles 11a and 11b apply a rotational force to the cylindrical eccentric cams 7a and 7b, the second rotation shaft 6b and the first rotation shaft 6a are inserted into the through holes 7g and 7h of the cylindrical eccentric cams 7a and 7b, respectively, and therefore the revolution force is transmitted to the first rotation shaft 6a and the second rotation shaft 6b.

[0023] The revolution force acting on the first and second rotation shafts 6a and 6b rotates and revolves the planetary gears 3a1 and 3a2 while meshing them with the internal sun gears 2a2 and 2b2. This force also revolves the third rotation shaft 6c. This revolution force allows the piston 4 to slide circumferentially around the third rotation shaft 6c, enabling the piston 4 to reciprocate in a substantially straight line.

[0024] The movement of this crank device 1 will be explained using Figures 4 to 11, particularly Figures 5, 7, 9, and 11. First, as shown in Figure 5, the planetary gear portion 3a2 hidden behind the second handle 6e is engaged with the internal sun gear 2a2, and the planetary gear portion 3a2 rotates and revolves 90° in the direction of the arrow. This brings the crank device 1 to the state shown in Figure 7. Then, with the planetary gear portion 3a2 further engaged with the internal sun gear 2a2, the planetary gear portion 3a2 rotates and revolves 90° in the direction of the arrow. This brings the crank device 1 to the state shown in Figure 9. Then, with the planetary gear portion 3a2 further engaged with the internal sun gear 2a2, the planetary gear portion 3a2 rotates and revolves 90° in the direction of the arrow. This brings the crank device 1 to the state shown in Figure 11. Then, with planetary gear portion 3a2 meshing with internal sun gear 2a2, planetary gear portion 3a2 rotates and revolves 90° in the direction of the arrow, returning crank device 1 to the state shown in Figure 5. By repeating these movements, crank device 1 can be operated to enable piston 4 to reciprocate approximately up and down, as shown in Figures 4 to 11.

[0025] Eccentric cam 7a has a gearless portion 7c2 on its outer peripheral surface 7c, and eccentric cam 7b has a gearless portion 7d2 on its outer peripheral surface 7d. Furthermore, on the inner peripheral surfaces of hole 2a1 in crankcase 2a and hole 2b1 in crankcase 2b, there are gearless portions 2a3 and 2b3 adjacent to a pair of opposing inner peripheral sun gears 2a2 and 2b2. These gearless portions 7c2 and 7d2 and the gearless portions 2a3 and 2b3 face each other, with bearings 12a and 12b disposed between them. These bearings 12a and 12b are fixed to the gearless portions 2a3 and 2b3. The individual balls that make up these bearings 12a and 12b rotate and function as rolling bearings.

[0026] (Major Effects Obtained by This Embodiment) As described above, the crank device 1 of this embodiment allows the piston 4 to reciprocate almost completely linearly, thereby reducing vibration and further improving quietness of the crank device 1. Furthermore, the crank device 1 can withstand the explosive force of a large-displacement engine, and in addition, reduces vibration and noise and avoids a decrease in efficiency due to vector decomposition.

[0027] Furthermore, by using eccentric cams 7a and 7b instead of the conventional second crank 111 shown in Fig. 21, it is possible to provide a crank device 1 that can withstand the explosive force of an engine. This is because the shape of the eccentric cams 7a and 7b is simpler than that of a crank and can withstand more stress. This is clear when comparing the cross-sectional view of Fig. 21 with the cross-sectional view of Fig. 3.

[0028] (Other forms) The crank device 1 according to the present embodiment described above is one example of a preferred form of the present invention, but is not limited to this and various modifications are possible within the scope that does not change the gist of the present invention.

[0029] For example, the crank device 1 of this embodiment has a bilaterally symmetrical (double-supported) structure, but it may also have a cantilever structure with one end fixed and the other end free. For example, this is the crank device shown in the cross-sectional view of the crank device 1 taken along line BB in FIG. 4.

[0030] This cantilever-structured crank device comprises an inner sun gear arranged on the inner surface of a hole drilled in the crankcase, planetary gears that rotate and revolve while meshing with the inner sun gear, a crank member that supports the planetary gears so that they can rotate and revolve, and a piston that moves back and forth in a straight line by rotating and revolving the planetary gears while meshing with the inner sun gear, the crank member having fourth and fifth rotating shafts and a third handle connecting the fourth and fifth rotating shafts, the piston being slidable circumferentially about the fifth rotating shaft, the planetary gears being arranged on the circumferential surface of the fourth rotating shaft, the outer surface of the eccentric cam facing the inner surface of the hole in the crankcase, an engaging portion being provided at a position close to the outer surface of the eccentric cam's flat surface, and the engaging portion engaging with another engaging portion provided on the fourth rotating shaft.

[0031] An exploded perspective view of the crank device 20 with this cantilever structure is shown in Fig. 12, and its structure will be described. The same reference numerals as in Fig. 1 are used to designate the same members, and their description will be omitted.

[0032] In the crank device 20, the third rotating shaft 6c of the crank member 5 of the crank device 1 is cut approximately in the middle in the longitudinal direction, and the first rotating shaft 6a, the first handle 6d, and approximately half of the third rotating shaft 6c on these sides are removed to form a fifth rotating shaft 6m. Here, the member corresponding to the second rotating shaft 6b of the crank device 1 is referred to as the fourth rotating shaft 6h in the crank device 20, and its circumferential surface is referred to as the circumferential surface 6k. Furthermore, the member corresponding to the third rotating shaft 6c of the crank device 1 is referred to as the fifth rotating shaft 6m in the crank device 20. Furthermore, the member corresponding to the second handle 6e of the crank device 1 is referred to as the third handle 6n in the crank device 20.

[0033] Furthermore, the crank device 20 does not have the bearing 12b and the eccentric cam 7b of the crank device 1. A left side view of the crank device 20 is shown in Fig. 13, a cross-sectional view taken along line CC of Fig. 13 is shown in Fig. 14, a front view is shown in Fig. 15, and a right side view is shown in Fig. 16.

[0034] Furthermore, the role of the drive device 8 may be played by something other than the drive device 8. For example, the explosive force of fuel such as gasoline or diesel in an internal combustion engine may be converted into driving force.

[0035] Furthermore, the second rotating shaft 6b and the first rotating shaft 6a (another engaging portion) are inserted into and engaged with through holes 7g and 7h (engaging portions) of the cylindrical eccentric cams 7a and 7b, respectively. However, the through holes 7g and 7h may be, for example, protrusions, and the second rotating shaft 6b and the first rotating shaft 6a may have insertion portions that are inserted into the protrusions. In short, it is sufficient that the positions of the through holes 7g and 7h and the positions of the first rotating shaft 6a and the second rotating shaft 6b are engaged with each other.

[0036] Furthermore, bearings 12a and 12b are not essential components and can be omitted. It is certainly considered desirable to have bearings 12a and 12b in order to reduce vibration and noise in the crank device 1. However, this has the disadvantage of increasing the number of parts in the crank device 1. Even if bearings are used, it goes without saying that bearings other than bearings 12a and 12b can be used. Furthermore, bearings 12a and 12b are rolling bearings (ball bearings), but they may also be roller bearings or plain bearings.

[0037] In addition, in this embodiment, the crankcase is manufactured by assembling the crankcase 2a and the crankcase 2b, but it goes without saying that the crankcase may be manufactured by integral molding or the like.

[0038] Furthermore, if there is a member that can replace the eccentric cams 7a and 7b, the eccentric cams 7a and 7b are not necessary. In other words, any member that has a simpler shape than a crank and can withstand stress can be used in place of the eccentric cams 7a and 7b. For example, members that can replace the eccentric cams 7a and 7b include plate-shaped members, cylindrical members, flat cylindrical members like the eccentric cams 7a and 7b, flat plate-shaped members, and even non-flat cylindrical or plate-shaped members. [Explanation of symbols]

[0039] 1 Crank device 2a crankcase 2b crankcase 2a1 hole 2b1 hole 2a2 Internal sun gear 2b2 Internal sun gear 3 Planetary gears 4 pistons 5 Crank parts 6a First rotating shaft (another engaging part) 6b Second rotating shaft (another engaging part) 6c Third rotation axis 6d First pattern 6e Second Handle 7a Eccentric cam (plate-shaped member) 7b Eccentric cam (plate-shaped member) 7c Outer surface 7d Outer surface 7e Flat part 7f flat part 7g Through hole (engaging part) 7h Through hole (engaging part)

Claims

[Claim 1] a pair of opposing inner sun gears disposed on the inner circumferential surface of a hole drilled in the crankcase; a planetary gear that rotates and revolves while meshing with the internal sun gear; a crank member that supports the planetary gear so that it can rotate and revolve; a piston that moves linearly back and forth by rotating and revolving the planetary gears while meshing with the internal sun gear; Equipped with the crank member has a first rotation shaft and a second rotation shaft that share a common rotation axis at both ends, a third rotation shaft between the first rotation shaft and the second rotation shaft and having a rotation axis different from that of the first rotation shaft and the second rotation shaft, a first handle connecting the first rotation shaft and the third rotation shaft, and a second handle connecting the second rotation shaft and the third rotation shaft, the piston is slidable in a circumferential direction of the third rotation shaft, the planetary gears are disposed on the circumferential surfaces of the first rotation shaft and the second rotation shaft, an outer peripheral surface of the plate-shaped member facing an inner peripheral surface of the hole in the crankcase; an engaging portion is provided at a position close to an outer peripheral surface of the flat portion of the plate-like member; The engaging portion engages with another engaging portion provided on the first rotating shaft and the second rotating shaft, respectively. Crank device.

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