Engine

Abstract

To provide an engine which can achieve a torsional vibration suppression function and detect a number of rotation with a simple structure.SOLUTION: An engine E of the disclosure includes: a crankshaft 2 that changes reciprocating motion of a piston 3 into rotational motion; and a vibration reduction device 40 that suppresses torsional vibration of the crankshaft 2. A flange-form flange part 50 is provided at an axial end part of the crankshaft 2. The vibration reduction device 40 has: an annular member 52 that is detachably connected to the flange part 50; and a shaft body 30 which is connected to the annular member via a damper member 54 for absorbing torsional vibration and to which rotation of the crank shaft 2 is transmitted. A plurality of first detected parts 69 for detecting a number of rotation of the crankshaft 2 is formed on an outer peripheral part of the flange part 50 at intervals in a circumferential direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an engine equipped with a vibration reduction device that suppresses torsional vibration of a crankshaft. [Background technology]

[0002] For example, some engines used as a driving source for vehicles have a vibration reduction device such as a crankshaft damper attached to the axial end of the crankshaft (see, for example, Patent Document 1). By providing such a vibration reduction device, torsional vibration of the crankshaft can be suppressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-035328 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, in an engine, a detection part such as a pulse rotor is provided directly or indirectly on the crankshaft to detect the rotation speed of the crankshaft. In addition, if a vibration reduction device and a detection part are provided on the crankshaft, there is a concern that the structure will become complicated.

[0005] The disclosure of the present application provides an engine that can achieve both a torsional vibration suppression function and rotation speed detection with a simple structure. [Means for solving the problem]

[0006] An engine according to one aspect of the present disclosure includes a crankshaft that converts the reciprocating motion of a piston into rotational motion, and a vibration reduction device that suppresses torsional vibration of the crankshaft. The crankshaft has an axial end provided with a flange-shaped portion. The vibration reduction device includes an annular member that is detachably connected to the flange portion, and a shaft that is connected to the annular member via a damper member that absorbs torsional vibration and to which rotation of the crankshaft is transmitted. A plurality of detectable portions that detect the rotation speed of the crankshaft are formed circumferentially spaced apart on the outer periphery of the flange portion or the annular member. [Effects of the Invention]

[0007] According to the engine of the present disclosure, a vibration reduction device that suppresses torsional vibration of the crankshaft is detachably connected to a flange-shaped portion provided at the axial end of the crankshaft. A detectable portion that detects the rotation speed of the crankshaft is formed on the flange portion of the crankshaft or on the outer periphery of the annular member of the vibration reduction device. By providing the detectable portion that detects the rotation speed using the structure that connects the vibration reduction device to the crankshaft or a part of the vibration reduction device, it is possible to omit providing a separate structure for detecting the rotation speed. As a result, both the torsional vibration suppression function and the rotation speed detection can be achieved with a simple structure. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view showing an engine according to a first embodiment of the present disclosure. [Figure 2] FIG. [Figure 3] FIG. 2 is a cross-sectional view showing a reduction mechanism of the engine. [Figure 4] FIG. 2 is a cross-sectional view showing a vibration reduction device for the engine. DETAILED DESCRIPTION OF THE INVENTION

[0009] A preferred embodiment of the present disclosure will be described below with reference to Figures 1 to 4. The engine E of this embodiment is a reciprocating engine, and is used, for example, in an airplane in which a propeller is disposed at the tip of the fuselage. In this case, the engine E is housed within the fuselage, and engine power is transmitted to the propeller. The use of the engine E is not limited to this, and it can also be used, for example, as a drive source for a ship. It can also be used as a drive source for vehicles such as two-wheeled vehicles and four-wheeled vehicles.

[0010] In the following description, the "width direction WD" refers to the direction in which the crankshaft 2 of the engine E extends. In other words, the "axial direction of the crankshaft" coincides with the width direction WD. In the width direction WD, the direction toward the width center is referred to as the "width inner side," and the direction away from the width center is referred to as the "width outer side." The "reciprocating direction VD" refers to the direction in which the pistons of the engine E reciprocate. The direction perpendicular to both the "width direction WD" and the "reciprocating direction VD" is referred to as the "perpendicular direction PD."

[0011] The engine E of this embodiment is a six-cylinder engine with six cylinders aligned in the direction in which the crankshaft 2 extends. However, the number of cylinders is not limited to this and may be, for example, four. Furthermore, although the engine E of this embodiment is a gasoline engine, the fuel is not limited to gasoline. The crankshaft 2 converts the reciprocating motion of the pistons 3 into rotational motion.

[0012] The engine E has a crankcase 4 that supports the crankshaft 2, a cylinder 6 that protrudes upward from the crankcase 4, and a cylinder head 8 that is connected to the upper end of the cylinder 6. In the following description, in the reciprocating direction VD of the piston 2, the direction in which the cylinder 6 protrudes from the crankcase 4 is referred to as "upper," and the opposite side is referred to as "lower."

[0013] The crankcase 4 is divided into two parts, a lower crankcase 4a and an upper crankcase 4b. In this embodiment, the upper crankcase 4b and the cylinder 6 are formed as an inseparable unit. However, the upper crankcase 4b and the cylinder 6 may be separate bodies. In the following description, the unit consisting of the upper crankcase 4b and the cylinder 6 is referred to as a cylinder block 10.

[0014] The engine E further has a head cover 12 connected to the upper end of the cylinder head 8, and an oil pan 14 connected to the lower end of the crankcase 4. The oil pan 14 stores oil, which is a type of engine lubricating fluid.

[0015] An intake port 16 opens to one end surface of the cylinder head 8 in the orthogonal direction PD (the right side in FIG. 1), and an exhaust port 18 opens to the other end surface of the cylinder head 8 in the orthogonal direction PD (the left side in FIG. 1). In the following description, the side in the orthogonal direction PD where the intake port 16 opens is referred to as the "intake side," and the side in the orthogonal direction PD where the exhaust port 18 opens is referred to as the "exhaust side."

[0016] The intake port 16 and the exhaust port 18 are passages formed inside the cylinder head 8. The upstream end of the intake port 16 opens to one end side of the cylinder head 8 in the orthogonal direction PD, and the downstream end opens to a combustion chamber 20 inside the cylinder 6. The upstream end of the exhaust port 18 opens to the combustion chamber 20 inside the cylinder 6, and the downstream end opens to the other end side of the cylinder head 8 in the orthogonal direction PD. An intake port 16 is formed for each cylinder. Similarly, an exhaust port 18 is also formed for each cylinder.

[0017] External air is supplied as intake air from the intake port 16 to the combustion chamber 20, and fuel is injected into the combustion chamber 20 from the injector 22 to form a mixture of fuel and air. The mixture in the combustion chamber 20 is ignited by the spark plug 24 and burns. Exhaust gas after combustion is discharged to the outside of the engine from the exhaust port 18.

[0018] FIG. 2 is a front view of the engine E of this embodiment, as viewed from the exhaust side. As shown in the figure, the engine E of the present disclosure includes a speed reduction mechanism 26 that reduces the rotation speed of the crankshaft 2. The speed reduction mechanism 26 is provided at one end (left side in FIG. 2) of the engine E in the width direction WD. The engine E of this embodiment also includes a generator GE that generates electricity by the rotation of the crankshaft 2. The generator GE is provided at the other end (right side in FIG. 2) of the engine E in the width direction WD. In the following description, the side in the width direction WD where the speed reduction mechanism 26 is provided will be referred to as the speed reduction mechanism side, and the side where the generator GE is provided will be referred to as the generator side.

[0019] The reduction gear mechanism 26 is covered by a gear cover 28. More specifically, the gear cover 28 covers the reduction gear mechanism 26 from the outside in the axial direction and from the radial direction. The gear cover 28 is detachably attached to the cylinder block 10 by fastening members 29 such as bolts.

[0020] The reduction gear mechanism 26 has an input shaft 30 connected to the crankshaft 2 and an output shaft 32 connected to the input shaft 30 by gears. A small-diameter input gear 34 is provided on the input shaft 30, and a large-diameter output gear 36 is provided on the output shaft 32, with the input gear 34 and the output gear 36 meshing together. In other words, the rotational force of the crankshaft 2 is transmitted to the input shaft 30, reduced by the gear connection between the gears 34, 36, and then transmitted to the output shaft 32. This allows the gear ratio to be changed to suit the output.

[0021] In this embodiment, the input gear 34 and the output gear 36 are "helical gears." Using helical gears is advantageous in terms of strength and noise reduction. However, the input and output gears 34, 36 of the reduction mechanism 26 are not limited to "helical gears."

[0022] In this embodiment, an aircraft propeller Pr is coupled to the output shaft 32. The propeller Pr may be directly connected to the output shaft 32, or may be coupled to the output shaft 32 via a power transmission member. In addition to the aircraft propeller Pr, for example, a vehicle wheel, a turbine or compressor rotor blade, a pump impeller, etc. may also be coupled to the output shaft 32.

[0023] The engine E of this embodiment is disposed within the fuselage of a propeller-driven aircraft, with the aircraft's propeller Pr connected to the output shaft 32. In this case, the propeller shaft and crankshaft 2 may be disposed along the fuselage centerline extending in the longitudinal direction of the fuselage of the propeller-driven aircraft. Furthermore, with the aircraft's wings positioned horizontally, the engine E of this embodiment may be in an upright position, i.e., the piston reciprocation direction VD may coincide with the vertical direction. This allows the engine E to be housed compactly within the fuselage.

[0024] 3, an axially inner end 30a of an input shaft 30 of the reduction gear mechanism 26 is rotatably supported on an axially outer end 2a of the crankshaft 2, and an axially outer end 30b of the input shaft 30 is rotatably supported on a gear cover 28. In this embodiment, the axially inner end 30a of the input shaft 30 is supported on the crankshaft 2 via a needle roller bearing 42, and the axially outer end 30b of the input shaft 30 is supported on the gear cover 28 via a ball bearing 44. However, the bearings 42, 44 are not limited to needle roller bearings or ball bearings.

[0025] An axially inner end 32a of the output shaft 32 of the reduction gear mechanism 26 is supported by the cylinder block 10 via a rolling bearing 46, and an axially outer end 32b of the output shaft 32 is supported by the gear cover 28 via a rolling bearing 48. In this embodiment, tapered roller bearings are used as the rolling bearings 46, 48. However, the rolling bearings 46, 48 are not limited to tapered roller bearings.

[0026] In the engine E of this embodiment, power is transmitted from the crankshaft 2 to the input shaft 30 of the reduction mechanism 26 via the vibration reduction device 40. In other words, power is transmitted from the crankshaft 2 to the input shaft 30 of the reduction mechanism 26 via a damper structure serving as the vibration reduction device 40, and the input shaft 30 is supported at one end 2a of the crankshaft 2 in the axial direction so as to be rotatable relative to the crankshaft 2.

[0027] The vibration reduction device 40 suppresses torsional vibration of the crankshaft 2. In this embodiment, the vibration reduction device 40 is a vibration reduction device 40 that suppresses torsional vibration of the crankshaft 2. More specifically, the vibration reduction device 40 of this embodiment is an engine torque damper, specifically a spring damper, that reduces engine vibration that occurs during deceleration and acceleration.

[0028] The vibration reduction device 40 is disposed coaxially on one end 2a of the crankshaft 2, and the input shaft 30 of the speed reduction mechanism 26 is connected to one end 2a of the crankshaft 2 via the vibration reduction device 40. More specifically, a flange 2b extending radially is formed on the axially outer end 2a of the crankshaft 2. A plurality of threaded holes 2ba are formed in the flange 2b and spaced at equal intervals in the circumferential direction.

[0029] A vibration reduction device 40 is attached to the axially inner end 30a of the input shaft 30 of the reduction mechanism 26 so as to be non-rotatable relative to the input shaft 30. The vibration reduction device 40 is connected to the flange 2b on the axially outer end 2a of the crankshaft 2 via a bracket 50. As a result, the rotation of the crankshaft 2 is transmitted to the input shaft 30 of the reduction mechanism 26 via the vibration reduction device 40, and the torque generated in the crankshaft 2 is absorbed by the vibration reduction device 40.

[0030] The bracket 50 of this embodiment is an annular member made of sheet metal. The bracket 50 is detachably attached at its radially inner portion to the flange 2b of the axially outer end 2a of the crankshaft 2 using fastening members 55 such as bolts. The radially outer portion of the bracket 50 extends radially outward in a flange-like shape, extending radially outward beyond the flange 2b of the crankshaft 2. In other words, the bracket 50 constitutes a flange-shaped flange portion provided at the axial end 2a of the crankshaft 2.

[0031] In this embodiment, the axially outer end portion 2a of the crankshaft 2 is fitted into a through-hole 50b in the center of the annular bracket 50. This positions the radial centers of the bracket 50 and the crankshaft 2.

[0032] An engagement hole 2bb is formed in the flange portion 2b of the crankshaft 2, and a knock pin 53 is press-fitted into the engagement hole 2bb. The axially outer end of this knock pin 53 is fitted into an engagement hole 50c formed in the bracket 50. This determines the circumferential positions of the bracket 50 and the crankshaft 2, i.e., their relative angles. In other words, the phase difference between the bracket 50 and the crankshaft 2 can be matched.

[0033] In this embodiment, the bracket 50 is formed by drawing a metal sheet. Therefore, it can be formed more inexpensively than by machining or casting. When the bracket 50 is formed by drawing, it is more difficult to provide a retaining structure than when it is formed by machining or casting. However, in this embodiment, the knock pin 53 is press-fit into the engagement hole 50c of the bracket 50, which prevents the bracket 50 from coming off the crankshaft 2.

[0034] A plurality of mounting holes 50a are formed circumferentially spaced apart in a radially outer portion of the bracket 50. In this embodiment, round press-fit nuts 51 are press-fitted into the mounting holes 50a to form threaded holes. However, the threaded holes are not limited to the press-fit nuts 51 and may be, for example, weld nuts.

[0035] The vibration reduction device 40 has an annular member 52 that is detachably connected to a bracket 50 that is a flange portion, a damper member 54 that absorbs torsional vibrations, and a shaft 30 that is connected to the annular member 52 via the damper member 54. In this embodiment, a spring is used as the damper member 54. The rotation of the crankshaft 2 is transmitted to the annular member 52 of the vibration reduction device 40 via the bracket 50, and after the torsional vibrations are absorbed by the damper member 54, the rotation is transmitted to the shaft 30. In this embodiment, the input shaft 30 of the speed reduction mechanism 26 forms the shaft 30 of the vibration reduction device 40.

[0036] The annular member 52 has a first annular body 56 connected to the bracket 50 and a second annular body 58 connected to the first annular body 56. The bracket 50 and the first annular body 56 are detachably connected via a cylindrical collar 60 by a fastening member 62 such as a bolt. If a bolt with a small head is used as the fastening member 62, it is possible to prevent the head from protruding outward in the axial direction.

[0037] In detail, the radial outer edge of the first annular body 56 faces the outer edge of the bracket 50 in the axial direction (width direction WD), and a bolt insertion hole 56a is formed in the outer edge at a position corresponding to the mounting hole 50a of the bracket 50.

[0038] With the collar 60 interposed between the inner surface of the first annular body 56 and the outer surface of the bracket 50, the fastening members 62 are inserted from the outside through the bolt insertion holes 56a of the first annular body 56 and the hollow holes in the collar 60, in that order, and tightened to the press-fit nuts 51 of the bracket 50. In this way, the bracket 50 and the first annular body 56 are connected via the collar 60. As shown in FIG. 4 , in this embodiment, the bracket 50 and the first annular body 56 are fastened together using eight fastening members 62 spaced apart in the circumferential direction, but the number of fastening members 62 is not limited to this.

[0039] When applying the vibration reduction device 40 of this embodiment to an engine having a different engine rotation direction from that of this embodiment, the collar 60 can be omitted and the surface opposite to that of this embodiment, i.e., the outer surface of the first annular body 56 in FIG. 3, can be attached to the bracket 50. In this way, by using the collar 60, a common vibration reduction device 40 can be applied to two types of engines having different engine rotation directions. When connecting via the collar 60 as in this embodiment, the number of parts increases, but the longer fastening member 60 is advantageous in preventing loosening of the fastening member 60.

[0040] The second annular body 58 has an outer annular member 58o on the outside in the width direction and an inner annular member 58i on the inside in the width direction, and these outer and inner annular members 58o, 58i are connected by fastening members 64 such as bolts. As shown in Fig. 4, in this embodiment, the second annular body 58 is fastened by four fastening members 64 spaced apart in the circumferential direction, but the number of fastening members 64 is not limited to this.

[0041] The first annular body 56 and the outer annular member 58 of the second annular body 58 are connected by fastening members 65 such as bolts. Specifically, with the inner surface of the first annular body 56 and the outer surface of the outer annular member 58o of the second annular body 58 abutting against each other, the fastening members 65 are inserted from the outside into the insertion holes 56b (FIG. 4) of the first annular body 56 and tightened into the threaded holes 58oa of the outer annular member 58o. The threaded holes 58oa are, for example, weld nuts. This connects the inner surface of the first annular body 56 and the outer annular member 58o of the second annular body 58. As shown in FIG. 4, in this embodiment, the first annular body 56 and the outer annular member 58o are fastened together using 16 fastening members 65 spaced apart in the circumferential direction, but the number of fastening members 65 is not limited to this.

[0042] The damper members 54 are interposed between the outer annular member 58o and the inner annular member 58i of the second annular body 58. More specifically, pockets 66 that open in the width direction WD are formed in the second annular body 58, and the damper members 54 are housed in these pockets 66. In this embodiment, four damper members 54 are provided spaced apart in the circumferential direction.

[0043] 3, a rotor 68 is mounted on the input shaft 30 of the speed reduction mechanism, which is the shaft 30 of the vibration reduction device 40, so as to be non-rotatable relative to the shaft 30, and a damper member 54 is connected to the rotor 68. The damper member 54 is biased in the circumferential direction, and the rotation of the annular member 52 acts on the damper member 54 against the biasing force, thereby rotating the rotor 68. In other words, the rotation of the annular member 52 is transmitted to the shaft 30 via the damper member 54 and the rotor 68.

[0044] When the engine E shown in Fig. 2 starts, the crankshaft 2 rotates. The rotation of the crankshaft 2 is transmitted to the vibration reduction device 40 via a flange portion 50 made of a bracket shown in Fig. 3. Specifically, the rotation of the crankshaft 2 is transmitted to a first annular body 56 of the vibration reduction device 40, which is connected to the bracket 50, via a collar 60, and is further transmitted to a second annular body 58 connected to the first annular body 56.

[0045] The rotation of the second annular body 58 acts on the damper member 54, compressing it, thereby suppressing torsional vibration of the crankshaft 2. When the compression limit of the damper member 54 is exceeded, the rotation of the second annular body 58 is transmitted to the shaft 30 of the vibration reduction device 40 (the input shaft 30 of the speed reduction mechanism 26) via the rotor 68.

[0046] In the rotation transmission path from the crankshaft 2 to the shaft 30 of the vibration reduction device 40, i.e., the input shaft 30 of the speed reduction mechanism 26, the members upstream of the damper member 54, i.e., the flange portion 50 made of a bracket, the first annular body 56, and the second annular body 58, rotate at the same rotation speed as the crankshaft 2. On the other hand, the members downstream of the damper member 54, i.e., the rotor 68 and the shaft 30, rotate at a different rotation speed from the crankshaft 2.

[0047] 4, a first detectable portion 69 that rotates integrally with the crankshaft 2 is formed on the outer peripheral surface of the bracket (flange portion) 50. In this embodiment, the first detectable portion 69 is an uneven portion formed on the outer peripheral surface of the flange portion 50, with multiple uneven portions formed spaced apart in the circumferential direction. In other words, the first detectable portion 69 constitutes a pulse rotor for detecting the rotation speed of the crankshaft 2.

[0048] In this embodiment, the first detectable portion 69 is formed on the flange portion 50 made of a bracket, but may also be provided on the annular member 52 of the vibration reduction device 40. Also, in this embodiment, the first detectable portion 69 is formed on the outer peripheral surface of the flange portion 50, but may also be provided on an end surface facing the width direction WD, which is the axial direction of the flange portion 50 or the annular member 52.

[0049] The engine E further includes a first rotation detection device 70 that detects the rotation speed of the crankshaft 2 from the first detectable part 69. The first rotation detection device 70 is fixed to the crankcase 4 by a fastening member 72 such as a bolt. In this embodiment, a pickup coil is used as the first rotation detection device 70. The first rotation detection device 70 detects irregularities in the rotating first detectable part 69 (pulsar rotor). The first rotation detection device 70 is connected to, for example, an electronic control unit (ECU), and calculates the rotation speed of the crankshaft 2 from the detected irregularities.

[0050] The first rotation detection device 70 is disposed on the intake side in the orthogonal direction PD. The first rotation detection device 70 is disposed closer to the cylinder 6 than the crankshaft 2 in the reciprocating direction VD, i.e., above the crankshaft 2. Furthermore, at least a portion of the first rotation detection device 70 is located inside the outer edge of the vibration reduction device 40 in the reciprocating direction VD and the orthogonal direction PD. The first rotation detection device 70 is disposed between the output shaft 32 of the reduction mechanism 26 and the crankshaft 2 when viewed from the axial direction of the crankshaft 2.

[0051] In this way, the first rotation detection device 70 is disposed above the crankshaft 2 on the intake side in the orthogonal direction PD, and is disposed so as not to protrude as much as possible in the reciprocating direction VD and the orthogonal direction PD. This avoids heat damage to the first rotation detection device 70 and achieves a compact external size.

[0052] As shown in FIG. 2, a first detectable part 69 and a first rotation detection device 70 are arranged on the reduction mechanism side in the engine width direction WD, which is the axial direction of the crankshaft 2, and a second rotation detection device 74, which is an additional rotation detection device, and a second detectable part 76, which is an additional detectable part, are provided on the generator side.

[0053] The second detected part 76 is a pulse rotor provided on the rotor of the generator GE. More specifically, the second detected part 76 is an irregularity provided on the outer periphery of the rotor of the generator GE. In other words, the second detected part 76 rotates at the same rotation speed as the crankshaft 2.

[0054] The second rotation detection device 74 detects the rotation speed of the crankshaft 2. In this embodiment, the second rotation detection device 74 is a pickup coil. That is, the second rotation detection device 74 detects irregularities in the rotating second detection target 76. The second detection target 76 is connected to, for example, an electronic control unit (ECU), which calculates the rotation speed of the crankshaft 2 from the detected irregularities. By providing two rotation detection devices 70, 74, that is, by duplicating the rotation detection devices 70, 74, the reliability of the detected rotation speed of the crankshaft 2 is improved.

[0055] According to the above configuration, as shown in Fig. 3, the vibration reduction device 40 that suppresses torsional vibration of the crankshaft 2 is detachably connected to a flange-shaped flange portion 50 provided at the axial end of the crankshaft 2. Furthermore, a first detectable portion 69 used to detect the rotation speed of the crankshaft 2 is formed on the outer peripheral surface of the flange portion 50 of the crankshaft 2. In this way, by using the bracket 50 that connects the vibration reduction device 40 to the crankshaft 2 to provide the first detectable portion 69 for rotation speed detection, it is possible to omit providing a separate structure for rotation speed detection. As a result, both the torsional vibration suppression function and the rotation speed detection can be achieved with a simple structure.

[0056] The engine E of this embodiment is a six-cylinder engine, and therefore has a long crankshaft 2. This makes it easy for torsion to occur in the crankshaft 2. In the above configuration, the vibration reduction device 40 is connected to the crankshaft 2, or a part of the vibration reduction device 40 is used to provide a pulsar rotor function. This makes it possible to both suppress torsional vibration in the crankshaft 2 and detect the rotation speed of the crankshaft 2 with a simple structure.

[0057] 4, in this embodiment, a first rotation detection device 70 that detects the rotation speed of the crankshaft 2 from a first detectable part 69 is disposed on the intake side in the orthogonal direction PD. With this configuration, the first rotation detection device 70 is disposed away from the exhaust side, which is prone to high temperatures, and therefore heat damage to the first rotation detection device 70 can be prevented.

[0058] In this embodiment, the first rotation detection device 70 is disposed closer to the cylinder 6 than the crankshaft 2 in the reciprocating direction VD, and at least a portion of the first rotation detection device 70 is located inside the outer edge of the vibration reduction device 40 in both the reciprocating direction VD and the orthogonal direction PD. With this configuration, the first rotation detection device 70 is disposed radially inside the outer edge of the vibration reduction device 40 when viewed in the axial direction of the crankshaft 2, allowing the first rotation detection device 70 to be disposed compactly.

[0059] In this embodiment, the first rotation detection device 70 is fixed to the crankcase 4. By being fixed to the robust crankcase 4 in this manner, the first rotation detection device 70 is stably supported.

[0060] In this embodiment, the first rotation detection device 70 is disposed between the output shaft 32 of the reduction mechanism 26 and the crankshaft 2, as viewed from the axial direction of the crankshaft 2. According to this configuration, the first rotation detection device 70 is disposed between the input shaft 30 and the output shaft 32 of the reduction mechanism 26, as viewed from the axial direction of the crankshaft 2, so that the first rotation detection device 70 can be disposed compactly.

[0061] In this embodiment, a first detectable portion 69 is formed on the outer peripheral surface of a bracket 50 that supports the vibration reduction device 40 on the crankshaft 2. With this configuration, since the first detectable portion 69 is formed on the bracket 50, it is not necessary to process the vibration reduction device 40 or the crankshaft 2 to provide a detectable portion.

[0062] In this embodiment, as shown in Fig. 3, the bracket 50 and the annular member 52 are connected via a cylindrical collar 60. With this configuration, one type of vibration reduction device 40 can be used for two types of engines with different rotation directions. Although the collar 60 is required to connect them in the opposite directions, the length of the fastening member 62 is advantageous in preventing loosening.

[0063] 2, in this embodiment, in addition to the first rotation detection device 70, a second rotation detection device 74 is provided to detect the rotation speed of the crankshaft 2. This configuration achieves redundancy of the rotation detection device, improving reliability.

[0064] The engine of the present disclosure includes the following aspects 1 to 8. [Aspect 1] A crankshaft converts the reciprocating motion of the pistons into rotational motion, a vibration reduction device that suppresses torsional vibration of the crankshaft, a flange-shaped portion is provided at an axial end of the crankshaft, The vibration reduction device is an annular member detachably connected to the flange portion; a shaft connected to the annular member via a damper member that absorbs torsional vibrations, and to which rotation of the crankshaft is transmitted, an engine in which a plurality of detectable portions for detecting the rotation speed of the crankshaft are formed circumferentially spaced apart on the outer periphery of the flange portion or the annular member; [Aspect 2] The engine according to aspect 1 further includes a rotation detection device that detects the rotation speed of the crankshaft from the detection target portion, an engine in which the rotation detection device is disposed on the intake side where an intake port is formed, in a direction perpendicular to both the axial direction of the crankshaft and the reciprocating direction of the piston; [Aspect 3] In the engine according to aspect 2, the rotation detection device is disposed closer to the cylinder than the crankshaft in the reciprocating direction, An engine in which at least a portion of the rotation detection device is located inside an outer edge of the vibration reduction device in the reciprocating direction and the perpendicular direction. [Aspect 4] 4. The engine according to claim 2, wherein the rotation detection device is fixed to a crankcase. [Aspect 5] The engine according to any one of aspects 2 to 4, further comprising a speed reduction mechanism that reduces the rotation speed of the crankshaft, the shaft body constitutes an input shaft of the reduction mechanism, an engine in which the rotation detection device is disposed between the output shaft of the reduction mechanism and the crankshaft when viewed from the axial direction of the crankshaft; [Aspect 6] In the engine according to any one of aspects 1 to 5, the flange portion is formed by a bracket detachably attached to an axial end portion of the crankshaft, An engine in which the detected portion is formed on the outer peripheral surface of the bracket. [Aspect 7] 7. The engine according to claim 6, wherein the bracket and the annular member are connected via a cylindrical collar. [Aspect 8] In the engine according to any one of aspects 1 to 7, the detected part is disposed on one axial end side of the crankshaft, An engine in which an additional rotation detection device for detecting the rotation speed of the crankshaft is provided on the other axial end side of the crankshaft.

[0065] The present disclosure is not limited to the above embodiments, and various additions, modifications, or deletions are possible without departing from the spirit and scope of the present disclosure. For example, the engine E of the above embodiment can also be applied to saddle-type vehicles such as motorcycles, tricycles, and four-wheeled buggies (all-terrain vehicles). The engine E may be used in an outboard motor or as a propulsion source for aircraft. Additionally, the engine E may be used as a propulsion source for four-wheeled vehicles or small personal watercraft. The number of cylinders is not limited to six, and may be less than six, or seven or more. The engine E may be provided with a supercharger such as a turbocharger or a supercharger. Therefore, such configurations are also included within the scope of the present disclosure. [Explanation of symbols]

[0066] 2 crankshaft 3 pistons 4 crankcase 6 cylinders 26 Reduction mechanism 30 Shaft (input shaft of reduction mechanism) 32 Output shaft of reduction mechanism 40 Vibration reduction device 50 Bracket (flange part) 52 Annular member 54 Damper member 60 colors 69 First detected part (pulsa rotor) 70 First rotation detection device 74 Second rotation detection device (additional rotation detection device) E-Engine

Claims

1. A crankshaft converts the reciprocating motion of the pistons into rotational motion, a vibration reduction device that suppresses torsional vibration of the crankshaft, a flange-shaped portion is provided at an axial end of the crankshaft, The vibration reduction device is an annular member detachably connected to the flange portion; a shaft connected to the annular member via a damper member that absorbs torsional vibrations, and to which rotation of the crankshaft is transmitted, an engine in which a plurality of detectable portions for detecting the rotation speed of the crankshaft are formed circumferentially spaced apart on the outer periphery of the flange portion or the annular member;

2. 2. The engine according to claim 1, further comprising a rotation detection device that detects the rotation speed of the crankshaft from the detected part, an engine in which the rotation detection device is disposed on the intake side where an intake port is formed, in a direction perpendicular to both the axial direction of the crankshaft and the reciprocating direction of the piston;

3. 3. The engine according to claim 2, wherein the rotation detection device is disposed closer to the cylinder than the crankshaft in the reciprocating direction. An engine in which at least a portion of the rotation detection device is located inside an outer edge of the vibration reduction device in the reciprocating direction and the perpendicular direction.

4. 4. The engine according to claim 2, wherein the rotation detection device is fixed to a crankcase.

5. The engine according to claim 2 or 3, further comprising a speed reduction mechanism for reducing the rotation speed of the crankshaft, the shaft body constitutes an input shaft of the reduction mechanism, an engine in which the rotation detection device is disposed between the output shaft of the reduction mechanism and the crankshaft when viewed from the axial direction of the crankshaft;

6. 4. The engine according to claim 1, wherein the flange portion is formed by a bracket detachably attached to an axial end portion of the crankshaft, An engine in which the detected portion is formed on the outer peripheral surface of the bracket.

7. 7. The engine according to claim 6, wherein the bracket and the annular member are connected via a cylindrical collar.

8. 4. The engine according to claim 1, wherein the detected part is disposed on one axial end side of the crankshaft, An engine in which an additional rotation detection device for detecting the rotation speed of the crankshaft is provided on the other axial end side of the crankshaft.

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